Endemic Acinetobacter baumannii in a New York Hospital

Acinetobacter baumannii is an increasingly multidrug-resistant (MDR) cause of hospital-acquired infections, often associated with limited therapeutic options. We investigated A. baumannii isolates at a New York hospital to characterize genetic relatedness.Thirty A. baumannii isolates from geographically-dispersed nursing units within the hospital were studied. Isolate relatedness was assessed by repetitive sequence polymerase chain reaction (rep-PCR). The presence and characteristics of integrons were assessed by PCR. Metabolomic profiles of a subset of a prevalent strain isolates and sporadic isolates were characterized and compared.We detected a hospital-wide group of closely related carbapenem resistant MDR A. baumannii isolates. Compared with sporadic isolates, the prevalent strain isolates were more likely to be MDR (p = 0.001). Isolates from the prevalent strain carried a novel Class I integron sequence. Metabolomic profiles of selected prevalent strain isolates and sporadic isolates were similar.The A. baumannii population at our hospital represents a prevalent strain of related MDR isolates that contain a novel integron cassette. Prevalent strain and sporadic isolates did not segregate by metabolomic profiles. Further study of environmental, host, and bacterial factors associated with the persistence of prevalent endemic A. baumannii strains is needed to develop effective prevention strategies

Integron Content in Select Study Isolates.

<p>Integron PCR gene products of WC 13–24 are shown. The block arrow marks the 550 base pair PCR product of the prevalent strain <i>A. baumannii</i>. The water control is labeled “neg.” The cartoon shows the layout of a typical Class I integron. The PCR primers are presented by CS-F and CS-R.</p

Rep-PCR Analysis of Study Isolates.

<p>Isolates with more than 90% similarity were considered related. Study isolates (WC 1–30) are shown, plus one isolate (WC-31) isolated on hospital day 1 after transfer from an outside hospital. Results show the majority of the study isolates are closely related.</p

Study Isolates.

<p>Study isolates (plus WC-31, which was isolated from a patient on Hospital Day 1 after transfer from an outside hospital). <b>Legend WC</b> = Weill Cornell; <b>PT</b> = Patient age and gender; <b>Date:</b> All dates are from 2008; <b>Floor:</b> Each letter represents a different hospital floor; Antimicrobial susceptibility to the various agents was determined following CLSI guidelines, or the Mean Inhibitory Concentration is reported directly for polymyxin B and tigecycline (µg/mL): A/S: ampicillin-sulbactam, Carb: imipenem or meropenem; Cef: cefepime; Gent; gentamicin; Amik: amikacin; S/T: sulfamethoxazole-trimethoprim; Levo: levofloxacin; PM: polymyxin B; Tig: tigecycline; Source: Resp = respiratory. Susceptibility interpretation based on 2008 CLSI cutoff points.</p