Field Epidemiology in Practice: A Hospital Outbreak of Acinetobacter Suzanne Beavers, M.D EIS Officer Kentucky Department for Public Health

Infectious Disease Epidemiology Host Agent Environment Distribution and determinants of disease frequency application to public health problems.

Why initiate an investigation? Characterize the problem Characterize the problem Control and prevention Control and prevention Research-answer scientific questions Research-answer scientific questions Training of epidemiologists Training of epidemiologists Political/legal requirement Political/legal requirement

10 Steps of a Field Investigation 1. Prepare for field work 2. Establish existence of outbreak 3. Verify diagnosis 4. Define and identify cases 5. Orient data in terms of time, place, person 6. Develop hypotheses 7. Evaluate hypotheses 8. Plan additional studies 9. Implement control and prevention measures 10. Communicate findings Adapted from Field Epidemiology ed. Gregg MB

Field Investigations in Healthcare Facilities Infections common, epidemics uncommon Infections common, epidemics uncommon Patients highly susceptible to infection Patients highly susceptible to infection Colonization common, transmission not always found Colonization common, transmission not always found Significant financial implications Significant financial implications

Field Investigations in Healthcare Facilities Epidemiology determines questions to ask Epidemiology determines questions to ask Laboratory provides answers Laboratory provides answers EPI and LAB together “solve” most outbreaks (especially true for outbreaks in healthcare facilities) EPI and LAB together “solve” most outbreaks (especially true for outbreaks in healthcare facilities) Epidemiology + Microbiology = Outbreak Success

Field Investigations in Healthcare Facilities Surveillance Epidemiologic Studies Confirmatory Studies Local Interventions Adapted from Ostrowsky and Jarvis Efficient Management of Outbreak Investigations Provides first evidence of outbreak Often detected by microbiology Patient isolation Enhanced disinfection Suspend procedure or close unit Line list of cases Epi-curves Case-Control study Exposure risks Surveillance cultures Environmental samples Culture ID Susceptibility testing Isolate typing

Acinetobacter Outbreak Investigation

Acinetobacter spp. Background Gram-negative bacillus Gram-negative bacillus Prior healthcare- associated outbreaks Prior healthcare- associated outbreaks Traditionally associated with ICUs Traditionally associated with ICUs Increasing cause of serious illness Increasing cause of serious illness Image courtesy of Acinetobacter.com

Microbiology Ubiquitous: Ubiquitous: –Widely distributed in nature (soil, water, food, sewage) & the hospital environment Survive on moist & dry surfaces Survive on moist & dry surfaces 32 species 32 species –>2/3 of Acinetobacter infections are due to A. baumannii Highly antibiotic resistant Highly antibiotic resistant

Major infections due to Acinetobacter Ventilator-associated pneumonia Ventilator-associated pneumonia Urinary tract Urinary tract Bloodstream infection Bloodstream infection Skin/wound infections Skin/wound infections Endocarditis Endocarditis Peritonitis Peritonitis

Acinetobacter Ventilator- Associated Pneumonia Acinetobacter accounts for 5-25% of all cases of VAP Acinetobacter accounts for 5-25% of all cases of VAP Risk factors: Risk factors: –Advanced age –Surgery –Use of antimicrobial agents –Invasive devices –Prolonged ICU stay

Acinetobacter spp. Outbreaks About 80 outbreaks in published literature over past 30 years About 80 outbreaks in published literature over past 30 years –Outbreaks divided between respiratory, non-respiratory sites –Respiratory sites commonly related to ventilators –Variety of other sources recognized, including cell phones, mattresses, Bear huggers, common source medications *Ryan MP, et al, 2006**Coenye T, et al, 2002 and Vaneechoutte M, et al, 2001

Acinetobacter Outbreak Investigation Verify existence of outbreak DPH notified in October, 2006 DPH notified in October, 2006 Hospital A in KY has increased number of cases Hospital A in KY has increased number of cases 75 patients with culture-positive Acinetobacter since January, patients with culture-positive Acinetobacter since January, 2006

Verify Diagnosis Goal is to rule out: Goal is to rule out:misdiagnosis laboratory error Examine case-patients Examine case-patients Review medical records Review medical records Confirm laboratory testing Confirm laboratory testing

Identify and Count Cases Goals: Goals: –Identify maximum number of cases –Exclude noncases  Consider spectrum of manifestation (colonized vs infected)  Develop Case Definition –Set of conditions –Specific time period –Specific location

Identify and count cases Conduct systematic search Conduct systematic search Use multiple sources Use multiple sources Construct a line list Construct a line list

Orient Data Person Person Place Place Time Time

Time-Ordering Key Events Onset of illness in cases and contacts Onset of illness in cases and contacts Period of exposure to causal agents or risk factors Period of exposure to causal agents or risk factors When treatments began When treatments began When control measures implemented When control measures implemented Potentially related events or unusual circumstances Potentially related events or unusual circumstances

Time Epidemic curve: # of cases by time of onset Epidemic curve: # of cases by time of onset Configuration permits inferences Configuration permits inferences –Agent known: use incubation period to look back at exposure –Agent unknown, but common event likely: postulate agent by determining the incubation period Construct relative to specific sites or groupsConstruct relative to specific sites or groups

Acinetobacter outbreak

Place In a general outbreak: In a general outbreak: –Place of residence –Place of occupation In a healthcare setting: In a healthcare setting: –Floor or unit –Operating room

Person Thoroughly describe the case group Thoroughly describe the case group Identify factors shared in common by cases Identify factors shared in common by cases Obtain denominators to derive rates Obtain denominators to derive rates Compare groups Compare groups

Formulate and test hypothesis Goal: explain the problem Goal: explain the problem Use comparison group(s) Use comparison group(s) –Case-control study –Cohort study Consider causationConsider causation

Compare Hypothesis with established facts Environmental/staff cultures may be needed Environmental/staff cultures may be needed –Performed to aid in the investigation once theories are generated –Less valuable in generating hypotheses

Plan More Systematic Study Control measures Control measures Continued data analysis Continued data analysis

Implement Control Measures Eliminate/treat source Eliminate/treat source Prevent further exposures Prevent further exposures –Active surveillance Protect at-risk population Protect at-risk population –Enforce isolation precautions Cohorting Cohorting Close/clean contaminated areas of hospitalClose/clean contaminated areas of hospital

Thank you!