ceftazidime and Cross-Infection

Topics: Acinetobacter baumannii; Acinetobacter Infections; Anti-Bacterial Agents; Cross Infection; Drug Resistance, Bacterial; Drug Resistance, Multiple, Bacterial; Humans

In vitro activities of colistin and other drugs were tested against 221 Klebsiella pneumoniae isolates that were collected between 2006 and 2007 in nine tertiary care South Korean hospitals from patients with bacteremia. The clonality of colistin-resistant K. pneumoniae (CRKP) isolates was assessed by multilocus sequence typing (MLST). We found that 15 isolates (6.8%) were resistant to colistin. MLST showed that CRKP isolates were nonclonal, with colistin resistance in K. pneumoniae occurring independently and not by clonal spreading.

Topics: Anti-Bacterial Agents; Bacteremia; Colistin; Cross Infection; Drug Resistance, Bacterial; Humans; Klebsiella Infections; Klebsiella pneumoniae; Microbial Sensitivity Tests; Population Surveillance; Republic of Korea

The resistance mechanism of 49 Enterobacteriaceae isolates with decreased susceptibility to carbapenems collected from 2004 to 2008 at 16 teaching hospitals in China was investigated. Moderate- to high-level carbapenem resistance in most isolates was more closely associated with loss or decreased expression of both major porins combined with production of AmpC or extended-spectrum beta-lactamase enzymes, while KPC-2, IMP-4, and IMP-8 carbapenemase production may lead to a low to moderate level of carbapenem resistance in Enterobacteriaceae in China.

Topics: Anti-Bacterial Agents; Bacterial Outer Membrane Proteins; Bacterial Proteins; beta-Lactamases; Carbapenems; China; Cross Infection; Drug Resistance, Bacterial; Electrophoresis, Gel, Pulsed-Field; Enterobacteriaceae; Enterobacteriaceae Infections; Genotype; Integrons; Microbial Sensitivity Tests; Phenotype; Population Surveillance; Porins; Reverse Transcriptase Polymerase Chain Reaction

A Pseudomonas aeruginosa isolate recovered in Belgium produced a novel extended-spectrum ss-lactamase, BEL-2, differing from BEL-1 by a single Leu162Phe substitution. That modification significantly altered the kinetic properties of the enzyme, increasing its affinity for expanded-spectrum cephalosporins. The bla(BEL-2) gene was identified from a P. aeruginosa isolate clonally related to another bla(BEL-1)-positive isolate.

Topics: Belgium; beta-Lactamases; Cephalosporinase; Cephalosporins; Cross Infection; Escherichia coli; Genes, Bacterial; Humans; Kinetics; Microbial Sensitivity Tests; Pseudomonas aeruginosa; Pseudomonas Infections

We describe the activity of a novel cephalosporin, CXA-101 (FR26 4205), against a panel of highly resistant Pseudomonas aeruginosa isolates collected from U.S. hospitals. CXA-101 demonstrated increased potency against this population of resistant isolates, with activity that is 4- to 10-fold higher than that of comparator agents in each phenotypic category. The addition of tazobactam did not improve its activity. CXA-101 appears to be a promising addition to the category of antipseudomonal beta-lactams.

Topics: Adolescent; Adult; Aged; Anti-Bacterial Agents; Cephalosporins; Child; Child, Preschool; Cross Infection; Drug Combinations; Drug Resistance, Multiple, Bacterial; Humans; Infant; Microbial Sensitivity Tests; Middle Aged; Penicillanic Acid; Pseudomonas aeruginosa; Tazobactam; Young Adult

