Microbiology is one of the fundamental sciences underlying modern nursing and clinical medicine. Every nurse encounters microorganisms directly or indirectly through respiratory infection, urinary tract infection, wound infection, diarrhoeal disease, tuberculosis, malaria, sepsis, maternal infection, neonatal infection, healthcare-associated infection and antimicrobial therapy.
This textbook approaches microbiology from the foundations of the science and gradually connects basic concepts to clinical disease. Particular attention is given to conditions encountered in Nigeria and other tropical countries while retaining relevance to nursing and health-science students internationally.
Foundations of Microbiology
This part introduces the science of microbiology before moving into clinical bacteriology, virology, mycology and parasitology.
Introduction to Microbiology
Microbiology is the scientific study of microscopic organisms and infectious agents. These include bacteria, fungi, protozoa, microscopic stages of helminths and viruses.
Microorganisms are found in soil, water, food, air, animals, plants and the human body. Many are harmless, and some are beneficial. Others possess characteristics that enable them to cause human disease.
Clinical Microbiology
Clinical microbiology is concerned with microorganisms associated with human disease and with the laboratory methods used to detect, isolate, identify and characterise them.
It therefore connects the laboratory with direct clinical care.
Colonisation
Colonisation is the presence and multiplication of microorganisms on or within the body without significant tissue injury or clinical disease.
Infection
Infection occurs when microorganisms enter a host, multiply and produce a biological response.
Infectious Disease
Infectious disease occurs when infection results in sufficient tissue damage or physiological disturbance to produce clinical manifestations.
Bacteria
Bacteria are single-celled prokaryotic organisms. They lack a membrane-bound nucleus and reproduce mainly by binary fission.
Viruses
Viruses are acellular infectious agents containing genetic material surrounded by a protein coat. Some possess an additional lipid envelope. They require living host cells for replication.
Fungi
Fungi are eukaryotic organisms and include yeasts, moulds and dimorphic fungi.
Protozoa
Protozoa are single-celled eukaryotic organisms. Important examples include Plasmodium, Entamoeba and Giardia.
Helminths
Helminths are multicellular parasitic worms including nematodes, cestodes and trematodes.
Bacteriology studies bacteria.
Virology studies viruses.
Mycology studies fungi.
Parasitology studies protozoa and helminths.
Immunology studies host defence and immune responses.
Clinical microbiology applies microbiological science to diagnosis and management of human infection.
Public-health microbiology supports disease surveillance, outbreak investigation and infection prevention.
History and Development of Microbiology
The development of microbiology changed medicine by establishing that invisible microorganisms could cause disease. Early microscopy allowed microorganisms to be observed, while controlled experiments eventually disproved the concept of spontaneous generation.
The germ theory of disease established that particular microorganisms may produce particular diseases. The subsequent development of culture techniques, aseptic surgery, vaccination, antimicrobial chemotherapy and molecular diagnostics transformed clinical practice.
Microscopy and Microbial Observation
The compound light microscope uses visible light and several lenses to magnify microorganisms.
Important components include the ocular lens, objective lenses, stage, condenser, light source and focusing mechanisms.
The oil-immersion objective provides high magnification and is used frequently in bacteriology.
Magnification
Magnification enlarges an object.
Resolution
Resolution is the ability to distinguish two closely positioned objects as separate structures.
Electron microscopes use electrons rather than visible light and therefore provide substantially greater resolution.
Transmission Electron Microscopy
TEM is useful for viewing internal ultrastructure.
Scanning Electron Microscopy
SEM provides detailed information about surface architecture.
Electron microscopy is particularly valuable in research and in the visualisation of structures much smaller than ordinary bacteria.
Bacterial Cell Structure
Cytoplasmic Membrane
The bacterial membrane regulates movement of substances into and out of the cell and participates in energy generation.
Cell Wall
The bacterial cell wall maintains shape and protects against osmotic rupture.
Gram-Positive Wall
Gram-positive bacteria possess a relatively thick peptidoglycan layer and appear purple following Gram staining.
Gram-Negative Wall
Gram-negative bacteria possess a thinner peptidoglycan layer and an outer membrane. They generally appear pink or red after Gram staining.
Their outer membrane contains lipopolysaccharide. The lipid A component can stimulate intense systemic inflammation.
Capsule
A capsule may protect a bacterium from phagocytosis and increase virulence.
Flagella
Flagella provide motility in many bacterial species.
Fimbriae
Fimbriae help organisms attach to host surfaces.
Pili
Some pili participate in transfer of DNA from one bacterial cell to another.
Endospores
Certain bacteria form highly resistant endospores capable of surviving harsh environmental conditions.
Microbial Growth, Metabolism and Genetics
Lag Phase
Bacteria adapt to a new environment and prepare for multiplication.
Log Phase
Rapid cell division occurs. Many antibacterial agents act best against actively multiplying organisms.
Stationary Phase
Nutrient depletion and metabolic waste reduce net population growth.
Death Phase
The viable population progressively declines.
Most bacteria possess a circular chromosome and may additionally contain plasmids.
Mutation
Changes in bacterial DNA may create new characteristics.
