Effect of quinolone treatment on selection and persistence of quinolone-resistant Escherichia coli in swine faecal flora

Transmission rates of veterinary and clinically important antibiotic resistant Escherichia coli: A meta- ANALYSIS

The transmission rate per hour between hosts is a key parameter for simulating transmission dynamics of antibiotic-resistant bacteria, and might differ for antibiotic resistance genes, animal species, and antibiotic usage. We conducted a Bayesian meta-analysis of resistant Escherichia coli (E. coli) transmission in broilers and piglets to obtain insight in factors determining the transmission rate, infectious period, and reproduction ratio. We included blaCTX-M-1, blaCTX-M-2, blaOXA-162, catA1, mcr-1, and fluoroquinolone resistant E. coli. The Maximum a Posteriori (MAP) transmission rate in broilers without antibiotic treatment ranged from 0.4∙10-3 to 2.5∙10-3 depending on type of broiler (SPF vs conventional) and inoculation strains. For piglets, the MAP in groups without antibiotic treatment were between 0.7∙10-3 and 0.8∙10-3, increasing to 0.9∙10-3 in the group with antibiotic treatment. In groups without antibiotic treatment, the transmission rate of resistant E. coli in broilers was almost twice the transmission rate in piglets. Amoxicillin increased the transmission rate of E. coli carrying blaCTX-M-2 by three-fold. The MAP infectious period of resistant E. coli in piglets with and without antibiotics is between 971 and 1065 hours (40 - 43 days). The MAP infectious period of resistant E. coli in broiler without antibiotics is between 475 and 2306 hours (20 - 96 days). The MAP infectious period of resistant E. coli in broiler with antibiotics is between 2702 and 3462 hours (113 - 144 days) which means a lifelong colonization. The MAP basic reproduction ratio in piglets of infection with resistant E. coli when using antibiotics is 27.70, which is higher than MAP in piglets without antibiotics between 15.65 and 18.19. The MAP basic reproduction ratio in broilers ranges between 3.46 and 92.38. We consider three possible explanations for our finding that in the absence of antibiotics the transmission rate is higher among broilers than among piglets: i) due to the gut microbiome of animals, ii) fitness costs of bacteria, and iii) differences in experimental set-up between the studies. Regarding infectious period and reproduction ratio, the effect of the resistance gene, antibiotic treatment, and animal species are inconclusive due to limited data.

Effect of Bacterial Resistance of Escherichia coli From Swine in Large-Scale Pig Farms in Beijing

With widespread use of antibiotics in the aquaculture industry, bacterial resistance has recently attracted increasing attention. Continuous emergence of multi-resistant bacteria has greatly threatened human and animal health, as well as the quality and safety of livestock products. To control bacterial resistance, the effect of bacterial resistance needs to be well understood. The purpose of this study was to explore the factors influencing Escherichia coli (E. coli) drug resistance in large-scale pig farms. In this study, 296 strains of E. coli isolated and identified from large-scale pig farms in Beijing were used as the research objects. In vitro drug sensitivity tests were used to determine the sensitivity to 10 antibiotics of pig-derived E. coli. SPSS logistic regression was employed to analyze the effects of the season, pig type, sampling point (medication type) and sampling location on resistance and multi-drug resistance of E. coli from pigs. The degrees of drug resistance to 10 antibiotics of the 296 strains of pig-derived E. coli were varied, their resistance rates were between 4.05 and 97.64%, and their multi-drug resistance was appalling, with the highest resistance to six antibiotics being 26.35%. The isolated strains were proven more resistant to tetracyclines, penicillin and chloramphenicol, which are commonly used for disease prevention in pig farms, and less resistant to quinolones and aminoglycosides, which are not used in pig farms. The resistance of the isolated strains in spring and summer was generally higher than that in winter. E. coli resistance in piglets, fattening pigs and sows was more serious than that in nursery and sick pigs. The results showed that the season, type of medication and type of pig had an influence on the pig-derived E. coli resistance, among which the type of medication was the most influencing factor.

