Development Of Quinolone Resistance Research Articles

Dissemination of Quinolone-Resistant Escherichia coli in the Norwegian Broiler and Pig Production Chains and Possible Persistence in the Broiler Production Environment.

In Norway, the use of quinolones in livestock populations is very low, and prophylactic use is prohibited. Despite this, quinolone-resistant Escherichia coli (QREC) isolates are present at low levels in several animal species. The source of these QREC isolates is unknown. The aim of this study was to characterize and compare QREC isolates from different animal species to identify putative factors that may promote the occurrence of QREC. A total of 280 QREC isolates, from broilers, pigs, red foxes, and wild birds, were whole-genome sequenced and analyzed. Well-known chromosomal and plasmid-mediated resistance mechanisms were identified. In addition, mutations in marR, marA, and rpoB causing novel amino acid substitutions in their respective proteins were detected. Phylogenetic analyses were used to determine the relationships between the isolates. Quinolone resistance mechanism patterns appeared to follow sequence type groups. Similar QREC isolates with similar resistance mechanism patterns were detected from the samples, and further phylogenetic analysis indicated close evolutionary relationships between specific isolates from different sources. This suggests the dissemination of highly similar QREC isolates between animal species and also the persistence of QREC strains within the broiler production chain. This highlights the importance of both control measures at the top of the production chain as well as biosecurity measures to avoid the further dissemination and persistence of QREC in these environments.IMPORTANCE Since antimicrobial usage is low in Norwegian animal husbandry, Norway is an ideal country to study antimicrobial resistance in the absence of selective pressure from antimicrobial usage. In particular, the usage of quinolones is very low, which makes it possible to investigate the spread and development of quinolone resistance in natural environments. Comparison of quinolone-resistant E. coli (QREC) isolates from livestock and wild animals in light of this low quinolone usage provides new insights into the development and dissemination of QREC in both natural and production environments. With this information, preventive measures may be taken to prevent further dissemination within Norwegian livestock and between other animals, thus maintaining the favorable situation in Norway.

Development of quinolone resistance and prevalence of different virulence genes among Shigella flexneri and Shigella dysenteriae in environmental water samples.

The purpose of this study was to find out the mechanism of quinolone resistance in Shigella sp. isolated from environmental water samples from various parts of Kolkata, India. Out of 196 Shigella sp. isolated from 2014 to 2017, we selected 32 Shigella isolates for antimicrobial susceptibility tests. The minimum inhibitory concentrations (MIC) for quinolones ranged from 30 to 50μgml-1 for ofloxacin, 5-20μgml-1 for ciprofloxacin and 20-30μgml-1 for norfloxacin. A few amino acid changes were found in quinolone resistance determining region (QRDR) of gyrA. Mutations in gyrA lead to a higher increment of MIC of quinolones. Among the plasmid-mediated (PMQR) quinolone resistance genes investigated, qnrB and aac(6')-lb-cr genes were found in all isolates. qnrA and qnrS were found in 25% and 62% of the isolates, respectively. ipaH gene was found in all of the isolates followed by the presence of other virulence genes ial, sen and stx1. Almost all the isolates having high MICs showed efflux pump activity in drug accumulation assay. All the mechanisms may or may not be present in a single strain. Several types of efflux pumps, presence of PMQR genes and mutations in drug target site of QRDR region may play the crucial role for resistance in our isolates.

Contribution of QnrA, a Plasmid-Mediated Quinolone Resistance Peptide, to Survival of <i>Escherichia coli</i> Exposed to a Lethal Ciprofloxacin Concentration

