Lecture 13 Staphylococci Staphylococci Gram positive stain purple o Have a PG layer on outside o Single membrane Clustered cocci bunch of grapes Opportunist Commensals on skin and upper respiratory tract Can grow in high salt conditions skin sweat glands salt Cannot dry out Can withstand UV from sun Tolerate heat up to 60 C for up to 60 mins Staphylococcus Aureus Gram positive Morphology Non motile Niche o Clustered Cocci bunches of grapes o Live mostly on skin and mucosa o Found on most individuals Reservoir Commensal o Yes Zoonosis Vector transmitted o No Opportunist o Possibly but mostly from human to human the body Has a capsule Most important virulence factors o Has a capsule VIP o Infections happen when skin or mucosa is broken and the organism can enter Slime layer on outside of cell helps to prevent phagocytosis Prevents cell wall made of PG from binding to TLRs on macrophages Allow the bacteria to bind to certain tissue types allowing them to o Adhesions stick around o Evasion of phagocytosis Physical evasion Production of enzymes that can protect against phagocytosis Production of toxins some o Protein A 1 virulence factor for S Aureus makes it the most dangerous Binds to FC constant region of IgG molecules prevents opsonization and blocking complement Coats Staph with human Ab so the immune system cannot recognize it Defense against phagocytosis S AUREUS ONLY o Has toxins Cytolytic toxins exotoxins secreted by bacteria and can interact w the environment Exfoliative toxins EFT dissolves desmosomes causing outer layer of skin to peel off Enterotoxins SE A G cause food poisoning and vomiting and diarrhea Toxic Shock Syndrome Toxin TSST o Has enzymes aka invasins KNOW Hyaluronidase Breaks down hyaluronic acid Leukocydin them Coagulase Destroys leukocytes phagocytes that are sent out to phagocytose Only found in S Aureus Helps the pathogen wall off the area of infection protecting against immune function cells Causes clotting of fibrin Helps to ID S Aureus from the other two types Kinase Catalase Dissolves clot produced by coagulase and releases bacteria so they can spread throughout the body Helps them survive in O2 environments o Can survive the respiratory burst of hydrogen peroxide All Staph species Superoxide dismutase Helps break down harmful oxygen molecules in cells o Fimbrial Ag Are they important Aerobic can survive in O2 environments Facultative anaerobes can ferment when air runs out Associated Diseases o Respiratory tract Pneumonia Infection of the lung o Causes drowning symptoms Alveoli become filled w fluid o Staph Aureus causes abscess formation in lungs of immunocompromised people Rare but highly fatal Sputum smear coughed up from LUNGS o Intestinal tract Toxic Shock Syndrome Rely tampons 1978 1980 Absorbent long lasting tampons perfect incubator for bacteria Certain strains of S Aureus release Toxic Shock Syndrome Toxin 1 TSST 1 o Superantigen can cross mucosa enter the bloodstream nonspecifically bind to the TCR on t cells Massive s of Macrophages and t cells are activated at the same time large amounts of cytokines being released o Results in septic shock with multiple organ failure Antibiotics did not help indicates that TSS was caused by possible death toxins not bacteria Staph Food Poisoning Staphylococcal Enterotoxins SE Local infection GI tract Group of toxins produced by some Staph species contaminate food Bacteria die in stomach acid toxin they release is acid stable and enters the blood stream Symptoms are produced by ingesting the toxin and not by the bacterial infection nausea extreme vomiting diarrhea headache sweating abdominal pain Most common type of food poisoning in the US SE Common in picnics and catering o Food becomes contaminated by improper hygiene of preparer bacteria grow in improperly refrigerated foods and release toxins person consumes food and becomes ill o Genital Urinary tract Bacteremia systemic DO NOT USE ANTIBIOTICS BC BACTERIA ARE NOT THE ISSUE TOXINS ARE THE ISSUE o Tx treat symptoms fluid iron replacement o Disease usually lasts 24 hours Enterotoxins are heat stable don t save and reheat the food Presence of bacteria in the blood Bacteria enter the blood stream from an area of infection and travel to other parts of the body which may become infected o Furuncles vaginal infections surgical wounds contaminated medical devices intravascular catheters and regular urinary catheters catheters are the most common cause Test for it using a blood culture takes a couple of days to come back risk of pt being dead by then o Treat aggressively Nosocomial infections account for about of the cases of Staph Bacteremia neglect at point of care Can lead to sepsis o Not as common in causing sepsis as Gram bacteria Systemic Staph Aureus colonizing growing inside the walls and valves of the heart o Heart valves receive no blood supply no protection o Once colonized by bacteria it grows quicky and valves from immune system quickly malfunction Pt start w flu like symptoms condition rapidly deteriorates as heart output drops Fatal in 50 of cases if not caught early enough o Cardiac Endocarditis o Skin lesions rash Impetigo Only involves epidermis outer layer of skin Contagious Produces blisters and sores mostly on the face sometimes the hands Common among children w poor hygiene Diffuse infection spreads over the skin Focused SA infections more important Folliculitis focused Localized infection of hair follicle Pus filled lumps that are tender warm and or painful o Boil should be drained under aseptic conditions Folliculitis of an eyelash stye usually not drained Furuncle Carbuncle focused Abscess larger than a boil usually found on the back of the neck local o Requires surgical draining acute round firm tender circumscribed Furuncle perifollicular Staph infection that usually presents as central pus area Carbuncle heads two or more confluent furuncles with separate o More widespread infection o Go deeper than the skin 1 step worse than furuncles Associated with acne in some cases hygiene problems also Staphylococcal Scalded Skin Syndrome SSSS Caused by endotoxin produced by some Staph Aureus strains Exfoliating toxins EFT o Proteases that digest specific proteins found in desmosomes special junctions that hold epiderm and derm together so skin can no longer be held together usually found in infants o toxins gain entry through infected umbilical stump involves large areas of skin often resembles 3rd degree burns no bacterial organisms can be