gentamicin-sulfate and Cross-Infection

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

Eighteen identical VanB-type Enterococcus faecalis isolates that were obtained from different hospitalized patients were examined for their drug resistance and plasmid DNAs. Of the 18 strains, 12 strains exhibited resistance to erythromycin (Em), gentamicin (Gm), kanamycin (Km), tetracycline (Tc), and vancomycin (Van) and produced cytolysin (Hly/Bac) and a bacteriocin (Bac) active against E. faecalis strains. Another six of the strains exhibited resistance to Gm, Km, Tc, and Van and produced a bacteriocin. Em and Van resistance was transferred individually to E. faecalis FA2-2 strains at a frequency of about 10(-4) per donor cell by broth mating. The Em-resistant transconjugants and the Van-resistant transconjugants harbored a 65.7-kbp plasmid and a 106-kbp plasmid, respectively. The 106-kbp and 65.7-kbp plasmids isolated from the representative E. faecalis NKH15 strains were designated pMG2200 and pMG2201, respectively. pMG2200 conferred vancomycin resistance and bacteriocin activity on the host strain and responded to the synthetic pheromone cCF10 for pCF10, while pMG2201 conferred erythromycin resistance and cytolysin activity on its host strain and responded to the synthetic pheromone cAD1 for pAD1. The complete DNA sequence of pMG2200 (106,527 bp) showed that the plasmid carried a Tn1549-like element encoding vanB2-type resistance and the Bac41-like bacteriocin genes of pheromone-responsive plasmid pYI14. The plasmid contained the regulatory region found in pheromone-responsive plasmids and encoded the genes prgX and prgQ, which are the key negative regulatory elements for plasmid pCF10. pMG2200 also encoded TraE1, a key positive regulator of plasmid pAD1, indicating that pMG2200 is a naturally occurring chimeric plasmid that has a resulting prgX-prgQ-traE1 genetic organization in the regulatory region of the pheromone response. The functional oriT region and the putative relaxase gene of pMG2200 were identified and found to differ from those of pCF10 and pAD1. The putative relaxase of pMG2200 was classified as a member of the MOB(MG) family, which is found in pheromone-independent plasmid pHTbeta of the pMG1-like plasmids. This is the first report of the isolation and characterization of a pheromone-responsive highly conjugative plasmid encoding vanB resistance.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Bacterial Proteins; Bacteriocins; Blotting, Southern; Conjugation, Genetic; Cross Infection; Culture Media; DNA Nucleotidyltransferases; DNA, Bacterial; Drug Resistance, Bacterial; Electrophoresis, Gel, Pulsed-Field; Enterococcus faecalis; Erythromycin; Gram-Positive Bacterial Infections; Humans; Microbial Sensitivity Tests; Molecular Sequence Data; Perforin; Pheromones; Plasmids; Vancomycin Resistance

Methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) is a serious problem worldwide. To investigate the molecular epidemiology of MRSA isolates in China, a total of 702 MRSA isolates collected from 18 teaching hospitals in 14 cities between 2005 and 2006 were characterized by antibiogram analysis, pulsed-field gel electrophoresis (PFGE), staphylococcal cassette chromosome mec (SCCmec) typing, and spa typing; and 102 isolates were selected for multilocus sequence typing (MLST). Overall, SCCmec type III was the most popular type and was found in 541 isolates (77.1%), followed by SCCmec type II (109/702; 15.5%). Twenty-four PFGE types were obtained among 395 isolates collected in 2005, and 18 spa types were obtained among 702 isolates. spa type t030, which corresponded to PFEG types A to E, constituted 52.0% (365/702) of all isolates, and isolates of this type were present in all 14 cities; spa type t037, which corresponded to PFGE types F and G, accounted for 25.5% (179/702) of all isolates, and isolates of this type were identified in 12 cities. The two spa genotypes belonged to sequence type 239 (ST239) and carried SCCmec type III. spa type t002, which included isolates of PFGE types L to T, made up 16.0% (112/702) of the isolates that belonged to ST5 and SCCmec type II, and isolates of this type were distributed in 12 cities. The distribution of spa types varied among the regions. spa type t002 was the most common in Dalian (53.4%) and Shenyang (44.4%); spa type t037 was predominant in Shanghai (74.8%), whereas spa type t030 was the most common in the other cities. Two isolates from Guangzhou that harbored SCCmec type IVa with ST59 and ST88 were identified as community-associated MRSA. The prevalence of the Panton-Valentine leukocidin gene was 2.3%. The data documented two major epidemic MRSA clones, ST239-MRSA-SCCmec type III and ST5-MRSA-SCCmec type II, with unique geographic distributions across China.

Topics: Bacterial Proteins; China; Cross Infection; DNA, Bacterial; Electrophoresis, Gel, Pulsed-Field; Genotype; Hospitals, Teaching; Humans; Leukocidins; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Penicillin-Binding Proteins; Staphylococcal Infections

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

Rx-01_423 and Rx-01_667 are two members of the family of oxazolidinones that were designed using a combination of computational and medicinal chemistry and conventional biological techniques. The compounds have a two- to eightfold-improved potency over linezolid against serious gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant streptococci, and vancomycin-resistant enterococci. This enhanced potency extends to the coverage of linezolid-resistant gram-positive microbes, especially multidrug-resistant enterococci and pneumococci. Compounds from this series expand the spectrum compared with linezolid to include fastidious gram-negative organisms like Haemophilus influenzae and Moraxella catarrhalis. Like linezolid, the Rx-01 compounds are bacteriostatic against MRSA and enterococci but are generally bactericidal against S. pneumoniae and H. influenzae.

Topics: Anti-Infective Agents; Bacteria; Community-Acquired Infections; Cross Infection; Enterococcus; Humans; Methicillin Resistance; Microbial Sensitivity Tests; Molecular Structure; Oxazolidinones; Respiratory System; Staphylococcus; Staphylococcus aureus; Streptococcus; Streptococcus pneumoniae

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

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

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