Minimum Inhibitory Concentrations Of Ciprofloxacin Research Articles

Detection of Overexpression of Efflux Pump Expression in Fluoroquinolone-Resistant Pseudomonas aeruginosa Isolates.

Context:Fluoroquinolones are the most effective antibiotics against Pseudomonas aeruginosa; many strains, however, have shown resistance due to mutations in DNA gyrase, topoisomerase IV, or in the efflux pumps. Little is known about P. aeruginosa efflux pump resistance mechanisms in the Kingdom of Bahrain.Aim:The aim was to study efflux pump-mediated fluoroquinolone resistance among P. aeruginosa isolates using phenotypic (E-test and agar dilution) and genotypic (real-time-polymerase chain reaction [RT-PCR]) methods.Materials and Methods:Fifty ciprofloxacin-resistant P. aeruginosa isolates were included in this study. Genus and species of P. aeruginosa were confirmed by conventional PCR. The minimum inhibitory concentration (MIC) of ciprofloxacin with and without carbonyl cyanide 3-chlorophenylhydrazone (CCCP) was determined by E-test and agar dilution test. The overexpression of genes MexB, MexD, MexF, and MexY was measured by RT-PCR.Results:All isolates were confirmed as P. aeruginosa. Among the fifty isolates, four showed reduction in ciprofloxacin MIC after addition of CCCP. These four isolates showed upregulation of expression of at least one of the four genes by RT-PCR. The mean gene expression of MexB, MexD, MexF, and MexY increased by 1.6, 4.65, 3.4, and 3.68-fold, respectively.Conclusion:The results demonstrate the presence and type of efflux pump overexpression, mandating for large multicentric studies.

Cinnamaldehyde: a compound with antimicrobial and synergistic activity against ESBL-producing quinolone-resistant pathogenic Enterobacteriaceae.

Usage of cephalosporin and quinolone antibiotics has aggravated the development of extended-spectrum beta-lactamase (ESBL)-producing quinolone-resistant (QR) pathogenic Enterobacteriaceae. The present study aims to determine antimicrobial activity of cinnamaldehyde alone or in combination with cefotaxime/ciprofloxacin to reverse the drug resistance and evaluations of efficacy, and possible molecular mechanism of action of the combination was also evaluated using in vitro assays. Broth microdilution assay was used to determine minimum inhibitory concentrations (MICs) of cinnamaldehyde and antibiotics against ESBL-QR Enterobacteriaceae. Synergistic effect and dynamic interaction with antibiotics were further examined by checkerboard assay, isobologram analysis, and time-kill assay, respectively. Cellular morphology of bacteria was viewed with scanning electron microscopy (SEM). Effects of cinnamaldehyde and its combination on the expression of gene encoding-porins (ompC, ompF, ompK35, and ompK36), efflux pump genes (acrB-E. coli, acrB-K. pneumoniae), and antibiotic-resistant genes (blaTEM, blaSHV, blaCTXM, and QnrB) were evaluated using real-time quantitative PCR (RT-qPCR). Majority of the E. coli (32.1%) and K. pneumoniae (24.2%) isolates demonstrated MIC of cinnamaldehyde at 7.34μg/mL and 0.91g/mL, respectively. Synergism between cinnamaldehyde and cefotaxime was noted among 75% E. coli and 60.6% K. pneumoniae. Similarly, synergism with ciprofloxacin was observed among 39.6% and 42.4% of the bacteria, respectively. Thus, cinnamaldehyde reduced MIC of cefotaxime and ciprofloxacin 2-1024-fold with bactericidal and/synergistic effect after 24h. Cinnamaldehyde and its combination altered gene expression by ~ 1.6 to ~ 400-fold. Distorted bacterial cell structures were visible after treatment with cinnamaldehyde and/or with cefotaxime/ciprofloxacin. The results indicated the potential efficacy and mode of action of cinnamaldehyde alone and in combination with antibiotics against pathogenic ESBL-QR bacteria.

