MICs Of Ciprofloxacin Research Articles

Assessment of phenotypic heterogeneity in Salmonella Typhimurium preadapted to ciprofloxacin and tetracycline.

Bacterial population exposed to stressful antibiotic conditions consists of various subpopulations such as tolerant, persister, and resistant cells. The aim of this study was to evaluate the phenotypic heterogeneity of Salmonella Typhimurium preadapted to sublethal concentrations of antibiotics. Salmonella Typhimurium cells were treated with 1/2×MIC of antibiotics for the first 48h and successively 1×MIC for the second 24h at 37°C, including untreated control (CON), no antibiotic and 1×MIC ciprofloxacin (NON-CIP), 1/2×MIC ciprofloxacin and 1×MIC ciprofloxacin (CIP-CIP), 1/2×MIC tetracycline and 1×MIC ciprofloxacin (TET-CIP), no antibiotic and 1×MIC tetracycline (NON-TET), 1/2×MIC ciprofloxacin and 1×MIC tetracycline (CIP-TET), and 1/2×MIC tetracycline and 1×MIC tetracycline (TET-TET). All treatments were evaluated by antibiotic susceptibility, ATP level, relative fitness, cross-resistance, and persistence. S. Typhimurium cells were more susceptible to non-adapted NON-CIP and NON-TET (>3-log reduction) than pre-adapted CIP-CIP, TET-CIP, CIP-TET, and TET-TET. CON exhibited the highest ATP level, corresponding to the viable cell number. The relative fitness levels were more than 0.95 for all treatments, except for NON-CIP (0.78). The resistance to ciprofloxacin and tetracycline was increased at all treatments with the exception of NON-TET. The persister cells were noticeably induced at CIP-TET treatment, showing more than 5 log CFU mL-1. The results suggest that the antibiotic preadaptation led to heterogeneous populations including persisters that can develop to resistance. This study provides new insight in the bacterial persistence associated with their potential risk and paves the way to design antibiotic therapy targeting dormant bacteria.

Reporting antimicrobial susceptibilities and phenotypes of resistance to vancomycin in vancomycin-resistant Enterococcus spp. clinical isolates: A nationwide proficiency study

IntroductionThe ability of Spanish microbiology laboratories to (a) determine antimicrobial susceptibility (AS), and (b) correctly detect the vancomycin resistance (VR) phenotype in vancomycin-resistant Enterococcus spp. (VRE) was evaluated. MethodsThree VRE isolates representing the VanA (E. faecium), VanB (E. faecium) and VanC (E. gallinarum) VR phenotypes were sent to 52 laboratories, which were asked for: (a) AS method used; (b) MICs of ampicillin, imipenem, vancomycin, teicoplanin, linezolid, daptomycin, ciprofloxacin, levofloxacin and quinupristin–dalfopristin, and high-level resistance to gentamicin and streptomycin; (c) VR phenotype. Results(a) The most frequently used system was MicroScan; (b) according to the system, the highest percentage of discrepant MICs was found with gradient strips (21.3%). By antimicrobial, the highest rates of discrepant MICs ranged 16.7% (imipenem) to 0.7% (linezolid). No discrepant MICs were obtained with daptomycin or levofloxacin. Mayor errors (MEs) occurred with linezolid (1.1%/EUCAST) and ciprofloxacin (5.0%/CLSI), and very major errors (VMEs) with vancomycin (27.1%/EUCAST and 33.3%/CLSI) and teicoplanin (5.7%/EUCAST and 2.3%/CLSI). For linezolid, ciprofloxacin, and vancomycin, discrepant MICs were responsible for these errors, while for teicoplanin, errors were due to a misassignment of the clinical category. An unacceptable high percentage of VMEs was obtained using gradient strips (14.8%), especially with vancomycin, teicoplanin and daptomycin; (c) 86.4% of the centers identified VanA and VanB phenotypes correctly, and 95.0% the VanC phenotype. ConclusionMost Spanish microbiology laboratories can reliably determine AS in VRE, but there is a significant percentage of inadequate interpretations (warning of false susceptibility) for teicoplanin in isolates with the VanB phenotype.

Oral ciprofloxacin activity against ceftriaxone-resistant Escherichia coli in an in vitro bladder infection model.

