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COMMON BACTERIA OF MEDICAL IMPORTANCE
I
Gram-positive bacteria
A. Cocci
a) cells in clusters (catalase +ve)
Staphylococcus
i) coagulase +ve
Staph.
aureus
ii) coagulase –ve, many species, examples:
Staph.
epidermidis
Staph. saprophyticus
b) cells in pairs/chains (catalase -ve)
Streptococcus
i)
β-haemolytic
group A
(Strep. pyogenes)
group B (Strep.
agalactiae)
group C
group D (Strep.
bovis,
or now in genus Enterococci)
group G
ii)
a-haemolytic
Strep.
pneumoniae (lancet-shaped diplococci)
‘viridans’
streptococci, many species, examples:
Strep.
milleri
anaerobic streps
iii) non-haemolytic
most enterococci
B. Bacilli (rod-shaped)
a) aerobic
Corynebacterium
– small pleomorphic
Listeria
– small, sometimes coccibacilli
Bacillus
(spores) – large
Nocardia
– slender, beaded, modified acid-fast +ve
b) anaerobic
Clostridium
(spores) - large
Actinomyces
(narrow, slender branching)
II
Gram-negative bacteria
A. Bacilli (rod-shaped)
a) aerobic
Simple growth requirements
i) lactose fermenters (LFS)
E. coli
Klebsiella
(mucoid)
Enterobacter
ii) lactose non-fermenters (NLFs)
Salmonella
Shigella
Proteus
(urease +ve)
Citrobacter
iii) others
Pseudomonas
(oxidase +ve)
Burkholderia (oxidase +ve)
Stenotrophomonas (oxidase –ve)
Acinetobacter (oxidase -ve)
Vibrio
(comma shape)
Yersinia
Fastidious growth requirements
i) Legionella
– special request
ii) Haemophilus
(X & V factors)
iii) Bordetella
- special request, PCR
iv) Brucella
- special request
v) Bartonella
- special request
vi) Campylobacter
(seagull shape, 42oC)
b) anaerobic
Bacteroides
Fusobacterium
Porphyromonas
Prevotella
B. Cocci
a) cells in pairs, coffee-bean shapes (oxidase +ve)
Neisseria
Moraxella
b) anaerobes:
Veillonella
III
Mycobacteria: Acid Fast
a)
M. tuberculosis
b)
M. avium-intracellulare
c) Many other species
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