Expanded-spectrum Cephalosporin Resistance Research Articles

Integron-borne transmission of VEB-1 extended-spectrum β-lactamase in Pseudomonas aeruginosa in a tertiary care hospital in India.

A total 14 clinical isolates of Pseudomonas aeruginosa that produced VEB-1 and were susceptible only to polymyxin B were recovered from hospitalized patients. VEB-1 was located within variable regions of the class 1 integron, flanked by resistant genes, and was horizontally transferable as well as carried within the IncP-type plasmid. We conclude that the IncP-type plasmid is responsible for the horizontal transmission of VEB-1-mediated expanded-spectrum cephalosporin resistance in this medical center.

Reclaiming the efficacy of β-lactam-β-lactamase inhibitor combinations: avibactam restores the susceptibility of CMY-2-producing Escherichia coli to ceftazidime.

CMY-2 is a plasmid-encoded Ambler class C cephalosporinase that is widely disseminated in Enterobacteriaceae and is responsible for expanded-spectrum cephalosporin resistance. As a result of resistance to both ceftazidime and β-lactamase inhibitors in strains carrying blaCMY, novel β-lactam-β-lactamase inhibitor combinations are sought to combat this significant threat to β-lactam therapy. Avibactam is a bridged diazabicyclo [3.2.1]octanone non-β-lactam β-lactamase inhibitor in clinical development that reversibly inactivates serine β-lactamases. To define the spectrum of activity of ceftazidime-avibactam, we tested the susceptibilities of Escherichia coli clinical isolates that carry bla(CMY-2) or bla(CMY-69) and investigated the inactivation kinetics of CMY-2. Our analysis showed that CMY-2-containing clinical isolates of E. coli were highly susceptible to ceftazidime-avibactam (MIC(90), ≤ 0.5 mg/liter); in comparison, ceftazidime had a MIC90 of >128 mg/liter. More importantly, avibactam was an extremely potent inhibitor of CMY-2 β-lactamase, as demonstrated by a second-order onset of acylation rate constant (k2/K) of (4.9 ± 0.5) × 10(4) M(-1) s(-1) and the off-rate constant (k(off)) of (3.7 ± 0.4) × 10(-4) s(-1). Analysis of the reaction of avibactam with CMY-2 using mass spectrometry to capture reaction intermediates revealed that the CMY-2-avibactam acyl-enzyme complex was stable for as long as 24 h. Molecular modeling studies raise the hypothesis that a series of successive hydrogen-bonding interactions occur as avibactam proceeds through the reaction coordinate with CMY-2 (e.g., T316, G317, S318, T319, S343, N346, and R349). Our findings support the microbiological and biochemical efficacy of ceftazidime-avibactam against E. coli containing plasmid-borne CMY-2 and CMY-69.

Emergence and maintenance of multidrug-resistant Escherichia coli of canine origin harbouring a blaCMY-2-IncI1/ST65 plasmid and topoisomerase mutations

To characterize the mechanisms implicated in fluoroquinolone (FQ) and expanded-spectrum cephalosporin (ESC) resistance in three clinical and seven faecal multidrug-resistant (MDR; resistant to at least three antimicrobial classes) Escherichia coli isolates from a dog with atopic dermatitis, also suffering from recurrent otitis, that had already been exposed to prolonged antimicrobial treatment and colonized for a long period. MICs of FQs, ESCs and other antimicrobials were determined by the broth microdilution method. Phenotypic tests (efflux pump inhibition and combination disc tests) and isoelectric focusing were combined with genotypic analyses [PCRs, sequencing, conjugation, S1 nuclease PFGE, PCR-based replicon typing, plasmid multilocus sequence typing (pMLST) and PCR mapping] to characterize the molecular basis of FQ and ESC resistance. Isolates were further characterized by MLST and PFGE. Three otitis and five faecal isolates with enrofloxacin MICs of 32 to >128 mg/L displayed the GyrA:S83L+D87N/ParC:E62K/ParE:G545D pattern harbouring novel ParC and ParE substitutions, whereas the two remaining faecal isolates were susceptible or borderline resistant single-step mutants (GyrA:S83L pattern) and carried qnrS1. Efflux pump overexpression also contributed to FQ resistance and the MDR phenotype. The three otitis and five faecal isolates also exhibited cefoxitin/ceftazidime MICs of 32-64 mg/L and harboured blaCMY-2, adjusted to ISEcp1, on an IncI1/ST65 conjugative plasmid, previously described in Salmonella Heidelberg from poultry. Interestingly, all isolates shared an identical MLST type (ST212), with the otitis isolates showing indistinguishable patterns with the high-level resistant faecal E. coli isolates. The long-term maintenance of FQ- and ESC-resistant clones harbouring topoisomerase mutations and a blaCMY-2-IncI1/ST65 plasmid in canine commensal flora after prolonged antimicrobial use may contribute to the dissemination of multidrug resistance.

