Welcome to MICROnesia

1. Welcome to MICROnesia • 4 “Bug” Case Studies • “Life of a Blood Culture” Slide Show • Questions welcomed!

2. Case #1 UTI BUG • Ambulatory 26 year old female with 101° temperature and painful urination • Physician orders a urine culture with gram stain

3. Gram Stain Results • Gram stain morphology shows many gram-positive cocci in pairs and chains

4. Urine Culture Setup • Urine plated to agar plates • 1/1000 ml inoculating loop used • One big drop of urine is enough for a culture!

5. Urine Culture Results • Culture grows >100,000 colonies of bacteria on a blood agar plate • Patient’s UTI caused by a strep-like organism called Enterococcus

6. Identifying Enterococcus • Produces an enzyme called PYRase • Detectable in a two minute test

7. Normal sites for Enterococcus • Upper respiratory tract • Gastrointestinal tract • Genitourinary tract

8. Enterococcus Infections • UTI’s • Nosocomial UTI’s • Wound infections

9. Emerging Resistance • Emerging strains showing resistance to Vancomycin • Resistant strains called Vancomycin Resistant Enterococcus or VRE • Bone marrow transplant and other immunocompromised patients at risk

10. Identifying VRE • Identify VRE as an Enterococcus faecalis or faecium using biochemical tests interpreted by an automated instrument

11. Phoenix Automated Instrument • Performs both biochemical tests and susceptibilities • 100 organisms can be tested at a time

12. VRE on the rise • Enterococcus showing resistance to Vancomycin E-strip • VRE strains account for 6% of all Enterococcus • Patients placed in isolation • Reported to RN and Infection Control

13. Case #2 Wound Bug • 65 year old male with 101° temperature after hip replacement surgery • Develops redness, tenderness and drainage at incision site • Physician orders a culture and gram stain on incision site

14. Incision site Gram Stain • Gram stain shows few gram-positive cocci in clusters with few wbc’s

15. Bacterial culture results • Staph aureus isolated on culture • White colonies on blood agar

16. Identifying Staph aureus • Latex agglutination test can identify an organism as Staph aureus in 10 seconds

17. Staph aureus infections • Skin infections • Scalded Skin Syndrome • Toxic Shock Syndrome • Osteomyelitis • Food poisoning

18. Staph aureus reservoirs • Carried in nose of 20-40% of adults • Higher % in hospital personnel • Transferred from nose to skin • Passed to others by direct contact or droplets • Primary way nosocomial infections occur

19. Staph aureus treatment • Penicillin discovered in 1920 – worked great on Staph! • More difficult to treat the last 50 years • Some SA now showing resistant to methicillin, a commonly used drug

20. Identifying MRSA • Strains resistant to methicillin are called MRSA • Extraction test can identify SA as an MRSA strain in 15 minutes

21. Lots of MRSA • Up to 50% of SA isolated are MRSA strains • Carriage rate for MRSA higher in hospitals • MRSA often found on health club gym equipment • Pets can get MRSA from their owners

22. Wash Your Hands • Good handwashing essential! • Careful wound dressing technique • Patients with MRSA placed in isolation • Reported to RN and Infection Control

23. 38 year-old HIV positive male Several previous hospital admissions Taking AZT & Bactrim antibiotic therapy 3 day history of severe diarrhea with 10 pound weight loss and profound dehydration Case #3 GI BUG

24. Lab Results Stat • Leukotest = negative (test for fecal wbc’s) • Occult blood exam = negative • Both tests usually positive with diarrhea caused by Salmonella or Shigella • Negative Leukotest and Occult blood = noninflammatory diarrhea

25. Lab Results not Stat • Ova & Parasite exam negative • Stool culture negative for enteric pathogens • Campylobacter EIA assay negative • Shiga Toxin EIA assay negative

26. Other Findings • No recent travel history • Patient has not recently eaten shellfish

27. Clues from Patient History • Severe diarrhea consistent with enterotoxigenic E.coli or Vibrio cholerae • Endemic in limited regions • Raw or undercooked shellfish may contain Vibrio cholerae • Patient had not consumed shellfish

