Metaphylactic antimicrobial effects on occurrences of antimicrobial resistance in Salmonella enterica, Escherichia coli and Enterococcus spp. measured longitudinally from feedlot arrival to harvest in high-risk beef cattle

Effects of a Novel Direct-fed Microbial on Occurrences of Antimicrobial Resistance in Salmonella enterica, Escherichia coli, and Enterococcus spp. Measured Longitudinally From Feedlot Arrival to Harvest in Finishing Beef Steers

Before implementation of the Veterinary Feed Directive in 2017, medically important antimicrobials, like tylosin, were approved for both therapeutic and subtherapeutic use. Nevertheless, subtherapeutic practices are now considered injudicious because their use increases antimicrobial resistance risk. Therefore, heightened consumer concerns have increased the interest in antimicrobial alternatives like direct-fed microbials. Two-hundred forty Angus beef steers (mean initial BW = 263 kg ± 18.0 kg) were assigned randomly to one of three dietary treatments; negative control, dietary supplement contained no tylosin (NCON); positive control, dietary supplement contained tylosin (PCON); or novel direct-fed microbial fed at 1 g mixture/steer with 1 × 1011 CFU/g (DFM). Fecal samples were collected on days 0, 59, 128, and at study end. Pen and hide swabs were collected two days before harvest, and subiliac lymph nodes were collected on the day of harvest. All targeted bacterial populations differed across time (p ≤ 0.05), except 128ERYREscherichia coli. Fecal Salmonella concentration and prevalence differed among dietary treatments (p = 0.02) with NCON having greater fecal Salmonella concentrations than PCON and DFM. No differences in Salmonella prevalence among pen swabs, hide swabs, or subiliac lymph nodes were detected (p ≥ 0.40). Salmonella resistant to tetracycline or cefotaxime were not detected in feces. The effect of treatment differed by day for total and 128ERYREnterococcus spp. concentrations. Total Enterococcus spp. concentrations were greatest for the DFM treatment on day 128 and at study end (p ≤ 0.01). At study end, 128ERYREnterococcus spp. concentrations were greatest for PCON (p ≤ 0.01). Total, TETR, COTR, and CTXRE. coli concentrations increased from d 0 to study end among treatments (p ≤ 0.01). These data suggest that the in-feed inclusion of a novel direct-fed microbial is not directly implicated in the antimicrobial resistance of feedlot beef cattle.

Assessment of Antimicrobial Exposure on Generic Escherichia coli and Enterococcus spp. Concentration, Prevalence, and Resistance to Antimicrobials in Beef Cattle Raised with or Without Antimicrobials

The aim was to longitudinally evaluate the association between antimicrobial exposure and resistance occurrence within generic Escherichia coli and Enterococcus spp. populations in feedlot beef cattle raised conventionally or raised without antimicrobials. Angus steers (n = 180) were sorted into 1 of 2 treatments over 2 consecutive years (108 in yr 1 and 72 in yr 2): steers raised without antimicrobials (NAT) and conventionally raised steers exposed to antimicrobials (CONV). Pens within treatment were adjacent and separated by five empty pens from the other treatment. Monensin and tylosin were included in CONV steer diets. On d 123, CONV steers received a metaphylactic antimicrobial. Longitudinal diet (n = 6/year) and fecal (n = 5/year) sampling timepoints were collected to determine E. coli and Enterococcus spp. concentration, prevalence, and resistance patterns. Dietary Enterococcus spp. concentrations, and erythromycin (8ERYR; 128ERYR), tetracycline (TETR), trimethoprim-sulfamethoxazole (COTR), and cefotaxime (CTXR) resistant E. coli concentrations and prevalence were greater in NAT diets than CONV diets (p < 0.02). Fecal E. coli concentrations tended to be greater in NAT steers than CON steers (p = 0.07). Fecal TETR E. coli concentrations were greater in CONV steers than NAT steers (p = 0.03). Fecal COTR and CTXR E. coli prevalence was greater for CONV steers at the beginning of the finishing phase while greater for NAT steers at the end of the finishing phase (p < 0.01). Fecal Enterococcus spp. concentrations did not differ between treatments (p = 0.11). Concentrations of 8ERYR and 128ERYR Enterococcus spp. were greater in CONV steers on d 64, 130, and 168 than NAT steers (p < 0.05). Overall, antimicrobial resistant Enterococcus spp. and E. coli were detected regardless of antimicrobial exposure.

