No abstract

Fosfomycin resistance in Escherichia coli is rare in the United States. An extended-spectrum β-lactamase–producing E. coli clinical strain identified in Pennsylvania, USA, showed high-level fosfomycin resistance caused by the fosA3 gene. The IncFII plasmid carrying this gene had a structure similar to those found in China, where fosfomycin resistance is commonly described.

OBJECTIVE To concomitantly determine the differential degrees of air and environmental contamination by Acinetobacter baumannii based on anatomic source of colonization and type of ICU layout (single-occupancy vs open layout). DESIGN Longitudinal prospective surveillance study of air and environmental surfaces in patient rooms. SETTING A 1,500-bed public teaching hospital in Miami, Florida. PATIENTS Consecutive A. baumannii-colonized patients admitted to our ICUs between October 2013 and February 2014. METHODS Air and environmental surfaces of the rooms of A. baumannii-colonized patients were sampled daily for up to 10 days. Pulsed-field gel electrophoresis (PFGE) was used to type and match the matching air, environmental, and clinical A. baumannii isolates. RESULTS A total of 25 A. baumannii-colonized patients were identified during the study period; 17 were colonized in the respiratory tract and 8 were colonized in the rectum. In rooms with rectally colonized patients, 38.3% of air samples were positive for A. baumannii; in rooms of patients with respiratory colonization, 13.1% of air samples were positive (P=.0001). In rooms with rectally colonized patients, 15.5% of environmental samples were positive for A. baumannii; in rooms of patients with respiratory colonization, 9.5% of environmental samples were positive (P=.02). The rates of air contamination in the open-layout and single-occupancy ICUs were 17.9% and 21.8%, respectively (P=.5). Environmental surfaces were positive in 9.5% of instances in open-layout ICUs versus 13.4% in single-occupancy ICUs (P=.09). CONCLUSIONS Air and environmental surface contaminations were significantly greater among rectally colonized patients; however, ICU layout did not influence the rate of contamination. Infect Control Hosp Epidemiol 2016;37:777-781.

Acinetobacter baumannii is a prevalent nosocomial pathogen with a high incidence of multidrug resistance. Treatment of infections due to this organism with colistin, a last-resort antibiotic of the polymyxin class, can result in the emergence of colistin-resistant strains. Colistin resistance primarily occurs via modifications of the terminal phosphate moieties of lipopolysaccharide-derived lipid A, which reduces overall membrane electronegativity. These modifications are readily identified by mass spectrometry (MS). In this study, we prospectively collected Acinetobacter baumannii complex clinical isolates from a hospital system in Pennsylvania over a 3-year period. All isolates were evaluated for colistin resistance using standard MIC testing by both agar dilution and broth microdilution, as well as genospecies identification and lipid A profiling using MS analyses. Overall, an excellent correlation between colistin susceptibility and resistance, determined by MIC testing, and the presence of a lipid A modification, determined by MS, was observed with a sensitivity of 92.9% and a specificity of 94.0%. Additionally, glycolipid profiling was able to differentiate A. baumannii complex organisms based on their membrane lipids. With the growth of MS use in clinical laboratories, a reliable MS-based glycolipid phenotyping method that identifies colistin resistance in A. baumannii complex clinical isolates, as well as other Gram-negative organisms, represents an alternative or complementary approach to existing diagnostics.

K. pneumoniae ST37 strains with an MDR IncR plasmid carrying armA, blaDHA-1 and qnrB4 were identified in a hospital in the USA, where these resistance genes remain rare. The IncR backbone may play a role in the global dissemination of these resistance genes.