L7 Aerobic +ve pathogens Flashcards
what are the groups of gram positive bacteria
firmicutes
actinobacteria
what are firmicutes characterised by
low GC
what are actinobacteria characterised by
high GC
what is the ‘respiration’ of staphylococci
facultative anaerobe
are staphylococci motile
no
what are the diagnostic tests for staphylococci
catalase positive coagulase positive(s. auerus) others are negative
what differentiates staph aureus in diagnostic tests
it is coagulase positive
where are s. aureus a normal part of flora
skin
mucosal surfaces
where are the most common sites for s.aureus to be
anterior nares, throat and groins
how does s. aureus spread
direct contact or formites (survives on dry surfaces)
what type of pathogen is s. aureus
opportunistic
where is s. aureus a risk
presence foreign body (e.g. splinter, catheter)
surgical proceudre
how is s. aureus diagnosed
selective media (e.g. salt mannitol) biochemical tests (e.g. coagulase) PCR/molecular probes
what is antibiotic resistant s. aureus called
Methicillin resistant S. aureus
what percentage of the population are carriers of s. aureus
20%
what is enterocolitis
inflammation of the digestive tract caused by s. aureus
what is empyema
collection of pus in the pleural cavity caused by s. auerus
what is pyomyositis
rare bacterial infection of skeletal muscles caused by s. aureus
what is the treatment for MRSA
vancomycin
does s. aureus have a capsule
yes
what is the capsule for in s. aureus
inhibits phagocytosis, facilitates adherence
what is protein A for in s. auerus
immune evasion factors
inhibits complement/AB function, reduce opsonisation
why does s. aureus have teichoic acids
bind fibronectin
what are the enzymes that s. aureus has
coagulase nucleuase fibrinolysin hyaluronidase lipase
what are coagulase enzymes for in s. auerus
clot plasma
what are nucleuase enzymes for in s. auerua
hydrolyse DNA
what are fibrinolysin enzymes for in s. aureus
degrade fibrin clots
what are hyaluronidase enzymes for in s. aureus
degrade hyaluronic acid
what are lipase enzymes for in s. aureus
degrade lipids
where is s.epidermis a normal commensal
skin
gut
respiratory tract
what pathogen is s. epidermis
opportunistic
where does s. epidermis colonise
implants as a biofilm
why is s. epidermis hard to treat
often resistant to most anti‑staphylocccal agents: methicillin-resistant S. epidermidis (MRSE)
produce a biofilm - glycocalyx
what is the ‘respiration’ of streptococcus and enterococcus
mainly facultative anaerobes
what is capnophilic
some strep and entrococcus need some co2 for growth
are strep and entrococcus motile
no
what morphology are strep and enterococcus found in
pairs or chains
what is the catalase for strep and enterococcus
negative
what do strep and enterococcus ferment carbohydrates into
lactic acid
how many strep species are there
> 100
how many enterococcus species are there
> 50
what are the schemes to classify strep
serologic properties - lancefield groupings (A, B, C, F, G)
haemolytic patterns:
biochemical (physiological) properties
types of hemolysis
- complete (beta [β]) haemolysis
- incomplete (alpha [α]) haemolysis
- no (gamma [γ]) haemolysis
how are beta haemolytic strep categorised
lancefield grouping (A, B, C, F, G)
how are alpha and gamma haemolytic strep categorised
collectively termed viridans streptococci
what is GAS
group A strep
what is s. pyogenes
GAS
where is s. pyogenes present
nasopharynx of healthy adults and children: strep throat
what caused scarlet fever
s. pyogenes
how does s. pyogenes spread
from person to person through respiratory droplets
how are s. pyogenes grouped
subdivided into Griffith types based on serology of three surface protein antigens: M, R, T
what is the virulent strains of s. pyogenes
with M protein
why is M protein virulent in s. pyogenes
inhibits phagocytosis
what is the treatment for s. pyogenes
penicillin and amoxicillin
no vaccine
what is the presumptive identification method for s. pyogenes
PYR and bacitracin test
what infections does s. pyogenes cause
suppurative
non suppurative
what are the suppurative infections that s. pyogenes causes
pharyngitis & tonsillitis scarlet fever necrotizing fasciitis (“flesh-eating disease”) otitis media pneumonia streptococcal TSS
what are the non suppurative infections s. pyogenes causes
rheumatic fever
acute glomerulonephritis
how is scarlet fever seen physically
rash and strawberry tongue
what are the virulence factors of s.pyogenes - structural
capsule (some strains)
M proteins
teichoic acids
what are capsules for in s. pyogenes
inhibits phagocytosis, facilitates adherence
what are M proteins for in s. pyogenes
anti-phagocytic, prevents opsonisation
what are teichoic acids for in s. pyogenes
bind fibronectin
what are s. agalactiae
group B strep
what is GBS
group B strep
where does s. agalactiae colonies
lower GI tract
genitourinary tract
what is the haemolysis of s. agalactiae
beta
1-2%strains none
what does s. agalactiae cause in newborns
meningitis
pneumonia
sepsis
why does s. agalactiae affect newborns
absence of maternal protective AB
low complement levels
what does s. agalactiae cause in adults
bacteremia, pneumonia
bone and joint infections
skin and soft tissue infections
pregnant women: urinary tract infections
what bacterias work together to give a bigger haemolysis
s. aureus and GBS
s. aureus makes another protein that synergistically works with GBS = bigger clearing
what is the haemolysis of s. pneumoniae
alpha
can be beta if grown anaerobically
what do the virulent s. pneumoniae carry
capsule
where does s. pneumoniae colonise
upper respiratory tract
mouth
pharynx
what does s. pneumoniae cause
pneumonia
meningitis
otitis media
sinusitis
why is s. pneumoniae difficult to isolate
