Temporal prevalence of antimicrobial resistance in Campylobacter spp. from beef cattle in Alberta feedlots

Antimicrobial resistance (AMR) was temporally assessed in campylobacters isolated from beef cattle (7,738 fecal samples from 2,622 animals) in four commercial feedlots in Alberta. All calves were administered chlortetracycline and oxytetracycline in feed, and a majority of the animals (93%) were injected with long-acting oxytetracycline upon arrival at the feedlot. Fecal samples from individual animals were collected upon arrival (i.e., entry sample), 69 days (standard deviation [SD] = 3 days) after arrival (i.e., interim sample), and 189 days (SD = 33 days) after arrival (i.e., exit sample) at the feedlot. In total, 1,586 Campylobacter isolates consisting of Campylobacter coli (n = 154), Campylobacter fetus (n = 994), Campylobacter jejuni (n = 431), Campylobacter hyointestinalis (n = 4), and Campylobacter lanienae (n = 3) were recovered and characterized. The administration of antimicrobials did not decrease carriage rates of campylobacters, and minimal resistance (< or =4%) to azithromycin, ciprofloxacin, enrofloxacin, gentamicin, and meropenem was observed. In contrast, substantive increases in the prevalence of isolates resistant to tetracycline and doxycycline (56 to 89%) for C. coli, C. fetus, and C. jejuni, as well as in the number of animals (7 to 42%) from which resistant isolates were recovered, were observed during the feedlot period. Increased resistance to erythromycin (total isolates and carriages rates) was also observed in isolates of C. coli over the three isolation times. The majority of C. fetus isolates recovered were resistant to nalidixic acid, but this was independent of when they were isolated. A relatively limited number of multidrug-resistant isolates were recovered and consisted primarily of C. coli resistant to tetracyclines and erythromycin (10% of isolates). Over the course of the feedlot period, considerable increases in antimicrobial resistance were observed in C. coli, C. fetus, and C. jejuni, but with the exception of erythromycin resistance in C. coli, the administration of antimicrobial agents to beef cattle was found to have a minimal impact on resistance to macrolides and fluoroquinolones, the two classes of antimicrobials used to treat campylobacteriosis in humans. However, the widespread use of antimicrobial agents in beef production and the possible horizontal transfer of mobile genetic elements with antimicrobial resistance determinants among Campylobacter and other bacterial taxa emphasize the need to monitor AMR development in bacteria from beef cattle.     

Enterotoxigenicity and frequency of Campylobacter jejuni, C. coli and C. laridis in human and animal stool isolates from different countries

Campylobacter jejuni and C. coli strains were collected during three different years from adult patients with enterocolitis in Sweden (n = 372) from 49 patients in Kuwait, and Campylobacter strains from hens from Mexico, Pakistan and Sweden (n = 107) and Swedish pigs (n = 47). C. jejuni was the predominant species in human and hen isolates, and C. coli in pigs C. coli was significantly more common in human isolates from Sweden, and more common in hen isolates from Pakistan, than in hens from Sweden and Mexico. C. laridis was only isolated from pigs (17%) and was in no case enterotoxigenic. Both in human and hen isolates, C. jejuni strains were more enterotoxigenic than C. coli strains. C. jejuni strains from Swedish hens were less enterotoxigenic than those from Pakistan and Mexico (P less than 0.001), and strains from pigs were less enterotoxigenic than those from hens (P less than 0.001). We conclude that C. jejuni are more often enterotoxigenic and possibly more virulent than c. coli and C. laridis. The relative frequency of C. jejuni and C. coli in humans and animals differs from one country to another.     

