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Case-Control Investigation of a DrugResistant Acinetobacter baumannii
Outbreak at a Regional Medical Center
in Eastern Kentucky, 2010
Alexander J. Freiman, MPH, CPH
CDC/CSTE Applied Epidemiology Fellow
Kentucky Department for Public Health
June 15, 2011
1
Background

A. baumannii
Aerobic, gram negative bacteria
 Persist in environment
 Person-person or direct contact
 Drug resistance


Outbreaks of multi drug-resistant (MDR)
A. baumannii in healthcare setting a growing
concern
Healthcare-associated infection
 Especially in intensive care units (ICUs)

2
Background

Kentucky Department for Public Health
(KDPH) notified of Acinetobacter outbreak in
September, 2010


66 cases initially reported
Assistance requested from KDPH
New Infection Preventionist
 Reported gaps in infection control process

Hand hygiene
 Lacked comprehensive environmental cleaning protocols

3
Background


Response team assembled from KDPH and
began on-site evaluation
CDC collaboration
Medical epidemiologist
 Laboratory experts

4
Objectives

Two main objectives
Identify risk factors associated with recovery of
A. baumannii in hospitalized ICU patients
 Investigate potential environmental sources of
A. baumannii in healthcare facility

5
Methods

Study Design


Case-control
Case definition:
Laboratory-confirmed cultures of MDR A. baumannii
≥72 hours after hospital admission
 ICU admission
 January-September 2010

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Methods

Control definition
ICU admission
 December 2009-October 2010
 No history of A. baumannii infection in chart


Controls were matched to cases 1:1
ICU admission date
 ICU length of stay

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Methods

Abstracted information from medical records
Demographics
 Admission/discharge
 Medical history
 Laboratory results
 Consultations
 Procedures
 Medications

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Methods

Statistical Analysis
Frequencies
 T-test, Chi square test, Fisher’s exact test
 Odds ratios between potential risk factors and MDR
A. baumannii recovery using logistic regression

Univariate
 Multivariate


Conducted using SPSS software
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Methods


Collected environmental samples using wide
sponge culturettes
Site selection
High touch surfaces in areas with infected patients
 Identified in previous studies
 CDC recommendations

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Methods

One sample taken at each of five sites
ICU glucometer
 ICU medication dispensing unit
 ICU nursing station digital camera
 Portable x-ray machine
 Countertops in radiology unit

