Reservoir of Carbapenem-Resistant Acinetobacter baumannii in the Hospital Environment and Colonization Pressure: A Surveillance-Based Study in Indian Intensive Care Unit

Abstract

The endemicity of Acinetobacter baumannii in intensive care units (ICUs) is a serious concern. We studied the reservoirs of A. baumannii in the ICU and their effects on colonization pressure and transmission. A prospective surveillance (6 months) was conducted. Screening culture (rectal and axillary) swabs were collected within 48 hours admission and in 120 hours. Surveillance cultures from patients' surroundings, health care workers (HCWs), and hospital sewage were collected. A. baumannii was identified by phenotypic and genotypic methods. Carbapenem resistance and insertion sequence element were detected. Typing was done by repetitive extragenic palindromic-polymerase chain reaction and multilocus sequence typing. Colonization pressure was calculated and compared with environment colonizers. Of the 87 patients, 21.83% (19) were colonized with A. baumannii, 73.68% (14/19) were imported, and 26.31% (5/19) acquired carriers. Axilla was the commonest site. From the environment (15), bed rails 33.33% (5/15) and suction tubes 26.66% (4/15) were the common sites. HCWs showed 7.5% (3/40) carriage. Carbapenem resistance with bla_OXA-51, bla_OXA-23, and ISAba1 were 91.89% (34/37). Strong correlation between colonization pressures and environmental colonizers was seen (r² = 0.719, p = 0.032). Carbapenem and polymyxin B were (p ≤ 0.05) significant exposures. Sequence type 623 was the predominant cluster with isolates from carriers, HCWs, and environment. Colonization pressure of carbapenem-resistant A. baumannii depends on their presence in the hospital. Hands of HCWs were an important vehicle for transmission. Infection control measure should consider reducing the environmental reservoir.