Pharmacodynamic profiling of oral ciprofloxacin dosing for urinary tract infections caused by ceftriaxone-resistant Escherichia coli isolates with ciprofloxacin MIC ≥ 0.25 mg/L. Urine-specific breakpoints for ciprofloxacin do not exist. However, high urinary concentrations may promote efficacy in isolates with low-level resistance. Ceftriaxone-resistant E. coli urinary isolates were screened for ciprofloxacin susceptibility. Fifteen representative strains were selected and tested using a dynamic bladder infection model. Oral ciprofloxacin dosing was simulated over 3 days (250 mg daily, 500 mg daily, 250 mg 12 hourly, 500 mg 12 hourly and 750 mg 12 hourly). The model was run for 96 h. Primary endpoint was change in bacterial density at 72 h. Secondary endpoints were follow-up change in bacterial density at 96 h and area-under-bacterial-kill-curve. Bacterial response was related to exposure (AUC0-24/MIC; Cmax/MIC). PTA was determined using Monte-Carlo simulation. Ninety-three clinical isolates demonstrated a trimodal ciprofloxacin MIC distribution (modal MICs at 0.016, 0.25 and 32 mg/L). Fifteen selected clinical isolates (ciprofloxacin MIC 0.25-512 mg/L) had a broad range of quinolone-resistance genes. Following ciprofloxacin exposure, E. coli ATCC 25922 (MIC 0.008 mg/L) was killed in all dosing experiments. Six isolates (MIC ≥ 16 mg/L) regrew in all experiments. Remaining isolates (MIC 0.25-8 mg/L) regrew variably after an initial period of killing, depending on simulated ciprofloxacin dose. A >95% PTA, using AUC0-24/MIC targets, supported 250 mg 12 hourly for susceptible isolates (MIC ≤ 0.25 mg/L). For isolates with MIC ≤ 1 mg/L, 750 mg 12 hourly promoted 3 log10 kill at the end of treatment (72 h), 1 log10 kill at follow-up (96 h) and 90% maximal activity (AUBKC0-96). Bladder infection modelling supports oral ciprofloxacin activity against E. coli with low-level resistance (ciprofloxacin MIC ≤ 1 mg/L) when using high dose therapy (750 mg 12 hourly).

High prevalence of qnrVC variants in Vibrio spp. isolated from food samples in South China

Phenotypic resistance to fluoroquinolones due to mutational changes in the gyrA and parC genes is common among clinical Vibrio strains; the plasmid-mediated quinolone resistance (PMQR) qnrVC genes were also suggested to play a role in enhancing resistance development. This study investigated the prevalence of qnrVC genes in foodborne Vibrio strains collected in Shenzhen, China, during the period August 2015 and April 2017. A total of 1811 foodborne Vibrio strains were collected, mostly (73.8%) from shrimp samples and 20.2% of these strains were resistant to ciprofloxacin. Investigation of resistance mechanisms showed that mutations in the gyrA and parC genes were commonly associated with ciprofloxacin resistance. The presence of qnrVC genes was shown to enhance ciprofloxacin MIC in Vibrio strains and 69.7% of Vibrio strains that harbored target mutations also carried qnrVC genes, yet only 27.5% of the isolates not harboring such mutations carried the qnrVC genes. A total of 141 strains were found to carry the qnrVC alleles, with qnrVC5 and qnrVC1 being the most common types. Fourteen qnrVC variant genes that contained novel mutations were detectable, with 12 (85.7%) involving qnrVC5-like alleles. For the first time, we found a variant that was likely formed by the recombination of qnrVC1 and qnrVC5. The genetic context of the qnrVC genes found in this study was highly variable, with most being accompanied by mobile genetic elements and other resistance genes. The increasing prevalence of qnrVC genes in Vibrio and its contribution on mediating the development of ciprofloxacin resistance need to be further investigated.

Enhancing activity of β-lactam and fluoroquinolones antibiotics by artemisinin and its derivatives against MDR Escherichia coli.

