Lec1 Staph Infections PDF

CARDIOVASCULAR INFECTIONS STAPHYLOCOCCI BACTERIA By Reem Abdelrahman Lecturer of microbiology and immunology Faculty of medicine Helwan university  Lecture objectives: ¡ Identify main characters and and species of staphylococci group....

CARDIOVASCULAR INFECTIONS STAPHYLOCOCCI BACTERIA By Reem Abdelrahman Lecturer of microbiology and immunology Faculty of medicine Helwan university  Lecture objectives: ¡ Identify main characters and and species of staphylococci group. ¡ Recognize morphology and cultural characters of staph aureus. ¡ Understand virulence factors of staph aureus. ¡ Identify diseases caused by staph aureus. ¡ Differentiate between hospital acquired and community acquired staph aureus. ¡ Identify how to diagnose staph aureus infections. ¡ Identify staph aureus treatment and prevention. ¡ Recognize Staph.epidermidis and Staph saprophyticus properties.  STAPHYLOCOCCI general characters Staphylococci are gram positive cocci arranged in grape-like clusters. Staph, aureus Staph Staph epidermidis saprophyticus Coagulase positive. Coagulase negative. Mannitol positive Normal human microbiota. Causing haemolysis of Sometimes cause infections, often RBCs in vitro associated with implanted appliances and devices.  Staphylococcus aureus morphology and cultural characters: Morphology Cultural characters Shape: Facultative anaerobes cocci arrangement: on nutrient agar grape like clusters Stain: producing golden positive yellow colonies. Motility: non motile beta haemolytic Capsule: colonies on blood agar. non capsulated Spores: yellow colonies on non spore forming mannitol salt agar.  virulence factors: Cell wall components Enzymes and toxins Coagulase Protein A Clumping factor Techoic acid Catalase Exfoliative toxins Peptidoglycan Toxic shock syndrome toxin Polysaccharide Enterotoxins microcapsule Panton-Valentine leukocidin Heamolysins and other enzymes  Pathogenesis and virulence factors: I- cell wall components Protein A binds to the Fc portion of IgG at the complement binding site. preventing complement activation opsonization and phagocytosis of the organism is reduced Teichoic acid mediates its adherence to mucosal surfaces endotoxin-like properties Peptidoglycan microcapsule that is anti-phagocytic Polysaccharide  Pathogenesis and virulence factors: in A ote P r  Pathogenesis and virulence factors: II- toxins and enzymes Coagulase Clumping factor enzyme-like protein. is a surface compound causes coagulation of plasma with fibrin responsible for adherence (adhesin) of the deposition around the lesions as well as on the organism to fibrinogen and fibrin in plasma surface of staphylococci rendering them more leading to their aggregation and promoting resistant to phagocytosis their attachment to blood clots and traumatized tissues. invasive pathogenic potential It is immunogenic.  Pathogenesis and virulence factors: II- toxins and enzymes Catalase limits the ability of phagocytic cells to kill bacteria by degrading H2O2  Pathogenesis and virulence factors: II- toxins and enzymes Exfoliative toxins two distinct proteins A and B epidermolytic and cause the desquamation seen in staphylococcal "scalded skin syndrome" in young children. They are superantigens. genes for these toxins are located on a chromosomal element called a pathogenicity island  Pathogenesis and virulence factors: II- toxins and enzymes Toxic shock syndrome toxin This is produced by strains that cause the toxic shock syndrome. manifested by fever, diffuse macular rash, shock and multisystem involvement. Superantigen. genes for these toxins are located on a chromosomal element called a pathogenicity island  Pathogenesis and virulence factors: II- toxins and enzymes Enterotoxins multiple (A-E, G-J, K-R and U,V). produced by 50% o f Staph, aureus strains. The toxins are heat stable and resistant to the action of gut enzymes. They cause the diarrhea and vomiting associated with staphylococcal food poisoning. They act as superantigens. genes for these toxins are located on a chromosomal element called a pathogenicity island.  Pathogenesis and virulence factors: II- toxins and enzymes Panton-Valentine leukocidin produced mainly by community- acquired CA- MRSA. It is encoded on a mobile phage. It lysis leukocytes, releasing inflammatory mediators leading to necrosis and sever inflammation.  