High prevalence of plasmid-mediated quinolone resistance in escherichia coli strains producing extended-spectrum beta-lactamases isolated from faeces and urine of pregnant women with acute cystitis

BACKGROUND

Escherichia coli is the most common etiological agent of urinary tract infections (UTIs). Meanwhile, plasmid-mediated quinolone resistance (PMQR) is reported in E. coli isolates producing extended-spectrum β-lactamases (ESBLs). Furthermore, the reservoirs and mechanisms of acquisition of uropathogenic Escherichia coli (UPEC) strains are poorly understood. On the other hand, UTIs are common in pregnant women and the treatment challenge is alarming.

METHODS AND RESULTS

In the present study, 54 pregnant women with acute cystitis were included. A total of 108 E. coli isolates, 54 isolates from UTI and 54 isolates from faeces of pregnant women (same host) were collected. In the antimicrobial susceptibility test, the highest rate of antibiotic resistance was to nalidixic acid (77%, 83/108) and the lowest rate was to imipenem (9%, 10/108). Among the isolates, 44% (48/108) were ESBLs producers. A high frequency of PMQR genes was observed in the isolates. The frequency of PMQR genes qnrS, qnrB, aac(6')-Ib-cr, and qnrA was 58% (63/108), 21% (23/108), 9% (10/108), and 4% (4/108), respectively. Meanwhile, PMQR genes were not detected in 24% (20/85) of isolates resistant to nalidixic acid and/or fluoroquinolone, indicating that other mechanisms, i.e. chromosomal mutations, are involved in resistance to quinolones, which were not detected in the present study. In ESBL-producing isolates, the frequency of PMQR genes was higher than that of non-ESBL-producing isolates (81% vs. 53%). Meanwhile, UTI and faeces isolates mainly belonged to phylogenetic group B2 (36/54, 67% and 25/54, 46%, respectively) compared to other phylogenetic groups. In addition, virulence factors and multidrug-resistant (MDR) were mainly associated with phylogenetic group B2. However, predominant clones in faeces were not found in UTIs. Rep-PCR revealed the presence of 85 clones in patients. Among the clones, 40 clones were detected only in faeces (faeces-only), 35 clones only in UTI (UTI-only) and 10 clones in both faeces and UTI (faeces-UTI). We found that out of 10 faeces-UTI clones, 5 clones were present in the host's faeces flora.

CONCLUSION

This study revealed a high rate of resistance to the quinolone nalidixic acid and a widespread distribution of PMQR genes in MDR E. coli strains producing ESBLs. The strains represented virulence factors and phylogenetic group B2 are closely associated with abundance in UTI and faeces. However, the predominant clones in faeces were not found in UTIs and it is possible that rep-PCR is not sufficiently discriminating clones.

Typhoidal salmonella disease in Mukuru informal settlement, Nairobi Kenya; carriage, diversity, and antimicrobial resistant genes

INTRODUCTION

Multiple studies have shown that typhoid fever is endemic in developing countries characterized by poor hygiene. A unique way of Salmonella Typhi (S.Typhi) pathogenicity is establishing a persistent, usually asymptomatic carrier state in some infected individuals who excrete large numbers of bacteria in faeces. This study aimed to determine the isolation rate of S.Typhi from blood and stool samples among cases and asymptomatic individuals in the Mukuru informal settlement and identify antibiotic resistance patterns within the same population.

MATERIALS AND METHODS

We recruited 1014 outpatient participants presenting with typhoid-like symptoms in selected health centres in Nairobi, Kenya. Bacterial isolation was done on Xylose Lysine Deoxycholate agar (XLD) and Mac Conkey agar (Oxoid), followed by standard biochemical tests. Identification was done using API20E, and S.Typhi was confirmed by serotyping using polyvalent antisera 0-9 and monovalent antisera d. The Kirby-Bauer disc diffusion method was used to test the antimicrobial susceptibility of S.Typhi isolates, while Multi-Drug Resistant (MDR) strains were characterized using conventional PCR.

RESULTS

Of 1014 participants, 54 (5%) tested positive for S.Typhi. Thirty-eight (70%) of the S.Typhi isolated were from stool samples, while sixteen (30%) were from blood. Three (0.2%) of the isolates were from asymptomatic carriers. Of the 54 S.Typhi isolates, 20 (37%) were MDR. Resistance to ciprofloxacin and nalidixic acid was 43% and 52%, respectively. Resistance to amoxicillin-clavulanic acid (a beta-lactam inhibitor) was 2%. The BlaTEM-1 gene was present in 19/20 (95%) MDR isolates.

CONCLUSION

MDR S.Typhi is prevalent in Mukuru Informal settlement. The sharp increase in nalidixic acid resistance is an indication of reduced susceptibility to fluoroquinolones, which are currently the recommended drugs for the treatment of typhoid fever. This study highlights the need for effective antimicrobial stewardship and routine surveillance of antimicrobial resistance (AMR) to inform policy on the prevention and control of MDR Typhoid disease.

[Molecular mechanisms of quinolone resistance in non-typhoidal Salmonella]

By conducting retrospective analysis, this study aim to investigate the resistance mechanism of quinolones in non-typhoidal Salmonella (NTS). A total of 105 strains of NTS isolated from clinical specimens from the Fifth Affiliated Hospital of Southern Medical University from May 2020 to February 2021 were used as research objects. VITEK2 Compact automatic identification drug sensitivity analysis system and serological test were used to identify the strains. The sensitivity of the strains to ciprofloxacin, levofloxacin and nalidixic acid was detected by AGAR dilution method. The whole genome of 105 strains of NTS was sequenced. Abricate and other softwares were used to analyze drug-resistant genes, including plasmid-mediated quinolone resistance gene (PMQR) and Quinolone resistance determination region (QRDR). Serotypes and ST types were analyzed using SISTR and MLST, and phylogenetic trees were constructed. The results showed that the NTS isolated in this region were mainly ST34 Salmonella typhimurium (53.3%). The drug sensitivity results showed that the drug resistance rates of NTS to ciprofloxacin, levofloxacin and nalidixic acid were 30.4%, 1.9% and 22.0%, respectively, and the intermediate rates of ciprofloxacin and levofloxacin were 27.6% and 54.2%.A total of 46 (74.2%) of the 62 quinolone non-susceptible strains carried the PMQR gene, mainly qnrS1 (80.4%), followed by aac(6')-Ib-cr(15.2%); there were 14 NTS and 8 NTS had gyrA and parC gene mutations, respectively. The gyrA was mutations at the amino acid position 87, Asp87Tyr, Asp87Asn, Asp87Gly, and Thr57Ser mutations were detected in parC. In conclusion, this study found that NTS had relatively high resistance to quinolones, carrying qnrS1 gene mainly resulted in decreased sensitivity of NTS to ciprofloxacin and levofloxacin, and gyrA:87 mutation mainly resulted in NTS resistance to Nalidixic acid; Salmonella typhimurium in clinical isolates showed clonal transmission and required further epidemiological surveillance.

Pathogenicity assessment of Arcobacter butzleri isolated from Canadian agricultural surface water

BACKGROUND

Water is considered a source for the transmission of Arcobacter species to both humans and animals. This study was conducted to assess the prevalence, distribution, and pathogenicity of A. butzleri strains, which can potentially pose health risks to humans and animals. Cultures were isolated from surface waters of a mixed-use but predominately agricultural watershed in eastern Ontario, Canada. The detection of antimicrobial resistance (AMR) and virulence-associated genes (VAGs), as well as enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) assays were performed on 913 A. butzleri strains isolated from 11 agricultural sampling sites.

RESULTS

All strains were resistant to one or more antimicrobial agents, with a high rate of resistance to clindamycin (99%) and chloramphenicol (77%), followed by azithromycin (48%) and nalidixic acid (49%). However, isolates showed a significantly (p < 0.05) high rate of susceptibility to tetracycline (1%), gentamycin (2%), ciprofloxacin (4%), and erythromycin (5%). Of the eight VAGs tested, ciaB, mviN, tlyA, and pldA were detected at high frequency (> 85%) compared to irgA (25%), hecB (19%), hecA (15%), and cj1349 (12%) genes. Co-occurrence analysis showed A. butzleri strains resistant to clindamycin, chloramphenicol, nalidixic acid, and azithromycin were positive for ciaB, tlyA, mviN and pldA VAGs. ERIC-PCR fingerprint analysis revealed high genetic similarity among strains isolated from three sites, and the genotypes were significantly associated with AMR and VAGs results, which highlight their potential environmental ubiquity and potential as pathogenic.

CONCLUSIONS

The study results show that agricultural activities likely contribute to the contamination of A. butzleri in surface water. The findings underscore the importance of farm management practices in controlling the potential spread of A. butzleri and its associated health risks to humans and animals through contaminated water.

A Comparative Study on Antimicrobial Resistance in Escherichia coli Isolated from Channel Catfish and Related Freshwater Fish Species

Antimicrobial resistance (AMR) trends in 114 generic Escherichia coli isolated from channel catfish and related fish species were investigated in this study. Of these, 45 isolates were from commercial-sized channel catfish harvested from fishponds in Alabama, while 69 isolates were from Siluriformes products, accessed from the U.S. Department of Agriculture Food Safety and Inspection Service' (FSIS) National Antimicrobial Resistance Monitoring System (NARMS) program. Antibiotic susceptibility testing and whole genome sequencing were performed using the GenomeTrakr protocol. Upon analysis, the fishpond isolates showed resistance to ampicillin (44%), meropenem (7%) and azithromycin (4%). The FSIS NARMS isolates showed resistance to tetracycline (31.9%), chloramphenicol (20.3%), sulfisoxazole (17.4%), ampicillin (5.8%) and trimethoprim-sulfamethoxazole, nalidixic acid, amoxicillin-clavulanic acid, azithromycin and cefoxitin below 5% each. There was no correlation between genotypic and phenotypic resistance in the fishpond isolates, however, there was in NARMS isolates for folate pathway antagonists: Sulfisoxazole vs. sul1 and sul2 (p = 0.0042 and p < 0.0001, respectively) and trimethoprim-sulfamethoxazole vs. dfrA16 and sul1 (p = 0.0290 and p = 0.013, respectively). Furthermore, correlations were found for tetracyclines: Tetracycline vs. tet(A) and tet(B) (p < 0.0001 each), macrolides: Azithromycin vs. mph(E) and msr(E) (p = 0.0145 each), phenicols: Chloramphenicol vs. mdtM (p < 0.0001), quinolones: Nalidixic acid vs. gyrA_S83L=POINT (p = 0.0004), and β-lactams: Ampicillin vs. blaTEM-1 (p < 0.0001). Overall, we recorded differences in antimicrobial susceptibility testing profiles, phenotypic-genotypic concordance, and resistance to critically important antimicrobials, which may be a public health concern.