Identification of lactobacilli residing in chicken ceca with antagonism against Campylobacter

Bacteriocins produced by Lactobacillus salivarius have been recently recognized as a natural means to control Campylobacter and Salmonella in live poultry. This finding is of relevance since Campylobacter jejuni and Campylobacter coli are the predominant species isolated from poultry that are associated with human campylobacteriosis. In the present work, lactic acid bacteria (LAB) isolated from the cecum of twenty Tunisian chickens were identified and those isolates with antagonism against Campylobacter were further characterized. Following their preliminary confirmation as LAB, 150 strains were identified by combining morphological criteria, biochemical tests, and molecular methods, the latter inluding intergenic 16S- 23S PCR, specific lactobacilli PCR, and a biphasic approach. Most of the LAB isolated belonged to the genus Lactobacillus, among them Lb. sakei (33.3%), Lb. salivarius (19.4%), Lb. reuteri (8.6%), and Lb. curvatus (8.6%). The other LAB strains included those of the genus Weissella (16.7%), Enterococcus faecalis (5.3%), Leuconostoc mesenteroides (2.7%), Lactococcus graviae (2.7%), and Streptococcus sp. (2.7%). The Lactobacilli strains were tested for their antagonism against C. jejuni and C. coli. The activity of three of them, Lb. salivarius SMXD51, Lb. salivarius MMS122, and Lb. salivarius MMS151, against the aforementioned target strains could be ascribed to the production of bacteriocins.     

Characterization of dominant cultivable lactobacilli and their antibiotic resistance profiles from faecal samples of weaning piglets

AIMS: To examine the lactic acid bacteria flora of weaning piglets, to define the distribution of different lactobacilli species in piglet faecal samples, and to determine the susceptibility phenotype to 11 antibiotic of different families. METHODS AND RESULTS: The faecal samples were taken from piglets with good herd status at 11 and 28 days after weaning. The Lactobacillus isolates (n = 129) from 78 animals housed in pairs in 39 pens were preliminarily identified by their morphology and biochemical characteristics. Partial 16S ribosomal DNA (16S rDNA) was used to identify the isolates to the species level, and RAPD (randomly amplified polymorphism DNA) profiles to differentiate Lactobacillus isolates to the strain level. Based on these studies, 67 strains were selected for antibiotic resistant tests. The most numerous Lactobacillus species found in the piglets was Lactobacillus reuteri (n = 43). Other lactobacilli were L. salivarius (n = 15), L. agilis (n = 4), L. johnsonii (n = 2), L. vaginalis (n = 1), L. mucosae (n = 1) and L. gallinarum (n = 1). All the strains were susceptible to chloramphenicol, ampicillin and gentamicin. Two L. salivarius isolates and two L. reuteri isolates were found to be multiresistant. CONCLUSIONS: This study indicates that the faecal Lactobacillus flora in piglets consists mainly of L. reuteri, L. salivarius and L. acidophilus group lactobacilli, and the distribution of lactobacilli is similar between individuals of the same age and with the same diet. Most of the Lactobacillus isolates tested were sensitive to the antibiotics used in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: Valuable information on Lactobacillus species distribution and their antibiotic resistance profiles in piglets is obtained.     

Lactobacillus inhibitor production against Escherichia coli and coaggregation ability with uropathogens

Previous investigations have shown that certain strains of lactobacilli can competitively exclude uropathogens from attaching to uroepithelial cells and from causing urinary tract infection in animals. The finding of an inhibitory effect produced by Lactobacillus casei ssp. rhamnosus GR-1 against the growth of uropathogens was investigated further using two Escherichia coli indicator strains Hu 734 and ATCC 25922. There were two phases to the inhibitor studies. The first one using an agar sandwich technique showed that the inhibitor activity was heat stable and inhibitory to the E. coli. The second phase showed that MRS broth provided optimum lactobacilli growth and inhibitor production. In addition, the inhibition was present under conditions buffering for acid and pH. The data indicated that the inhibitory effect was not due to bacteriophages or hydrogen peroxide. Strain GR-1 was found to coaggregate with E. coli ATCC 25922 in urine, a phenomenon that has not previously been reported for urogenital bacteria. An in vitro assay system was developed to study the coaggregation of various lactobacilli and uropathogens. The results demonstrated that highest coaggregation scores occurred after 4 h incubation at 37 degrees C with lactobacilli and two type-1 fimbriated E. coli strains. Of the nine lactobacilli strains tested, each was found to coaggregate with 2 or more of the 13 uropathogens. The dominance of inhibitor-producing lactobacilli on the urogenital epithelium and the ability of these organisms to interact closely with uropathogens would constitute an important host defense mechanism against infection.     