Prevalence, sequence type, and quinolone resistance of Neisseria lactamica carried in children younger than 15 years in Shanghai, China

Neisseria lactamica has an important influence on carriage and antimicrobial susceptibility of N. meningitidis, a major pathogen of septicemia and meningitis. In China, quinolone resistance is highly prevalent in N. meningitidis but unknown in N. lactamica. This study investigates the carriage rate, sequence type, and ciprofloxacin resistance of N. lactamica in children in China. During 2014-2016, throat swabs were collected from 2,239 children in Shanghai. The ciprofloxacin minimum inhibitory concentrations of the isolates were determined by the agar dilution method. The overall carriage rate of N. lactamica was higher (8.9%) than that of N. meningitidis (0.9%) and peaked at two years (37.1%). The resistance frequency of N. lactamica to ciprofloxacin was 98.5% (197/200). There were 65 sequence types (STs). Clonal complex (cc) 640 (45.5%) dominated, while ST-14031 was predominant (37%, 74/200). All isolates possessed a GyrA mutation; 17 isolates (8.5%) harbored additionally a ParC mutation. Assigned to 39 different alleles, the gyrA sequences from these N. lactamica isolates formed an N. lactamica cluster, which also included eight alleles from N. meningitidis. The N. lactamica isolates in China showed distinct characteristics with lower genetic diversity and a much higher prevalence of quinolone resistance than in other countries.

Pefloxacin susceptibility as a surrogate test to detect ciprofloxacin-resistance in typhoidal Salmonella

Pefloxacin susceptibility as a surrogate test to detect ciprofloxacin-resistance in typhoidal Salmonella - IJMR- Print ISSN No: - 2394-546X Online ISSN No:- 2394-5478 Article DOI No:- 10.18231/j.ijmr.2019.044, Indian Journal of Microbiology Research-Indian J Microbiol Res

A study on prevalence of plasmid mediated quinolone resistant genes in Klebsiella pneumoniae

Introduction: Fluoroquinolone resistance is increasingly been reported in Enterobacteriaceae. Resistance to quinolones among Enterobacteriaceae is mediated by point mutations in chromosomal genes that encode the subunits of DNA-gyrase and topoisomerase IV. Objectives: The present study was done to identify quinolone resistant Klebsiella pneumoniae isolates from clinical samples and to detect the prevalence of plasmid mediated quinolone resistance genes. Materials & Methods: A total of 63 isolates from various clinical samples were identified by standard biochemical methods. Antimicrobial resistance pattern of these isolates were performed by disk diffusion method as per guidelines of CLSI. Minimum Inhibitory Concentration for Ciprofloxacin was determined by E test strips with concentration gradient of 0.002-32 µg/ml. Detection of plasmid mediated quinolone resistance genes was performed by PCR. Results: By disk diffusion, 90.99% isolates were found to be resistant to Ciprofloxacin. The sensitivity of isolates to Imipenem was found to be 99.10%. About 50.74% isolates were resistant to Aminoglycosides and 61.19% were resistant to third generation Cephalosporins. By E test, 80.95% isolates were resistant for Ciprofloxacin with MIC of >1µg/ml. By PCR, out of 63 isolates, 6 (9.52%) showed aac (6’) – Ib - cr gene, 7 (11.11%) were positive for qnr A gene, 29 (46.03%) for both qnr B and aac (6’) - Ib-cr gene and 8 (12.70%) for qnr B gene. Conclusion: The transferrable nature of Plasmid mediated fluoroquinolone resistant genes favours the dissemination of the resistant genes between different bacterial genera and limit therapeutic options available. The prevalence of plasmid mediated quinolone resistance mediated by qnr A, qnrB and aac (6’) - Ib-cr gene results in multidrug resistance among Klebsiella pneumoniae.

Chemical composition, antimicrobial activity and synergistic potential of essential oil from endemic Lavandula maroccana (Mill.)

The aims of the present study were to evaluate for the first time the chemical composition and in vitro antimicrobial potential of essential oil (EO) obtained from endemic Lavandula maroccana (Murb.) singly or in combination with some conventional antimicrobials (ciprofloxacin, vancomycin, fluconazol, and amphotericin B) against a panel of pathogenic microorganisms. The gas chromatography/mass spectrometry (GC/MS) analysis of EO led to the identification of 20 components, representing 98.8% of the total oil. The main constituent was the phenolic monoterpene carvacrol (78.2%), followed by 2-Methoxy-4-vinylphenol (2.5%), and Spathulenol (2.2%). The results of the antimicrobial assays demonstrated that L. maroccana EO displayed moderate activity, with minimal inhibitory concentration (MIC) values of 4.604 mg/mL for yeasts and ranged from 2.302 to 18.416 mg/mL for bacteria. According to FIC index values, the combination between L. maroccana EO and conventional antimicrobials elicited very promising synergistic effects against all tested strains. In fact, at sub-inhibitory concentrations L. maroccana EO contributed to the decrease of fluconazol and amphotericin B MICs of Candida strains by 64- to 128-fold and by 2- to 4-fold, respectively. Regarding bacterial strains, L. maroccana EO has reduced the ciprofloxacin and vancomycin MICs by 4- to 33-fold and by 2- to 4-fold, respectively. From these results, it can be concluded that L. maroccana EO can be considered as a promising source of natural antimicrobials, and constitute a potential candidate to be used in combination antibiotic therapy in order to reduce the overuse of antibiotics, and to combat some human infectious diseases.