Transferable mechanisms of quinolone resistance are more frequent among enterotoxigenic Escherichia coli isolates displaying low-level quinolone resistance

This study analysed the mechanisms of quinolone resistance among enterotoxigenic Escherichia coli (ETEC) in a periurban area of Lima, Peru. The susceptibility to nalidixic acid and ciprofloxacin, the role of Phe-Arg-b-Naphtylamyde inhibitable-(PAbN) efflux pumps, the presence of mutations in gyrA and parC as well as the presence of aac(6')Ib-cr, qepA, qnrA, qnrB, qnrC, qnrD, qnrVC and oqxAB were determined in 31 ETEC from previous case/control studies of children's diarrhoea. Discordances between disk diffusion, with all isolates showing intermediate or fully resistance to nalidixic acid, and minimal inhibitory concentration (MIC), with 7 isolates being below considered resistance breakpoint, were observed. Twenty-one isolates possessed gyrA mutations (19 S83L, 2 S83A). AAC(6') Ib-cr, QnrS, QnrB and QepA were found in 7, 6, 2 and 1 isolates respectively, with 3 isolates presenting 2 transferable mechanisms of quinolone resistance (TMQR) concomitantly. TMQR were more frequent among isolates with MIC to nalidixic acid ranging from 2 to 16 mg/L (p=0.03), while gyrA mutations were more frequent among isolates with nalidixic acid MIC >= 128 mg/L (p=0.0002). In summary, the mechanisms of quinolone resistance present in ETEC isolates in Peru have been described. Differences in the prevalence of underlying mechanisms associated with final MIC levels were observed. The results suggest two different evolutive strategies to survive in the presence of quinolones related to specific bacterial genetic background.

The Effect of Quinolones on Common Duckweed Lemna minor L., a Hydrophyte Bioindicator of Environmental Pollution

Plant growth and the development of morphological traits in plants are inhibited under exposure to pharmaceuticals that are present in soil and water. The present study revealed that moxifloxacin (MOXI), nalidixic acid (NAL), levofloxacin (LVF) and pefloxacin (PEF) at concentrations of >0.29, >0.48, >0.62 and >1.45 mg × L^-1, respectively, inhibited the growth (Ir) of duckweed plants and decreased their yield (Iy). In the current study, none of the tested quinolones (QNs) at any of the examined concentrations were lethal for common duckweed plants. However, at the highest concentration (12.8 mg × L^-1), LVF increased Ir and Iy values by 82% on average and increased the values of NAL, PEF and MOXI by 62% on average. All tested QNs led to the loss of assimilation pigments. In consequence, all QNs, except for LVF, induced changes in chlorophyll fluorescence (Fv/Fm), without any effect on phaeophytinization quotient (PQ) values. The uptake of NAL, MOXI, LVF by Lemna minor during the 7-day chronic toxicity test was directly proportional to drug concentrations in the growth medium. Nalidixic acid was absorbed in the largest quantities, whereas in the group of fluoroquinolones (FQNs), MOXI, LVF and PEF were less effectively absorbed by common duckweed. This study demonstrated that biosorption by L. minor occurs regardless of the plants' condition. These findings indicate that L. minor can be used as an effective biological method to remove QNs from wastewater and water and that biosorption should be a mandatory process in conventional water and wastewater treatment.

Comparison of disk diffusion and broth microdilution methods for antimicrobial susceptibility testing of Campylobacter isolates of meat origin

The aim of this study was to compare the disk diffusion (DD) and the broth microdilution (BMD) methods in determining the antimicrobial susceptibility of 36 Campylobacter isolates of meat-origin to six antibacterial drugs (erythromycin, ciprofloxacin, tetracycline, streptomycin, gentamicin and nalidixic acid). All the available zone diameter and minimum inhibitory concentration (MIC) breakpoints of C. jejuni and C. coli as recommended by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) were utilized. In addition, the zone diameter breakpoints of Enterobacterales for nalidixic acid, gentamicin, and streptomycin, as recommended by the Clinical and Laboratory Standards Institute (CLSI), were applied. All Campylobacter isolates were categorised as susceptible to erythromycin and gentamicin by both methods indicating completely concordant classification results. The overall highest 'Very major error' (VME) and 'Major error' (ME) rates were detected for nalidixic acid (13.3%) and tetracycline (26.3%), respectively, whereas a 'Minor error' (mE) rate was detected only for ciprofloxacin (60.1%). However, the Cohen's kappa statistic indicated a substantial concordance between the DD and BMD classification results for tetracycline and streptomycin, and almost perfect agreement for nalidixic acid, with corresponding categorical agreement rates of over 86% and approximately up to 92%. The correlation between the complementary inhibition zones and MIC breakpoints was strong and statistically highly significant (p < 0.001) for ciprofloxacin, tetracycline, streptomycin, and nalidixic acid.

Lower Susceptibility to Fluoroquinolones and a gyrA Gene Mutation in Salmonella Typhi Isolates from Enteric Fever Patients

BACKGROUND

Enteric fever remains a major cause of morbidity and mortality in Nepal. The emergence of multi-drug resistant Salmonella is a challenge to the clinician to care for patients with enteric fever. This study assessed the antibiotic susceptibility of Salmonella Typhi isolated from enteric fever and the presence of gyrA? ?gene mutation at ser83 of S. Typhi.

METHODS

Blood samples (n = 834) from suspected enteric fever patients were collected and cultured to identify Salmonella Typhi. Antimicrobial sensitivity test was performed by the modified Kirby Bauer disc diffusion method. The minimum ?inhibitory concentration (MIC) tests for ofloxacin and ciprofloxacin were examined by the agar dilution method. The gyrA gene was amplified by PCR and restriction enzyme digestion was performed to evaluate the ser83 mutation.

RESULTS

Among 824 blood samples analyzed, 5.1% (42/824) were culture positive for S. Typhi. First-line antibiotics chloramphenicol and co-trimoxazole showed higher in-vitro efficacy compared to amoxicillin. Macrolides (azithromycin) and third-generation cephalosporins (ceftriaxone, cefixime, and cefotaxime) were highly effective against S. Typhi. Nalidixic acid resistance (NAR) was observed in 95.2% (40/42) isolates, among them, all (40/40) isolates harbored mutant gyrA gene at ser83. However, none of the nalidixic acid-sensitive Salmonella? isolates was positive for gyrA? mutation at ser83.

CONCLUSIONS

This study showed decreased susceptibility to fluoroquinolones and the presence of gyrA? mutation at ser83 position in majority of S. Typhi isolates which highlights the importance of alternate drugs as empirical therapy for the treatment of enteric fever patients. So, the clinician should focus on prescribing conventional first-line antibiotics for the treatment of typhoid patients after higher cohort and extended follow-up studies.

Antibiotic Resistance Profile and Multiple Antibiotic Resistance Index of Campylobacter Species Isolated from Poultry

Campylobacter is a major public health problem, leading to foodborne diarrhea in the world. The current study aimed to isolate Campylobacter in different sources of poultry and determine antimicrobial susceptibility. A total of 150 fecal and 29 cloacal swabs were obtained from poultry farms (84 cloacal swabs) and live bird markets (LBMs), respectively, and 37 cecal swabs were also acquired from a local slaughterhouse located in the middle Euphrates region. Campylobacter Species (spp.) was first isolated and characterized by conventional bacteriological methods. Secondly, the antimicrobial susceptibility of isolates was investigated by disc diffusion method. The overall prevalence of Campylobacter spp. isolated from fecal cloacal and cecal poultry samples was 24% (36 out of 150). All strains were resistant to Nalidixic acid and Ciprofloxacin (100%), with high resistance to Tetracycline (88.8%), Ampicillin (83.3%), Sulpha/Trimethoprim (80.5%), Erythromycin (50%), and Ceftriaxone (50%), but less resistant to Gentamicin (30.5%), Amoxi-Clav (27.7%), and Chloramphenicol (22.2%). The majority of isolates (97.2%) scored a multiple antibiotic resistance (MAR) index of 0.3 or more, and 35 (97.2%) isolates were resistant to three or more antibiotic classes. Particularly, 61.1% of the isolates were multidrug resistance (MDR), 36.1% of the isolates were extensively drug resistant, and 2.8% of the isolates were Pan drug resistant. Moreover, the current study detected 24 multiple resistance patterns from 36 isolates of Campylobacter spp., and most of the isolates (27 out of 36) displayed an important route of resistance to Nalidixic acid, Ciprofloxacin, and Tetracycline. Based on the results, increased resistance rates to commonly used antibiotics in Campylobacter were recovered from poultry farms, LBMs, and local slaughterhouses. The majority of strains were MDR to commonly used antimicrobials with elevated MAR indices, requiring implementation of a national strategy to improve husbandry practice and the effective use of antibacterial agents, alternatives, and vaccines.

The threat of persistent bacteria and fungi contamination in tuberculosis sputum cultures

Background

Tuberculosis (TB) sputum culture contaminants make it difficult to obtain pure TB isolates.We aimed to study and identify persistent TB sputum culture contaminants post the standard laboratory pre-culture sample decontamination techniques.