CXA-101, previously designated FR264205, is a new antipseudomonal cephalosporin. We evaluated the activity of CXA-101 against a highly challenging collection of beta-lactam-resistant Pseudomonas aeruginosa mutants selected in vitro and after antipseudomonal treatment of intensive care unit (ICU) patients. The in vitro mutants investigated included strains with multiple combinations of mutations leading to several degrees of AmpC overexpression (ampD, ampDh2, ampDh3, and dacB [PBP4]) and porin loss (oprD). CXA-101 remained active against even the AmpD-PBP4 double mutant (MIC = 2 microg/ml), which shows extremely high levels of AmpC expression. Indeed, this mutant showed high-level resistance to all tested beta-lactams, except carbapenems, including piperacillin-tazobactam (PTZ), aztreonam (ATM), ceftazidime (CAZ), and cefepime (FEP), a cephalosporin considered to be relatively stable against hydrolysis by AmpC. Moreover, CXA-101 was the only beta-lactam tested (including the carbapenems imipenem [IMP] and meropenem [MER]) that remained fully active against the OprD-AmpD and OprD-PBP4 double mutants (MIC = 0.5 microg/ml). Additionally, we tested a collection of 50 sequential isolates that were susceptible or resistant to penicillicins, cephalosporins, carbapenems, or fluoroquinolones that emerged during treatment of ICU patients. All of the mutants resistant to CAZ, FEP, PTZ, IMP, MER, or ciprofloxacin showed relatively low CXA-101 MICs (range, 0.12 to 4 microg/ml; mean, 1 to 2 microg/ml). CXA-101 MICs of pan-beta-lactam-resistant strains ranged from 1 to 4 microg/ml (mean, 2.5 microg/ml). As described for the in vitro mutants, CXA-101 retained activity against the natural AmpD-PBP4 double mutants, even when these exhibited additional overexpression of the MexAB-OprM efflux pump. Therefore, clinical trials are needed to evaluate the usefulness of CXA-101 for the treatment of P. aeruginosa nosocomial infections, particularly those caused by multidrug-resistant isolates that emerge during antipseudomonal treatments.

Topics: Anti-Bacterial Agents; Bacterial Proteins; beta-Lactam Resistance; beta-Lactamases; Cephalosporins; Cross Infection; Humans; Intensive Care Units; Microbial Sensitivity Tests; Mutation; Pseudomonas aeruginosa; Pseudomonas Infections

From 2002 to 2008, there was a significant increase in extended-spectrum beta-lactamase (ESBL)-positive Escherichia coli isolates in European intra-abdominal infections, from 4.3% in 2002 to 11.8% in 2008 (P < 0.001), but not for ESBL-positive Klebsiella pneumoniae isolates (16.4% to 17.9% [P > 0.05]). Hospital-associated isolates were more common than community-associated isolates, at 14.0% versus 6.5%, respectively, for E. coli (P < 0.001) and 20.9% versus 5.3%, respectively, for K. pneumoniae (P < 0.01). Carbapenems were consistently the most active drugs tested.

Topics: Abdomen; Anti-Bacterial Agents; beta-Lactamases; Carbapenems; Cross Infection; Escherichia coli; Escherichia coli Infections; Humans; Klebsiella Infections; Klebsiella pneumoniae

The mechanisms responsible for the increasing prevalence of colistin-only-sensitive (COS) Pseudomonas aeruginosa isolates in a Spanish hospital were investigated. Pulsed-field gel electrophoresis revealed that 24 (50%) of the studied isolates belonged to the same clone, identified as the internationally spread sequence type 235 (ST235) through multilocus sequence typing. In addition to several mutational resistance mechanisms, an integron containing seven resistance determinants was detected. Remarkably, the extended-spectrum beta-lactamase GES-1 and its Gly170Ser carbapenem-hydrolyzing derivative GES-5 were first documented to be encoded in a single integron. This work is the first to describe GES enzymes in Spain and adds them to the growing list of beta-lactamases of concern (PER, VIM, and OXA) detected in ST235 clone isolates.

Topics: Anti-Bacterial Agents; Base Sequence; beta-Lactamases; Colistin; Cross Infection; Humans; Molecular Sequence Data; Pseudomonas aeruginosa

Topics: Acinetobacter baumannii; Acinetobacter Infections; Anti-Bacterial Agents; beta-Lactamases; Carbapenems; Chromosomes, Bacterial; Cross Infection; Disease Outbreaks; DNA, Bacterial; Drug Resistance, Bacterial; Edetic Acid; Greece; Humans; Imipenem; Integrons; Isoelectric Focusing; Microbial Sensitivity Tests; Molecular Sequence Data; Sequence Analysis, DNA

The basis of the beta-lactam resistance of 39 multidrug-resistant Acinetobacter baumannii isolates recovered from hospitalized patients was studied. These isolates were collected from 2001 to 2005 at the Sahloul Hospital in Sousse, Tunisia. They belonged to two distinct clones. One clone that grouped 19 isolates produced a carbapenem-hydrolyzing oxacillinase, OXA-97, that differed from OXA-58 by a single amino acid substitution and conferred the same beta-lactam resistance profile as OXA-58. The bla(OXA-97) gene was located on plasmids that varied in size in 18 isolates and was chromosomally located in a single isolate. Cloning and sequencing identified genetic structures surrounding the bla(OXA-97) gene similar to those reported to be adjacent to the bla(OXA-58) gene. In addition, the novel ISAba8 element (which is of the IS21 family) was identified. This is the first report of the nosocomial spread of carbapenemase producers in A. baumannii isolates in Africa.