Antimicrobial use, biosecurity, herd characteristics, and antimicrobial resistance in indicator Escherichia coli in ten Finnish pig farms

We investigated connections between antimicrobial use (AMU), biosecurity, and the numbers of pigs and staff in ten Finnish farrow-to-finish herds. Data on AMU in each herd were collected for 12 months. AMU was quantified as treatment incidences per 1000 days at risk (TI) using the consensus defined daily dose calculation. Biosecurity was scored using the Biocheck.UGent™ system. We also examined antimicrobial resistance patterns of indicator E. coli isolated from faeces of selected pigs. In each herd, two groups of five pigs were formed: 1) antimicrobial treatment group (ANT: at least one pig in the litter was identified as sick and treated with antimicrobials) and 2) non-antimicrobial treatment group (NON: the litter was not medicated). Faecal samples were taken from these pigs at 5 and 22 weeks of age, cultured, and indicator E. coli isolates were tested for antimicrobial susceptibilities. The AMU varied considerably between the herds. Altogether, most of the antimicrobial treatment courses were assigned to weaned piglets. When AMU was quantified as TIs, suckling piglets had the highest TI (mean 46.6), which was significantly higher (P < 0.05) than TIs in fatteners and breeders (9.3 and 7.3, respectively). The difference between TI in suckling and TI in weaned piglets (19.1) was not statistically significant. There was a tendency for a negative correlation between the TI in breeders and the number of sows (r = -0.56, P = 0.09). Larger herds had higher external biosecurity scores than smaller herds (LS-means; 72 vs. 66, P < 0.05). The proportions of E. coli isolates resistant to at least one antimicrobial were higher in pigs at 5 weeks than in pigs at 22 weeks of age (Binomial proportion means; 40.5 % vs. 15.5 %, P < 0.05); as well as proportions of isolates resistant to at least three antimicrobial classes (23.0 % vs. 3.7 %, P < 0.01). These proportions did not differ between the ANT and NON groups at either 5 or 22 weeks of age (P> 0.05). We found few connections: enhanced external biosecurity levels found in the large herds co-occurred with lower use of antimicrobials and herds with low biosecurity scores - especially in the internal subcategories - appeared to have higher proportions of resistant isolates. Conclusively, we suggest that enhancing internal biosecurity might contribute to a reduction in the spreading of antimicrobial resistance in pig herds.

Reduction in antimicrobial resistance prevalence in Escherichia coli from a pig farm following withdrawal of group antimicrobial treatment

An important element in the control of antimicrobial resistance (AMR) is reduction in antimicrobial usage. In the veterinary sector individual antimicrobial treatment of livestock, rather than the use of group treatment, can help achieve this goal. The aim of this study was to investigate how cessation of group antimicrobial treatment impacted the prevalence of AMR in commensal Escherichia coli in pigs at one farm over an 11-month period. Minimum inhibitory concentrations of eight antimicrobials were determined for 259 E. coli isolates collected during the study. A significant reduction in the prevalence of multidrug resistance and a significant increase in the proportion of full susceptibility to the panel of nine antimicrobials tested was seen after 11 months. Whole genome sequencing of 48 multidrug resistant isolates revealed E. coli clones that persisted across multiple visits and provided evidence for the presence of plasmids harbouring AMR genes shared across multiple E. coli lineages. E. coli were also isolated from on-farm environmental samples. Whole genome sequencing of one multidrug resistant isolate obtained from cleaning tools showed it was clonal to pig-derived E. coli that persisted on the farm for 11 months. In this study we provide evidence that withdrawal of group antimicrobial use leads to significant reductions in key indicators for AMR prevalence and the importance of the farm environment as a reservoir of resistant bacteria. These findings support policy makers and producers in the implementation of measures to control AMR and reduce antimicrobial use.

