Field Epidemiology in Field Epidemiology in Practice: A Hospital Practice: A Hospital Outbreak of Outbreak of AcinetobacterAcinetobacter

Suzanne Beavers, M.DSuzanne Beavers, M.DEIS OfficerEIS OfficerKentucky Department for Kentucky Department for Public HealthPublic Health

Infectious Disease Infectious Disease EpidemiologyEpidemiology

Host Agent

EnvironmentDistribution and determinants of disease frequency . . .

. . . application to public health problems.

Why initiate an Why initiate an investigation?investigation? Characterize the problemCharacterize the problem Control and preventionControl and prevention Research-answer scientific Research-answer scientific

questionsquestions Training of epidemiologistsTraining of epidemiologists Political/legal requirementPolitical/legal requirement

10 Steps of a Field 10 Steps of a Field InvestigationInvestigation

1.1. Prepare for field workPrepare for field work

2.2. Establish existence of outbreakEstablish existence of outbreak

3.3. Verify diagnosisVerify diagnosis

4.4. Define and identify casesDefine and identify cases

5.5. Orient data in terms of time, place, personOrient data in terms of time, place, person

6.6. Develop hypothesesDevelop hypotheses

7.7. Evaluate hypothesesEvaluate hypotheses

8.8. Plan additional studiesPlan additional studies

9.9. Implement control and prevention Implement control and prevention measuresmeasures

10.10. Communicate findingsCommunicate findingsAdapted from Field Epidemiology ed. Gregg MB

Field Investigations in Field Investigations in Healthcare FacilitiesHealthcare Facilities Infections common, epidemics Infections common, epidemics

uncommonuncommon Patients highly susceptible to Patients highly susceptible to

infectioninfection Colonization common, Colonization common,

transmission not always foundtransmission not always found Significant financial Significant financial

implicationsimplications

Field Investigations in Field Investigations in Healthcare FacilitiesHealthcare Facilities

Epidemiology determines Epidemiology determines questions to askquestions to ask

Laboratory provides answersLaboratory provides answers EPI and LAB together “solve” EPI and LAB together “solve”

most outbreaks (especially true most outbreaks (especially true for outbreaks in healthcare for outbreaks in healthcare facilities)facilities)

Epidemiology + Microbiology = Outbreak Success

Field Investigations in Field Investigations in Healthcare FacilitiesHealthcare 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 Acinetobacter Outbreak Outbreak InvestigationInvestigation

AcinetobacterAcinetobacter spp. spp. BackgroundBackground

Gram-negative Gram-negative bacillusbacillus

Prior healthcare- Prior healthcare- associated associated outbreaksoutbreaks

Traditionally Traditionally associated with associated with ICUsICUs

Increasing cause Increasing cause of serious illnessof serious illness

Image courtesy of Acinetobacter.com

MicrobiologyMicrobiology

Ubiquitous:Ubiquitous:– Widely distributed in nature (soil, water, Widely distributed in nature (soil, water,

food, sewage) & the hospital environmentfood, sewage) & the hospital environment Survive on moist & dry surfacesSurvive on moist & dry surfaces 32 species32 species

– >2/3 of >2/3 of AcinetobacterAcinetobacter infections are due infections are due to to A. baumanniiA. baumannii

Highly antibiotic resistantHighly antibiotic resistant

Major infections due to Major infections due to AcinetobacterAcinetobacter Ventilator-associated pneumonia Ventilator-associated pneumonia Urinary tractUrinary tract Bloodstream infectionBloodstream infection Skin/wound infectionsSkin/wound infections EndocarditisEndocarditis PeritonitisPeritonitis

AcinetobacterAcinetobacter Ventilator-Associated Ventilator-Associated PneumoniaPneumonia

AcinetobacterAcinetobacter accounts for 5- accounts for 5-25% of all cases of VAP25% of all cases of VAP

Risk factors: Risk factors: – Advanced ageAdvanced age– SurgerySurgery– Use of antimicrobial agentsUse of antimicrobial agents– Invasive devicesInvasive devices– Prolonged ICU stayProlonged ICU stay

AcinetobacterAcinetobacter spp. spp. OutbreaksOutbreaks About 80 outbreaks in published About 80 outbreaks in published

literature over past 30 yearsliterature over past 30 years– Outbreaks divided between Outbreaks divided between

respiratory, non-respiratory sitesrespiratory, non-respiratory sites– Respiratory sites commonly Respiratory sites commonly

related to ventilatorsrelated to ventilators– Variety of other sources Variety of other sources

recognized, including cell phones, recognized, including cell phones, mattresses, Bear huggers, mattresses, Bear huggers, common source medicationscommon source medications