Topics: Acinetobacter baumannii; Africa; Bacterial Proteins; beta-Lactamases; Blotting, Southern; Carbapenems; Cross Infection; Drug Resistance, Bacterial; Humans; Microbial Sensitivity Tests; Models, Genetic; Molecular Sequence Data; Polymerase Chain Reaction; Tunisia

The oxacillinase gene was reported to confer limited resistance to carbapenem in Acinetobacter baumannii. In this study, we have demonstrated that an A. baumannii clinical isolate harboring a plasmid, pTVICU53, has 11,037 bp encoding 13 open reading frames. A bla(OXA-58) gene with an upstream insertion of truncated ISAba3 (DeltaISAba3) and IS1008 was found in this plasmid. DeltaISAba3and IS1008 provided two independent promoters for the transcription control of the bla(OXA-58) gene. The transformation of pTVICU53 or a shuttle vector bearing IS1008-DeltaISAba3-bla(OXA-58) to different A. baumannii recipients can increase their MICs of carbapenem 64- to 256-fold. The deletion of promoters provided by IS1008 resulted in dramatic decreases in bla(OXA-58) transcription and a 32- to 64-fold reduction in the carbapenem MIC. These findings highlight that A. baumannii might develop carbapenem resistance with a single transformation step, taking up a plasmid containing a genetic construct with a potentially high level of transcription of the bla(OXA-58) gene.

Topics: Acinetobacter baumannii; Acinetobacter Infections; Base Sequence; beta-Lactam Resistance; beta-Lactamases; Carbapenems; Cross Infection; DNA Primers; DNA Transposable Elements; DNA, Bacterial; Genes, Bacterial; Humans; Microbial Sensitivity Tests; Molecular Sequence Data; Plasmids; Promoter Regions, Genetic; Transformation, Genetic

During 2003, 40 carbapenem-resistant Pseudomonas aeruginosa clinical isolates collected in a Mexican tertiary-care hospital were screened for metallo-beta-lactamase production. Thirteen isolates produced IMP-15, and 12 had a single pulsed-field gel electrophoresis pattern. The bla(IMP-15) gene cassette was inserted in a plasmid-borne integron with a unique array of gene cassettes and was named In95.

Topics: Bacterial Proteins; beta-Lactamases; Cross Infection; Electrophoresis, Gel, Pulsed-Field; Humans; Integrons; Mexico; Models, Genetic; Molecular Sequence Data; Pseudomonas aeruginosa; Pseudomonas Infections

The first outbreak of carbapenem-resistant Klebsiella pneumoniae isolates producing the plasmid-encoded carbapenem-hydrolyzing oxacillinase OXA-48 is reported. The 39 isolates belonged to two different clones and were collected at the University Hospital of Istanbul, Turkey, from May 2006 to February 2007, and they coproduced various beta-lactamases (SHV-12, OXA-9, and TEM-1 for clone A and CTX-M-15, TEM-1, and OXA-1 for clone B).

Topics: Bacterial Proteins; beta-Lactamases; Carbapenems; Cross Infection; Drug Resistance, Bacterial; Electrophoresis, Gel, Pulsed-Field; Humans; Klebsiella Infections; Klebsiella pneumoniae; Microbial Sensitivity Tests; Models, Genetic; Turkey

