Microbiology in Nursing: Key Concepts and Pathogens

Why is microbiology important in nursing and allied health?

It helps prevent infections, guides treatment decisions, supports antimicrobial stewardship, and enables effective patient education.

What are HAIs and how can they be prevented?

Hospital-acquired infections; prevented through aseptic technique and understanding the human microbiome.

Why is differentiating between viral and bacterial infections important?

Because antibiotics treat bacteria, not viruses—misuse can lead to resistance.

How does interpreting lab reports support clinical decisions?

Identifying specific microbes helps guide appropriate treatment.

How does microbiological literacy help patient education?

Enables healthcare providers to explain antibiotic use, vaccines, and infection prevention.

What are the characteristics of viruses?

Acellular, 100-200 nm, DNA or RNA in a protein coat, obligate intracellular parasites.

Give examples of clinically significant viruses.

Influenza virus, HIV, SARS-CoV-2.

What are prions and why are they dangerous?

Misfolded proteins <10 nm, cause diseases like Creutzfeldt-Jakob, resistant to sterilization.

Key traits of bacteria?

Prokaryotic, ~1 µm, peptidoglycan walls, diverse shapes, reproduce by binary fission.

Name 3 types of clinically significant bacteria by Gram stain.

Gram-positive cocci: Staphylococcus aureus; Gram-negative rods: Escherichia coli; Spore-forming bacilli: Clostridioides difficile.

What is the difference between Gram-positive and Gram-negative bacteria?

Gram-positive have thick peptidoglycan walls and stain purple; Gram-negative have thin peptidoglycan walls, an outer membrane with LPS/endotoxin, and stain pink/red.

What makes archaea unique?

Prokaryotic, no peptidoglycan, often extremophiles, not known to cause human disease.

What are protozoa and give examples.

Unicellular eukaryotes, 10-100 µm, motile; examples include Plasmodium falciparum, Giardia lamblia.

What are fungi and give examples.

Eukaryotes with chitin cell walls; yeasts like Candida albicans, molds like Aspergillus fumigatus.

What are helminths?

Multicellular parasitic worms; examples include Taenia solium, Ascaris lumbricoides, Schistosoma species.

What is the human microbiome?

The community of microbes living in the human body that influences digestion, immunity, and mood.

What is dysbiosis?

Microbial imbalance, often after antibiotics, leading to opportunistic infections like Clostridioides difficile overgrowth.

Who proposed the idea of invisible particles causing disease?

Girolamo Fracastoro (1546).

Who first observed microorganisms under a microscope?

Antonie van Leeuwenhoek (1675).

What did Ignaz Semmelweis contribute to microbiology?

Showed that handwashing reduced puerperal fever.

What was John Snow's key discovery?

Linked cholera outbreak to contaminated water, founding epidemiology.

What are Louis Pasteur's major contributions?

Disproved spontaneous generation, developed pasteurization and vaccines for rabies and anthrax.

Who introduced antiseptic surgical techniques?

Joseph Lister.

What are Koch's Postulates?

Criteria to link specific microbes to specific diseases.

Who discovered penicillin and how?

Alexander Fleming discovered it accidentally from Penicillium notatum mold in 1928.

What did Howard Florey & Ernst Chain do?

Mass-produced penicillin, starting the antibiotic era.

What's the difference between miasma and germ theory?

Miasma theory says diseases come from bad air; germ theory states microorganisms cause disease.

What is aseptic technique?

Practices to prevent contamination and infection, like handwashing and sterile equipment.

Define sterilization, disinfection, antisepsis, degerming, and sanitization.

Sterilization: kills all microbes including spores;

Disinfection: reduces/eliminates pathogens on surfaces;

Antisepsis: reduces microbes on living tissue;

Degerming: mechanical removal of microbes (handwashing);

Sanitization: lowers microbial counts to safe public health levels.

What are the 4 Biological Safety Levels (BSL)?

BSL-1: minimal risk (e.g., nonpathogenic E. coli);

BSL-2: moderate risk (e.g., S. aureus);

BSL-3: serious airborne pathogens (e.g., M. tuberculosis);

BSL-4: deadly untreatable agents (e.g., Ebola virus).

