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 meningitis
2. Acute epiglottitis
3. 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-capsulated
Antimicrobial 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

STREPTOCOCCUS
Streptococcus pyogenes
Streptococcus agalactiae
Enterococci
TO BE CONTINUE..
Explain what happens in the following
biochemical tests:
i) Indole test
ii) 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.