Pigment of Staphylococcus
Golden yellow pigment of Staphylococcus aureus which is ATCC strain 25923 as shown above picture.
Spherical, non motile, gram positive, cluster forming. On nutrient agar , growth is opaque and golden yellow or white color. Catalase test positive, coagulase test positive, oxidase negative , aerobic or facultative anaerobe. Parasite of human and animal.
Normal flora of skin, upper respiratory tract and feces of human, animal and birds too.
Round or spherical arranged in clusters.
Non motile, non sporing, usually non encapsulate while some strains are encapsulate. Capsule is of two types
Micro capsule <200 nm
Macro capsule >200 nm and is responsible for slime layer
On nutrient agar
- Smooth, circular, often yellow pigmented colonies and non diffusible.
- 1-2 mm in diameter
- Butyrous in consistency
On blood agar
Golden yellow and increased in the presence of CO2 and also at room temperature. Pigmentation can be induced by culturing bacteria into 30% milk agar, potato and 1% glycerol monoacetate or phosphate agar.
Selective media for Staphylococcus
- 7-10% salt agar
- Mannitol salt agar
- Tellurite glycine agar
- Phenolphthalien phosphate agar
- Polymyxin B agar (75 μg/ml)
Note: Staphylococcus aureus grow well on this medium but coagulase negative Staphylococci (CoNS) can not grow.
Thermal death point of Staphylococcus aureus is 60°C for 30 minutes.
It can survive in dried pus for 2-3 months.
Protein -A: It has specific affinity for Fc portion of the IgG molecule (except Ig3) leaving the Fab region free to combine with its specific antigen resulting in agglutination known as coagglutination. Peptidoglycan of cell activates complement and induces release of inflammatory cytokines. Similarly teichoic acid of cell wall facilitates adhesion of the cocci to the host cell surface.
With the use of 28 phages, several hundred phage types have been identified among them important phage types are-
Group 1: 8052A/79 (Hospital strains)
Group 2: 3B/3C/55 (Impetigo / Staphyococcal Scalded Syndrome)
Group 3: 6/47 (Enterotoxin producer)
There are 30 serotypes based on protein A antigen.
Enzyme and toxins
Haemolysin: alpha, beta, gamma
Type A and B are responsible for food poisoning.
25 µg of toxin B can cause food poisoning.
Epidermolytic toxin: It is responsible for Staphylococcal Scalded Syndrome (SSS) or Ritter’s disease.
Toxic Shock Syndrome Toxin (TSST): Type -F
Coagulase : It is of two types bound and free coagulase.
Pathogenecity of Staphylococcus aureus
Staphylococcus aureus can cause following diseases-
- Corneal ulcer
- Mastitis: It is an inflammation of breast.
- Empyemia : It is accumulation of pus in the body cavity.
- Food poisoning
- Staphylococcal Scalded Syndrome
- Toxic Shock Syndrome (TSS)-enterotoxin F
- Septic arthritis
- Bailey & Scott’s Diagnostic Microbiology. Editors: Bettey A. Forbes, Daniel F. Sahm & Alice S. Weissfeld, 12th ed 2007, Publisher Elsevier.
- Clinical Microbiology Procedure Hand book , Chief in editor H.D. Isenberg, Albert Einstein College of Medicine, New York, Publisher ASM (American Society for Microbiology), Washington DC.
- Colour Atlas and Text book of Diagnostic Microbiology. Editors: Koneman E.W., Allen D.D., Dowell V.R. Jr and Sommers H.M.
- Jawetz, Melnick and Adelberg’s Medical Microbiology. Editors: Geo. F. Brook, Janet S. Butel & Stephen A. Morse, 21st ed 1998, Publisher Appleton & Lance, Co Stamford Connecticut.
- Mackie and Mc Cartney Practical Medical Microbiology. Editors: J.G. Colle, A.G. Fraser, B.P. Marmion, A. Simmous, 4th ed, Publisher Churchill Living Stone, New York, Melborne, Sans Franscisco 1996.
- Manual of Clinical Microbiology. Editors: P.R. Murray, E. J. Baron, M. A. Pfaller, F. C. Tenover and R. H. Yolken, 7th ed 2005, Publisher ASM, USA
- Text book of Diagnostic Microbiology. Editors: Connie R. Mahon, Donald G. Lehman & George Manuselis, 3rd edition2007, Publisher Elsevier.
- District Laboratory Practice in Tropical Countries – Part-2- Monica Cheesebrough- 2nd Edn Update