Characterization of plasmid mediated quinolone resistance determinants in ciprofloxacin resistant-Escherichia coli from chicken meat produced by integrated broiler operations in Korea

The purpose of this study was to determine the genetic characterization of ciprofloxacin resistant- Escherichia coli recovered from 7 different integrated broiler operations in Korea. Among the 157 E. coli isolated from chicken meat produced by integrated broiler operations, 75 (47.8%) were observed to be ciprofloxacin resistant-E. coli. However, the prevalence varied from 25.0 to 75.0%, in chicken meat, indicating variation in ciprofloxacin resistant E. coli occurrence among the operations. Among the 75 ciprofloxacin resistant-E. coli isolates, 10 showed plasmid-mediated quinolone resistance (PMQR) genes, aac(6′)-Ib-cr, qnrS1 and qnrB4. Among the 10 PMQR-positive E. coli, a double amino-acid exchange in both gyrA and parC with ciprofloxacin minimum inhibitory concentrations of ≥16 μg/mL was noted in 8 isolates, and 4 transconjugants (40.0%) expressed similar antimicrobial resistance patterns and revealed the presence of PMQR genes and β-lactamase genes. Our findings suggest that E. coli with resistance to ciprofloxacin can now be found in association with integrated broiler operations, thus highlighting the need for monitoring and prevention programs in integrated operations.

Estimating the burden of enteric fever in Chhattisgarh: A single-center study on culture-positive cases from a newly built tertiary care hospital.

BACKGROUND:Enteric fever is the most common cause of community acquired blood stream infections in under developed and developing countries. The enteric fever is exclusive to humans and transmitted through the faeco-oral route. Though India is an endemic zone for enteric fever, the data is very scarce from Central India. The present study was undertaken to determine the prevalence of enteric fever in this region and to know the antimicrobial susceptibility pattern of the isolated typhoidal Salmonellae.MATERIAL AND METHOD:We conducted a retrospective analysis of blood culture positive cases of enteric fever over a period of two years (December 2015 to December 2017). All blood cultures submitted for suspected enteric fever and associated symptoms were included in the study. Relevant demographic, clinical and laboratory data were analyzed.RESULT:A total of 51 cases (3.56%) were of typhoidal Salmonella from a total of 1430 blood culture submission. Salmonella Typhi were 70.5% while Salmonella Paratyphi A were 29.5% of the total isolated Salmonellae. The most vulnerable age group was 10-19years (41.2%). The mean minimum inhibitory concentration of ciprofloxacin for Salmonella Typhi and Salmonella Paratyphi A are 1.20 and 1.97 μg/ml respectively. All the isolates were susceptible to ceftriaxone. Highest isolation was in the July – September quarter (35.3%).CONCLUSION:There is a high prevalence of the disease which needs urgent focus on safe water, sanitation services and also to establish guidelines for empiric therapy for enteric fever.