Methods

This was a longitudinal study of TB sputum culture contamination for a cohort of TB patients on standard treatment at: baseline, during TB treatment and post TB treatment. Sputum samples were decontaminated with 1.5%NaOH and neutralized using 6.8 Phosphate buffer solution.Sputum was then inoculated into MGIT (mycobactrial growth indicator tube) supplemented with 0.8ml PANTA. A drop of each positive MGIT culture was sub cultured onto blood agar and incubated for 48 hours at 35 -37OC.Any growth was identified using growth characteristics and colony morphology.

Results

From October 2017 through May 2019;we collected 8645 sputum samples of which 8624(99.8%) were eligible and inoculated into MGIT where 2444(28.3%)samples were TB culture positive and 255(10.4%)were positive for contaminants: 237 none-tuberculosis bacteria, 12 fungi and 6 mixed(none-tuberculous bacteria+fungi). There was no statistically significant difference between none tuberculosis bacteria and fungi in the treatment (OR=1.4,95%CI:0.26–7.47,p=0.690) and the post treatment TB phases(OR=2.02,95%CI:0.38–10.79,p=0.411)Vs baseline.

Conclusion

None-tuberculous bacteria and fungi dominate the plethora of TB sputum culture contamination and persist beyond the standard laboratory pre-culture decontamination algorithm.

Genome-Wide Identification and Expression Analysis of SOS Response Genes in Salmonella enterica Serovar Typhimurium

A bioinformatic search for LexA boxes, combined with transcriptomic detection of loci responsive to DNA damage, identified 48 members of the SOS regulon in the genome of Salmonella enterica serovar Typhimurium. Single cell analysis using fluorescent fusions revealed that heterogeneous expression is a common trait of SOS response genes, with formation of SOS^OFF and SOS^ON subpopulations. Phenotypic cell variants formed in the absence of external DNA damage show gene expression patterns that are mainly determined by the position and the heterology index of the LexA box. SOS induction upon DNA damage produces SOS^OFF and SOS^ON subpopulations that contain live and dead cells. The nature and concentration of the DNA damaging agent and the time of exposure are major factors that influence the population structure upon SOS induction. An analogy can thus be drawn between the SOS response and other bacterial stress responses that produce phenotypic cell variants.

Comparing treatment strategies to reduce antibiotic resistance in an in vitro epidemiological setting

The rapid rise of antibiotic resistance, combined with the increasing cost and difficulties to develop new antibiotics, calls for treatment strategies that enable more sustainable antibiotic use. The development of such strategies, however, is impeded by the lack of suitable experimental approaches that allow testing their effects under realistic epidemiological conditions. Here, we present an approach to compare the effect of alternative multidrug treatment strategies in vitro using a robotic liquid-handling platform. We use this framework to study resistance evolution and spread implementing epidemiological population dynamics for treatment, transmission, and patient admission and discharge, as may be observed in hospitals. We perform massively parallel experimental evolution over up to 40 d and complement this with a computational model to infer the underlying population-dynamical parameters. We find that in our study, combination therapy outperforms monotherapies, as well as cycling and mixing, in minimizing resistance evolution and maximizing uninfecteds, as long as there is no influx of double resistance into the focal treated community.

Genomic Background Governs Opposing Responses to Nalidixic Acid upon Megaplasmid Acquisition in Pseudomonas

Horizontal gene transfer is a significant driver of evolutionary dynamics across microbial populations. Although the benefits of the acquisition of new genetic material are often quite clear, experiments across systems have demonstrated that gene transfer events can cause significant phenotypic changes and entail fitness costs in a way that is dependent on the genomic and environmental context. Here, we test for the generality of one previously identified cost, sensitization of cells to the antibiotic nalidixic acid after acquisition of an ∼1-Mb megaplasmid, across Pseudomonas strains and species. Overall, we find that the presence of this megaplasmid sensitizes many different Pseudomonas strains to nalidixic acid but that this same horizontal gene transfer event increases resistance of Pseudomonas putida KT2440 to nalidixic acid across assays as well as to ciprofloxacin under competitive conditions. These phenotypic results are not easily explained away as secondary consequences of overall fitness effects and appear to occur independently of another cost associated with this megaplasmid, sensitization to higher temperatures. Lastly, we draw parallels between these reported results and the phenomenon of sign epistasis for de novo mutations and explore how context dependence of effects of plasmid acquisition could impact overall evolutionary dynamics and the evolution of antimicrobial resistance.IMPORTANCE Numerous studies have demonstrated that gene transfer events (e.g., plasmid acquisition) can entail a variety of costs that arise as by-products of the incorporation of foreign DNA into established physiological and genetic systems. These costs can be ameliorated through evolutionary time by the occurrence of compensatory mutations, which stabilize the presence of a horizontally transferred region within the genome but which also may skew future adaptive possibilities for these lineages. Here, we demonstrate another possible outcome, that phenotypic changes arising as a consequence of the same horizontal gene transfer (HGT) event are costly to some strains but may actually be beneficial in other genomic backgrounds under the right conditions. These results provide a new viewpoint for considering conditions that promote plasmid maintenance and highlight the influence of genomic and environmental contexts when considering amelioration of fitness costs after HGT events.

Customized optical mapping by CRISPR-Cas9 mediated DNA labeling with multiple sgRNAs

Whole-genome mapping technologies have been developed as a complementary tool to provide scaffolds for genome assembly and structural variation analysis (1,2). We recently introduced a novel DNA labeling strategy based on a CRISPR-Cas9 genome editing system, which can target any 20bp sequences. The labeling strategy is specifically useful in targeting repetitive sequences, and sequences not accessible to other labeling methods. In this report, we present customized mapping strategies that extend the applications of CRISPR-Cas9 DNA labeling. We first design a CRISPR-Cas9 labeling strategy to interrogate and differentiate the single allele differences in NGG protospacer adjacent motifs (PAM sequence). Combined with sequence motif labeling, we can pinpoint the single-base differences in highly conserved sequences. In the second strategy, we design mapping patterns across a genome by selecting sets of specific single-guide RNAs (sgRNAs) for labeling multiple loci of a genomic region or a whole genome. By developing and optimizing a single tube synthesis of multiple sgRNAs, we demonstrate the utility of CRISPR-Cas9 mapping with 162 sgRNAs targeting the 2Mb Haemophilus influenzae chromosome. These CRISPR-Cas9 mapping approaches could be particularly useful for applications in defining long-distance haplotypes and pinpointing the breakpoints in large structural variants in complex genomes and microbial mixtures.

Application of Amplon in combination with peroxyacetic acid for the reduction of nalidixic acid-resistant Salmonella Typhimurium and Salmonella Reading on skin-on, bone-in tom turkey drumsticks

Peroxyacetic acid (PAA) has become an important component of pathogen reduction in poultry processing, but there are potential concerns for continued exposure. The objective was to evaluate the effects of PAA and Amplon (AMP) used alone or in the combination. Bone-in tom turkey drumsticks (N = 100, n = 10, k = 5, 0 and 24 h) per study were obtained and inoculated with either nalidixic acid–resistant Salmonella Typhimurium or Salmonella Reading (64 μg/mL). The inocula were allowed to adhere to the drums at 4°C for 60 min for a final attachment of 10⁸ and 10⁷ cfu/g per S. Typhimurium and S. Reading, respectively. Drumsticks were treated with a no-treatment control; tap water, pH 8.5 (TW); TW+500 ppm PAA, pH 3.5 (PAA); TW+500 ppm AMP, pH 1.3 (AMP); TW + PAA + AMP (PAA + AMP). Treatments were applied as short duration dips (30 s) and allowed to drip for 2 min. After treatment, drums were stored at 4°C until microbial analyses at 0 and 24 h. Drums were rinsed in neutralizing buffered peptone water and spot plated for total aerobes and Salmonella. Bacterial counts were log₁₀ transformed and analyzed using n-way ANOVA. All treatments reduced S. Reading on turkey legs at both 0 and 24 h (P < 0.0001; P < 0.0001). At 24 h, drums treated with PAA + AMP (3.92 log₁₀ cfu/g) had less S. Reading than no-treatment control, TW, and AMP. Treatment by time interactions were observed for total aerobes among drums in both studies (P < 0.0001, P < 0.0001) and Salmonella among drums inoculated with S. Typhimurium (P < 0.0001). During the S. Reading and S. Typhimurium study, all treatments reduced Salmonella and total aerobes on drums. During the S. Typhimurium study, drums treated with PAA + AMP had the lowest numerical load of S. Typhimurium and total aerobes. The combination of AMP + PAA may exhibit a synergistic effect in reducing Salmonella on turkey drums, thus increasing the safety of turkey products for consumers.

Research Note: Effect of organic acid mixture on growth performance and Salmonella Typhimurium colonization in broiler chickens

Feed additives can be alternatives to antibiotics for routinely encountered pathogens in the poultry production. The objective of this study was to understand effects of organic acid mixture on growth parameters and Salmonella Typhimurium (ST) colonization in broilers. Organic acid mixture is a feed-grade buffered formic acid and sodium formate mixture (Amasil NA). A total of 800 1-day-old Cobb500 males were fed one of the five dietary treatments: a negative control diet without ST challenge (NC), positive control diet with ST challenge (PC), 0.3% organic acid mixture with ST, 0.6% organic acid mixture with ST, and 0.9% organic acid mixture with ST. Treatments were assigned to 20 pens with 40 chicks/pen and 4 replicates of each treatment. Chickens were challenged with 107 CFU/mL of nalidixic acid-resistant ST (STNAR) 4-D posthatch. In the grower phase, feed conversion rate was significantly reduced in the 9% organic acid mixture compared with the PC. The body weight and body weight gain (BWG) were not affected either in the starter or grower phases. However, in the finisher phase, the nonchallenged NC had higher BWG than the PC (P < 0.05), whereas there were no differences in BWG among the NC and organic acid mixture fed groups. In addition, there was a significant effect of organic acid mixture on the colonization of cecal STNAR. At 9 dpi, cecal STNAR was 3.28 log10 in the PC that was reduced to 2.65 log10 at 0.3%, 1.40 log10 at 0.6%, and 0.84 log10 in 0.9% organic acid mixture. At 24 dpi, cecal STNAR recovery was 0.81, 0.99, 0.53, and 0.33 log10 in the PC and 0.3, 0.6, and 0.9% organic acid mixture, respectively. Similarly, at 38 dpi, cecal STNAR was 0.26, 0.11, 0.33, and 0 log10 in the PC, 0.3, 0.6, and 0.9%, respectively. These results show that organic acid mixture can be one dietary strategy to control ST infection and maintain efficient growth performance.