Occurrence of Escherichia coli non-susceptible to quinolones in faecal samples from fluoroquinolone-treated, contact and control pigs of different ages from 24 Swiss pig farms

BACKGROUND

Despite their indispensability in human medicine, fluoroquinolones (FQ) are used for the treatment of bacterial infections in farm animals which increases the risk of transferring FQ-resistant bacteria into the environment and via the food chain to humans. The objectives of this observational study were to follow-up of the presence of quinolone non-susceptible Escherichia coli (QNSE) qualitatively and quantitatively in faecal samples of pigs at four time points (2 weeks old, 4 weeks old, 2 weeks post weaning and during fattening period). Moreover differences between groups of FQ-treated pigs, pigs with contact to treated pigs and control pigs were investigated. Additionally, quinolone and FQ resistance of Escherichia coli isolates of the faecal samples were investigated by determining minimum inhibitory concentrations (MICs).

RESULTS

40.9% of 621 fecal samples contained QNSE. Proportion of samples with detectable QNSE from treated and contact pigs did not differ significantly and were highest in piglets of 2 and 4 weeks of age. However, the proportions of samples with QNSE were significantly lowest in control pigs (7/90; 7.8%; CI = 3.5-14.7%) among all groups. Also, the number of colony-forming units was lowest in both weaners and fattening pigs of the control group compared to treated and contact groups. Following CLSI human breakpoints, in total, 50.4% out of 254 isolates in faecal samples were intermediate or resistant to ciprofloxacin.

CONCLUSIONS

QNSE were present in faeces of pigs independent of age or FQ background but significantly less were found in pigs from farms without FQ usage. Due to the long half-life of FQ, it is likely that only a prolonged absence of fluoroquinolone treatments in pig farming will lead to a reduced frequency of QNSE in the farm environment. Solutions need to be found to minimise the emergence and transfer of quinolone and FQ-resistant bacteria from treated pigs to contact pigs and to farms without FQ usage.

Decrease in fluoroquinolone use in French poultry and pig production and changes in resistance among E. coli and Campylobacter

This paper presents the impact on antimicrobial resistance (AMR) in poultry and pig bacteria of the French EcoAntibio plan, a public policy to reduce antimicrobial use in animals. The analysis was performed using sales data of veterinary antimicrobials and AMR data from bacteria obtained at slaughterhouse and from diseased animals. From 2011-2018, fluoroquinolones exposure decreased by 71.5 % for poultry and 89.7 % for pigs. For Campylobacter jejuni isolated from broilers at slaughterhouses, ciprofloxacin resistance increased from 51 % in 2010 to 63 % in 2018, whereas for turkeys the percentages varied from 56 % in 2014 to 63 % in 2018. For commensal E. coli isolated from the caecal content of broilers at slaughterhouses, the resistance to ciprofloxacin - assessed using an epidemiological cut-off value - increased in broiler isolates from 30.7 % in 2010 to 38.1 % in 2018. In turkeys, the percentage of resistant E. coli isolates decreased from 21.3 % in 2014 to 15.2 % in 2018, whereas in pigs, it increased from 1.9 % in 2009 to 5.5 % in 2017. However, for E. coli isolated from diseased animals, when the breakpoints of 2018 were applied, resistance to fluoroquinolones significantly decreased between 2010 and 2018 from 9.0%-5.4% for broilers/hens, from 7.4 % to 3.4 % for turkeys and from 9.4 % to 3.6 % for pigs. These data show that the major, rapid decrease in the exposition to fluoroquinolones had contrasting effects on resistance in the diverse bacterial collections. Co-selection or fitness of resistant strains may explain why changes in AMR do not always closely mirror changes in use.

