These remarkably high coefficients indicate that, at a national level, the level of use of specific antimicrobials strongly correlates to the level of resistance towards these agents in commensal E. coli isolates in pigs, poultry and cattle. However, data restraints reveal the need for further detail in collection and harmonization of antimicrobial resistance and use data in Europe.

No abstract

No abstract

cFresh produce is known to carry nonpathogenic epiphytic microorganisms. During agricultural production and harvesting, leafy greens can become contaminated with antibiotic-resistant pathogens or commensals from animal and human sources. As lettuce does not undergo any inactivation or preservation treatment during processing, consumers may be exposed directly to all of the (resistant) bacteria present. In this study, we investigated whether lettuce or its production environment (irrigation water, soil) is able to act as a vector or reservoir of antimicrobial-resistant Escherichia coli. Over a 1-year period, eight lettuce farms were visited multiple times and 738 samples, including lettuce seedlings (leaves and soil), soil, irrigation water, and lettuce leaves were collected. From these samples, 473 isolates of Escherichia coli were obtained and tested for resistance to 14 antimicrobials. Fiftyfour isolates (11.4%) were resistant to one or more antimicrobials. The highest resistance rate was observed for ampicillin (7%), followed by cephalothin, amoxicillin-clavulanic acid, tetracycline, trimethoprim, and streptomycin, with resistance rates between 4.4 and 3.6%. No resistance to amikacin, ciprofloxacin, gentamicin, or kanamycin was observed. One isolate was resistant to cefotaxime. Among the multiresistant isolates (n ‫؍‬ 37), ampicillin and cephalothin showed the highest resistance rates, at 76 and 52%, respectively. E. coli isolates from lettuce showed higher resistance rates than E. coli isolates obtained from soil or irrigation water samples. When the presence of resistance in E. coli isolates from lettuce production sites and their resistance patterns were compared with the profiles of animal-derived E. coli strains, they were found to be the most comparable with what is found in the cattle reservoir. This may suggest that cattle are a potential reservoir of antimicrobial-resistant E. coli strains in plant primary production.

The aim of this study was to investigate the relationship between antimicrobial use and the occurrence of antimicrobial resistance in the digestive and respiratory tract in three different production systems of food producing animals. A longitudinal study was set up in 25 Belgian bovine herds (10 dairy, 10 beef, and 5 veal herds) for a 2 year monitoring of antimicrobial susceptibilities in E. coli and Pasteurellaceae retrieved from the rectum and the nasal cavity, respectively. During the first year of observation, the antimicrobial use was prospectively recorded on 15 of these farms (5 of each production type) and transformed into the treatment incidences according to the (animal) defined daily dose (TIADD) and (actually) used daily dose (TIUDD). Antimicrobial resistance rates of 4,174 E. coli (all herds) and 474 Pasteurellaceae (beef and veal herds only) isolates for 12 antimicrobial agents demonstrated large differences between intensively reared veal calves (abundant and inconstant) and more extensively reared dairy and beef cattle (sparse and relatively stable). Using linear mixed effect models, a strong relation was found between antimicrobial treatment incidences and resistance profiles of 1,639 E. coli strains (p<0.0001) and 309 Pasteurellaceae (p≤0.012). These results indicate that a high antimicrobial selection pressure, here found to be represented by low dosages of oral prophylactic and therapeutic group medication, converts not only the commensal microbiota from the digestive tract but also the opportunistic pathogenic bacteria in the respiratory tract into reservoirs of multi-resistance.

In this study the possible association between antibiotic use and resistance was explored, focusing on commensal Escherichia coli from livestock (veal calves, young beef cattle, pigs and broiler chickens) in Belgium between 2011 and 2015. A continuous decreasing trend in antibiotic use was observed for all classes, except for the phenicols. Antibiotic resistance of commensal E. coli significantly decreased for several of the tested antibiotics in all livestock species. A more rapidly reverted resistance was seen to 3th/4th generation cephalosporins and fluoroquinolones. Moderate to strong correlations between antibiotic use and resistance were found, except for antibiotic resistance to chloramphenicol and gentamicin and the use of the corresponding antibiotic class. Yet, total antibiotic use was positively correlated with chloramphenicol resistance, showing the potential importance of co-selection for chloramphenicol resistance. These results suggest that national antimicrobial usage reduction campaigns have beneficial effects on the overall resistance levels. Analyses were performed on small datasets, though, and care must be taken while making inference. For more detailed analysis, antibiotic use data at an animal species level are required.

