Microbiology Flashcards by Adam Henderson

Microbiology:

Define: Pathogen,
Commensal,
Opportunistic pathogen, Virulence/pathogenicity
and asymptomatic carriage

• Pathogen
Organism that causes or is capable of causing disease
• Commensal
Organism which colonises the host but causes no disease in normal circumstances
• Opportunistic Pathogen
Microbe that only causes disease if host defences are compromised
• Virulence/Pathogenicity
The degree to which a given organism is pathogenic
• Asymptomatic carriage
When a pathogen is carried harmlessly at a tissue site where it causes no disease

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Microbiology:

Morphology of coccus/bacillus
Chains
Clusters
Curved rod? 
Spiral rod?

Coccus - ball
chain/clusters of cocci

Bacilllus - rod
Curved rod = vibrio
Spiral rod = spirochaete

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Microbiology:

Normal sterile areas of the body

Lungs, kidneys, bladder, gall bladder, vasculature

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Microbiology:
Gram staining
Purple?
Pink/red?

Purple = Gram positive (thick layer of peptidoglycan absorb stain)
Pink/red = Gram negative (thin layer due to 2 membranes)

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Microbiology:

Test for mycobacterium?(tuberculosis)

Ziehl-neelsen stain

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Microbiology:

Endotoxin vs Exotoxin 
What is it? 
Gram +/-?
Heat stable?
Antigenicity?
Can you make a toxoid?

Endotoxin - bacterial membrane component e.g. lipopolysaccharide Gram NEGATIVE
Heat stable
weak antigenicity
No toxoid

Endotoxin - secreted proteins both Gram +ve and -ve (mainly +ve)
Unstable in heat
Strong antigenicity
CAN BE MADE INTO A TOXOID VACCINE

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Microbiology:

Bacterial gene transfer?
3 methods

Transformation - DNA transfer via plasmids

Bacterial conjugation - sex pilus

Transduction - Phages transfer genetic material

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Microbiology:

Gram positive bacteria:
Staphylococcus
+ve coagulase?
how is it spread?

Virulence factors?
TSST?

S. aureus
- spread by aerosol and touch (carriers and shedders)

Virulence factors:

Pore forming toxins
Proteases
Toxic shock syndrome toxin (TSST)

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Microbiology:

What is MRSA multi-resistant s. aureus resistant to?
Treatment?

Beta-lactams
Gentamycin
Erythromycin
Tetracycline

Treatment = vancomycin

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Microbiology:

Gram positive bacteria:
Staphylococcus
-ve coagulase?

S. epidermidis (biofilms)

S. saprophyticus (acute cystitis)

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Microbiology:
Clusters or chains?

Staphylococcus
Streptococcus

Staphylococcus = clusters

Streptococcus = chains

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Microbiology:
Clusters or chains?

Staphylococcus
Streptococcus

Staphylococcus = clusters

Streptococcus = chains

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Microbiology:

Strep classification steps
-Haemolysis alpha or beta?

Alpha = partial, greening of blood agar plate

Beta = complete haemolysis clean strip around bacteria on BA

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Microbiology:

Streptococci examples:

Causes tonsillitis, cellulitis, impetigo
Causes pneumonia and meningitis
Oral Strep/Dental

1) S. pyogenes
2) S. pneumoniae
3) Viridan’s streptococci (alpha haemolytic)

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Microbiology:

Streptococci examples:

Causes tonsillitis, cellulitis, impetigo
Causes pneumonia and meningitis
Oral Strep

1) S. pyogenes
2) S. pneumoniae
3) Viridan’s streptococci (alpha haemolytic)

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Microbiology:

Corynebacterium diphtheriae
Type of vaccine?
Toxin?

Toxin inhibits protein synthesis

Vaccine is a toxoid

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Microbiology:

Gram negative bacteria:
Lipopolysaccharide
Endo or exotoxin
Which part of LPS is toxic?

Endotoxin

Toxic part is the lipid in the outer membrane

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Microbiology:

Agglutination test: antiserum to detect cell antigens
H - antigen is?
A - antigen is?

H-antigen = flagellum
A-antigen = polysaccharide

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Microbiology:

Strains;
ETEC? toxins?
EHEC? toxin?
EPEC?