Efficacy of peroxy acetic acid in reducing Salmonella and Campylobacter spp. populations on chicken breast fillets

Poultry processors use antimicrobials to reduce the risk of pathogens on poultry and poultry products. The efficacy of selective and nonselective plating media to enumerate injured Salmonella (selective media-brilliant green sulfa agar and Petrifilm Enterobacteriaceae Plate Count; nonselective media-tryptic soy agar and Petrifilm Aerobic Plate Count) and Campylobacter (selective medium-Campy cefex agar and nonselective medium-Brucella agar) populations and the efficacy of peroxy acetic acid (PAA) to reduce Salmonella and Campylobacter populations on chicken breast fillets were evaluated. All plating media for Salmonella and Campylobacter contained nalidixic acid (200 ppm) or gentamycin (200 ppm), respectively. Breast fillets were sprayed or immersed in PAA (500 ppm) for 10 min for evaluation of the plating media. Breast fillets inoculated with a mixed Salmonella and Campylobacter cocktail were sprayed (5 or 10 s) or immersed (4-30 s) in PAA (100, 400, 500, or 1,000 ppm) for evaluation of PAA efficacy. Salmonella populations were higher (P ≤ 0.05) when plated on nonselective media compared with the selective media for the non-PAA treated fillets, although the differences in populations were low (<0.32 log CFU/mL). For both the microorganisms, populations on PAA treated (immersion or spray) fillets were similar when enumerated on nonselective or selective media within each treatment (PAA immersion or spray). Both immersion and spray applications reduced (P ≤ 0.05) the Salmonella and Campylobacter populations compared with the control. Increasing the PAA concentration to 250, 500, and 1,000 ppm resulted in greater reductions (P ≤ 0.05) in Salmonella and Campylobacter populations. Immersion of the inoculated breast fillets in 1,000 ppm PAA solution for 30 s resulted in Salmonella and Campylobacter population reductions of 1.92 and 1.87 log CFU/mL, respectively. Method of antimicrobial application (immersion and spray) did not affect the reductions in Salmonella and Campylobacter populations. Either immersion or spray application can be used to improve microbial safety of chicken breast fillets in a poultry processing plant.

High occurrence of β-lactamase-producing Salmonella Heidelberg from poultry origin

Salmonella Heidelberg is commonly reported in foodborne outbreaks around the world, and chickens and poultry products are known as important source of these pathogen. Multidrug-resistant S. Heidelberg strains are disseminated into poultry production chair, which can lead to severe clinical infections in humans and of difficult to treat. This study aimed at evaluating the β-lactam susceptibility and genotypic relatedness of Salmonella Heidelberg at Brazilian poultry production chain. Sixty-two S. Heidelberg strains from poultry production chain (poultry, poultry meat and poultry farm) were used. All strains were evaluated to antimicrobial susceptibility by diffusion disk test, as well as β-lactam resistance genes. Genotypic relatedness was assessed by Pulsed-Field Gel Eletrophoresis, using Xba1 restriction enzyme. Forty-one strains were characterized as multidrug-resistant according to phenotype characterization. The resistance susceptibility revealed 31 distinct profiles, with higher prevalence of streptomycin (61/62), nalidixic acid (50/62), tetracycline (43/62) and β-lactam drugs (37/62). blaCMY-2 was the more frequent β-lactamase gene found (38/62); other resistance genes found were blaCTX-M (2/62), blaSHV (3/62) and blaTEM-1 (38/62). No carbapenemase genes was found. The Pulsed-Field Gel Electrophoresis showed 58 different profiles. Strains with a larger number of antimicrobial resistance were grouped into ten major clusters apart from others. The spread of resistance by ampC continues to rise, thereby turning concern to public health, since the β-lactam antimicrobials are used as a therapeutic treatment in humans.

Altered Growth and Envelope Properties of Polylysogens Containing Bacteriophage Lambda N-cI- Prophages

The bacterial virus lambda (λ) is a temperate bacteriophage that can lysogenize host Escherichia coli (E. coli) cells. Lysogeny requires λ repressor, the cI gene product, which shuts off transcription of the phage genome. The λ N protein, in contrast, is a transcriptional antiterminator, required for expression of the terminator-distal genes, and thus, λ N mutants are growth-defective. When E. coli is infected with a λ double mutant that is defective in both N and cI (i.e., λN^-cI^-), at high multiplicities of 50 or more, it forms polylysogens that contain 20–30 copies of the λN^-cI^- genome integrated in the E. coli chromosome. Early studies revealed that the polylysogens underwent “conversion” to long filamentous cells that form tiny colonies on agar. Here, we report a large set of altered biochemical properties associated with this conversion, documenting an overall degeneration of the bacterial envelope. These properties reverted back to those of nonlysogenic E. coli as the metastable polylysogen spontaneously lost the λN^-cI^- genomes, suggesting that conversion is a direct result of the multiple copies of the prophage. Preliminary attempts to identify lambda genes that may be responsible for conversion ruled out several candidates, implicating a potentially novel lambda function that awaits further studies.

The Occurrence of blaCTX-M-15 extended-spectrum β-lactamase Among Clinical Isolates of Klebsiella pneumoniae in Khorramabad, Iran

OBJECTIVE

During the recent decade, CTX-M-type enzymes, primarily CTX-M-15 extended- spectrum β-lactamase (ESBL) have strikingly developed throughout the world. The objective of this study was to investigate the frequency of CTX-M-type β-lactamases, as well as blaCTXM- 15 among Klebsiella pneumoniae isolates in Khorramabad, Iran.

METHODS

In this cross-sectional study, 60 isolates of K. pneumoniae were collected from selected teaching hospitals in Khorramabad, Iran. ESBLs producing isolates were identified using phenotypic double-disk synergy test. The presence of bla_CTX-M-types, as well as bla_CTX-M-15 gene, were investigated by PCR method.

RESULTS

While the highest resistance rates of isolates were found to nalidixic acid (65%) and trimethoprim/sulfamethoxazole (60%) antibiotics, the least resistance was to imipenem (15%). Moreover, 31(51.7%) isolates were resistant to at least three classes of antibiotics and designated as multidrug resistance (MDR). Fifty-two (86.7%) of 60 isolates were ESBLs positive. Thirty-five (58.3%) isolates harbored CTX-M-type β-lactamases, and also 29 (48.3%) isolates carried blaCTX-M-15.

CONCLUSIONS

This study presents the first report on the frequency of bla_CTX-M-15 in the west of Iran, so that our results showed ESBL of CTX-M-15 may partly account for hydrolyzing thirdgeneration cephalosporins.

Molecular Detection of gyrA Gene in Salmonella enterica serovar Typhi Isolated from Typhoid Patients in Baghdad

BACKGROUND AND OBJECTIVE

Typhoid fever is endemic in most countries, causing major public health problems with high morbidity and mortality, the resistance of Salmonella enterica serovar Typhi (S. Typhi) towards antimicrobials is recently increased. The aim was to detect the harboring gyrA gene in Typhi Salmonella enterica serovar.

MATERIALS AND METHODS

Twenty Salmonella enterica serovar Typhi isolates were obtained from the Teaching laboratories of the medical city in Baghdad, the isolates were obtained from blood specimens from typhoid patients. Colonies of Salmonella enterica serovar Typhi appeared on CHROM agar and Xylose Lysine Deoxycholate Agar (XLD) as light mauve to mauve-colored and as red with black center colonies, respectively. Polymerase Chain Reaction (PCR) technique was used to detect the presence of the gyrA gene within the twenty isolates with specific primer.

RESULTS

All twenty isolates show the highest resistance rates to Cefazolin 18 (90%), Ciprofloxacin 16 (80%), and Nalidixic acid 15 (75%), while it shows highest sensitivity rates to Cefepime 18 (90%) and Tobramycin 16 (80%) antibiotics. The MIC values show equal to or more than breakpoint of Nalidixic acid and Ciprofloxacin were 15 (75%) and 16 (80%) isolates, respectively.

CONCLUSION

PCR results showed the presence of gyrA gene (488 bp) in 14 (70%) of isolates (isolate number 1, 2, 3, 4, 7, 8, 9, 10, 12, 13, 14, 15, 18 and 19). On the other hand, 6(30%) isolates (isolate numbers 5, 6, 9, 11, 16, 17, and 20) don't harbor the gyrA gene.