An analysis of culture-based methods used for the detection and isolation of Salmonella spp., Escherichia coli, and Enterococcus spp. from surface water: A systematic review

Identification of methods for the standardized assessment of bacterial pathogens and antimicrobial resistance (AMR) in environmental water can improve the quality of monitoring and data collected, support global surveillance efforts, and enhance the understanding of environmental water sources. We conducted a systematic review to assemble and synthesize available literature that identified methods for assessment of prevalence and abundance of bacterial fecal indicators and pathogens in water for the purposes of monitoring bacterial pathogens and AMR. After screening for quality, 175 unique publications were identified from 15 databases, and data were extracted for analysis. This review identifies the most common and robust methods, and media used to isolate target organisms from surface water sources, summarizes methodological trends, and recognizes knowledge gaps. The information presented in this review will be useful when establishing standardized methods for monitoring bacterial pathogens and AMR in water in the United States and globally.

Weaning transition, but not the administration of probiotic candidate Kazachstania slooffiae, shaped the gastrointestinal bacterial and fungal communities in nursery piglets

As in-feed antibiotics are phased out of swine production, producers are seeking alternatives to facilitate improvements in growth typically seen from this previously common feed additive. Kazachstania slooffiae is a prominent commensal fungus in the swine gut that peaks in relative abundance shortly after weaning and has beneficial interactions with other bacteriome members important for piglet health. In this study, piglets were supplemented with K. slooffiae to characterize responses in piglet health as well as fungal and bacterial components of the microbiome both spatially (along the entire gastrointestinal tract and feces) and temporally (before, during, and after weaning). Litters were assigned to one of four treatments: no K. slooffiae (CONT); one dose of K. slooffiae 7 days before weaning (day 14; PRE); one dose of K. slooffiae at weaning (day 21; POST); or one dose of K. slooffiae 7 days before weaning and one dose at weaning (PREPOST). The bacteriome and mycobiome were analyzed from fecal samples collected from all piglets at day 14, day 21, and day 49, and from organ samples along the gastrointestinal (GI) tract at day 21 and day 49. Blood samples were taken at day 14 and day 49 for cytokine analysis, and fecal samples were assayed for antimicrobial resistance. While some regional shifts were seen in response to K. slooffiae administration in the mycobiome of the GI tract, no remarkable changes in weight gain or health of the animals were observed, and changes were more likely due to sow and the environment. Ultimately, the combined microbiome changed most considerably following the transition from suckling to nursery diets. This work describes the mycobiome along the piglet GI tract through the weaning transition for the first time. Based on these findings, K. slooffiae administered at this concentration may not be an effective tool to hasten colonization of K. slooffiae in the piglet GI tract around the weaning transition nor support piglet growth, microbial gut health, or immunity. However, diet and environment greatly influence microbial community development.

Dynamics of Extended-spectrum Beta-lactamase-producing, Third-generation Cephalosporin-resistant and Tetracycline-resistant Escherichia coli in Feedlot Cattle With or Without Tylosin Administration

The impact of in-feed use of tylosin in feedlot cattle on Gram-negative foodborne bacteria is unknown. We evaluated the effect of continuous in-feed tylosin use on the concentration and prevalence of tetracycline-resistant (TETr)-, third-generation cephalosporin-resistant (3GCr)-, and extended-spectrum β-lactamase-producing (ESBLs) E. coli in feedlot cattle. A cohort of weaned calves (10 animals/group) were randomized to receive a feed ration with or without tylosin. Fecal samples, regularly collected over the entire feeding period, and pen surface and feed samples, collected at the end of the feeding period, were cultured on selective media. Enumeration and binary outcomes were analyzed by mixed effects linear regression or logistic regression, respectively, using treatment and days on feed as fixed factors, and animal ID as a random variable. Tylosin supplementation did not affect the fecal concentrations of TETrE. coli or fecal prevalence of 3GCrE. coli. However, cattle in the tylosin group were 1.5 times more likely (Odds ratio = 1.5: 95% confidence interval: 1.1-2.0) to harbor ESBLs E. coli than the control cattle. Regardless of tylosin treatment, fecal concentrations of TETrE. coli and the prevalence of 3GCr- and ESBLs-E. coli increased over time. Tylosin-supplemented feed did not affect the prevalence of TETrE. coli; 3GCr and ESBLs-E. coli were not detected from the feed samples. Most of the 3GCr- and ESBLs-E. coli isolates carried the blaCTX-M-15 gene, widely detected among ESBLs-E. coli human isolates. In summary, although in-feed tylosin use in feedlot cattle did not select for TETr- and 3GCr-E. coli, it increased the likelihood of detecting ESBL-producing E. coli. Furthermore, the study indicated that the feedlot production setting gradually increases the levels of E. coli resistant to the critically and/or important antibiotics for public health, indicating an increased risk of their dissemination beyond the feedlot environment.