Artemisinin and its derivatives had played a biocidal role in biomedical remedies, while they were expected to enhance the activity of antibiotics against multiple drug-resistant (MDR) bacteria. The current study evaluated the interaction of artemisinin (ART), dihydroartemisinin (DHA), artesunate (AS), and artemisinic acid (AA) with β-lactam and fluoroquinolones antibiotics against Escherichia coli. Antibiotic strip test (E-test), Kirby Bauer's disc test (KB method), and broth microdilution method were adopted for susceptibility analysis, while the checkerboard method was applied to assess synergisms. ART, DHA, AS, and AA showed significantly enhanced antibacterial effects of β-lactam antibiotics against different strains of E. coli. The study showed ciprofloxacin to be most effective by presenting the least MIC (0.017125 ± 0.0022 μg/ml), while oxacillin was least effective (MIC 256 μg/ml) against E. coli. Synergism between AA and penicillin G (75%), ampicillin (25%), and oxacillin (50%) was observed in all isolates tested. AA and AS significantly decreased the MIC of ampicillin (-0.912 ± 0.908 μg/ml) and ciprofloxacin (-0.901 ± 0.893 g/ml), respectively. Artemisinin and its derivatives increased antibiotic accumulation within E. coli in a dose-dependent manner. The time-kill assay significantly reduced the bacterial number within 24 h of incubation. The study thus concludes greater room for improvement in enhancing the efficacy of antibiotics if used with artemisinin and its derivatives.

Synergistic Effect of Capparis Spinosa Fruits Extract in Comparison with Ciprofloxacin Against Resistant E. Coli O157:H7

This study was conducted to evaluate the synergistic effect between Capparis Spinosa fruits methanolic extract and ciprofloxacin against resistant E. Coli O157:H7, in varying concentration. This experiment was carried out through the ultrasonic alcoholic extraction of C. Spinosa fruits, and an extraction ratio of 24% was obtained. The extract showed pronounced concentration dependent antibacterial activity. The susceptibility study revealed that E. Coli O157:H7 was sensitive to C. Spinosa fruits. The findings of the present study indicate that the use of pronounced C. Spinosa fruits extract may have the perfect to be choice in clinical control. The concentration of C. spinosa fruits extract increase the activity of inhibition, increase as well when used in combination with ciprofloxacin (half concentration from each other). In result appeared synergism effect between plant extract and ciprofloxacin and may make bacteria lost their resistance to antibiotics by this synergism phenomenon. The result of MIC (6400 µg/ ml), MBC (12800 µg/ ml) and for C. spinose fruits extract while ciprofloxacin MIC (12.5 µg/ ml) and MBC (25 µg/ ml). MICs of CIP/ C. spinosa fruits extract combinations against E. coli O157:H7 isolate was 1.562/ 1600 μg/ml. Value of minimum bactericidal concentration (MBC) of the synergistic combinations (CIP/ C. spinosa fruits extract) was 3.124/ 3200 μg/ml. According to obtained results fractional inhibitory concentration (FIC) value of (CIP/ C. spinosa fruits extract 1.562/ 1600 μg/ml) was (0.375) less than 0.5 indicates synergistic effect of interaction.

Evaluation of Delafloxacin against a Burkholderia pseudomallei Efflux Mutant Panel.

ABSTRACTIn vitro activities of delafloxacin and ciprofloxacin were evaluated against Burkholderia pseudomallei mutants expressing or lacking defined resistance-nodulation-cell division (RND) efflux pumps using CLSI methodology at pHs of 5.8 and 7.2. Delafloxacin MIC values were as much as 8-fold lower at pH 5.8 than those at pH 7.2, while ciprofloxacin MICs increased as much as 8-fold. The data from this study suggest that compared to ciprofloxacin, delafloxacin may have improved efflux avoidance, notably at acidic pH. In contrast to ciprofloxacin, delafloxacin may thus retain its therapeutic potential, even in BpeEF-OprC efflux-pump-expressing B. pseudomallei strains that compromise the use of fluoroquinolones, such as ciprofloxacin.IMPORTANCE Resistance-nodulation-cell division (RND) efflux pumps play a major role in intrinsic and acquired antibiotic resistance in Burkholderia pseudomallei, and these pumps are its only known multidrug resistance determinants. Fluoroquinolones have performed poorly in clinical settings and are currently not recommended for treatment of B. pseudomallei infections. While the reasons for the poor clinical performance of this pathogen remain unclear, efflux may be partially responsible since fluoroquinolones like ciprofloxacin are prone to efflux by RND pumps, notably BpeEF-OprC. In vitro efficacy testing using a panel of efflux-proficient and efflux-deficient strains allows identification of fluoroquinolones that compared to ciprofloxacin are less prone to efflux.