Antimicrobial resistance genotypes and phenotypes of Campylobacter jejuni isolated in Italy from humans, birds from wild and urban habitats, and poultry

Campylobacter jejuni, a common foodborne zoonotic pathogen, causes gastroenteritis worldwide and is increasingly resistant to antibiotics. We aimed to investigate the antimicrobial resistance (AMR) genotypes of C. jejuni isolated from humans, poultry and birds from wild and urban Italian habitats to identify correlations between phenotypic and genotypic AMR in the isolates. Altogether, 644 C. jejuni isolates from humans (51), poultry (526) and wild- and urban-habitat birds (67) were analysed. The resistance phenotypes of the isolates were determined using the microdilution method with EUCAST breakpoints, and AMR-associated genes and single nucleotide polymorphisms were obtained from a publicly available database. Antimicrobial susceptibility testing showed that C. jejuni isolates from poultry and humans were highly resistant to ciprofloxacin (85.55% and 76.47%, respectively), nalidixic acid (75.48% and 74.51%, respectively) and tetracycline (67.87% and 49.02%, respectively). Fewer isolates from the wild- and urban-habitat birds were resistant to tetracycline (19.40%), fluoroquinolones (13.43%), and quinolone and streptomycin (10.45%). We retrieved seven AMR genes (tet (O), cmeA, cmeB, cmeC, cmeR, blaOXA-61 and blaOXA-184) and gyrA-associated point mutations. Two major B-lactam genes called blaOXA-61 and blaOXA-184 were prevalent at 62.93% and 82.08% in the poultry and the other bird groups, respectively. Strong correlations between genotypic and phenotypic resistance were found for fluoroquinolones and tetracycline. Compared with the farmed chickens, the incidence of AMR in the C. jejuni isolates from the other bird groups was low, confirming that the food-production birds are much more exposed to antimicrobials. The improper and overuse of antibiotics in the human population and in animal husbandry has resulted in an increase in antibiotic-resistant infections, particularly fluoroquinolone resistant ones. Better understanding of the AMR mechanisms in C. jejuni is necessary to develop new strategies for improving AMR programs and provide the most appropriate therapies to human and veterinary populations.

Characterizing Shigella species distribution and antimicrobial susceptibility to ciprofloxacin and nalidixic acid in Latin America between 2000-2015

BACKGROUND

Shigellosis is the second leading cause of diarrheal death globally. The global burden has been complicated by the emergence of Shigella strains resistant to first line antibiotic treatments such as ciprofloxacin. This study aims to describe the epidemiologic distribution of the most common Shigella species, and their antimicrobial susceptibility patterns to ciprofloxacin and nalidixic acid (NA) in Latin America.

METHODS

Laboratory data from 19 countries were obtained through the Latin American Network for Antimicrobial Resistance Surveillance (ReLAVRA) from 2000-2015. The Clinical Laboratory Standards Institute reduced susceptibility breakpoints for Enterobacteriaceae was used to interpret the disc diffusion tests for Shigella susceptibility to ciprofloxacin and NA. Negative binominal regression was used to analyze longitudinal trends of Shigella isolates antimicrobial susceptibility.

RESULTS

79,548 Shigella isolates were tested and reported between 2000-2015. The most common isolated species were S. flexneri (49%), and S. sonnei (28%). There was a steady increase in the proportion of S. sonnei isolates within the region(p<0.001). The average annual percentage increase (AAPI) in nonsusceptibility was 18.4% (p<0.001) for ciprofloxacin (baseline = 0.3); and 13.2%(p<0.001) for NA (baseline = 3). AAPI nonsusceptibility to ciprofloxacin was 13.3% for S. flexneri (p<0.04); and 39.9% for S. sonnei (p<0.001). Honduras, Dominican Republic, Venezuela, and Chile reported the highest increase in nonsusceptibility to ciprofloxacin among all Shigella isolates.

CONCLUSION

There is an increasing trend in Shigella nonsusceptibility to ciprofloxacin and NA, including among the most common shigella species, in Latin America. This rise of nonsusceptibility among Shigella species to commonly used treatments such as ciprofloxacin is alarming and threatens the control and management of this currently treatable infection. Improved data quality, collection and reporting is needed in Latin America to respond effectively to the rising trends observed. This includes the need for quality isolate level epidemiological data; molecular data, and data on antibiotic consumption and use.

Influence of nalidixic acid on tandem heterotrophic-autotrophic kinetics in a "NIPHO" activated sludge reactor

This work analyzes the effect of nalidixic acid (NAL) on the kinetics of the heterotrophic and autotrophic biomass growth within a "NIPHO" activated sludge reactor treating municipal wastewater. Thus, the effect of this chemical in the degradation rates of carbon and nitrogen sources and net biomass growth rate is evaluated. Activated sludge samples were taken at three different operation conditions, changing the values of hydraulic retention time (2.8-3.8 h), biomass concentration (1400-1700 mgVSS L^-1), temperature (12.6-14.8 °C), and sludge retention time (11.0-12.6 day). A respirometric method was applied to model the kinetic performance of heterotrophic and autotrophic biomass in absence and presence of NAL, and a multivariable statistical analysis was carried out to characterize the influence of the operation variables on the kinetic response of the system, which was finally optimized. The results showed that there was no inhibitory effect of NAL on heterotrophic biomass, with an increase of net heterotrophic biomass growth rate from 1.70 to 6.73 mgVSS L^-1 h^-1 at the most favorable period. By contrast, the autotrophic biomass was negatively affected by NAL, reducing the value of net autotrophic biomass growth rate from 25.37 to 10.29 mgVSS L^-1 h^-1 at the best operation conditions. In general, biomass concentration and temperature had the highest influence on the degradation rate of carbon and nitrogen sources, whereas hydraulic retention time and sludge retention time were the most influential on net heterotrophic and autotrophic biomass growth rates.

Prevalence and characterization of Escherichia coli isolated from the Upper Oconee Watershed in Northeast Georgia

Surface waters are important sources of water for drinking, industrial, agricultural, and recreational uses; hence, contamination of water by fecal, pathogenic, or antimicrobial resistant (AR) bacteria is a major environmental and public health concern. However, very little data is available on prevalence of these bacteria in surface water throughout a watershed. This study aimed to characterize Escherichia coli present in the Upper Oconee Watershed, a mixed-use watershed in Athens, GA, USA for potential pathogenicity and AR. E. coli were enumerated by colony counts, cultured by enrichment and direct plating, and characterized by phylo-groups, diarrheagenic pathotypes, and antimicrobial susceptibility. From the analysis, 99.3% (455/458) of the total samples were positive for E. coli resulting in 496 isolates. E. coli counts were as high as 1.2×10⁴ CFU/100 ml, which is above the United States Environmental Protection Agency (U.S. EPA) threshold for recreational water (235 CFU/100 ml based on a one-time measurement). Phylo-groups B2 (31.7%; 157/496) and B1 (30.8%; 153/496) were the most prevalent among the isolates. Enteropathogenic E. coli (EPEC) (19/496) and Shiga toxin-producing E. coli (STEC) (1/496) were the only diarrheagenic pathotypes detected. AR was observed in 6.9% (34/496) of the isolates, 15 of which were multidrug resistant (MDR; resistance to two or more classes of antimicrobials). Tetracycline resistance was most often detected (76.5%; 26/34), followed by ampicillin (32.4%; 11/34), streptomycin (23.5%; 8/34), sulfisoxazole (23.5%; 8/34), and nalidixic acid (14.7%; 5/34). Results from this study showed that E. coli is prevalent in high levels in the Upper Oconee Watershed, suggesting possible widespread fecal contamination. The presence of pathogenic, AR E. coli in the watershed indicates that environmental water can serve as a reservoir of resistant bacteria that may be transferred to humans through drinking and recreational activities.

Multidrug resistance, prevalence and phylogenetic analysis of genes encoding class II and III integrons in clinically isolated Escherichia coli

The present study was conducted to evaluate the susceptibility, multidrug resistance and genetic characteristics of Escherichia coli (E. coli) strains, isolated from clinical samples from Jazan Hospital, Jazan, Saudi Arabia. A total of 95 samples were recruited from wound, urine, stool and blood. The isolates were assessed for their antibiotic susceptibilities and the presence of class II and III integrons was studied using PCR technique. Integron II-positive PCR products were further confirmed using partial sequencing. Ampicillin (84.2%) was found to be the most resistant antibiotic followed by ciprofloxacin (57.9%), gentamicin (56.8%), nalidixic acid (50.5%), cefotaxim (49.5%), ofloxacin (45.3%), amikacin (26.3%) and imipenem (16.8%), respectively. Seventy-six isolated strains were designated as multidrug resistant (MDR), while non-MDR was found in 19 strains (20.0%). Out of 76 MDR E. coli isolates, 41 (53.9%) were identified as positive for class II and 5 (6.5%) were positive for class III integron. Bioinformatics' analysis have shown that the sequences of our samples aligned along with many published sequences of integron II. Our findings further strengthen the significance of hospital-based and community E. coli strains on rising the burden of antimicrobial resistance.

Evolution of mutation rates in hypermutable populations of Escherichia coli propagated at very small effective population size

Mutation is the ultimate source of the genetic variation-including variation for mutation rate itself-that fuels evolution. Natural selection can raise or lower the genomic mutation rate of a population by changing the frequencies of mutation rate modifier alleles associated with beneficial and deleterious mutations. Existing theory and observations suggest that where selection is minimized, rapid systematic evolution of mutation rate either up or down is unlikely. Here, we report systematic evolution of higher and lower mutation rates in replicate hypermutable Escherichia coli populations experimentally propagated at very small effective size-a circumstance under which selection is greatly reduced. Several populations went extinct during this experiment, and these populations tended to evolve elevated mutation rates. In contrast, populations that survived to the end of the experiment tended to evolve decreased mutation rates. We discuss the relevance of our results to current ideas about the evolution, maintenance and consequences of high mutation rates.

Genotypic characterization of quinolone resistant-Escherichia coli isolates from retail food in Morocco

This study was conducted to assess the retail food as a possible vehicle for antimicrobial resistant, particularly quinolones resistant and pathogenic Escherichia coli. We determined the prevalence and characteristics of nalidixic acid (Nal) resistant E. coli isolates from diverse retail food samples. In all, 70 (28%) of 250 E. coli isolates studied were Nal-resistant E. coli and 91% of these were multi-drug resistant. Plasmid mediated quinolone resistance genes were identified in 32 isolates, including aac(6')-Ib-cr (n = 16), qnrS1 (n = 11) and qnrB19 (n = 7). Mutations in gyr A and par C genes were detected among 80% of the isolates, and the isolates showed substitution Ser83-Leu and Asp87-Asn in gyrA and Ser80-Ile in parC. In addition, three different gene cassettes were identified (aadA1, aadA7, aac(3)-Id) in 18%. Virulence-associated genes stx1, eae, sfa, hlyA and stx2 were found in six (8%), three (4%), two (3%), three (4%) and three (4%) isolates, respectively. E. coli isolates of phylogenetic group A were dominant (64%, 45/70). Pulsed field gel electrophoresis revealed none epidemiological relationship between these isolates. The results of this work report the higher frequency of Nal-resistant E. coli isolates from Moroccan retail food samples including MDR and pathogenic isolates.