Phenotypic screening for quinolone resistance in Escherichia coli

Recent studies show that rectal colonization with low-level ciprofloxacin-resistant Escherichia coli (ciprofloxacin minimal inhibitory concentration (MIC) above the epidemiological cutoff point, but below the clinical breakpoint for resistance), i.e., in the range > 0.06–0.5 mg/L is an independent risk factor for febrile urinary tract infection after transrectal ultrasound-guided biopsy (TRUS-B) of the prostate, adding to the other risk posed by established ciprofloxacin resistance in E. coli (MIC > 0.5 mg/L) as currently defined. We aimed to identify the quinolone that by disk diffusion best discriminates phenotypic wild-type isolates (ciprofloxacin MIC ≤ 0.06 mg/L) of E. coli from isolates with acquired resistance, and to determine the resistance genotype of each isolate. The susceptibility of 108 E. coli isolates was evaluated by ciprofloxacin, levofloxacin, moxifloxacin, nalidixic acid, and pefloxacin disk diffusion and correlated to ciprofloxacin MIC (broth microdilution) using EUCAST methodology. Genotypic resistance was identified by PCR and DNA sequencing. The specificity was 100% for all quinolone disks. Sensitivity varied substantially, as follows: ciprofloxacin 59%, levofloxacin 46%, moxifloxacin 59%, nalidixic acid 97%, and pefloxacin 97%. We suggest that in situations where low-level quinolone resistance might be of importance, such as when screening for quinolone resistance in fecal samples pre-TRUS-B, a pefloxacin (S ≥ 24 mm) or nalidixic acid (S ≥ 19 mm) disk, or a combination of the two, should be used. In a setting where plasmid-mediated resistance is prevalent, pefloxacin might perform better than nalidixic acid.

Genetic mutations in the quinolone resistance-determining region are related to changes in the epidemiological profile of methicillin-resistant Staphylococcus aureus isolates.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important causative agent of nosocomial infections. Mutations in the quinolone resistance-determining regions (QRDRs) of the gyr and par genes have been described. This study aimed to characterise phenotypic and genotypic fluoroquinolone resistance in 69 MRSA isolates of different clonal lineages from hospitals in Rio de Janeiro, Brazil. QRDR mutations in the gyrA, gyrB, parC and parE genes were detected by DNA sequencing. Minimum inhibitory concentrations (MICs) for ciprofloxacin and moxifloxacin were determined by broth microdilution. The occurrence of associations between mutations and MICs among the different clonal lineages of MRSA isolates was then verified. Most isolates from the USA400/ST1/SCCmec IV lineage, but mainly USA100/ST5/SCCmec II isolates, which have been more recently found in Rio de Janeiro hospitals, showed different patterns of mutations, including double mutation in the QRDR of parC (Ser-80⿿⿿⿿Tyr and Glu-84⿿⿿⿿Lys/Gly) and/or gyrA (Ser-84⿿⿿⿿Leu and/or Glu-88⿿⿿⿿Lys) associated with higher moxifloxacin and ciprofloxacin MICs (MIC90, ⿥8⿿mg/L and 256⿿mg/L, respectively). On the other hand, all USA800/ST5/SCCmec IV and the BEC/ST239/SCCmec III isolates, which have disappeared from hospitals, showed single mutations in parC (Ser-80⿿⿿⿿Phe) and gyrA (Ser-84⿿⿿⿿Leu or Glu-88⿿⿿⿿Gly) and lower fluoroquinolones MICs (MIC90, ⿥2⿿mg/L and ⿥16⿿mg/L). This study highlights an increase in the number and types of mutations in the QRDRs ofgyrA and parC associated with high fluoroquinolones MICs that may be related to changes in the epidemiological profile of MRSA isolates from hospitals in Rio de Janeiro.

<p>A novel mechanism of action of ketoconazole: inhibition of the <em>NorA</em> efflux pump system and biofilm formation in multidrug-resistant <em>Staphylococcus aureus</em></p>

Background: The rapid emergence of antimicrobial resistance among Gram-positive organisms, especially staphylococci, has become a serious clinical challenge. Efflux machinery and biofilm formation are considered two of the main causes of antimicrobial resistance and therapy failure.Aim: Our study aims to evaluate the antibiofilm and efflux pump inhibitory activity of the antifungal ketoconazole against multidrug-resistant (MDR) Staphylococcus aureus.Methods: Ketoconazole was tested for its effect on the following: minimum inhibitory concentrations (MICs) of ciprofloxacin, norfloxacin, levofloxacin, and ethidium bromide (EtBr) by the broth microdilution method, the efflux of EtBr by NorA-positive MDR S. aureus, and the relative expression of NorA, NorB, and NorC efflux pump genes. Docking studies of ketoconazole were performed using 1PW4 (glycerol-3-phosphate transporter from Escherichia coli which was the representative structure from the major facilitator superfamily).Results: Ketoconazole significantly decreased the MICs of levofloxacin, ciprofloxacin, norfloxacin, and EtBr (a substrate for efflux pump) by 8 to 1024-fold (P<0.01) and decreased the efflux of EtBr. Furthermore, a time-kill assay revealed that combinations of levofloxacin with ketoconazole or carbonyl cyanide m-chlorophenylhydrazone showed no growth for the tested strains after 24 h in comparison to the effect of levofloxacin alone. Docking studies and the ability of ketoconazole to diminish the relative expression of NorA gene in comparison to control (untreated strains) confirmed its action as an efflux pump inhibitor. Conclusion: The findings showed that the antifungal ketoconazole has no antibacterial activity but can potentiate the activity of the fluroquinolones against MDR S. aureus via inhibiting efflux pump and biofilm formation in vitro.