Pathogenesis and virulence factors: II- toxins and enzymes Heamolysins ,other exotoxins and other enzymes  Answer the following. ………………., ……………, ……Act as Characters of staphylococcal enterotoxin superantigens, and their genes carried on …………………………… chromosomal element called ………While genes........................................................ for ………………are carried on mobile phage. ……………………………….. Compare between coagulase and clumping factor Protein A action as virulence factor  Diseases caused by Staph, aureus: I -Pyogenic II.Toxigenic staphylococcal Diseases staphylococcal diseases: Focal Food poisoning suppuration Invasive Toxic shock conditions syndrome (TSS) Scalded skin Outbreaks syndrome:  Diseases caused by Staph, aureus: I- pyogenic staphylococcal diseases Focal suppuration abscess formation is characteristic of Staph, aureus lesions. This is due to coagulase which deposits fibrin around the lesions forming a wall, which is reinforced by inflammatory cells, e.g. folliculitis, carbuncles, boils and abscesses.  Diseases caused by Staph, aureus: I- pyogenic staphylococcal diseases Invasive from any focus or after trauma, organisms may conditions spread via the lymphatics or blood (bacteraemia) to other parts of the body causing deep seated lesions e.g. osteomyelitis, necrotizing pneumonia, empyema, endocarditis, meningitis, multiple abscesses in tissues and septicaemia.  Diseases caused by Staph, aureus: I- pyogenic staphylococcal diseases Outbreaks Outbreaks of hospital acquired post-operative wound infections commonly occur due to antibiotic resistant staphylococci. Foreign bodies, such as sutures and intravenous catheters predispose to these infections.  Diseases caused by Staph, aureus: II.Toxigenic staphylococcal diseases: ingestion of the preformed enterotoxin in contaminated food that is Food poisoning improperly cooked and kept unrefrigerated for some time. The source of contamination of food is the hands or the nose of a cook or food handlers (carriers). The type of food involved in staphylococcal food poisoning is carbohydrate rich food e.g. cakes, pastry, koskosi, koshari (popular Egyptian food) as well as milk and milk products. The incubation period is short (1-8 hrs) followed by nausea, vomiting, watery non-bloody diarrhoea and general malaise with no fever.  Diseases caused by Staph, aureus: II.Toxigenic staphylococcal diseases: Toxic shock This is associated with TSST-1. syndrome (TSS) TSS was first described in menstruating women using tampons. The syndrome also occurs with wound or localized infections. TSS has an abrupt onset of fever, vomiting, diarrhoea, muscle pains and rash. Hypotension, heart failure and renal failure may occur in severe cases. TSST-1 can be detected in the blood by ELISA  Diseases caused by Staph, aureus: II.Toxigenic staphylococcal diseases: Scalded skin It is due to the exfoliative toxin. syndrome: The syndrome occurs in babies and young children. It is characterized by large areas of desquamation of the skin and generalized bullae formation.  Answer the following. Clinical Symptoms of Staph food poisoning Staphylococcal toxic shock syndrome ………, …….,………… caused by ………… while scalded skin syndrome caused by ……………….. Toxigenic staphylococcal diseases ………, Pyogenic staphylococcal diseases ……… …….,…….. ……………., ………….  Differences between CA-MRSA and HA-MRSA CA-MRSA HA-MRSA less resistant More resistant Not hospitalized Hospitalized PVL No PVL More transmissible Less transmissible  Diagnosis specimens Smears Catalase Cultures production Coagulase Colony production Diagnosis identification Clumping factor Phage typing Typing methods for Antimicrobial epidemiological purposes susceptibility Molecular typing  Treatment and drug resistance: 90% of staphylococci are (VISA) or complete resistance to 65% of staphylococci resistant to B resistant to penicillin G, lactams vancomycin (VRSA) were ampicillin reported penicillin-binding protein (PBP2a) not due to production of B lactamase affected by these drugs. alteration in cell wall structure HA-MRSA treated by the beta lactamase The drugs of choice for these These strains are susceptible to resistant antibiotics such as organisms are the glycopeptides, i.e. linezolid. methicillin and oxacillin vancomycin  Treatment and drug resistance: te s N o ¡ Mupirocin is used as a topical antibiotic to reduce nasal carriage of the organism in hospital personnel and in patients with recurrent staphylococcal skin infections. ¡ resistanse to penicillin G, ampicillin and amoxicillin due to production of B lactamase (controlled by a plasmid) which breaks down the B lactam ring in penicillin. ¡ However resistance to methicillin, nafcillin and oxacillin is due to acquisition of a mecA gene that codes for a penicillin-binding protein (PBP2a) not affected by these drugs.  