Multilocus Variable-Number Tandem-Repeat Analysis and Plasmid Profiling To Study the Occurrence of bla CMY-2 within a Pulsed-Field Gel Electrophoresis-Defined Clade of Salmonella enterica Serovar Typhimurium

Salmonella enterica serovar Typhimurium circulating in food animal populations and carrying resistance to antimicrobial agents represents a human health risk. Recently, a new clade of S. Typhimurium, WA-TYP035/187, was reported in cattle and humans in the Pacific Northwest, United States of America. The objective of this study was to describe a possible mechanism of acquisition of expanded-spectrum cephalosporin resistance in this clade. Ceftazidime resistance increased steadily among WA-TYP035/187 isolates, from 0% (0/2) in 1999 to 77.8% (28/36) in 2006 (chi2 for linear trend, P value of <0.001). Among 112 bovine-source and 18 human-source isolates, 49 (43.8%) and 12 (66.7%) were resistant to ceftazidime, respectively. Multiple-locus variable-number tandem-repeat analysis (MLVA) and plasmid profiling suggested that resistance was acquired by multiple independent genetic events within the WA-TYP035/187 clade. Given the lack of an obvious reservoir in species other than cattle and a parallel rise in ceftiofur resistance in the bovine-specific serovar Salmonella enterica serovar Dublin in the same time frame and region, selection pressure due to the use of the expanded-spectrum cephalosporin drug ceftiofur in cattle is a likely factor driving the increasing cephalosporin resistance of WA-TYP035/187.

Prevalence of Fecal Carriage of Acquired Expanded-Spectrum Cephalosporin Resistance in Enterobacteriaceae Strains from Cattle in France

In gram-negative pathogens, extended-spectrum beta-lactamases (ESBLs) confer resistance to penicillins, cephalosporins (including extended-spectrum cephalosporins), and aztreonam, but not to cephamycins and carbapenems, and are inhibited by beta-lactamase inhibitors ([8][1]). Recently, cefotaximases

Mechanisms of resistance to expanded-spectrum cephalosporins in Escherichia coli isolates recovered in a Spanish hospital

To characterize the beta-lactamase genes of the expanded-spectrum cephalosporin-resistant Escherichia coli isolates recovered in a Spanish hospital during the March 2002-March 2003 period. Thirty-four of the 1700 E. coli isolates recovered from unrelated patients in a Spanish hospital showed expanded-spectrum cephalosporin resistance. The presence of genes encoding TEM, SHV, CTX-M, CMY-2-type or FOX beta-lactamases as well as the existence of mutations in the regulatory region of the chromosomal ampC gene were studied by PCR and sequencing in these 34 E. coli isolates. The following extended-spectrum beta-lactamases (ESBLs) or plasmidic class C beta-lactamase genes were detected (number of isolates): bla(CTX-M-14) (14), bla(CTX-M-9) (4), bla(CTX-M-32) (1), bla(TEM-52) (2), bla(SHV-12) (3) and bla(CMY-2) (2). The remaining eight isolates showed a mutation in the promoter/attenuator region of the ampC chromosomal gene at position -42, in combination with mutations at positions -18, -1 and +58. The bla(TEM-1) gene was also detected in 12 of the ESBL-producing isolates, in both CMY-2-producing isolates and in four of the eight isolates that showed a mutation at position -42 of the ampC promoter. Other mutations in the promoter/attenuator region were detected in association with ESBL or CMY-2 genes, such as the combination -18, -1 and +58, -28 and +58, or +22, +26, +27 and +32. No clonal relationship was found among the CTX-M-producing E. coli isolates by PFGE with XbaI enzyme. Approximately 1.5% of the E. coli isolates of our hospital harboured ESBL genes, those of the CTX-M-9 group being the most common ones.

