Use of fluoroquinolones is the single most important risk factor for the high bacterial load in patients with nasal and gastrointestinal colonization by multidrug-resistant Acinetobacter baumannii

Gastrointestinal colonization by carbapenem-resistant Acinetobacter baumannii (CRAB) and multidrug-resistant Acinetobacter baumannii (MRAB) provides an important reservoir for clinical infections and hospital outbreaks. We conducted a 7-month study in a 3200-bed healthcare network to investigate the prevalence of gastrointestinal colonization of CRAB and MRAB in Hong Kong. Between 1 June and 31 December 2014, a total of 17,760 fecal specimens from 9469 patients were screened. Testing showed that 340 (1.9 %) specimens from 224 (2.6 %) patients were CRAB-positive, which included 70 (0.39 %) MRAB-positive specimens from 54 (0.57 %) patients. The presence of wound or ulcer, use of broad-spectrum antibiotics in the preceding 6 months, and residence in elderly homes are independent risk factors for gastrointestinal colonization of CRAB. Quantitative bacterial counts in various body sites (rectal, nasal, axilla, wound, catheterized urine, if available) were performed in 33 (61.1 %) of 54 MRAB patients. Ten (30.3 %) and 8 (24.2 %) patients had high bacterial load (defined as over 3 log₁₀) in rectal and nasal swabs, with a median of 5.04 log₁₀ cfu/ml of rectal swab and 4.89 log₁₀ cfu/ml of nasal swab in saline diluent, respectively. Nine (81.8 %) of 11 patients with wounds had high bacterial load in wound swabs, with a median of 5.62 log₁₀ cfu/ml. Use of fluoroquinolones 6 months before admission was the only significant factor associated with high bacterial load in nasal and rectal swabs. With the implementation of directly observed hand hygiene before meals and medications to all conscious hospitalized patients, no hospital outbreaks were observed during our study period.