enterobacteria and pseudomonads

Question 1

enterobacteria are gram

Answer 1

negative

Question 2

what shape are enterobacteria

Answer 2

non spore forming rods

Question 3

do enterobacteria usually colonise oral cavity

Answer 3

no. transient, non resident members

Question 4

what are the two types of enterobacteria. name examples and state how they are differentiated

Answer 4

lactose fermenting: ecoli, klebsiella (pink on macconkey agar)

non lactose fermenting: salmonella, shigella (colourless on macconkey agar)

Question 5

why is klebsiella so virulent

Answer 5

encapsulated. capsule is virulence factor

Question 6

are enterobacteria aerobic

Answer 6

facultative anaerobes

Question 7

do enterobacteria have oxidase

Answer 7

no. oxidase negative

Question 8

where are enterobacteria usually found

Answer 8

normal intestinal flora

Question 9

what factors increase risk of enterobacteria carriage

Answer 9

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

Question 10

how to test for type of enterobacteria (4)

Answer 10

serological agglutination test
oxidation glucose fermentation
Kliger iron agar slants
MALDI-TOF

Question 11

are e coli gram negative or positive

Answer 11

negative. enterobacteria

Question 12

what can e coli cause

Answer 12

community UTI, neonatal septicemia, meningitis, post operative abdominal sepsis, diarrhea

Question 13

what toxin does enterohaemorrhagic e coli produce

Answer 13

shiga toxin

Question 14

what can klebsiella cause

Answer 14

hospita associated pathogen that can cause UTI, pneumonia, biliary tract infections, wound infections, bacteremia, meningitis, liver abscess

Question 15

what enterobacteria has highly mucoid strains

Answer 15

klebsiella, due to overproduction of capsule

Question 16

what is klebsiella resistant to

Answer 16

ampicillin, amoxicillin due to presence of intrinsiv enzymes

Question 17

what is enterobacter resistant to

Answer 17

cephalosporins, intrinsic resistance

Question 18

what enterobacteria forms frons on the agar plate

Answer 18

proteus due to swarming motility. has hundreds of petrichous flagella

Question 19

what does typhoidal salmonella cause

Answer 19

enteric fever

Question 20

how does enteric fever invade body

Answer 20

bacteria invade intestinal lymphoid tissue (eyer’s patches) and disseminates through bloodstream. reproduces in macrophages

Question 21

how is enteric fever spread

Answer 21

salmonella typhi/paratyphi are foodborne

Question 22

clinical symptoms of enteric fever

Answer 22

prolonged fever, diarrhea/constipation, rose spots on abdominal skin, hepatosplenomegaly, intestinal perforation

Question 23

why can stool culture be used to diagnose salmonella typhi infection

Answer 23

bacteria may be carried in stool for a long time after patient has clinically recovered and spread to others

Question 24

what does non typhoidal salmonella cause

Answer 24

gastroenteritis. may cause invasive disease in immunocompromised hosts

Question 25

what is the source of non typhoidal salmonella

Answer 25

animals

Question 26

is non typhoidal salmonella self limiting

Answer 26

yes. if invasive, no, need antibiotics though antibiotics tend to suppress normal flora rather than salmonella

Question 27

are pseudomonads gram positive or negative

Answer 27

negative

Question 28

are pseudomonads motile

Answer 28

yes

Question 29

are pseuodomonads oxidase positive or negative

Answer 29

positive

Question 30

where can pseudomonads be found

Answer 30

wet environmnet

Question 31

what bacteria can be commonly found in dental unit water lines

Answer 31

p aeruginosa

Question 32

why is p aeruginosa able to survive in dental unit water lines

Answer 32

able to survive on little nutrients, in disinfectants. survives in biofilms

Question 33

what is malignant otitis externa

Answer 33

p aeruginosa infection in diabetics. infection at face tissues, can spread to bone

Question 34

why is p aeruginosa hard to eradicate from implants

Answer 34

biofilm

Question 35

what media is used for burkholderia pseudomallei

Answer 35

pseudomonad. ashtile media (dry, crinkly appearance)

Question 36

what are common causes of maxillary sinus infection

Answer 36

p aeruginosa in immunocompromised. s pneumoniae in kids

Question 37

what are coliforms

Answer 37

gram negative, rod shaped, non spore forming, facultative anaerobe, ferment lactose and produce gas and acid in the process

Question 38

why can macconkey grow coliforms

Answer 38

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