Microbiology Flashcards
What is a pathogen?
An organism that causes or is capable of causing disease
What is a commensal?
an organism which colonises the host but causes no disease in normal circumstances
What is an opportunistic pathogen?
A microbe which only causes diseases if its host organism is compromised
Define pathogenicity/ virulence
The degree to which a given organism is pathogenic
Does microbacteria stain with gram?
No
What is the stain of gram positive
Purple
What is the stain of gram negative
Red
Name G+ coccus chain bacteria family
Streptococcus
Name G+ coccus cluster bacteria family
Staphylococcus
Name a G+ coccus pair bacteria family
Enterococcus
What type of bacteria is staphlococcus?
Gram postive coccus cluster
What type of bacteria is streptococcus?
Gram positive cocus chains
What type of bacteria is enterococcus?
G+ coccus pair
What type of bacteia is s. pyogenes?
Group A, beta haemolytic streptococci (G+ cocci chains)
What type of bacteria is s. pneuomiae
G+ streptococcus (coccus chain), alpha haemolysis- optochin sensitive
What type of bacteria is s. aureus?
G+ staphlococcus (coccus cluster), coagulase test positive
What is the test used to distinguis between staphlococcus classes
Coagulase test
Name the bacteria which is G+, cluster coccus and is coagulase test positve
S. aureus
- Impetigo, endocarditisis and septiciemia
Name 2 bacteria which are G+, cluster coccus and are coagulase test negative
S. epidermidis
S. saprophyticus
Is S. aureus coagulase positive or negative?
Positive
Which test is used to differentiate between streptococcus members
Haeomolysis on blood agar
What is the colour of beta haemolysis of streptococcus and an example
It is complete lysis forming yellow/ transparent agar
S. pyogenes
What is the colour of alpha haemolysis of streptococcus
It is partial lysis (greening) and is dark green on agar plate
Is S. pneumoniae optochin test sensitive or resistent
Sensitive
Give an example of alpha- haemolysis of streptococcus
Viridans strept
S. pneuomoniae
Is S. pnueomoniae staphlococcus or streptococcus?
Streptococcus
Name 3 types of bacteria in the staphlococcus family
S. aureus
S. epidermidis
S. saprophyticus
Name 2 members of viridans strep (optochin resistant)
S. sanguinis and S. oralis in infective endocarditis
Name 4 types of bacteria in the streptococcus family
S. pyogenes - alpha haemolysis a antigen group
S. agalactiae - alpha haemolysis b antigen group
S. pneuomoniae - optochin sensitive -beta haemolysis
S. sanguinis - viridans strep - b haemolysis
S. oralis - viridans strep - b haemolysis
Name 3 types of G+ aerobic bacilli bacteria
- Listeria monocytogenes
- Bacillus anthracis
- Coryne bacterium diphtheriae
Name 3 types of G+ anaerobic bacilli bacteria
Clostridia
1. C. difficile
2. C. tetani
3. C. botulinum
What type of bacteria is N. gonorrhoea and N. menigitidis?
Gram negitive cocci
Give another example of gram negative coccus
N. gonorrhoea and N. menigitidis
M.catarrhalis
Is shingella lactose or non-lactose fermenting
non-lactose fermenting
Wht test is used to distinguis between salmonella and shingella
serum H antigen (shingella is H-)
What type of bacteria is E.coli?
G-, lactose fermenting bacteria with simple growth conditons bacillus aerobic
What type of bacteria is K. pnuemoniae?
G-, lactose fermenting bacteria with simple growth conditions bacillus
Give an example of lactose fermenting gram negative bacillus
E. coli and K. pneuomonia
What type of bacteria is salmonella
Gram negative, aerobic, non-lactose fermenting bacillus aerobic
What type of agar plate is used for parvobacteria and H. pylori
Choc agar
What is parvobacteria and give 2 examples?
G-, aeorbic bacilli with fastidious growth condions
haemophillic influenza, brucella, campylobacter jejuni, bordatella pertussus, legionella pnuemophillia
Give a specific example of salmonella bacteria
S. enterica
S. typhi
S. paratyphi
Give an example of Shingella
S. dysenteriae
What colour is lactose fermenting bacteria on MacConkey
Pink - e.coli
What type of bacteria is H. pylori
G-, bacillus with fastidious growth conditions - aerobic
What colour is non-lactose fermenting bacteria on MacConkey agar
Pale pink- salmonella, shingella, p. mirabilis
What test is used for mycobacteria?
Ziehl-Neelsen test
Name differences between G- and G+ bacteria
G+: thick peptidoglycan
G- : thin peptidoglycan
G+: no LPS
G-: LPS
G+ exotoxin
G- endotoxin
Give an example of a mycobacteria
m. tubercolosis
m. leprae
Summarise properties of mycobacteria
Slow growing, aerobic, acid fast, non-spore forming, non motile bacilli
What stain is used for mycobacteria
Ziehl-Neelson stain
What is the positve staining result for mycobacteria
Red with ziehl-neelson stain (Alcohol and acid fast bacteria)
What makes mycobacteria resistant to gram staining
High lipid content in cell wall (mycolic acid)
What is the general speed onset of diseases caused by mycobacteria?
