Contribution of target alteration, protection and efflux pump in achieving high ciprofloxacin resistance in Enterobacteriaceae

Navigating fluoroquinolone resistance in Gram-negative bacteria: a comprehensive evaluation

Since the introduction of quinolone and fluoroquinolone antibiotics to treat bacterial infections in the 1960s, there has been a pronounced increase in the number of bacterial species that have developed resistance to fluoroquinolone treatment. In 2017, the World Health Organization established a priority list of the most critical Gram-negative resistant pathogens. These included Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli. In the last three decades, investigations into the mechanisms of fluoroquinolone resistance have revealed that mutations in the target enzymes of fluoroquinolones, DNA gyrase or topoisomerase IV, are the most prevalent mechanism conferring high levels of resistance. Alterations to porins and efflux pumps that facilitate fluoroquinolone permeation and extrusion across the bacterial cell membrane also contribute to the development of resistance. However, there is a growing observation of novel mutants with newer generations of fluoroquinolones, highlighting the need for novel treatments. Currently, steady progress has been made in the development of novel antimicrobial agents that target DNA gyrase or topoisomerase IV through different avenues than current fluoroquinolones to prevent target-mediated resistance. Therefore, an updated review of the current understanding of fluoroquinolone resistance within the literature is imperative to aid in future investigations.

Genotypic and phenotypic characterization of determinants that mediate antimicrobial resistance in Escherichia coli strains of clinical origin in South-Western Nigeria

Background

Multidrug resistant bacterial pathogens employ different mechanisms in evading the action of antibiotics. Multidrug resistance is wide spread among strains of Escherichia coli implicated in several infections including urinary tract infections, gastrointestinal infections, meningitis and bacteraemia.

Aim/Objective

This study investigates the antibiotic resistance profile, efflux pump activity and biofilm formation ability of E. coli strains isolated from clinical samples.

Methods

A total of 32 E. coli strains isolated from clinical samples were characterized and subjected to antibiotic susceptibility testing using standard methods. Isolates were screened phenotypically for biofilm formation and efflux pump activity. While molecular detection of genes encoding curli fimbriae and efflux pump activity was done by PCR.

Results

All 32 (100%) E. coli isolates were resistant to ceftazidime, cefuroxime, cefixime, amoxicillin-clavulanate, ofloxacin and ciprofloxacin. While 30 (93.8%) were resistant to gentamicin, 27 (84.4%) were resistant to cefepime and the least resistance of 15.6% was to imipenem. Efflux pump encoding gene tolC was detected in 13(40.6%) of the isolates, while 1(3.1%) harboured acrA gene. acrB gene was not detected in any of the isolates. Seven (21.9%) of the isolates were strong biofilm formers, while 5 (15.6%) and 20 (62.5%) were moderate and weak biofilm formers respectively. csgA gene was detected in all E. coli isolates.

Discussion

High antibiotic resistance of E. coli strains observed in this study is of public health significance. . It is therefore important to scale up efforts in regular monitoring of antibiotic resistance in both community and hospital settings.

Increasing antimicrobial susceptibility of MDR Salmonella with the efflux pump inhibitor 1-(1-Naphthylmethyl)-piperazine

Salmonella is a widespread foodborne pathogen that can exhibit multidrug resistance (MDR; resistance to ≥3 antimicrobial classes). Therefore, the development of new preventative measures against MDR Salmonella is highly important. Bacterial antibiotic resistance is commonly mediated by efflux pumps. In this study, two compounds that block efflux pump activity, 1-(1-Naphthylmethyl)-Piperazine (NMP) and Phenylalanine-arginine β-naphthylamide (PaβN), were tested with the antibiotic tetracycline to determine if a synergistic reduction in resistance could be achieved in tetracycline-resistant Salmonella. The efflux pump inhibitors (EPIs) reduced Salmonella resistance to tetracycline by 16 to 32-fold in several tetracycline resistant isolates. For example, the tetracycline minimum inhibitory concentration (MIC) for MDR Salmonella enterica serovar I 4,[5],12:i:- USDA15WA-1 (SX 238) was 256 μg/mL. However, in the presence of NMP (250 μg/mL), the MIC dropped to 8 μg/mL which is below the Clinical Laboratory Standards Institute (CLSI) breakpoint for tetracycline resistance in Salmonella (≥16 μg/mL). Confocal and transmission electron microscopy revealed NMP-mediated damage to Salmonella membranes at a higher concentration (1000 μg/mL), implying that the EPI disrupts membrane morphology which can lead to cell death; however, this effect was dependent on NMP concentration, as NMP blocked efflux activity with less of a membrane-disrupting effect at a lower concentration (250 μg/mL). These findings suggest that the use of EPIs can reduce the MIC of tetracycline and restore the effectiveness of the antibiotic against tetracycline-resistant Salmonella.

Contribution of efflux and mutations in fluoroquinolone susceptibility in MDR enterobacterial isolates: a quantitative and molecular study

OBJECTIVES

The emergence of MDR strains is a public health problem in the management of associated infections. Several resistance mechanisms are present, and antibiotic efflux is often found at the same time as enzyme resistance and/or target mutations. However, in the laboratory routinely, only the latter two are identified and the prevalence of antibiotic expulsion is underestimated, causing a misinterpretation of the bacterial resistance phenotype. The development of a diagnostic system to quantify the efflux routinely would thus improve the management of patients.

