Staphylococcus

Staphylococus aureus routes of transmission

Inhalation - aerosols Direct contact Ingestion of preformed toxin Endogenous

What to use for non-beta-lactamase producing S. aureus (methicillin-susceptible)

Penicillinase-resistant synthetic penicillins: methicillin, nafcillin, oxacillin, dicloxacillin

Staphylococcus transmission

Person to person Self - colonizing,strain gains entrance through trauma or wound Directly through surgical procedures

Stomatococcus

Rarely clinically significant

Treatment of Staphylococcus aureus

Wound drainage Pull indwelling device Antimicrobial agents: Penicillin Erythromycin Vancomycin Discontinue antibiotics Enterocolitis only

Toxin production of Staphylococus aureus

Alpha toxin Hemolyzes red cells, destroys platelets, kills leukocytes, and causes necrosis of skin (dermonecrosis) Leukocidin or Panton-Valentine factor Lethal to PMN's by partially disrupting their membranes Component most responsible for production of pus in Staph infections Enterotoxins Ingestion of food containing one of these preformed enterotoxins results in staphylococcal food poisoning Exfoliatinsoxins An exotoxin that leads to separation and loss of the most superficial layers of the epidermis Toxic Shock Syndrome Toxin (TSST-1) Appears to be capable of producing widespread organ damage through other yet poorly defined mechanisms - end result of which is toxic shock.C

Types of virulence factors

Anatomical Toxin production Enzyme production

biochemical tests for staphylococcus

Catalase Oxidativ-fermentations of carbohydrates (turns media from green to yellow) mannitol fermentative (S. aureus ONLY) Coagulase (S. aureus ONLY) Novobiocin susceptibility

Deep lesions of Staphylococus aureus

Cellulitis Osteomyelitis Disease of growing bones - occurs in children under 12 Arthritis Organ tissue abscesses Endocarditis common in intravenous drug users Pneumonia Enterocolitis Manifestations include high fever and profuse diarrhea - can be life threatening Infection of wounds S. aureus major cause of wound infections

Predisposing conditions that can cause stapylococcus infection

Chronic infections • Indwelling devices • Skin injuries • Immune response defects

Types of Staphylococus aureusdiseases

Cutaneous infection Deep lesions Disease due to toxin production

Describe coagulase test

Detects enzyme coagulase cell-bound "clumping factor" converts fibrinogen to fibrin extracellular enzyme "free coagulase" thrombokinase-like acton clots fibrinogen in the presence of plasma

Methicillin-resistant Staphylococcus aureus (MRSA)

Due to presence of mec gene Alters the site at which methicillin binds to kill the bacteria Causes the same infections as susceptible bacteria Can colonize a host without causing illness (increasing transmission)

Cutaneous Staphylococus aureus infections

Folliculitis • Inflammatory condition of a hair follicle Furuncle (boil) • A superficial infection that develops in a hair follicle, sebaceous gland, or sweat gland - deeper than in folliculitis Carbuncle • Spread of furuncle to subcutaneous tissues with development of one or more abscesses Impetigo • Acute and highly communicable • Characterized by large blisters in superficial layers of skin Seen most often in infants and children

S. aureus epidemiology

Found Worldwide colonizes anterior nares and sometimes other skin sites about 30% of population are persistent carriers 20-30% of population are intermittent carriers up to 60% are non-carriers - carrier rate may be higher in hospitals considered normal flora of intestine Most common in hospitals and nursing homes Usual sites of colonization are nostrils, skin, groin and wounds

Micrococcus

Free living saprophytes

Microscopic examination of staphylococcus

Gram positive cocci Pairs and clusters Numerous polymorphonuclear cells

Staphyloccocus common reservoirs

Health-care staff Patients Inanimate objects

Hemolysin toxins

Hemolyzes RBCs Alpha: platelets/WBCs/tissue Beta: sphingomyelin of RBCs GammaL host cell membranes Delta: less lethal

Staphylococus aureus extracellular enzymes

Hyaluronidase: Connective tissue, enhance invasion and survival in tissues Staphylokinase: Fibrinolysin Coagulase: Virulance marker Lipase: Allows colonization Penicillianse: Confers resistance

Current and Future Concerns of staphylococcus aureus

Increasing frequency Community-acquired MRSA Resistance to a wider range of antibiotics VISA strains: vancomycin intermediate susceptibility S. aureus

Organisms similar to Staphylococcus

Micrococcus Planococcus Stomatococcus

Anatomical features to diagnose staphylococcus

Non motile No spores

Characteristics of Staphylococcus

Normal flora of the skin and mucous membrane Asymptomatic, chronic carriage 32 species gram positive cocci clusters (can be in singles or pairs) Non-motile Non-spore forming Non-fastidious facultative anaerobe yellow or white colonies w/ regular conves morphology Catalase positive

