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 ß-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.

Antibiotics promote abdominal fat accumulation in broilers.

Antibiotics stimulate the growth of animals but result in drug residues and bacterial resistance. In this study, the negative effect of antibiotics on abdominal fat deposition was evaluated in broilers. The results showed that adding both chlortetracycline (50 g/1,000 kg) and tylosin (50 g/1,000 kg) significantly increased abdominal fat weight, abdominal fat percentage (p < .05), and triglyceride and cholesterol levels (p < .05) in blood. Also, both products synchronously stimulated intestinal absorption and synthesis of liver fat. The expression levels of the peroxisome proliferator-activated receptor Î³ (PPARγ), diacylgycerol acyltransferase 2 (DGAT2), lipoprotein lipase (LPL), and fatty acid-binding protein (FABP4) genes in abdominal fat tissue significantly increased (p < .05 or 0.01) when antibiotics were added to the feed. However, no significant difference was found in expression of the fatty acid synthesis (FAS) or acetyl CoA carboxylase (ACC) genes. Further in vitro study results revealed that antibiotics had no effect on fat content or the related gene expression levels in preadipocytes. In summary, the antibiotics induced fat deposition in adipose tissues by activating extracellular absorption of fatty acids from intestinal absorption and synthesis of liver fat. However, it shows no direct regulation by adipose tissue.

Protective effect of ghrelin against tilmicosin-induced left ventricular dysfunction in rats.

This study was conducted to investigate the possible protective effects of ghrelin against tilmicosin-induced acute ventricular dysfunction in rats. Forty adult male Sprague Dawley rats were randomly divided into 4 equal groups: control, ghrelin, tilmicosin, and ghrelin + tilmicosin. The left ventricular structural and functional parameters together with cardiac biomarker levels were evaluated. The results showed that tilmicosin treatment alone significantly decreased the left ventricular fractional shortening, left ventricular ejection fraction, left ventricular stroke volume, and cardiac output when compared with control group. In addition, tilmicosin led to a significant increase in left ventricular internal dimension in systole and left ventricular fractional end-systolic volume. At the same time, serum lactate dehydrogenase, creatine kinase, and creatine kinase-myocardial B fraction levels were significantly increased in tilmicosin-treated group when compared with control group. However, ghrelin pretreatment significantly prevented the left ventricular internal dimension in systole, left ventricular fractional end-systolic volume, left ventricular stroke volume, left ventricular ejection fraction, left ventricular fractional shortening, and cardiac output changes caused by tilmicosin. Moreover, ghrelin pretreatment could reduce significantly serum lactate dehydrogenase, creatine kinase, and creatine kinase-myocardial B fraction levels. These data indicated that ghrelin treatment may provide a protective effect against tilmicosin-induced left ventricular systolic dysfunction.

Investigating the potential role of vitamin E in modulating the immunosuppressive effects of tylvalosin and florfenicol in broiler chickens.

Tylvalosin (TVS) is a third-generation macrolide drug used for prophylaxis and treatment of mycoplasma, however; it is supposed to possess an immunosuppressive effect. In the current study, the immunosuppressive effect of TVS and florfenicol (FFC) and the potential immunomodulatory role of Vit E were investigated. The experiment included one day old chick groups treated with either TVS, FFC, Vit E, TVS/Vit E, FFC/Vit E and control non-treated group. Chicks were vaccinated with inactivated H9N2 avian influenza (AI) vaccine and humoral antibody titers to viral antigen as well as innate immunity (serum lysozyme activity and nitric oxide levels) were evaluated. Total and differential leucocytic counts, serum liver enzymes level, blood leucocytic DNA damage and cellular area percentages within the lymphoid organs were also screened. Treatment with TVS and FFC significantly decreased immune response of chickens while treatment with Vit E improved the humoral immune response at 4 and 5weeks post-vaccination. Vit E also significantly increased the cellular immune response. The combination of Vit E with either TVS or FFC modulated their immunosuppressive effect and resulted in mild immunostimulatory effects. TVS alone induced a genotoxic effect on chickens' blood leucocytes and the genotoxicity was inhibited by combination of TVS with Vit E. Histopathology revealed that chickens treated with either TVS or FFC exhibited toxic effect on the lymphatic tissues.