fastidious
how is s. pneumoniae diagnosed
sensitive to optochin, ferments inulin, and lysed by bile salts
what is the treatment for s. pneumoniae
vaccines available: PCV and PPV in the UK
how many species of bacillus are there
~300
does bacillus species make spores
endospore forming
what is the ‘respiration’ of bacillus
aerobic or facultative anaerobe
what is the shape of bacillus
rod
are bacilli motile
some
which are the pathogenic bacillus
b. cereus
where is b. cereus present
ubiquitous - all environments
what pathogen is b. cereus
opportunisitic
what does b. cereus cause
vomiting disease – toxin in food
diarrheal disease – GI tract infection
ocular infections, complete eye loss in 48 h
intravenous catheter - sepsis
severe pneumonia (rare; after acquiring B. anthracis toxin genes)
how do you get infected by b.cereus
food poisoning (gastroenteritis)
what are the vomiting toxins of b. cereus
heat stable enterotoxin
what are the diarrhoea disease toxins of b. cereus
heat liable enterotoxin
what are the eye destruction toxins of b. cereus
necrotic toxin (heat-labile)
cerolysin (alpha haemolysin)
phospholipase C
what shape is b. anthracis
large vegetative cell
is b. anthracis motile
no
what is the characteristic growth of b. anthracis
medusa head colonies
what encodes the toxin and capsule for b.anthracis
plasmid encoded
what does b. anthracis cause
anthrax
how does b. anthracis infect
humans infected through contaminated animals/animal products (also drug abusers – heroin injection)
inoculation (95%), ingestion (very rare), inhalation
do b. anthracis have spores
yes
survive for years in soil
what is the treatment for b. anthracis
vaccines
how is b. anthracis detected
direct fluorescent antibody test
what are the virulence factors of b. anthracis
capsule (poly D-glutamate)
lethal toxin
edema toxin
what is the lethal toxin of b. anthracis made of
protective antigen + lethal factor
what is the edema toxin of b. anthracis made of
protective antigen + edema factor
types of anthrax
cutaneous
gastrointestinal
inhalation
what does listeria monocytogenes cause
listeriosis
is listeria monocytogenes motile
tumbling motility at 25 degrees
what shape are listeria monocytogenes
short rods
what is the haemolytic activity of listeria monocytogenes
beta
how is listeria monocytogenes acquired
contaminated food: soft cheese, milk, undercooked meat, unwashed raw vegetable
what temp ph does listeria monocytogenes grow at
wide pH and temperature range (1 – 45 °C; fridge!)
where is listeria monocytogenes present
widely distributed in nature restricted to
neonatal disease
pregnant women
healthy adults
what is the effect of early onset neonatal disease by listeria monocytogenes
spontaneous abortion
how is early onset neonatal disease by listeria monocytogenes trasnmitted
via placenta in uterus
what is the effect of late onset neonatal disease by listeria monocytogenes
meningitis, septicaemia
what is the effect of listeria monocytogenes on pregnant women/immune defect patients
bacteraemia
meningitis
what is the effect of listeria monocytogenes on healthy adults
mild influenza-like illness, gastrointestinal symptoms, often asymptomatic = listeriosis
what is the group for gram positive bacteria with high GC
actinobacteria
what is the shape of Corynebacterium diphtheriae
club
is Corynebacterium diphtheriae motile
no
is Corynebacterium diphtheriae catalase +/-
positive
what is in the cell wall of Corynebacterium diphtheriae
mycolic acid
what is the ‘respiration’ of Corynebacterium diphtheriae
facultative anaerobe
what are the hosts of Corynebacterium diphtheriae
only humans
what does Corynebacterium diphtheriae cause
diphtheria
- respiratory
- cutaneous (less servere)
what are the diphtheria toxins
A-B exotoxin
what does A-B exotoxin do
inhibit protein synthesis
what is the diphtheria toxin encoded by
lysogenic phage (b-phage)
what is the treatment for diphtheria
anti-toxin and antibiotics; prevention through vaccination (now part of 5 component vaccine) & contact tracing
how many species of mycobacterium are there
> 100
are mycobacterium motile
no
what is the ‘respiration’ of mycobacterium
aerobic
what are the pathogenic mycobacterium
Mycobacterium tuberculosis
Mycobacterium leprae: lepra
Mycobacterium africanum
Mycobacterium bovis
what is different in mycobacterium
Highly complex cell wall with mycolic acid = acid fast stain
what is the growth of mycobacterium
slow growing
what does the cell wall of mycobaterium include
lipid-rich
high % mycolic acid
hydrophobic
what is the cell wall of mycobacterium like with disinfectants/antibiotics
resistant
how are acid fast organisms characterised
hydrophobic, wax-like, nearly impermeable cell walls
what does mycobacterium tuberculosis cause
tuberculosis
what is tuberculosis
infects lungs but can disseminate to other sites
what type of pathogen is mycobacterium tuberculosis
intracellular - replicates in unactivated alveolar macrophages
what is the mycobacterium tuberculosis infection like
can remain dormant and establish lifelong infection
why does mycobacterium tuberculosis cause disease
primarily due to host response (no myco-bacterial toxin/enzyme known to destruct tissue)
where is mycobacterium tuberculosis present
humans are only natural reservoir: 1/3 of world population infected
how is mycobacterium tuberculosis spread
inhalation of infectious aerosols
how is mycobacterium tuberculosis diagnosed
molecular probes, tuberculin skin test (with proteins from cell wall)
QuantiFERON-TB (blood) test: ELISA-based interferon gamma release assay
what is the RBC virulence factor that strep pyogenes group A has
Streptolysin S
examples of actinobacteria (high GC)
Corynebacterium
Mycobacterium