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Objectives: To examine mutations within the penA, mtrR, porB, ponA and pilQ genes of Neisseria gonorrhoeae to determine their contribution to cephalosporin resistance.Methods: A total of 46 N. gonorrhoeae isolates with reduced susceptibility to cefixime or ceftriaxone (MICs > or = 0.12 mg/L) and two susceptible isolates were selected. The full sequence of penA and partial sequences previously reported as hot mutation sites of the other genes were analysed. Genotyping by N. gonorrhoeae multiantigen sequence typing (NG-MAST) was also performed.Results: A mosaic penicillin-binding protein 2 (PBP 2) was found in a single isolate that exhibited the highest cefixime MIC (0.5 mg/L). The majority of the isolates with reduced susceptibility to cephalosporins contained non-mosaic PBP 2 sequences, of which PBP 2 pattern XIII was most common (28/46). All isolates with reduced susceptibility to cephalosporins also had mtrR and porB mutations. Two susceptible isolates had the PBP 2 pattern XIV and an incomplete MtrR protein, which was a new mutation. Isolates with identical PBP 2 patterns comprised multiple NG-MAST sequence types.Conclusions: Reduced susceptibility of N. gonorrhoeae to ceftriaxone and cefixime was associated with diverse penA mutations, particularly PBP 2 pattern XIII containing an Ala-501-->Val substitution, together with mtrR and porB mutations. The existence of only one strain having the mosaic penA sequence indicated that ceftriaxone and cefixime resistance in Korea is mostly not associated with a mosaic penA sequence. Highly heterogeneous NG-MAST sequence types excluded the clonal expansion of a particular subtype. [ABSTRACT FROM AUTHOR]

Mupirocin has been used against Gram-positive pathogenic bacteria, and is a specific inhibitor of bacterial isoleucyl-tRNA synthetase. In this work, we have determined the prevalence of mupirocin resistance among staphylococci isolated from a Korean hospital, and have investigated the characteristics of the resistance. In Staphylococcus aureus, the prevalence of high-level mupirocin resistance was 5% (16 of 319), whereas low-level mupirocin resistance was not detected. In coagulase-negative staphylococci (CoNS) the rates of high- and low-level mupirocin resistance were 16.7% (34 of 204) and 10.3% (21 of 204), respectively. The high-level resistant strains contained the ileS-2 gene, which encodes a novel staphylococcal isoleucyl-tRNA synthetase. In contrast, all of the low-level mupirocin-resistant CoNS contained the mutation V588F, which is located near the conserved motif KMSKS, within the chromosomal staphylococcal isoleucyl-tRNA synthetase gene (ileS). In conclusion, this work describes the recent, but rapid, emergence of two different types of mupirocin-resistant staphylococci in Korea, and the sequence and mutant characterization of the isoleucyl-tRNA synthetase of CoNS. [ABSTRACT FROM AUTHOR]