Types of light microscopes and their uses?

Bright-field: basic viewing; Dark-field: unstained microbes; Phase-contrast: living cells with detail; Oil immersion: improved resolution at 100x.

Describe Gram stain results.

Gram-positive bacteria stain purple with thick peptidoglycan walls; Gram-negative stain pink/red with thin walls and outer membrane.

What is acid-fast stain used for?

Detecting bacteria with mycolic acid like Mycobacterium tuberculosis.

Name special stains and their targets.

Capsule stain, endospore stain, flagella stain — highlight virulence factors.

What are the three domains of life?

Bacteria, Archaea, Eukarya.

What defines each domain?

Bacteria: prokaryotes with peptidoglycan; Archaea: prokaryotes without peptidoglycan, often extremophiles; Eukarya: organisms with membrane-bound nuclei.

List the taxonomic hierarchy from highest to lowest.

Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species.

What is binomial nomenclature?

Two-part scientific naming system (Genus species), italicized with Genus capitalized.

Why is proper naming important in microbiology?

Ensures clarity and avoids confusion between similar species.

What are key structural features of prokaryotic cells?

Cell wall (peptidoglycan), plasma membrane, nucleoid (circular DNA), ribosomes, external appendages (flagella, pili, glycocalyx).

How does the bacterial cell wall protect cells?

Peptidoglycan provides shape, resists osmotic pressure to prevent lysis in hypotonic environments.

Difference between Gram-positive and Gram-negative cell walls?

Gram-positive: thick peptidoglycan, teichoic acids, stains purple.

Gram-negative: thin peptidoglycan, outer membrane with LPS, stains pink/red.

What clinical relevance does Lipid A in Gram-negative bacteria have?

Acts as endotoxin causing fever and septic shock.

Name 3 major bacterial shapes.

Coccus (round), Bacillus (rod), Spirillum/Spirochete (spiral).

What is binary fission?

Asexual reproduction where one bacterium splits into two identical daughter cells.

What are fimbriae and their function?

Short protein filaments used for attachment to host tissues.

What is the role of capsules in bacteria?

Protects against desiccation and phagocytosis; aids in adherence.

Name the antibiotic class targeting bacterial cell walls.

β-lactams (penicillins, cephalosporins) and glycopeptides (vancomycin).

What is the significance of plasmids in bacteria?

Carry genes for antibiotic resistance; spread via horizontal gene transfer.

Which bacteria form endospores? Name two clinically important examples.

Bacillus and Clostridium species (e.g., Bacillus anthracis, Clostridium difficile).

What is the Gram reaction and clinical importance of Staphylococcus aureus?

Gram-positive cocci in clusters; causes skin infections, pneumonia, MRSA is antibiotic-resistant.

What type of bacteria is Escherichia coli and what diseases does it cause?

Gram-negative rod; causes UTIs, diarrhea, sepsis.

How do bacteria acquire antibiotic resistance genes?

Through conjugation, transformation, and transduction.

Why is infection control critical in healthcare regarding bacteria?

Prevents spread of resistant bacteria; requires hand hygiene, aseptic technique, and antimicrobial stewardship.

What staining method is used for Mycobacterium tuberculosis?

Acid-fast (Ziehl-Neelsen) stain.

Name the main oxygen requirements types of bacteria.

Obligate aerobes, obligate anaerobes, facultative anaerobes, microaerophiles, aerotolerant.

What is the function of bacterial flagella?

Motility (movement).

What role do porins in Gram-negative bacteria play?

Allow nutrient entry; restrict some antibiotics.

Name a bacterial genus that lacks a cell wall.

Mycoplasma.

What defines prokaryotes compared to eukaryotes?

Lack membrane-bound nucleus, have circular DNA in nucleoid, smaller 70S ribosomes, no membrane-bound organelles.

What happens to a bacterial cell in hypotonic vs. hypertonic solutions?

Hypotonic: water enters; with cell wall, cell resists lysis; without wall, may lyse.

Hypertonic: water leaves; plasmolysis occurs.

