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- Microscopic appearance
- Cultural characteristics
- Biochemical Tests of Campylobacter species.
Campylobacter
Campylobacters are
small delicate,
spirally curved,
motile Gram
negative bacteria
Campylobacters jejuni
Campylobacters coli
Campylobacter jejuni causing:-
- Enteritis.
*** Fresh diarrhoeal or dysenteric specimens
containing blood, pus and mucus (child under
2 y).
Campylobacters are Gram negative curved rod
A filtration technique and a non-selective culture
medium. A filter of 0.47 μm pore size will retain
faecal commensals and allow Campylobacters to
pass through
A selective culture medium that contains
antimicrobials to inhibit the growth of faecal
commensals.
Blaser’s medium: Containing 10% sheep blood, vancomycin,
trimethoprim, polymyxin B, cephalothin, amphotericin B.
Skirrow’s blood agar: Containing lyzed horse blood, vancomycin,
polymyxin B, trimethoprim
Butzler virion medium: Containing defibrinated sheep blood, cefoperazone, rifampicin, colistin, amphotericin B.
Improved Preston blood free-medium: Containing
cefoperazone
and amphotericin B. This supplement is added to a
Campylobacter blood-free agar base containing
bacteriological charcoal, ferrous sulphate, sodium
deoxycholate, sodium pyruvate, casein hydrolysate,
nutrient broth and agar. Isolations are best on this medium
when cultures are incubated at 37 ºC rather than 42–43 ºC
C. jejuni produces grey,
moist, flat-spreading
colonies. Some strains
may have a green hue or a
dry appearance with or
without a metallic sheen.
On Blood agar: C. jejuni and C. coli produce
nonhaemolytic spreading, droplet-like colonies
Catalase Test
Oxidase Test
-Hippurate hydrolysis: this test can be used to differentiate
C. jejuni from C. coli.
-Hippurate is hydrolyzed by C. jejuni and not hydrolyzed by
C. coli.
The end product of hydrolysis of hippuric acid by
hippuricase include glycine and benzoic acid.
Glycine is deaminated by the oxidizing agent
ninhydrin.
The end products of the ninhydrin oxidation reacts
to form a purple-coloured product.
- Microscopic appearance
- Cultural characteristics
- Biochemical Tests of Helicobacter species.
Helicobacter
Helicobacter
- gastric and duodenal ulcers (eradication of H. pylori
results in cure and reduces ulcer recurrence in 90% of
peptic ulcer patients).
- H. pylori also contribute to diarrhoea, malnutrition and
growth failure in young children (reduced gastric acid
protection leads to infection with enteropathogens).
- To isolate H. pylori by culture a gastric biopsy is
required. Place a biopsy of mucosa from the gastric
antrum in a bottle containing about 0.5 ml of sterile
physiological saline.
It should reach the laboratory with the minimum of delay.
Using a sterile scalpel and forceps,
cut the biopsy into small pieces.
Inoculate a plate of chocolate
(heated blood) agar or
Campylobacter medium, and
also place a piece of biopsy in
Christensens urea broth
H. pylori appears as a small, spiral or S-shaped Gram
negative bacterium
On blood agar, H. pylori colonies are slightly
beta-haemolytic. Growth is best at 37 ºC
When the strain is urease producing, the enzyme will break down
the urea (by hydrolysis) to give ammonia and carbon dioxide.
With the release of ammonia, the medium becomes alkaline as
shown by a change
in colour of the indicator to pink-red.
Urease Test
The test organism is
cultured in a medium which
contains urea and the
indicator phenol red.
Urea breath test