Department of
Department
of
Pathology:
Department
of
Pathology:
Department
of
Pathology:
Department
Pathology: of
Pathology:
Questioning Dogmas in
Microbiology
Paul C. Schreckenberger, Ph.D
Director, Clinical Microbiology Lab
University of Illinois at Chicago
pschreck@uic.edu
The University of Illinois at
Chicago Medical Center
– Urban Medical Ctr.
– 450 Bed Teaching
Hospital
– 400K Ambulatory
Visits
– 43 Ancillary
Departments
Broth Culture
• RULE: eliminate back-up broths except
for Tissue and CSF with shunts -?
• References:
– Morris AJ et al: JCM 33:161, 1995
– Derby P et al: JCM 35:1101, 1997
– Silletti RP et al: JCM 35:2003, 1997
– Sturgis CD et al. AJCP 108:217, 1997 - CSF
– Meredith FT et al. JCM 35:3109, 1997 - CSF
– Dunbar SA et al. JCM 36:1617, 1998 - CSF
Broth Culture
• Savings at UICMC - 1998
Direct Cost Savings
Wounds
- 3084 x .32 (EB) = $ 990
CSF
- 3114 x .32 (EB) =
996
Body fluid - 1905 x .32 (EB) =
610
Stools
- 1013 x .45 (GN, HE) = 456
$3,052
Broth Culture
• Savings at UICMC - 1998
Indirect Cost Savings
Did not have to set up or exam 9116 broth tubes
Did not report bogus findings leading to
additional testing or therapy of patients
Screening Sputum
• RULE: perform Gram stain and evaluate
under LPF (10 x). Reject if >10 SEC/LPF,
unless also see a predominant field of WBCs
assoc. with single morphotype of bacteria
Screening Sputum
• Cancel Culture, Charge for Gram Stain only
• DON’T REQUEST REPEAT CULTURE:
Add Comment: “specimen contaminated with
epithelial cells represents oropharyngeal
contamination further processing would yield
potentially misleading results.”
Screening Sputum
• References for using criteria of >10 SEC
to reject sputum:
1. Murray PR, Washington II JA: Mayo
Clinic Proc. 50:339-344, 1975
2. Wong LK et al: JCM 16:627-631, 1982
Screening Sputum
Sputum Quality Indicator UICMC
• Using criteria of >25 SEC/LPF
– Rejected 20% (range 8-33%) - 1/91-6/92
– QA monitor 12/95 showed rejection rate of 8%
• Using criteria of >10 SEC/LPF
– Rejected 39.4% (range 32-47%) - 1/96-5/97
– Current Rate 35.4% (range 29-53) - 1/99-12/99
Number of Respiratory
Specimens Accepted for Culture
1800
1600
1400
1200
1000
Sputum
Bronch
Trach
800
600
400
200
0
FY 94
FY 95
FY 96
FY 97
FY 98
FY 99
Screening Endotrachs
Endotrach Quality Indicator UICMC
• Using same criteria as sputum screen (>10 SEC)
– Reject avg. of 4.1% endotrach specimens
– For FY 98 rejected only 51 specimens
• Using criteria of >10 SEC + NOS on Gram stain
– Reject avg. of 25% of endotrach specimens
– For FY 98 would have rejected 372 specimens
Screening Endotrachs
• RULE: specimens with >10 SEC/LPF,
or no organisms seen on Gram stain
(or yeast only) are not cultured
• Reference:
– Morris AJ et al: JCM 31:1027, 1993
– Zaidi AK, Reller LB : JCM 34:352, 1996
– Rand KH: Diagn Micro Infect Dis 27:55, 1997
– Gilligan PH: Clin Micro Newsl 21:44, 1999
Endotrach Screening
Accept
Reject SEC
Reject LOC
150
100
50
0
Aug- Sep- Oct- Nov- Dec- Jan- Feb- Mar- Apr99
99
99
99
99
00
00
00
00
Assessing the Quality of Sputum
Specimens for AFB Culture
• Rejection criteria applied to bacterial cultures
based on presence of SEC should not be
applied to specimens for AFB culture
– Curion CJ et al:JCM 5:381, 1977
– Havlik D, Wood GL: Lab Med 26:411, 1995
– Isaac-Renton JL et al: AJCP 84:361, 1986
– Laird AT: JAMA 52:294, 1909
– McCarter YS, Robinson A: AJCP 105:769, 1996
– Pohl AD Keim AC: Lab Med 24:25, 1993
Assessing the Quality of Sputum
Specimens for AFB Culture
• Rule: Sputum Specimens Containing No
PMNs Are Not Routinely Smeared or
Cultured for AFB
– Laird AT: JAMA 52:294, 1909
– McCarter YS et al: AJCP 105:769, 1996
– Wilson M: AJCP 105:665, 1996
Correlation of PMN to AFB Positivity
McCarter and Robinson AJCP 1996
No. Specimens PMN Present PMN Absent
Total – 724
665 (91.9)
59 (8.1)
AFB smear
Pos – 51
AFB culture
Pos – 121
47 (92.2)
4 (7.8)
109 (90.1)
12 (9.9)
Correlation of PMN to AFB Positivity
McCarter and Robinson 1996
• Based on annual volume of 1378 Sputa
and absence of PMNs in 8.1%,
• Annual savings of $1,802.00 (based on
incremental costs of $3.55 for AFB
smear and $12.54 for AFB culture)
Guidelines for AFB Cultures
• General Order: first morning sputum x 3.