Critically Important Antimicrobial Resistance Trends in Salmonella Derby and Salmonella Typhimurium Isolated from the Pork Production Chain in Brazil: A 16-Year Period.

Knowledge about antimicrobial resistance in Salmonella is relevant due to its importance in foodborne diseases. We gathered data obtained over 16 years in the southern Brazilian swine production chain to evaluate the temporal evolution of halo for carbapenem, and the MIC for third-generation cephalosporins, fluoroquinolone, and polymyxin in 278 Salmonella Derby and Typhimurium isolates. All antimicrobial resistance assays were performed in accordance with EUCAST. To assess the diameter halo, we used a mixed linear model, and to assess the MIC, an accelerated failure time model for interval-censored data using an exponential distribution was used. The linear predictor of the models comprised fixed effects for matrix, serovar, and the interaction between year, serovar, and matrix. The observed halo diameter has decreased for ertapenem, regardless of serovars and matrices, and for the serovar Typhimurium it has decreased for three carbapenems. The MIC for ciprofloxacin and cefotaxime increased over 16 years for Typhimurium, and for Derby (food) it decreased. We did not find evidence that the MIC for colistin, ceftazidime, ciprofloxacin (Derby), or cefotaxime (food Typhimurium and animal Derby) has changed over time. This work gave an overview of antimicrobial resistance evolution from an epidemiological point of view and observed that using this approach can increase the sensitivity and timeliness of antimicrobial resistance surveillance.

Prevalence of Plasmid-Mediated Quinolone Resistance (PMQRs) Determinants and Whole Genome Sequence Screening of PMQR-Producing E. coli Isolated from Men Undergoing a Transrectal Prostate Biopsy.

Fluoroquinolones (FQs) are recommended as prophylaxis for men undergoing transrectal prostate biopsy (TRUS-Bx). Recent studies suggest a significant share of FQ-resistant rectal flora in post-TRUST-Bx infections. Methods: 435 Enterobacterales isolates from 621 patients attending 12 urological departments in Poland were screened by PCR for PMQR genes. PMQR-positive isolates were tested for quinolone susceptibility and investigated by whole genome sequencing (WGS) methods. Results: In total, 32 (7.35%) E. coli strains with ciprofloxacin MIC in the range 0.125–32 mg/L harbored at least one PMQR gene. qnrS and qnrB were the most frequent genes detected in 16 and 12 isolates, respectively. WGS was performed for 28 of 32 PMQR-producing strains. A variety of serotypes and sequence types (STs) of E. coli was noticed. All strains carried at least one virulence gene. AMR genes that encoded resistance against different classes of antibiotics were identified. Additionally, five of 13 ciprofloxacin-susceptible E. coli had alterations in codon 83 of the GyrA subunits. Conclusion: This study provides information on the common presence of PMQRs among E. coli, which may explain the cause for development of post-TRUS-Bx infections. High numbers of virulence and antimicrobial resistance genes detected show a potential for analysed strains to develop infections.

