Most pathogenic Staph cause infection after a breach in the skin. PrepTalk Clicker Questions. First Case - Lulu. Diagnostic information

Transcription

1 Most pathogenic Staph cause infection after a breach in the skin. PrepTalk Clicker Questions A. True B. False Did you Prep? Which factor is most strongly correlated with the virulence of pathogenic staphylococci? First Case - Lulu A. Superantigen B. Coagulase C. Fibrinolysin D. Enterotoxin E. Hemolysin Case: Lulu s Lips Diagnostic information Gram stain of colony St. Bernard 4-years-old Bad breath Painful, hyperemic sores on lips BAP 24 hr 1

2 What is the most probable pathogen causing this lipfold pyoderma? What is the most probable pathogen causing this lipfold pyoderma? A. Staphylococcus hyicus B. Staphylococcus epidermidis C. Staphylococcus aureus D. Staphylococcus intermedius Where did this infection most likely come from? A. Normal flora on Lulu s skin B. Another infected dog C. Contaminated dog food D. Lulu s owner E. Contaminated water bowl F. The darn cat! Key Elements of the Story Source = endogenous Predisposing factor: moisture = skin maceration Invasion & adherence Inflammation localized pain If untreated, can become chronic Acute inflammatory: neutrophils..pus S. intermedius factors: Protein A backward Ig binding Capsule antiphagocytic Coagulase hides bact. - coats with fibrin Hyaluronidase spreading factor More Key Elements of the Story Coagulase Testing Tube test 100% sensitive; Slide test is fast. Fibrinogen Penicillin resistance common penicillinase Diagnosis: culture Key test coagulase Tube test 3 37C Fibrin Slide test minutes at RT All coagulase-positive Staph = pathogenic Tube test is definitive; slide test is presumptive 2

3 Resisting Resistance Allows penicillin to remain active and exert its effect New Emerging Resistance Problem MRSA (methicillin resistant Staph aureus) 60% 50% Clavulanic acid blocks penicillinase Works based on structural similarity of penicillin and clauvulanic acid. % Resistant 40% 30% 20% 10% 0% Next case Ursula s Udder Swollen quarter High SCC Abnormal Diagnostic Information What is Your Diagnosis? 3

4 Which is most commonly associated with multiple cases of Staph mastitis in a dairy herd? Mastitis Staphylococcus aureus A. Poor hygiene at milking B. Purchase of infected cattle C. Sand bedding in freestalls D. Hot weather Key Elements of the Story Prevention & Control Identify infected cows by culture & milk them last Source = endogenous, endogenous, infected cow Predisposing factor: milking system Ascending infection Inflammation: acute or chronic Low-grade infections intermittent shedding Modest increase in SCC S. aureus factors: Protein A backward Ig binding Capsule antiphagocytic Coagulase hides bact. - coats with fibrin Hyaluronidase spreading factor Prevention & Control Dry cow treatment Antibiotic Therapy in Food Animal You MUST Consider Withdrawal Times Ceftiofur 3 rd generation cephalosporin Bacteriocidal vs Gram-pos & Gram-neg bacteria Witholding time = zero 4

5 Next case Case: Got Milk? No Got Sick! 14,000 people sick 98 hospitalized Diarrhea Vomiting Associated with drinking low-fat milk Some complained of strange smell in milk True Story Diagnostic information High numbers recovered from milk products Gram stain of colony What is Your Diagnosis? BAP 24 hr What Staph characteristics contribute to Staph food poisoning? Food Poisoning (more correctly food-borne intoxication) Staphylococcus aureus A. Staph grow well in high protein foods B. Staph are not inhibited by salt in foods C. Staph secrete a potent enterotoxin D. All of the above 5

6 Key Elements of the Story Source = post-pasteurization contamination Violation of sanitary practices Adequate time at ambient temp for S. aureus to grow Enterotoxigenic strain Ingestion of adequate dose of toxin NOT an infection Food-borne INTOXICATION Short incubation period (<12 hr) No need for bacterial growth in patient before onset of symptoms Factors Involved in Outbreak Workers at dairy plant were found recycling products returned by large-lot customers and unshipped products to make new batches. Cartons were opened manually with bare hands and poured into a storage vat for recycling. Food Safety Net, June 30 - July 15, Staph. aureus Enterotoxin 30% of Staph aureus strains can produce it. Staph grows well in high protein foods. Not inhibited by salt. Heat-stable protein toxin. Survives moderate cooking temperatures. Resistant to proteolytic enzymes. Survives passage through stomach. Induces nausea, vomiting, diarrhea. Humans more susceptible to toxin than animals. Other Staphylococcus Infections Similar pathogenesis details and/or less well defined pathogenesis. Exudative Epidermitis Sequence of Events 1. Trauma inoculates Strep hyicus (normal flora) 2. Bacteria adhere via fibronectin-binding proteins 3. Avoids phagocytosis Protein A Capsule 4. Secretion of exfoliative toxin 5. Host reaction + toxin effects cause massive exudation leading to dehydration and death. 6

7 Human Form of Disease Bumble Foot Summary Major Virulence Factors Name Changes in 2009 Protein A backward Ig binding Capsule 11 types; polysaccharides; antiphagocytic Coagulase hides bact. - coats with fibrin Hyaluronidase spreading factor Enterotoxins emesis (vomiting) in humans Toxic Shock Toxins = Superantigens hypotension Exfoliative toxin skin damage α Hemolysin / cytotoxin cell death or damage Old Staphylococcus aureus Staph aureus subsp. aureus (most common) Staph aureus subsp. anaerobius (rare; sheep abscess) Old Staph intermedius (coag-pos Staph from cats & dogs) Staph pseudintermedius (most common) Staph delphini Staph intermedius Name Changes in 2009 Old Staphylococcus aureus Staph aureus subsp. aureus (most common) Staph aureus subsp. anaerobius (rare; sheep abscess) Old Staph intermedius (coag-pos Staph from cats & dogs) Differentiation is very complex and not all that Staph pseudintermedius clinically relevant. (most common) Some labs or clinicians Staph delphini simply refer to Staph intermedius Group. Staph intermedius Methicillin-resistance can appear in any of these species. 7