Gradual onset due to slow =growing bacterium
What are the diagnostic tests used for TB
-PCR nucleic acid test: rapid, from sputum analysis
-Tuberculin skin test: tests the immune response (t memory cells) as a diagnostic test
Differences between yeast and mould
Yeast: small, unicellular, reproduce asexually by budding
Mould: multicellular hyphae, reproduce via spores
Example of a yeast and of a mould
Yeast: candidiasis (c. glabrata = thrush)
Mould: aspergillus
3 examples of fungal infection
athletes foot (tinea pedia)
vulvovaginal candidiasis
nappy rash
Main class of treatment for fungal infections
Azoles: eg fluconazole
Define a virus
Is an infectious, obligate intracellular parasite
(completely dependent on living cells for their replication and existance)
What type of bacteria is staphlococcus?
G+ coccus clusters
What type of bacteia is s. pyogenes?
G+ streptococcus (coccus chains) aerobic beta haemolytic antigen A
What are the properties of a virus?
No organelles, DNA AND RNA, cell wall
Not alive
Dependent on host cell
Genetic material covered by protein capsule
How are virus’ genetic material stored?
In protein capsule/ membrane
What is the name given to viruses outside their host cells?
Virions
Describe the process of viral replication
- Attachement onto a specific receptor
- Entry into cell
- Host cell/ virus interaction and replication
- Translation of viral RNA
- Virion assembly
- Release of new virus particles
Name the 5 ways in which a virus can cause disease and an example for each
Direct destruction of host cell - HIV, polio
Over-reaction of immune system - rotavirus
Modification of immune system - Het B
Evasion of host defences - varicella zoster virus
Damage through cell proliferation- HPV
What is the primary infection and reactivation of varicella zoster virus?
PI- chicken pox
2nd- shingles/ herpes zoster
What does epstien barr virus cause?
mononucleosis (glandular fever)
How many viruses are apart of the verpesviridae family?
8 herpesviruses
What does s.pyogenes cause?
Scarlet fever-
Strep throart
Impetigo
What is primary vaccine failure?
Persone doesnt develop immunity from vaccine
What is seconday vaccine failure?
Person initially develops immunity but it wanes after time
Give examples of notifiable diseases
Rubella, mumps, measels, diphtheria, leprosy, malaria
What is the Ddx to epstein barr virus?
s. pyogenes -> white/ yellow pusulent over tonsils
How to diagnose EBV?
black charcoal swab- exclude s. pyogenes
FBC- atypical lymphocytes
EBV serology - elisa
and PCR
What are the 2 main techniques used to diagnose viruses?
PCR and serology (eg elisa/ immunofluorescent)
What colour is the diagnostic swab for bacteria and viruses
black and green respectively
What are antibiotics?
Drugs that work by bindign to a target site in bacteria
What are the main 4 classes of antibiotics?
Cell wall synthesis
Nucleic acid synthesis
Protein synthesis
Folate synthesis
What are the 2 groups of cell wall synthesis antibiotics?
Beta lactans and glycopeptides
Give examples of beta lactan antibiotics
penicillin
- flucloxacillin
- amoxicillin
- co-amoxiclav
cephalosporins
-cefuroxime
- cefotaxime
carbapenems (meropenem)
What is vancomycin?
glycopeptide cell wall synthesis AB
Uses: G+ bacteria w pen allergy or resistance/ MRSA/ enterococci
What is vancomycin?
glycopeptide cell wall synthesis AB
Uses: G+ bacteria w pen allergy or resistance/ MRSA/ enterococci
What is the antibiotic given for s. aureus?
Flucloxacillin
What is the antibiotic given for strep throat and which bacteria may cause this
PO (oral) penicillin
Group A, C, G strep
What antibiotic is given for pneumonia (s. pneumoniae)
oral amoxicillin
(erythromycin or clarithromycin if severe)
What is MRSA and which AB can be given for it?
methicillin resistant staphylococcus aureus (flucoxacillin)
- give vancomycin IV
What is gentamycin used for
g- bacteria, uti
What bacteria can cause UTI and which AB for it?
E.coli, klebsella, enterobacteria proteua
trimethoprim
(nitrofurantoin for lower UTI)
Which AB target G- bacteria
gentamycin, ciprofloxacin, trimethoprim, nitrofurantoin
Does G+/- bacteria have a thick cell wall
G+
What are the 2 classes of AB resistance?
Intrinsic and acquired
How may AB resistance be acquired?
Spontaneous mutation and horizontal gene transfer
What are th 3 ways genes can be transferred in acquired AB resistance?
Conjugation - plasmid DNA transfer
Transformation
Transduction
What are examples of G + and - AB resistance?
G+
- MRSA (methocillin resistant staph aureus) -> vancomycin
- VRE (vancomycin resistance enerococci) -> penicillins