Trend of plasmid-mediated quinolone resistance genes at the Children's Hospital in Tunisia

Resistance to aminoglycoside and quinolone drugs among Klebsiella pneumoniae clinical isolates from northern Jordan

This study aimed to identify phenotypic and genotypic aminoglycoside and quinolone non-susceptibility and the prevalence of aminoglycoside-modifying enzymes and plasmid-mediated quinolone resistance genes among K. pneumoniae clinical isolates from northern Jordan. K. pneumoniae isolates (n = 183) were tested for antimicrobial susceptibility using the Kirby-Bauer disk diffusion method. The double-disk synergy test was used for the detection of the extended-spectrum beta-lactamase phenotype. Polymerase chain reaction was used to detect genes encoding aminoglycoside-modifying enzyme (aac (3')-II, aac (6')-II, aac (6')-Ib, ant (3″)-I, aph (3')-VI, armA, and rmtB), and plasmid-mediated quinolone resistance (qnrA, qnrB, qnrC, qnrD, qnrS, acc(6')-Ib-cr, qepA, and oqxAB) genes. Multi-locus sequence typing was used to elucidate the genetic diversity of selected isolates. The non-susceptibility percentages to aminoglycosides and quinolones were 65.0 % and 61.7 %, respectively. The most frequent aminoglycoside-modifying enzyme gene was ant (3″)-I at 73.8 %, followed by aac (6')-Ib at 25.1 %, aac (3')-II at 17.5 %, aph (3')-VI at 12.0 %, armA at 9.8 %, and rmtB at 0.5 %. Aac (6')-II was not detected among the isolates. The most frequent plasmid-mediated quinolone resistance gene was oqxAB at 31.7 %, followed by qnrS at 26.2 %, qnrB at 25.7 %, and aac(6')-Ib-cr at 25.7 %. QnrA, qnrD, qebA, and qnrC were not detected among the isolates. Aac (3')-II, aac (6')-Ib, aph (3')-VI, armA, qnrB, qnrS, and acc(6')-Ib-cr were significantly associated with non-susceptibility to aminoglycosides, quinolones, and beta-lactams. Among 27 randomly selected K. pneumoniae isolates, the most common sequence type was ST2096, followed by ST348 and ST1207. Overall, 19 sequence types were observed, confirming a high level of genetic diversity among the isolates. High percentages of non-susceptibility to the studied antimicrobials were found and were associated with the presence of several resistance genes. Similar studies should be periodically carried out to monitor changes in the prevalence of resistance phenotypes and genotypes of isolates.

Correlation of CRISPR/Cas and Antimicrobial Resistance in Klebsiella pneumoniae Clinical Isolates Recovered from Patients in Egypt Compared to Global Strains

The CRISPR/Cas system has been long known to interfere with the acquisition of foreign genetic elements and was recommended as a tool for fighting antimicrobial resistance. The current study aimed to explore the prevalence of the CRISPR/Cas system in Klebsiella pneumoniae isolates recovered from patients in Egypt in comparison to global strains and correlate the CRISPR/Cas to susceptibility to antimicrobial agents. A total of 181 clinical isolates were PCR-screened for cas and selected antimicrobial resistance genes (ARGs). In parallel, 888 complete genome sequences were retrieved from the NCBI database for in silico analysis. CRISPR/Cas was found in 46 (25.4%) isolates, comprising 18.8% type I-E and 6.6% type I-E*. Multidrug resistance (MDR) and extensive drug resistance (XDR) were found in 73.5% and 25.4% of the isolates, respectively. More than 95% of the CRISPR/Cas-bearing isolates were MDR (65.2%) or XDR (32.6%). No significant difference was found in the susceptibility to the tested antimicrobial agents among the CRISPR/Cas-positive and -negative isolates. The same finding was obtained for the majority of the screened ARGs. Among the published genomes, 23.2% carried CRISPR/Cas, with a higher share of I-E* (12.8%). They were confined to specific sequence types (STs), most commonly ST147, ST23, ST15, and ST14. More plasmids and ARGs were carried by the CRISPR/Cas-negative group than others, but their distribution in the two groups was not significantly different. The prevalence of some ARGs, such as blaKPC, blaTEM, and rmtB, was significantly higher among the genomes of the CRISPR/Cas-negative strains. A weak, nonsignificant positive correlation was found between the number of spacers and the number of resistance plasmids and ARGs. In conclusion, the correlation between CRISPR/Cas and susceptibility to antimicrobial agents or bearing resistance plasmids and ARGs was found to be nonsignificant. Plasmid-targeting spacers might not be naturally captured by CRISPR/Cas. Spacer match analysis is recommended to provide a clearer image of the exact behavior of CRISPR/Cas towards resistance plasmids.