Antibiotic resistance in Escherichia coli from pigs from birth to slaughter and its association with antibiotic treatment

The purpose of this longitudinal study was to describe the occurrence of antibiotic resistance in faecal Escherichia coli isolated from pigs between birth and slaughter and its association with antibiotic treatment. Four objectives were addressed: comparison of antibiotic resistance in isolates from a) treated vs. non-treated pigs, b) follow-up vs. initial samples of treated and non-treated pigs, c) pigs receiving treatments via different administration routes and d) sows and their piglets. Each comparison addressed the following antibiotic groups used for treatment: beta-lactams, tetracyclines, polymyxins and macrolides, and the susceptibility of E. coli isolates to the respective agents: ampicillin, tetracycline, colistin and azithromycin. Between 2014 and 2016, 406 focal animals from 29 commercial breeding herds were followed from birth to the end of the relevant fattening periods. All antibiotic treatments in these pigs were documented. Faecal samples were collected from the focal pigs once while suckling, once after weaning and three times during fattening, and from their dams once around farrowing. Escherichia coli isolated from these samples was tested for antibiotic susceptibility. In total, 264 animals from 19 breeding herds were treated with an antibiotic at least once during their lifetime. Beta-lactams, tetracyclines and colistin were used most frequently. Piglets were treated individually by injection (n = 108 treatments) or via drench (9); weaners via feed (192) or water (56) and fatteners via feed (30) or injection (15). Resistance to ampicillin and tetracycline in E. coli was already common prior to antibiotic treatment. Resistance proportions were higher for beta-lactam-, tetracycline-, colistin- and macrolide-treated pigs compared to untreated pigs at different sampling periods (p < 0.05; Fisher's exact test). In the logistic analysis, the difference was confirmed for beta-lactam-treated vs. untreated pigs. In E. coli from macrolide-untreated pigs, resistance to azithromycin was more frequent compared to pre-treatment values. Route of application did not affect rates of antibiotic resistance in the logistic analysis even though Fisher's exact test indicated associations for beta-lactams (feed/water vs. injection), tetracyclines (feed/water vs. non-treatment) and macrolides (tulathromycin-injection vs. tylosin in feed). Piglets were more likely to carry an E. coli resistant to ampicillin or azithromycin if their dams did so as well. Our results suggest further research on resistance effects by administration routes is required. Reducing antibiotic resistance in sows might lead to a lower level of beta-lactam or macrolide-resistant E. coli among their progeny. To preserve treatment options for bacterial infections, antibiotic use should be restricted to necessary cases.

Effects of oral orbifloxacin on fecal coliforms in healthy cats: a pilot study

The study objective was to determine the effect of oral orbifloxacin (ORB) on antimicrobial susceptibility and composition of fecal coliforms in cats. Nine cats were randomized to two groups administered a daily oral dose of 2.5 and 5.0 mg ORB/kg for 7 days and a control group (three cats per group). Coliforms were isolated from stool samples and were tested for susceptibilities to ORB and 5 other drugs. ORB concentration in feces was measured using high-performance liquid chromatography (HPLC). The coliforms were undetectable after 2 days of ORB administration, and their number increased in most cats after termination of the administration. Furthermore, only isolates of Escherichia coli were detected in all cats before administration, and those of Citrobacter freundii were detected after termination of the administration. E. coli isolates exhibited high ORB susceptibility [Minimum inhibitory concentration (MIC), ≤0.125 µg/ml] or relatively low susceptibility (MIC, 1-2 µg/ml) with a single gyrA mutation. C. freundii isolates largely exhibited intermediate ORB susceptibility (MIC, 4 µg/ml), in addition to resistance to ampicillin and cefazolin, and harbored qnrB, but not a gyrA mutation. HPLC revealed that the peaks of mean concentration were 61.3 and 141.0 µg/g in groups receiving 2.5 and 5.0 mg/kg, respectively. Our findings suggest that oral ORB may alter the total counts and composition of fecal coliform, but is unlikely to yield highly fluoroquinolone-resistant mutants of E. coli and C. freundii in cats, possibly because of the high drug concentration in feces.