*Ryan MP, et al, 2006 **Coenye T, et al, 2002 and Vaneechoutte M, et al, 2001

Acinetobacter Acinetobacter Outbreak InvestigationOutbreak InvestigationVerify existence of Verify existence of outbreakoutbreak DPH notified in October, 2006DPH notified in October, 2006 Hospital A in KY has increased Hospital A in KY has increased

number of casesnumber of cases 75 patients with culture-positive 75 patients with culture-positive

Acinetobacter since January, Acinetobacter since January, 20062006

Verify DiagnosisVerify Diagnosis

Goal is to rule out:Goal is to rule out:

misdiagnosismisdiagnosis

laboratory errorlaboratory error Examine case-patientsExamine case-patients Review medical recordsReview medical records Confirm laboratory testingConfirm laboratory testing

Identify and Count Identify and Count CasesCases Goals:Goals:

– Identify maximum number of casesIdentify maximum number of cases– Exclude noncasesExclude noncases

Consider spectrum of manifestation Consider spectrum of manifestation (colonized vs infected)(colonized vs infected)

Develop Case DefinitionDevelop Case Definition– Set of conditionsSet of conditions– Specific time periodSpecific time period– Specific locationSpecific location

Identify and count Identify and count casescases Conduct Conduct

systematic systematic searchsearch

Use multiple Use multiple sourcessources

Construct a line Construct a line listlist

Orient DataOrient Data

PersonPerson

PlacePlace

TimeTime

Time-Ordering Key Time-Ordering Key EventsEvents Onset of illness in cases and Onset of illness in cases and

contactscontacts Period of exposure to causal Period of exposure to causal

agents or risk factorsagents or risk factors When treatments beganWhen treatments began When control measures When control measures

implementedimplemented Potentially related events or Potentially related events or

unusual circumstancesunusual circumstances

TimeTime

Epidemic curve: # of cases by time Epidemic curve: # of cases by time of onsetof onset

Configuration permits inferencesConfiguration permits inferences– Agent known: use incubation period to Agent known: use incubation period to

look back at exposurelook back at exposure– Agent unknown, but common event Agent unknown, but common event

likely: postulate agent by determining likely: postulate agent by determining the incubation periodthe incubation period

• Construct relative to specific sites or Construct relative to specific sites or groupsgroups

Acinetobacter Acinetobacter outbreakoutbreak

Figure 1. Frequency of Acinetobacter cases at Hospital B by half month from April -

October 2006

0

1

2

3

45

6

7

8

9

Culture Date

Co

un

t

PlacePlace

In a general outbreak:In a general outbreak:– Place of residencePlace of residence– Place of occupationPlace of occupation

In a healthcare setting:In a healthcare setting:– Floor or unitFloor or unit– Operating roomOperating room

PersonPerson

Thoroughly describe the case Thoroughly describe the case groupgroup

Identify factors shared in Identify factors shared in common by casescommon by cases

Obtain denominators to Obtain denominators to derive ratesderive rates

Compare groupsCompare groups

Formulate and test Formulate and test hypothesishypothesis Goal: explain the problemGoal: explain the problem

Use comparison group(s)Use comparison group(s)– Case-control studyCase-control study– Cohort studyCohort study

• Consider causationConsider causation

Compare Hypothesis Compare Hypothesis with established factswith established facts Environmental/staff cultures Environmental/staff cultures

may be neededmay be needed– Performed to aid in the Performed to aid in the

investigation once theories are investigation once theories are generatedgenerated

– Less valuable in generating Less valuable in generating hypotheseshypotheses

Plan More Systematic Plan More Systematic StudyStudy Control Control

measuresmeasures Continued Continued

data analysisdata analysis

Implement Control Implement Control MeasuresMeasures Eliminate/treat sourceEliminate/treat source Prevent further exposuresPrevent further exposures

– Active surveillanceActive surveillance Protect at-risk populationProtect at-risk population

– Enforce isolation precautions Enforce isolation precautions • CohortingCohorting

• Close/clean contaminated areas Close/clean contaminated areas of hospitalof hospital

Thank you!Thank you!