Fluoroquinolone-resistance mechanisms and molecular epidemiology of ciprofloxacin-resistant Klebsiella pneumoniae isolates in Iran

Klebsiella pneumoniae is an important cause of nosocomial infections and displays increasing resistance to fluoroquinolones (FQ). This study surveyed the mechanisms of FQ resistance and molecular typing of K. pneumoniae isolates from intensive care units patients in Tehran, Iran. A total of 48 ciprofloxacin (CIP) resistant K. pneumoniae isolates from urine samples were included in this study. Broth microdilution assays revealed high-level CIP resistance (MIC > 32 μg/mL) in 31.25% of the isolates. Plasmid-mediated quinolone resistance genes were detected in 41 (85.4%) isolates. Among which, qnrS (41.67%) was the most prevalent followed by qnrD (35.42%), qnrB (27.1%), qnrA (25%), qepA (22.9%), aac(6')-Ib-cr (20.83%), and qnrC (6.25%). Target site mutations (gyrA and parC) were assessed using PCR and sequencing on all isolates. A single mutation in gyrA (S83I) was found in 13 (27.1%) isolates and two isolates harbored six simultaneous mutations. Fourteen isolates (29.2%) had mutations in parC and S129A and A141V mutations were the most prevalent. Real time PCR showed an increase in the expression level of acrB and oqxB efflux genes in 68.75 and 29.16% isolates, respectively. Enterobacterial repetitive intergenic consensus (ERIC)-PCR revealed 14 genotypes and 11 of them were classified by multilocus sequence typing (MLST) into 11 different sequence types belonging to seven clonal complexes and two singletons, most of them have not been reported in Iran yet. We are concerned about the spread of these clones throughout our country. Most FQ resistance mechanisms were detected among our isolates. However, target site mutation had the greatest effect on CIP resistance among our isolates.

Prevalence of Plasmid-Mediated Quinolone Resistance Genes and Molecular Typing of Klebsiella pneumoniae Isolates from Blood Cultures in Milad Hospital, Tehran, Iran, Within 2018 - 2019

Background: Plasmid-mediated quinolone resistance (PMQR) determinants are commonly characterized in Klebsiella pneumoniae isolates worldwide and complicate the treatment of infections caused by this bacterium. Objectives: This study aimed to investigate the prevalence of PMQR determinants and molecular typing of blood isolates of K. pneumoniae in Milad hospital in Tehran, Iran, within 2018 - 2019. Methods: A total of 100 K. pneumoniae isolates were tested for susceptibility to quinolones using the disk diffusion method. The minimum inhibitory concentrations (MICs) of ciprofloxacin (CIP) and levofloxacin (LEV) were determined using the microdilution broth method. The PMQR determinants were detected by polymerase chain reaction (PCR) assay, and the genetic relationship between the isolates was assessed using enterobacterial repetitive intergenic consensus (ERIC)-PCR. Results: The resistance rates of the isolates to LEV, CIP, nalidixic acid, and norfloxacin were determined to be 62%, 46%, 29%, and 23%, respectively. Eighty-one isolates were resistant to at least one tested quinolone. A high-level CIP and LEV resistance (MIC > 32 mg/L) was observed in 15 (18.51%) and 36 (44.44%) isolates, respectively. The PMQR genes were detected in 71 (87.65%) isolates. The oqxAB, qnrS, qnrD, qnrB, aac(6')-Ib-cr, qnrA, qepA, and qnrC genes were detected in 71 (87.65%), 30 (37%), 25 (30.8%), 24 (29.6%), 18 (22.2%), 17 (21%), 17 (21%), and 8 (9.9%) isolates, respectively. The ERIC-PCR revealed 64 genotypes among quinolone-resistant isolates. Conclusions: The high prevalence of PMQR genes observed in this study is a significant concern for public health since they can contribute to the spread of fluoroquinolone resistance among clinical isolates. The ERIC-PCR revealed high heterogeneity among the studied isolates, indicating that they emerged from different sources.