This study investigated whether antimicrobial-resistant Escherichia coli in apparently healthy sows and antimicrobial administration to sows and piglets influenced antimicrobial resistance in fecal commensal E. coli from piglets. Sixty sows from three herds and three of their piglets were sampled at several time points. Antimicrobial usage data during parturition and farrowing were collected. Clinical resistance was determined for two isolates per sampling time point for sows and piglets using disk diffusion. Only 27.4% of E. coli isolates from newborn piglets showed no resistance. Resistance to one or two antimicrobial classes equaled 41.2% and 46.8% in isolates from sows and piglets, respectively, for the overall farrowing period. Multiresistance to at least four classes was found as frequently in sows (15.6%) as in piglets (15.2%). Antimicrobial resistance in piglets was influenced by antimicrobial use in sows and piglets and by the sow resistance level (p≤0.05). Using aminopenicillins and third-generation cephalosporins in piglets affected resistance levels in piglets (odds ratios [OR] >1; p≤0.05). Using enrofloxacin in piglets increased the odds for enrofloxacin resistance in piglets (OR=26.78; p≤0.0001) and sows at weaning (OR=4.04; p≤0.05). For sows, antimicrobial exposure to lincomycin-spectinomycin around parturition increased the resistance to ampicillin, streptomycin, trimethoprim-sulfadiazine in sows (OR=21.33, OR=142.74, OR=18.03; p≤0.05) and additionally to enrofloxacin in piglets (OR=7.50; p≤0.05). This study demonstrates that antimicrobial use in sows and piglets is a risk factor for antimicrobial resistance in the respective animals. Moreover, resistance determinants in E. coli from piglets are selected by using antimicrobials in their dam around parturition.

Streptococcus suis (S. suis) has often been reported as an important swine pathogen and is considered as a new emerging zoonotic agent. Consequently, it is important to be informed on its susceptibility to antimicrobial agents. In the current study, the Minimum Inhibitory Concentration (MIC) population distribution of nine antimicrobial agents has been determined for nasal S. suis strains, isolated from healthy pigs at the end of the fattening period from 50 closed or semiclosed pig herds. The aim of the study was to report resistance based on both clinical breakpoints (clinical resistance percentage) and epidemiological cutoff values (non-wild-type percentage). Non-wild-type percentages were high for tetracycline (98%), lincomycin (92%), tilmicosin (72%), erythromycin (70%), tylosin (66%), and low for florfenicol (0%) and enrofloxacin (0.3%). Clinical resistance percentages were high for tetracycline (95%), erythromycin (66%), tylosin (66%), and low for florfenicol (0.3%) and enrofloxacin (0.3%). For tiamulin, for which no clinical breakpoint is available, 57% of the isolates did not belong to the wild-type population. Clinical resistance and non-wild-type percentages differed substantially for penicillin. Only 1% of the tested S. suis strains was considered as clinically resistant, whereas 47% of the strains showed acquired resistance when epidemiological cutoff values were used. In conclusion, MIC values for penicillin are gradually increasing, compared to previous reports, although pigs infected with strains showing higher MICs may still respond to treatment with penicillin. The high rate of acquired resistance against tiamulin has not been reported before. Results from this study clearly demonstrate that the use of different interpretive criteria contributes to the extent of differences in reported antimicrobial resistance results. The early detection of small changes in the MIC population distribution of isolates, while clinical failure may not yet be observed, provides the opportunity to implement appropriate risk management steps. Introduction Streptococcus suis (S. suis) is an important swine pathogen affecting pigs of different ages, although susceptibility to the disease decreases with age after weaning. 4,36 It is known to cause meningitis, arthritis, septicemia, endocarditis, polyserositis, bronchopneumonia, and abortion, 4,23,36 but can also be found in the upper respiratory, alimentary, and urogenital tract of healthy pigs.4,22 S. suis has also been implicated in disease in humans, especially among people in close contact with swine and pork. 20,27 Moreover, S. suis has recently been reported as an emerging zoonotic pathogen evidenced by a few large-scale outbreaks of severe S. suis epidemics in Asia. 28,41,42 The most frequently applied treatment for pigs with clinical signs of S. suis infection is feed medication with antimicrobials, particularly, broad-spectrum penicillins. 9,19,37 Currently, no effective commercial vaccine is available. Prevention is based on the optimization of management, au...