Transformation
Bacteria may acquire free DNA from their environment.
Transduction
Bacteriophages may transfer genetic material between bacterial cells.
Conjugation
DNA may pass directly between bacteria, often through plasmids. This is important in the spread of antimicrobial resistance.
Microbial Pathogenesis
Virulence
Virulence refers to the degree of pathogenicity of an organism. Different strains of the same microbial species may differ greatly in their ability to cause severe disease.
Adhesins
Adhesins allow microorganisms to attach to host cells and resist mechanical removal.
Capsules
Capsules may reduce effective phagocytosis.
Exotoxins
Exotoxins are secreted microbial proteins capable of altering or damaging host cells.
Endotoxin
Gram-negative lipopolysaccharide can stimulate fever, inflammatory mediator release and circulatory dysfunction in severe infection.
Biofilms
Biofilms are organised microbial communities attached to surfaces and enclosed within an extracellular matrix. They are particularly important on vascular catheters, urinary catheters, prostheses and some chronic wounds.
The Chain of Infection
The chain-of-infection model explains how infectious disease spreads. Interruption of any link can reduce transmission.
Reservoir
Humans, animals, water, soil and contaminated environments can serve as reservoirs.
Portal of Exit
Respiratory secretions, blood, faeces, urine and wound drainage are common portals of exit.
Modes of Transmission
Important routes include direct contact, indirect contact, respiratory droplets, airborne transmission, contaminated food or water, vectors and blood exposure.
Susceptible Host
Host susceptibility is influenced by age, immunity, nutritional status, vaccination, chronic disease and disruption of normal anatomical barriers.
Normal Microbiota and Opportunistic Infection
The human body supports large microbial communities, particularly on the skin, oral cavity, colon and genital tract.
Normal microbiota can prevent colonisation by pathogens by competing for nutrients and attachment sites.
However, normal organisms can become opportunistic pathogens when they enter normally sterile tissues or when host immunity is impaired.
Sterilisation, Disinfection and Infection Control
Sterilisation
Sterilisation destroys all forms of microbial life, including bacterial spores.
Disinfection
Disinfection reduces or eliminates many pathogenic microorganisms on inanimate objects but may not reliably destroy all spores.
Antisepsis
Antisepsis uses antimicrobial substances on living tissue to reduce microbial numbers.
Autoclaving
Steam under pressure is a highly effective sterilisation method for appropriate heat-resistant equipment.
Hand Hygiene
Hand hygiene remains one of the most important measures for preventing healthcare-associated transmission.
Antimicrobial Agents and Resistance
Beta-Lactams
Penicillins, cephalosporins, carbapenems and monobactams interfere with bacterial cell-wall synthesis.
Macrolides
Agents such as azithromycin and clarithromycin inhibit bacterial protein synthesis.
Tetracyclines
Doxycycline and related drugs inhibit protein synthesis and have important roles in selected respiratory, zoonotic and vector-borne infections.
Aminoglycosides
These inhibit protein synthesis and are used particularly against selected aerobic Gram-negative infections and in certain combination regimens.
Fluoroquinolones
These interfere with enzymes involved in bacterial DNA replication. Resistance and adverse-effect concerns require judicious use.
Glycopeptides
Vancomycin is important for serious infections caused by susceptible Gram-positive organisms, including selected MRSA infections.
Resistance may be intrinsic or acquired.
Important mechanisms include drug-inactivating enzymes, alteration of the antimicrobial target, reduced drug entry, active efflux and metabolic bypass.
Beta-Lactamases
These enzymes destroy selected beta-lactam antibiotics. Extended-spectrum beta-lactamases are especially important among Enterobacterales.
MRSA
Methicillin-resistant Staphylococcus aureus contains altered penicillin-binding proteins that reduce susceptibility to many beta-lactam agents.
Diagnostic Clinical Microbiology
Clinical Specimen Collection and Laboratory Diagnosis
General Principles
The diagnostic value of microbiology begins with the specimen. Incorrect specimen collection can produce false, misleading or clinically irrelevant results.
The correct material should be collected from the correct anatomical site using suitable aseptic technique and an appropriate container.
When clinically safe and appropriate, culture specimens are often best obtained before the first antimicrobial dose.
Blood Culture
Blood cultures are obtained when bloodstream infection is suspected. Meticulous skin antisepsis is important because contamination with skin organisms can produce false-positive results.
Urine
A clean-catch midstream urine specimen is commonly used to investigate urinary tract infection.
Sputum
A useful sputum specimen should represent lower respiratory secretions rather than saliva.
CSF
Cerebrospinal fluid is normally sterile. Suspected meningitis is an urgent clinical situation requiring rapid laboratory evaluation.
Stool
Stool may be examined for bacterial pathogens, protozoa, helminths, toxins, antigens or nucleic acids depending on the clinical syndrome.
Wounds
Where possible, deep material or aspirated infected material may provide greater diagnostic value than superficial contamination.
Gram Stain
Gram staining provides rapid information about bacterial morphology, arrangement and Gram reaction.
Acid-Fast Stain
Acid-fast staining is particularly important for mycobacteria.