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Methods


Five environmental and three patient samples
sent to state and CDC labs for pulsed field gel
electrophoresis (PFGE) typing
Similarity between strains from environmental
and patient samples determined using computer
software
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Case Selection
13
Case Selection
14
Case Selection
15
Case Selection
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Results
Number of cases
Epidemic curve for MDR A. baumannii cases in an
eastern Kentucky regional medical center, 2010
(N=30)
9
8
7
6
5
4
3
2
1
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Month
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Results
Selected Characteristics of Cases and Controls
Characteristic
Race/Ethnicity
Caucasian
Non-Hispanic
Age (in years)
Mean
Median
Range
Sex
Female
Comorbidity
Diabetes
Case
n (%)
Control
n (%)
P value
29 (97)
29 (97)
29 (97)
29 (97)
1.00
1.00
68
70
40-87
67
69
38-105
0.72
12 (40)
17 (57)
0.30
18 (60)
10 (33)
0.04
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Results
Source of MDR A. baumannii
culture from cases (N=30)
Source
Respiratory
Blood
Wound
Urine
n (%)
19 (63)
5 (17)
4 (13)
2 (7)
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Results
Environmental culture results
Site
Portable x-ray machine
ICU nursing station digital camera
ICU medication dispensing unit
ICU glucometer
Countertops in radiology unit
Result
Positive
Positive
Negative
Negative
Negative
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Results
*
*
Patient 4 from another healthcare facility
21
Results
*
*
Patient 4 from another healthcare facility
22
Results
*
*
Patient 4 from another healthcare facility
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Results
*
*
Patient 4 from another healthcare facility
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Results
Crude Associations for Risk Factors and Positive MDR
A. baumannii Culture
Risk Factors
Received subcutaneous or intravenous insulin
Fingersticks performed
Total number of chest x-ray procedures
Diabetic
Central line performed
Decubitis ulcer present
Consulted with occupational therapist
Did patient have cardiovascular issues
Obese
*p value ≤ 0.05
OR
4.97
5.02
1.10
3.00
3.14
2.62
3.08
3.27
2.41
P value
0.014*
0.025*
0.032*
0.041*
0.043*
0.072
0.094
0.107
0.111
95% Confidence Interval
(1.39, 17.82)
(1.23, 20.49)
(1.01, 1.21)
(1.05, 8.60)
(1.03, 9.55)
(0.92, 7.46)
(0.82, 11.50)
(0.77, 13.83)
(0.82, 7.10)
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Results
Crude Associations for Risk Factors and Positive MDR
A. baumannii Culture
Risk Factors
Received subcutaneous or intravenous insulin
Fingersticks performed
Total number of chest x-ray procedures
Diabetic
Central line performed
Decubitis ulcer present
Consulted with occupational therapist
Did patient have cardiovascular issues
Obese
*p value ≤ 0.05
OR
4.97
5.02
1.10
3.00
3.14
2.62
3.08
3.27
2.41
P value
0.014*
0.025*
0.032*
0.041*
0.043*
0.072
0.094
0.107
0.111
95% Confidence Interval
(1.39, 17.82)
(1.23, 20.49)
(1.01, 1.21)
(1.05, 8.60)
(1.03, 9.55)
(0.92, 7.46)
(0.82, 11.50)
(0.77, 13.83)
(0.82, 7.10)
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Results
Crude Associations for Risk Factors and Positive MDR
A. baumannii Culture
Risk Factors
Received subcutaneous or intravenous insulin
Fingersticks performed
Total number of chest x-ray procedures
Diabetic
Central line performed
Decubitis ulcer present
Consulted with occupational therapist
Did patient have cardiovascular issues
Obese
*p value ≤ 0.05
OR
4.97
5.02
1.10
3.00
3.14
2.62
3.08
3.27
2.41
P value
0.014*
0.025*
0.032*
0.041*
0.043*
0.072
0.094
0.107
0.111
95% Confidence Interval
(1.39, 17.82)
(1.23, 20.49)
(1.01, 1.21)
(1.05, 8.60)
(1.03, 9.55)
(0.92, 7.46)
(0.82, 11.50)
(0.77, 13.83)
(0.82, 7.10)
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Results
Adjusted Associations for Risk Factors and MDR
A. baumannii Culture for Sampled Equipment
Risk Factors
OR
P value 95% Confidence Interval
Fingersticks performed*
4.34
0.048
(1.01, 18.62)
Total number of chest x-ray procedures†
1.10
0.065
(0.99, 1.22)
Decubitis ulcer photographed*
2.71
0.083
(0.88, 8.37)
*Model adjusted for age, type of admission, and mechanical ventilation
†Model adjusted for age, type of admission, and fingersticks
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Results
Adjusted Associations for Risk Factors and MDR
A. baumannii Culture for Sampled Equipment
Risk Factors
OR
P value 95% Confidence Interval
Fingersticks performed*
4.34
0.048
(1.01, 18.62)
Total number of chest x-ray procedures†
1.10
0.065
(0.99, 1.22)
Decubitis ulcer photographed*
2.71
0.083
(0.88, 8.37)
*Model adjusted for age, type of admission, and mechanical ventilation
†Model adjusted for age, type of admission, and fingersticks
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Discussion

Lab cultures identified two possible sources for
MDR A. baumannii transmission to patients in
the facility



Portable chest x-ray machine
Digital camera used for wound photography
PFGE pattern similarity between environmental
and patient samples matched between 92-100%
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Discussion


Epidemiologic analysis suggests receiving
fingersticks is a risk factor for becoming a case
Breakdowns in disease prevention activities
Hand hygiene
 Cleaning shared equipment


Lack of clear equipment-cleaning responsibility
might have contributed to ongoing transmission
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Discussion

Limitations

Generalizability


Reliability


Small sample
Cases: Controls only 1:1
Validity
Lack of true electronic medical records
 Incomplete line listing from healthcare facility

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Discussion


Have procedures in place to clean all shared
equipment
Recognition of an outbreak and immediate
implementation of effective controls is
CRITICAL to preventing MDR A. baumannii
transmission in the healthcare setting
33
Acknowledgments
Kentucky Department for Public Health
Margaret A. Riggs, PhD, MPH, MA
Fontaine Sands, DrPH, MSN, CIC
David R. Reese, MA, MPH, FRSPH
Kraig E. Humbaugh, MD, MPH
Doug Thoroughman, PhD, MS
Robert L. Brawley, MD, MPH, FSHEA
Centers for Disease Control and Prevention, Division
of Healthcare Quality and Promotion
Alexander J. Kallen, MD, MPH
Judith Noble-Wang, PhD
Heather A. O’Connell, PhD
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Acknowledgments

This study was supported in part by an
appointment to the Applied Epidemiology
Fellowship Program administered by the
Council of State and Territorial Epidemiologists
(CSTE) and funded by the Centers for Disease
Control and Prevention (CDC) Cooperative
Agreement Number 5U38HM000414.
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Contact Information
Alex Freiman
CDC/CSTE Applied Epidemiology Fellow
Kentucky Department for Public Health
Phone: (502)564-3261 x3278
Email: [email protected]
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