In a second step, we aimed to investigate whethertet(C) PCR from clinical swabs yielded similar results. Interestingly, out FOXO3 of 32 isolated samples positive fortet(C), only 16 corresponding clinical swabs were positive resulting in a sensitivity of only 50% and a negative predictive value of 62. 8% for clinical swabs. rate from fecal swabs compared to conjunctival swabs. The farms were divided into three treatment groups: A) farms without antibiotic treatment, B) farms Captopril with prophylactic oral antibiotic treatment of the whole herd consisting of trimethoprime, sulfadimidin and sulfathiazole (TSS), or C) farms giving herd treatment with chlortetracycline with or without tylosin and sulfadimidin (CTS). 59 isolates and their corresponding clinical samples were selected and tested for the presence or absence of the tetracycline resistance class C gene [tet(C)] by conventional PCR and isolates were further investigated for their antibiotic susceptibilityin vitro. The phenotype of the investigated isolates was either classified as tetracycline sensitive (Minimum inhibitory concentration [MIC] < 2 g/ml), intermediate (2 g/ml MIC < 4 g/ml) or resistant (MIC 4 g/ml). Results of groups and individual pigs were correlated with antibiotic treatment and time of sampling (beginning/end of the fattening period). We found clear evidence for selective pressure as absence of antibiotics led to isolation of only tetracycline sensitive or intermediate strains whereas tetracycline treatment resulted in a greater number of tetracycline resistant isolates. == Introduction == Since the 1940s, antibiotics have been prescribed in human and veterinary medicine to treat bacterial infection, Captopril but only a few years after discovery of these antimicrobial drugs, the first cases of acquired antibiotic resistance emerged in the form of penicillin-resistantStaphylococcus aureus[1]. Antibiotic resistance as a result of chromosomal mutation or acquisition of resistance genes is promoted by numerous factors including a) the use of sub-inhibitory antimicrobial concentrations (during treatment, as preventive measures or as growth promoters in livestock), b) the use of broad-spectrum antibiotics, and c) non-compliance of individuals and communities under treatment. Moreover, there is a positive correlation between the frequency of antibiotic treatment and the occurrence of resistance [2]. Taken together, the use of antibiotics exerts selective pressure against the microbial community promoting the emergence of therapy-resistant bacteria [3]. However , selective pressure does not only concern pathogens. Complex microbial ecosystems, in particular the microbiota of the gastrointestinal tract, have been reported to regularly acquire and transfer antibiotic resistance genes, often promoted by the use of oral antimicrobial drugs. With high bacterial loads of 1011to 1012bacteria/ml from several phyla, the colon offers plenty of opportunity for horizontal gene transfer and the selection for commensal bacteria resistant to antibiotics [4, 5]. Of particular interest in this wide range of commensal and opportunistic bacteria is the speciesChlamydia suis, which is primarily found in the gastrointestinal tract of pigs and was the first obligate intracellular bacterium reported to have acquired stable tetracycline resistance through horizontal gene transfer [6, 7]. C. suisbelongs to theChlamydiaceae, a family of Gram-negative bacteria which also Captopril includesC. trachomatis, the leading cause of sexually transmitted bacterial disease worldwide as well as the Captopril causing agent of blinding trachoma [8]. Despite its high prevalence Captopril in pigs, with up to 94. 2% in farms, C. suisis not considered a primary pathogen for pigs, but it has been associated with several disease complexes including conjunctivitis as well as reproductive disorders, and cases of diarrhea within the herd related to a highC. suisprevalence [9, 10]. The tetracycline resistance found inC. suisis defined by the presence of an efflux pump encoding gene called tetracycline resistance gene class C [tet(C)] within a genomic island [7], though its presence does not necessarily translate into antibiotic resistancein vitro[11]. C. suisstrains carrying thetet(C) gene have been identified in several pig farms in the USA, Italy, Switzerland, Belgium, Cyprus and Israel in recent years [7, 1214, 15]. Moreover, there has been preliminary evidence for selective pressure as a result of antibiotic treatment inC. suis-infected pigs [13]. In this study, we used 158 swab samples from a vast collection of over 2000 fecal and conjunctival swabs originating from.
In a second step, we aimed to investigate whethertet(C) PCR from clinical swabs yielded similar results