Extended-Spectrum β-Lactamases in Escherichia coli Isolated from Dogs and Cats in Rome, Italy, from 2001 to 2003

We report expanded-spectrum cephalosporin resistance in Escherichia coli from dogs and cats in Rome, Italy. Three major beta-lactamases (CMY-2, SHV-12, and CTX-M-1) are reported for the first time in E. coli from sick and healthy dogs and cats. Molecular characterization suggests the presence of several combinations of beta-lactamase genes in E. coli from companion animals.

Korean nationwide surveillance of antimicrobial resistance in 2000 with special reference to vancomycin resistance in enterococci, and expanded-spectrum cephalosporin and imipenem resistance in gram-negative bacilli.

Antimicrobial resistance surveillance is necessary to determine the size of the problem and to guide empirical selection of antimicrobial agents for treating infected patients. The aim of this study was to analyze the results of susceptibility tests performed by hospitals participating in the Korean Nationwide Surveillance of Antimicrobial Resistance (KONSAR) program. The rates of oxacillin-resistant staphylococci, penicillin-nonsusceptible pneumococci, and ampicillin-resistant E. faecium were over 70%. Ampicillin-resistant H. influenzae increased to 68%. Expanded-spectrum cephalosporin-resistant K. pneumoniae, fluoroquinolone-resistant E. coli, and imipenem-resistant P. aeruginosa remained at 16% through 27%, depending on the species. The proportions of vancomycin- resistant E. faecium and imipenem-resistant P. aeruginosa were 18 - 24% and 19-21%, respectively, indicating the seriousness of antimicrobial resistance. In conclusion, the increasing prevalence of resistant bacteria indicates that more concerted effort is required to conserve the usefulness of precious new antimicrobial agents.

GES-2, a class A beta-lactamase from Pseudomonas aeruginosa with increased hydrolysis of imipenem.

Pseudomonas aeruginosa GW-1 was isolated in 2000 in South Africa from blood cultures of a 38-year-old female who developed nosocomial pneumonia. This isolate harbored a self-transferable ca. 100-kb plasmid that conferred an expanded-spectrum cephalosporin resistance profile associated with an intermediate susceptibility to imipenem. A beta-lactamase gene, bla(GES-2), was cloned from whole-cell DNA of P. aeruginosa GW-1 and expressed in Escherichia coli. GES-2, with a pI value of 5.8, hydrolyzed expanded-spectrum cephalosporins, and its substrate profile was extended to include imipenem compared to that of GES-1, identified previously in Klebsiella pneumoniae. GES-2 activity was less inhibited by clavulanic acid, tazobactam and imipenem than GES-1. The GES-2 amino acid sequence differs from that of GES-1 by a glycine-to-asparagine substitution in position 170 located in the omega loop of Ambler class A enzymes. This amino acid change may explain the extension of the substrate profile of the plasmid-encoded beta-lactamase GES-2.

Characterization of expanded-spectrum cephalosporin resistance in E. coli isolates associated with bovine calf diarrhoeal disease.

Antibiotic resistance among Escherichia coli isolates from diarrhoeal disease in cattle was studied. Many of the isolates were multiply resistant to beta-lactams, including expanded-spectrum cephalosporins, aminoglycosides, sulphonamides, tetracycline and fluoroquinolones. In many of the isolates, IEF revealed a strong beta-lactamase band compatible with overexpression of the AmpC beta-lactamase, either alone or in addition to TEM-type enzymes. Several of the isolates also possessed genes encoding virulence factors associated with animal and human diarrhoeal diseases. These results suggest that the use of antibiotics in animals could lead to a reservoir of antibiotic-resistant bacteria that could potentially infect humans.