Recent Sensitivity Pattern of Salmonella Typhi in a tertiary care Hospital

Salmonella typhi is the main cause of the enteric fever in Homo sapiens. The topic of the concern now a day is the emerging multidrug resistance. It causes the disease of intestinal tract known as enteric fever, while Salmonella paratyphi cause the paratyphoid fever. This infection is waterborne and foodborne. Approximately 12 – 33 million people suffered from the typhoid fever annually around the globe. Objective: The aim of the study was to evaluate the sensitivity patterns of Salmonella typhi and Salmonella paratyphi. It is a retrospective study, conducted at the Medicine Department of Sahara Medical College, Narowal and Rawalpindi Medical University, Rawalpindi. Methods: The blood sample of 306 patients visiting the teaching hospital of our institute were collected. The samples were tested to evaluate the antimicrobial sensitivity. The Kirby-Bauer disc diffusion method was used. The E-test was leveraged for obtaining MIC of ciprofloxacin, while agar dilution method was utilized for obtaining MIC of azithromycin. Results: The samples were collected from patients. Out of the 306 sample, 177 samples were of S. paratyphi and other 127 were of S. typhi. 56% sample showed the sensitivity to ciprofloxacin antibiotic, while 281 samples showed sensitivity to nalidixic antibody. According to the MIC criteria 94% sample isolate were susceptible to ciprofloxacin and 46% to azithromycin. While 31% sample were resistant to it. 90% of the samples were susceptible to ampicillin while other 95% to trimoxazole. Conclusion: The co-trimoxazole and ampicillin care highly suggested for the management of the enteric fever. Ciprofloxacin resistance cannot be accurately measured by Nalidixic acid resistance screening. The samples also showcased emerging resistance against azithromycin.

Characteristics of Klebsiella Pneumonia St4 Coharboring Qnrb1, Aac-Ib-Cr, CTX-M-15 and SHV 11 in A Tunisian Hospital

Background: Multiresistant Klebsiella pneumonia are predominant cause of hospital acquired infection. This work describes the molecular epidemiology of these isolates in Tunisian Hospital. Methods: Between October 2010 and June 2013, 50 non-duplicated clinical K.pneumoniae were selected based on nalidixic acid (NA) resistance and were characterized. Isolates were identified using APi 20E system. Susceptibility testing was determined using the disc diffusion method and the micro dilution technique to determine the MIC of ciprofloxacin. PMQR and ESBL genes were detected by PCR and positive results were confirmed by direct sequencing of PCR products. Multilocus sequence typing (MLST) was performed to determine the genetic relationship among isolates. Conjugation and transformation were done to know if PMQR and ESBL were carried with one or two plasmids. Results: 20 PMQR harboring K.pneumoniae representing 40% of all NA resistant isolates were characterized. Among PMQR positive K.pneumoniae 13 were resistant to amoxicillin, amoxicillin/clavulanic acid, ticarcilline, piperacillin, cefaloridine, cefotaxime (CTX) and ceftazidime. The rate of resistance to gentamicin, tobramycin and amikacin were 85%, 95% and 25% respectively. Out of 20 K.pneumoniae (60%) were qnr positive (1 qnrA6 and 11 qnrB1) and (60%) were aac-Ib-cr positive. 33.3% harbored the aac-Ib-cr and qnrB1 determinants. Out of all PMQR positive strains, 65% harbored ctx-M-15 gene. It was associated to shv11 in three cases and tem1 in two cases. The predominant types were ST4 (35%) and ST15 (20%). ST 101(15%) and ST 147 (10%) come in second order. one case of each ST14,ST86,ST336 and ST307 were also observed. qnrB1, aac-Ib-cr, Ctx-m-15 can be carried with more than one plasmid in the same bacteria. Conclusion: The co-existing of different genes conferring resistance among the same and different family of antibiotics is a big threat to patient because it limits the therapeutic process. This phenomenon is a problem of concern that needs to improve the resistance surveillance of multi gene carrying K pneumonia.

The expression of type II TA system genes following persister cell formation in Pseudomonas aeruginosa isolates in the exponential and stationary phases.

Failure of infection therapy in the presence of antibiotics has become a major problem which has been mostly attributed to the ability of bacterial persister cell formation. Bacteria use various mechanisms to form persister cells in different phases, among which is the toxin-antitoxin (TA) systems. This study aimed at investigating the expression of type II TA system genes under the stress of ciprofloxacin and colistin antibiotics in the exponential and stationary phases. To determine the effects of ciprofloxacin and colistin on persister cell formation in the exponential and stationary phases of Pseudomonas aeruginosa strains, colony counting was performed at different time intervals in the presence of fivefold MIC of ciprofloxacin and colistin. In addition, the expression of relBE, Xre-COG5654, vapBC, and Xre-GNAT genes in P. aeruginosa isolates was assessed 3.5h after antibiotic treatment in the exponential and stationary phases using qRT-PCR. Our results indicated the presence of persister phenotype of P. aeruginosa strains in the presence of fivefold MIC of ciprofloxacin and colistin compared to the control after 3.5h of incubation in the exponential and stationary phases. Also, the number of persister cells in the stationary phase was higher than that of the exponential phase. According to the results of qRT-PCR, ciprofloxacin and colistin may induce persister cells by increasing the expression of type II TA systems in stationary and exponential phases. Ciprofloxacin and colistin may increase the formation of persister cells by affecting the expression of type II TA systems.