Wet Preparation
Wet preparations may be useful for motility, cells, fungi or parasites depending on the specimen.
Culture permits microorganisms to multiply under controlled laboratory conditions.
Identification may involve colony morphology, Gram staining, biochemical reactions, antigen detection and molecular techniques.
Common Biochemical Tests
Catalase, coagulase, oxidase, urease and carbohydrate-utilisation tests are examples of classical methods used to differentiate bacteria.
Susceptibility Testing
Antimicrobial susceptibility testing helps determine which agents are likely to inhibit a bacterial isolate.
Clinical Bacteriology and Bacterial Diseases
Causative organism. Staphylococcus aureus is a Gram-positive, catalase-positive, usually coagulase-positive coccus that commonly forms clusters.
Clinical disease. The organism commonly causes folliculitis, furuncles, carbuncles, abscesses, cellulitis and wound infection. Infection may remain localised or progress into deeper tissues and bloodstream infection.
Pathogenesis. Skin barrier disruption allows colonising organisms to invade. Adhesins, enzymes, toxins and immune-evasion mechanisms contribute to inflammation and abscess formation.
Diagnosis. Diagnosis is often clinical. Purulent material or deep wound specimens may be cultured when indicated. Gram staining may reveal Gram-positive cocci in clusters. Culture and susceptibility testing are particularly valuable in severe, recurrent or healthcare- associated infection.
Treatment. Drainage is an essential component of management for many abscesses. When systemic antimicrobial treatment is required, selection should consider whether MSSA or MRSA is likely and should follow local susceptibility results and guidelines. Anti-staphylococcal beta-lactams are commonly used for susceptible MSSA, while MRSA may require agents such as vancomycin or other appropriate anti-MRSA therapy in serious infection.
Nursing management. Assess pain, erythema, warmth, swelling and drainage. Perform wound care using appropriate aseptic technique, administer prescribed antibiotics, monitor temperature and systemic status and educate the patient about hygiene and completion of therapy.
Prevention. Hand hygiene, appropriate wound covering, environmental cleaning and avoidance of sharing contaminated personal items reduce spread.
Bloodstream infection with S. aureus is potentially life-threatening because the organism may disseminate to the heart, bones, joints and other organs.
Diagnosis. Multiple blood cultures and careful search for the source are important. Persistent bacteraemia may suggest endocarditis, infected vascular devices or another deep focus.
Treatment. Prompt intravenous antimicrobial treatment is required and should be guided by methicillin susceptibility. Removal or drainage of an infected focus may be necessary.
Nursing management. Monitor haemodynamic status, temperature, consciousness, urine output and other signs of organ dysfunction. Obtain cultures as ordered and administer antimicrobial therapy promptly.
Group A Streptococcus pyogenes is an important bacterial cause of acute pharyngitis.
Clinical features. Sore throat, fever, tonsillar inflammation and tender cervical lymph nodes may occur. Cough and prominent coryza favour a viral cause.
Diagnosis. Clinical assessment may be supported by rapid antigen testing or throat culture where appropriate.
Treatment. Penicillin-class therapy remains a standard treatment for susceptible group A streptococcal pharyngitis. Allergy and local guidance determine alternatives.
Nursing care. Encourage hydration, pain relief, adherence to prescribed treatment and infection-prevention measures.
Complications. Suppurative complications and immune-mediated complications such as acute rheumatic fever may occur.
Scarlet fever results from toxin-producing strains of group A streptococcus, usually in association with pharyngitis.
Patients develop fever, sore throat and a characteristic diffuse erythematous rash.
Diagnosis and antibiotic treatment follow principles used for group A streptococcal infection. Nursing care focuses on symptom relief, hydration, antimicrobial adherence and recognition of complications.
Streptococcus pneumoniae is an encapsulated Gram-positive diplococcus and an important cause of community-acquired pneumonia.
Clinical features. Fever, cough, sputum production, chest discomfort, tachypnoea and dyspnoea may occur.
Diagnosis. Assessment may include chest radiography, oxygenation and selected microbiological testing depending on disease severity.
Treatment. Antibiotic selection depends on severity, resistance patterns, comorbidity and treatment setting. Beta-lactam therapy is commonly used, with additional agents in selected patients according to current pneumonia guidelines.
Nursing management. Monitor respiratory rate, oxygen saturation, breath sounds, temperature, hydration and mental status. Administer prescribed antibiotics and oxygen where indicated.
Vaccination is an important preventive measure for eligible groups.
Pneumococcus is an important cause of acute bacterial meningitis. Disease may present with fever, severe headache, neck stiffness, altered consciousness and neurological complications.
CSF examination, culture and molecular testing may aid diagnosis. Treatment requires urgent intravenous antibiotics capable of penetrating the central nervous system. Empirical regimens commonly include a third-generation cephalosporin with additional coverage according to local resistance patterns until microbiological results are available.
Nursing priorities include neurological observation, seizure precautions where indicated, monitoring of consciousness, temperature, fluid balance and rapid administration of prescribed therapy.
Neisseria meningitidis is a Gram-negative diplococcus capable of causing meningitis and fulminant bloodstream infection.
