A total of 1623 clinical isolates of Salmonella belonging to 229 serotypes were received by the Senegalese Reference Center for Enterobacteria from January 1999 to December 2009. The most common ...serotypes were Enteritidis (19% of the isolates), Typhi (8%), Typhimurium (7%) and Kentucky (4%). A significant increase in the prevalence of resistance to amoxicillin (0.9% in 1999 to 11.1% in 2009) and nalidixic acid (0.9% in 1999 to 26.7% in 2009) was observed in non-typhoidal Salmonella serotypes. For critically important antibiotics, notably ciprofloxacin and extended-spectrum cephalosporins (ESCs), the rates of resistance were low: 0.3% and 0.5%, respectively. Seven ESC-resistant Salmonella strains and three additional ESC-resistant strains from Senegal (1990) and Mali (2007) were studied to identify the genetic basis of their antibiotic resistance. All ESC-resistant strains produced an extended-spectrum β-lactamase (ESBL). These were CTX-M-15 (n = 6; 2000–2008), SHV-12 (n = 3; 2000–2001) and SHV-2 (n = 1; 1990). A large IncHI2 ST1 pK29-like plasmid was found in six strains (three producing SHV-12 and three CTX-M-15), whereas IncN and IncF plasmids were found in three strains and one strain, respectively. The association of plasmid-mediated quinolone resistance (PMQR) genes qnrB1 and aac(6′)-Ib-cr was found in four ESBL-producing strains, leading to decreased susceptibility and even full resistance to ciprofloxacin (MIC range 0.75–2 mg/L) despite the absence of mutations in the quinolone resistance-determining region (QRDR) of gyrA, gyrB, parC and parE. This association of ESBL and multiple PMQR mechanisms within the same strains is therefore a serious concern as it hampers the use of both ESCs and fluoroquinolones for severe Salmonella infections.
Abstract After two decades of the discovery of plasmid-mediated quinolone resistance (PMQR), three different mechanisms have been associated to this phenomenon: target protection (Qnr proteins, ...including several families with multiple alleles), active efflux pumps (mainly QepA and OqxAB pumps) and drug modification AAC(6′)-Ib-cr acetyltransferase. PMQR genes are usually associated with mobile or transposable elements on plasmids, and, in the case of qnr genes, are often incorporated into sul1 -type integrons. PMQR has been found in clinical and environmental isolates around the world and appears to be spreading. Although the three PMQR mechanisms alone cause only low-level resistance to quinolones, they can complement other mechanisms of chromosomal resistance to reach clinical resistance level and facilitate the selection of higher-level resistance, raising a threat to the treatment of infections by microorganisms that host these mechanisms.
We investigated the prevalence of extended-spectrum β-lactamases (ESBLs) in Enterobacter spp. bloodstream isolates from 19 hospital laboratories in Norway during 2011. A total of 62/230 (27%) ...isolates were resistant to third-generation cephalosporins and four (1.7%) were ESBL-positive; blaCTX-M-15 (n = 3) and blaSHV-12 (n = 1). This is comparable to the prevalence of ESBLs in clinical isolates of Escherichia coli and Klebsiella pneumoniae in Norway during the same period. All ESBL-positive isolates were multidrug resistant (MDR) and harboured plasmid-mediated quinolone resistance. Three isolates supported transfer of large IncHI2-plasmids harbouring ESBL- and MDR-encoding genes to E. coli recipients by in vitro conjugation.
Quinolones are among the most effective antibiotics against
spp. Several chromosomal and/or plasmid-mediated quinolone-resistance mechanisms have been found in
. Plasmid-mediated ...quinolone-resistance (PMQR) is mediated by quinolone-resistance (QNR) proteins, modifying enzymes or efflux pumps. Only a few previous studies examined the prevalence of quinolone-resistance in the Kingdom of Saudi Arabia (KSA) and showed it is increasing. Mechanisms of quinolone-resistance among
spp. in the KSA; examined herein; have not been extensively studied.
Ninety-two
isolates were collected and their resistance to seven different types of quinolones was determined by the microbroth dilution method. PMQR mechanisms were examined using a PCR screen to identify six PMQR genes including
,
,
,
, and
. Clonal relatedness of the quinolone-resistant isolates was determined by ERIC-PCR.
