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🌍 MRCS Part A · subject
MRCS Part A Microbiology Syllabus
The Microbiology syllabus for MRCS Part A in full: 9 chapters, 35 topics and 111 sub-topics, every one listed below, plus 52 Microbiology flashcards with answers.
Microbiology syllabus: all 9 chapters
Expand any chapter to see its topics and sub-topics.
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Introduction to Microbiology
3 topics- History of Microbiology
- Early Discoveries
- Golden Age of Microbiology
- Modern Microbiology
- Classification of Microorganisms
- Bacteria
- Viruses
- Fungi
- Protozoa
- Algae
- Microscopy
- Light Microscopy
- Electron Microscopy
- Fluorescence Microscopy
- History of Microbiology
-
Bacteriology
4 topics- Bacterial Structure
- Cell Wall
- Cell Membrane
- Cytoplasm
- Flagella
- Pili
- Spores
- Bacterial Physiology
- Growth and Reproduction
- Metabolism
- Genetic Exchange
- Pathogenic Bacteria
- Gram-Positive Bacteria
- Gram-Negative Bacteria
- Mycobacteria
- Spirochetes
- Bacterial Infections
- Respiratory Infections
- Gastrointestinal Infections
- Skin and Soft Tissue Infections
- Systemic Infections
- Bacterial Structure
-
Virology
4 topics- Virus Structure
- Capsid
- Envelope
- Genome
- Virus Replication
- Attachment and Entry
- Genome Replication
- Assembly and Release
- Pathogenic Viruses
- DNA Viruses
- RNA Viruses
- Retroviruses
- Viral Infections
- Respiratory Infections
- Gastrointestinal Infections
- Neurological Infections
- Systemic Infections
- Virus Structure
-
Mycology
4 topics- Fungal Structure
- Cell Wall
- Cell Membrane
- Hyphae
- Spores
- Fungal Physiology
- Growth and Reproduction
- Metabolism
- Pathogenic Fungi
- Yeasts
- Molds
- Dimorphic Fungi
- Fungal Infections
- Superficial Mycoses
- Cutaneous Mycoses
- Subcutaneous Mycoses
- Systemic Mycoses
- Fungal Structure
-
Parasitology
4 topics- Protozoa
- Amoebae
- Flagellates
- Ciliates
- Sporozoa
- Helminths
- Nematodes
- Trematodes
- Cestodes
- Ectoparasites
- Lice
- Mites
- Fleas
- Ticks
- Parasitic Infections
- Intestinal Infections
- Blood and Tissue Infections
- Vector-Borne Infections
- Protozoa
-
Immunology
4 topics- Innate Immunity
- Physical Barriers
- Cellular Defenses
- Inflammation
- Adaptive Immunity
- Humoral Immunity
- Cell-Mediated Immunity
- Immunological Memory
- Immune Response to Infections
- Bacterial Infections
- Viral Infections
- Fungal Infections
- Parasitic Infections
- Immunopathology
- Hypersensitivity Reactions
- Autoimmune Diseases
- Immunodeficiency Disorders
- Innate Immunity
-
Microbial Genetics
4 topics- Genetic Material
- DNA Structure
- RNA Structure
- Gene Expression
- Transcription
- Translation
- Regulation of Gene Expression
- Genetic Variation
- Mutations
- Horizontal Gene Transfer
- Genetic Engineering
- Recombinant DNA Technology
- CRISPR-Cas9
- Genetic Material
-
Antimicrobial Agents
4 topics- Antibiotics
- Mechanisms of Action
- Spectrum of Activity
- Resistance Mechanisms
- Antiviral Agents
- Mechanisms of Action
- Resistance Mechanisms
- Antifungal Agents
- Mechanisms of Action
- Resistance Mechanisms
- Antiparasitic Agents
- Mechanisms of Action
- Resistance Mechanisms
- Antibiotics
-
Clinical Microbiology
4 topics- Specimen Collection and Transport
- Types of Specimens
- Transport Media
- Diagnostic Techniques
- Microscopy
- Culture Methods
- Molecular Methods
- Serological Methods
- Antimicrobial Susceptibility Testing
- Disk Diffusion Method
- Broth Dilution Method
- E-test
- Infection Control
- Sterilization and Disinfection
- Hospital-Acquired Infections
- Antibiotic Stewardship
- Specimen Collection and Transport
MRCS Part A Microbiology flashcards — 52 questions with answers
Who is regarded as the 'Father of Microbiology' and what did he first observe using his single-lens microscopes in the 1670s?
Antonie van Leeuwenhoek; he was the first to observe and describe live microorganisms ('animalcules'), including bacteria and protozoa.