Microbiological toxicity of tilmicosin on human colonic microflora in chemostats.

To evaluate the microbiological safety of tilmicosin on human intestinal microflora, four chemostat models of healthy human colonic ecosystems were exposed to tilmicosin (0, 0.436, 4.36, and 43.6 µg/mL) for 7 days. Prior to and during drug exposure, three microbiological endpoints were monitored daily including short-chain fatty acids, bacterial counts and macrolide susceptibility. Colonization resistance of each community was determined by 3 successive daily challenges of Salmonella typhimurium. Genes associated with virulence and macrolide resistance in Enterococcus faecalis were determined by PCR. Transcriptional expression of the virulence gene (gelE) in E. faecalis was determined by real-time RT-PCR. Our results showed that different concentrations of tilmicosin did not disrupt the colonization resistance in each chemostat. During exposure to 4.36 and 43.6 µg/mL tilmicosin, the Bacteroides fragilis population was significantly decreased while the proportion of resistant Enterococci increased. After long-term exposure to the highest concentration (43.6 µg/mL) of tilmicosin, the gelE gene was significantly up-regulated in the high-level macrolide resistant strains that also contained the ermB resistance gene. This study was the first of its kind to evaluate the microbiological toxicity of tilmicosin using a chemostat model. These findings also provide new insight into the co-occurrence of macrolide resistance and virulence in E. faecalis under tilmicosin selective pressure.

Airborne allergic contact dermatitis from tylosin in pharmacy compounders and cross-sensitization to macrolide antibiotics.

Tylosin is a broad-spectrum macrolide antibiotic that is restricted to veterinary use. Allergic contact dermatitis (ACD) caused by tylosin has been reported in the literature from the farming industry and veterinary medicine. It is also reported as the most common antibiotic to cause ACD in the previously mentioned occupational settings. We present 2 cases of airborne ACD from tylosin among veterinary pharmaceutical compounding technicians. To our knowledge, only one other case of patch test-confirmed tylosin ACD has been reported in the manufacturing setting. Based on our results, cross-sensitization to other clinically relevant macrolides does not appear to be a concern. Our cases highlight the importance of patch testing among pharmaceutical compounders where the incidence of an airborne contact may be greater, given that the exposure is to the powdered form of potential allergens.

Biochemical effects of veterinary antibiotics on proliferation and cell cycle arrest of human HEK293 cells.

The purpose of this study was to examine the effects of veterinary antibiotics, including amoxicillin (AMX), chlortetracycline (CTC) and tylosin (TYL), on the biochemical mechanism of human embryonic kidney cells (HEK293). CTC and TYL inhibited HEK293 cell proliferation, in both time- and dose-dependent manners, and changed the cell morphology; whereas, AMX showed no cytotoxic effects. The cell cycle analysis of CTC and TYL revealed G1-arrest in HEK293 cells. Western blot analysis also showed that CTC and TYL affected the activation of DNA damage responsive proteins, as well as cell cycle regulatory proteins, such as p53, p21(Waf1/Cip1) and Rb protein, which are crucial in the G1-S transition. The activation of p21(Waf1/Cip1) was significantly up-regulated over time, but there was no change in the level of CDK2 expression. The results of this study suggest that veterinary antibiotics, even at low level concentrations on continuous exposure, can potentially risk the development of human cells.

Human health hazards of veterinary medications: information for emergency departments.

