classification of pathogenic bacteria

Question 1

List clinically signi cant bacteria which are not readily identi ed by Gram staining and outline how they are identi ed or distinguished.

Answer 1

1- Mycobacterium 
-Acid and alcohol fast bacilli- resistant to decolorisation after staining with carbon fuchsin
Lab testing
-ZN or Auramine staining
-Does not identify between species unless culture is grown
-TB-link to HIV, Atypical, Leprae
2-Spirocytes 
-Long, spiral shaped bacteria
-not easily seen with light microscopy-dark microscopy and immunofluorescence used
-difficult to culture 
A. syphilis
Primary infection- skin lesions 
secondary- Systemic illness
Tertiary- CNS
B. Lyme
stage 1- skin rash 
stage 2- systemic illness 
stage 3- chronic disease- skin, neurological, joint  
C.Leptospirosis
concentrates in kidneys 
spread through urine and other body fluids
3- Chlamydia 
Intracellular bacteria 
Grown on cell lines not agar 
Respiratory or ophthalmic/genital infection

Question 2

List clinically signi cant Gram positive bacteria and outline how they are identi ed or distinguished.

Answer 2

COCCI- Round shaped
Staphylococci- coagulase test
-Positive- aureus 
-Negative
Streptococci-haemolytic
-Partial- turn agar green.
Pneumoniae
Viridans 
-Complete- turn agar clear
Group A- Pyogenes
Group B- Agalactiae 
Group D- enterococci 
-Non-haemolytic

BACILLI- Rod shaped 
Anaerobic- spore forming
Clostrium difficile 
Clostrium tetani
Clostridium perfringens

Question 3

List clinically signi cant Gram negative bacteria and outline how they are identi ed or distinguished.

Answer 3

BACILLI
-ANAEROBIC- Grown on Macconkeys 
1. Lactose fermenting: 
-E.coli: 
enterotoxigenic
enterohaemoraggic 
2. Non- lactose fermenting
-Salmonella: enterica and typhi
-Shingella 
-Pseudomans
-Proteus 
-ANAEROBIC:
Bacteriodes
Polyphormanas
Prevotella 
-CURVED:
H. Pylori 
Camplyobacter 
COCCO-BACILLI:
Haemophilus influenza 
COCCI: 
1.Neisseria :
Gonorrea
Meningitis 
2. Moxarella catarrahalis