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.