Transmission occurs mainly through respiratory secretions during close contact.
Diagnosis involves blood and/or CSF testing. Treatment requires urgent effective intravenous antibiotics, commonly a third-generation cephalosporin while susceptibility is being established.
Droplet precautions are important during the infectious period. Close contacts may require chemoprophylaxis according to public- health guidance.
Gonorrhoea is caused by Neisseria gonorrhoeae, a Gram-negative diplococcus that infects mucosal surfaces.
It may produce urethritis, cervicitis, pelvic inflammatory disease, epididymal infection, proctitis, pharyngitis or disseminated disease. Some infections are asymptomatic.
Nucleic-acid amplification tests are commonly used for diagnosis. Current guidelines generally use ceftriaxone-based treatment, with additional treatment for possible chlamydial coinfection when it has not been excluded.
Nursing care includes confidential counselling, partner-management education, adherence support and prevention of reinfection.
E. coli is the leading cause of many community-acquired urinary tract infections.
Cystitis commonly presents with dysuria, urinary frequency, urgency and suprapubic discomfort.
Diagnosis may involve urinalysis and urine culture. Antibiotic choice should consider local resistance patterns and the distinction between uncomplicated and complicated UTI.
Nursing responsibilities include correct urine collection, hydration education where appropriate, medication adherence and recognition of progression to upper urinary disease.
Pyelonephritis is infection involving the renal pelvis and kidney, commonly caused by ascending Gram-negative organisms such as E. coli.
Fever, flank pain, urinary symptoms, nausea and systemic illness may occur.
Urine culture is important. Blood cultures may be indicated in severe disease. Antimicrobial therapy depends on severity and local resistance. Severely ill patients may require intravenous therapy and hospital care.
Nurses monitor temperature, hydration, urine output, pain, renal function indicators and systemic deterioration.
Typhoid fever is a systemic infection caused principally by Salmonella enterica serovar Typhi.
Transmission occurs through ingestion of food or water contaminated with human faecal material.
Patients may develop prolonged fever, headache, malaise, abdominal symptoms and systemic complications.
Blood culture is particularly useful early in disease. Stool culture may become positive during illness.
Treatment requires an effective antimicrobial selected according to regional resistance patterns. Ceftriaxone and azithromycin are among commonly used options in many settings; fluoroquinolone resistance has limited empirical use in many regions.
Nursing care includes hydration, fever monitoring, nutrition, observation for intestinal bleeding or perforation and public-health education on sanitation and safe water.
Non-typhoidal Salmonella commonly causes acute gastroenteritis following contaminated food or animal exposure.
Treatment is primarily rehydration in uncomplicated disease. Antibiotics are reserved for severe disease and selected high-risk patients because unnecessary treatment may not improve ordinary self-limited gastroenteritis.
Nursing priorities include hydration assessment, oral rehydration, monitoring stool losses and food-safety education.
Shigella species cause inflammatory diarrhoeal disease and may produce fever, abdominal cramps and bloody stools.
Only a small inoculum is required for transmission, making strict hand hygiene particularly important.
Diagnosis may involve stool culture or molecular testing. Rehydration is essential. Antibiotic therapy is considered for moderate to severe disease based on susceptibility and local guidelines.
Cholera is an acute secretory diarrhoeal disease caused by toxigenic Vibrio cholerae.
The organism colonises the small intestine and produces cholera toxin, leading to massive secretion of water and electrolytes.
Patients may develop sudden profuse watery diarrhoea and rapidly progress to severe dehydration and circulatory collapse.
Diagnosis during outbreaks may be clinical with laboratory confirmation according to public-health protocols.
Rapid rehydration is the foundation of treatment. Oral rehydration solution is used whenever possible, while severe dehydration requires intravenous fluid replacement. Antibiotics may shorten illness in severe cases and should follow current local susceptibility guidance.
Campylobacter jejuni is an important bacterial cause of gastroenteritis associated with contaminated poultry, food and water.
Diarrhoea, abdominal pain and fever are common. Some patients develop bloody stools.
Management is mainly supportive with rehydration. Macrolide therapy may be used in severe or high-risk disease according to guidelines.
Helicobacter pylori colonises gastric mucosa and is associated with chronic gastritis, peptic ulcer disease and increased risk of gastric malignancy.
Diagnosis may involve urea breath testing, stool antigen testing or endoscopic methods.
Eradication requires combination therapy using acid suppression together with multiple antimicrobial agents. Selection should follow current regional resistance and treatment guidelines.
Pseudomonas aeruginosa is a Gram-negative environmental bacillus important in healthcare-associated infection and in patients with damaged host defences.
It may cause pneumonia, wound infection, urinary infection, bloodstream infection and infection associated with burns or devices.
Treatment requires an antipseudomonal antimicrobial selected from agents such as piperacillin-tazobactam, ceftazidime, cefepime, selected carbapenems, fluoroquinolones or other agents according to susceptibility and disease severity.
Resistance can be extensive; culture and susceptibility testing are therefore especially important.
Diphtheria is caused by toxin-producing Corynebacterium diphtheriae.
