enterobacteria and pseudomonads Flashcards
enterobacteria are gram
negative
what shape are enterobacteria
non spore forming rods
do enterobacteria usually colonise oral cavity
no. transient, non resident members
what are the two types of enterobacteria. name examples and state how they are differentiated
lactose fermenting: ecoli, klebsiella (pink on macconkey agar)
non lactose fermenting: salmonella, shigella (colourless on macconkey agar)
why is klebsiella so virulent
encapsulated. capsule is virulence factor
are enterobacteria aerobic
facultative anaerobes
do enterobacteria have oxidase
no. oxidase negative
where are enterobacteria usually found
normal intestinal flora
what factors increase risk of enterobacteria carriage
hospitalisation especially long stay, terminally ill patients
immunocompromised
mucositis (damage caused by mucositis allow gram negative to penetrate mucosa)
xerostomia because dry mouth allow gram negative to displace normal flora
diabetes, alcoholism
antibiotic treatment altering normal oral flora
loss of normal airway protection eg due to airway intubation, causing reflux of gi organisms
change in adherence factors. commensal bacteria attach to mucosal cells lose adherence allow gram neg to take over
respiratory disease
how to test for type of enterobacteria (4)
serological agglutination test
oxidation glucose fermentation
Kliger iron agar slants
MALDI-TOF
are e coli gram negative or positive
negative. enterobacteria
what can e coli cause
community UTI, neonatal septicemia, meningitis, post operative abdominal sepsis, diarrhea
what toxin does enterohaemorrhagic e coli produce
shiga toxin
what can klebsiella cause
hospita associated pathogen that can cause UTI, pneumonia, biliary tract infections, wound infections, bacteremia, meningitis, liver abscess
what enterobacteria has highly mucoid strains
klebsiella, due to overproduction of capsule
what is klebsiella resistant to
ampicillin, amoxicillin due to presence of intrinsiv enzymes
what is enterobacter resistant to
cephalosporins, intrinsic resistance
what enterobacteria forms frons on the agar plate
proteus due to swarming motility. has hundreds of petrichous flagella
what does typhoidal salmonella cause
enteric fever
how does enteric fever invade body
bacteria invade intestinal lymphoid tissue (eyer’s patches) and disseminates through bloodstream. reproduces in macrophages
how is enteric fever spread
salmonella typhi/paratyphi are foodborne
clinical symptoms of enteric fever
prolonged fever, diarrhea/constipation, rose spots on abdominal skin, hepatosplenomegaly, intestinal perforation
why can stool culture be used to diagnose salmonella typhi infection
bacteria may be carried in stool for a long time after patient has clinically recovered and spread to others
what does non typhoidal salmonella cause
gastroenteritis. may cause invasive disease in immunocompromised hosts
what is the source of non typhoidal salmonella
animals
is non typhoidal salmonella self limiting
yes. if invasive, no, need antibiotics though antibiotics tend to suppress normal flora rather than salmonella
are pseudomonads gram positive or negative
negative
are pseudomonads motile
yes
are pseuodomonads oxidase positive or negative
positive
where can pseudomonads be found
wet environmnet
what bacteria can be commonly found in dental unit water lines
p aeruginosa
why is p aeruginosa able to survive in dental unit water lines
able to survive on little nutrients, in disinfectants. survives in biofilms
what is malignant otitis externa
p aeruginosa infection in diabetics. infection at face tissues, can spread to bone
why is p aeruginosa hard to eradicate from implants
biofilm
what media is used for burkholderia pseudomallei
pseudomonad. ashtile media (dry, crinkly appearance)
what are common causes of maxillary sinus infection
p aeruginosa in immunocompromised. s pneumoniae in kids
what are coliforms
gram negative, rod shaped, non spore forming, facultative anaerobe, ferment lactose and produce gas and acid in the process
why can macconkey grow coliforms
contains bile salts to inhibit non intestinal bacteria and contains lactose with neutral red to distinguish pink or red lactose fermenting oclonies eg ecoli from non fermenting pale yellow colonies eg salmonella shigella