We investigated the basis of the carbapenem resistance of 17 multidrug-resistant Acinetobacter baumannii clinical isolates collected from 2004 to 2005 at the Saint George University Hospital in Beirut, Lebanon. A. baumannii isolates were clonally related and were susceptible to colistin and trimethoprim-sulfamethoxazole, susceptible or intermediate to ampicillin-sulbactam and meropenem, and resistant to all other antimicrobials. Conjugation experiments demonstrated that resistance to imipenem could be transferred along with a plasmid containing the carbapenem-hydrolyzing oxacillinase bla(OXA-58) gene. The plasmid that we called pABIR was 29,823 bp in size and showed a novel mosaic structure composed of two origins of replication, four insertion sequence (IS) elements, and 28 open reading frames. The bla(OXA-58) gene was flanked by IS18 and ISAba3 elements at the 5' and 3' ends, respectively. The production of the carbapenem-hydrolyzing oxacillinase OXA-58 was apparently the only mechanism for carbapenem resistance in A. baumannii isolates causing the outbreak at the Lebanese Hospital.

Topics: Acinetobacter baumannii; Acinetobacter Infections; Anti-Bacterial Agents; beta-Lactam Resistance; beta-Lactamases; Conjugation, Genetic; Cross Infection; Disease Outbreaks; Drug Resistance, Multiple, Bacterial; Genes, Bacterial; Hospitals, University; Humans; Imipenem; Lebanon; Molecular Epidemiology; Molecular Sequence Data; Plasmids

A total of 49 unique clinical isolates of multidrug-resistant (MDR) Acinetobacter baumannii identified at a tertiary medical center in Pittsburgh, Pennsylvania, between August 2006 and September 2007 were studied for the genetic basis of their MDR phenotype. Approximately half of all A. baumannii clinical isolates identified during this period qualified as MDR, defined by nonsusceptibility to three or more of the antimicrobials routinely tested in the clinical microbiology laboratory. Among the MDR isolates, 18.4% were resistant to imipenem. The frequencies of resistance to amikacin and ciprofloxacin were high at 36.7% and 95.9%, respectively. None of the isolates was resistant to colistin or tigecycline. The presence of the carbapenemase gene bla(OXA-23) and the 16S rRNA methylase gene armA predicted high-level resistance to imipenem and amikacin, respectively. bla(OXA-23) was preceded by insertion sequence ISAba1, which likely provided a potent promoter activity for the expression of the carbapenemase gene. The structure of the transposon defined by ISAba1 differed from those reported in Europe, suggesting that ISAba1-mediated acquisition of bla(OXA-23) may occur as an independent event. Typical substitutions in the quinolone resistance-determining regions of the gyrA and parC genes were observed in the ciprofloxacin-resistant isolates. Plasmid-mediated quinolone resistance genes, including the qnr genes, were not identified. Fifty-nine percent of the MDR isolates belonged to a single clonal group over the course of the study period, as demonstrated by pulsed-field gel electrophoresis.

Topics: Academic Medical Centers; Acinetobacter baumannii; Acinetobacter Infections; Amikacin; Base Sequence; beta-Lactamases; Cross Infection; DNA Primers; Drug Resistance, Multiple, Bacterial; Electrophoresis, Gel, Pulsed-Field; Genes, Bacterial; Humans; Microbial Sensitivity Tests; Molecular Epidemiology; Pennsylvania; Polymerase Chain Reaction

A Klebsiella pneumoniae strain resistant to third-generation cephalosporins was isolated in the eastern Netherlands. The strain was found to carry a novel extended-spectrum beta-lactamase, namely, SHV-31. The combination of the two mutations by which SHV-31 differs from SHV-1, namely, L35Q and E240K, had previously only been described in association with one or more additional mutations.

Topics: Anti-Bacterial Agents; beta-Lactamases; Cross Infection; Disease Outbreaks; Drug Resistance, Multiple, Bacterial; Humans; Intensive Care Units; Isoelectric Focusing; Klebsiella Infections; Klebsiella pneumoniae; Microbial Sensitivity Tests; Molecular Sequence Data; Netherlands; Plasmids