Antioxidant activity and evidence for synergism of Cannabis sativa (L.) essential oil with antimicrobial standards

The present work was conducted to study the antioxidant activity and to determine for the first time the antimicrobial potential of Moroccan Cannabis sativa essential oil (EO) singly or in combination with two conventional antibiotics (fluconazol and ciprofloxacin) against some resistant and pathogenic microorganisms. The chemical composition analyzed by means of GC/MS showed that C. sativa EO was characterized by the dominance of (E)-caryophyllene (35.0%), α-humulene (12.8%) and caryophyllene oxide (10.6%). Results from antioxidant tests showed that C. sativa EO exhibit a moderate potency (IC50 = 1.6 ± 0.1 mg/m L for 2,2- diphenyl-1-picrylhydrazyl (DPPH) assay, IC50 = 1.8 ± 0.2 mg/mL for β-carotene/linoleic acid assay, and IC50 = 0.9 ± 0.1 mg/m L for ferric reducing power assay). Regarding antimicrobial assays, the results demonstrated that C. sativa EO displayed interesting antimicrobial activities with minimum inhibitory concentration (MIC) values in the range from (1.2 to 37.8) mg/m L for tested microorganisms. The combination of the studied EO with fluconazol and ciprofloxacin showed a significant decrease in their individual MICs. In fact, at sub-inhibitory concentrations, C. sativa EO contributed to the decrease of ciprofloxacin MICs of bacterial strains by 2- to 64-fold and by16-fold regarding fluconazol MICs against Candida spp. These findings suggest that C. sativa EO can be considered as a potential source of natural antioxidant and antimicrobials, and constitute in combinational treatments a promising strategy to overcome the intense use of antibiotics against some infectious diseases.

Fluoroquinolone-Resistant Salmonella enterica, Campylobacter spp., and Arcobacter butzleri from Local and Imported Poultry Meat in Kumasi, Ghana.

Salmonella and Campylobacter are important gastroenteric pathogens. Arcobacter butzleri is an emerging enteric pathogen. Data on the frequencies of these poultry-associated pathogens on meat products sold in sub-Saharan Africa are scarce. This study aimed to analyze the frequency of Salmonella, Campylobacter, and Arcobacter antibiotic resistance and underlying mechanisms of resistance to fluoroquinolones in locally produced and imported poultry sold in urban Ghana. Chicken meat was collected and cultured on standard media. Bacterial strains were identified by biochemical methods and by mass spectrometry. Antibiotic susceptibility was tested by disk diffusion. Ciprofloxacin-resistant strains were assessed for molecular mechanisms of resistance. Among 200 samples, comprising 34% (n = 68) from the Ghanaian poultry industry and 66% (n = 132) from imports, 9% (n = 17) contained Salmonella, 11% (n = 22) Campylobacter, and 26.5% (n = 53) A. butzleri. Higher overall contamination frequencies were found in local meat. Most common Salmonella serovars identified were Kentucky (n/N = 5/16; 31%) and Poona (n/N = 4/16; 25%). Campylobacter were C. coli (n/N = 10/19; 53%) and C. jejuni (n/N = 9/19; 47%). Resistance to fluoroquinolones was high with 63% (n = 10), 75% (n = 15), and 52% (n = 25) in Salmonella, Campylobacter, and Arcobacter, respectively. A link between Salmonella Kentucky [sequence type (ST) 198] and a ciprofloxacin minimum inhibitory concentration of 16 μg/mL was found. Salmonella Poona-ST308 revealed transferable qnrB2 fluoroquinolone resistance genes. Markedly high frequencies of resistant Salmonella, Campylobacter, and Arcobacter predominant in locally produced meat represent a probable transmission reservoir for human infections. These findings highlight the need for implementation of surveillance systems that focus on food hygiene, use of antibiotics in animal husbandry, and continuous monitoring of the quality of meat products from imports.