BACKGROUND: There are over 5000 approved prescription and over-the-counter medications, as well as vaccines, with labeled indications for veterinary patients. Of these, there are several products that have significant human health hazards upon accidental or intentional exposure or ingestion in humans: carfentanil, clenbuterol (Ventipulmin), ketamine, tilmicosin (Micotil), testosterone/estradiol (Component E-H and Synovex H), dinoprost (Lutalyse/Prostamate), and cloprostenol (Estromate/EstroPlan). The hazards range from mild to life-threatening in terms of severity, and include bronchospasm, central nervous system stimulation, induction of miscarriage, and sudden death. OBJECTIVE: To report medication descriptions, human toxicity information, and medical management for the emergent care of patients who may have had exposure to veterinary medications when they present to an emergency department (ED). DISCUSSION: The intended use of this article is to inform and support ED personnel, drug information centers, and poison control centers on veterinary medication hazards. CONCLUSION: There is a need for increased awareness of the potential hazards of veterinary medications within human medicine circles. Timely reporting of veterinary medication hazards and their medical management may help to prepare the human medical community to deal with such exposures or abuses when time is of the essence.

Adverse outcome of using tilmicosin in a lamb with multiple ventricular septal defects.

A 15-day-old, 6.08 kg, lamb was injected subcutaneously with tilmicosin 15 mg/kg body weight. Approximately 15 min later, the lamb died. During necropsy, the heart was found to have multiple ventricular septal defects. Death was attributed to sudden heart failure due to the cardiac effects of tilmicosin in a heart having congenital defects.

Effectiveness of tilmicosin against Paenibacillus larvae, the causal agent of American Foulbrood disease of honeybees.

American Foulbrood (AFB) of honeybees (Apis mellifera L.), caused by the Gram-positive bacterium Paenibacillus larvae is one of the most serious diseases affecting the larval and pupal stages of honeybees (A. mellifera L.). The aim of the present work was to asses the response of 23 strains of P. larvae from diverse geographical origins to tilmicosin, a macrolide antibiotic developed for exclusive use in veterinary medicine, by means of the minimal inhibitory concentration (MIC) and the agar diffusion test (ADT). All the strains tested were highly susceptible to tilmicosin with MIC values ranging between 0.0625 and 0.5 microg ml(-1), and with MIC(50) and MIC(90) values of 0.250 microg ml(-1). The ADT tests results for 23 P. larvae strains tested showed that all were susceptible to tilmicosin with inhibition zones around 15 microg tilmicosin disks ranging between 21 and 50mm in diameter. Oral acute toxicity of tilmicosin was evaluated and the LD(50) values obtained demonstrated that it was virtually non-toxic for adult bees and also resulted non-toxic for larvae when compared with the normal brood mortality. Dosage of 1000 mg a.i. of tilmicosin applied in a 55 g candy resulted in a total suppression of AFB clinical signs in honeybee colonies 60 days after initial treatment. To our knowledge, this is the first report of the effectiveness of tilmicosin against P. larvae both in vitro and in vivo.

Technical note: Occurrence in fecal microbiota of genes conferring resistance to both macrolide-lincosamide-streptogramin B and tetracyclines concomitant with feeding of beef cattle with tylosin.

Development of antimicrobial resistance in food animals receiving antimicrobials has been well documented among bacterial isolates, especially pathogens, but information on development of antimicrobial resistance at the microbial community level during long-term feeding of antimicrobials is lacking. The objective of this study was to examine the association between inclusion of tylosin in feed and occurrence of resistance to macrolide-lincosamide-streptogramin B (MLS(B)) in the entire fecal microbial communities of beef cattle over a feeding study of 168 d. A completely randomized design included 6 pens housed together in 1 barn, with each pen housing 10 to 11 steers. The control and tylosin groups each had 3 pens, with the former receiving no antimicrobial whereas the latter received both tylosin and monensin (11 and 29.9 mg/ kg of feed, respectively, DM) in feed. The abundance of genes conferring resistance to MLS(B) (erm genes) and tetracyclines (tet genes) were quantified using class-specific, real-time PCR assays. The abundances of erm and tet genes were analyzed with pens as experimental units using the MIXED procedure of SAS. Correlations between abundance of different resistance genes were calculated using the CORR procedure of SAS. We identified 4 classes (B, F, T, and X) of erm genes in fresh fecal samples collected at wk 2, 17, and 21 of feeding. From wk 2 to 17, the abundance of erm(T) and erm(X) increased (P < 0.05), whereas that of erm(B) and erm(F) did not. The abundance of the erm genes did not further change from wk 17 to 21. The tet(A/C), tet(G), and tet gene variants encoding ribosomal protection proteins (including classes M, O, P, Q, S, T, and W) appeared to be co-selected by tylosin feeding. Such co-selection of multiresistance at community level by one antimicrobial drug used in animals has the important implication that future studies should examine resistance to not only the antimicrobials used in animals, but also other antimicrobials, especially those used in human medicine, to fully assess the potential risk associated with antimicrobial use in animals. Both the erm and tet genes appeared to be disseminated among the microbial populations in all steers housed together.