Evaluation of the effect of ibuprofen in combination with ciprofloxacin on the virulence-associated traits, and efflux pump genes of Pseudomonas aeruginosa.

Biofilm formation and antibiotic efflux are two determinant factors in the development of drug resistance phenotype by Pseudomonas aeruginosa. Non-steroid anti-inflammatory drugs have shown the antimicrobial potential to be used in combination with antibiotics against bacterial pathogens. In this work, the effect of ibuprofen alone and in combination with ciprofloxacin on some virulence traits and the expression of the alginate synthesis and efflux pump genes of clinical isolates of P. aeruginosa was investigated. The checkerboard titration assay was used to evaluate the synergism of the drugs. P. aeruginosa strains were grown in the presence of sub-inhibitory concentrations of the drug and their biofilm formation level, swarming, swimming, and hemolytic activity were assessed. Also, the relative expression of the alg44, algT/U, mexB, and oprM genes was determined by qPCR assay. The MIC of ibuprofen and ciprofloxacin were measured 2048 and 32µg/mL and the drugs showed synergic antibacterial activity (FIC = 0.4). Moreover, ibuprofen alone and in combination with ciprofloxacin, significantly reduced the expression of alg44 (0.22 and 0.25 folds) and algT/U (0.26 and 0.37 folds) genes, while increased the expression of the mexB (1.64 and 1.83 folds) and oprM (1.36 and 1.92 folds) genes. Simultaneous treatment of bacterial cells with ibuprofen and ciprofloxacin significantly decreased bacterial biofilm formation (65%), swimming, swarming, and hemolytic activity (85%), compared with the control. This work suggests that ibuprofen has considerable anti-virulence potential against P. aeruginosa and could be employed for combination therapy with antibiotics after further characterizations.

Antimicrobial susceptibility testing and molecular characterization of Neisseria gonorrhoeae in Tehran, Iran.

Gonorrhea is a sexually transmitted infection occurring worldwide. Antimicrobial resistance (AMR) surveillance in Neisseria gonorrhoeae and associated molecular epidemiological studies are crucial to ascertain the spread of antibiotic-resistant and developing the local treatment guidelines. This study was performed to determine the antimicrobial susceptibility testing (AST) and molecular epidemiology of N. gonorrhoeae isolates in Tehran, Iran. During 1 July 2018-30 July 2020, a total of 500 urogenital (468 endocervical, 32 urethral) swabs were collected from patients with signs and symptoms of genitourinary infections presenting to two women's hospitals and one health center located center and south of Tehran. Specimens were cultured and examined for the presence of N. gonorrhoeae isolates by biochemical tests. MIC Test Strip determined the MICs of ceftriaxone, azithromycin, and ciprofloxacin. Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) was also performed. A total of 38N. gonorrhoeae isolates were identified. The proportions of resistant N. gonorrhoeae isolates were as follows: ceftriaxone (MIC ≥0.125μg/mL) 10.5% (4/38), azithromycin (MIC >1μg/mL) 34% (13/38), and ciprofloxacin (MIC ≥1μg/mL) 31.5% (12/38). In total, 25 different NG-MAST STs were identified. The STs comprised 1-4 isolates each, and the predominant ST was ST266 (n = 4). Our study demonstrates a diverse gonococcal population with high rates of resistance to azithromycin and evidence of resistance to ceftriaxone. The results have potential implications for antibiotic choice for the gonococcal treatment and highlight the need to broaden gonococcal AMR monitoring in Iran.

