MicroB Flashcards
what bacterials grow as diplococci?
- strep pneumoniae (gram pos cocci)
- Neisseria spp. (gram neg cocci)
out of all the streps, which is the one that is not part of normal flora
strep pneumo (group A)
out of all the staphs, which is the coagulase positive one?
staph aureus - it is the only coagulase positive staph
are all the staphs part of normal flora?
yes! staph aureus found in anterior nares of 30% of people; staph saprophytic found part of vagina
what is a group A beta haemolytic gram pos cocci?
strep pyogenes
what type of haemolytic bacteria is strep pneumonia?
alpha haemolytic
what is the test for alpha haemolytic bacteria?
green tinge on blood agar
what is the virulence for strep pneumo?
anti-phagocytic capsule with pneumolysin
what can strep pneumo cause?
Young: otitis media and URTI Enter: endocarditis P: pneumonia M: meningitis S: septicemia
how to test for strep pneumo?
culture, gram stain, urine antigen test
how to treat strep pneumo?
benzylpenicillin or ceftriaxone if meningitis
is there a vaccine for strep pneumo?
yes - the pneumococcal vaccine which is a conjugated vaccine (compulsory for kids in sg)
what can strep viridans cause?
subacute endocarditis secondary to septicemia
dental caries
what type of haemolytic bacteria is strep viridans?
alpha haemolytic (like strep pneumo)
it is a group A alpha haemolytic cocci
what type of hemolytic bacteria is strep pyogenes?
beta haemolytic
it is the only group A beta haemolytic bacteria
what does it mean to be beta haemolytic?
leaves a yellow tinge after breaking down the RBC on blood agar
VS alpha haemolytic which leaves a green stain
what is the virulence of strep pyogenes?
streptolysin O and M protein
what can strep pyogenes cause?
P: pharyngitis with sequelae of acute rheumatic fever
S: skin and soft tissue infections (e.g. scalded skin syndrome, erysipelas, bullies impetigo)
S: Scarlett fever
how to treat strep pyogenes?
benzylpenicillin
what is an example of group B strep?
strep agalactiae
what type of haemolytic bacteria is strep agalactiae?
beta haemolytic
what is special about strep agalactiae?
there is vaginal carriage in 30% of women, 30% of the time
why is the 30%/30% thing special about strep agalactiae?
it means it is not persistent and can be cleared by antibiotics
what is the treatment of strep agalactiae?
benzylpenicillin
what is a group D strep?
enterococcus spp.
is enterococcus part of the normal flora?
yes, its part of the GIT
what are the presentations of enterococcus?
E: endocarditis
N: nosocomial infections
U: UTI
how to treat enterococcus? (note that its a special gram pos cocci)
any beta lactam that is not cephalosporin
or vancomycin
how does staph aureus grow?
yellow clusters on blood agar
what is the virulence of staph aureus?
- alpha toxin
- toxic shock syndrome -1 toxin
- enterotoxin
- epidermolytic toxins
what does staph aureus cause?
mnemonic: it’s dangerous so must SET BP Fast
S: skin and soft tissue infections
E: endocarditis
T: toxic shock syndrome
B: bone infections
P: pneumonia secondary to influenza
Fast: food poisoning
how to treat staph aureus?
cloxacillin or 5th gen cephalosporin (ceftaroline)
vancomycin for MRSA
what type of coagulase bacteria is staph saprophyticus?
coagulase negative
what do coagulase negative bacteria usually cause?
usually the ones contaminating blood cultures, prosthetics and line infections
what does staph sapro cause?
UTI in young, sexually active women
what type of bacteria is moraxella catarrhalis?
gram neg cocci
what does moraxella catarrhalis cause?
opportunistic chest infections like bronchopneumonia
what is special about the way Neisseria grows?
grows as diplococci, just like strep pneumo
on which medium does Neisseria grow on?
need charcoal medium for transport and to be grown in a Thayer-martin medium with rich CO2
what does Neisseria gonorrhoea cause?
males: acute urethritis
females: asymptomatic carriage or PID
neonates: ophthalmia neonatorum
blood: disseminated gonorrhea
how to treat Neisseria gonorrhoea
ceftriaxone
azithromycin if resistant
do we have prophylactic treatment for Neisseria gonorrhoea and if so, what is it?
silver nitrate eyedrops for neonates
what is special about the virulence of Neisseria meningitidis?
it was 4 subtypes; type A, C, Y and W135
what does Neisseria meningitidis present as?