GyrA and parC mutations in fluoroquinolone-resistant Neisseria gonorrhoeae isolates from Kenya

BackgroundPhenotypic fluoroquinolone resistance was first reported in Western Kenya in 2009 and later in Coastal Kenya and Nairobi. Until recently gonococcal fluoroquinolone resistance mechanisms in Kenya had not been elucidated. The aim of this paper is to analyze mutations in both gyrA and parC responsible for elevated fluoroquinolone Minimum Inhibitory Concentrations (MICs) in Neisseria gonorrhoeae (GC) isolated from heterosexual individuals from different locations in Kenya between 2013 and 2017.MethodsAntimicrobial Susceptibility Tests were done on 84 GC in an ongoing Sexually Transmitted Infections (STI) surveillance program. Of the 84 isolates, 22 resistant to two or more classes of antimicrobials were chosen for analysis. Antimicrobial susceptibility tests were done using E-test (BioMerieux) and the results were interpreted with reference to European Committee on Antimicrobial Susceptibility Testing (EUCAST) standards. The isolates were sub-cultured, and whole genomes were sequenced using Illumina platform. Reads were assembled de novo using Velvet, and mutations in the GC Quinolone Resistant Determining Regions identified using Bioedit sequence alignment editor. Single Nucleotide Polymorphism based phylogeny was inferred using RaxML.ResultsDouble GyrA amino acid substitutions; S91F and D95G/D95A were identified in 20 isolates. Of these 20 isolates, 14 had an additional E91G ParC substitution and significantly higher ciprofloxacin MICs (p = 0.0044*). On the contrary, norfloxacin MICs of isolates expressing both GyrA and ParC QRDR amino acid changes were not significantly high (p = 0.82) compared to MICs of isolates expressing GyrA substitutions alone. No single GyrA substitution was found in the analyzed isolates, and no isolate contained a ParC substitution without the simultaneous presence of double GyrA substitutions. Maximum likelihood tree clustered the 22 isolates into 6 distinct clades.ConclusionSimultaneous presence of amino acid substitutions in ParC and GyrA has been reported to increase gonococcal fluoroquinolone resistance from different regions in the world. Our findings indicate that GyrA S91F, D95G/D95A and ParC E91G amino acid substitutions mediate high fluoroquinolone resistance in the analyzed Kenyan GC.

In vitro influence of metronidazole on the activities of ciprofloxacin against clinically important bacterial isolates

A continued in vitro investigation into drug-drug interaction is necessary to avert dangerous drug combinations and achieve effective therapy at lower drug concentrations. In this study, the interactions of ciprofloxacin and metronidazole and the effectiveness of the antibacterial combinations against selected bacterial strains were investigated by agar diffusion, macrobroth dilution and the checkerboard assay methods. The results showed that the combined antibiotics had better antibacterial effects than those produced by the ciprofloxacin while no inhibition zone was produced by metronidazole at the concentrations used. At the highest concentration of the combination, the inhibition zones ranged between 28±1.00 mm and 37±1.00 mm while Plesiomonas shigelloidis was highly resistant. While the minimum inhibitory concentrations (MICs) of ciprofloxacin ranged between 0.05 and 3.13 µg/ml and those of metronidazole were between 15.63 and 62.5 µg/ml, the MICs for the antibacterial combinations were between 0.02/0.12 and 3.13/1.56 (Cip/Met) µg/ml against all the test microorganisms. The percentage reduction in the MICs showed that while the MICs of ciprofloxacin were reduced by between 0 and 96.87%, those of metronidazole were reduced by between 0 and 99.80 % when the two antibiotics were combined. The interaction of ciprofloxacin and metronidazole was more of synergy (55.56 %) than additive/indifference (44.4%). The FICI indicating synergistic interaction ranged between 0.035 and 0.375, the FICI indicating additive/indifference interactions ranged between 0.532 and 1.25. No antagonistic interaction was recorded. The lack of antagonism between these antibacterial agents suggested that their combination would be an improved therapy over the use of each antibiotic individually and may be useful in attaining better therapeutic effects in infections where polymicrobial and resistant bacterial strains may be involved.