Resistance gene transfer during treatments for experimental avian colibacillosis

An experiment was conducted in animal facilities to compare the impacts of four avian colibacillosis treatments-oxytetracycline (OTC), trimethoprim-sulfadimethoxine (SXT), amoxicillin (AMX), or enrofloxacin (ENR)-on the susceptibility of Escherichia coli in broiler intestinal tracts. Birds were first orally inoculated with rifampin-resistant E. coli strains bearing plasmid genes conferring resistance to fluoroquinolones (qnr), cephalosporins (bla(CTX-M) or bla(FOX)), trimethoprim-sulfonamides, aminoglycosides, or tetracyclines. Feces samples were collected before, during, and after antimicrobial treatments. The susceptibilities of E. coli strains were studied, and resistance gene transfer was analyzed. An increase in the tetracycline-resistant E. coli population was observed only in OTC-treated birds, whereas multiresistant E. coli was detected in the dominant E. coli populations of SXT-, AMX-, or ENR-treated birds. Most multiresistant E. coli strains were susceptible to rifampin and exhibited various pulsed-field gel electrophoresis profiles, suggesting the transfer of one of the multiresistance plasmids from the inoculated strains to other E. coli strains in the intestinal tract. In conclusion, this study clearly illustrates how, in E. coli, "old" antimicrobials may coselect antimicrobial resistance to recent and critical molecules.

Estimation of transmission parameters of a fluoroquinolone-resistant Escherichia coli strain between pigs in experimental conditions

Antimicrobial resistance is of primary importance regarding public and animal health issues. Persistence and spread of resistant strains within a population contribute to the maintenance of a reservoir and lead to treatment failure. An experimental trial was carried out to study the horizontal transmission of a fluoroquinolone-resistant Escherichia coli strain from inoculated to naïve pigs. All naïve contact pigs had positive counts of fluoroquinolone-resistant E. coli after only two days of contact. Moreover, re-infections of inoculated pigs caused by newly contaminated animals were suspected. A maximum likelihood method, based on a susceptible-infectious-susceptible (SIS) model, was used to determine the transmission parameters. Two transmission levels were identified depending on the quantity of bacteria shed by infected individuals: (i) low-shedders with bacterial counts of resistant E. coli in the faeces between 5*10³ and 10⁶ CFU/g (β_L = 0.41 [0.27; 0.62]), (ii) high shedders with bacterial counts above 10⁶ CFU/g (β_H = 0.98 [0.59; 1.62]). Hence, transmission between animals could be pivotal in explaining the persistence of resistant bacteria within pig herds.

Effects of antimicrobial treatment on selection of resistant Escherichia coli in broiler fecal flora

Under field conditions, three commercial antimicrobials were sequentially prescribed to 16,000 broiler chickens during their rearing period, via drinking water using subtherapeutic levels for 3 days. A control group of 16,000 broilers was placed in the same controlled environment poultry house. Feed diet and fecal samples from both groups were collected periodically. One sample of the drinking water along with samples from the broiler house environment was also collected 1 day before bird placement. Samples were plated onto Tergitol BCIG Agar media; a maximum of 26 Escherichia coli were isolated per sample, and their susceptibility was tested to 12 antimicrobials by disk diffusion agar method. We have observed that day-old chicks were rapidly colonized by new antibiotic-resistant patterns shortly after treatment with lincomycin associated with spectinomycin. After medication with the second (sulfadiazine with trimethoprim) and third (tylosin) antimicrobials, a more radical displacement was observed, and, concurrently, antimicrobial resistance phenotypes have become more complex. In contrast, more than 70% of the strains isolated in control group during the experiment displayed exactly the same resistance pattern found in the day-old chicks. This study provides clear evidence that a sequential medication of a broiler flock, with different antimicrobial classes during short periods of time for prophylactic objectives, was accompanied by a dramatic increase in both antimicrobial resistance rates and phenotype diversity of E. coli strains.