Of the isolates, 42.4% (39/92) were resistant to 1-7 of the tested quinolones. Gemifloxacin resistance was the lowest (28.3%) while resistance to the other six quinolones were ≥ 35%. The most common biotype among the 39 quinolone-resistant isolates was resistance to the seven tested quinolones (26/39; 66.7%).
,
, and
were found in 31 (79.5%), 31 (79.5%) and 28 (71.8%) of the 39 isolates, respectively, and all three genes together were found in 22 of the 39 isolates (56.4%).
, and
were not detected in any of the isolates and two isolates did not harbor any of the six tested genes. The isolates showed 38 different ERIC profiles and only two isolates (Pa16 and Pa17) had an identical profile.
This is the first description of PMQR mechanisms among clinical
isolates from the KSA, which appears to be mainly mediated by
,
, and
.
Wastewater treatment plants (WWTPs) harbor bacteria and antimicrobial resistance genes, favoring gene exchange events and resistance dissemination. Here, a culture-based and metagenomic survey of ...qnrA, qnrB, qnrS, and aac(6′)-Ib genes from raw sewage (RS) and activated sludge (AS) of a full-scale municipal WWTP was performed. A total of 96 bacterial isolates were recovered from nalidixic acid-enrichment cultures. Bacteria harboring the aac(6′)-Ib gene predominated in RS, whereas qnrS-positive isolates were specific to AS. Novel qnrS- and aac(6′)-Ib-cr positive species were identified: Morganella morganii, Providencia rettgeri, and Pseudomonas guangdongensis (qnrS), and Alcaligenes faecalis and P. rettgeri (aac(6′)-Ib-cr). Analysis of qnrS and aac(6′)-Ib sequences from isolates and clone libraries suggested that the diversity of qnrS is wider than that of aac(6′)-Ib. A large number of amino acid mutations were observed in the QnrS and AAC(6′)-Ib proteins at previously undetected positions, whose structural implications are not clear. An accumulation of mutations at the C72, Q73, L74, A75 and M76 positions of QnrS, and D181 of AAC(6′)-Ib might be important for resistance. These findings add significant information on bacteria harboring qnrS and aac(6′)-Ib genes, and the presence of novel mutations that may eventually emerge in clinical isolates.
•Bacteria harboring the aac(6′)-Ib gene predominated in raw sewage.•qnrS-positive bacteria were specific to activated sludge.•First report of the qnrS gene in Providencia rettgeri and Pseudomonas guangdongensis.•aac(6′)-Ib-cr: first report in Alcaligenes faecalis and Providencia rettgeri.•QnrS and AAC(6′)Ib exhibited many amino acids alterations previously undetected.
Lindemann PC, Risberg K, Wiker HG, Mylvaganam H. Aminoglycoside resistance in clinical Escherichia coli and Klebsiella pneumoniae isolates from Western Norway. APMIS 2012; 120: 495–502.
Resistance to ...gentamicin in Escherichia coli from blood culture has shown an increase over the past decade in Norway. This study was done to investigate aminoglycoside resistance in Escherichia coli and Klebsiella pneumoniae in Western Norway. The material included 49 blood culture isolates which had shown aminoglycoside resistance collected during 2000–2009. To investigate co‐resistance to alternative antibiotics and dynamics involved in aminoglycoside resistance 67 isolates (mostly from urine) exhibiting resistance to both aminoglycosides and extended spectrum beta‐lactam antibiotics were also included. MIC values were obtained for amikacin, gentamicin, kanamycin, netilmicin, streptomycin and tobramycin and all isolates were screened using PCR for aac(3)‐II and aac(6′)‐Ib, encoding aminoglycoside modifying enzymes. Resistance to ≥3 aminoglycosides was found in 92% of the isolates and 60.3% showed resistance to gentamicin, netilmicin, tobramycin and kanamycin. Amikacin resistance was low. Co‐resistance to ciprofloxacin was found in 88% of the isolates with gentamicin resistance. aac(3)‐IIa/c was found in 79.3% and aac(6′)‐Ib in 37.9% of the isolates and 28.4% harboured both genes. aac(6′)‐Ib‐cr, possibly contributing to ciprofloxacin resistance was found mostly in extended spectrum beta‐lactamase producers. The aminoglycoside resistance patterns indicate co‐existence of multiple resistance mechanisms. The use of ciprofloxacin and third generation cephalosporins is likely to have contributed to the increase in aminoglycoside resistance in Norway.
