An Outbreak of Imipenem-Resistant Acinetobacter Baumannii at Songklanagarind Hospital: The Risk Factors and Patient Prognosis
Silom Jamulitrat MD*, Somchit Thongpiyapoom RN**, Nonglak Suwalak RN**
Affiliation : * Department of Community Medicine, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla **Infection Control Unit, Songklanagarind Hospital, Hat Yai, Songkhla
Objective : To investigate for the factors associated with acquisition of imipenem-resistant Acinetobacter
baumannii (IRAB) at Songklanagarind Hospital and the subsequent patient mortality outcome.
Design : A case-control study was conducted to evaluate the risk factors for IRAB acquisition using imipenem-
sensitive A. baumannii (ISAB) as controls. A retrospective cohort study was employed to assess the factors
associated with mortality in the hospital.
Setting : An 850-bed university hospital served as a medical school, training hospital, tertiary care, and
referral center for the southern part of Thailand.
Patients: The patients who acquired A. baumannii during their stay in the hospital.
Results : Between July 2003 and September 2005, there were 2,130 isolates of A. baumannii from clinical
specimens of 1,237 hospitalized patients. The medical records of 899 admissions to the hospital were avail-
able for review. The significant risk factors associated with IRAB acquisition, identified from a case-control
study and multiple logistic regression analysis included previous admission to medical-surgical intensive
care unit (ICU), respiratory care unit (RCU), previous use of multiple classes of antibiotics, and previous use
of imipenem. The cohort study revealed that the mortality rate in the patients with IRAB compared to ISAB
were 33.8% and 24.1% respectively, yielding an unadjusted odds ratio of 1.6 (95% CI = 1.2-2.2). However,
after controlling for confounding factors by multivariate analysis IRAB did not show the increased mortality.
Conclusion : The outbreak of IRAB at Songklanagarind Hospital is associated with increasing antibiotic
pressure particularly imipenem and the admission to the ICU and RCU. The excess patient mortality rate
attributable to IRAB is not significantly different from that attributable to ISAB.
Keywords : Epidemic, Outbreak, Acinetobacter baumannii, Antimicrobial-resistant, Imipenem