meningitis
meningococcemia
unique: waterhouse-friderichsen syndrome (adrenal gland failure)
what are the general signs of meningitis?
fever, neck stiffness, headache, non-specific macular rash
what are the signs of meningicoccemia?
non-blanching rash which results in a positive tumbler test
what does a non-blanching rash mean?
it means there is inflammation that makes the blood vessels so leaky, that the blood has entered the epidermal layers
how to treat Neisseria meningitidis
ceftriaxone (clears throat carriage)
benzylpenicillin (does not clear throat carriage)
is there a vaccine for n. meningitidis?
yes, the meningococcal vaccine that is conjugated
compulsory for kids in sg
list the important gram positive rods (aerobic and anaerobic)
aerobic: listeria monocytogenes corynebacterium diphtheria bacillus cereus bacillus anthracis
anaerobic: clostridium tetani clostridium botulinum clostridium difficile clostridium perfringens
list the important gram negative rods (4 main types)
enterobacteriaceae: E. coli klebsiella proteus spp shigella dysenteriae salmonella type salmonella enteritidis
pseudomonads:
burkholderia pseudomallei
pseudomonas aeruginosa
vibrio:
vibrio cholerase
vibrio vulnificus
fastidious rods:
legionella pneumophila
haemophilus influenzae
what does listeria monocytogenes cause?
neonatal infections
meningitis in immunocompromised
how to treat listeria monocytogenes?
ampicillin
NOTE: resistant to all cephalosporins like enterococcus
what does corynebacterium diphtheria grow on?
tinsdale medium and looks like Chinese characters
what is the virulence of corynebacterium diphtheria?
exotoxin - diphtheria toxin
what does corynebacterium diphtheria cause?
URTI
bull neck appearance
myocarditis (the cause of death)
is there a vaccine for corynebacterium diphtheria?
yes there is and its compulsory for children (but you inject the bacteria without the toxin)
what is special about the treatment about corynebacterium diphtheria?
use an anti-serum and not some antibiotic
what does bacillus cereus cause?
food poisoning that is self-limiting
what does bacillus anthracis cause?
causes anthrax which results in black ulcers all over
how to treat bacillus anthracis?
benzylpenicillin
ciprofloxacin
what is the virulence of clostridium tetani?
tetanoplasmin toxin - blocks the inhibitory signals of LMN
what does clostridium tetani cause?
spastic paralysis
how to treat clostridium tetani?
human tetanus immunoglobulin
what is the virulence of clostridium botulinum?
preformed botulinum toxin that blocks the NMJ junction
what does clostridium botulinum cause?
flaccid paralysis
how to treat clostridium botulinum?
antiserum
what is the virulence of clostridium difficile?
alpha toxin
what does clostridium difficile cause?
c. diff associated colitis
how to treat clostridium difficile?
metronidazole
oral vancomycin
what is the virulence of clostridium perfringens?
lithicinase toxin
what does clostridium perfringens cause?
gas gangrene
how to treat clostridium perfringens?
penicillin
what is special about all the clostridiums?
they all have toxins as virulence and the first two have special treatments
what are the lactose fermenters of the enterobacteriaceae group?
E. coli and klebsiella (the only 2)
what are the different types of e.coli?
ETEC: enterotoxigenic
EPEC: enteropathogenic
EHEC: enterohemorrhagic (O157) is most common
VTEC: shigatoxin-producing
UPEC: uropathogenic
how to treat e.coli?
ceftriaxone, cipro, cotrimox, nitrofurantoin
what does klebsiella spp. cause?
UTI, liver abscess, pneumonia (caused by klebsiella pneumoniae)
what does proteus spp cause?
UTI
what does shigella dysenteriae cause?
dysentry
what does salmonella typhi cause
typhoid fever (this differs from typhus! which is caused of rickettsia typhi)
what does salmonella enteritidis cause
common bacterial cause of gastroenteritis
what is special about the way pseudomonas aeruginosa grows?
it grows green on blood agar
what does pseudomonas aeruginosa cause?
contact lens keratitis
pneumonia or other nosocomial infections
how to treat pseudomonas aeruginosa?
like e.coli, it is very extensive
common treatments: ceftriaxone and cipro
what is special about the way burkholderia pseudomallei grows?
grows as wrinkled colonies
what does burkholderia pseudomallei cause?
melioidosis: fever, pneumonia, liver abscess
how to treat burkholderia pseudomallei?