Analysis of the Correlation Between Antibiotic Resistance Patterns and Virulence Determinants in Pathogenic Klebsiella pneumoniae Isolates from Egypt

Klebsiella pneumoniae is responsible for a plethora of infections involving multiple body systems. This study investigated K. pneumoniae clinical isolates for virulence-associated characters and antibiotic resistance. First, antibiotic sensitivity was determined for 40 K. pneumoniae clinical isolates. Some virulence and resistance-associated factors were studied phenotypically and genotypically. Multiple resistance profiles were observed (multidrug resistant [MDR; 42.5%], extensive drug resistant [XDR; 35%], and pandrug resistant [PDR; 5%]). Moreover, CTX-M-1, TEM, qnrS, and qnrA genes were detected in 70%, 30%, 60%, and 30% of selected isolates, respectively, and 40% of tested isolates were extended-spectrum β-lactamases (ESBLs) producers. Interestingly, all ESBLs producers harbored class 1 integrase gene (IntI1), while 60% of ESBLs producers harbored both CTX-M-1 and TEM. All tested isolates were capsulated while 87.5% were biofilm producers. Fimbriae were detected in 90% of tested isolates (all were biofilm producers and type 3 fimbriae adhesion gene [mrkD] positive). Sequence analysis of OXA-48, qnrS, and IntI1 revealed 100% identity with published sequences, while sequencing of qnrA, OmpK-35, and iron regulatory protein gene (irp2) showed minor variations in the form of one or few single-nucleotide polymorphism. Altogether, the current study revealed that all MDR, XDR, and PDR K. pneumoniae isolates were multivirulent and all harbored 3-5 virulence genes and 2-9 antimicrobial resistance genes and exhibited 8 and 10 different virulence and antimicrobial resistance profiles, respectively. In this study, we also report a positive correlation between some virulence genes and antimicrobial resistance genes among K. pneumoniae tested isolates.

Enterobacter spp.: Update on Taxonomy, Clinical Aspects, and Emerging Antimicrobial Resistance

The genus Enterobacter is a member of the ESKAPE group, which contains the major resistant bacterial pathogens. First described in 1960, this group member has proven to be more complex as a result of the exponential evolution of phenotypic and genotypic methods. Today, 22 species belong to the Enterobacter genus. These species are described in the environment and have been reported as opportunistic pathogens in plants, animals, and humans. The pathogenicity/virulence of this bacterium remains rather unclear due to the limited amount of work performed to date in this field. In contrast, its resistance against antibacterial agents has been extensively studied. In the face of antibiotic treatment, it is able to manage different mechanisms of resistance via various local and global regulator genes and the modulation of the expression of different proteins, including enzymes (β-lactamases, etc.) or membrane transporters, such as porins and efflux pumps. During various hospital outbreaks, the Enterobacter aerogenes and E. cloacae complex exhibited a multidrug-resistant phenotype, which has stimulated questions about the role of cascade regulation in the emergence of these well-adapted clones.

