Colistin-resistant Acinetobacter baumannii: beyond carbapenem resistance.

BACKGROUND: With an increase in the use of colistin methansulfonate (CMS) to treat carbapenem-resistant Acinetobacter baumannii infections, colistin resistance is emerging. METHODS: Patients with infection or colonization due to colistin-resistant A. baumannii were identified at a hospital system in Pennsylvania. Clinical data were collected from electronic medical records. Susceptibility testing, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) were performed. To investigate the mechanism of colistin resistance, lipid A was subjected to matrix-assisted laser desorption/ionization mass spectrometry. RESULTS: Twenty patients with colistin-resistant A. baumannii were identified. Ventilator-associated pneumonia was the most common type of infection. Nineteen patients had received intravenous and/or inhaled CMS for treatment of carbapenem-resistant, colistin-susceptible A. baumannii infection prior to identification of colistin-resistant isolates. The 30-day all-cause mortality rate was 30%. The treatment regimen for colistin-resistant A. baumannii infection associated with the lowest mortality rate was a combination of CMS, a carbapenem, and ampicillin-sulbactam. The colistin-susceptible and -resistant isolates from the same patients were highly related by PFGE, but isolates from different patients were not, suggesting evolution of resistance during CMS therapy. By MLST, all isolates belonged to the international clone II, the lineage that is epidemic worldwide. Phosphoethanolamine modification of lipid A was present in all colistin-resistant A. baumannii isolates. CONCLUSIONS: Colistin-resistant A. baumannii occurred almost exclusively among patients who had received CMS for treatment of carbapenem-resistant, colistin-susceptible A. baumannii infection. Lipid A modification by the addition of phosphoethanolamine accounted for colistin resistance. Susceptibility testing for colistin should be considered for A. baumannii identified from CMS-experienced patients.

OXA-48-producing Enterobacteriaceae causing bacteremia, United Arab Emirates.

OXA-48-producing isolates were identified in approximately 4% and less than 1% of ESBL-producing and non-ESBL-producing E. coli and K. pneumoniae causing bacteremia at the largest tertiary hospital in Abu Dhabi.

Molecular features of community-associated extended-spectrum-ß-lactamase-producing Escherichia coli strains in the United States.

We characterized 30 community-associated extended-spectrum-ß-lactamase-producing Escherichia coli isolates collected from five hospitals in the United States. Nineteen sequence types were identified. All sequence type 131 (ST131) isolates had the fimH30 allele. IncFII-FIA-FIB was the most common replicon type among the blaCTX-M-carrying plasmids, followed by IncFII-FIA and IncA/C. Restriction analysis of the IncFII-FIA-FIB and IncFII-FIA plasmids yielded related profiles for plasmids originating from different hospitals. The plasmids containing blaCTX-M or blaSHV were stably maintained after serial passages.

Microbiological features of KPC-producing Enterobacter isolates identified in a U.S. hospital system.

Microbiological data regarding Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacter spp. are scarce. In this study, 11 unique KPC-producing Enterobacter isolates were identified among 44 ertapenem-nonsusceptible Enterobacter isolates collected between 2009 and 2013 at a hospital system in Western Pennsylvania. All cases were healthcare-associated and occurred in medically complex patients. While pulsed-field gel electrophoresis showed diverse restriction patterns overall, multilocus sequence typing identified Enterobacter cloacae isolates with sequence types 93 and 171 from 2 hospitals each. The levels of carbapenem minimum inhibitory concentrations were highly variable. All isolates remained susceptible to colistin and tigecycline, and the majority, to amikacin and doxycycline. A blaKPC-carrying IncN plasmid conferring trimethoprim-sulfamethoxazole resistance was identified in 3 of the isolates. Spread of blaKPC in Enterobacter spp. appears to be due to a combination of plasmid-mediated and clonal processes.

Clinical outcomes of hospital-acquired infection with Acinetobacter nosocomialis and Acinetobacter pittii.

The role of Acinetobacter nosocomialis and Acinetobacter pittii, which belong to the A. calcoaceticus-A. baumannii complex, in hospital-acquired infections is increasingly recognized. Here we describe a retrospective cohort study of hospital-acquired A. calcoaceticus-A. baumannii complex infections at a university hospital in Thailand. A total of 222 unique cases were identified between January 2010 and December 2011. The genomospecies of the A. calcoaceticus-A. baumannii complex isolates were classified as follows: A. baumannii, 197 (89%); A. nosocomialis, 18 (8%); and A. pittii, 7 (3%). All A. nosocomialis and A. pittii isolates were susceptible to imipenem and meropenem. The patients infected with A. nosocomialis and A. pittii had lower 30-day mortality than those infected with carbapenem-susceptible A. baumannii (P = 0.025) and carbapenem-resistant A. baumannii (P = 0.013). The factors influencing 30-day mortality were infection with non-baumannii A. calcoaceticus-A. baumannii complex (hazard ratio [HR], 0.12; 95% confidence interval [CI], 0.03 to 0.51; P = 0.004), infection with carbapenem-resistant A. baumannii (HR, 1.57; 95% CI, 0.89 to 2.79; P = 0.105), appropriate empirical antimicrobial therapy (HR, 0.38; 95% CI, 0.23 to 0.61; P < 0.001), and higher acute physiology and chronic health evaluation II (APACHE II) score (HR, 1.15; 95% CI, 1.10 to 1.19; P < 0.001). In Galleria mellonella assays, the survival rates were significantly higher for the larvae infected with A. nosocomialis or A. pittii than for those infected with either carbapenem-susceptible A. baumannii or carbapenem-resistant A. baumannii, but no differences in survival rates were observed between carbapenem-susceptible A. baumannii and carbapenem-resistant A. baumannii. These findings suggest intrinsic differences in virulence between non-baumannii A. calcoaceticus-A. baumannii complex species and A. baumannii but not between carbapenem-susceptible and resistant A. baumannii.