In vitro pharmacological interaction of caffeine and first-line antibiotics is antagonistic against clinically important bacterial pathogens

The in vitro antibacterial activity of pure caffeine powder and its interaction with first line antibiotic against bacterial isolates were investigated with the macrobroth dilution and the checkerboard assay methods. This study showed that caffeine and the antibiotics exhibited various degrees of antibacterial activities. While caffeine had MICs ranging between 67.19 and 268.75 µg/ml, chloramphenicol was characterized by MICs between 0.98 and 31.25 µg/ml, kanamycin - 15.63-62.5 µg/ml, nalidixic acid - 0.49-250 µg/ml, erythromycin - 0.49-62.5 µg/ml, tetracycline - 1.99-62.5 µg/ml and metronidazole - 15.63-31.25 µg/ml. Combining ½ MICs and MICs of caffeine with the antibiotics as well as direct combination of caffeine and the antibiotics resulted in significant reduction of antibiotics' effectiveness. The fractional inhibitory concentration index (FICI) for the combination of ½ MICs of caffeine with different antibiotics showed antagonistic interactions with the antibiotics except kanamycin which had additive and indifferent interactions with caffeine. The FICI of the MICs of caffeine combined with antibiotics showed a reduction in the number of antagonistic interactions as chloramphenicol, nalidixic acid and erythromycin showed some indifferent interactions while kanamycin was the only antibiotic that showed indifferent interaction against all the bacterial isolates. The direct combination of caffeine and the antibiotics resulted in significant antagonistic interactions higher than in the case when caffeine, at the ½ MICs and MICs, was combined with the antibiotics. Although caffeine demonstrated significant antibacterial activity against the selected bacterial isolates, its combination with the selected antibiotics resulted in significant antagonistic interactions. Caffeine should not be combined with antibiotics as this could result in serious therapeutic failure and, possibly, drug toxicity in vivo.

[Effects of antibiotics on the transfer frequency of SXT/R391 element of Vibrio alginolyticus]

OBJECTIVE

We studied the effects of nalidixic acid, norfloxacin and kanamycin on the transfer frequency of SXT/R391 element ICEValA056-1 in Vibrio alginolyticus.

METHODS

The circular ICEValA056-1 in V. alginolyticus A056 was detected by PCR. Conjugation experiments were conducted between V. alginolyticus A056 and Escherichia coli VB111 to explore the frequency variation of the integrating conjugative elements transfer after donor strain A056 was cultured in Luria Broth containing nalidixic acid or norfloxacin or kanamycin in different concentrations for 15 min or 30 min.

RESULTS

Circular ICEValA056-1 was detected in V. alginolyticus A056, indicating that ICEValA056-1 had the potential to transfer. Treatment with 40 μg/mL nalidixic acid for 30 min increased the transfer frequency of ICEValA056-1 to19.59 folds. Treatment with 50 μg/mL norfloxacin for 15 min increased the transfer frequency of ICEValA056-1 to 31.25 folds. The transfer frequency of ICEValA056-1 had no significant changes under treatment with different concentrations of kanamycin for 30 min.

CONCLUSION

This study indicates that some antibiotics can obviously increase the transfer frequency of ICEValA056-1, and that antibiotics abuse and arbitrarily discharge might intensify dissemination of integrating conjugative elements from V. alginolyticus to other bacteria.

Dynamics and Cell-Type Specificity of the DNA Double-Strand Break Repair Protein RecN in the Developmental Cyanobacterium Anabaena sp. Strain PCC 7120

DNA replication and repair are two fundamental processes required in life proliferation and cellular defense and some common proteins are involved in both processes. The filamentous cyanobacterium Anabaena sp. strain PCC 7120 is capable of forming heterocysts for N₂ fixation in the absence of a combined-nitrogen source. This developmental process is intimately linked to cell cycle control. In this study, we investigated the localization of the DNA double-strand break repair protein RecN during key cellular events, such as chromosome damaging, cell division, and heterocyst differentiation. Treatment by a drug causing DNA double-strand breaks (DSBs) induced reorganization of the RecN focus preferentially towards the mid-cell position. RecN-GFP was absent in most mature heterocysts. Furthermore, our results showed that HetR, a central player in heterocyst development, was involved in the proper positioning and distribution of RecN-GFP. These results showed the dynamics of RecN in DSB repair and suggested a differential regulation of DNA DSB repair in vegetative cell and heterocysts. The absence of RecN in mature heterocysts is compatible with the terminal nature of these cells.

Molecular level understanding of resistance to nalidixic acid in Salmonella enteric serovar typhimurium associates with the S83F sequence type

Nalidixic acid is an antibiotic drug used for treatment of Salmonellosis, a gastrointestinal infection. DNA gyrase subunit A (GyrA) of Salmonella typhimurium is the drug target for nalidixic acid. Resistance of GyrA to nalidixic acid, because of a point mutation in S. typhimurium, was recently reported. Substitution of Phe in place of Ser at locus 83 in GyrA of S. typhimurium has been experimentally associated with nalidixic acid resistance. Despite recent efforts, the mechanism of this resistance is not well understood. In this investigation we used computational techniques to address this shortcoming. Our results showed that contact with residue Arg 91 is certainly important for efficient binding of nalidixic acid to the target protein, and that mutation of this residue results in 180° rotation of the antibiotic in its binding pocket, around its own long axis. It is hoped these findings may enable development of new antibiotics against resistant forms of Salmonella.

Drug Resistance Reversal Potential of Ursolic Acid Derivatives against Nalidixic Acid- and Multidrug-resistant Escherichia coli

As a part of our drug discovery program, ursolic acid was chemically transformed into six semi-synthetic derivatives, which were evaluated for their antibacterial and drug resistance reversal potential in combination with conventional antibiotic nalidixic acid against the nalidixic acid-sensitive and nalidixic acid-resistant strains of Escherichia coli. Although ursolic acid and its all semi-synthetic derivatives did not show antibacterial activity of their own, but in combination, they significantly reduced the minimum inhibitory concentration of nalidixic acid up to eightfold. The 3-O-acetyl-urs-12-en-28-isopropyl ester (UA-4) and 3-O-acetyl-urs-12-en-28-n-butyl ester (UA-5) derivatives of ursolic acid reduced the minimum inhibitory concentration of nalidixic acid by eightfold against nalidixic acid-resistant and four and eightfold against nalidixic acid-sensitive, respectively. The UA-4 and UA-5 were further evaluated for their synergy potential with another antibiotic tetracycline against the multidrug-resistant clinical isolate of Escherichia coli-KG4. The results showed that both these derivatives in combination with tetracycline reduced the cell viability in concentration-dependent manner by significantly inhibiting efflux pump. This was further supported by the in silico binding affinity of UA-4 and UA-5 with efflux pump proteins. These ursolic acid derivatives may find their potential use as synergistic agents in the treatment of multidrug-resistant Gram-negative infections.

Efficacy of Ciprofloxacin for Treatment of Cholera Associated with Diminished Susceptibility to Ciprofloxacin to Vibrio cholerae O1

Objective

We identified a poor clinical response to treatment of cholera with a single 1 g dose of ciprofloxacin, a standard treatment for cholera.

Methods

To determine reasons for the poor response and better therapeutic approaches we examined the minimal inhibitor concentration (MIC, n = 275) and disc-diffusion zone sizes (n = 205) for ciprofloxacin and nalidixic acid of V. cholerae O1 strains isolated in Bangladesh from 1994 to 2012, and reexamined data from 161patients infected with Vibrio cholerae O1 recruited in four clinical trials who received single- or multiple-dose ciprofloxacin for treatment of cholera and compared their clinical response to the V. cholerae O1 susceptibility.

Results

Although all 275 isolates of V. cholerae O1 remained susceptible to ciprofloxacin using standard MIC and disc-diffusion thresholds, the MIC⁹⁰ to ciprofloxacin increased from 0.010 in 1994 to 0.475 μgm/ml in 2012. Isolates became frankly resistant to nalidixic with the MIC⁹⁰ increasing from 21 μgm/ml in 1994 to >256 μgm/ml and 166 of 205 isolates from 1994 to 2005 being frankly resistant using disc-diffusion testing. Isolates resistant to nalidixic acid by disc-diffusion testing had a median ciprofloxacin MIC of 0.190 μgm/ml (10^th-90^th centiles 0.022 to 0.380); nalidixic acid-susceptible isolates had a median ciprofloxacin MIC of 0.002 (0.002 to 0.012).The rate of clinical success with single-dose ciprofloxacin treatment for nalidixic acid-susceptible strains was 94% (61 of 65 patients) and bacteriologic success 97% (63/65) compared to 18% (12/67) and 8% (5/67) respectively with nalidixic acid-resistant strains (P<0.001 for both comparisons). Multiple-dose treatment with ciprofloxacin had 86% and 100% clinical and bacteriologic success rates respectively in patients infected with nalidixic acid-susceptible strains of V. cholerae O1 compared to clinical success 67% and bacteriologic success 60% with nalidixic acid-resistant strains.

Conclusions

Single-dose ciprofloxacin is not effective for treating cholera caused by V. cholerae O1 with diminished susceptibility to ciprofloxacin, and nalidixic acid disc-diffusion testing effectively screens for such isolates.

[Role of double strand DNA break repair for quinolone sensitivity in Escherichia coli: therapeutic implications]

INTRODUCTION

Quinolones are one of the types of antibiotics with higher resistance rates in the last years. At molecular level, quinolones block type II topoisomerases producing double strand breaks (DSBs). These DSBs could play a double role, as inductors of the quinolone bactericidal effects but also as mediators of the resistance and tolerance mechanisms.