What is the function of teichoic acids in Gram-positive bacteria?

Contribute to virulence and inflammation.

What is the periplasmic space in Gram-negative bacteria?

Space between outer and inner membranes containing enzymes.

What are the components of LPS (lipopolysaccharide)?

Lipid A (endotoxin), core polysaccharide, O-antigen.

What is the significance of biofilms in bacterial infections?

Protect bacteria from antibiotics and immune response, contribute to chronic infections.

Describe the main types of bacterial arrangements.

Diplococci (pairs), streptococci (chains), staphylococci (clusters), tetrads, sarcinae (cubical packets), palisades (parallel rods).

What does the Gram stain differentiate?

Bacteria by cell wall structure: Gram-positive (purple), Gram-negative (pink/red).

What is the glycocalyx?

Sugar-rich outer layer; includes capsule and slime layer.

What is the difference between a capsule and slime layer?

Capsule is organized and protective; slime layer is loose and aids biofilm formation.

What are the different flagella arrangements?

Monotrichous (single), amphitrichous (both ends), lophotrichous (tufts), peritrichous (all over).

What size and type are bacterial ribosomes?

70S (30S + 50S subunits).

What are bacterial inclusions?

Storage granules for nutrients (e.g., glycogen, sulfur).

How do bacteria exchange genetic material?

Conjugation (via F pilus), transformation (uptake free DNA), transduction (via bacteriophage).

List oxygen requirement types with examples.

Obligate aerobes (Mycobacterium), obligate anaerobes (Clostridium), facultative anaerobes (E. coli), microaerophiles (Helicobacter), aerotolerant (Streptococcus).

What temperatures do mesophiles prefer?

20-45°C (human body temp range).

What antibiotic class targets bacterial protein synthesis?

Aminoglycosides, tetracyclines, macrolides, lincosamides.

Name an antibiotic targeting bacterial DNA synthesis.

Fluoroquinolones.

What is the mode of action of sulfonamides?

Inhibit folate synthesis (metabolic pathway inhibitors).

How do polymyxins work?

Disrupt Gram-negative outer membrane.

What are R plasmids?

Plasmids carrying antibiotic resistance genes.

Name a spore-forming Gram-positive pathogen causing gas gangrene.

Clostridium perfringens.

How are bacterial endospores destroyed?

Autoclaving (steam under pressure) or sporicidal agents like bleach.

What class of bacteria does Neisseria gonorrhoeae belong to?

Gram-negative diplococcus.

What disease does Vibrio cholerae cause?

Cholera—profuse watery diarrhea.

Which bacteria is a common cause of healthcare-associated pneumonia?

Klebsiella pneumoniae.

How is tuberculosis transmitted?

Airborne droplets.

What bacteria can grow at refrigeration temperatures and cause meningitis?

Listeria monocytogenes.

What bacterial structure is targeted by isoniazid?

Mycolic acid synthesis in acid-fast bacteria.

Why is knowledge of bacterial morphology important clinically?

Helps rapid identification and guides empiric antibiotic therapy.

What is the nurse's role in infection control?

Hand hygiene, aseptic technique, isolation precautions, antimicrobial stewardship.

What causes pseudomembranous colitis?

Clostridioides difficile overgrowth after antibiotic use.

Which bacterium causes necrotizing fasciitis?

Streptococcus pyogenes.

What bacterial group includes cyanobacteria?

Phototrophic bacteria.

What are microaerophiles?

Bacteria that require low oxygen levels.

What is the clinical significance of bacterial capsules?

Enhance virulence by evading phagocytosis.

Name three bacteria that produce endospores.

Bacillus anthracis, Clostridium tetani, Clostridioides difficile.

What kind of bacteria are Mycoplasmas?

Lack cell walls; resistant to β-lactam antibiotics.

What pathogen is associated with foodborne gastroenteritis caused by a curved rod?

Campylobacter jejuni.

What bacterial structure allows conjugation?

F pilus (sex pilus).

What distinguishes prokaryotes from eukaryotes?

Prokaryotes lack a membrane-bound nucleus and have circular DNA in a nucleoid.