BRUCELLA
MAIN SPECIES
Brucella melintensis Brucella abortus Brucella suis
NORMAL HABITAT
Obligate intracellular pathogens of animals B. melitensis mainly found in goat and sheep B. abotus infects cattle B. suis found in pigs and occasionally in goat Other animal including horse, camel, eland
and wild rodents
ROUTES OF INFECTION
Mosquitoes helps in transfer Brucella from animal to human
Also by ingesting unpastuerized milk or milk products, enter damaged skin or eyes, inhaled in airborne particles or aerosols.
LABORATORY DIAGNOSTICS
MICROSCOPIC OBSERVATION
Non-motile Gram negative Coccobacili Show bipolar staining Rarely found in direct smear from uncultured
specimen On Gram stain they appear as dense clumps
of Gram-negative coccobacilli and are exceedingly difficult to see.
CULTURE CHARACTERISTICS
Mostly cultured from blood of high fever patient(Brucellosis)
Isolation is extremely rare in chronic brucellosis
In all blood culture, they need carbon dioxide Blood culture should be kept in 4 – 6 weeks
before result as no organisms isolated To reduce the risk of contamination, use the
diphasic medium such as Castaneda or tryptic soy broth or agar
Brucellae are aerobic with enriched of carbon dioxide
BIOCHEMICAL TESTS SEROLOGY TESTS
Urease and hydrogen sulphide production
All brucella strains are catalase positive
Possess two antigens called A and M
Famous test serum: Rapid slide
agglutination test Tube agglutination
titration test
SEROLOGY TEST
It is crucial to be able to differentiate Brucella from Salmonella which could also be isolated from blood cultures and are Gram-negative. Testing for urease would successfully accomplish the task; as it is positive for the Brucella and negative for the Salmonella.
HAEMOPHILUS
MEDICAL IMPORTANT SPECIES
Haemophilus influenzae Haemophilus aegyptius Haemophilus ducreyi
NORMAL HABITAT
H.influenzae (mostly non-capsulated strains), H. parainfluenzae and H.aegyptius is normal flora of the upper respiratory tract
Infections causing:1. Pyogenic meningitis2. Acute epiglottitis3. Cellulitis, middle ear infection,etc
CONJUCTIVITIS
LABORATORY DIAGNOSIS
MICROSCOPY
Small, non-motile, Gram negative rods or coccobacili
Long thread-like form in old csf culture
MICROSCOPIC OBSERVATION
CULTURE OF H.INFLUNZAE
H.influenzae grows better in aerobically compare to anaerobically
The optimum temperature for growth 35 – 37oC
The are X and V factor Both represent in blood agar and permit the
culture to grow H.influenzae and H.aegyptius need X and V
factor, H. parainfluenzae need V factor and H.ducreyi need X factor
BIOCHEMICAL TESTS
Not usually used to identify hemophilus 6 biovars of H.influenzae are recognized
based on the indole, urease and ornithine decarboxylase (ODC) reactions of the diff strains
SEROLOGY
Consist of 1 – f serotypes Mostly causing meningitis belong to
serogroup b Most strains that cause chronic bronchial
disease are non-capsulatedAntimicrobial sensitivity Resistant towards chloramphenicol,
ampicilin, tetracycline, erythromycin and cotrimoxazole
H. ducreyi is sensitive to sulphonamides Ampicillin resistant are common
STAPHYLOCOCCUS & STREPTOCOCCUS
STAPHYLOCOCCUS Staphylococcus aureus
Staphylococcus epidermidis
Staphylococcus saprophyticus
INTRODUCTION
Are microbial flora of the skin, upper respiratory tract and intestinal tract
S.aureus usually cause abscesses, boils, conjuctivitis, pneumonia, septicemia, food poisoning and scalded skin syndrome
S. epidermidis causing bacteraemia S. saprophyticus causing cystitis and acute
urethritis
LABORATORY DIAGNOSIS
Microscopy Non-motile Non capsulate Gram positive cocci Arrangement single or in pair Size 1 µm diameter
CULTURE
Grow well in aerobically and also in present of carbon dioxide
Temperature between 10 – 420C, optimum temperature are between 35 - 370C
S.AUREUS
Produce yellow to cream in blood and chocolate agar (heated agar)
Occationally produce white 1-2 mm in diameter colonies
Some strain produce beta-hemolytic when grown aerobically
Colonies are slightly raised and easily emulsified on a slide
Non- lactose fermenter in MacConkey agar Mannitol salt agar is a useful differential and
selective agar to identify S.aureus
ON BLOOD AGAR
S.EPIDERMIDIS
Colony is white Non hemolytic in blood agar
S. saprophyticus Maybe white or yellow There are non-hemolytic in BA Not grow anaerobically No growth in MacConkey agar
BIOCHEMICAL REACTIONS
S.aureus DNAse test will be positive for S.aureus but
negative in other species Catalase test will be positive in all
staphylococcus but negative in all streptococcus
S. epidermidis and S. saprophyticus Coagulase negative DNAse negative Catalase positive
ANTIMICROBIAL SENSITIVITY
Erythromycin Clindamysin Fucidin Vancomycin Many strains of S.aureus are penicillin-
resistant S.epidermidis are more resistant than
S.aureus to antibiotics S. saprophyticus less resistant to antibiotics
than S.aureus and S.epidermidis
STREPTOCOCCUSStreptococcus pyogenes
Streptococcus agalactiae
Enterococci
TO BE CONTINUE..
Explain what happens in the following biochemical tests:i) Indole testii) Methyl red test
8 marks) b) Write the scientific name of a bacterium that gave positive results for both tests.
(2 marks)
QUESTION
State all group of gram positive and
gram negative bacteria.