Online Microbiology and Biology Study Notes
Image Source: ASM and Bacteria in Photos. Habitat of Staphylococcus aureus The natural habitat is mammalian body surfaces. They are normal flora of the skin and mucous membrane. Also present in the 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 …
Coagulase Test Definition A coagulase test is a biochemical test that is used to differentiate Staphylococcus aureus from other Staphylococci species like S. epidermidis and S. saprophyticus on the basis of the ability to produce the coagulase enzyme. The coagulase test is an important test that differentiates the species of the genus Staphylococci into two groups; Coagulase positive Staphylococci and …
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What is Catalase Test? The catalase test is a biochemical test for aerobic organisms that detects the production of catalase enzyme in the organism. Catalase enzyme is a common enzyme that is found in all living beings that survive in oxygen and catalyzes the decomposition of hydrogen peroxide, releasing water and oxygen. Catalase is an essential enzyme in pathogenic organisms …
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Biochemical reactions are very important in the identification of bacterial isolates and in the identification of different bacterial species. These tests depend on the presence of certain enzymes, such as catalase, oxidase, urease, gelatinase, etc., produced by the bacteria. Different bacteria produce varying spectra of enzymes. For example, some enzymes are necessary for the bacterium’s individual metabolism, and some facilitate …
Staphylococcus aureus are catalase-positive, gram-positive cocci which frequently colonize the skin and mucosa of humans and animals. However, it is a highly successful opportunistic pathogen and thus involved in various diseases including toxin-mediated diseases (food poisoning, toxic shock syndrome, scalded skin syndrome), pyogenic diseases (impetigo, folliculitis, furuncles, carbuncles, wound infections), and other systemic diseases. The species are characterized by the …
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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 differentiation agent. The medium allows the growth of Staphylococcus …
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 synthesis. The altered PBP2a of MRSA strains has less affinity …
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 group of certain bacteria while inhibiting the growth of …
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 A, various toxins (cytotoxins, exfoliative …
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– 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 of Mannitol Salt Agar and Vogel …
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