Plasmid-mediated quinolone resistance: Mechanisms, detection, and epidemiology in the Arab countries

Quinolones are an important antimicrobial class used widely in the treatment of enterobacterial infections. Although there are multiple mechanisms of quinolone resistance, attention should be paid to plasmid-mediated genes due to their ability to facilitate the spread of quinolone resistance, the selection of mutants with a higher-level of quinolone resistance, and the promotion of treatment failure. Since their discovery in 1998, plasmid-mediated quinolone resistance (PMQR) mechanisms have been reported more frequently worldwide especially with the extensive use of quinolones in humans and animals. Nevertheless, data from the Arab countries are rare and often scattered. Understanding the prevalence and distribution of PMQR is essential to stop the irrational use of quinolone in these countries. This manuscript describes the quinolone resistance mechanisms and particularly PMQR among Enterobacteriaceae as well as their methods of detection. Then the available data on the epidemiology of PMQR in clinical and environmental isolates from the Arab countries are extensively reviewed along with the other associated resistance genes. These data shows a wide dissemination of PMQR genes among Enterobacteriaceae isolates from humans, animals, and environments in these countries with increasing rates over the years and a common association with other antibiotic resistance genes as bla_CTX-M-15. The incontrovertible emergence of PMQR in the Arab countries highlights the pressing need for effective stewardship efforts to prevent the selection of a higher rate of quinolone resistance and to preserve these crucial antibiotics.

Prevalence of Plasmid-Mediated Quinolone Resistance in Multidrug-Resistant Gram Negative Bacilli in Egypt

Resistance to quinolone has increased significantly and one of the most reasons is plasmid-mediated quinolone resistance (PMQR). The aim of this study is to detect the prevalence of PMQR in multidrug-resistant (MDR) Gram negative bacilli and to characterize these resistance genes. A total of 420 Gram negative bacilli clinical isolates were collected from patients attending Misr children hospital. Isolates were identified by biochemical reactions, while antimicrobial susceptibility testingwas done by Kirby-Bauer disk diffusion method. Minimum inhibitory concentrations (MIC) of ciprofloxacin were detected by E-test, whereas combined test method was used to detect extended-spectrum β-lactamase (ESBL) production. QnrA, qnrB, and qnrS genes were determined by multiplex polymerase chain reaction (PCR). MDRGram negative bacilli represented 68% (268/420); most of them were recovered from blood culture specimens (21%).Among these MDR isolates21%(60/268) were ciprofloxacin resistant; with MICs >32µg/ml in 95% of the isolates.ESBL production was detected in 11.7% of the studied isolates. The qnr genes were detected in 60%. QnrS and qnrB were the detected genes in 77.8% and 16.7% of the isolates respectively. Both qnrB and qnrS genes were determined simultaneously in 5.5%.QnrB gene was found alone in only one isolate (14.3%) that was ESBL-producer. The most MDR isolates were recovered from blood culture; this confirms the occurrence of these superbugs and their ability to cause life threatening infections. The prevalence of quinolone resistant Gram negative bacilli clinical isolates is high. The mostly prevalent PMQR gene is qnrS followed by qnrB.

The genetic background of antibiotic resistance among clinical uropathogenic Escherichia coli strains