Respiratory disease can produce pharyngitis and a characteristic adherent pseudomembrane. Systemic toxin effects may involve the heart and nervous system.
Treatment requires urgent diphtheria antitoxin plus appropriate antibiotic therapy such as a macrolide or penicillin according to guidelines.
Isolation, contact management and vaccination are critical public- health measures.
Pertussis is caused by Bordetella pertussis and produces a prolonged respiratory illness characterised by severe paroxysmal coughing.
Young infants are at greatest risk of severe complications.
PCR and other respiratory testing may support diagnosis. Macrolides are commonly used to eradicate the organism and reduce transmission.
Nursing management includes respiratory observation, feeding and hydration support and monitoring infants for apnoea.
Tetanus is caused by neurotoxin produced by Clostridium tetani following contamination of a wound.
The toxin interferes with inhibitory neurotransmission and produces muscular rigidity and painful spasms.
Management requires wound care, neutralisation of unbound toxin with tetanus immune globulin, antimicrobial therapy such as metronidazole, control of spasms, airway support and intensive supportive care in severe disease.
Vaccination is the major preventive strategy.
Botulism is a neuroparalytic disease caused by botulinum toxin, usually produced by Clostridium botulinum.
Patients develop descending flaccid paralysis and may progress to respiratory failure.
Management requires urgent administration of appropriate antitoxin and intensive supportive care, including mechanical ventilation when necessary.
Clostridioides difficile can cause antibiotic-associated diarrhoea and colitis when normal intestinal microbiota are disrupted.
Diagnosis combines compatible diarrhoeal illness with appropriate toxin or molecular testing.
Common modern therapies include oral vancomycin or fidaxomicin according to disease severity and current guidance.
Because spores are environmentally resistant, infection-control measures include contact precautions and appropriate environmental decontamination.
Tuberculosis is caused principally by Mycobacterium tuberculosis, an acid-fast bacillus with a lipid-rich cell envelope.
Pulmonary TB spreads mainly through airborne particles produced by an infectious patient.
Clinical manifestations include persistent cough, fever, night sweats, fatigue, weight loss and sometimes haemoptysis.
Diagnosis uses appropriate respiratory specimens and may include rapid molecular testing, microscopy and culture.
Treatment requires multidrug antituberculous therapy under national TB programme guidance. Standard drug-susceptible regimens use combinations that commonly include isoniazid, rifampicin, pyrazinamide and ethambutol during appropriate phases. Drug-resistant TB requires specialised regimens based on resistance testing.
Nurses support sputum collection, airborne infection control, adherence, nutrition, monitoring for adverse drug effects and continuity of care.
Leprosy is a chronic infection caused by Mycobacterium leprae that affects skin and peripheral nerves.
Clinical manifestations include hypopigmented or erythematous skin lesions with altered sensation, peripheral nerve involvement and, in advanced disease, disability.
Treatment uses WHO multidrug therapy. Core agents include rifampicin, dapsone and clofazimine, with regimen and duration based on disease classification and national programme guidance.
Nursing care includes sensory assessment, wound prevention, disability prevention, adherence support and reduction of stigma.
Syphilis is caused by the spirochaete Treponema pallidum. Disease progresses through primary, secondary, latent and sometimes tertiary stages.
Diagnosis generally uses serological tests, supported by direct methods in selected lesions.
Penicillin remains the cornerstone of treatment. Pregnant patients with syphilis require penicillin therapy to prevent congenital infection.
Nursing care includes confidential counselling, partner management, screening in pregnancy and adherence to follow-up testing.
Clinical Virology and Viral Diseases
Influenza is an acute respiratory illness caused by influenza viruses. Fever, headache, myalgia, malaise and cough are common.
Diagnosis is frequently clinical during recognised transmission, although molecular respiratory testing is useful in selected cases.
Antiviral medicines such as neuraminidase inhibitors may be used in eligible patients, particularly when treatment is started early or when severe or high-risk disease is present.
Nursing care includes hydration, fever management, respiratory assessment and infection-control precautions.
COVID-19 is caused by SARS-CoV-2 and ranges from asymptomatic infection to severe respiratory and systemic disease.
Diagnosis may use antigen or nucleic-acid testing depending on clinical circumstances.
Management depends on severity and individual risk. Supportive care, oxygen when indicated and current antiviral or immunomodulatory therapy may be used in eligible patients according to contemporary guidelines.
Nursing priorities include respiratory assessment, oxygenation, fluid balance, thrombosis awareness, isolation precautions and patient education.
RSV is an important respiratory virus, especially in infants, older adults and vulnerable patients.
Infants may develop bronchiolitis with tachypnoea, wheezing, difficulty feeding and hypoxaemia.
Treatment is mainly supportive. Nursing care focuses on respiratory monitoring, hydration and feeding support.
Measles is a highly contagious viral illness characterised by fever, cough, coryza, conjunctivitis and a generalised maculopapular rash.
Complications include pneumonia, diarrhoea, otitis and encephalitis. Vitamin A is recommended in children with measles according to clinical guidance.
Vaccination is the principal preventive measure. Airborne precautions are necessary in healthcare settings.