MexXY Multidrug Efflux System Is More Frequently Overexpressed in Ciprofloxacin Resistant French Clinical Isolates Compared to Hospital Environment Ones.

Modulation of the membrane permeability through a decrease in porin-mediated antibiotic entry and/or an increase in antibiotic efflux is one of the resistance mechanisms to antibiotics evolved by Gram-negative bacteria. To assess whether the outer membrane porin OprD and Resistance-Nodulation-Division (RND) efflux pumps were similarly expressed in 33 ciprofloxacin-resistant clinical strains of Pseudomonas aeruginosa and in 30 non-clinical strains originating from the hospital environment (mainly waterborne Pseudomonas aeruginosa), the expression of oprD, mexB, mexF, and mexY genes was investigated. Overall, the expression of oprD was not detected by RT-qPCR in 14 (22%) strains and underexpressed in 35 (56%) more. No significant difference in oprD expression was detected between clinical and non-clinical strains. As for efflux pumps, 23 (70%) of the clinical strains overexpressed at least one of the tested RND genes. Overexpression of mexB, mexF and mexY was detected in 27, 12, and 45% of the clinical strains, respectively. In the 30 non-clinical strains, no overexpression could be found for mexB, mexF, or mexY. On the contrary, a global underexpression of the tested efflux pump genes was recorded. In both clinical and environmental strains, a positive correlation was found between the expressions of oprD and mexB. Similarly, the expressions of oprD and mexF were positively correlated. This result contrasts with the inverse correlation between both MexAB-OprM/MexEF-OprN and OprD previously described in carbapenem-resistant P. aeruginosa strains. The only positive correlation between phenotypic ciprofloxacin minimum inhibitory concentrations (MICs) and the expression of efflux pump gene was witnessed with mexY (analysis on pooled results for clinical and environmental strains). However, in clinical strains, no statistically significant link could be found between the degree of reduction in ciprofloxacin MICs witnessed with Phenylalanine-Arginine β-naphthylamide (PAβN) and the expression of any of the 3 RND genes tested.

Tetrahydropyridine derivative as efflux inhibitor in Mycobacterium abscessus.

This study aimed to evaluate a tetrahydropyridine derivative (THP) as a potential inhibitor of the efflux mechanism and modulator of the high level of antimicrobial resistance usually observed in members of the Mycobacterium abscessus (M. abscessus) group. The strain M. abscessus subsp. abscessus (ATCC 19997) was used as reference, in addition to three clinical isolates: M. abscessus subsp. abscessus (AT 07), and two M. abscessus subsp. bolletii (AT 46 and AT 52). The minimum inhibitory concentration (MIC) of amikacin (AMI), ciprofloxacin (CIP), clarithromycin (CLA), verapamil (VP), and THP derivative (NUNL02) was determined. The NUNL02 showed activity against M. abscessus; the MIC of AMI against ATCC 19997 was reduced more than 16-fold, and the MIC of CIP against AT 52 was reduced four-fold. When combined with CLA, the MIC was reduced against all tested strains. In addition, to detect and quantify the activity of the efflux mechanism, the intracellular accumulation kinetics of the fluorometric substrate ethidium bromide in the presence and absence of VP and NUNL02 were evaluated. The NUNL02 was found to be a more effective efflux inhibitor than VP, which is the classical inhibitor. The tetrahydropyridine derivative, NUNL02, is a promising adjuvant in the treatment of infections caused by M. abscessus.

Mutations in gyrA and parC Genes in Quinolone-Resistant Klebsiella pneumoniae Isolates from Borujerd Hospitals