We evaluated the effects of qnrA on survival of bacteria exposed to a lethal ciprofloxacin (CIP) concentration and development of quinolone resistance through the accumulation of amino acid substitutions in quinolone resistance-determining regions (QRDRs) of GyrA and ParC, targets of quinolones, in Escherichia coli. CIP-susceptible E. coli strains of different O-serotypes (O1, O6, O18, O25b, O74, and O78) were transformed by a recombinant plasmid harboring qnrA, and the parent strains and their transformants were subjected to killing curve assays and adaptation tests. In the killing curve assay at 2 × the minimum inhibitory concentration of CIP, the viable bacterial cell numbers of strains O1, O6, and O25b were maintained at 10(5)-10(8) CFU/mL after 24-h incubation, while the remaining strains showed a 10(5)-fold reduction in viable cell numbers. In the adaptation test, a Ser83-Leu substitution in the QRDR of GyrA was identified earlier in the parent strains of O25b and O1 than in their transformants, suggesting that the acquisition of qnrA did not necessarily accelerate the rate of accumulation of amino acid substitutions in the QRDR. We confirmed that the presence of qnrA contributed to increased survival of the E. coli strains displaying certain O-serotypes. Further studies are necessary to evaluate the precise effects of qnrA on quinolone resistance acquisition by Enterobacteriaceae.

High levels of multiresistance in quinolone resistant urinary tract isolates of Escherichia coli from Norway; a non clonal phenomen?

BackgroundThe problem of emerging ciprofloxacin resistance is compounded by its frequent association with multiresistance, the reason for which is not fully understood. In this study we compare multiresistance, clonal similarities and phylogenetic group in urinary tract isolates of Escherichia coli sensitive and resistant to the quinolone antimicrobials nalidixic acid and ciprofloxacin.ResultsQuinolone resistant isolates were more resistant to non-quinolone antibiotics than sensitive isolates, with resistance to ampicillin, mecillinam, sulphonamide, trimethoprim, tetracycline, kanamycin and chloramphenicol significantly increased. Fifty-one percent of quinolone-resistant isolates were multiresistant. Although multiresistance was most prevalent (63%) in isolates showing high-level ciprofloxacin resistance, it was still highly prevalent (41%) in nalidixic acid resistant isolates with low-level ciprofloxacin resistance. Multiresistance was more frequent among singleton isolates (61%) than clonal isolates (40%) of quinolone resistant Escherichia coli. Ciprofloxacin resistance was associated with certain specific clones, among them the globally distributed clonal Group A. However, there was no significant difference in the overall degree of clonality between quinolone sensitive and resistant isolates. Ciprofloxacin resistance was positively associated with phylogroup D and negatively associated with phylogroup B2. This correlation was not associated with clonal isolates.ConclusionThis study supports earlier findings of association between ciprofloxacin resistance and resistance to other antibiotics. The prevalence of multiresistance in quinolone-resistant isolates that have not yet developed high-level ciprofloxacin resistance suggest that multiresistance arises early in the development of quinolone resistance. This is consistent with exposure to quinolones causing quinolone resistance by mutations and mobilization of multiresistance elements by induction of the SOS response. The spread of clones seems to be less important than previously reported in regard to emergence of quinolone resistance and multiresistance as both are associated primarily with singleton isolates.

Prevalence and characterization of quinolone resistance in Laribacter hongkongensis from grass carp and Chinese tiger frog

Laribacter hongkongensis is a food-borne bacterium associated with community-acquired gastroenteritis and diarrhoea. Quinolone resistance was recently reported in bacterial isolates from aquatic products, but the molecular mechanisms for resistance were still unknown. In this study, a total of 157 L. hongkongensis strains were isolated from grass carps (n = 443) and Chinese tiger frogs (n = 171). Twenty-one ciprofloxacin-resistant strains were analysed for mutations in quinolone resistance-determining regions (QRDR), acquired quinolone resistance (AQR) genes and the role of efflux pumps in resistance. All QRDR mutations in gyrA (codons 85 and 89) and parC (codons 83 and 231) were found to be closely associated with ciprofloxacin resistance. The AQR gene aac(6')-Ib-cr was found in 42.9% (9/21) of the resistant strains, but qnrA, qnrB, qnrC, qnrD, qnrS and qepA were not detected. No significant change of MICs to ciprofloxacin was observed in the presence of an efflux pump inhibitor, indicating the role of efflux pump was probably absent. All 21 ciprofloxacin-resistant strains showed different electrophoretic patterns, which suggested they were not genetically related. These data highlight the importance of QRDR mutations and the AQR gene aac(6')-Ib-cr during the development of quinolone resistance in a heterogeneous population of L. hongkongensis.