Mumps commonly causes parotid swelling and fever. Complications may include orchitis, meningitis and pancreatitis.
Management is supportive. Prevention depends principally on vaccination.
Rubella usually causes a mild febrile rash illness but is especially important because infection during pregnancy can result in congenital rubella syndrome.
Management is supportive. Prevention through vaccination is essential.
Varicella-zoster virus causes chickenpox during primary infection. Disease is characterised by crops of pruritic vesicular lesions.
Most healthy children require supportive care. Antiviral therapy such as acyclovir may be indicated in selected high-risk or severe cases.
Airborne and contact precautions are important in healthcare.
HSV-1 and HSV-2 cause mucocutaneous disease and can also cause encephalitis, neonatal infection and disseminated disease.
Diagnosis may involve PCR or lesion testing. Acyclovir, valacyclovir and related antivirals are commonly used.
Herpes zoster results from reactivation of latent varicella-zoster virus within sensory ganglia.
Patients usually develop a painful unilateral vesicular eruption in a dermatomal distribution.
Antiviral treatment is particularly beneficial when initiated early and in patients at increased risk of complications.
Hepatitis A virus spreads primarily by the faecal–oral route. Disease is acute and does not cause chronic infection.
Treatment is supportive. Prevention includes sanitation, safe food and water and vaccination where indicated.
Hepatitis B virus is transmitted through blood and certain body fluids and can also be transmitted perinatally.
Infection may be acute or chronic. Chronic disease can progress to cirrhosis and hepatocellular carcinoma.
Diagnosis relies on characteristic serological and molecular markers.
Chronic infection may require antiviral treatment with potent nucleos(t)ide analogues such as tenofovir or entecavir according to specialist guidelines.
Vaccination, safe injection practice and prevention of perinatal transmission are central preventive measures.
Hepatitis C is primarily blood borne and frequently produces chronic infection.
Untreated chronic disease can progress to cirrhosis and liver cancer. Modern direct-acting antiviral combinations can cure most treated patients.
Nurses support testing, treatment adherence, liver-health education and prevention of blood exposure.
Human immunodeficiency virus is a retrovirus that progressively impairs immune function, especially through effects on CD4-positive T lymphocytes.
Transmission occurs through sexual exposure, blood exposure and mother-to-child transmission.
Diagnosis uses validated antibody/antigen and molecular algorithms.
Treatment uses combination antiretroviral therapy. Modern ART suppresses viral replication, restores immune function and markedly reduces morbidity and transmission.
Nurses provide adherence counselling, monitor for opportunistic infection and treatment adverse effects, maintain confidentiality and combat stigma.
Rabies is a fatal encephalitic illness caused by rabies virus, usually transmitted by the bite or saliva exposure of an infected mammal.
Once neurological symptoms develop, survival is extremely rare. Therefore prevention after exposure is critical.
Immediate thorough wound washing followed by appropriate rabies vaccination and rabies immunoglobulin when indicated can prevent disease.
Poliovirus is transmitted primarily by the faecal–oral route. Most infections are asymptomatic, but a minority progress to neurological disease and acute flaccid paralysis.
There is no specific antiviral cure. Prevention depends on vaccination and strong surveillance.
Yellow fever is a mosquito-borne flavivirus infection occurring in parts of Africa and South America.
Severe disease may produce fever, jaundice, haemorrhage and organ failure.
Treatment is supportive. Vaccination and mosquito-control measures are highly important for prevention.
Dengue is a mosquito-borne flavivirus infection that can range from mild febrile illness to severe dengue with plasma leakage, haemorrhage and shock.
Diagnosis uses antigen, molecular or serological testing depending on disease timing.
Treatment is supportive and requires careful fluid management. Nurses monitor circulation, urine output, bleeding and warning signs of severe disease.
Lassa fever is a viral haemorrhagic fever endemic in parts of West Africa, including Nigeria.
Transmission may occur following exposure to infected rodent excreta and through person-to-person contact with infectious body fluids.
Illness ranges from mild disease to severe multisystem infection. Diagnosis requires specialised laboratory methods.
Management requires strict infection-prevention measures, supportive care and specialist treatment according to current national protocols. Antiviral therapy may be considered under specialist guidance.
Ebola virus disease is a severe viral haemorrhagic fever. Transmission occurs through direct contact with infected body fluids and contaminated material.
Management requires specialist isolation, intensive supportive care and outbreak-response measures. Specific therapeutics may be available for particular Ebola virus species under expert protocols.
Nursing care demands meticulous PPE use, safe specimen handling and strict prevention of occupational exposure.
Clinical Mycology
Oral candidiasis occurs when Candida overgrows on oral mucosa, often in association with antimicrobial exposure, immunosuppression, infancy, older age or other predisposing factors.
White plaques and oral discomfort may occur.
Treatment commonly uses topical antifungals or systemic fluconazole depending on severity and patient factors.
Nurses provide oral care, medication education and assessment for underlying predisposing conditions.
Invasive candidiasis occurs when Candida enters the bloodstream or deep tissues, often in critically ill or immunocompromised patients.
