Bacteremia due to extended-spectrum-β-lactamase-producing Aeromonas spp. at a medical center in Southern Taiwan.

Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan.
Antimicrobial Agents and Chemotherapy (Impact Factor: 4.57). 10/2011; 55(12):5813-8. DOI: 10.1128/AAC.00634-11
Source: PubMed

ABSTRACT Although extended-spectrum-β-lactamase (ESBL)-producing aeromonads have been increasingly reported in recent years, most of them were isolates from case reports or environmental isolates. To investigate the prevalence of ESBL producers among Aeromonas blood isolates and the genes encoding ESBLs, consecutive nonduplicate Aeromonas blood isolates collected at a medical center in southern Taiwan from March 2004 to December 2008 were studied. The ESBL phenotypes were examined by clavulanate combination disk test and the cefepime-clavulanate ESBL Etest. The presence of ESBL-encoding genes, including bla(TEM), bla(PER), bla(CTX-M), and bla(SHV) genes, was evaluated by PCR and sequence analysis. The results showed that 4 (2.6%) of 156 Aeromonas blood isolates, 1 Aeromonas hydrophila isolate and 3 Aeromonas caviae isolates, expressed an ESBL-producing phenotype. The ESBL gene in two A. caviae isolates was bla(PER-3), which was located in both chromosomes and plasmids, as demonstrated by Southern hybridization. Of four patients with ESBL-producing Aeromonas bacteremia, two presented with catheter-related phlebitis and the other two with primary bacteremia. Three patients had been treated with initial noncarbapenem β-lactams for 5 to 10 days, and all survived. In conclusion, ESBL producers exist among Aeromonas blood isolates, and clinical suspicion of ESBL production should be raised in treating infections due to cefotaxime-resistant Aeromonas isolates.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Aeromonas dhakensis, often phenotypically identified as A. hydrophila, is an important human pathogen. The present study aimed to compare the clinical and biological features of A. dhakensis and A. hydrophila isolates from human wounds. A total of 80 of Aeromonas wound isolates collected between January 2004 and April 2011 were analyzed. The species was identified by the DNA sequence matching of rpoD and gyrB (or rpoB if necessary). Most of the Aeromonas isolates were identified as A. dhakensis (37, 46.3%), and 13 (16.3%) as A. hydrophila. Both these two species alone can cause severe skin and soft-tissue infections. More A. dhakensis isolates were found in wounds exposed to environmental water (32.4% vs. 0%, P=0.042). More biofilm formation was noted among A. dhakensis isolates (mean OD570 , 1.23±0.09 vs. 0.78±0.21, P=0.03). The minimal inhibitory concentrations of ceftriaxone, imipenem, and gentamicin for A. dhakensis isolates were higher (P values <0.0001, 0.04, and 0.01, respectively). The survival rates of Caenorhabditis elegans co-incubated by A. dhakensis from day 1 to day 3 were lower than those of worms infected with A. hydrophila in liquid toxicity assays (all P values <0.01). A. dhakensis isolates exhibited more cytotoxicity, as measured by the released leukocyte lactate dehydrogenase levels in human normal skin fibroblast cell lines (29.6±1.2% vs. 20.6±0.6%, P<0.0001). The cytotoxin gene ast was primarily present in A. hydrophila isolates (100% vs. 2.7%, P<0.0001). In summary, A. dhakensis is the predominant species among Aeromonas wound isolates, and more virulent than A. hydrophila. This article is protected by copyright. All rights reserved.
    Clinical Microbiology and Infection 11/2013; · 4.58 Impact Factor
  • Source
    Infection, genetics and evolution: journal of molecular epidemiology and evolutionary genetics in infectious diseases 04/2014; · 3.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Aeromonas dhakensis, a recently described Aeromonas sp. formerly called Aeromonas aquariorum, is associated with human infections. In this study, a chromosomal gene, blaAQU-1, was identified in A. dhakensis AAK1 that constitutes a 1143-bp open reading frame and is 87% identical to the gene encoding CepH in Aeromonas hydrophila. An Escherichia coli TOP10 cell transformant harbouring blaAQU-1 was resistant to cefotaxime but not to cefepime. mRNA expression of blaAQU-1 in the cefotaxime-resistant mutant strain AAK1m was 70-fold higher than in the wild strain AAK1. In all 16 A. dhakensis isolates (the major species of 51 consecutive Aeromonas blood isolates collected from June 1999 to June 2001) as well as in A. aquariorum MDC47(T) and A. hydrophila subsp. dhakensis LMG 19562(T), but not in the reference strains or clinical isolates of other A. hydrophila subspecies, Aeromonas caviae, Aeromonas veronii or Aeromonas enteropelogenes, blaAQU-1-related genes were detected by PCR. Overall, 13 (81%) of the 16 A. dhakensis blood isolates exhibited either cefotaxime resistance or the in vitro emergence of derepressed cefotaxime-resistant mutants. In vivo selection of an A. dhakensis resistant mutant was noted in a burn patient undergoing cefotaxime monotherapy. These observations suggest that AQU-1 is a chromosomal cephalosporinase in A. dhakensis. Cefotaxime monotherapy for severe A. dhakensis infections should be used cautiously.
    International journal of antimicrobial agents 09/2013; · 3.03 Impact Factor

Full-text (2 Sources)

Available from
May 21, 2014