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Lab. 2

includes: (1) haemophilus, (2) bordetella, (3). brucella.

1. haemophilus:

the most important pathogen is h. influenzae type b, which may causes meningitis, epiglutitis, pneumonia, conjunctivitis, nasopharyngitis, otitis media and externa.

haemophilus is opportunistic pathogen found normally in upper respiratory tract. this bacteria derives its name from essential growth factor in blood represented by:

x-factor: it is heat stable and physiologically known as hemin.

v-factor: it is heat labile known as nad coenzyme. haemophilus produce no exotoxine, non hemolytic.

general characteristics and morphology:

g –ve , pleomorphic, cocco bacilli in young cultures (6-8 hr.) and bacilli in old culture (up to 1 day), arranged in single, pairs or short chains, non spore forming, non motile, oxidase +ve, catalase +ve, some strains are capsulated produce polysaccharide, capsular ag. which is the most important virulence factor in h. inf. and according to this capsule h. inf. can be classified into 6 serotype: a, b, c, d, e and f.

the commonest virulence one is type b which is called prp (polyribose, ribitol-phosphate), some strains have fimbriae.

lab. diagnosis:

specimens ® csf, blood, pus, throat swab.

culture: blood agar is done on blood agar supplemented with (nad) and incubated at 37°c of 10% co2. the media can be made selective by adding penicillin and bacitracin. h. inflenzae also not grow on sheep blood agar except around colonies of staphylococcus (satellite phenomenon).

on chocolate agar: flat, grayish-brown at 37°c and 10% co2.

serology:

agglutination test.

coagulation resemble to quilling test for capsular strains (serum + capsular ag ? swelling of capsule (capsular swelling reaction).)

immunoflourescence.

h. influenzae requires v and x factors and non haemolytic.

h. parainfluenzae requires v only and non haemolytic.

h. parahaemolyticus and h. haemolyticus are haemolytic.

2. bordetella:

the most important pathogen is b. pertussis which cause whooping cough (pertusis), b. parapertussis can cause same disease, it does not requires x and v factors.

general characteristics and morphology:

pleomorphic, small coccobacilli or bacilli, some strains produce capsule when freshly isolated.

non motile, non spore forming, fimbria may be found in b. pertussis.

produce a powerful exotoxins called pertussis toxin (pt) and filamentous haemagglutinin (fha) that used in the vaccine of pertussis.

oxidase and catalasse (+ve).

produce haemolysin, strickt aerobic, capnophilic requires 10% co2.

lab. diagnosis:

specimens: saline nasal wash is the best, nasopharyngeal swab, cough dropingings expelled onto cough plate held’s infront of patient’s mouth, but not good as saline nasal wash.

culture: specimens are cultured on a selective medium called (bordet-gengou’s medium) containing (starch, blood, glycerol agar), and penicillin g 0.5 mg/ml is added to inhibit other resistant bacteria (normal flora). the plate is incubated at 35-37°c for 3-7 days in a moist environment aerobically.

3. brucellae:

which may causes brucellosis (malta fever) (rock fever) (mediterranean fever) (undulant fever).

brucellosis is a zoonosis disease and man may get infection when he comes close contact with animals and animal products.

there are 2 clinically important spp.:

b. abortus.

b. melitensis: which may cause the same disease.

general characteristics and morphology:

specimens ? blood for culture and serology. tissue ? liver, spleen biopsy, lymph node biopsy, bone marrow.

culture ? brucellae have complex nutritional requirements, bold agar, tryptic soya agar and tryptic soya broth that containing (amino acid, vitamins and salts).

b. abortus requires 5-10% co2, culture is difficult and positive in 20% of cases optimal condition of cultivation are 2-3 days at 37°c.

serology: infection of brucellae gives rise to igm abs. which persist for up to 3 months after which level wanes off. igg and iga appear after 3 weeks. rose bengal serological test (ag-ab) reaction is reliable and common in lab. diagnosis of brucellusis.