STAPHYLOCOCCUS in hospital practice

1. STAPHYLOCOCCUSinhospital practice Dr.T.V.Rao MD Dr.T.V.Rao MD

2. Staphylococcus • Sir Alexander Ogston, a Scottish surgeon, first showed in 1880 that a number of human pyogenic diseases were associated with a cluster-forming micro-organism. He introduced the name 'staphylococcus' (Greek: staphyle = bunch of grapes; kokkos = grain or berry), now used as the genus name for a group of facultatively anaerobic, catalase-positive, Gram-positive cocci. Dr.T.V.Rao MD

3. Dr.T.V.Rao MD

4. INTRODUCTION • Staphylococci - derived from Greek “stapyle” (bunch of grapes) • Gram positive cocci arranged in clusters • Hardy organisms surviving many non physiologic conditions • Include a major human pathogen and skin commensals Dr.T.V.Rao MD

5. Staphylococci: Gram positive Cocci ( from Greek staphyle, means bunch of grapes ) that occur singly and in pairs, short chains and irregular grape-like clusters. Dr.T.V.Rao MD

6. Staphylococcus = nonmotile, grapelike clusters, nonsporeformers = nonencapsulated but few strains form capsules = aerobic or facultative anaerobes = catalase positive 2H202  2H20 + 02 = most strains --- heat stable (60oC x 30 mins.) SPECIES: Staphylococcus aureus coagulase ( + ) (clots citrated plasma) Staphylococcus epidermidis coagulase ( - ) TOXINS: hemolysins 6 enterotoxins Leukocidin exfoliatin Dr.T.V.Rao MD

7. Alexander Fleming Penicillin: is the antibiotic agent that Alexander Fleming a Scottish physician discovered in 1929. In 1950 only 15% of S.aureus was susceptible to penicillin. Approximately only 5% of S. aureus today are sensitive to penicillin. Dr.T.V.Rao MD

8. Classification • Family • Genus • Species Micrococcaceae Micrococcus and Staphylococcus S. aureus S. saprophyticus S. epidermidis M. luteus more than 20 species Dr.T.V.Rao MD

9. Structure and Physiology • Gram-positive cocci, nontitle, facultative anaerobes • Cells occur in grapelike clusters because cells division occurs along different planes and the daughter cells remain attached to one another • Salt-tolerant: allows them to tolerate the salt present on human skin • Tolerant of desiccation: allows survival on environmental surfaces (fomites) Dr.T.V.Rao MD

10. S. aureusA Unique Organism PVL Dr.T.V.Rao MD Adapted from: Lowy. N Engl J Med. 1998;339:520-532.

11. Structure and Physiology • Two species are commonly associated with staphylococcal diseases in humans • Staphylococcus aureus-The more virulent strain that can produce a variety of conditions depending on the site of infection • Staphylococcus epidermidis-Normal micro biota of human skin that can cause opportunistic infections in immunocompromised patients or when introduced into the body Dr.T.V.Rao MD

12. General Cultural Characteristics Staphylococcusspecies, most notably S. aureus, produce a hemolysis that completely lyses red blood cells of humans and some other mammals (sheep blood). This is referred to as “beta” hemolysis. Dr.T.V.Rao MD

13. Staphylococcus aureus: is the staphylococcus which has the ability to clot plasma, which is coagulase positive. More than 80% of Staphylococcus aureus strains produce beta-lactamases. Dr.T.V.Rao MD

14. Other S. aureus Characteristics Mannitol fermentation is another useful characteristic – it is unique to, and consistent among S. aureus strains. Virtually all strains of S. aureus ferment mannitol. Bright yellow colonies on a yellow background indicates mannitol fermentation on mannitol salt agar. Dr.T.V.Rao MD

15. Pathogenicity • “Staph’ infections result when staphylococci breach the body’s physical barriers • Entry of only a few hundred bacteria can result in disease • Pathogenicity results from 3 features • Structures that enable it to evade phagocytosis • Production of enzymes • Production of toxins Dr.T.V.Rao MD

16. Cell-Associated Virulence Factors • Capsule or slime layer (glycocalyx) • Peptidoglycan (PG) • Teichoic acid is covalently linked to PG and is species specific: • S. aureus ribitol teichoic acid (polysaccharide A) • S. epidermidis glycerol teichoic acid (polysaccharide B) • Protein A is covalently linked to PG • Clumping factor (bound coagulase) Dr.T.V.Rao MD

17. Virulence Factors Extracellular Enzymes • Coagulases (bound or free) • Antigenic • Hyaluronidase • “spreading factor” of S. aureus • Nuclease • Cleaves DNA and RNA in S. aureus • Protease • Staphylokinase (fibrinolysin) • Lipases • Esterase's Dr.T.V.Rao MD

18. Biochemical characteristic • Staphylococcus species can be differentiated from Micrococcus species based upon oxygen requirements: Staph is facultative and Micrococcus species are obligate aerobes Dr.T.V.Rao MD

