Microbiology: Systemic Bacteriology Flashcards
how are micro-organisms classified
- appearance
- growth requirements
- enzyme/metabolic tests
- molecular tests
how are micro-organisms classified on their appearance
shape, size, structure, cell wall (gm-ve/+ve), arrangement
how are organisms classified on their growth requirements
- aerobic/anaerobic
- requirements for blood proteins
- sensitivity to inhibitory agents
what enzyme/metabolic tests can be carried out on a micro-organism
- coagulase test
- haemolysis
- catalase test
- biochem profiling
what molecular tests can be carried out on a micro-organism
- DNA sequencing
- protein profiling
- immunological tests
what microscopic identifications are used
- staining (gm stains, Ziehl Neilson, fluorochromes)
- structures
- shape, group, sizing
- pure culture or polymorph
what are the common shapes of bacterial structures and their names
- cocci - spheres
- bacilli - rods
- spiral-shaped
what is the division plane of diplococcus
1 plane, 2 spheres
what is the division plane of sterptococcus
1 plane into chains
what is the division plane of staphylococcus
3 planes, clumps
what do bacillus duplicate into
chains
what are bacillus called
vibrio
are vibrio gm -ve or gm +ve
gm -ve
what are the two types of spiral shaped bacteria
- spirillum, rigid
- spirochaete, flexible
what are spores resistant to
chemical and physical challenge
what are spores
condensed DNA encased in a shall with no active protein processes
describe how spores react to antibiotics
they dont
what colour stain does
- gm -ve
- gm +ve
bacteria go
+ve - purple
-ve - pink
what organisms dont stain well with gm stain
myobacterium TB and treponema pallidum
what are the growth requirements of - aerobic - obligate aerobes - obligate anaerobes - facultative anaerobes - capnophilic organisms
- grow in O2
- need O2
- killed by O2
- tolerate O2
- prefer high CO2 levels
what is selective media
media that selects the growth of different bacteria with the presence of specific substances permitting the growth of one organism over another
what is differential media
media that has chemicals incorporated that produces visible changes in colonies that allow identification
describe the different types of haemolysis
- alpha, partial - greening
- beta, full - yellow
- gamma, none
what is metabolic profiling
utilisation of carbon/amino acids
what does a coagulase test look for and what bacterium
clot plasma
- S. Aureus gm+ve
what does a catalse test for
the H2O2 -> 2H2O + O2
what bacterium does a lipid hydrolysis test look for
clostrida species
what reaction does a urease test look for
urea -> ammonia + CO2
what do serological tests look for
host immune response and antibodies (i.e. presence of a specific IgM ab)
what can serological tests detect
- rapid virus detection
- specific bacteria serotypes
what types of DNA technology is available
- PCR
- ribosome 16S RNA
- MLST
- MALDITOF
what is MLST
multi-licus sequence typing - genome sequencing
what is MALDITOF
matrix-assoc. laser desorption ionisation time of flight - mass spec
what does MALDITOF do
detects spectrum of proteins from samples
what bacterium is MALDITOF bad for
staphylococci and streptococci
what microbio tests are available
- pus swab
- mucous sample
- blood/urine/faeces culture
- bloods
what are exogenous bacteria
not part of normal flora
describe the parasitic life cycle
- pathogen enters host from reservoir of pathogens or by host via direct contact
- the parasite the colonies and invades, evading host defences, it multiplies/completes its life cycle and exits host after causing damage
- it then is spread going into reservoir or directly into host
virulence
capacity of pathogen to cause damage
pathogen
harmful organisms that causes pathology
commensal/mutualism/symbiotic
endogenous organism thats part of normal flora, often mutualistic
opportunistic pathogen
organism that causes infection when opportunity/change in natural immunity arises
contaminant
organism accidentally grown in culture
in what type of people do fungal infections occur
immunocompromised
what type of diseases to protozoans cause
malaria, GI infections, toxoplasma
what are the 2 types of pathogenic gm-ve diplococci
- Neisseria meningitis
- Neisseria gonorrhoea
what pathogenic bacteria are associated with the GI tract
- salmonella
- shigella
- VTEC producing E.coli -0157, 0104
what commensal bacteria are associated with the GI tract
- most E. coli forms
- klebsiellla
- enterobacteria
- proteus
coliforms