Development of macrolide-resistant Campylobacter in broilers administered subtherapeutic or therapeutic concentrations of tylosin.

The use of antimicrobials in food animal production, particularly those commonly used to treat infections in humans, has become a source of debate in recent years. However, limited data are available regarding the development of resistance following the subtherapeutic or therapeutic administration of antimicrobials in animal production. The objective of this study was to evaluate the effect of the administration of therapeutic and subtherapeutic concentrations of tylosin on the erythromycin susceptibility of Campylobacter jejuni and Campylobacter coli isolated from the ceca of treated broilers. In three replicated studies, day-of-hatch chicks were exposed to macrolide-susceptible C. jejuni or C. coli. At 2 weeks of age, tylosin was administered at subtherapeutic (22 ppm, continuously in the diet) or therapeutic concentrations (529 ppm, in the drinking water for 5 days). Broilers were sacrificed weekly. Total and erythromycin-resistant Campylobacter spp. were enumerated from individual ceca plus cecal contents. Overall erythromycin resistance was observed at a higher frequency (P < 0.01) among C. coli isolates (70.8%) than among C. jejuni isolates (36.8%) following tylosin administration. Across Campylobacter species, erythromycin resistance was observed at a higher frequency (P < 0.001) when tylosin was administered at subtherapeutic (62.7%) than at therapeutic (11.4%) concentrations. Subtherapeutic administration resulted in the recovery of 83.3 and 56.1% erythromycin-resistant isolates compared with only 33.3 and 7.9% of the isolates expressing erythromycin resistance following the administration of therapeutic concentrations for C. coli and C. jejuni, respectively. Further studies are needed to determine the factors involved in the apparent difference in the acquisition of macrolide resistance in C. coli compared with C. jejuni.

Eczema de contacto alérgico por tilosina en un criador de canarios / Allergic contact eczema from tylosin in a canary breeder

Las personas dedicadas a la cría de animales entran en contacto con múltiples sustancias añadidas a los piensos. Algunas de ellas pueden dar lugar a dermatitis de contacto. Se presenta el caso de un paciente aficionado a la cría de canarios que desarrolló una dermatitis de contacto alérgica secundaria a tilosina, un antibiótico macrólido de amplio espectro muy utilizado en veterinaria (AU)

[Analysis of immunological indices of occupational sensibilization to tylosin]. / Analiz immunologicheskikh pokazatelei professional'noi sensibilizatsii k tilozinu.

The authors studied sensibilization to antibiotic Tilosine and determined several immunologic parameters in Tilosine production workers, searching for criteria of the sensibilization's occupational etiology. The results prove that skin allergic reactivity, antibodies production and lymphocytes proliferation response are diagnostic for immune changes in workers exposed to occupational allergens and useful for assessing risk of allergic disorders.

Accidental veterinary antibiotic injection into a farm worker.

A 29-year-old white male farm worker accidentally injected tilmicosin, a bovine antibiotic, into his finger. He developed temporary pulmonary, gastrointestinal, and neuromuscular symptomatology and a more persistent subjective asthenia.