Molecular epidemiology of KPC-producing Escherichia coli: occurrence of ST131-fimH30 subclone harboring pKpQIL-like IncFIIk plasmid.

Of 20 Klebsiella pneumoniae carbapenemase (KPC)-producing Escherichia coli isolates identified at hospitals in western Pennsylvania, 60% belonged to the epidemic ST131-fimH30 subclone. IncFIIk was the most common replicon type for the blaKPC-carrying plasmids (n = 8). All IncFIIk plasmids possessed a scaffold similar to that of pKpQIL, and seven of them were borne by ST131-fimH30 isolates. IncN plasmids conferred resistance to trimethoprim-sulfamethoxazole, and IncA/C plasmids conferred resistance to gentamicin. Three blaKPC-carrying plasmids (IncA/C and IncN) possessed blaSHV-7/12 and qnrA1 or qnrS1.

Aerosolization of Acinetobacter baumannii in a trauma ICU*.

OBJECTIVE: To establish the presence of air contamination with Acinetobacter baumannii in the trauma ICU. DESIGN: Point prevalence microbiological surveillances. SETTINGS: A 1,500-bed public teaching hospital in the Miami metro area. PATIENTS: Trauma ICU patients. MEASUREMENTS: Pulsed field electrophoresis was performed on environmental and clinical isolates to determine the association of any isolates from the air with clinical isolates. MAIN RESULTS: Out of 53 patient areas cultured, 12 (22.6%) had their air positive for A. baumannii. The presence of an A. baumannii-positive patient (underneath the plate) was associated with positive air cultures for A. baumannii (11 of 21 [52.4%] vs 0 of 25 [0%]; p < 0.0001). However, we were not able to find differences in air contamination based on the presence of A. baumannii in respiratory secretions versus absence (p = 1.0). Air and clinical isolates were found to be clonally related. CONCLUSIONS: Aerosolization of A. baumannii in the ICUs is a concern, and its role in the transmission of this organism among patients should be further clarified.

Acinetobacter baumannii: association between environmental contamination of patient rooms and occupant status.

We aimed to determine the association between the presence of Acinetobacter baumannii in patient rooms and the carrier status of the occupants. Fifty-six (39%) of 143 rooms with A. baumannii-positive patients had results positive for A. baumannii. Only 49 (10%) of 485 rooms with A. baumannii-negative patients were positive (odds ratio, 5.72 [95% confidence interval, 3.66-8.96]; [Formula: see text]). Clinical and environmental isolates shared pulsed-field gel electrophoresis patterns.

Community-associated extended-spectrum ß-lactamase-producing Escherichia coli infection in the United States.

Background. The occurrence of community-associated infections due to extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli has been recognized as a major clinical problem in Europe and other regions. Methods. We conducted a prospective observational study to examine the occurrence of community-associated infections due to ESBL-producing E. coli at centers in the United States. Five academic and community hospitals and their affiliated clinics participated in this study in 2009 and 2010. Sites of acquisition of the organisms (community-associated or healthcare-associated), risk factors, and clinical outcome were investigated. Screening for the global epidemic sequence type (ST) 131 and determination of the ESBL types was conducted by polymerase chain reaction and sequencing. Results. Of the 291 patients infected or colonized with ESBL-producing E. coli as outpatients or within 48 hours of hospitalization, 107 (36.8%) had community-associated infection (81.5% of which represented urinary tract infection), while the remainder had healthcare-associated infection. Independent risk factors for healthcare-associated infection over community-associated infection were the presence of cardiovascular disease, chronic renal failure, dementia, solid organ malignancy, and hospitalization within the previous 12 months. Of the community-associated infections, 54.2% were caused by the globally epidemic ST131 strain, and 91.3% of the isolates produced CTX-M-type ESBL. Conclusions. A substantial portion of community-onset, ESBL-producing E. coli infections now occur among patients without discernible healthcare-associated risk factors in the United States. This epidemiologic shift has implications for the empiric management of community-associated infection when involvement of E. coli is suspected.