Micronesia Case Study #2

Report
Welcome to MICROnesia
4 “Bug” Case
Studies
 “Life of a Blood
Culture” Slide
Show
 Questions
welcomed!

Case #1 UTI BUG
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Ambulatory 26 year old female with 101°
temperature and painful urination
Physician orders a urine culture with gram
stain
Gram Stain Results
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Gram stain
morphology shows
many gram-positive
cocci in pairs and
chains
Urine Culture Setup
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Urine plated to agar
plates
1/1000 ml inoculating
loop used
One big drop of urine is
enough for a culture!
Urine Culture Results
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Culture grows >100,000
colonies of bacteria on a
blood agar plate
Patient’s UTI caused by
a strep-like organism
called Enterococcus
Identifying Enterococcus
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Produces an enzyme
called PYRase
Detectable in a two
minute test
Normal sites for Enterococcus
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Upper respiratory tract
Gastrointestinal tract
Genitourinary tract
Enterococcus Infections
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UTI’s
Nosocomial UTI’s
Wound infections
Emerging Resistance
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Emerging strains showing resistance to
Vancomycin
Resistant strains called Vancomycin Resistant
Enterococcus or VRE
Bone marrow transplant and other
immunocompromised patients at risk
Identifying VRE
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Identify VRE as an
Enterococcus
faecalis or faecium
using biochemical
tests interpreted by
an automated
instrument
Phoenix Automated Instrument
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Performs both
biochemical tests
and susceptibilities
100 organisms can
be tested at a time
VRE on the rise
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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
Case #2 Wound Bug
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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
Incision site Gram Stain
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Gram stain shows few
gram-positive cocci in
clusters with few wbc’s
Bacterial culture results
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Staph aureus isolated
on culture
White colonies on blood
agar
Identifying Staph aureus
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Latex agglutination
test can identify an
organism as Staph
aureus in 10
seconds
Staph aureus infections
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Skin infections
Scalded Skin Syndrome
Toxic Shock Syndrome
Osteomyelitis
Food poisoning
Staph aureus reservoirs
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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
Staph aureus treatment
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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
Identifying MRSA
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Strains resistant to
methicillin are called
MRSA
Extraction test can
identify SA as an
MRSA strain in 15
minutes
Lots of MRSA
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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
Wash Your Hands
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Good handwashing
essential!
Careful wound dressing
technique
Patients with MRSA
placed in isolation
Reported to RN and
Infection Control
Case #3 GI BUG
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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
Lab Results Stat
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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
Lab Results not Stat
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Ova & Parasite exam negative
Stool culture negative for enteric pathogens
Campylobacter EIA assay negative
Shiga Toxin EIA assay negative
Other Findings
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No recent travel history
Patient has not recently eaten shellfish
Clues from Patient History
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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
Suppressive Antibiotic Therapy
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Normal gut flora protects the bowel from
invasive pathogens
Antibiotics destroy large part normal flora
Allows overgrowth of organisms usually
suppressed
Responsible Bug
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Clostridium difficile frequently causes
antibiotic-associated diarrhea
Disrupted normal flora allows C. difficile to
multiply
Produces two different exotoxins
Patient’s Diagnosis
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Patient suffering from Clostridium difficile colitis
“Pseudomembranous colitis”
More about Clostridium difficile
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C. difficile is an
anaerobe
Gram-positive
rods on Gram
Stain
Diagnosing C. difficile colitis
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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
Important to Establish Cause of Diarrhea
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Many causes of diarrhea in AIDS patients
untreatable
C. difficile treatable with oral antibiotics
Patient placed in isolation to avoid hospital
outbreaks
Life of a BLOOD CULTURE Slide Show
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Drawn in yellow-top
SPS tubes
Full size & pedi-tube
Life of a BLOOD CULTURE
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4 Kinds of Blood Culture
Bottles
Aerobic
Anaerobic
Pediatric
ARD
(Antimicrobial Removal
Device)
Life of a BLOOD CULTURE
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Chlorhexidine preps or
swabs disinfect
venipuncture site
Scrub arm for 30
seconds, not to exceed a
2 inch square surface
Let arm air dry
Life of a BLOOD CULTURE
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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
Life of a BLOOD CULTURE
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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.)
Life of a BLOOD CULTURE
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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
Life of a BLOOD CULTURE
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Bottles placed in an
automated Bactec
instrument
Incubate for 5 days
Monitored every 15
minutes for bacterial
growth
Life of a BLOOD CULTURE
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Loud alarm sounds
when growth is detected!
Positive blood culture
considered a STAT
Subcultured to agar
plates
Plates incubate for 18
hours
Life of a BLOOD CULTURE

Gram stain slide
made from “positive”
bottle
Life of a BLOOD CULTURE
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Gram Stain takes
about two minutes
Look for bacteria on
slide under the
microscope
Gram stain results
called to patient’s RN
Case #4 BLOOD BUG
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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 portacath placement
Emergency Department findings
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Patient has right arm discomfort and swelling
Physician orders two sets of blood cultures
One drawn through porta-cath
One drawn through peripheral vein
Blood culture results
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Both sets of blood
cultures show gram
positive cocci in
clusters on smear
Both cultures grow
the same organism
Responsible Bug
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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
Identifying CNS
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Grow as white colonies
on blood agar plate
Nonreactive in rapid
latex tests
Sources of CNS
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Normal inhabitants of skin, mucous
membranes and nares
About 20 species of CNS
Most common is Staph epidermidis
Slime Producers
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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
Diagnosing Line-Related Sepsis
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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
Two sites important
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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
Two sites important
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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
Confirming line-related sepsis
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Confirm by performing a catheter tip culture
Catheter is removed and sent to Micro Lab
Culturing the Catheter tip
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Catheter tip cut to 50mm
Roll on surface of blood
agar plate
Interpreting Catheter tip cultures
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Culture “positive” if
15 colonies grow
from a 50 mm tip
CNS growing on
plate
Diagnosis confirmed
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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
Microbiology Art
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Thank you!
Please call Microbiology
with any questions:
2-2422
2-2435

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