Search

Objectives: Mycobacterium kansasii causes a variety of infections. Although previous reports on the prognosis of antimicrobial therapy have been mostly satisfactory, problems involving treatment failure or relapse have been encountered. The purpose of this study was to establish a relationship between the clinical treatment outcomes of M. kansasii infections and bacterial drug susceptibility, and their clonality. [ABSTRACT FROM PUBLISHER]

Objectives: The aim of the study was to characterize the genetic basis of β-lactam resistance developed in clinical isolates of Klebsiella pneumoniae after exposure to cefuroxime.Methods: Clinical features of two episodes of liver abscess caused by K. pneumoniae in a diabetic patient were reported. Four isolates (KP1/KP2 and KP3/KP4) of K. pneumoniae were recovered from cultures of blood/pus in the first and second episodes, respectively. Laboratory investigation of the K. pneumoniae isolates included genotyping by PFGE, resistance gene analysis by PCR amplification and DNA sequencing, and outer membrane protein analysis by SDS–PAGE.Results: KP3 and KP4 were recovered after a 21 day cefuroxime therapy and demonstrated identical genotypes to that of KP1 and KP2. However, compared with KP1 and KP2, emerging resistance to piperacillin, cefalotin, cefuroxime and cefoxitin was observed. The other antibiotics tested, except ampicillin, retained the same effectiveness against the four isolates, although increases (4- to 8-fold) in the MICs of cefotaxime, ceftriaxone, ceftazidime, cefepime, flomoxef and aztreonam were observed in KP3 and KP4. None of the isolates produced extended-spectrum β-lactamases or plasmid-mediated AmpC β-lactamases. Deficiency in the expression of an outer membrane protein (OmpK35) was observed in the cefuroxime-resistant isolates, KP3 and KP4.Conclusions: The increased resistance to cephalosporins in these clinical isolates of K. pneumoniae after exposure to cefuroxime might be related to the loss of OmpK35. [ABSTRACT FROM AUTHOR]

Objectives: The dissemination of cephamycin resistance in Enterobacteriaceae and its correlation with a transposon-like DNA element consisting of a specific tnpA-blaCMY-2-blc-sugE structure were investigated.Methods: A total of 140 enterobacterial isolates belonging to 17 species (10 genera) of Enterobacteriaceae phenotypically characterized as putative AmpC-producers were evaluated. The isolates were examined by PCR analysis, DNA–DNA hybridization and nucleotide sequencing.Results: The blaCMY-2-carrying element was detected in 34 isolates from 10 species (9 genera), including all 14 Salmonella and 4 Shigella isolates as well as 7 of the 10 Escherichia coli isolates tested. The remaining 9 isolates were from 112 isolates of the other 14 species tested. The genetic structure of the blaCMY-2-carrying element was identical in 29 isolates, while in 3 E. coli and 2 Citrobacter isolates an additional insertion sequence IS1 was found inserted at various nucleotide positions close to the 3′ end, either within or downstream, of tnpA. In 12 of the 14 representative isolates examined, the blaCMY-2-carrying element was found inserted in the finQ gene of various-sized plasmids with highly conserved 8 bp direct repeats flanking the junction regions. Among the other 106 non-CMY-2-producing isolates, plasmid-mediated ampC genes were found only in one isolate of Enterobacter aerogenes which carried a blaDHA-1-like gene.Conclusions: blaCMY-2 is the most prevalent plasmid-mediated ampC gene among Enterobacteriaceae. All the blaCMY-2 genes identified in the present study were associated with a specific transposon-like element that may be responsible for the spread of blaCMY-2 among Enterobacteriaceae. [ABSTRACT FROM AUTHOR]

Objectives: Salmonella infection is a distressing health problem worldwide. This study reports the changing epidemiology of Salmonella infections in Taiwan during 1999–2003, with emphasis on increasing ceftriaxone resistance.Methods: Records of Salmonella clinical isolates in Chang Gung Memorial Hospital during 1999–2003 were reviewed. All isolates were identified and antimicrobial susceptibility determined by standard methods. A total of 22 ceftriaxone-resistant isolates were investigated by PCR sequencing of the blaTEM, blaSHV, blaCTX-M and ampC genes. Southern-blot hybridization was used to localize the ampC gene. Infrequent-restriction-site PCR was used to genotype these isolates.Results: A total of 3635 Salmonella isolates, including 3592 (98.8%) non-typhoid Salmonella, were identified. Serogroup B (55.6%) remained the most predominant, but the prevalence has been decreasing. In contrast, serogroup D infections have increased significantly from 13.6 to 22.8%. Overall resistance to ampicillin and chloramphenicol remained high, with the highest rate (91% to both drugs) observed in Salmonellaenterica serotype Choleraesuis in 2003. A sudden upsurge of ciprofloxacin resistance from zero to 69% was found in S. Choleraesuis. Ceftriaxone resistance increased in several serogroups (0.8–2.1%; average, 1.5%). The resistance was associated with plasmid-mediated blaCMY-2 in 14 cases and extended-spectrum β-lactamases (ESBLs), including CTX-M-3 (n=6), SHV-2a (n=1) and SHV-12 (n=1), in others. Diverse serotypes and genotypes were found among the ceftriaxone-resistant isolates.Conclusions: Increasing ceftriaxone resistance in non-typhoid Salmonella appears to link to the spread of plasmid-mediated ampC or ESBL genes. Effective measures should be taken to prevent the problem worsening. [ABSTRACT FROM AUTHOR]