Background & Objective: Quinolones are the antibiotics used to treat infections. Several reports have indicated the increased resistance to quinolone in Klebsiella pneumoniae strains all over the world. The aim of this study was to investigate amino acid substitutions in GyrA and ParC proteins among quinolone-resistant isolates of K. pneumoniae in Borujerd (west of Iran) hospitals. Materials & Methods: Totally, 100 isolates of K. pneumoniae were collected. After validating the isolates by conventional laboratory methods, an antimicrobial susceptibility test was carried out for some antibiotics from the quinolones family. Quinolone resistance and Minimum Inhibitory Concentration (MIC) of Ciprofloxacin were detected by disk diffusion and E-test methods, respectively. The amplification of gyrA and parC genes in quinolone-resistant strains was performed by PCR using specific primers. PCR products were sequenced in order to detect the mutations in gyrA and parC genes. Results: Generally, 38 of all the collected isolates were resistant to Nalidixic acid and Ciprofloxacin, 18 were resistant to Ofloxacin, and 15 were resistant to Norfloxacin. Concurrent resistance to Nalidixic acid, Ciprofloxacin, Ofloxacin, and Norfloxacin was determined in 15 of the cases. In 86 (n=20) of Ciprofloxacin-resistant strains, MIC was measured 128 µg/mL. The mutation rate was 40 (n=9) in gyrA gene in quinolone-resistant strains and 35 (n=8) in parC gene. Conclusion: Briefly, our research findings revealed that a relatively high resistance to quinolones as well as fluoroquinolone was observed among K. pneumoniae isolates in Brojurd hospitals. It is likely that mutation occurrence in certain positions of gyrA and parC genes has a significant effect on developing high-level resistance to quinolone in K. pneumoniae. © 2019, Zanjan University of Medical Sciences and Health Services. All rights reserved.

Effectiveness of selected broad spectrum antibiotics against Pseudomonas species isolated through the use of chloramphenicol

Greenish pigment producing Pseudomonas species were isolated from water samples using nutrient agar supplemented with 50 μg.ml-1 chloramphenicol. Broth cultures of three of the Pseudomonas isolates were prepared for minimum inhibitory concentration (MIC) determination by adjusting their turbidity using sterile normal saline to match the turbidity of McFarland standard No. 1 which is regarded to have a cell density of about 3 × 108 cfu/ml. The MIC of ciprofloxacin, erythromycin, and tetracycline against the three isolates was determined using the agar dilution method. The concentrations of the antibiotics used are 0.625, 1.25, 2.5, 5.0, 10.0, 20.0, 40.0, 80.0, 160.0, 320.0, and 640.0 μg/ml. The results showed that the MIC of ciprofloxacin against the Pseudomonas isolates ranged from 5 – 640 μg/ml; the MIC of tetracycline against the isolates ranged from 5 – 640 μg/ml; and the MIC of erythromycin against the isolates ranged from 40 - 80 μg/ml. It is thus concluded that multidrug resistant species of Pseudomonas can be generated as a result of using chloramphenicol for the isolation of Pseudomonas, and that erythromycin can be effective in treating infections caused by Pseudomonas species that are resistant to ciprofloxacin and tetracycline.

Physical properties and cytotoxicity of antimicrobial dental resin adhesives containing dimethacrylate oligomers of Ciprofloxacin and Metronidazole

ObjectiveAntimicrobial oligomers synthesized from ciprofloxacin (CF) and metronidazole (MN) were investigated for their potential use in dental adhesives. MethodsSusceptibility of the cariogenic bacterium Streptococcus mutans UA159 to CF, MN, and CF/MN combination was evaluated. Hydrolytic stability and drug release from the oligomers was studied in buffer and simulated human salivary esterase conditions. Cytotoxicity of films with 15wt% drug oligomers co-polymerized with commercial monomers were assessed using human gingival fibroblasts (HGFs). In-house adhesives were prepared and characterized for viscosity. Polymerized films were analysed for gel content and water swelling. Interfacial fracture toughness (KIC) of composites bonded to dentin by either a 2 or 3-step etch-and-rinse approach using the in-house formulated adhesives was measured. ResultsThe respective minimum inhibitory concentration for CF and MN against S. mutans was 0.7 and 2400μg/mL, with the combination having an additive effect (0.35μg/mL CF with 1200μg/mL MN). Antibiotics were released upon hydrolysis of the oligomers. Films containing the drug oligomers were not cytotoxic against HGFs. Replacing 2-hydroxyethyl methacrylate with the drug oligomers increased the viscosity of the experimental adhesives, reduced gel content, and decreased swelling of films in water. Antimicrobial adhesives demonstrated bonding to dentin with interfacial KIC values comparable to the in-house control in the 2-step application, and with slightly lower KIC values in the 3-step approach. SignificanceThe antimicrobial oligomers can be incorporated into dental adhesive systems using formulations that show comparable fracture toughness to commercial materials, and may provide a means to deliver local antimicrobial drug release at the marginal interface.