19. Structural Defenses Against Phagocytosis • Protein A coats the cell surface • Interferes with humoral immune responses by binding to class G antibodies • Inhibits the complement cascade • Clumping Factor (Bound coagulase) • Converts the soluble blood protein fibrinogen in insoluble fibrin molecules that form blood clots • Fibrin clots hide the bacteria from phagocytic cells Dr.T.V.Rao MD

20. Virulence Factors: Exotoxins • Cytolytic (cytotoxins; cytolysins) • Alpha toxin - hemolysin • Reacts with RBCs • Beta toxin • Sphingomyelinase • Gamma toxin • Hemolytic activity • Delta toxin • Cytopathic for: • RBCs • Macrophages • Lymphocytes • Neutrophils • Platelets • Enterotoxic activity • Leukocidin Dr.T.V.Rao MD

21. Virulence Factors: Exotoxin • Enterotoxin • Exfoliative toxin (epidermolytic toxin) • Pyrogenic exotoxins Dr.T.V.Rao MD

22. Staphylococcal toxins Enterotoxins • Enterotoxins, types A-E, G, H, I and J, are commonly produced by up to 65% of strains of Staph. aureus, sometimes singly and sometimes in combination. These toxic proteins withstand exposure to 100°C for several minutes. Dr.T.V.Rao MD

23. Disease Manifestations • Boils, carbuncles Scalded skin syndrome Wound infection Pemphigus neonatroum Abscesses Toxic shock syndrome Impetigo Food poisoning Mastitis  Bacteraemia  Osteomyelitis Pneumonia  Endocarditis Dr.T.V.Rao MD

24. Clinical Manifestations/Disease • SKIN • folliculitis • boils (furuncles) • carbuncles • impetigo (bullous & pustular) • scalded skin syndrome • Neonates and children under 4 years Dr.T.V.Rao MD

25. A painful cluster of boils with a central well of pus, often found on the neck. take a long time to heal and often leave a scar. caused by infections of the skin Staphylococcus aureus Carbuncle Dr.T.V.Rao MD

26. Decubitus Ulcer or Bedsore Bedsores or pressure sores, local loss of skin and soft tissue as a result of pressure from prolonged bed rest. Also known as decubitus ulcers, bedsores common on the buttocks, and on bony points such as the heels, elbows, shoulders, and the back of the head. affect elderly or infirm people who are confined to bed for long periods, including comatose patients, whose condition prevents them from moving freely. Dr.T.V.Rao MD

27. Mastitis • Inflammation of the breast especially during nursing. • also a frequent site of both benign and malignant tumors. Dr.T.V.Rao MD

28. Meningitis Involving the covering of the brain & the spinal cord (meninges). Dr.T.V.Rao MD

29. Cystitis inflammation of the urinary bladder, usually from bacterial infection originating in the urethra, vagina, or, in the kidneys. Dr.T.V.Rao MD

30. most common form usually associated with adolescence but may also occur in adults. primarily from hormonal changes taking place in the body Other factors include stress, drugs, bacteria, and certain foodstuffs. Acne Vulgaris Dr.T.V.Rao MD

31. Skin lesions • Boils • Styes • Furuncles(infection of hair follicle) • Carbuncles (infection of several hair follicles) • Wound infections(progressive appearance of swelling and pain in a surgical wound after about 2 days from the surgery) • Impetigo(skin lesion with blisters that break and become covered with crusting exudate) Dr.T.V.Rao MD

32. Scalded skin syndrome (toxic epidermal necrolysis Dr.T.V.Rao MD

33. DEEP ABSCESSSES • Can be single or multiple • Breast abscess can occur in 1-3% of nursing mothers in puerperiem • Can produce mild to severe disease • Other sites - kidney, brain from septic foci in blood • Needs special investigations Dr.T.V.Rao MD

34. Pathology - predisposing factors • This list is virtually true for all pathogens • Immune system suppressed or otherwise compromised. Specifically… • Skin injuries (e.g. burns, surgical incisions, cuts, etc) • Presence of foreign bodies (e.g intravenous lines, prosthetic devices, sutures, tampons-) Dr.T.V.Rao MD

35. Pre-existing infections • Chronic underlying conditions (e.g. auto-immune conditions, malignancies, alcoholism, heart disease, etc.) • Compromised micro biota via antimicrobial therapy • Infants susceptible: oral, skin: impetigo, “scalded skin”, respiratory, other Dr.T.V.Rao MD

36. Pre-existing infections • With obvious focus • Osteomyelitis, septic arthritis • 2. No obvious focus • heart (infective endocarditis) • Brain(brain abscesses) • 3. Associated With predisposing factors • multiple abscesses, septicemia(IV drug users) • Staphylococcal pneumonia (Post viral) Dr.T.V.Rao MD

