clinically important bacteria

clinical classification of bacteria

mainly belong to Enterobacteriaceae family & are non-fastidious, facultative anaerobes with fermentative metabolism, oxidase negative, bile tolerant, & if motile then have peritrichous flagella
obligate anaerobes:
- bacteroidaceae (non-sporing)
- bacteroides (mixed acid f. glucose)
- fusobacterium (butyric acid mainly f. glucose)
- leptotrichia (lactic acid mainly f. glucose)
facultative anaerobes:
- oxidase negative:
  - enterobacteriaceae (ferm., non-fastidious)
    - Escherichia (acid f.lactose)
    - Edwardsiella
    - Citrobacter (acid f.lactose)
    - Salmonella (ONPG neg, urea neg; mannitol→gas)
    - Shigella (ONPG neg, urea neg; mannitol→no gas)
    - Klebsiella (acid f. lactose)
    - Enterobacter (acid f. lactose)
    - Serratia
    - Proteus (ONPG neg. urea pos.)
    - Providencia
    - Yersinia including bubonic plague and Yersiniosis (ONPG pos.)
    - Erwinia
    - actinobacillus (ferm., pleomorphic fastidious)
- oxidase positive:
  - fermentative:
    - Vibrio
    - Aeromonas
    - Pasteurella
    - Plesiomonas
oxidative
- Flavobacterium (variably fac.anaer.)
obligate aerobes:
- Pseudomonas (oxidase +ve, not ferment.)
- Xanthomonas
- Alcaligenes (oxidase +ve, alkali producing)
fastidious
- Legionella (Legionaire's disease)

facultative anaerobes
- Haemophilus (fastid.,)
obligate aerobes
- Brucella (fastid. needs vitamins)
- Bordetella (complex media with nicotinic acid)
- Francisella (highly fastid.)

obligate aerobes
- Neisseria (bean-shaped diplococci, fastid., oxidase +ve)
  - N. gonorrhoeae (gonococcus)
  - N. meningitidis (meningococcus)
- Acinetobacter
- Moraxella (oxidase +ve)
- Branhamella (oxidase +ve)
anaerobes
- Veillonella (oxidase neg., fastid.)
intracellular
- Rickettsia
- Coxsiella
- Chlamydia

Spirillum (aerob/microaerophilic)
Campylobacter (microaerophilic/anaerobic)
Spirochaetaceae (helically coiled)
Treponema
- syphilis
Borrelia
- Borrelia recurrentis the cause of louse-borne relapsing fever and evolved to spread via the human louse rather than ticks presumably in response to higher density living of the Neolithic period
  - evolved from the tick-borne cousin, B. duttonii, about 6,000 to 4,000 years ago ¹⁾
- Borrelia burgdorferi is a tick-borne bacteria which causes Lyme disease
- various other Borrelia sp. including B. duttonii cause tick-borne relapsing fever
Leptospira
- leptospirosis

sporing:
- Bacilli (aerobic)
- Bacillus anthracis (anthrax)
- Clostridium sp. (anaerobic with variable O2 tolerance)
non-sporing:
- Lactobacilli
- Listeria
- Erysipelothrix
coryneform & filamentous:
- Corynebacterium
- Propionibacterium
- Actinomyces
  - Kytococcus sedentarius obligate aerobe associated with foul foot odour from sweaty feet and pitted keratolysis of soles of feet, also opportunistics and can rarely cause SBE and infectove spondylitis in diabetics or immunocompromised
- Nocardia
mycobacteria (not really Gram +ve)
- tuberculosis (TB)
Streptomyces

catalase +ve
- Micrococcaceae
- staphylococcus (fermentative)
  - Staph. aureus
- Micrococcus (oxidative)
catalase -ve
- Streptococcaceae (fac. anaerobes, pairs or chains)
- streptococcus / streptococcal infections
  - Str. pyogenes
  - Str. pneumoniae pneumococcus
- Enterococcus including VRE Enterococcus faecalis formerly known as Str. faecalis
- Peptococcaceae (oblig. anaerobes)
- Peptococcus (no chains usually)
- Peptostreptococcus (pairs or chains)
- Parvimonas infections

Mycoplasmataceae
- Mycoplasma (need sterols, most fac.anaer.)
- Acholeplasma (do not need sterols)
- Ureaplasma (hydrolyse urea, need urea & sterols)
L forms of Classical bacteria (require hypertonicity)
- NB. induced by antibiotics/lysozyme/Ab-C/osmotic/etc.
- Need phase contrast or Giemsa stain;
- stable L-forms (wholly cell wall defic. abn. form)
  - not able to revert;
- unstable L forms (partly defic. cell wall abn. form)
  - revert to normal form of bacteria if inducing factor withdrawn;

Include:
- pyogenic cocci - S.aureus; Str.pyogenes/pneumoniae; N.mening./gono.
- Gram-ve rods - E.coli; Proteus; Ps.aerug.; Bacteroides;

¹⁾