State Koch's postulates, the four criteria used to establish that a specific microbe causes a specific disease.
1) The organism is found in all cases of the disease and absent in healthy hosts. 2) It can be isolated and grown in pure culture. 3) The cultured organism reproduces the disease when introduced into a healthy susceptible host. 4) It can be re-isolated from that experimentally infected host.
What key contributions did Louis Pasteur make to microbiology?
He disproved spontaneous generation, developed pasteurisation, established the germ theory of disease, and pioneered attenuated vaccines (e.g. rabies, anthrax, chicken cholera).
In the three-domain classification system of Carl Woese, what are the three domains and on which molecule is the classification based?
Bacteria, Archaea, and Eukarya; the classification is based on comparison of small-subunit (16S/18S) ribosomal RNA sequences.
How do prokaryotic cells differ fundamentally from eukaryotic cells?
Prokaryotes lack a membrane-bound nucleus and membrane-bound organelles, have 70S ribosomes and a single circular chromosome; eukaryotes have a true nucleus, membrane-bound organelles, 80S ribosomes and linear chromosomes.
Give the standard order of the biological taxonomic hierarchy from broadest to most specific.
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
What is the limit of resolution of the light microscope and roughly what magnification does it achieve?
Resolution limit is about $0.2\ \mu m$ (200 nm), with useful magnification up to approximately $\times 1000$ to $\times 1500$.
State the Abbe equation for the resolving power (d) of a microscope and define its terms.
$$d = \frac{0.61\,\lambda}{NA}$$ where $\lambda$ is the wavelength of light and $NA$ is the numerical aperture of the objective lens. Smaller $d$ means better resolution.
Why does the electron microscope achieve far higher resolution than the light microscope?
It uses a beam of electrons whose wavelength is vastly shorter than visible light, giving resolution down to about $0.2\ nm$ and magnifications over $\times 100{,}000$.
Outline the steps and key reagents of the Gram stain.
1) Crystal violet (primary stain). 2) Gram's iodine (mordant). 3) Alcohol/acetone (decolouriser). 4) Safranin (counterstain). Gram-positive cells retain crystal violet and appear purple; Gram-negative cells lose it and appear pink/red.
Compare the cell wall of Gram-positive and Gram-negative bacteria.
Gram-positive: thick peptidoglycan layer with teichoic acids, no outer membrane. Gram-negative: thin peptidoglycan layer plus an outer membrane containing lipopolysaccharide (LPS/endotoxin) and a periplasmic space.
What is the chemical nature and function of bacterial peptidoglycan (murein)?
A polymer of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by peptide bridges; it provides cell wall rigidity and osmotic protection. It is the target of penicillins and lysozyme.
What is bacterial LPS (lipopolysaccharide) and which component is toxic?
LPS is the major molecule of the Gram-negative outer membrane, composed of O-antigen, core polysaccharide and lipid A. Lipid A is the toxic endotoxin responsible for fever and septic shock.
Distinguish bacterial endotoxin from exotoxin.
Endotoxin is the lipid A of LPS, part of the Gram-negative cell wall, heat-stable, weakly immunogenic, causing fever/shock. Exotoxins are secreted proteins (Gram +/-), often heat-labile, highly immunogenic, and convertible to toxoids for vaccines.
What is a bacterial spore (endospore), which genera produce them, and why are they clinically important?
A dormant, highly resistant dehydrated structure containing dipicolinic acid and DNA. Produced by Bacillus and Clostridium. They resist heat, desiccation and disinfectants, surviving standard sterilisation and causing disease (e.g. tetanus, anthrax).
Describe the classification of bacteria by shape.
Cocci (spherical), bacilli (rods), spirilla/spirochaetes (spiral/helical), and vibrios (comma-shaped). Arrangements include diplo-, strepto- (chains) and staphylo- (clusters).
What is the function of bacterial fimbriae/pili versus flagella?
Fimbriae (common pili) mediate adhesion to surfaces; the sex pilus mediates conjugation/DNA transfer. Flagella provide motility.
Define the four phases of the bacterial growth curve.
Lag phase (adaptation, no division), log/exponential phase (maximal division), stationary phase (growth = death as nutrients deplete), and death/decline phase (net cell death).
Give the exponential growth equation relating cell number to generation number.
$$N = N_{0} \times 2^{n}$$ where $N_{0}$ is the initial number, $n$ is the number of generations, and $N$ is the final number of cells.
Classify bacteria according to their oxygen requirements.
