Staphylococci

• Staphylococcus saprophyticus is a frequent cause of cystitis in women, probably related to its occurrence as part of normal vaginal flora.
• Staphylococcus saprophyticus can be distinguished from Staphylococcus aureus and most other coagulase-negative staphylococci by its natural resistance to novobiocin.
• Staphylococcus epidermidis tends to be sensitive to most antibiotics, even penicillin G.
• Staphylococcus epidermidis is a frequent cause of cystitis in women, probably related to its occurrence as part of normal vaginal flora.
• Staphylococcus aureus produces an extracellular polysaccharide material called polysaccharide intercellular adhesin (“slime”), that facilitates adherence to bioprosthetic material surfaces, such as intravenous catheters, and acts as a barrier to antimicrobial agents.
• Staphylococcus saprophyticus tends to be sensitive to most antibiotics, even penicillin G.
• Gram Staining is a staining method using crystal violet (primary stain) & a counterstain – safranin or fuchsine.
• Gram Staining is used to distinguish and classify bacteria into Gram (+) or Gram (-) based on its peptidoglycan cell wall.
• Gram Staining was developed by Hans Christian Gram in 1884.
• Another portal of entry is the respiratory tract, such as staphylococcal pneumonia.
• Nosocomial infections are hospital-associated infections, often of wounds (surgical, decubital) or bacteremia associated with catheters.
• Staphylococcus aureus causes disease by infecting tissues, typically creating abscesses and/or producing toxins.
• Serious consequences occur when the bacteria invade the bloodstream, leading to septicemia, which is rapidly fatal.
• Localized host response to staphylococcal infection includes inflammation, accumulation of pus, and necrosis of tissue.
• Bacteremia, the presence of viable bacteria circulating in the bloodstream, may result in seeding internal abscesses, skin lesions, and infections in the lung, kidney, heart, skeletal muscle, or meninges.
• Deep, localized infections are metastatic from superficial infections and are the most common cause of acute and chronic bone marrow infection.
• Localized skin infections include small, superficial abscesses involving hair follicles (folliculitis) or sweat or sebaceous glands, such as sty (external hordeolum).
• A common entry point into the body is a break in the skin, which may be a minute needlestick or a surgical wound.
• Acute endocarditis is generally associated with IV drug abuse by injection of contaminated preparations or needles.
• Toxic shock syndrome is characterized by high fever, a rash ('sunburn', with diffuse erythema followed by desquamation), vomiting, diarrhea, hypotension, multiorgan involvement (GI, renal, and/or hepatic damage).
• Septicemia is a generalized infection with sepsis or bacteremia that may be associated with a known focus (for example, a septic joint) or not (an occult focus).
• Fibroblasts and their products may form a wall around the inflamed area, which contains bacteria and leukocytes, creating a characteristic pus-filled boil or abscess.
• Gram (+) bacteria stains dark violet (retains the Crystal Violet), while Gram (-) bacteria stains pink or red (retains the counterstain Safranin or Fuchsine).
• Staphylococcus epidermidis is present in large numbers as part of the normal flora of the skin and is frequently recovered from blood cultures, generally as a contaminant from skin.
• Staphylococcus aureus relies largely on microscopic and colony morphology and catalase positivite for identification.
• The bullae in Scalded skin syndrome may be infected or may result from toxin produced by organisms infecting a different site.
• Staphylococcus aureus is distinguished from the coagulase-negative staphylococci primarily by coagulase positivity.
• Despite its low virulence, Staphylococcus epidermidis is a common cause of infection of implants such as heart valves and catheters.
• Coagulase-negative Staphylococci are of 12 species recovered as normal commensals of human skin and anterior nares, with S. epidermidis being the most abundant and important.
• Staphylococcal gastroenteritis is caused by the ingestion of food contaminated with enterotoxin, which can be protein rich (egg salad or cream pastry) or salty, like ham, and is improperly refrigerated.
• Scalded skin syndrome is characterized by superficial bullae resulting from the action of an exfoliative toxin that attacks the intercellular adhesive of the stratum granulosum, causing marked epithelial desquamation.
• The symptoms of Staphylococcal gastroenteritis include nausea, vomiting, and diarrhea, which are acute and follow a short incubation period (< 6 hrs) because toxin in the food has already been formed before food is ingested.
• Staphylococcus epidermidis has acquired drug resistance even more frequently than S. aureus.
• The second most important coagulase-negative staphylococcus is S. saprophyticus.
• Coagulase-negative Staphylococci are important agents of hospital-acquired infections associated with the use of implanted prosthetic devices and catheters.
• Staphylococcus aureus is identified by staining strongly gram(+) and being frequently seen in grapelike clusters.
• Gram-variable or Gram-indeterminate bacteria have an unclear or no stain, such as Typhus bacillus.
• If there is no clumping in both slides, the test is negative for coagulase (+).
• Staphylococcus aureus is resistant to heat and drying, can persist for long periods on fomites, and its transmission can be decreased by frequent hand-washing before and after contact with food or potentially infected individuals.
• Disease caused by Staphylococcus aureus may be a combination of invasive infection and intoxication.