Blood cultures and additional investigations are used for diagnosis. Initial therapy commonly includes an echinocandin in seriously ill adults, with treatment adjusted according to species, susceptibility and clinical response.
Vascular catheter management may be important.
Aspergillus species are environmental moulds. Disease ranges from allergic syndromes to invasive infection.
Invasive pulmonary aspergillosis occurs mainly in patients with major immune suppression.
Diagnosis may use imaging, fungal biomarkers, microscopy, culture and molecular methods.
Voriconazole and other mould-active antifungal agents are commonly used in invasive disease according to specialist guidance.
Cryptococcus species can cause pulmonary disease and meningitis, especially in people with major cellular immune suppression.
Cryptococcal antigen testing is highly useful in diagnosis. CSF examination is important when meningitis is suspected.
Severe CNS disease is treated with specialist antifungal regimens commonly involving amphotericin B and flucytosine followed by fluconazole phases.
Nursing care includes neurological monitoring, medication toxicity monitoring and careful fluid/electrolyte assessment.
Dermatophytes infect keratinised tissues such as skin, hair and nails. Clinical forms include tinea corporis, tinea capitis, tinea pedis and tinea unguium.
Diagnosis may be clinical or supported by microscopy and fungal culture.
Topical antifungal agents are suitable for many localised skin infections, while scalp or extensive disease may require systemic therapy.
Nursing education includes skin hygiene, keeping affected areas dry and avoiding sharing contaminated clothing or grooming items.
Clinical Parasitology and Tropical Diseases
Malaria is caused by Plasmodium parasites and transmitted mainly through infected female Anopheles mosquitoes. P. falciparum is particularly associated with severe disease in Africa.
Parasites first multiply in hepatocytes before entering erythrocytes. Repeated red-cell infection and rupture contribute to fever and anaemia.
Diagnosis uses validated malaria microscopy or rapid diagnostic testing.
Uncomplicated falciparum malaria is generally treated with an effective artemisinin-based combination therapy according to current national guidance.
Severe malaria requires urgent parenteral therapy, commonly artesunate, followed by a complete oral regimen when the patient can tolerate oral treatment.
Nursing management includes neurological assessment, temperature, glucose, hydration, urine output, anaemia assessment and recognition of respiratory or circulatory deterioration.
Amoebiasis is caused by Entamoeba histolytica and is transmitted through ingestion of mature cysts from faecally contaminated food or water.
Intestinal disease may produce abdominal pain and bloody diarrhoea. The organism can also produce amoebic liver abscess.
Diagnosis may use stool antigen, molecular testing, microscopy and imaging where extraintestinal disease is suspected.
Invasive disease is commonly treated with metronidazole or tinidazole followed by a luminal amoebicide to eradicate intestinal colonisation.
Giardia duodenalis causes intestinal infection acquired through contaminated water, food or person-to-person spread.
Patients may develop diarrhoea, abdominal bloating and malabsorption.
Stool antigen, microscopy or molecular testing can establish the diagnosis.
Common treatment options include tinidazole, metronidazole or nitazoxanide according to individual circumstances.
Schistosomiasis is caused by blood flukes of the genus Schistosoma.
Human infection follows skin penetration by cercariae during contact with contaminated freshwater.
Urogenital schistosomiasis may produce haematuria and chronic urinary pathology, while intestinal/hepatic disease may cause abdominal and portal complications.
Diagnosis depends on parasite detection, antigen/serological methods and clinical context.
Praziquantel is the principal antiparasitic treatment.
Prevention includes safe water, sanitation, snail/vector control programmes and mass-treatment strategies in endemic communities.
Ascaris lumbricoides is a soil-transmitted nematode. Infection occurs following ingestion of embryonated eggs.
Larval migration may cause transient pulmonary symptoms, while heavy intestinal worm burdens may cause abdominal symptoms, malnutrition or intestinal obstruction.
Diagnosis commonly relies on detection of characteristic eggs in stool.
Albendazole or mebendazole are commonly used treatments.
Hookworms infect humans when larvae in contaminated soil penetrate the skin.
Adult worms attach to the intestinal mucosa and cause chronic blood loss, potentially resulting in iron-deficiency anaemia.
Diagnosis is made by stool microscopy.
Treatment commonly uses albendazole or mebendazole, together with management of iron deficiency when present.
Footwear, sanitation and deworming programmes reduce transmission.
Strongyloides stercoralis can persist for decades through autoinfection.
Immunosuppression can precipitate potentially fatal hyperinfection and dissemination.
Diagnosis may require repeated stool examination, specialised methods or serology.
Ivermectin is the preferred treatment in many clinical settings.
Taeniasis is intestinal infection with adult Taenia tapeworms following ingestion of inadequately cooked infected meat.
Treatment commonly includes praziquantel or niclosamide.
Taenia solium is additionally important because ingestion of its eggs can cause cysticercosis, including neurocysticercosis.
Onchocerciasis is caused by Onchocerca volvulus and transmitted by blackflies.
Disease can involve the skin and eyes and may lead to severe visual impairment.
Ivermectin is central to individual and community control programmes, with management coordinated according to endemic-area public-health guidance.