METHODS

A quantitative technique based on detection of clinically used fluoroquinolones was investigated in Enterobacteriaceae clinical strains with a high or basal efflux activity. The detail of efflux involvement was studied from MIC determination and antibiotic accumulation inside bacteria. WGS was carried out on selected strains to determine the genetic background associated with efflux expression.

RESULTS

Only 1 Klebsiella pneumoniae isolate exhibited a lack of efflux whereas 13 isolates had a basal efflux and 8 presented efflux pump overexpression. The antibiotic accumulation evidenced the efficacy of the efflux mechanism in strains, and the contribution of dynamic expulsion versus target mutations in fluoroquinolone susceptibility.

CONCLUSIONS

We confirmed that phenylalanine arginine β-naphthylamide is not a reliable marker of efflux due to the affinity of the AcrB efflux pump for different substrates. We have developed an accumulation test that can be used efficiently on clinical isolates collected by the biological laboratory. The experimental conditions and protocols ensure a robust assay that with improvements in practice, expertise and equipment could be transferred to the hospital laboratory to diagnose the contribution of efflux in Gram-negative bacteria.

Molecular and phenotypic characterization of efflux pump and biofilm in multi-drug resistant non-typhoidal Salmonella Serovars isolated from food animals and handlers in Lagos Nigeria

BACKGROUND

Multidrug resistance efflux pumps and biofilm formation are mechanisms by which bacteria can evade the actions of many antimicrobials. Antibiotic resistant non-typhoidal Salmonella serovars have become wide spread causing infections that result in high morbidity and mortality globally. The aim of this study was to evaluate the efflux pump activity and biofilm forming capability of multidrug resistant non-typhoidal Salmonella (NTS) serovars isolated from food handlers and animals (cattle, chicken and sheep) in Lagos.

METHODS

Forty eight NTS serovars were subjected to antibiotic susceptibility testing by the disc diffusion method and phenotypic characterization of biofilm formation was done by tissue culture plate method. Phenotypic evaluation of efflux pump activity was done by the ethidium bromide cartwheel method and genes encoding biofilm formation and efflux pump activity were determined by PCR.

RESULTS

All 48 Salmonella isolates displayed resistance to one or more classes of test antibiotics with 100% resistance to amoxicillin-clavulanic acid. Phenotypically, 28 (58.3%) of the isolates exhibited efflux pump activity. However, genotypically, 7 (14.6%) of the isolates harboured acrA, acrB and tolC, 8 (16.7%) harboured acrA, acrD and tolC while 33 (68.8%) possessed acrA, acrB, acrD and tolC. All (100%) the isolates phenotypically had the ability to form biofilm with 23 (47.9%), 24 (50.0%), 1 (2.1%) categorized as strong (SBF), moderate (MBF) and weak (WBF) biofilm formers respectively but csgA gene was detected in only 23 (47.9%) of them. Antibiotic resistance frequency was significant (p < 0.05) in SBF and MBF and efflux pump activity was detected in 6, 21, and 1 SBF, MBF and WBF respectively.

CONCLUSION

These data suggest that Salmonella serovars isolated from different food animals and humans possess active efflux pumps and biofilm forming potential which has an interplay in antibiotic resistance. There is need for prudent use of antibiotics in veterinary medicine and scrupulous hygiene practice to prevent the transmission of multidrug resistant Salmonella species within the food chain.

Study of antimicrobial resistance for the causative agent of the bovine reproductive system infection by the NGS method

In the present study, the biomaterial specimen derived from a farm animal with a chronic reproductive system infection was carefully investigated using the Next Generation Sequencing method. The bacterial DNA of the genus Enterobacter was detected. The genetic determinants of resistance to 12 classes of antibiotics were identified in the genome of this microorganism. The data obtained highlight the necessity of strengthening global control over the spread of resistant microorganism strains in agriculture especially in the animal husbandry sector.

High frequency of the combined presence of QRDR mutations and PMQR determinants in multidrug-resistant Klebsiella pneumoniae and Escherichia coli isolates from nosocomial and community-acquired infections

Plasmid-mediated quinolone resistance (PMQR) determinants combined with mutations in quinolone resistance-determining regions (QRDRs) and clonal dissemination were investigated in 40 fluoroquinolone-resistant Klebsiella pneumoniae and Escherichia coli isolates from nosocomial and community-acquired infections. We observed nucleotide substitutions in gyrA (Ser83Ile, Val37Leu, Lys154Arg, Ser171Ala, Ser19Asn, Ile198Val, Ser83Tyr, Ser83Leu, Asp87Asn and Asp87Gly) and parC genes (Ser80Ile, Glu84Lys, Ala129Ser, Val141Ala and Glu84Gly). Two novel substitutions were detected in the gyrA gene (Val37Leu and Ile198Val). The presence of PMQR genes predominated in community isolates (55.5 %). In addition to the frequent presence of the class 1 integron in isolates from community-acquired infections, the genetic similarity results obtained by PFGE showed high genomic diversity. This study suggests that management of multidrug-resistant Enterobacteriaceae isolates from the community are a possible source of genetic mobile elements that carry genes that confer resistance to fluoroquinolones. More attention should be paid to the surveillance of community-acquired infections.