MATERIAL AND METHODS

In this work we have studied the molecular pathways responsible for DSBs repair in the quinolone susceptibility: the stalled replication fork reversal (recombination-dependent) (RFR), the SOS response induction, the translesional DNA synthesis (TLS) and the nucleotide excision repair mechanisms (NER). For this reason, at the European University in Madrid, we analysed the minimal inhibitory concentration (MIC) to three different quinolones in Escherichia coli mutant strains coming from different type culture collections.

RESULTS

recA, recBC, priA and lexA mutants showed a significant reduction on the MIC values for all quinolones tested. No significant changes were observed on mutant strains for TLS and NER.

DISCUSSION

These data indicate that in the presence of quinolones, RFR mechanisms and the SOS response could be involved in the quinolone susceptibility.

[Salmonella enterica with nonclassical quinolone resistance phenotype in pediatric patients]

INTRODUCTION

Decreased susceptibility to fluoroquinolones in Salmonella spp. may lead to treatment failures. The use of ciprofloxacin for extraintestinal and serious intestinal Salmonella infections in children is controversial and therefore the clinical relevance of these strains is not significant. Consequently little is know about the quinolone resistance of strains Salmonella of our paediatric population. The objective of this study was to assess the incidence of nonclassical quinolone resistance phenotype in paediatric patients.

MATERIAL AND METHODS

Two hundred and sixty eight Salmonella spp. from Hospital Infantil Universitario Niño Jesús of Madrid (2009-2013) were tested against nalidixic acid and ciprofloxacin by microdilution. Moreover, 146 strains (2011-2013) were tested against ciprofloxacin by E-test. Reduced ciprofloxacin susceptibility was defined as a MIC of 0.125-1 mg/L.

RESULTS

Of 42 isolates with reduced ciprofloxacin susceptibility, four isolates showing nonclassical quinolone resistance phenotype. Three were confirmed as carrying of plasmid-mediated quinolone resistance-conferring genes qnr.

CONCLUSIONS

The percentage of strains with a genotype that confers a nonclassical quinolone resistance phenotype is low in our series. The identification of these isolates is difficult using conventional methods, but its ability of horizontal spread recommends an appropriate identification. Taking into account the low isolation rate of these strains in this study, evaluation of ciprofloxacin MIC on every nalidixic acid susceptible strain would not be cost effective. Alternatively, we propose to evaluate periodically any changing trend.

Synergistic antimicrobial activity of Camellia sinensis and Juglans regia against multidrug-resistant bacteria

Synergistic combinations of antimicrobial agents with different mechanisms of action have been introduced as more successful strategies to combat infections involving multidrug resistant (MDR) bacteria. In this study, we investigated synergistic antimicrobial activity of Camellia sinensis and Juglans regia which are commonly used plants with different antimicrobial agents. Antimicrobial susceptibility of 350 Gram-positive and Gram-negative strains belonging to 10 different bacterial species, was tested against Camellia sinensis and Juglans regia extracts. Minimum inhibitory concentrations (MICs) were determined by agar dilution and microbroth dilution assays. Plant extracts were tested for synergistic antimicrobial activity with different antimicrobial agents by checkerboard titration, Etest/agar incorporation assays, and time kill kinetics. Extract treated and untreated bacteria were subjected to transmission electron microscopy to see the effect on bacterial cell morphology. Camellia sinensis extract showed higher antibacterial activity against MDR S. Typhi, alone and in combination with nalidixic acid, than to susceptible isolates." We further explore anti-staphylococcal activity of Juglans regia that lead to the changes in bacterial cell morphology indicating the cell wall of Gram-positive bacteria as possible target of action. The synergistic combination of Juglans regia and oxacillin reverted oxacillin resistance of methicillin resistant Staphylococcus aureus (MRSA) strains in vitro. This study provides novel information about antimicrobial and synergistic activity of Camellia sinensis and Juglans regia against MDR pathogens.

[Role of reactive oxygen species in the bactericidal action of quinolones--inhibitors of DNA gyrase]

Quinolone antibiotics inhibit DNA gyrase, but the induced degradation of chromosomal DNA is determined by a complex process of joint action quinolones and hydroxyl radical OH'. To quantify the level of stress responses and their time dependence in bacterial cells the induced specific lux-biosensors--the bacterium Escherichia coli, containing hybrid plasmids pColD'::lux; pSoxS'::lux; pKatG'::lux were used in this study. It is shown that quinolones (nalidixic acid, norfloxacin) induce SOS-response and oxidative stress with the formation of superoxide anion O2(-) in E. coli cells. The main parameters of SOS-response and oxidative stress, which depend on the quinolone concentration, are determined. Formation of superoxide anion O2(-) occurs almost simultaneously with the SOS-response. The mutant strain of E. coli sodA sodB, which do not contain active forms of superoxide dismutases SodA and SodB, is characterized by an increased resistance to quinolones as compared to the wild type cells. At high concentrations of quinolones (nalidixic acid-->20 μg/mL; norfloxacin-->500 ng/mL) their bactericidal effect is partially caused by conversion of the superoxide anion to hydrogen peroxide H2O2, conducted by superoxide dismutases SodA and SodB, which is followed by the Fenton reaction and the formation of toxic hydroxyl radical OH'. At low concentrations of quinolones (nalidixic acid--<20 μg/mL; norfloxacin--<500 ng/mL), the role of active oxygen species in the antimicrobial effect is practically nonexistent.

Quinolone resistance mechanisms in Salmonella enterica serovars Hadar, Kentucky, Virchow, Schwarzengrund, and 4,5,12:i:-, isolated from humans in Switzerland, and identification of a novel qnrD variant, qnrD2, in S. Hadar

Human isolates of Salmonella enterica serovars Hadar, Kentucky, Virchow, Schwarzengrund, and the monophasic variant of S. Typhimurium, Salmonella enterica subsp. enterica serovar 4,5,12:i:- were examined for mutations within the quinolone resistance target genes gyrA, gyrB, parC, and parE and for plasmid-mediated resistance genes. Differences were observed among the serovars. A novel variant of qnrD, qnrD2, was detected in an S. Hadar isolate.

Molecular epidemiology of Salmonella enterica serovar Kottbus isolated in Germany from humans, food and animals

Salmonella enterica serovar Kottbus has been continuously isolated from poultry and poultry meat, especially from turkey. We investigated by comparative molecular typing 95 S. Kottbus isolates obtained in Germany between 2000 and 2011 from poultry/poultry meat, pig/pork, cattle, reptiles, the environment as well as from human cases to identify potential infection sources for humans, especially the role of poultry and poultry products as vehicle in transmission of S. Kottbus isolates to humans. Multilocus sequence typing analysis detected three main genetic lineages. Most human isolates belonged to lineage 1 represented by sequence types ST212 and ST808. Part of the isolates isolated from cattle and pork were also linked to this lineage. Nevertheless, human isolates and especially isolates from poultry/poultry meat, and with less extend from other livestock, grouped in lineage 2 represented by ST582. Four additional isolates from reptiles and humans belonging to ST1669 represented the third lineage. The three lineages were also reflected by pulsed-field gel electrophoresis typing data and DNA microarray analysis of 102 pathogenicity genes. Antimicrobial resistance especially to nalidixic acid and ciprofloxacin was predominantly observed in isolates assigned to lineage 2, which contains predominantly resistant isolates compared to lineage 1 and 3. Sequencing of the quinolone resistance-determining region of gyrA revealed a point mutation in codon 83 or 87 responsible for nalidixic acid resistance and MIC values for ciprofloxacin between 0.125 and 0.25mg/l. Overall, this study showed that in Germany a specific S. Kottbus lineage (ST582), which is well-established in poultry, can be transmitted to humans by poultry meat and, consequently, poses a risk for human health.

[Regulation of Yersinia pseudotuberculosis major porin expression in response to antibiotic stress]

The OmpF porin gene expression in Yersinia pseudotuberculosis in response to antibiotics of two different classes (kanamycin and nalidixic acid) was analyzed using quantitative PCR and a fluorescence reporter system. Both antibiotics downregulated the expression of the ompF gene. The nalidixic acid significantly reduced ompF expression, while kanamycin, for which porins are considered to be an alternative transport route, only slightly reduced the ompF level.

Elevated mutagenesis does not explain the increased frequency of antibiotic resistant mutants in starved aging colonies

The frequency of mutants resistant to the antibiotic rifampicin has been shown to increase in aging (starved), compared to young colonies of Eschierchia coli. These increases in resistance frequency occur in the absence of any antibiotic exposure, and similar increases have also been observed in response to additional growth limiting conditions. Understanding the causes of such increases in the frequency of resistance is important for understanding the dynamics of antibiotic resistance emergence and spread. Increased frequency of rifampicin resistant mutants in aging colonies is cited widely as evidence of stress-induced mutagenesis (SIM), a mechanism thought to allow bacteria to increase mutation rates upon exposure to growth-limiting stresses. At the same time it has been demonstrated that some rifampicin resistant mutants are relatively fitter in aging compared to young colonies, indicating that natural selection may also contribute to increased frequency of rifampicin resistance in aging colonies. Here, we demonstrate that the frequency of mutants resistant to both rifampicin and an additional antibiotic (nalidixic-acid) significantly increases in aging compared to young colonies of a lab strain of Escherichia coli. We then use whole genome sequencing to demonstrate conclusively that SIM cannot explain the observed magnitude of increased frequency of resistance to these two antibiotics. We further demonstrate that, as was previously shown for rifampicin resistance mutations, mutations conferring nalidixic acid resistance can also increase fitness in aging compared to young colonies. Our results show that increases in the frequency of antibiotic resistant mutants in aging colonies cannot be seen as evidence of SIM. Furthermore, they demonstrate that natural selection likely contributes to increases in the frequency of certain antibiotic resistance mutations, even when no selection is exerted due to the presence of antibiotics.