Planococcus

Not clinically significant

Coagulase-positive staphylocci

S. aureus - Human Pathogen Animal species S. intermedius S. hyicus S. delphini S. schleiferi

Less common staph species to cause disease

S. hemolyticus S. hominis S. simulans

Novobiocin response in Staph

Sensitive: All other Staph spp resistant: S. saprophyticus

Types of Staphylococus aureus clinical infections

Skin and wound Food poisoning scalded skin syndrome Toxic shock syndrome Respiratory Bacterima Osteomyelitis

Cultural characteristics of Coagulase negative staphylococci

Smooth, creamy, white small-to-medium sized usually non-hemolytic

Diseases caused by toxin production of Staphylococcus aureus:

Staphylococcal Scalded Skin Syndrome Exfoliatin-producing strains Most common in young children Food Poisoning Foods commonly involved are meats, salads, creams Vomiting or diarrhea Incubation period = 1 - 5 hours Duration = 1 -3 days Toxic Shock Syndrome Most common in young women Causes fever, vomiting, diarrhea, sore throat and muscle pain Can lead to hypotension and organ damage TSST-1 toxin release

Most common staph species to cause disease

Staphylococcus aureus Staphylococcus epidermidis Staphylococcus saprophyticus

Most common CNS isolated

Staphylococcus epidermidis

Non routine tests for Staph

TSST-1 production Serology Phage typing DNA probes

Anatomical features of Staphylococus aureus

Teichoic acid: component of cell wall that mediates adherence of organism to host and contributes to initiation of infection • Protein A: coats surface of aprox. 90% Staph. aureus strains o Has strong affinity for Fc portion of IgG molecules o blocks phagocyte receptor sites on IgG molecules inhibiting phagocytosis

Characteristics of Staphylococcus aureus

The most virulent Staphylococcus species The only human Staph species that produces coagulase The most common species of Staph involved in human infections Common cause of necrotic skin infections and abscesses Tolerant to high salt concentrations Ferments mannitol Hemolysis (beta-hemolytic)

Genus Staphylococcus

resemble members of Micrococcaceae family 14 to 17 species associated with humans Several veterinary pathogens Key test to differentiate species is the coagulase test

Colony morphology of staphylococcus

small, white to yellowish, CREAMY S.aureus may produce hemolysis on blood agar

Cultural characteristics of S. saprophyticus

smooth, creamy, may produce a yellow pigment usually not hemolytic

Describe the catalase test

tests for enzyme catalase H2O2------->H2O + O2 bubbling = positive No bubbling - Negative ( streptococci and other lactic acid bacteria, no @s generated)

What to use for methicillin -resistant S. aureus (MRSA) and methicillin-resistant S. epidermidis (MRSE)

vancomycin combined with rifampin or gentamicin

characteristics of Coagulase-negative staphylocci (CNS)

• Habitat o Skin and mucous membranes • Approximately 35 species • Common human isolates o S. epideremidis, S. saprophyticus, S. haemolyticus • Less virulent than S. aureus • Common nosocomial infections • Usually involved with implantation of medical devices • Ubiquitous • Normal flora o usually contaminants in clinical specimens

Staphylococcus epidermidis epidemiology

• Habitat: skin and mucous membranes • Cell wall: glycerol-teichoic acids • Virulence factor: "slime" • Mode of transmission: implantation of medical devices such as catheters, shunts, and prosthetic devices • Infections are acquired nosocomially • Serious infections among immunosuppressed patients may occur

Staphylococcus saprophyticus epidemiology

• Habitat: skin and mucous membranes • Cell wall: glycerol-teichoic acids • Virulence factor: "slime" • Mode of transmission: implantation of medical devices such as catheters, shunts, and prosthetic devices • Infections are acquired nosocomially • Serious infections among immunosuppressed patients may occur

diseases caused by Staphylococcus epidermidis

• Nosocomial infections particularly in immunocompromised or neutropenic patients Associated with implantation of prosthetic devises • Endocarditis seen most commonly in drug addicts • Bacteremia (contamination) Must show repeated isolation Usually occurs is extremely compromised individuals can be life threatening

Common human isolates that are CNS

• S. epidermidis Nosocomial infections Endocarditis bacteremia • S. saprophyticus Urinary tract infections (UTI)

Other gram-positive cocci

• S. haemolyticus associated with wound infections, bacteremia, and endocarditis • S. lugdunensis and S. schleiferi are also found to be opportunists • Habitat: skin and mucous membranes • Rarely implicated in infections

Treatmentss of CNS

• Wound drainage • Pull line (line sepsis) • Antimicrobics o erythromycin or vancomycin used when patient allergic to penicillin or when organism is resistant to penicillin • Discontinuation of antimicrobial therapy (enterocolitis only)