RESUMEN
Carbapenemase-producing Gram-negative bacteria have been increasingly reported. Simple and sensitive methods for carbapenemase detection are still needed. In this study, a gold nanoparticle (AuNP) solution was modified by the addition of zinc sulfate (ZnSO4) for improving the conventional GoldNano Carb (cGoldC) test, and the modified GoldC (mGoldC) test was then evaluated for phenotypic detection of carbapenemase production in Gram-negative bacilli clinical isolates. ZnSO4 was added to give final concentrations of 0.25, 0.5, 0.75, and 1 mM. The performance of the mGoldC test was evaluated in Enterobacterales, Acinetobacter spp., and Pseudomonas aeruginosa isolates from six hospitals in different regions using polymerase chain reaction (PCR) as a gold standard. The AuNP solution with 0.25 mM ZnSO4 was used for the mGoldC test. Evaluation of the mGoldC test in 495 Enterobacterales, 212 Acinetobacter spp., and 125 P. aeruginosa isolates (including 444 carbapenemase producers and 388 non-carbapenemase producers) revealed sensitivity, specificity, a positive likelihood ratio, and a negative likelihood ratio of 98.6%, 98.2%, 54.7, and 0.01, respectively. This test is fast, easy to perform, cost-effective (~0.25 USD per test), and highly sensitive and specific for routine carbapenemase detection, thus leading to effective antimicrobial therapy and infection control measures.
RESUMEN
A total of 121 Escherichia coli (47 extended-spectrum ß-lactamase [ESBL] and 74 non-ESBL producers) and 75 Klebsiella pneumoniae isolates (49 ESBL and 26 non-ESBL producers) were collected from urine samples between October 2010 and April 2011 at a university hospital and assessed for the presence of plasmid-mediated quinolone resistance (PMQR) genes. Twenty-seven E. coli (22.3%) and 49 K. pneumoniae (65.3%) isolates harbored PMQR genes, which mostly consisted of aac(6')-Ib-cr and qnrS, followed by qnrB and qnrA. Among the 76 PMQR-positive isolates, 15 (19.7%) and 2 (2.6%) carried 2 and 3 different PMQR genes, respectively. However, qnrC, qnrD, and qepA were not found in any isolate. The PMQR genes were more prevalent in ESBL producers than in non-ESBL producers (42.6% versus 9.5% in E. coli and 81.6% versus 34.6% in K. pneumoniae). Approximately 35%-60% of the PMQR-positive isolates were susceptible or intermediately susceptible to fluoroquinolones. The enterobacterial repetitive intergenic consensus-PCR method revealed that most PMQR-positive isolates belonged to different strains, indicating the spread of these resistance determinants. PMQR gene transfer by conjugation was successful in 10%-25% of the test donors. This study showed a high prevalence of PMQR genes among both organisms. Clinical use of fluoroquinolones for the treatment of infections caused by fluoroquinolone-susceptible strains harboring PMQR genes may lead to decreased therapeutic efficacy.