Of the 181 unduplicated Escherichia coli strains isolated in nine different hospitals in three Portuguese regions, 119 were extended-spectrum beta-lactamase (ESBL)-CTX-M producers and were selected for phenotype and genotype characterization. CTX-M producer strains were prevalent among community-acquired infections (56%), urinary tract infections (76%), and patients >/=60 years old (76%). In MIC tests, all strains were resistant to cefotaxime, 92% were resistant to ceftazidime, 93% were resistant to quinolones, 89% were resistant to aminoglycoside, and 26% were resistant to trimethoprim-sulfamethoxazole; all strains were sensitive to carbapenems, and 92% of the strains had a multidrug resistance phenotype. Molecular methods identified 109 isolates harboring a bla(CTX-M-15) gene, 1 harboring the bla(CTX-M-32) gene (first identification in the country), and 9 harboring the bla(CTX-M-14) gene. All isolates presented the ISEcp1 element upstream from the bla(CTX-M) genes; one presented the IS903 element (downstream of bla(CTX-M-14) gene), and none had the IS26 element; 85% carried bla(TEM-1B), and 84% also carried a bla(OXA-30). Genetic relatedness analysis based on pulsed-field gel electrophoresis defined five clusters and indicated that 76% of all isolates (from cluster IV) corresponded to a single epidemic strain. Of the 47 strains from one hospital, 41 belonged to cluster IV and were disseminated in three main wards. CTX-M-producing E. coli strains are currently a problem in Portugal, with CTX-M-15 particularly common. This study suggests that the horizontal transfer of bla(CTX-M) genes, mediated by plasmids and/or mobile elements, contributes to the dissemination of CTX-M enzymes to community and hospital environments. The use of extended-spectrum cephalosporins, quinolones, and aminoglycosides is compromised, leaving carbapenems as the therapeutic option for severe infections caused by ESBL producers.

Topics: Aged; Anti-Bacterial Agents; beta-Lactamases; Community-Acquired Infections; Cross Infection; Drug Resistance, Bacterial; Escherichia coli; Escherichia coli Infections; Escherichia coli Proteins; Humans; Microbial Sensitivity Tests; Middle Aged; Portugal

Bloodstream infections (BSI) caused by extended-spectrum beta-lactamase (ESBL)-producing organisms markedly increase the rates of treatment failure and death. We conducted a retrospective cohort analysis to identify risk factors for mortality in adult in-patients with BSI caused by ESBL-producing Enterobacteriaceae (ESBL-BSI). Particular attention was focused on defining the impact on the mortality of inadequate initial antimicrobial therapy (defined as the initiation of treatment with active antimicrobial agents >72 h after collection of the first positive blood culture). A total of 186 patients with ESBL-BSI caused by Escherichia coli (n = 104), Klebsiella pneumoniae (n = 58), or Proteus mirabilis (n = 24) were identified by our microbiology laboratory from 1 January 1999 through 31 December 2004. The overall 21-day mortality rate was 38.2% (71 of 186). In multivariate analysis, significant predictors of mortality were inadequate initial antimicrobial therapy (odds ratio [OR] = 6.28; 95% confidence interval [CI] = 3.18 to 12.42; P < 0.001) and unidentified primary infection site (OR = 2.69; 95% CI = 1.38 to 5.27; P = 0.004). The inadequately treated patients (89 of 186 [47.8%]) had a threefold increase in mortality compared to the adequately treated group (59.5% versus 18.5%; OR = 2.38; 95% CI = 1.76 to 3.22; P < 0.001). The regimens most commonly classified as inadequate were based on oxyimino cephalosporin or fluoroquinolone therapy. Prompt initiation of effective antimicrobial treatment is essential in patients with ESBL-BSI, and empirical decisions must be based on a sound knowledge of the local distribution of pathogens and their susceptibility patterns.

Topics: Adult; Aged; Anti-Bacterial Agents; Bacteremia; beta-Lactamases; Cross Infection; Drug Resistance, Bacterial; Enterobacteriaceae; Enterobacteriaceae Infections; Escherichia coli; Female; Humans; Klebsiella pneumoniae; Male; Microbial Sensitivity Tests; Middle Aged; Predictive Value of Tests; Proteus mirabilis; Risk Factors; Survival Analysis; Treatment Outcome

Clinical isolates of Acinetobacter baumannii (n = 470) were collected during a 7-year period and investigated for the genetic determinants of resistance to expanded-spectrum beta-lactams. Thirty-one isolates produced the TEM-92 extended-spectrum beta-lactamase (ESBL) and were clonally related. This is the first report of A. baumannii producing a TEM-type ESBL.