Role of Efflux pumps in the development of quinolone-resistance in Peruvian Escherichia coli isolates

Role of Efflux pumps in the development of quinolone-resistance in Peruvian Escherichia coli isolates

Effect of GrlA mutation on the development of quinolone resistance in Staphylococcus aureus in an in vitro pharmacokinetic model

To investigate the effect of GrlA mutation on the development of quinolone resistance in Staphylococcus aureus in an in vitro pharmacokinetic (PK) model and to examine the relationship between the emergence of resistance and PK/pharmacodynamic parameters. A wild-type and a GrlA mutant of S. aureus were exposed to the Japanese clinical dose of ciprofloxacin in an in vitro PK model, and the development of resistance was measured by population analysis. In addition, several doses of four quinolones (pazufloxacin, ciprofloxacin, levofloxacin and tosufloxacin) were tested against the GrlA mutant. All model simulations were single-dose design and were conducted over 24 h. Four quinolones were tested against the GrlA mutant, and a resistant population emerged after treatment with 250 mg pazufloxacin intravenous drip infusion, 600 mg ciprofloxacin intravenous drip infusion, 200 mg levofloxacin oral dosing and 150 mg tosufloxacin oral dosing. The emergence of a resistant population was not induced by treatment with 500 mg pazufloxacin intravenous drip infusion, 2,400 mg ciprofloxacin intravenous drip infusion, 400 mg levofloxacin oral dosing and 600 mg tosufloxacin oral dosing. Treatment with the clinical dose of ciprofloxacin induced the development of resistance in the GrlA mutant, but not in the wild-type strain. These data suggest that the frequency of acquisition of additional mutations differs between the wild-type and the GrlA mutant of S. aureus. Also, GrlA mutation predisposes S. aureus to develop high-level quinolone resistance.

Antibacterial prophylaxis in neutropenic patients

Antibiotic prophylaxis has been used for several decades to prevent infection in chemotherapy-induced neutropenia and its benefits have been debated just as long. Recent analysis suggests that quinolones may actually be life saving in high-risk groups such as acute leukaemia and autologous bone marrow transplant but these benefits are likely to be negated in the long term by the development of quinolone resistance.

Comment on: Quinolone resistance determinant qnrA3 in clinical isolates of Salmonella in 2000-2005 in Hong Kong

Sir, In their recent correspondence, Chu et al. noted the first observation of qnrA3 in salmonellae in Hong Kong, underlining the spread and diversity of plasmidic quinoloneresistance determinants worldwide. Such determinants now include qnrA1–5, qnrB and qnrS, some of which, at least, protect DNA gyrase, as well as the fluoroquinolone-acetylating variant of the aminoglycoside-modifying enzyme AAC(60)Ib, named AAC(60)Ib-cr. These proteins may influence the development of high-level resistance to at least some fluoroquinolones. In our recent article, we sought to explore the unexplained significant association between chromosomal fluoroquinolone resistance and plasmidic resistances to other antibiotic classes (such as ESBLs), which is seen in several bacterial genera. We were pleased to note that Chu et al. cited our article, but would like to clarify a misinterpretation of our hypothesis. Multiresistance plasmids can encode toxin–antitoxin systems to prevent their own loss from the cell, and some toxins target DNA gyrase. We asked whether the development of quinolone resistance by plasmid-bearing strains might be associated with such DNA gyrase-targeting toxins. We speculated on whether a cell might escape addiction to toxin–antitoxin systems by developing resistance to the toxin. Mutational events in DNA gyrase could play a role in cells escaping addiction to plasmids with gyrase-targeting toxins, and we suggested that these mutations might fortuitously confer a degree of cross-resistance to quinolones. Notably, whilst at least three qnrA variants likely originated from the chromosome of Shewanella algae, and although Qnr-type proteins inhibit/protect DNA gyrase, their precise cellular role(s) remains unknown. We would like to emphasize that we did not state, or wish to imply, that Qnr proteins could be part of a toxin–antitoxin pair as was attributed to our article by Chu et al. Rather, we postulated that gyrase ‘inhibitors/protectors’ such as Qnr might give some crossresistance to gyrase-targeting toxins in addition to the more obvious resistance to quinolones. By so doing these proteins might open a ‘window’ and influence the frequency at which cells could eject the toxin–antitoxin encoding replicons without suffering apoptosis, thereby providing the host organism with a toxin–antitoxin evasion mechanism. This might provide a competitive advantage in demanding psychrophilic aquatic environments, the natural environment of S. algae, by allowing enhanced ejection of ‘accessory’ replicons.

