Online microbiology and biology related notes by SAGAR ARYAL
Baird Parker Agar Baird Parker Agar was developed by Baird Parker from the Tellurite-glycine formulation of Zebovitz et al for isolation and enumeration of Staphylococci in food and other material since it allows a good differentiation of coagulase positive strains. Sodium pyruvate was added as a selective growth stimulant, and egg yolk emulsion as a … Read moreBaird Parker Agar
Methicillin Resistant Staphylococcus aureus (MRSA) MRSA is mediated by mecA gene; which is a chromosomally coded. It alters penicillin binding protein (PBP) present on S. aureus cell membrane to PBP-2a: PBP is an essential protein needed for cell wall synthesis of bacteria. β lactam drugs bind and inhibit this protein, there by inhibiting cell wall … Read moreMethicillin Resistant Staphylococcus aureus (MRSA)
Mannitol Salt Agar (MSA) Introduction of Mannitol Salt Agar (MSA) Mannitol Salt Agar (MSA) is used as a selective and differential medium for the isolation and identification of Staphylococcus aureus from clinical and non-clinical specimens. It is recommended for the detection and enumeration of coagulase-positive Staphylococci in milk, food and other specimens and encourages the growth of a … Read moreMannitol Salt Agar (MSA)
Enterococcus faecalis and Enterococcus faecium Clinical Features Urinary tract infections, peritonitis, bacteremia, endocarditis Virulence Factors Relatively avirulent Staphylococcus aureus Clinical Features Suppurative infections: impetigo, folliculitis, furuncles, carbuncles, wounds Disseminated infections: bacteremia, endocarditis, pneumonia, empyema, osteomyelitis, septic arthritis Toxin-mediated infections: toxic shock syndrome, scalded skin syndrome, food poisoning Virulence Factors Possess thick peptidoglycan layer, capsule, protein … Read moreAerobic and Facultatively Anaerobic Gram-Positive Cocci
– Staphylococcus aureus on combined Mannitol Salt Agar and Vogel & Johnson Agar. – Photo By: Luis Alberto Pascual Santiago. – It is used for the selective isolation and differentiation of Staphylococcus aureus from clinical samples. – It forms yellow colonies with yellow zones. – Culture Media is still pink because this is combined media … Read moreStaphylococcus aureus on combined Mannitol Salt Agar and Vogel & Johnson Agar
– Staphylococcus aureus on Columbia CNA Agar with 5% Sheep Blood. – Photo By: Marlon Neris from Brasília, Brazil. – Columbia CNA Agar is recommended for use as a selective growth medium for the isolation and differentiation of gram-positive cocci from clinical and non-clinical specimens which contain mixed flora. – Large White to Cream Colonies … Read moreStaphylococcus aureus on Columbia CNA Agar with 5% Sheep Blood
Biochemical Test of Staphylococcus aureus Basic Characteristics Properties (Staphylococcus aureus) Capsule Non-Capsulated Catalase Positive (+ve) Citrate Positive (+ve) Coagulase Positive (+ve) Gas Negative (-ve) Gelatin Hydrolysis Positive (+ve) Gram Staining Positive (+ve) H2S Negative (-ve) Hemolysis Positive (+ve)- Beta Indole Negative (-ve) Motility Negative (-ve) MR (Methyl Red) Positive (+ve) Nitrate Reduction Positive (+ve) OF … Read moreBiochemical Test of Staphylococcus aureus
Virulence factors of Staphylococcus aureus A. Cell wall components Polysaccharide Capsule: inhibits phagocytosis Peptidoglycan: activates complement, IL-1, chemotactic to PMNs Teichoic acid: species specific, mediate binding to fibronectin Protein A: It binds to the Fc region of IgG and complement ,exerting an anti-opsonin effect. Fibronectin binding protein(FnBP): promote binding to ,mucosal cells and tissue matrices. … Read moreVirulence factors and Clinical manifestation of Staphylococcus aureus
Cultural characteristics of Staphylococcus aureus Staphylococci grow readily on most bacteriologic media under aerobic or microaerophilic conditions. Colonies on solid media are round, smooth, raised, and glistening. S. aureus usually forms gray to deep golden yellow colonies. Mannitol Salt Agar: circular, 2–3 mm in diameter, with a smooth, shiny surface; colonies appear opaque and are often … Read moreCultural and Biochemical characteristics of Staphylococcus aureus
Habitat and Morphology of Staphylococcus aureus Habitat Natural habitat is mammalian body surfaces. They are normal flora of skin and mucous membrane. Also present in nose / the anterior nares. They can also be found in Pharynx. Found in stratified epithelial cells or mucous or serum constituents associated with these cells. Found in skin/nasal passage … Read moreHabitat and Morphology of Staphylococcus aureus