Topics: Acinetobacter baumannii; Acinetobacter Infections; Anti-Bacterial Agents; beta-Lactam Resistance; beta-Lactamases; beta-Lactams; Cross Infection; Humans; Italy; Microbial Sensitivity Tests

A prospective observational study was conducted to identify factors associated with bloodstream infections (BSIs) caused by integron-carrying Enterobacteriaceae and to evaluate the clinical significance of integron carriage. Consecutive patients with Enterobacteriaceae BSIs were identified and followed up until discharge or death. Identification of blood isolates and susceptibility testing were performed by the Wider I automated system. int-1-specific PCR, conserved-segment PCR, and DNA sequencing were used to determine the presence, length, and content of integrons. The relatedness among the isolates was examined by pulsed-field gel electrophoresis. Two hundred fifty episodes of Enterobacteriaceae BSI occurred in 233 patients; 109 (43.6%) were nosocomial, 82 (32.8%) were community acquired, and 59 (23.6%) were health care associated. Integrons were detected in 11 (13.4%) community-acquired, 24 (40.7%) health care-associated, and 46 (42.2%) nosocomial isolates. Integron-carrying organisms were more likely to exhibit resistance to three or more classes of antimicrobials (odds ratio [OR], 9.84; 95% confidence interval [95% CI], 5.31 to 18.23; P < 0.001) or to produce extended-spectrum beta-lactamases (OR, 5.75; 95% CI, 2.38 to 13.89; P < 0.001) or a VIM-type metallo-beta-lactamase (P, 0.003). Inter- or intraspecies integron transfer and cross-transmission of integron-carrying clones were observed. Use of cotrimoxazole (OR, 4.77; 95% CI, 1.81 to 12.54; P < 0.001) and a nosocomial or other health care setting (OR, 3.07; 95% CI, 1.30 to 7.22; P, 0.01) were independently associated with BSIs caused by integron-carrying Enterobacteriaceae. Patients with a nonurinary source of bacteremia (OR, 9.46; 95% CI, 2.77 to 32.32; P < 0.001) and a Pitt bacteremia score of > or =4 (OR, 23.36; 95% CI, 7.97 to 68.44; P < 0.001) had a significantly higher 14-day mortality rate, whereas integron carriage did not affect clinical outcomes. These findings may have implications affecting antibiotic policies and infection control measures.

Topics: Bacteremia; Community-Acquired Infections; Cross Infection; DNA, Bacterial; Drug Resistance, Multiple, Bacterial; Electrophoresis, Gel, Pulsed-Field; Enterobacteriaceae Infections; Gene Transfer, Horizontal; Humans; Infectious Disease Transmission, Professional-to-Patient; Integrons; Microbial Sensitivity Tests; Nucleic Acid Amplification Techniques; Polymerase Chain Reaction; Prospective Studies; Risk Factors; Sequence Analysis, DNA; Treatment Outcome

Seven bla(IMP-1)-harboring Acinetobacter sp. isolates and one Pseudomonas putida clinical isolate were recovered from hospitalized patients. All isolates possessed a class 1 integron, named In86, carrying the same cassette array [bla(IMP1), aac(6')-31, and aadA1], which was plasmid located in five of the isolates. This report describes the ability of nonfermentative nosocomial pathogens to acquire and disseminate antimicrobial resistance determinants.

Topics: Acinetobacter; Amino Acid Sequence; Aminoglycosides; Anti-Bacterial Agents; Base Sequence; Brazil; Codon, Terminator; Cross Infection; Drug Resistance, Multiple, Bacterial; Gene Transfer, Horizontal; Genes, Bacterial; Hospitals; Humans; Integrons; Microbial Sensitivity Tests; Molecular Sequence Data; Open Reading Frames; Plasmids; Pseudomonas putida; Transcription, Genetic

Topics: Acinetobacter; Acinetobacter baumannii; Acinetobacter Infections; Bacterial Proteins; beta-Lactamases; Cross Infection; Humans; Plasmids; Portugal