In vitro development of resistance to DX-619 and other quinolones in enterococci

To investigate the molecular events involved in the development of quinolone resistance in enterococci. Clinical isolates of Enterococcus faecium and Enterococcus faecalis were exposed to inhibitory and subinhibitory concentrations of DX-619, ciprofloxacin, levofloxacin, gatifloxacin and moxifloxacin. Mutational frequencies were calculated and susceptibility changes were determined. The quinolone resistance determining regions (QRDRs) of gyrA and parC in less-susceptible mutants were amplified by PCR and sequenced. Single-step mutants of E. faecalis and E. faecium were selected with all drugs. There were no differences in the frequencies of mutant selection among drugs, with frequencies ranging from 10(-5) to 10(-8). All single-step mutants were inhibited by 0.03-1 mg/L DX-619, 0.25-8 mg/L moxifloxacin, 0.5-8 mg/L gatifloxacin, 1-16 mg/L levofloxacin and 1-32 mg/L ciprofloxacin. No QRDR changes were observed in single-step mutants. Less-susceptible mutants selected after five passages on agar containing subinhibitory quinolone concentrations were inhibited by 0.12-8 mg/L DX-619, 1-64 mg/L moxifloxacin, 2-64 mg/L gatifloxacin and 2-128 mg/L levofloxacin and ciprofloxacin. QRDR changes were detected in only 9 of the 20 fifth-passage mutants, suggesting that mutations outside the purported QRDRs and/or other resistance mechanisms were also involved. The relatively high frequencies at which single-step mutants were selected with all drugs indicate that caution is necessary if quinolones are to be considered for monotherapy of serious enterococcal infections. DX-619, the most potent quinolone, may have potential as an anti-enterococcal agent if sufficient concentrations can be safely attained in vivo.

In vitro selected fluoroquinolone-resistant mutants of Citrobacter freundii: analysis of the quinolone resistance acquisition

Ten quinolone-resistant mutants of Citrobacter freundii, which were selected in vitro with fluoroquinolones from two clinical isolates, were studied. The parent isolates were susceptible to quinolones in spite of showing a single substitution in the GyrB (His-417 --> Leu). No change was observed in the outer membrane proteins or in the lipopolysaccharide in any of the ten mutants studied with respect to their parent isolates. The development of quinolone resistance in selected mutants was associated with the appearance of a substitution in the GyrA (Thr-83 --> Ile) in nine of the ten mutants plus enhanced active efflux in all of them.

Uncomplicate the Treatment of Uncomplicated Urinary Tract Infections-Reply

The concerns expressed by Ditmanson and Apgar regarding the use of ciprofloxacin as a short-course, low-dose treatment for uncomplicated urinary tract infections in otherwise healthy women are well expressed and not unexpected. Nevertheless, their generalizations about the problem of antimicrobial resistance should be dispelled by examination of available data. Certain microorganisms such as S aureus<i>and</i>P aeruginosa<i>have been associated with development of quinolone resistance in the United States, usually in the hospital setting. However, there has been no significant development of resistance to the fluoroquinolones among the Enterobacteriaceae.1 The issue of "inappropriate use" and, in particular, the anecdotal cases of treatment failures associated with</i>S pneumoniae<i>are not related to development of drug resistance. In fact, while the increasing resistance of</i>S pneumoniae to penicillin is of great concern, there has been no change in the susceptibility of this organism to the quinolones, despite the significant use

Development of quinolone resistance and multiple antibiotic resistance in Salmonella bovismorbificans in a pancreatic abscess

Development of quinolone resistance and multiple antibiotic resistance in <i>Salmonella bovismorbificans</i> in a pancreatic abscess