Vibrio cholerae identification

Flat yellow colonies on TCBS
Oxidase pos
Gram comma shaped GNB
Citrate pos
LDC pos

specific processing of stools

all stools inoculated onto XLD, Mac, Selenite F broth, Campy BA or Butzlers for Campy
patient less than 2 years: stain for Cryptosporidium, media for EPEC
Loose stools: TCBS for Vibrio, Sorbital Mac for E coli 0157H7
bloody stools: sorbitol Mac
0157H7 is sorbitol negative (pale colonies) whilst other E coli are sorbitol pos (pink colonies)
query Campylobacter: Campy BA or Butzlers or Skirrows

Campy BA contains sheep blood, trimethoprim, vancomycin, cephalothin, amphotericin B and Polymyxin B
Skirrows contains 7% lysed horse blood, vancomycin, polymyxin B, trimethoprim

all plates for Campy incubated microaerophically at 42 degrees for up to 5 days.

Campylobacter identification

Gram negative small curved, spiral, seagull wings bacilli
growth at 37 and at 42 degrees
Darting motility in wet prep
Oxidase pos
Catalase pos
Sensitive to nalidixic acid 30ug
Resistant to cephalothin 30ug
Campylobacter jejuni is pos for hippurate hydrolysis
Campylobacter coli is neg for hippurate hydrolysis

Carriers

The following orgs can be carried by healthy people
Corynebacterium diphtheriae
Haemophilus influenzae
Streptococcus pneumoniae
Salmonella typhi
Vibrio cholerae
Staphylococcus aureus

WIDAL test

This is a serological test for typhoid and paratyphoid fever
Set up 2 rows of 6 tubes each
make dilutions of 1/40 up to 1/1280
Add the O antigen and H antigen to separate rows
O antigen is blue, and O agglutination is granuler
Vigorous shaking of the tube when reading will not destroy the agglutination
H antigen is pink, and H agglutination is floccular (cloud like)
Vigorous shaking will destroy the agglutination which is rectified by light centrifugation
O are incubated at 37 degrees
H are incubated at 56 degrees

This test is done when MC and S is negative. Patients dont visit the Dr at the appropriate time.
The organism is shed in the blood in weeks 1-2, in urine in weeks 2-3, and in stool indefinitely.
The name of the serotying is the Kauffman White scheme. The types of antigens tested for are the O and H. The Vi antigen is tested for to determine if the patient is a carrier

Neisseria species

2 pathogens of interest:
Neisseria meningitidis also called meningococcus
Neisseria gonorrhoeae also called gonococcus
GNC which is oxidase positive and produces beta lactamse
grows on enriched media (BA and CHOC) at 37 degrees
does not grow on general purpose media like NA
Non pathogens or commensals grow at room temp on enriched media and on NA at 37 degrees
CTA sugars are cysteine lactose sugars - enriched media in tubes which support the growth of Neissera. Has added CHO to aid in identification, look for acid production
Neisseria gonorrhoeae produces acid from glucose
Neisseria meningitidis produces acid from glucose and maltose
Neisseria lactamica produces acid from glucose, maltose and lactose
B catarrhalis produces no acid from glucose, maltose, lactose or sucrose
In the Gram of the specimen, look for the kidney shaped diplococci IC or EC in WBC. This needs to be reported to the Dr.
Be careful when making the smear and inoculating agar plates:
roll the swab over the slide/plate. In the smear this is done to preserve the morphology of the organism.
N meningitidis is encapsulated so a Quellung reaction can be done
culture plates are incubated under increased carbon di oxide

Pseudomonas aeruginosa

this is an oxidative organism, GNB, which produces 2 pigments, pyocyanin and pyoverdin. On NA, the colonies have a characteristic greenish colour. It also produces a distinct smell. Open the plate and pass it quickly past your nostrils. Dont inhale too eagerly and dont leave the plate open for long.
the identification rests on:
colonial morphology on agar plates
characteristic colour and smell
reactions in OF/Hugh Leifson medium acid in open and closed tube, oxidative reaction
oxidase reaction positive

this organism is very fond of damp/moist areas so it colonises readily anything that has "standing" water. It has a strong unhealthy relationship with cystic fibrosis patients. These patients produce the alginate gene. This gene is activated to produce alginate which surrounds the cell wall of the organism and therefore protects it against phagocytosis.
Now picture this:
the organism produces many toxins/enzymes that destroy elastin, collagen, lipase which all allow the organism to spread the infection
the pigment pyocyanin stops other bacteria from causing an infection at then same time
the organism destroys the RBC and produces toxic effects in the patient
the organism is resistant to most of the antibiotics used for GNB infections. So any antibiotic used will produce serious side effects in the patient
What a nasty little buggar??
And to top it all, it is capable of growing at room temp, body temp and at 42 degrees. So a fever in the patient wont kill this little horror!!!