Welcome to MICROnesia

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Welcome to MICROnesia

• 4 Bug Case Studies
• Life of a Blood Culture Slide Show
• Questions welcomed!

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Case 1 UTI BUG

• Ambulatory 26 year old female with 101
  temperature and painful urination
• Physician orders a urine culture with gram stain

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Gram Stain Results

• Gram stain morphology shows many gram-positive
  cocci in pairs and chains

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Urine Culture Setup

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

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Urine Culture Results

• Culture grows gt100,000 colonies of bacteria on a
  blood agar plate
• Patients UTI caused by a strep-like organism
  called Enterococcus

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Identifying Enterococcus

• Produces an enzyme called PYRase
• Detectable in a two minute test

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Normal sites for Enterococcus

• Upper respiratory tract
• Gastrointestinal tract
• Genitourinary tract

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Enterococcus Infections

• UTIs
• Nosocomial UTIs
• Wound infections

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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

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Identifying VRE

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

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Phoenix Automated Instrument

• Performs both biochemical tests and
  susceptibilities
• 100 organisms can be tested at a time

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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

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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

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Incision site Gram Stain

• Gram stain shows few gram-positive cocci in
  clusters with few wbcs

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Bacterial culture results

• Staph aureus isolated on culture
• White colonies on blood agar

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Identifying Staph aureus

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

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Staph aureus infections

• Skin infections
• Scalded Skin Syndrome
• Toxic Shock Syndrome
• Osteomyelitis
• Food poisoning

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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

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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

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Identifying MRSA

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

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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

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Wash Your Hands

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

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Case 3 GI BUG

• 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

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Lab Results Stat

• Leukotest negative (test for fecal wbcs)
• Occult blood exam negative
• Both tests usually positive with diarrhea caused
  by Salmonella or Shigella
• Negative Leukotest and Occult blood
  noninflammatory diarrhea

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Lab Results not Stat

• Ova Parasite exam negative
• Stool culture negative for enteric pathogens
• Campylobacter EIA assay negative
• Shiga Toxin EIA assay negative

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Other Findings

• No recent travel history
• Patient has not recently eaten shellfish

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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

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Suppressive Antibiotic Therapy

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

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Responsible Bug

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

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Patients Diagnosis

• Patient suffering from Clostridium difficile
  colitis
• Pseudomembranous colitis

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More about Clostridium difficile

• C. difficile is an anaerobe
• Gram-positive rods on Gram Stain

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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 patients RN

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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

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Life of a BLOOD CULTURE Slide Show

• Drawn in yellow-top SPS tubes
• Full size pedi-tube

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Life of a BLOOD CULTURE

• 4 Kinds of Blood Culture Bottles
• Aerobic
• Anaerobic
• Pediatric
• ARD
• (Antimicrobial Removal Device)

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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

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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

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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 gt aerobic
• One tube gt anaerobic
• Record collection site on label
• (peripheral, art line, etc.)

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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

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Life of a BLOOD CULTURE

• Bottles placed in an automated Bactec instrument
• Incubate for 5 days
• Monitored every 15 minutes for bacterial growth

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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

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Life of a BLOOD CULTURE

• Gram stain slide made from positive bottle

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Life of a BLOOD CULTURE

• Gram Stain takes about two minutes
• Look for bacteria on slide under the microscope
• Gram stain results called to patients RN

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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

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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

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Blood culture results

• Both sets of blood cultures show gram positive
  cocci in clusters on smear
• Both cultures grow the same organism

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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

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Identifying CNS

• Grow as white colonies on blood agar plate
• Nonreactive in rapid latex tests

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Sources of CNS

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

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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

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Diagnosing Line-Related Sepsis

• Draw 2 sets of blood cultures from a patient with
  fever or signs of infection at the IV site
• One set from catheter line
• One set from peripheral site

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Two sites important

• CNS on skin can be a blood culture contaminant
  if blood not collected properly
• Single positive blood culture with CNS may be
  skin contamination and not true infection

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Two sites important

• Negative peripheral culture and positive line
  culture with CNS may just show local infection of
  the catheter site
• Two Blood cultures with CNS from two different
  sites more likely represents true infection

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Confirming line-related sepsis

• Confirm by performing a catheter tip culture
• Catheter is removed and sent to Micro Lab

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Culturing the Catheter tip

• Catheter tip cut to 50mm
• Roll on surface of blood agar plate

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Interpreting Catheter tip cultures

• Culture positive if 15 colonies grow from a 50
  mm tip
• CNS growing on plate

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Diagnosis confirmed

• If Catheter tip culture has CNS and blood
  cultures from both the line and peripheral draws
  have CNS ?
• Patient has a confirmed line-related sepsis

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Microbiology Art

• Thank you!
• Please call Microbiology with any questions
• 2-2422
• 2-2435