Effect of continuous in-feed administration of tylosin to feedlot cattle on macrolide and tetracycline resistant enterococci in a randomized field trial.

Liver abscess causes substantial economic loss to the beef cattle industry through liver condemnation, reduced animal performance, and carcass yield. Continuous in-feed use of tylosin is the most effective and a commonly used practice in beef cattle production to prevent liver abscess. However, such mass medication can increase the level of antimicrobial resistant bacteria. We investigated the effect of continuous in-feed use of tylosin in feedlot cattle on (i) concentrations and prevalence of erythromycin-resistant (ERYr) and tetracycline-resistant (TETr) enterococci; (ii) associated antimicrobial resistance genes (ARGs) for resistance; (iii) species distribution; iv) macrolide and tetracycline resistance gene concentrations; and (v) tylosin concentration. A cohort of weaned calves were randomized to receive tylosin-medicated feed (Tylosin; n = 10) or nonmedicated feed (Control; n = 10) for a full feedlot cycle. Feces, feed and pen-surface samples were collected and processed by culture, droplet digital PCR, and liquid chromatography/mass spectroscopy for bacterial enumeration, detection and characterization, ARG quantification, and tylosin concentration, respectively. Data were analyzed by mixed effects linear- or binary-regression models depending on the outcomes. Tylosin administration significantly increased fecal concentration (P < 0.001) and prevalence (P = 0.021) of ERYr enterococci and erm(B) gene concentration (P < 0.001), compared to the control group. Interestingly, tylosin administration significantly reduced (P = 0.037) fecal TETr enterococci concentration compared to the control group, with no significant effect (P = 0.758) on fecal tet(M) concentration. In both treatment groups, enterococci concentrations increased over time, peaking on 174 days in feed before returning to the baseline. ERYr enterococci concentration was significantly (P = 0.012) higher in tylosin medicated feeds, with no significant effect (P = 0.321) on TETr enterococci concentration. Pen-surface concentration of ermB was significantly (P = 0.024) higher in the tylosin group, with no significant effect (P > 0.05) on bacterial concentrations. Increased diversity and a shift in the composition of enterococcal species and ARGs were observed over time, although tylosin use did not significantly affect (P > 0.05) their prevalence. Tylosin concentration was significantly higher in the feces of tylosin administered cattle (P < 0.001) and medicated feed (P = 0.027), with numerically higher pen-surface concentration (P = 0.065) in the tylosin group. In conclusion, continuous in-feed use of tylosin in feedlot cattle increases macrolide resistant enterococci and its fecal excretion, while decreasing tetracycline resistance. Two medically important species, E. faecium and E. faecalis, were predominant regardless of resistance status or sample source. Risk-based approaches including label changes to limit tylosin use such as withdrawal period, and development of effective manure treatments are potential areas of research to reduce environmental and public health impacts.

Lagoon, Anaerobic Digestion, and Composting of Animal Manure Treatments Impact on Tetracycline Resistance Genes.

Increased demand for animal protein is met by increased food animal production resulting in large quantities of manure. Animal producers, therefore, need sustainable agricultural practices to protect environmental health. Large quantities of antimicrobials are used in commercial food animal production. Consequently, antimicrobial-resistant bacteria and the resistance genes emerge and are excreted through feces. Manure management is essential for the safe disposal of animal waste. Lagoons, with or without covers, and anaerobic digesters, with the primary purpose of methane production, and composting, with the primary purpose of producing organic fertilizer, are widely used methods of manure treatment. We reviewed manure management practices and their impact on tetracycline resistance genes. Lagoons are maintained at ambient temperatures; especially uncovered lagoons are the least effective in removing tetracycline resistance genes. However, some modifications can improve the performance of lagoons: sequential use of uncovered lagoons and the use of covered lagoons resulted in a one-log reduction, while post-treatments such as biofiltration following covered lagoon treatment resulted in 3.4 log reduction. Mesophilic digestion of animal manure did not have any significant effect; only a 0.7 log reduction in tet(A) was observed in one study. While thermophilic anaerobic digesters are effective, if properly operated, they are expensive for animal producers. Aerobic thermophilic composting is a promising technology if optimized with its economic benefits. Composting of raw animal manure can result in up to a 2.5 log reduction, and postdigestion composting can reduce tetracycline resistance gene concentration by >80%. In general, manure management was not designed to mitigate antimicrobial resistance; future research is needed to optimize the economic benefits of biogas or organic fertilizer on the one hand and for the mitigation of foodborne pathogens and antimicrobial resistance on the other.

Association between 318C/T polymorphism of the CTLA-4 gene and systemic lupus erythematosus in Iranian patients.

BACKGROUND: Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is an important negative regulator of T-cell response. It is a functional candidate gene connected with susceptibility to systemic lupus erythematosus (SLE). We analyzed the role of -318C/T polymorphism in the promoter region of the CTLA-4 gene in Iranian patients suffering from SLE. METHODS: A total of 180 SLE patients and 304 healthy ethnically matched controls were enrolled in the study. DNA was extracted from blood samples according to the standard procedure. Polymerase chain reaction restriction fragments length polymorphism (PCR-RFLP) was used to analyze the genotype and allele frequencies of these polymorphisms. RESULTS: The CC genotype was observed in 170 (94.5%) of the SLE patients, which was significantly different compared to the controls (251 [82.4%]; P = 0.0001, OR = 3.51 95%CI = 1.77-7.53). T allele was significantly more common in the controls (9.2%) compared to SLE patients 2.8% (P = 0.0001, OR = 0.26, 95%CI = 0.13-0.53). There was no significant correlation between different genotypes and age, gender or family history of SLE in the studied population. CONCLUSION: It can be concluded that -318C/T polymorphism of CTLA-4 gene might play a significant role in the development of SLE in the Iranian patients.

Synthesis, characterization, and application of m-phenylendiamine-modified Amberlite XAD-4 resin for preconcentration and determination of metal ions in water samples.

A new chelating resin is prepared by coupling Amberlite XAD-4 (Serva, Heidelberg, New York) with m-phenylendiamine through an azo spacer, characterized (by elemental analysis, infrared, and thermogravimetric analysis) and studied for preconcentrating nickel(II), cobalt(II), zinc(II), copper(II), and chromium(III) using flame atomic absorption spectrometry for metal monitoring. The optimum pH values for sorption of the above-mentioned metal ions were 8.5, 8.5, 6.5, 6.5, and 5.5, respectively. The resin was subjected to evaluation through batch binding and column chromatography of the mentioned metal ions. Quantitative desorption occurred instantaneously with 0.5 M HNO3. Various flowrates of sorption and desorption of nickel(II) have been studied. The sorption capacity was found to be 3.89, 3.27, 2.96, and 3.44 mmol/g of resin for cobalt, copper, zinc, and nickel, respectively. The chelating resin can be reused for 10 cycles of sorption-desorption without any significant change in sorption capacity. A recovery of >98% was obtained for all the metal ions, with 0.5 M HNO3 as the eluting agent. The method was applied for determination of metal ions from an industrial wastewater sample.