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Carbapenems are important agents for the therapy of infections due to multidrug-resistant Pseudomonas aeruginosa; the development of carbapenem resistance hampers effective therapeutic options. To assess the mechanisms leading to resistance, 33 clinical isolates with differing degrees of carbapenem susceptibility were analyzed for the expression of the chromosomal ␤-lactamase (ampC), the porin that is important for the entry of carbapenems (oprD), and the proteins involved in four efflux systems (mexA, mexC, mexE, and mexX). Real-time reverse transcriptase PCR was performed using primers and fluorescent probes for each of the target genes. The sequencing of regulatory genes (ampR, mexR, nalC, nalD, mexT, and mexZ) was also performed. Diminished expression of oprD was present in all imipenem-and meropenem-resistant isolates but was not required for ertapenem resistance. Increased expression of ampC was not observed in several isolates that were overtly resistant to carbapenems. Increased expression of several efflux systems was observed in many of the carbapenem-resistant isolates. Increased efflux activity correlated with high-level ertapenem resistance and reduced susceptibility to meropenem and aztreonam. Most isolates with increased expression of mexA had mutations affecting nalC and/or nalD. Two isolates with mutations leading to a premature stop codon in mexZ had markedly elevated mexX expressions, although mutations in mexZ were not a prerequisite for overexpression. ␤-Lactam resistance in clinical isolates of P. aeruginosa is a result of the interplay between diminished production of oprD, increased activity of ampC, and several efflux systems.Both acquired and intrinsic mechanisms of antibiotic resistance make Pseudomonas aeruginosa a formidable nosocomial pathogen (19). Carbapenem antibiotics remain important agents for the therapy of serious infections due to multidrug-resistant P. aeruginosa; the development of carbapenem resistance severely compromises effective therapeutic options. In the absence of carbapenem-hydrolyzing enzymes, the mechanism leading to carbapenem resistance is usually multifactorial. Increased chromosomal cephalosporinase activity, reduced porin expression, and augmented antibiotic extrusion have all been defined as contributory factors (18,19). The outer membrane protein OprD allows entry of carbapenems, and its reduced expression is frequently noted in carbapenem-resistant isolates (18,33).Several antibiotic efflux systems that belong to the resistance-nodulation-division family and contribute to multidrug resistance have been characterized in P. aeruginosa. The MexAB-OprM system is constitutively expressed in virtually all isolates, and substrates for this pump include fluoroquinolones, tetracycline, chloramphenicol, and ␤-lactams (including carbenicillin, piperacillin, ceftazidime, cefepime, and aztreonam) (17,27,40,46,50). Imipenem does not appear to be a substrate for MexAB-OprM, but because of its hydrophobic side chain, meropenem can be affected by this system (13,17,33)....

Summary Background : Steroid resistance represents a major clinical problem in the treatment of ulcerative colitis. In vitro, interleukin‐2 renders lymphocytes steroid resistant. Aim : To explore the therapeutic potential of interleukin‐2 receptor blockade in steroid‐resistant ulcerative colitis with both in vitro measures and a pilot in vivo study. Methods : Ten patients with steroid‐resistant ulcerative colitis received a single bolus of 40 mg of intravenous basiliximab plus steroid treatment in an open‐label, uncontrolled, 24‐week study. The outcome was assessed using the Ulcerative Colitis Symptom Score, rectal biopsy and Inflammatory Bowel Disease Questionnaire. Lymphocyte steroid sensitivity was measured in vitro in 39 subjects in the presence or absence of basiliximab. Results : Nine of the 10 patients achieved clinical remission within 8 weeks. At 24 weeks, seven patients were in clinical remission. Marked improvement in the Ulcerative Colitis Symptom Score was seen by 1 week (P = 0.004) and on rectal biopsy and Inflammatory Bowel Disease Questionnaire by 2 weeks (both P < 0.05). Improvements persisted to 24 weeks (Ulcerative Colitis Symptom Score, Inflammatory Bowel Disease Questionnaire, both P < 0.005). Eight of the nine responders relapsed (median, 9 weeks), but remission was re‐achieved with further corticosteroids and the addition of azathioprine. At 24 weeks, seven patients were in full clinical remission, five off all steroid therapy. In vitro measurement of lymphocyte steroid sensitivity demonstrated steroid resistance in 22% of subjects. All were rendered steroid sensitive in the presence of basiliximab. Conclusions : Basiliximab appears to be effective at inducing remission in steroid‐resistant ulcerative colitis. In vitro, basiliximab also produced a dramatic increase in lymphocyte steroid sensitivity in healthy subjects. Confirmation in randomized controlled studies is required.

A carbapenem-resistant isolate of Escherichia coli was identified that possessed a 23-kb plasmid encoding Klebsiella pneumoniae carbapenemase type 2 (KPC-2). A subsequent surveillance study involving hospitals in Brooklyn, New York, revealed that, among 1417 E. coli isolates, 7 isolates (from 3 hospitals) possessed bla(KPC-2). E. coli possessing KPC-2 is emerging in our region, and improved methods for detection are urgently needed.