The spreading mechanisms of antibiotic resistance are related to many bacterial and environment factors. The overuse of antibiotics is leading to an unceasing emergence of new multidrug resistant strains. This problem also concerns uropathogenic Escherichia coli strains, which is the most common pathogen causing urinary tract infections. The aim of this study was the genetic analysis of antibiotic resistance in comparison to the phenotypic background of E. coli strains. The characterized collection of E. coli strains isolated 10 years ago from the urine samples of patients with urinary tract infections was used for antimicrobial susceptibility testing (the disc diffusion method) and analysis of antibiotic resistance genes (PCR reaction, sequencing). Additionally, the presence of ESBL strains was analyzed. Fourteen genes were associated with resistance to beta-lactams, aminoglycosides, sulfonamides and quinolones. The genetic analysis revealed that bla_TEM-1 and sul2 were present in almost all of the studied strains. Other drug-resistance genes were very rare or non-existent. Otherwise, the phenotypic resistance to fluoroquinolones was well correlated with the genotypic background of the studied bacteria. The presence of particular genes and specific mutations indicate a high bacterial potential to multidrug resistance. On the other hand, it needs to be emphasized that the standard disk diffusion test for the routine antimicrobial susceptibility analysis is still the best way to estimate the current situation of bacterial drug-resistance.

Molecular Identification of Aminoglycoside-Modifying Enzymes and Plasmid-Mediated Quinolone Resistance Genes among Klebsiella pneumoniae Clinical Isolates Recovered from Egyptian Patients

Inappropriate use of antibiotics in clinical settings is thought to have led to the global emergence and spread of multidrug-resistant pathogens. The goal of this study was to investigate the prevalence of genes encoding aminoglycoside resistance and plasmid-mediated quinolone resistance among clinical isolates of Klebsiella pneumoniae. All K. pneumoniae isolates were phenotypically identified using API 20E and then confirmed genotypically through amplification of the specific K. pneumoniae phoE gene. All isolates were genotyped by the enterobacterial repetitive intergenic consensus polymerase chain reaction technique (ERIC-PCR). Antibiotic susceptibility testing was done by a modified Kirby-Bauer method and broth microdilution. All resistant or intermediate-resistant isolates to either gentamicin or amikacin were screened for 7 different genes encoding aminoglycoside-modifying enzymes (AMEs). In addition, all resistant or intermediate-resistant isolates to either ciprofloxacin or levofloxacin were screened for 5 genes encoding the quinolone resistance protein (Qnr), 1 gene encoding quinolone-modifying enzyme, and 3 genes encoding quinolone efflux pumps. Biotyping using API 20E revealed 13 different biotypes. Genotyping demonstrated that all isolates were related to 2 main phylogenetic groups. Susceptibility testing revealed that carbapenems and tigecycline were the most effective agents. Investigation of genes encoding AMEs revealed that acc(6′)-Ib was the most prevalent, followed by acc(3′)-II, aph(3′)-IV, and ant(3′′)-I. Examination of genes encoding Qnr proteins demonstrated that qnrB was the most prevalent, followed by qnrS, qnrD, and qnrC. It was found that 61%, 26%, and 12% of quinolone-resistant K. pneumoniae isolates harbored acc(6′)-Ib-cr, oqxAB, and qebA, respectively. The current study demonstrated a high prevalence of aminoglycoside and quinolone resistance genes among clinical isolates of K. pneumoniae.

Structural and mechanistic diversity of multidrug transporters

The review article surveys recent structural and mechanistic advances in the field of multi-drug and natural product transporters.

Mechanisms of drug resistance: quinolone resistance

Quinolone antimicrobials are synthetic and widely used in clinical medicine. Resistance emerged with clinical use and became common in some bacterial pathogens. Mechanisms of resistance include two categories of mutation and acquisition of resistance-conferring genes. Resistance mutations in one or both of the two drug target enzymes, DNA gyrase and DNA topoisomerase IV, are commonly in a localized domain of the GyrA and ParE subunits of the respective enzymes and reduce drug binding to the enzyme-DNA complex. Other resistance mutations occur in regulatory genes that control the expression of native efflux pumps localized in the bacterial membrane(s). These pumps have broad substrate profiles that include quinolones as well as other antimicrobials, disinfectants, and dyes. Mutations of both types can accumulate with selection pressure and produce highly resistant strains. Resistance genes acquired on plasmids can confer low-level resistance that promotes the selection of mutational high-level resistance. Plasmid-encoded resistance is due to Qnr proteins that protect the target enzymes from quinolone action, one mutant aminoglycoside-modifying enzyme that also modifies certain quinolones, and mobile efflux pumps. Plasmids with these mechanisms often encode additional antimicrobial resistances and can transfer multidrug resistance that includes quinolones. Thus, the bacterial quinolone resistance armamentarium is large.