Which is the most pathogenic?

Pedestal ones?

ETEC = Enterotoxigenic E. coli – travellers diarrhoea (heat liable and heat stable enterotoxins = Cl- efflux)

EHEC = Enterohemorrhagic E. coli - bloody diarrhoea (Shigella like toxin - SLT)

EPEC = Enteropathogenic E. coli
EHEC most pathogenic

EHEC and EPEC = pedestal formation

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Microbiology:

Strains;
ETEC?
EHEC/EPEC
EHEC

ETEC = Entero-toxigenic E. coli – travellers diarrhoea

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Microbiology:

Salmonella

3 forms of salmonellosis?

What they causes?
Dose needed?
How does it penetrate the intestinal epithelia?

serovars enteritidis = gastroenteritis (food poisoning)
serovars typhi/paratyphi = Enteric fever - TYPHOID

High infective dose needed
Penetrates through M-cells

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Microbiology:

Salmonella

2 strains?
What they causes?
Dose needed?
How does it penetrate the intestinal epithelia?

serovars enteritidis = gastroenteritis (food poisoning)
serovars typhi/paratyphi = Enteric fever - TYPHOID

High infective dose needed
Penetrates through M-cells

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Microbiology:

Funghi

Eukaryote or prokaryote? 
Cell wall? 
Heterotrophic
2 forms of funghi? 
are they budding/hyphea or spore forming

Funghi are eukaryote

Chitinous cell wall

Heterotrophic - need to acquire carbon

Moulds - spore forming and hyphae

Yeasts - budding

Microbiology:

Fungal infections
Common not severe
Rarely severe

Athletes foot/fungal nail infections caused by?

“mycosis” = fungal infection

Onychomycosis = fungal nail infection
caused by dermatophyte moulds

Microbiology: Candidiasis?

Fungal infection caused by a yeast called Candida Oral and Vaginal candida

Microbiology: Treatment for fungal infections? difficult as eukaryotic cells are similar to our own cells

- Echinocandins target cell wall - Polyenes - Azoles - pore forming by targeting cholesterol synthesising pathway

Microbiology: Principles of IPC (infection prevention control) - EPS?

Environment - cleaning, ward design Patient - Isolation Staff - PPE, isolation

Microbiology: example of commensal bacteria that can cause UTIs and Intra-abdominal infections Resistant to?

"Coliforms" - Carbapenemase producing enterobacteriaceae Colonise the skin below the waist, large bowel and most of the body Resistant to carbapenems and other beta lactams

``` Microbiology: what kills each of these? alcohol gel or hand washing? Norovirus C. difficile MRSA ```

Norovirus = hand washing C. difficile = hand washing MRSA = alcohol gel

Microbiology Virus - define structure? Are they living?

An infectious obligate intracellular parasite comprised of RNA/DNA surrounded by a protein coat Not technically living

Microbioogy: Viral replication steps? (5)

1) Attachment 2) Cell entry 3) Host cell interaction + replication o Translation of viral mRNA to produce structural proteins 4) Assembly of virion 5) Release of new virus particles

Microbiology: How do viruses cause disease? 5 ways example for each?

- destruction of host cells e.g. Polio - modification of host cell e.g. HIV? - Over-reactivity of immune system e.g. Hep B - Damage through proliferation e.g. HPV - Evasion of host defences e.g. Herpes zoster/virdae

Microbiology: Varicella and shingles? caused by what virus?

``` Varicella zoster virus chickenpox in early life (varicella) Shingles later (herpes zoster) ```

Microbiology: Protozoa is a..? Classes? (4)

Single celled eukaryote Amoeboids - pseudopodia Ciliates - cilia movement Sporozoa – non-motile Flagellates – flagella

Microbiology: Geography! African protozoa? South/Central american protozoa? Protozoa of poverty (asia, africa, south america)

African Trypanosomiasis 'Sleeping sickness' - Tsetse fly American Trypanosomiasis 'chagas disease' - Triatomine bug Leishmaniasis - female sand fly

Microbiology: Toxoplasma gondi infection? Typical sign? Pregnancy problem?

