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.

Clinical and microbiologic characteristics of cephalosporin-resistant Escherichia coli at three centers in the United States.

We investigated the clinical and microbiologic features of 300 cases of cephalosporin-resistant Escherichia coli producing extended-spectrum ß-lactamase (ESBL) or plasmid-mediated AmpC ß-lactamase (pAmpC) at three medical centers in the United States. Solid-organ malignancy, connective tissue disease, and a recent history of surgery were more common among pAmpC-producing cases (n = 49), whereas urinary catheter at enrollment, diabetes, and hospitalization in the past year were more common among ESBL-producing cases (n = 233). The factors independently associated with clinical outcome were the following: the presence of cardiovascular disease (odds ratio [OR], 2.88; 95% confidence interval [CI], 1.29 to 6.43), intra-abdominal infection (OR, 6.35; 95% CI, 1.51 to 26.7), other or multiples sources of infection (OR, 8.12; 95% CI, 2.3 to 28.6), age of 65 years or greater (OR, 0.43; 95% CI, 0.2 to 0.95), favorable baseline health status (OR, 0.39; 95% CI, 0.16 to 0.95), and appropriate empirical antimicrobial therapy given in the first 72 h (OR, 0.42; 95% CI, 0.20 to 0.88). ß-Lactamase genes responsible for cephalosporin resistance were identified in 291 cases. CTX-M-type ESBLs accounted for 72.0%. Of those, 88.0% were CTX-M-15. The next most common type was CMY-type pAmpC (16.7%), followed by SHV- and TEM-type ESBLs (6.3 and 1.3%, respectively). Seven cases (2.3%) had KPC-type ß-lactamase. Ertapenem, imipenem, meropenem, doripenem, piperacillin-tazobactam, amikacin, nitrofurantoin, and tigecycline were highly active, with greater than 90% of the isolates being susceptible. Cefepime was less active, with only 74.2% being susceptible due to the predominance of CTX-M-15. These findings have implications in the selection of appropriate empirical therapy when infection due to cephalosporin-resistant E. coli is suspected.

Screening for Acinetobacter baumannii colonization by use of sponges.

There is currently no consensus method for the active screening of Acinetobacter baumannii. The use of swabs to culture nostrils, pharynx, and skin surface of various anatomical sites is known to yield less-than-optimal sensitivity. In the present study, we sought to determine whether the use of sterile sponges to sample large areas of the skin would improve the sensitivity of the detection of A. baumannii colonization. Forty-six patients known to be colonized with A. baumannii, defined by a positive clinical culture for this organism as defined by resistance to more than two classes of antimicrobials, participated in the study. The screening sites included the forehead, nostrils, buccal mucosa, axilla, antecubital fossa, groin, and toe webs with separate rayon swabs and the forehead, upper arm, and thigh with separate sponges. Modified Leeds Acinetobacter medium (mLAM) agar plates that contained vancomycin and either aztreonam or ceftazidime were used as the selective medium. An enrichment culture grown overnight substantially increased the sensitivity for most sites. The sensitivity ranged between 69.6 and 82.6% for individual sponge sites and 21.7 to 52.2% for individual swab sites when mLAM plates with ceftazidime were inoculated after a 24-h enrichment period. The sponge and swab sites with the best sensitivity were the leg and the buccal mucosa, respectively (82.6% and 52.2%; P = 0.003). The combined sensitivity for the upper arm and leg with a sponge was 89.1%. The novel screening method using sterile sponges was easy to perform and achieved excellent sensitivity for the detection of A. baumannii colonization.

Genetic environment of 16S rRNA methylase gene rmtD.

The genetic environment of the 16S rRNA methylase gene rmtD was investigated. rmtD was flanked by a novel ISCR motif located downstream of class I integron In163 in the original Pseudomonas aeruginosa strain. rmtD found in Klebsiella pneumoniae appeared to have been mobilized from P. aeruginosa by an IS26-mediated event.