Obligate aerobes (need $\ce{O2}$), obligate anaerobes (killed by $\ce{O2}$), facultative anaerobes (grow with or without $\ce{O2}$), microaerophiles (need low $\ce{O2}$), and aerotolerant anaerobes (tolerate but don't use $\ce{O2}$).
Show the other 32 Microbiology flashcards
Name the three mechanisms of horizontal gene transfer in bacteria.
Transformation (uptake of free/naked DNA), transduction (transfer via bacteriophage), and conjugation (direct transfer via a sex pilus/plasmid).
What are the major mechanisms of bacterial antibiotic resistance?
Enzymatic drug inactivation (e.g. beta-lactamases), alteration of the drug target, decreased drug uptake/reduced permeability, and increased efflux pump activity.
Which coagulase-positive coccus is a common cause of wound infection, abscesses and is often methicillin-resistant?
Staphylococcus aureus (MRSA when methicillin-resistant); Gram-positive, catalase-positive, coagulase-positive cocci in clusters.
Which Gram-positive organism causes gas gangrene, and what is its key laboratory feature?
Clostridium perfringens; an anaerobic, spore-forming Gram-positive bacillus that produces alpha-toxin (lecithinase) causing myonecrosis and gas in tissues.
What organism causes pseudomembranous colitis, and what typically precipitates it?
Clostridioides (Clostridium) difficile; typically follows broad-spectrum antibiotic use that disrupts normal gut flora, mediated by toxins A and B.
Which Gram-negative organism is a leading cause of surgical/urinary tract infection, is oxidase-positive and produces a blue-green pigment?
Pseudomonas aeruginosa; an aerobic Gram-negative bacillus producing pyocyanin, notable for multidrug resistance and biofilm formation.
Which bacterium causes tuberculosis and what staining property defines it?
Mycobacterium tuberculosis; it is acid-fast (stains with Ziehl-Neelsen due to mycolic acid in its cell wall) and does not Gram stain reliably.
What is the difference between primary and secondary intention wound healing regarding infection risk?
Primary intention closes clean wounds directly with minimal tissue loss and low infection risk; secondary intention leaves contaminated/open wounds to granulate and heal from the base, with higher bacterial colonisation and infection risk.
Name the classic clinical features (cardinal signs) of local infection/inflammation.
Rubor (redness), calor (heat), dolor (pain), tumor (swelling), and functio laesa (loss of function).
What is SIRS and how many criteria are required for its diagnosis?
Systemic Inflammatory Response Syndrome; diagnosed when at least 2 of: temperature >38 or <36 °C; heart rate >90 bpm; respiratory rate >20 or $PaCO_{2} < 4.3\ kPa$; white cell count >12 or <4 $\times 10^{9}/L$.
What organism causes tetanus and by what mechanism does its toxin act?
Clostridium tetani; tetanospasmin blocks release of inhibitory neurotransmitters (GABA/glycine) from spinal interneurons, causing unopposed muscle spasm (spastic paralysis).
Describe the basic structure of a virus.
A nucleic acid genome (DNA or RNA) enclosed in a protein capsid (made of capsomeres); together the nucleocapsid. Some viruses have an outer lipid envelope with glycoprotein spikes. Viruses lack their own metabolic machinery.
What are the two main types of viral capsid symmetry?
Helical symmetry (capsomeres arranged in a spiral around the nucleic acid) and icosahedral symmetry (20 triangular faces). Some viruses (e.g. poxviruses) are complex.
How does the Baltimore classification categorise viruses?
By genome type and replication strategy into 7 groups: dsDNA, ssDNA, dsRNA, (+)ssRNA, (-)ssRNA, ssRNA-RT (retroviruses), and dsDNA-RT.
List the stages of the viral replication cycle in order.
Attachment (adsorption), penetration/entry, uncoating, replication/biosynthesis (of nucleic acid and proteins), assembly (maturation), and release (by lysis or budding).
What enzyme is unique to retroviruses and what does it do?
Reverse transcriptase; an RNA-dependent DNA polymerase that transcribes the viral RNA genome into DNA, which is then integrated into the host genome by integrase.
Which cell type does HIV primarily infect via which receptor and co-receptors?
HIV infects CD4+ T-helper cells (and macrophages) by binding the CD4 receptor plus a chemokine co-receptor (CCR5 or CXCR4).
Compare the routes of transmission of hepatitis B and hepatitis A viruses.
Hepatitis B: blood-borne/parenteral, sexual and vertical transmission (DNA virus). Hepatitis A: faecal-oral route via contaminated food/water (RNA virus), causing self-limiting acute hepatitis.
Which virus causes chickenpox and shingles, and what is the mechanism linking the two conditions?