Prevalence and characterization of plasmid-mediated quinolone resistance genes in extended-spectrum β-lactamase-producing Enterobacteriaceae in a Tunisian hospital

The objective of the study was to assess the prevalence of plasmid-mediated quinolone resistance (PMQR) genes (qnrA, qnrB, qnrC, qnrD, qnrS, aac(6')-Ib-cr, qepA, and oqxAB) in a collection of 120 extended-spectrum β-lactamases (ESBLs)-producing enterobacteria and to characterize them. Overall, PMQR determinants were detected in 72 (60%) isolates (20 Escherichia coli, 32 Klebsiella pneumoniae, and 20 Enterobacter cloacae). PMQR frequencies were as follows: qnr genes (25.8%), oqxAB (21.6%), and aac(6')-Ib-cr variant (19.2%). Four qnr alleles were identified as qnrB1 (83.8%), qnrB4 (6.4%), qnrB2 (3.2%), and qnrS1 (6.4%). qnr genes were mainly detected in E. cloacae (50%), aac(6')-Ib-cr in E. coli (47.5%), and oqxAB in K. pneumoniae (65%). Overall, blaCTX-M-15 (90.3%) was the most prevalent blaESBL type followed by blaSHV-12 (6.4%) and blaSHV-27 (2.7%). Rates of mutations in gyrA and parC genes were 75% for E. coli, 72.8% for K. pneumoniae, and 50% for E. cloacae. Isolates with mutations in their quinolone resistance-determining regions exhibited high fluoroquinolones resistance levels compared to those with wild ones. Genetic study of PMQR-harboring isolates revealed a great genomic diversity among each Enterobacteriaceae species. Our findings indicate the high prevalence of PMQR determinants among ESBL-producing Enterobacteriaceae isolates from our hospital and their diffusion in various unrelated CTX-M-15-producing clones.

Interplay between plasmid-mediated and chromosomal-mediated fluoroquinolone resistance and bacterial fitness in Escherichia coli

OBJECTIVES

The aim of this study was to analyse the interplay among plasmid-mediated qnr genes, alone or in combination with multiple chromosomal-mediated fluoroquinolone (FQ) resistance determinants, susceptibility to FQs and bacterial fitness in an isogenic Escherichia coli collection.

METHODS

E. coli ATCC 25922 was used to modify or delete chromosomal genes. qnr genes were cloned into the pBK-CMV vector. The MICs of FQs were determined by microdilution. Mutant prevention concentration and frequency of mutants were evaluated. Bacterial fitness was analysed using ΔlacZ system competition assays using in vitro and in vivo models.

RESULTS

The relationships between the number of resistance mutations and bacterial fitness were complex. With specific combinations of resistance mechanisms the addition of a new resistance mutation was shown to improve bacterial fitness. qnrA1 caused a decrease in fitness (7%-21%) while qnrS1 caused an increase in fitness (9%-21%) when combined with chromosomal mutations. We identified susceptible triple mutants in which the acquisition of a fourth resistance mutation significantly increased fitness and at the same time reached the clinical resistance level (the acquisition of qnrS1 in a S83L + D87N + ΔmarR genetic background). A strong correlation with the production of reactive oxygen species, as well as changes in susceptibility, was observed following treatment with ciprofloxacin.

CONCLUSIONS

Our data indicate that there may be critical stages (depending on the genotype) in resistance development, including chromosomal- and plasmid-mediated mechanisms, at which some low-fitness mutants below the resistance breakpoint are able to evolve clinical resistance with just one or two mutations, and show increased fitness.