Accept only one specimen/day
• If first three concentrated smears negative
1. Must initiate consult with lab director
2. If patient is symptomatic, lab will
accept three more for up to a maximum of
six specimens
Guidelines for AFB Cultures
• Once three smears are positive
1. Stop accepting respiratory cultures for one
month to allow time for cultures to grow
2. Smear requests honored any time as
direct smears (not concentrated) until three
consecutive negatives are received
Guidelines for AFB Cultures
• Once cultures are positive
No new specimens for culture accepted for 1
month after date of positive culture
• References for No. of Sputum Necessary:
– Cascina A et al: JCM 38:466, 2000
– Nelson SM et al: JCM 36:467-469, 1998
– Divinagracia RM et al. Chest 114:681-684, 1998
– Peterson EM et al: JCM 37:3564-3568, 1999
Distribution of first positive specimen
in patients with >3 AFB specimens
Nelson S. et al. JCM 36:467, 1998
Collection
Order
st
1
2nd
rd
3
th
4 or later
Total
Culture
Pos
80(67)
33(28)
7(5)
0(0)
120
Smear
Pos
41(73)
8(14)
4(7)
3(6)
56
Smear
Neg
39(61)
22(34)
3(5)
0(0)
64
AFB Smear Results Among 43
Patients Culture Pos for MTB
Peterson et al. JCM 37:3564, 1999
Collection Concentrated
Direct
Order
Smear Pos Smear Pos
st
1
31(72.1)
24(55.8)
nd
2
4(9.3)
8(18.6)
rd
3
3(7.0)
2(4.7)
Total
38(88.4)
34(79.1)
Guidelines for Release from Isolation
• Patient Receiving effective chemotherapy
• Clinical Condition is improving
• Three consecutive sputum samples, collected
on different days are AFB-smear-negative
• References :
– Telzak EE, et al: Clin Infect Dis 25:666, 1997
– Iseman MD, et al: Clin Infect Dis 25:671, 1997
– MMWR 43(suppl RR-13):1-132, 1994
Stool Cultures
• RULE: Restrict culture and O&P exam to
outpatients and inpatients admitted <3 days
• RULE: Reject fungal culture on stools. Add
statement: “Fungal cultures of stool have not
been shown to be clinically useful.”
• Reference:
– Hines J, et al: Clin Infect Dis 23:1292, 1996
Stool Cultures - Additional Rules
• Use MacConkey instead of EMB, allows you to
screen for Yersinia without using CIN agar
• Eliminate enrichment broths except when
looking for asymptomatic carriers
• Eliminate serotyping of Salmonella and Shigella,
report presumptive result based on biochemical
ID, send organism to State Health Lab for typing
• Place limitations on AST of stool pathogens
Guidelines for Submitting
Stool for C. difficile
• Test should only be requested when following
criteria are met:
1. Antibiotic within 2 mos. prior to diarrhea
2. Diarrhea water/profuse: 6 episodes in 36h
3. Absence of other diagnosis for diarrhea
Stool for C. Difficile
Repeat Testing Criteria
• Negative results: Up to 3 stool specimens
(not more than 1 per day) tested per patient
• Positive results: after a positive test, further
testing only performed 7-10 days after
completion of therapy
Reference: Barenfanger J, Khardori N: Clin Micro
Newsl 18:142, 1996
Questioning Dogmas in
Microbiology
“Nearly all experts
agree that by the year
2000 bacterial and
viral disease will have
been wiped out”
-Time Magazine
February 25, 1966