Carbapenem resistance in Acinetobacter spp. is an emerging problem in China. We investigated the molecular epidemiology and carbapenemase genes of 221 nonrepetitive imipenem-resistant clinical isolates of Acinetobacter spp. collected from 1999 to 2005 at 11 teaching hospitals in China. Genotyping by pulsed-field gel electrophoresis (PFGE) found 15 PFGE patterns. Of these, one (clone P) was identified at four hospitals in Beijing and another (clone A) at four geographically disparate cities. Most imipenem-resistant isolates exhibited high-level resistance to all beta-lactams and were only susceptible to colistin. bla(OXA-23)-like genes were found in 97.7% of isolates. Sequencing performed on 60 representative isolates confirmed the presence of the bla(OXA-23) carbapenemase gene. Analysis of the genetic context of bla(OXA-23) showed the presence of ISAba1 upstream of bla(OXA-23). All of the 187 A. baumannii isolates identified by amplified RNA gene restriction analysis carried a bla(OXA-51)-like oxacillinase gene, while this gene was absent from isolates of other species. Sequencing indicated the presence of bla(OXA-66) for 18 representative isolates. Seven isolates of one clone (clone T) carried the plasmid-mediated bla(OXA-58) carbapenemase gene, while one isolate of another clone (clone L) carried the bla(OXA-72) carbapenemase gene. Only 1 isolate of clone Q carried the bla(IMP-8) metallo-beta-lactamase gene, located in a class 1 integron. Of 221 isolates, 77.8% carried bla(PER-1)-like genes. Eleven different structures of class 1 integrons were detected, and most integrons carried genes mediating resistance to aminoglycosides, rifampin, and chloramphenicol. These findings indicated clonal spread of imipenem-resistant Acinetobacter spp. and wide dissemination of the OXA-23 carbapenemase in China.

Topics: Acinetobacter; Acinetobacter Infections; Aminoglycosides; Anti-Bacterial Agents; Bacterial Proteins; beta-Lactamases; beta-Lactams; Blotting, Southern; Carbapenems; China; Chloramphenicol; Colistin; Cross Infection; Drug Resistance, Multiple, Bacterial; Electrophoresis, Gel, Pulsed-Field; Hospitals; Humans; Imipenem; Integrons; Microbial Sensitivity Tests; Molecular Epidemiology; Molecular Sequence Data; Rifampin; Sequence Analysis, DNA

All (236) Pseudomonas aeruginosa isolates resistant to imipenem and/or meropenem collected during a multicenter (127-hospital) study in Spain were analyzed. Carbapenem-resistant isolates were found to be more frequently resistant to all beta-lactams and non-beta-lactam antibiotics than carbapenem-susceptible isolates (P < 0.001), and up to 46% of the carbapenem-resistant isolates met the criteria used to define multidrug resistance (MDR). Pulsed-field gel electrophoresis revealed remarkable clonal diversity (165 different clones were identified), and with few exceptions, the levels of intra- and interhospital dissemination of clones were found to be low. Carbapenem resistance was driven mainly by the mutational inactivation of OprD, accompanied or not by the hyperexpression of AmpC or MexAB-OprM. Class B carbapenemases (metallo-beta-lactamases [MBLs]) were detected in a single isolate, although interestingly, this isolate belonged to one of the few epidemic clones documented. The MBL-encoding gene (bla(VIM-2)), along with the aminoglycoside resistance determinants, was transferred to strain PAO1 by electroporation, demonstrating its plasmid location. The class 1 integron harboring bla(VIM-2) was characterized as well, and two interesting features were revealed: intI1 was found to be disrupted by a 1.1-kb insertion sequence, and a previously undescribed aminoglycoside acetyltransferase-encoding gene [designated aac(6')-32] preceded bla(VIM-2). AAC(6')-32 showed 80% identity to AAC(6')-Ib' and the recently described AAC(6')-31, and when aac(6')-32 was cloned into Escherichia coli, it conferred resistance to tobramycin and reduced susceptibility to gentamicin and amikacin. Despite the currently low prevalence of epidemic clones with MDR, active surveillance is needed to detect and prevent the dissemination of these clones, particularly those producing integron- and plasmid-encoded MBLs, given their additional capacity for the intra- and interspecies spread of MDR.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Bacterial Proteins; beta-Lactam Resistance; beta-Lactamases; Carbapenems; Chromosomes, Bacterial; Cross Infection; DNA, Bacterial; Drug Resistance, Multiple, Bacterial; Electrophoresis, Gel, Pulsed-Field; Integrons; Molecular Epidemiology; Molecular Sequence Data; Mutation; Plasmids; Polymerase Chain Reaction; Porins; Pseudomonas aeruginosa; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Spain