Longitudinal Assessment of Prevalence and Incidence of Salmonella and Escherichia coli O157 Resistance to Antimicrobials in Feedlot Cattle Sourced and Finished in Two Different Regions of the United States

The objective was to investigate the influence of cattle origin and region of finishing on the prevalence of Salmonella, Escherichia coli O157:H7, and select antimicrobial resistance in E. coli populations. Yearling heifers (n = 190) were utilized in a 2 × 2 factorial arrangement. After determining fecal Salmonella prevalence, heifers were sorted into one of four treatments: heifers originating from South Dakota (SD) and finished in SD (SD-SD); heifers originating from SD and finished in Texas (SD-TX); heifers originating from TX and finished in SD (TX-SD); and heifers originating from TX and finished in TX (TX-TX). Fecal, pen, and water scum line samples were collected longitudinally throughout the study; hide swab and subiliac lymph node (SLN) samples were collected at study end. A treatment × time interaction was observed (p ≤ 0.01) for fecal Salmonella prevalence, with prevalence being greatest for TX-TX and TX-SD heifers before transport. From day (d) 14 through study end, prevalence was greatest for TX-TX and SD-TX heifers compared with SD-SD and TX-SD heifers. Salmonella prevalence on hides were greater (p ≤ 0.01) for heifers finished in TX compared with SD. Salmonella prevalence in SLN tended (p = 0.06) to be greater in TX-TX and SD-TX heifers compared with TX-SD and SD-SD. Fecal E. coli O157:H7 prevalence had a treatment × time interaction (p = 0.04), with SD-TX prevalence being greater than TX-SD on d 56 and SD-SD and TX-TX being intermediate. A treatment × time interaction was observed for fecal trimethoprim-sulfamethoxazole-resistant and cefotaxime-resistant E. coli O157:H7 prevalence (p ≤ 0.01). Overall, these data suggest that the region of finishing influences pathogenic bacterial shedding patterns, with the initial 14 d after feedlot arrival being critical for pathogen carriage.

The Coexistence of Bacterial Species Restructures Biofilm Architecture and Increases Tolerance to Antimicrobial Agents

Chronic infections caused by polymicrobial biofilms are often difficult to treat effectively, partially due to the elevated tolerance of polymicrobial biofilms to antimicrobial treatments. It is known that interspecific interactions influence polymicrobial biofilm formation. However, the underlying role of the coexistence of bacterial species in polymicrobial biofilm formation is not fully understood. Here, we investigated the effect of the coexistence of Enterococcus faecalis, Escherichia coli O157:H7, and Salmonella enteritidis on triple-species biofilm formation. Our results demonstrated that the coexistence of these three species enhanced the biofilm biomass and led to restructuring of the biofilm into a tower-like architecture. Furthermore, the proportions of polysaccharides, proteins, and eDNAs in the extracellular matrix (ECM) composition of the triple-species biofilm were significantly changed compared to those in the E. faecalis mono-species biofilm. Finally, we analyzed the transcriptomic profile of E. faecalis in response to coexistence with E. coli and S. enteritidis in the triple-species biofilm. The results suggested that E. faecalis established dominance and restructured the triple-species biofilm by enhancing nutrient transport and biosynthesis of amino acids, upregulating central carbon metabolism, manipulating the microenvironment through "biological weapons," and activating versatile stress response regulators. Together, the results of this pilot study reveal the nature of E. faecalis-harboring triple-species biofilms with a static biofilm model and provide novel insights for further understanding interspecies interactions and the clinical treatment of polymicrobial biofilms. IMPORTANCE Bacterial biofilms possess distinct community properties that affect various aspects of our daily lives. In particular, biofilms exhibit increased tolerance to chemical disinfectants, antimicrobial agents, and host immune responses. Multispecies biofilms are undoubtedly the dominant form of biofilms in nature. Thus, there is a pressing need for more research directed at delineating the nature of multispecies biofilms and the effects of the properties on the development and survival of the biofilm community. Here, we address the effects of the coexistence of Enterococcus faecalis, Escherichia coli, and Salmonella enteritidis on triple-species biofilm formation with a static model. In combination with transcriptomic analyses, this pilot study explores the potential underlying mechanisms that lead to the dominance of E. faecalis in triple-species biofilms. Our findings provide novel insights into the nature of triple-species biofilms and indicate that the composition of multispecies biofilms should be a key consideration when determining antimicrobial treatments.