STAPHYLOCOCCIy Definition: Gram +ve cocci

arranged in clusters. y All Catalase test +ve # y [ streptococci] . y All Oxidase negative # [Neisseria]

2

Gram positive cocci in clusters staphylococci

MSA

NA

BA

Pigmented golden yellow

White colonies

Pigmented colonies of staph on NA

Complete

(

)

Hemolytic staphylococci on BA

Hemolytic staphylococci on BA

Dont Ferment mannitol (red color )

Ferment mannitol ( yellow color )

Staphylococci on mannitol salt agar pathogenic (F+) non pathogenic(F-)

Staphylococci on mannitol salt agar pathogenic (F+)

Catalase +ve

Oxidase -ve

Differential CharacteristicsCatalase

Streptococci vs. Staphylococci

2H2O2

O2 + 2H2O

Catalase POS

Staphylococcus Catalase NEG

Differential CharacteristicsCoagulase

Fibrinogen

Fibrin

S. aureus

Staphylococcus aureus

Coagulase POS

Coagulase NEG

COAGULASE TEST

Staphylococci

Coagulase +ve (pathogenic)

Coagulase ve (non-pathogenic)

Staph. Staph. aureus epidermidis

Staph. saprophyticus

Difference between pathogenic and non pathogenicPathogenic 1- coagulase +ve Non-pathogenic 1- Coagulase ve.

Culture media

2- Pigmented golden yellow on NA 2- White colonies. 3- Haemolysis on BA. 4- Ferment mannitol on MSA . 3- No hemolysis on BA 4- Don not ferment mannitol.

Biochemical reactions of staphylococci

Coagulase +ve Mannitol fermentation +ve

Coagulase ve Mannitol fermentation ve

1-Novobiocin sensitive. * S. epidermidis. 2-Nov. resistant * S. saprophyticus.

Novobiocin testStaph epidermidis ---S Staph saprophytics ---R

Antigenic structureStaph. aureus has several cell wall components and antigens: 1Peptidoglycan polymer.

2Telchoic acids that mediate adherence of the organism to mucosal cells. 3Protein A: 90% of staph. aureus posses this antigen. It is antiphagocytic. Protein A binds IgG molecule nonspecifically through Fc portion leaving specific Fab sites free to combine with specific antigen. When suspension of such sensitized staphylococci is treated with homologous (test) antigen, the antigen combines with free Fab sites of IgG attached to staph cells leading to visible clumping of staphylococci within two minutes. It is known as coagglutination.

Antigenic structure4- Clumping factor: which binds to fibrinogen yielding aggregation of the bacteria. 5- Capsular polysaccharide: A few strains of staph. aureus are encapsulated and tend to be more virulent that non capsulated strains. 6- Surface receptors: for specific bacterial phages, permit phage typing for epidemiological purposes.

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Staphylococcal DiseaseRange from localized to systemic y Localized cutaneous infections invade skin through wounds, follicles, or glandsy folliculitis superficial inflammation of hair follicle;

usually resolved with no complications but can progress y furuncle boil; inflammation of hair follicle or sebaceous gland progresses into abscess or pustule y carbuncle larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles y impetigo bubble-like swellings that can break and peel away; most common in newborns27

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Nonbullous Lesions of Impetigo

Figure 21.4

Staphylococcal Diseasey Systemic infectionsy osteomyelitis infection is established in

the metaphysis; abscess forms y bacteremia primary origin is bacteria from another infected site or medical devices; endocarditis possible

30

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Bacterial Endocarditis

Figure 23.4

Staphylococcal Diseasey Toxigenic diseasey food intoxication ingestion of heat stable

enterotoxins; gastrointestinal distress y staphylococcal scalded skin syndrome toxin induces bright red flush, blisters, then desquamation of the epidermis y toxic shock syndrome toxemia leading to shock and organ failure

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Lesions of Skin Syndrome

Figure 21.5

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Staphylococcal Food PoisoningPathogen Symptoms Staphylococcus aureus Nausea, vomiting, and diarrhea Intoxication Enterotoxin (superantigen) Phage typing None

Intoxication/Infection

Diagnosis Treatment

Events in Staphylococcal Food Poisoning

Figure 25.6

Carriers of Staph. aureusImportance in hospital infection: yCarriage of staph. by medical personnel hospital infection (nosocomial infection of patients) or food poisoning. y Carriage in : i Nose. iHands. y Tracing the source of infection = (epidemiological study of the isolated strains)pphage typing. y Detection of carriers p nasal or skin swabpblood agar. pstaphp (identification).

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Phage typing

Phage Typing

Figure 10.13

Methicillin-resistant Staph.aureus (MRSA) Resistant to all beta lactam antibiotics. resistant to other drugs (aminoglycosides). s sensitive to vancomycin.

y y y

Other StaphylococciCoagulase-negative staphylococcus; frequently involved in nosocomial and opportunistic infections y S. epidermidis lives on skin and mucous membranes; endocarditis, bacteremia, UTI y S. saprophyticus infrequently lives on skin, intestine, vagina; UTI

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Coagulase-Negative Staphylococciy Staphylococcus epidermidis y S. saprophyticus

Novobiocin testStaph epidermidis ---S Staph saprophytics ---R

Staphylococcal Biofilms

Figure 21.3