Antibiotic resistance is one of the most pressing threats on human health worldwide. Such resistance has been increasing largely due to widespread antibiotic usage. However, it has also been noticed that under certain growth limiting conditions, there is an increase in resistance frequency that is independent of the presence of antibiotics. Such increases in antibiotic resistance frequency can greatly affect the dynamics of antibiotic resistance emergence and spread. Yet currently their causes are far from understood. Many assume that we observe more resistance mutations when growth is limited, because more mutations occur under such conditions. Here we use whole genome sequencing to show that increases in resistance frequency to two different antibiotics under starvation cannot be explained by increased mutagenesis. We further show that at least some of the increase in resistance frequency is likely to be explained by natural selection that favors certain resistance mutations conferring increased fitness under starvation. These results are intriguing as they demonstrate that positive selection may contribute to increases in the frequency of certain antibiotic resistance mutations, even in the absence of selection exerted by the presence of antibiotics.

Occurrence of fluoroquinolones and fluoroquinolone-resistance genes in the aquatic environment

Fluoroquinolones (FQs) have been detected in aquatic environments in several countries. Long-term exposure to low levels of antimicrobial agents provides selective pressure, which might alter the sensitivity of bacteria to antimicrobial agents in the environment. Here, we examined FQ levels and the resistance of Escherichia coli (E. coli) to FQs by phenotyping and genotyping. In the aquatic environment in Osaka, Japan, ciprofloxacin, enoxacin, enfloxacin, lomefloxacin, norfloxacin, and ofloxacin were detected in concentrations ranging from 0.1 to 570 ng L(-1). FQ-resistant E. coli were also found. Although no obvious correlation was detected between the concentration of FQs and the presence of FQ-resistant E. coli, FQ-resistant E. coli were detected in samples along with FQs, particularly ciprofloxacin and ofloxacin. Most FQ-resistant E. coli carried mutations in gyrA, parC, and parE in quinolone resistance-determining regions. No mutations in gyrB were detected in any isolates. Amino acid changes in these isolates were quite similar to those in clinical isolates. Six strains carried the plasmid-mediated quinolone resistance determinant qnrS1 and expressed low susceptibility to ciprofloxacin and nalidixic acid: the minimum inhibitory concentrations ranged from 0.25 μg mL(-1) for ciprofloxacin, and from 8 to 16 μg mL(-1) for nalidixic acid. This finding confirmed that plasmids containing qnr genes themselves did not confer full resistance to quinolones. Because plasmids are responsible for much of the horizontal gene transfer, these genes may transfer and spread in the environment. To our knowledge, this is the first report of plasmid-mediated quinolone resistance determinant qnrS1 in the aquatic environment, and this investigation provides baseline data on antimicrobial resistance profiles in the Osaka area.

[A nalidixic acid-resistant Salmonella enteritidis outbreak in Popayán, Cauca, 2011]

INTRODUCTION

Salmonella Enteritidis is recognized worldwide as one of the main agents of human gastrointestinal infection. Several reports indicate the presence of isolates with decreased sensitivity to ciprofloxacin that can lead to a delayed response or the development of resistance during treatment.

OBJECTIVE

To describe and characterize isolates of Salmonella Enteritidis associated to an outbreak of food-borne diseases in Popayán, Cauca.

MATERIALS AND METHODS

Ten Salmonella Enteritidis isolates from nine patients and one food sample (chicken sandwich) were analyzed by biochemical tests, serotyping and antimicrobial sensitivity. The minimum inhibitory concentration to ciprofloxacin was determined by E-test and the genetic profile of the isolates was tested by pulsed field gel electrophoresis (PFGE) with XbaI and Blnl enzymes.

RESULTS

Salmonella Enteritidis was identified in all isolates. They were resistant to nalidixic acid and had a decreased sensitivity to ciprofloxaxin between 0.25 and 0.5 μg/ml; all isolates were sensitive to all the other antimicrobials we tested. Ten isolates were grouped by PFGE with the XbaI enzyme in the COIN11.JEG.X01.0038 pattern, and seven isolates were confirmed with the BlnI enzyme using the COIN11.JEG.A26.0009 pattern.

CONCLUSION

We report for the first time an outbreak of nalidixic acid-resistant Salmonella Enteritidis in Colombia and confirmed by phenotypic and genotypic analysis the association between the isolates from patients and the chicken sandwich as the source of infection.

[Optimization of conditions of Pseudomonas aeruginosa bacteriocin induction]

Influence of cultivation conditions on activity of bacteriocins produced by Pseudomonas aeruginosa YKM B-333 has been investigated. It was shown, that the induction of bacteriocins with maximum activity values occurs on LB medium at 28 degrees C after addition of 100 microg/ml of nalidixic acid in a late logarithmic growth phase. Using the proposed methods for induction optimization permits to improve activity of P. aeruginosa YKM B-333 bacteriocins 256 times and to reach the index of 6.5 million AU/ml.

Emergence of decreased susceptibility to extended-spectrum cephalosporins in Neisseria gonorrhoeae in India

BACKGROUND

In the past, Neisseria gonorrhoeae has developed resistance to antimicrobial agents used for its treatment. Consequently, extended-spectrum cephalosporins form the mainstay of treatment for gonorrhoea.

METHODS

Samples from 88 patients attending the sexually transmitted diseases clinics from December 2009 to January 2011 in two referral hospitals in New Delhi were studied. Antimicrobial susceptibility testing was done using the disc diffusion method as per the calibrated dichotomous sensitivity technique against the following antibiotics: penicillin (0.5 i.u.), tetracycline (10 μg), nalidixic acid (30 μg), ciprofloxacin (1 μg), spectinomycin (100 μg), ceftriaxone (0.5 μg) and cefpodoxime (10 μg) (Oxoid UK). Azithromycin (15 μg) (Oxoid, UK) was tested as per the guidelines of the Clinical and Laboratory Standards Institute. Minimum inhibitory concentrations were determined using the Etest for penicillin, tetracycline, ciprofloxacin, ceftriaxone, spectinomycin and azithromycin as per the manufacturer's instruction (Biomerieux, France).

RESULTS

Eighteen isolates of Neisseria gonorrhoeae were obtained. Three of these had decreased susceptibility to ceftriaxone and cefpodoxime by the disc diffusion method. The minimum inhibitory concentrations of ceftriaxone for two isolates were 0.064 μg/ml and for one isolate it was 0.125 μg/ml.

CONCLUSION

Higher minimum inhibitory concentrations to extended-spectrum cephalosporins is of concern as it has been shown to precede treatment failure. This may warrant its use in increased/multiple dosages alone or possibly in combination (dual therapy), thereby complicating effective disease control. Our report is in accordance with earlier reports from different parts of the world. Therefore, a continuous surveillance of antimicrobial resistance is crucial to tailor treatment schedules for Neisseria gonorrhoeae in a particular geographical region.

[Prevalence of qnr genes in clinical Enterobacteriaceae non-susceptible to fluoroquinolone in Poland]

INTRODUCTION

Fluoroquinolone are broad-spectrum antimicrobial agents extensively used by physicians. This widespread use has been associated with increased level ofquinolone resistance strains, particularly in Enterobacteriaceae. Plasmid-mediated quinolone resistance (PMQR) including Qnr determinants with the potential for horizontal transfer confer to quinolone resistance. Plasmid harboring qnr genes may also encode extended-spectrum beta-lactamases (ESBLs) such as CTX-M, SHV and TEM type. The prevalence ofplasmid-mediated quinolone resistance (PMQR) determinants like qnrA, qnrB and qnrS was investigated in a collection of 215 Enterobacteriaceae strains with reduced susceptibility to fluoroquinolone.

METHODS

The isolates (n=215) were collected from 1 March to 31 September, 2010 in a regular hospital in Warsaw, Poland. The resistance to nalidixic acid, norfloxacin and ciprofloxacin was determinated by twofold agar dilution method, while MICs of moxifloxacin were examined by using E-test. The prevalence of qnrA, qnrB, qnrS, blaCTX-M, blaSHV and blaiTEM was evaluated by PCR. All PCR-products for qnr were sequenced. The epidemiological relationship between positive isolates was studied by PFGE method.

RESULTS

Eighteen isolates (8,3%) carried the qnr gene encoding the QnrA, QnrB or QnrS. The coexistence of both qnrA and qnrS genes was noted in one isolate of E. coli. The qnrB gene was the most common qnr type found. All the Qnr-producing strains were simultaneously resistant to naldixic acid and different - level non-susceptible fluoroquinolone (MIC CIP 1.5-1024 microg/ml). Most of qnr-positive strains (88.9%) were extended-spectrum beta-lactamase (ESBL) producers of CTX-M and TEM types predominantly.

CONCLUSIONS

The present study highlights the wide spread of Qnr-like determinants in clinical Enterobacteriaceae non-susceptible to fluoroquinolone in Poland, with an association with the ESBL.

Bioenhancing and antimycobacterial agents from Ammannia multiflora

The methanolic extract of Ammannia multiflora (Lythraceae) showed significant bioenhancing activity with the antibiotic nalidixic acid. Bioassay-guided fractionation of MeOH extract resulted in the isolation of a novel compound, 2,5-bis-(3,3'-hydroxyaryl)tetrahydrofuran, named as ammaniol (5), along with 9 other known compounds (1-4, 6-10). Furthermore, compound 4-hydroxy- α-tetralone (1) was converted into five semisynthetic acyl derivatives, 1A-1E, which were evaluated along with compounds 1, 5, 6, 9, and 10 for their bioenhancing activity in combination with nalidixic acid against the two strains, CA8000 and DH5 α, of Escherichia coli. The results showed that the methanolic extract of A. multiflora and compounds 1 and 9 possessed significant bioenhancing activity and reduced the dose of nalidixic acid fourfold while compounds 5, 6, 10 and semisynthetic derivatives 1A- 1E reduced the dose of nalidixic acid twofold. Compound 5 was also tested for antimycobacterial activity against Mycobacterium H37Rv and was found to show moderate activity (MIC 25 µg/mL) against this pathogen.