Associations between feed and water antimicrobial use in farrow-to-finish swine herds and antimicrobial resistance of fecal Escherichia coli from grow-finish pigs

Escherichia coli (n = 1439), isolated from the feces of apparently healthy grow-finish pigs in 20 herds, were tested for susceptibility to 16 antimicrobials. Logistic regression models were developed for each resistance that was observed in more than 5% of the isolates. Each production phase's (suckling, nursery, grow-finish pigs or sows) antimicrobial exposure rate, through feed or water, was considered as a risk factor. Management variables were evaluated as potential confounders. Six resistance outcomes were associated with an antimicrobial use risk factor and four included exposures of pigs outside the grow-finish phase. In the case of sulfamethoxazole, the odds of resistance increased 2.3 times for every 100,000 pig-days of nursery pig exposure to sulfonamides. Thus, swine producers and veterinarians must be aware that antimicrobial use in pigs distant from market could have food safety repercussions. Five resistance outcomes were associated with exposure to an unrelated antimicrobial class. Most notably, the odds of sulfamethoxazole and chloramphenicol resistance were each six times higher in herds reporting high (more than 500/1,000 pig-days) grow-finish pig, macrolide exposure compared to herds with no macrolide use in grow-finish pigs. Therefore, the potential for co-selection should be considered in antimicrobial use decisions. This study emphasizes the importance of judicious antimicrobial use in pork production.

Risk factors for community-acquired urinary tract infection due to quinolone-resistant E. coli

BACKGROUND

Resistance to fluoroquinolone drugs is emerging among E. coli causing community acquired urinary tract infections (COMA-UTI).

OBJECTIVES

To evaluate demographic and clinical risk factors associated with COMA-UTI due to quinolone-resistant E. coli (QREc).

METHODS

In this case-control study, clinical and demographic data from 300 COMA-UTI due to E. coli (including 150 QREc) were analyzed.

RESULTS

By univariate analysis QREc was associated to males, older patients, nursing home residents, functionally dependent, dementia, diabetes, cardiovascular diseases, immunosupression, nephrolithiasis, recurrent UTI, invasive procedures, hospitalization, and antibiotic use within previous 6 months. By multivariate analysis, use of ciprofloxacin (OR 20.6 [CI 2.3-179.2], p=0.006) or ofloxacin (OR 7.5 [CI 2.9-19.4], p<0.0001), previous invasive procedure (OR 6.6 [CI 3.0-14.7], p<0.0001), recurrent UTI (OR 4.7 [CI 2.3-9.3], p<0.0001), and previous hospitalization (OR 2.9 [CI 1.4-6], p=0.003) were identified as independent risk factors for COMA-UTI due to QREc.

CONCLUSION

In patients with one or more of the risk factors identified here, the empiric use of quinolones should be reconsidered.

Impact of three ampicillin dosage regimens on selection of ampicillin resistance in Enterobacteriaceae and excretion of blaTEM genes in swine feces

The aim of this study was to assess the impact of three ampicillin dosage regimens on ampicillin resistance among Enterobacteriaceae recovered from swine feces by use of phenotypic and genotypic approaches. Phenotypically, ampicillin resistance was determined from the percentage of resistant Enterobacteriaceae and MICs of Escherichia coli isolates. The pool of ampicillin resistance genes was also monitored by quantification of bla(TEM) genes, which code for the most frequently produced beta-lactamases in gram-negative bacteria, using a newly developed real-time PCR assay. Ampicillin was administered intramuscularly and orally to fed or fasted pigs for 7 days at 20 mg/kg of body weight. The average percentage of resistant Enterobacteriaceae before treatment was between 2.5% and 12%, and bla(TEM) gene quantities were below 10(7) copies/g of feces. By days 4 and 7, the percentage of resistant Enterobacteriaceae exceeded 50% in all treated groups, with some highly resistant strains (MIC of >256 microg/ml). In the control group, bla(TEM) gene quantities fluctuated between 10(4) and 10(6) copies/g of feces, whereas they fluctuated between 10(6) to 10(8) and 10(7) to 10(9) copies/g of feces for the intramuscular and oral routes, respectively. Whereas phenotypic evaluations did not discriminate among the three ampicillin dosage regimens, bla(TEM) gene quantification was able to differentiate between the effects of two routes of ampicillin administration. Our results suggest that fecal bla(TEM) gene quantification provides a sensitive tool to evaluate the impact of ampicillin administration on the selection of ampicillin resistance in the digestive microflora and its dissemination in the environment.