28. Suppressive Antibiotic Therapy • Normal gut flora protects the bowel from invasive pathogens • Antibiotics destroy large part normal flora • Allows overgrowth of organisms usually suppressed

29. Responsible Bug • Clostridium difficile frequently causes antibiotic-associated diarrhea • Disrupted normal flora allows C. difficile to multiply • Produces two different exotoxins

30. Patient’s Diagnosis • Patient suffering from Clostridium difficile colitis • “Pseudomembranous colitis”

31. More about Clostridium difficile • C. difficile is an anaerobe • Gram-positive rods on Gram Stain

32. Diagnosing C. difficile colitis • Detect exotoxins in stool using EIA assay • Performed twice daily in Microbiology • Takes about 3 hours • Pea-size amount of stool needed for testing • Positive results called to patient’s RN

33. Important to Establish Cause of Diarrhea • Many causes of diarrhea in AIDS patients untreatable • C. difficile treatable with oral antibiotics • Patient placed in isolation to avoid hospital outbreaks

34. Life of a BLOOD CULTURE Slide Show • Drawn in yellow-top SPS tubes • Full size & pedi-tube

35. Life of a BLOOD CULTURE • 4 Kinds of Blood Culture Bottles • Aerobic • Anaerobic • Pediatric • ARD (Antimicrobial Removal Device)

36. Life of a BLOOD CULTURE • Chlorhexidine preps or swabs disinfect venipuncture site • Scrub arm for 30 seconds, not to exceed a 2 inch square surface • Let arm air dry

37. Life of a BLOOD CULTURE • Use of Chlorhexidine preps has decreased blood culture contamination rate by 50% • Blood culture considered “contaminated” if common skin flora grows from one or both bottles in a set

38. Life of a BLOOD CULTURE • Clean SPS tubes with alcohol and let air dry • Draw 2 SPS tubes for each set of cultures • 10 ml in each tube • One tube –> aerobic • One tube –> anaerobic • Record collection site on label (peripheral, art line, etc.)

39. Life of a BLOOD CULTURE • Recommended draw times: • Two sets drawn at least 30 minutes apart in a 24 hour period • Bacterial recovery rate increases by 57% when 2 sets are drawn

40. Life of a BLOOD CULTURE • Bottles placed in an automated Bactec instrument • Incubate for 5 days • Monitored every 15 minutes for bacterial growth

41. Life of a BLOOD CULTURE • Loud alarm sounds when growth is detected! • Positive blood culture considered a STAT • Subcultured to agar plates • Plates incubate for 18 hours

42. Life of a BLOOD CULTURE • Gram stain slide made from “positive” bottle

43. Life of a BLOOD CULTURE • Gram Stain takes about two minutes • Look for bacteria on slide under the microscope • Gram stain results called to patient’s RN

44. Case #4 BLOOD BUG • 37 year old man with sickle cell disease and numerous hospitalizations • Porta-cath placed in right subclavian vein • Patient admitted to ED two weeks after porta-cath placement

45. Emergency Department findings • Patient has right arm discomfort and swelling • Physician orders two sets of blood cultures • One drawn through porta-cath • One drawn through peripheral vein

46. Blood culture results • Both sets of blood cultures show gram positive cocci in clusters on smear • Both cultures grow the same organism

47. Responsible Bug • Two positive blood cultures + porta-cath = probable line-related sepsis • Most common bug causing line-related infection is Coagulase Negative Staph or CNS • CNS  important cause of nosocomial bacteremia • Foreign body devices act as source

48. Identifying CNS • Grow as white colonies on blood agar plate • Nonreactive in rapid latex tests

49. Sources of CNS • Normal inhabitants of skin, mucous membranes and nares • About 20 species of CNS • Most common is Staph epidermidis

50. Slime Producers • CNS secrete a virulence factor called slime • Makes them “sticky” • Stick to plastic surfaces like catheter tips • Slime-producing strains more difficult to treat with antibiotics • Indwelling catheters place patient at risk for infection