Varicella-zoster virus (VZV, a herpesvirus). Primary infection causes chickenpox; the virus becomes latent in dorsal root ganglia and reactivation causes shingles (herpes zoster).
What is a prion and how does it cause disease?
A prion is an infectious misfolded protein (PrP-Sc) with no nucleic acid. It induces normal cellular prion protein (PrP-C) to misfold, causing neurodegenerative spongiform encephalopathies (e.g. CJD). Prions resist standard sterilisation.
Which oncogenic virus is strongly associated with cervical carcinoma?
Human papillomavirus (HPV), particularly high-risk types 16 and 18; its E6 and E7 proteins inactivate p53 and Rb tumour suppressors.
Describe the general structure of a fungal cell and how it differs from a bacterium.
Fungi are eukaryotes with a nucleus and organelles, a cell wall of chitin and glucans, and a cell membrane containing ergosterol. Bacteria are prokaryotes with peptidoglycan walls and cholesterol-free membranes.
What is the target of azole and polyene antifungal agents in the fungal cell?
Both act on ergosterol in the fungal membrane: azoles inhibit ergosterol synthesis (14-alpha-demethylase); polyenes (e.g. amphotericin B) bind ergosterol directly, forming membrane pores.
Distinguish yeasts from moulds (filamentous fungi), and define a dimorphic fungus.
Yeasts are single round/oval cells that reproduce by budding; moulds grow as filamentous hyphae forming a mycelium. Dimorphic fungi grow as mould in the environment (cooler temps) and yeast in tissue at 37 °C (e.g. Histoplasma).
What is the difference between septate and aseptate (coenocytic) hyphae, giving an example of each?
Septate hyphae have cross-walls dividing cells (e.g. Aspergillus); aseptate/coenocytic hyphae lack regular cross-walls and are multinucleate (e.g. Mucor/Rhizopus).
Which yeast causes oral/vaginal thrush and invasive candidiasis, and what predisposes to it?
Candida albicans; predisposed by antibiotic use, immunosuppression, diabetes, indwelling lines and prolonged ICU stay. It is a dimorphic yeast forming germ tubes.
Which fungus causes invasive pulmonary aspergillosis and in whom?
Aspergillus fumigatus; a septate mould causing invasive disease predominantly in neutropenic and immunocompromised patients, and aspergilloma in pre-existing lung cavities.
What are dermatophytes and which tissues do they infect?
Keratinophilic fungi (Trichophyton, Microsporum, Epidermophyton) that infect keratinised tissue—skin, hair and nails—causing tinea (ringworm) infections.
Which protozoan causes malaria, how is it transmitted, and which species is most lethal?
Plasmodium species transmitted by the bite of the female Anopheles mosquito; Plasmodium falciparum causes the most severe, potentially fatal disease (cerebral malaria).
Which protozoan causes amoebic dysentery and liver abscess, and how is it transmitted?
Entamoeba histolytica; transmitted faecal-orally via cysts in contaminated food/water, causing bloody diarrhoea and characteristic 'anchovy paste' liver abscesses.
Compare the transmission and clinical target of the roundworm Ascaris lumbricoides versus the tapeworm Taenia.
Ascaris (nematode): faecal-oral egg ingestion, larvae migrate through lungs then mature in the small intestine causing obstruction. Taenia (cestode): ingestion of undercooked pork/beef cysticerci, adult tapeworm resides in the gut; T. solium eggs can cause neurocysticercosis.
Name two clinically important ectoparasites and the conditions they cause.
Sarcoptes scabiei mite causes scabies (intensely itchy burrows); Pediculus/Pthirus lice cause pediculosis (head/body/pubic lice) and can act as vectors for typhus and relapsing fever.
Same Microbiology syllabus in other exams
The Microbiology outline above is identical in these 3 exams:
MRCS Part A Microbiology FAQ
What is in the MRCS Part A Microbiology syllabus?
MRCS Part A Microbiology is split into 9 chapters: Introduction to Microbiology, Bacteriology, Virology, Mycology, Parasitology, Immunology, Microbial Genetics, Antimicrobial Agents and Clinical Microbiology. Together they contain 35 topics and 111 sub-topics.
How many chapters are in MRCS Part A Microbiology?
9 chapters, containing 35 topics and 111 sub-topics. The largest chapter is Bacteriology, with 4 topics.
Are there flashcards for MRCS Part A Microbiology?
Yes — a 52-card Microbiology deck, printed in full in the flashcards section of this page and available in the Examius app with spaced repetition. The free plan covers one exam of your choice, including its flashcards; Examius Pro, a one-time purchase, unlocks every other exam and deck.