gm-ve bacilli that look like E.coli on gm film and blood cultures
in what sort of environment do coliforms best grow
aerobically but can grow anaerobically
how are coliforms differentiated
- biochem reactions
- serotyping
- O antigens
- H antigen
how can coliforms cause infection
by getting into naturally sterile site
what antibiotic is 1st line for coliform infection
gentamicin
how is coliform sepsis very bad
endotoxin is released from cell wall when the bacteria die
how do endotoxins produce a response
bind to receptors on macrophages, B cells and others stimulating acute cytokine release
describe an endotoxin membrane
gm -ve and assymetrical with LPS
describe fever production
- endotoxon antigen or LPS interacts with macrophages
- cytokines released
- cytokines travel to anterior hypothalmus
- PGE released and body thermal set point increased
- body initiates cold response
- fever
- increased infection survival
what do cytokines stimulate, other than fever, in hypothlmus
adverse effects of sepsis
how can harm arise from a fever
febrile convulsions in children
what is sepsis
host response to severe infection
describe the mechanism behind sepsis
- leaky blood vessels allow fluid to be lose to tissues
- HR increased due to decreased blood vol to
- poor tissue perfusion results in blood supply to less vital organs shutting down to maintain brain blood supply
- clotting cascade activated causing clots in tiny blood vessels
how can sepsis increase haemorrhage risk
clotting factors are used up therefore less can be usedin caseof haemorrhage
4 gm +ve pathogens
- streptococci
- staphylococcus
- enterococcus
- clostridia
what type of bacteria are differentiated using haemolysis
sterpotococci
describe - alpha - beta - gamma haemolysis
- partial haemolysis, greenish discolouration, Hb in RBCs denatures
- complete haemolysis, yellow, complete lysis of Hb in RBCs
- none
what type of streptococci (in terms of haemolysis) is the most pathogenic
beta
GAS
group A streptococci
what type of haemolysis do GAS undergo
beta
infections associated with GAS
- strep pyrogens
- strep sore throat (scarlet fever)
- invasive disease - necrotising fascitis
- peurperal sepsis
describe strep pneumoniaes differentiating features
- gm +ve
- alpha haemolytic
- short chains or pairs
what bacteria is the most common cause of pneumonia and what else can this bacteria cause
- streptococcal pneumoniae
- severe meningitis
what group of non-haemolytci streptococci are the most important
enterococci
what is the most common cause of UTIs
non-haemolytic streptococci
what are VREs and where do they break out
- vancomycin-resistant enterococci
- outbreaks in hospitals
are non-haemolytci streptococci part of normal bowel flora or nah
yes
two types of staphylococci
- S. Aureus
- S. Epidermis
describe staphylococcis differentiating features
gm+ve irregular clusters, non-motic, +ve catalse, -ve oxidase, coagulase can be either, aerobe and faculative anaerobe, 15% NaCl
where does S. aureus usually stay
where does it break out
- anterior nares and perineum
- nosocomial and community
where does S. epidermis usually stay
where does it break out
- skin and mucosal membranes
- nosocomial and immunocompromised
where and who does MRSA infect
- nosomical in ICU - IV lines
- immunocompromised, elderly, burns, dialysis and surgical patients
what are S. epidermis infections associated with
foreign bodies
what is the most common skin, soft tissue, wound, bone and joint infection
S. Aureus
what type of S. aureus causes food poisoning
enterotoxin producing strains
how does S. aureus cause
- local inflam
- bacteremia
- sepsis
- multiplies at sites of acquisition
- once its in bloodstream
- disseminates to distant sites in the body
where does S. aureus cause abscesses
spleen, liver, kidney
describe clostriodes differentaiting features
- gm +ve, anaerobic bacilli
- normal flora
- spore producing
clostriodes produce spores meaning what
they can survive outsidethe body for months
what type of clostriodes produce enterotoxins
- C. difficile
- C. perfringens
- C. tetani
what infection is C. difficile associated with
antibiotic associated diarrhoea in the elderly
what infection is C. perfringens associated with
gangrene
what infection is C. tetani associated with
tetanus
what can enterotoxin producing clostriodes cause
severe tissue damage
what causes pseudomembranous colitis
C. difficule
what is the link of C. difficile to antibiotic therapy
proliferates in absence of normal bowel flora