37. Frequent Contact Crowding Defense Offense Cleanliness Antimicrobial Use Contaminated Surfaces and Shared Items Compromised Skin Factors that Facilitate Transmission Dr.T.V.Rao MD

38. TOXIN MEDIATED DISEASES • 1. Staphylococcal food poisoning • Due to production of entero toxins • heat stable entero toxin acts on gut • produces severe vomiting following a very short incubation period • Resolves on its own within about 24 hours Dr.T.V.Rao MD

39. Toxic shock syndrome toxin (TSST-1) This was discovered in the early 1980s as a result of epidemiological and microbiological investigations in the USA of toxic shock syndrome, a multi-system disease caused by staphylococcal TSST-1 or enterotoxin, or both. A link was established with the use of highly absorbent tampons in menstruating women, although non-menstrual cases are now as common. The absence of circulating antibodies to TSST-1 is a factor in the pathogenesis of this syndrome. Dr.T.V.Rao MD

40. Toxic shock syndrome toxin (TSST-1) • TSST-1 and the enterotoxins are now recognized as super antigens, that is, they are potent activators of T lymphocytes resulting in the liberation of cytokines such as tumour necrosis factor, and they bind with high affinity to mononuclear cells. These characteristics partly explain the florid and multi-system nature of the clinical conditions associated with these toxins. Dr.T.V.Rao MD

41. Toxic shock syndrome • High fever, diarrhea, shock and erythematous skin rash which desquamate • Mediated via ‘toxic shock syndrome toxin’ • 10% mortality rate • Described in two groups of patients • ass. With young women using tampons during menstruation • Described in young children and men Dr.T.V.Rao MD

42. Enzymes • Coagulase • Triggers blood clotting • Hyaluronidase • Breaks down hyaluronic acid, enabling the bacteria to spread between cells • Staphylokinase • Dissolves fibrin threads in blood clots, allowing Staphylococcus aureus to free itself from clots Dr.T.V.Rao MD

43. Enzymes (cont.) . Lipases • Digest lipids, allowing staphylococcus to grow on the skin’s surface and in cutaneous oil glands 5.-lactamase • Breaks down penicillin • Allows the bacteria to survive treatment with -lactam antimicrobial drugs Dr.T.V.Rao MD

44. Toxins • Staphylococcus aureus produces toxins more frequently than S.epidermidis 1. Cytolytic toxins • Disrupts the cytoplasmic membrane of a variety of cells • Leukocidin can lyse leukocytes specifically 2. Exfoliative toxins • Causes the patient’s skin cells to separate from each other and slough off the body Dr.T.V.Rao MD

45. Food poisoning • S. aureusis the #1 most common cause of food poisoning although it is comparatively mild in most cases. • Symptoms include nausea, vomiting, diarrhea, abdominal cramping and mild fever. • Symptom onset can be within minutes or hours of ingestion, with similar duration • Foods: handled foods: wet, sugary or salty, handled after some preparation – cooked, mixed, then served cold, at least initially Dr.T.V.Rao MD

46. Coagulase • Coagulase (staphylocoagulase) is a fibrinogen activating enzyme produced by some staph species - it has thrombin-like activity. In situ, coagulase combines with “coagulase reacting factor” (CRF) to catalyze the formation of fibrin clots around cells as a barrier to host immune components – it is a virulence factor. • Clinically significant staphylococci are usually divided into two groups: those that produce coagulase and those that do not • Coagulase positivespecies include S. aureus, S. intermedius and S. hyicus • S. intermedius and S. hyicus mostly inhabit animals and are only rarely found as a cause of human infections Dr.T.V.Rao MD

47. Coagulase testing • The tube is observed hourly during the four hour incubation period • The formation of a fibrin clot or gel indicates a positive test Dr.T.V.Rao MD

48. Clusters of USA300 isolates with multiple resistance to erythromycin, clindamycin, tetracycline, ciprofloxacin, and mupirocin1 Resistance to ≤ one class of antibiotics other than beta-lactams is still the most common resistance pattern in MRSA USA300 TMP/SMX resistance rare in MRSA USA300 Emerging Multi-Drug Resistance in USA300? 1Diep et al Lancet 2006. Han et al J Clin Micro 2007. Dr.T.V.Rao MD

49. Beta lactams: Beta lactams:are the antibiotics that contain the beta lactam ring. These are : penicillins, cephamycins, cephalosporins, carbapenems monobactams. The ring structure is common to all beta-lactams and must be intact for antibacterial action. They are cell wall synthesis inhibitors. Dr.T.V.Rao MD

50. MRSA culture in outpatient setting or 1st 48 hours of hospitalization AND patient lacks risk factors for healthcare-associated MRSA: Hospitalization Surgery Long-term care Dialysis Indwelling devices Community-Associated MRSA:CDC Population-Based Surveillance Definition Dr.T.V.Rao MD