The aac(6′)-Ib gene is the most widespread gene encoding aminoglycoside-modifying enzyme and conferring resistance to tobramycin, streptomycin and kanamycin. The variant aac(6′)-Ib-cr gene confers ...resistance to both aminoglycosides and fluoroquinolones (FQ). A total of 132 Campylobacter isolates, including 91 C. jejuni and 41 C. coli, were selected from broiler hens isolates. The aac(6′)-Ib gene was amplified using PCR and was subsequently digested with the BtsCI restriction enzyme to identify aac(6′)-Ib-cr. Among these isolates, 31 out of 41 C. coli (75.6%) and 1 (0.98%) C. jejuni were positive for the aac(6′)-Ib gene, which was identified as the aac(6′)-Ib-cr variant in 10 (32.25%) C. coli isolates. This variant was correlated with mutations in gyrA (Thr-86-Ile), as well as resistance to FQs. This study is the first report in Tunisia on Campylobacter coli strains harboring both the aac(6′)-Ib and aac(6′)-Ib-cr variants. These genes were present in Campylobacter isolates exhibiting resistance to multiple antibiotics, which restricts the range of available treatments.
Although resistance to quinolones is commonly chromosomally-encoded in Enterobacteriaceae, the emergence of plasmid-mediated quinolone resistance (PMQR) has also been reported, with at least three ...known resistance mechanisms to date, i.e., Qnr, aminoglycoside acetyltransferase AAC(6′)-Ib-cr and QepA. Qnr proteins protect target enzymes (DNA gyrase and type IV topoisomerase) from quinolone inhibition, the AAC(6′)-Ib-cr enzyme acetylates norfloxacin and ciprofloxacin, and the QepA efflux pump extrudes hydrophilic fluoroquinolones. Although these PMQR determinants confer only low-level resistance to quinolones and/or fluoroquinolones, they may provide a favourable background in which the selection of additional chromosomally-encoded quinolone resistance mechanisms can occur.
We investigated the phenotypic and molecular characteristics of Extended-Spectrum-β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae clinical isolates from four health-care ...institutions in Hermosillo, Sonora, Mexico. ESBL-producing isolates were collected from February to August 2016. The prevalence of ESBL-producing E. coli and K. pneumoniae was 11.9 and 8.7%, respectively. High dissemination of resistance to ciprofloxacin (88%), trimethoprim/sulfamethoxazole (72%) and aminoglycosides (59%) were detected, as well as susceptibility to meropenem, amikacin and tigecycline. The ESBL found variants were CTX-M-1 (88%) and CTX-M-9 (5%). The plasmid-mediated quinolone resistance (PMQR) gene aac(6´)-Ib-cr was identified in 62% of a representative sample, whereas the qnrB and qnrS genes were detected in 49% of the isolates. PFGE analyses detected many unrelated clones among the hospital or community isolates. A constant programme of epidemiological surveillance is recommended to understand the dynamics of bacterial resistance to both cephalosporin as well as the fluoroquinolone family of antibiotics.
The plasmid-mediated quinolone resistance (PMQR) genes have changed the resistance pattern to quinolones, especially among Enterobacteriales. The dissemination of these genes in Latin American ...countries, where the prescription of fluoroquinolones is high, has been described in several studies; however, no review of the impact of PMQR in this continent has been conducted. This review summarized current knowledge about the circulation of PMQR among Enterobacteriales in Latin American. After the search and selection, 61 articles were included in the study. Most of studies reported PMQR genes among Enterobacteriales from human (47/61, 77%) and animal (18/61, 29.5%) samples, recovered mainly in Brazil (23/61, 37.7%), Mexico (11/61, 18%), and Uruguay (7/61, 11.5%). Nine different PMQR genes (
qnrA, qnrB, qnrS, qnrD, qnrE, aac
-
(6′)
-
Ib
-
cr, oqxA
,
oqxB,
and
qepA
) were found in Latin America, with
aac (6′)
-
Ib
-
cr
(37/61, 60.6%) and
qnrB
(26/61, 42.6%) being the most frequently reported.
Escherichia coli
(40/61, 65.6%) was the species most frequently reported to carry a PMQR gene, followed by
Klebsiella pneumoniae
(24/61, 39.3%),
Enterobacter cloacae
(15/61, 24.6%), and
Salmonella
spp. (14/61, 22.9%). Thus, this review provides important information which might help in designing measures to control the spread of quinolone resistance determinants on this continent.
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