Table of Contents

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