Toxoplasmosis Ring enhancing lesion on CT scan Foetus can develop retinal defects

Microbiology: Which Malaria strains have Dormant Human Liver Stages? how long until relapse?

P. vivax and P. ovale Relapse in weeks to years later

Microbiology: Malaria life cycle main stages?

``` Injection of sporozites Human liver stages leadsing to merozoite release (Schizont/Hypnozoites certain strains) Asexual blood cycle Production of gametocytes Mosquito blood meal Vector stages Re-injection ```

Microbiology: Blood stage - asexual blood cycle?

``` Merozoites from hepatocytes/Erythrocytes (schizont) enter Erythrocytes Immature trophozoite Mature trophozoite Schizont formation Schizont rupture Cycle restarts ```

Microbiology: Malaria treatment

Antimalarials: Quinine, Doxycyclin Primaquine - eliminates hypozoites in liver in P. vivax and P. ovale

``` Microbiology: Define: Pathogenicity Infectivity Virulence Invasiveness ```

Pathogenicity - the disease producing capability of a pathogen Infectivity - the ability to become established in the host Virulence - the ability to cause harm once established Invasiveness -

Microbiology: Viral infection Humoral response effectors Cell mediated response

Humoral: Antibodies: Block viral binding (IgA), opsonization of virus, agglutination, neutralisation Complement: Lysis, Opsonization (C3b) Cell mediated: IFN - antiviral NK cells + macrophages - ADCC Antibody dependent cellular cytotoxicity

Microbiology: What are adhesins Biofilms

adhesins help bacteria bind to mucosal surfaces Biofilms - bacteria secrete extracellular polymeric substance which allows them to stick on surfaces e.g. catheter

Microbiology: 2 stages of infection? What mediates each stage?

Blood stage = humoral immunity Tissue stage = cell mediated immunity

Microbiology: Eosinophils are associated with which type of infectioN? Which interleukin?

Eosinophils = parasitic infections IL-5

Microbiology: ``` Antibiotic targets with example: Beta lactams? Glycopeptides? Aminoflycosides? Tetracylcins? Macrolides? ```

Beta lactams - cell wall synthesis e.g. penicillins/aminopenicillins (amoxicillin) Glycopeptides - Protein synthesis e.g. Vancomycin Aminoglycosides - Protein synthesis e.g. Gentamycin Tetracylcins - Protein synthesis e.g. Doxycylin Macrolides - protein synthesis e.g. erythromycin, clarithromycin

Microbiology: Mycobacteria which stain? Mycobacteria OWA?

Mycobacteria = Ziehl Neelsen stain "acid fast bacilli"

Microbiology: Characteristics of mycobacteria

``` Aerobic Lipid rich cell wall SLOW growing (insidious) Can't use gram stains Granulomas Dormancy ```

Microbiology: Mycobacterial disease immunology Describe process

Phagocytosed by macrophages Mycobacteria resistant to phagolysosomal killing Antigens presented to T-cells SIEGE to mycobacteria = granulomas Mycobacteria then reduce metabolism to survive - dormancy

Microbiology: HIV phases

Acute primary infection Asymptomatic phase (years) Early symptomatic HIV "AIDs related complex" AIDS - immune deficiency CD4+ <200

Microbiology: Marker of progression in HIV? (2)

Viral load | CD4+ T-cell count

Microbiology: AIDS infection phase = how many CD4+ cell count

<200 CD4+

Microbiology: Steps of HIV replication? (9)

``` HIV replication: Attachment Entry Uncoating Reverse transcription of vRNA Genome integration Transcription of viral DNA Splicing of mRNA Assembly of new virions Budding ```

Microbiology: HIV evolved from? CD4 or CD8 T-cell replication? Which receptors allow binding?

HIV-1 is evolved from simian immunodeficiency virus in chimpanzees CD4+ T-cells due to CD4 and CCR5 receptors

Microbiology: Varicella Zoster virus Primary infection? Secondary infection?

Primary infection = Varicella "chickenpox" Secondary infection = Herpes Zoster shingles

Microbiology: Herpes viruses demonstrate... Hide where? Reactivation characteristic?

Dormancy Viral dormancy in dorsal root or cerebral ganglion Reactivation due to immunocompromisation and restricted to one dermatome usually