Use of Traditional Infection Control Methods plus Molecular Biology to identify, track, and solve an outbreak of Multidrug Resistant Acinetobacter baumannii infection in an intensive care unit

Background: Healthcare-associated Acinetobacter baumanii ( A baumannii) infections have been reported in US hospitals. Multidrug-resistant (MDRO) cases are increasingly being reported in intensive care units (ICU). In a regional tertiary care/teaching hospital, a patient with MDRO A baumannii was identified in an ICU in May 2010, followed by a cluster of clinical infections in two additional ICU pods 1 month later.

Objective: To determine the extent of transmission, presence of a single or multiple strains, contain and prevent further spread of MDRO A. baumanii.

Methods: A baumannii isolates were identified from clinical samples, and met criteria as MDRO by being resistant to at least three classes of antibiotics. Control techniques included hand hygiene, contact precautions, cohorting of patients and staff, enhanced environmental cleaning, and surveillance cultures of surrounding ICU patients. Environmental samples were taken for culture and identification. Clinical, surveillance and environmental isolates were further analyzed via rep-PCR amplification and an Acinetobacter fingerprinting kit using the Diversilab system.

Results: A total of 16 patients with MDRO A. baumannii were detected in the outbreak, starting in May 2010 and continuing to October 2010 when the last outbreak patient was discharged. Device related infections included 3 ventilator-associated pneumonias, 1 central line-associated bloodstream infection, and 1 catheter-associated urinary tract infection. Surveillance cultures of the surrounding 12 ICU patients with no clinical evidence of infection detected 6 (50%) as colonized either nasally (2), rectally (5) or both (1), and two patients developed clinical infections. Environmental screening for A baumannii revealed 5/7(71%) hospital rooms had contamination, with the sinks and/or countertops (5/7; 71%) and respiratory therapy equipment (3/7; 42.8%) being positive. Genotyping revealed a single strain of A baumannii detected among the clinical and surveillance cultures, and among a majority of the environmental cultures. Previous environmental cultures of these rooms had not detected A baumannii, and those performed after patient discharges and enhanced environmental cleaning were negative for A baumannii.

Conclusions: 1) A single strain of A baumannii was identified as the agent of an outbreak in an ICU by rep-PCR, with colonization and infection of patients, and environmental contamination. 2) The detection of spread to > 50% of the inhabitants of the two units reinforces the transmissibility of MDRO A. baumannii. 3) The outbreak was controlled by the implementation of traditional infection control approaches, with resolution of the MDRO A. baumannii transmission and disappearance of the organism from the environment following detailed cleaning of the rooms.