Urea-Based Ligand as an Efflux Pump Inhibitor: Warhead to Counter Ciprofloxacin Resistance and Inhibit Collagen Adhesion by MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) is a frontline human pathogen in which efflux pump activity confers high levels of antibiotic-resistance and poses a therapeutic challenge in the clinics. The present study illustrates the potential of urea-based ligand as an efflux pump inhibitor (EPI) in order to restore the efficacy of ciprofloxacin (CPX) against MRSA. Among eight structurally varying urea-based ligands, the ligand C8 could significantly inhibit efflux pump activity in the clinical MRSA strain S. aureus 4s and was superior to the known EPI reserpine. In combinatorial treatment, C8 enhanced cellular accumulation of CPX, rendered a 16× decrease in the MIC of CPX, and restored the susceptibility of S. aureus 4s to CPX. Notably, C8 downregulated the expression of norA gene coding for the efflux pump in MRSA and treatment with 10 μM C8 and 2.0 μM CPX prevented emergence of the CPX resistance trait and suppressed MRSA cell growth till 120 generations. For potential anti-MRSA therapy, C8-loaded poly(d,l-lactide-co-glycolide) nanocarrier (C8-PNC) was generated, which facilitated facile release of C8 in physiologically relevant fluid. C8-PNC (loaded with 50 μM C8) rendered efflux pump inhibition and eliminated MRSA in combination with only 2.0 μM CPX. Treatment with the non-toxic C8-PNC (loaded with 50 μM C8) and CPX (2.0 μM) also hindered MRSA adhesion on collagen manifold higher as compared to cells treated with 32 μM CPX and significantly downregulated norA gene expression in non-adhered MRSA cells. The urea-based ligand presented herein is a promising biocompatible therapeutic material for effective mitigation of MRSA infections.

Draft Genome Sequences of Sixteen Fluoroquinolone-Resistant Extraintestinal Escherichia coli Isolates from Human Patients.

ABSTRACTWe report here the draft genome sequences of 16 fluoroquinolone-resistant extraintestinal Escherichia coli isolates from human patients. These isolates had high MICs (32 to 256 μg/mL) for ciprofloxacin and contained point mutations in the quinolone resistance-determining region (QRDR) of both gyrA and parC that confer resistance to fluoroquinolone. The whole-genome sequence data provide a better understanding of the fluoroquinolone resistance mechanisms in these isolates and would be beneficial in source tracking these pathogens during pandemic outbreaks.

Plasmid-Mediated Quinolone Resistance (PMQR) in Two Clinical Strains of Salmonella enterica Serovar Corvallis.

Non-typhoid serovars of Salmonella enterica are one of the main causes of bacterial food-borne infections worldwide. For the treatment of severe cases of salmonellosis in adults, fluoroquinolones are amongst the drugs of choice. They are categorized by the World Health Organization (WHO) as “critically important with highest priority in human medicine”. In the present study, two clinical S. enterica serovar Corvallis isolates (HUA 5/18 and HUA 6/18) from a Spanish hospital, selected on the basis of fluoroquinolone resistance, were characterized. The MICs of ciprofloxacin, determined by E-test, were 0.5 and 0.75 µg/mL for HUA 5/18 and HUA 6/18, respectively, and both were also resistant to pefloxacin but susceptible to nalidixic acid. Whole genome sequencing (WGS) of the isolates was performed with Illumina platform, and different bioinformatics tools were used for sequence analysis. The two isolates belonged to ST1541, and had the Thr57Ser substitution in the ParC protein which is also found in ciprofloxacin susceptible isolates. However, they harbored identical ColE plasmids of 10 kb carrying the qnrS1 gene. In these plasmids, the gene was flanked by defective versions of IS2-like and ISKra4-like insertion sequences. HUA 5/18 and HUA 6/18 were also phenotypically resistant to streptomycin, sulfonamides and tetracycline, with the responsible genes: strA, strB, sul2 and tet(A) genes, being located on a IncQ1 plasmid. ColE plasmids with the qnrS1 gene are widely spread among multiple serovars of S. enterica from different samples and countries. These mobilizable plasmids are playing an important role in the worldwide spread of qnrS1. Thus, their detection in hospitals is a cause of concern which deserves further attention.

A novel parC mutation potentiating fluoroquinolone resistance in Klebsiella pneumoniae and Escherichia coli clinical isolates.

