Lecture 1 Bacteriology Systemic Bacteriology Objective Pyogenic cocci
Lecture 1 Bacteriology Systemic Bacteriology Objective : Pyogenic cocci : Pyogenic means “ pus forming” Cocci means “spherical bacteria” They include: 1. Staphylococcus (Gram positive) 2. Streptococcus (Gram positive) 3. Neisseria (Gram Negative) The pathogenic cocci are often called pyogenic cocci because of their ability to form pus (suppuration).
Blood agar plate, S. aureus 8
�Staph is initially differentiated by coagulase into � 1. Coagulase positive (Staphlycoccous aureus) � 2. Coagulase negative (Co. NS): S. epidermidis, S. saprophyticus.
Antigenic structure 1. Protein A 2. Teichoic acid 3. Capsule 4. Surface receptors 5. Peptidoglycan
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Effects of staphylococcal toxins on skin 18
Clinical Manifestations/Disease • SKIN ü ü ü folliculitis boils (furuncles) carbuncles impetigo (bullous & pustular) scalded skin syndrome • Neonates and children under 4 years
Cutaneous lesions of S. aureus 22
*coagulase-positive staphylococci are considered pathogenic for humans. F- Susceptibility Testing: broth microdilution or disk diffusion susceptibility testing should be done. Most strain of S. aureus are penicillin resistant due to B-lactamase (penicillinase) production. Some drug resist penicillinase, so, they could kill some species of staphylococcus , so Naficillin and methicllin are used. Some strains are found as resistant to methicillin. This resistance is known as methicillin resistance S. aureus (M. R. S. A). this resistance is due genetic information in plasmid. Transmission of MRSA is done from one person to others occuring in the hospitals. G-phage typing: is done for epidemiology in a grouped patients to determine from where the infection is transmitted (i. e from hospital or from places).
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