Prevention: ¡ There are no vaccines. ¡ Measures taken to control spread of staphylococcal infections including: Proper hygiene measures including, frequent hand washing. Aseptic management of lesions and proper disposal of bandages. Avoidance of sharing personal items such as towels and razors. Shared exercise equipment should be wiped down between users. ¡ Treatment of nasal carriers or their removal from high risk areas, e.g. operating rooms, intensive care units and newborn nurseries...etc.  D I S E R MI E P ID A P H GENERAL CHARACTERS S T ¡ Staph, epidermidis, present on normal skin and mucous membranes, ¡ It causes infections on top of prosthetic devices e.g. prosthetic valves or artificial joints and intravenous catheters.  VIRULENCE FACTORS ¡ A surface protein (adhesins) ¡ An exopolysaccharide (glycocalyx and slime) ¡ participate in its adherence ¡ lead to formation of a multi-layered biofilm on the surface of devices and valves, causing infections that are resistant to antibiotics.  DISEASES CAUSED: ¡ Most infections are hospital acquired affecting immunosuppressed patients. ¡ It is also a major cause of sepsis in neonates.  Morphology Cultural characters Shape: Facultative anaerobes cocci arrangement: on nutrient agar grape like clusters Stain: producing white positive colonies. Motility: non motile non haemolytic Capsule: colonies on blood agar. non capsulated Spores: pink colonies on non spore forming mannitol salt agar.  TREATMENT: ¡ Most strains produce ℬ -lactamase and many are methicillin/nafcillin resistant. ¡ The drug of choice is vancomycin to which gentamicin is added.  U S IC T Y PH ¡ Staph, saprophyticus is an opportunistic pathogen, RO P ¡ second to E. coli as a cause of urinary tract infection SA P H in sexually active young women. TA S ¡ Infection usually occurs 24 hr after intercourse. ¡ It produces urease which may play a role in its invasiveness in urinary tract infections. ¡ It is novobiocin-resistant while Staph, epidermidis is novobiocin-sensitive.  NOVOBIOCIN S.saprophyticus S.epidermidis Resistant Sensitive  is s en u n g d L u h. a p St ¡ Staph. Lugdunensis has emerged as a virulent organism causing disease similar to Staph, aureus.  Preventing complement activation, opsonization and phagocytosis are maintained by which Staphylococcal cell wall component? a. Techoic acid. b. Peptidoglycan. c. Protein A. d. Microcapsule. A family of four members had a delicious picnic lunch last Sunday. It was a warm day, and the food sat in the sun for several hours. 3 hours later, everyone came down with vomiting and nonbloody diarrhea. In the emergency room, it was found that the mother who prepared the food, had a paronychia on her thumb. Which one of the following is the most likely causative organism? a. Enterococcus faecalis. b. Staphylococcus aureus. c. Staphylococcus epidermidis. d. Streptococcus agalactiae. You’re in the clinical lab looking at a Gram stain when the laboratory technician comes up to you and says, “I think your patient has Staphylococcus epidermidis bacteremia.” Which one of the following sets of results did the tech find with the organism recovered from the blood culture? Gram-positive cocci in chains, catalase-positive, coagulase-positive Gram-positive cocci in chains, catalase-negative, coagulase-negative Gram-positive cocci in clusters, catalase-positive, coagulase-negative Gram-positive cocci in clusters, catalase-negative, coagulase-positive Superantigen production by Staphylococcus aureus is involved in the pathogenesis of which one of the following diseases? folliculitis bacteremia glomerulonephritis Toxic shock syndrome