D: doxycycline
C: coamox
C: cotrimox
C: chloramphenicol
what is special about the way vibrio cholerase grows?
grows in yellow colonies
what is the virulence of vibrio cholerase?
cholerase toxin
what does vibrio cholerase cause?
cholera
the O1 type causes outbreaks
how to treat vibrio cholerase?
cipro and rehydration
what does vibrio vulnificus cause?
self-limiting watery diarrhea
what does legionella pneumophila cause?
pontiac fever legionnaires disease (non-productive pneumonia)
how to diagnose legionella pneumophila?
since its a non-productive cough, can use a bronchoalveolar lavage to get sputum samples
can also get urine antigen test
how to treat how to diagnose legionella pneumophila?
IV erythromycin
rmb leeeee-gionella, so eeeeee-rythromycin
what does h. influenzae grow on?
chocolate agar with X and Y factors
what is the virulence of h. influenzae
like strep pneumo, its capsule is the virulence factor
what does h. influenzae cause
encapsulated and non-encapsulated diseases
encapsulated: meningitis, pneumonia post influenza
non-encapsulated: URTI
how to treat h. influenzae?
ceftriaxone
what are the important mycoplasma/chlamydia bacteria?
- mycoplasma pneumoniae
- chlamydia psittaci
- chlamydia trachomatis
- chlamydia pneumoniae
what does m. pneumo cause?
“walking pneumonia” in adults = essentially atypical pneumonia
paroxysmal cough in children
how to treat m. pneumo?
any protein synthesis inhibitor (TAG/MCL)
what does c. psittaci cause?
atypical pneumonia
what does c. trachomatis cause?
it essentially is the STD, but different variants present differently
type A-B: trachoma (eye blindness)
type D-K: inflammatory diseases such as urethritis
type L1-L3: genital warts
what does c. pneumoniae cause?
atypical pneumonia
what are the important intracellular obligate parasites?
just rickettsia, so there’s:
- rickettsia typhi
- rickettsia rickettsii
- rickettsia prowazeki
what does rickettsia typhi cause?
typhus (different from typhoid fever caused by salmonella typhi)
what does rickettsia prowazeki cause?
typhus too (abdominal pain, fever, headache, general malaise)
what does rickettsia rickettsii cause?
Rocky Mountain fever + centripetal rash
what are the important spiral bacteria?
- treponema pallidum
- helicobacter pylori
- campylobacter jejuni
what does treponema pallidum cause? (consider its various stages - primary, secondary, late stage, latent, neonatal)
essentially syphilis
primary syphilis: chancres and enlarged lymph nodes
secondary syphilis: mucous tracks, acute meningitis, rash on palms and soles
late stage: neurosyphilis and gummatous syphilis
latent: asymptomatic with some flares
neonatal: hutchinson’s triad (eye blindness, deafness, teeth malformation)
how to diagnose treponema pallidum?
- dark illumination
- non-treponema antibody test (tp hemagglutinin test + tp particle agglutinin test)
- treponemal antibody test (VDRL + RPR)
can spiral bacteria be gram stained?
no!
what does h. pylori cause?
acute and chronic gastritis
PUD
increased risk for gastroadenocarcinoma
how to diagnose h. pylori?
fecal antigen test and urease breath test
how to treat h. pylori?
O: omeprazole (antacid)
A: amoxicillin
C: clarithromycin
what does c. jejuni cause?
gastroenteritis
how to treat c. jejuni?
erythromycin
ciprofloxacin
how to treat treponema pallidum?
penicillin (surprisingly easy)
what does primary m. tb cause?
AFB have cord factor –> are phagocytosed but survive in macrophages –> accumulation of macrophages and formation of granulomas called goon’s focus –> need a while for T cells to secrete TB-specific IFN-y to increase microbicidal effect of macrophages to attack these AFB-filled macrophages
what does secondary m. tb cause?
if there is a reinfection or reactivation of latent tb, there will be formation of caseous necrosis with cavitating granulomas
what does miliary tb cause?
hematogenous spread to other organs to cause caseous necrosis
how to diagnose tb?
- chest xray
- AFB test with ziehl-neelson stain
- Mantoux test for secondary TB (but note BCG vaccine will also have positive reaction)
how to treat TB?
R: rifampicin I: isoniazid (must give with pyridoxine) P: pyrazinamide E: ethambutol [2 months RIPE + 4 months RI]
if secondary tb, just give isoniazid for 6 months daily
what does m. leprae cause?
tuberculoid leprosy: Th1 cell response
lepromatous leprosy: Th2 cell response
how to treat m. leprae?
6 months of rifampicin with dapsone