Lymphatic filariasis is caused by filarial nematodes transmitted by mosquitoes.
Chronic disease can produce lymphoedema, hydrocele and elephantiasis.
Treatment and mass drug-administration strategies differ between regions and depend on co-endemic infections. National programme and WHO guidance should therefore be followed.
Nursing care includes meticulous skin hygiene, lymphoedema care, prevention of secondary bacterial infection and psychosocial support.
Toxoplasmosis is caused by Toxoplasma gondii. Transmission can occur through undercooked infected meat, exposure to oocysts and congenital transmission.
Most immunocompetent infections are mild, but severe neurological or ocular disease can occur in immunocompromised patients. Congenital infection may produce serious fetal disease.
Diagnosis uses serological and molecular methods depending on the clinical syndrome.
Treatment of significant disease commonly involves combinations such as pyrimethamine, sulfadiazine and folinic acid under specialist management.
Clinical Infection Syndromes and Nursing Practice
Bloodstream Infection and Sepsis
Sepsis is a life-threatening condition resulting from a dysregulated host response to infection with associated organ dysfunction. Bacteria are common causes, but fungi and other microorganisms may also be responsible.
Clinical Recognition
Patients may demonstrate fever or hypothermia, tachycardia, tachypnoea, altered mental state, hypotension, reduced urine output, poor peripheral perfusion or other signs of organ dysfunction.
Microbiological Investigation
Blood cultures and cultures from the suspected infection source are important when clinically appropriate.
Management
Sepsis requires rapid clinical assessment, source control, appropriate antimicrobial therapy, circulatory support and organ support according to severity.
Healthcare-Associated Infection
Healthcare-associated infections develop during healthcare delivery and include catheter-associated urinary infection, central-line- associated bloodstream infection, surgical-site infection and ventilator-associated infection.
Contributing Factors
Invasive devices, poor hand hygiene, antimicrobial selection pressure, environmental contamination and vulnerable patient populations all contribute.
Role of Nurses
Nurses prevent healthcare-associated infection through hand hygiene, aseptic technique, device-care bundles, early removal of unnecessary devices, correct wound care, appropriate PPE and surveillance for infection.
Role of the Nurse in Clinical Microbiology
1. Recognition of Infection
The nurse identifies changes in temperature, respiratory status, mental status, wounds, urine characteristics, gastrointestinal symptoms and haemodynamic condition.
2. Specimen Collection
The nurse ensures that the correct specimen is collected using appropriate technique, labelled accurately and transported promptly.
3. Antimicrobial Administration
The nurse checks prescriptions, allergy status, timing, route and clinical response.
4. Monitoring for Adverse Effects
Many antimicrobial agents can affect renal, hepatic, neurological, haematological or gastrointestinal function.
5. Infection Prevention
Hand hygiene, PPE, isolation precautions and safe sharps handling are fundamental professional responsibilities.
6. Patient Education
Patients should understand why a medicine has been prescribed, why the treatment course matters and why antibiotics should not be shared or used without proper indication.
7. Public Health
Nurses participate in vaccination, surveillance, contact education, outbreak response and community disease prevention.
High-Yield Clinical Microbiology Principles
Microorganisms are not automatically pathogens. Normal colonisation must be distinguished from true infection.
The quality of a microbiology result depends strongly on specimen quality.
Gram staining remains a rapid way to characterise many bacterial infections.
Culture permits recovery and identification of living microorganisms and often allows antimicrobial susceptibility testing.
Molecular diagnostics permit rapid detection of specific microbial nucleic acids.
Antimicrobial resistance is driven partly by inappropriate antimicrobial exposure and spread of resistant organisms.
Nurses influence infection outcomes directly through specimen collection, antimicrobial administration, aseptic practice, infection prevention and early recognition of clinical deterioration.
Abbas Saleh
Abbas Saleh, RN, RM, B.Sc. Microbiology, BNSc is a nursing professional with an academic background in microbiology and a strong interest in clinical nursing education, infectious diseases and the development of accessible educational resources for nurses and other health-science students.
His combined background in microbiology and nursing informs the clinical approach used throughout this textbook, connecting microbial science with laboratory diagnosis, patient management, infection prevention and the practical responsibilities of nurses.
For Academic and Commercial Publication
Treatment recommendations should be checked against the most recent guidelines from relevant national and international authorities before each edition is published. Important sources include the Federal Ministry of Health Nigeria, Nigeria Centre for Disease Control and Prevention, National Tuberculosis and Leprosy Control Programme, National Malaria Elimination Programme, World Health Organization and recognised infectious-disease and antimicrobial susceptibility standards.
Because antimicrobial resistance differs geographically, culture and susceptibility information and local antimicrobial guidelines should take priority over a fixed textbook regimen when managing an individual patient.
Photographs and microscopy images intended for a commercially sold edition should have their individual licences checked and recorded in an image-attribution register. Public-domain, CC0 or appropriately licensed Creative Commons images are preferable.
Educational notice: This textbook is intended for nursing and health-science education. Clinical diagnosis and antimicrobial therapy must be individualised and based on current professional guidance, patient factors, microbiological findings and local antimicrobial-resistance data.