CLASSIFICATION OF MEDICALLY IMPORTANT BACTERIA I. Rigid, thick–walled cell II. Flexible, thin-walled cells, III. Wall-less cells,

I.Rigid,thick-walled cell: Divided into: A) Free-living outside cells, divided into: 1- Gram positive, divided into: a. Cocci, e.g.: Staph. and Strept. b. Spore-forming rods, divided into: (i) Aerobic, e.g.: Bacillus. (ii) Anaerobic, e.g.: Clostridium.

c. Non-spore forming rods, divided into: (i) Non-filamentous, e.g.: Corynebacterium. (ii) Filamentous, e.g.: Actinomyces & Nocardia

2- Gram negative, divided into: a. Cocci, e.g.: Neisseria. b. Rods, divided into: (i) Facultative, divided into: 1. Straight, divided into: a. Respiratory organisms, e.g.: Bordetella. b. Zoonotic organisms, e.g.: Brucella. c. Enteric and related organisms, e.g. E.coli.

2. Curved e.g. Vibrio, Helicobacter. (ii) Aerobic, e.g.: Pseudomonas (iii) Anaerobic, e.g: Bacteroides. c. Acid-fast, e.g., Mycobacterium.

B) Non-free living inside cells, e.g.: Chlamydia. II. Flexible, thin-walled cells, e.g.: Treponema III. Wall-less cells, e.g.: Mycoplasma.

BACTERIAL PATHOGENS Major bacterial pathogens may be divided into: 1- READILY GRAM- STAINED: 2- NOT READILY GRAM- STAINED:

1- READILY GRAM-STAINED: Divided into: a) Gram positive cocci, e.g.: Staph. & Strept. b) Gram negative cocci, e.g.: Neisseria. c) Gram positive rods, e.g.: Corynebacterium, Bacillus, Clostridia, Nocardia, Actinomyces.

d) Gram negative rods, divided into: (i) Gastro-intestinal tract organisms, e.g 1- Pathogenic inside & outside G.I. tract : E.coli, Salmonella. 2- Pathogenic inside G.I. tract, only e.g.: Shigella, Vibrio, Campylobacter, Helicobacter. 3- Pathogenic outside G.I. tract, e.g.: Klebsiella, Pseud., Prot.,Bacteroides.

(ii) Respiratory tract organisms, e.g.: Legionella, Haemophilus, Bordetella. (iii) Zoonotic bacteria, e.g.: Brucella, Pasteurella, Yersinia, Francisella.

2- NOT READILY GRAM- STAINED: Divided into: a) Obligate intracellular pathogens e.g.: Chlamydia, Rickettsia. b) Not obligate intracellular parasites, e.g.: Treponema, Mycobacteria, Mycoplasma, Leptospira.

COMMON NOTIFIABLE DISEASES IN SUDAN: 1.Cholera. 2.Tuberculosis. 3.Enteric fever. 4.C. S. M. 5.Tetanus.

6. Whooping cough. 7. Diphtheria. 8. Anthrax. 9. Brucellosis. 10-Plague. 11-Relapsing fever.