Resistance to fluoroquinolones is mainly due to point mutations that gave rise to amino acid substitutions in the quinolone resistance-determining regions of either gyrA or parC genes, which may be augmented by plasmid mediated resistance. Accordingly, the main aim of the study was to investigate the mutations in gyrA and parC genes as well as the qnrA and qnrB genes acquisition. 193 Klebsiella pneumoniae and Escherichia coli isolates were collected, identified and MICs for ciprofloxacin, levofloxacin and moxifloxacin were determined. Polymerase Chain Reaction to investigate qnrA, qnrB, gyrA and parC genes followed by DNA sequencing analysis to identify mutations in gyrA and parC genes. The most prominent mutation in gyrA gene was ser83leu, followed by asp87asn, and lys154arg. Regarding parC mutations, ser80ile was the most detected. Other mutations val141ala and glu84ala were also noted. In addition to a substitution mutation at codon 157 of leucine to tyrosin. To the best of our knowledge this mutation was not previously reported. qnrB was the most detected gene, as 64.7% Klebsiella pneumoniae and 57.1% Escherichia coli were positive. qnrA gene was detected in 11% Klebsiella pneumoniae and 4% of Escherichia coli isolates tested. This study suggests that the indiscriminate use of fluoroquinolones resulted in the increase of development of resistance either through mutations in the quinolone resistance-determining regions of either gyrA or parC genes augmented by plasmid mediated resistance. The irrational use of new fluoroquinolones such as moxifloxacin has created selective pressure for the appearance of new mutation.

Elucidation of resistance acquisition between various genera of gram-negative bacteria

The antimicrobial agents have the potential to maintain the selective pressure on bacteria. Bacteria can alter various mechanisms for survival under selective pressure. Thus, the bacteria acquire resistance through conjugation from co-existing bacteria during antimicrobial stress. The study was designed experimentally to investigate the acquired resistance on the basis of time against different genera of gram-negative bacteria. The study was conducted at the Department of Pathology, King Edward Medical University, Mayo Hospital, Lahore, Pakistan. E coli strain was sensitive to Ciprofloxacin and Pseudomonas aeruginosa strain was resistant to Ciprofloxacin. The macro broth dilution technique was used to verify the susceptibility of E. coli and P. aeruginosa. 0.5 MacFarland standard solution of E. coli and P. aeruginosa were mixed and kept at the sub-minimal inhibitory concentration (0.781 µg/ml) of Ciprofloxacin for 28 days. MIC of Ciprofloxacin was measured against E. coli at weekly basis. It was observed that the Ciprofloxacin MIC against E. coli after 7, 14, 21 and 28 days were <01 µg/ml, <01 µg/ml, <04 µg/ml and <25 µg/ml respectively. In conclusion, E. coli acquires resistance from P. aeruginosa under selective pressure of sub-minimal concentration of antibiotic Ciprofloxacin in 28 days.

Helicobacter canis: A Review of Microbiological and Clinical Features.

Helicobacter canis, an enterohepatic Helicobacter, has proven its role in human diseases and has been rediscussed in recent years as its zoonotic potential is increasingly described. Routine microbiological detection of this pathogen is a difficult task as its culture may fail due to fastidious growth. It is therefore supposed that many clinical laboratories under-recognize H. canis infections. A review of all clinical and microbiological literature currently available from previous relevant H. canis human clinical cases, mainly bacteremia, added with a clinical case observed at the Cliniques universitaires Saint-Luc, was performed. Clinical features of H. canis reports show the presence of underlying clinical conditions in 89% of the cases, bacteremia in 83%, associated fever in 58%, and recent close contact with pets in 83%, especially dogs. The observed microbiological trends from 10 cases of bacteremia were a median of 4 days until positive blood culture bottle detection, subcultures showing a thin layer of small colonies under microaerophilic atmosphere at 35–42°C after 3–4 days of growth, and an identification requiring 16S rRNA sequencing given the difficulties observed with MALDI-TOF MS. Low MICs were observed for penicillins, amoxicillin/clavulanic acid, carbapenems, and metronidazole in opposition to high MICs for ciprofloxacin. A frequent association of H. canis and bacteremia in immunocompromised patients with recurrent fever in contact with pets, especially dogs, was identified. Considering the fastidious growing capacities, final identification from blood cultures may not be expected before 7 days. Intravenous ceftriaxone, oral doxycycline, or metronidazole has been suggested as efficient therapeutic choices.