Effect of lactobacilli onE. coli adhesion to caco-2 cellsin Vitro

Inhibitory effect of various lactobacilli against pathogenic strains of E. coli in model system Caco2 cells was determined by enumerating the number of adhering E. coli after pre-incubation (exclusion), post-incubation (displacement) or co-incubation (competition) with lactobacilli. Porcine E. coli strain F107 (F18ab, Stx2v) in the competition assay with porcine lactobacillus strain P10 gave bacterial counts 7.25 (log CFU per well); in the exclusion test it was only 7.05 while in displacement test it reached 7.29. The lowest E. coli counts adhering to Caco-2 cells were in exclusion assay (pre-incubation, Lactobacillus inoculated as the first). Pre-treatment of E. coli with our lactobacilli strains reduced the cultivable E. coli numbers.     

The effects of antibiotic usage in food animals on the development of antimicrobial resistance of importance for humans in Campylobacter and Escherichia coli

Modern food animal production depends on use of large amounts of antibiotics for disease control. This provides favourable conditions for the spread and persistence of antimicrobial-resistant zoonotic bacteria such as Campylobacter and E. coli O157. The occurrence of antimicrobial resistance to antimicrobials used in human therapy is increasing in human pathogenic Campylobacter and E. coli from animals. There is an urgent need to implement strategies for prudent use of antibiotics in food animal production to prevent further increases in the occurrence of antimicrobial resistance in food-borne human pathogenic bacteria such as Campylobacter and E. coli.     

Antagonistic activity of Lactobacillus bacteria strains against anaerobic gastrointestinal tract pathogens (Helicobacter pylori, Campylobacter coli, Campylobacter jejuni, Clostridium difficile)]

Antagonistic activity of Lactobacillus strains has been known for some time. This property is connected with production of many active substances by lactobacilli e.g., organic acids and bacteriocin-like substances which interfere with other indigenous microorganisms inhabiting the same ecological niche, including also anaerobic gastrointestinal tract pathogens. Growing interest of clinical medicine in finding new approaches to treatment and prevention of common inflammatory infections of the digestive tract resulted in studies on a possible usage of lactic acid bacteria. Last years, several in vitro and in vivo experiments on antagonism of different Lactobacillus strains against Helicobacter pylori and Clostridium difficile were performed. These observations had been done on already established, well known probiotic Lactobacillus strains. We tested antibacterial activities of Lactobacillus strains isolated from human digestive tract. As indicator bacteria, four species known as anaerobic bacterial etiologic agents of gastroenteric infections: Helicobacter pylori, Campylobacter jejuni, C. coli and Clostridium difficile were used. Some of them were obtained from international collections, others were clinical isolates from specimens taken from patients with different defined gastrointestinal infections. We used a slab method of testing inhibitory activity described in details previously. Following conclusions were drawn from our study: All tested human Lactobacillus strains were able to inhibit the growth of all strains of anaerobic human gastrointestinal pathogens used in this study. Inhibitory activities of tested Lactobacillus strains against Helicobacter pylori, Campylobacter spp., and Clostridium difficile as measured by comparing mean diameters of the inhibition zones were similar. Differences in susceptibility of individual indicator strains of Campylobacter spp. and Clostridium difficile to inhibitory activity of Lactobacillus strains were small. A similar mechanism of inhibition of anaerobic bacteria by lactobacilli is postulated.     

Genetic characterization and antibiotic resistance of Campylobacter spp. isolated from poultry and humans in Senegal

AIMS: The main objectives of this study were to investigate the diversity of Campylobacter genotypes circulating in Senegal and to determine the frequency of antibiotic resistance. METHODS AND RESULTS: Strains of Campylobacter jejuni isolated from poultry (n = 99) and from patients (n = 10) and Campylobacter coli isolated from poultry (n = 72) were subtyped by pulsed-field gel electrophoresis (PFGE). The pulsotypes obtained after digestion by SmaI and KpnI revealed a significant genetic diversity in both species, but without any predominant pulsotypes. However, farm-specific clones were identified in the majority of poultry houses (76.5%). Human and poultry isolates of C. jejuni had common PFGE patterns. High quinolone-resistance rates were observed for C. jejuni (43.4%) and C. coli (48.6%) isolates obtained from poultry. CONCLUSIONS: The results showed a genetic diversity of Campylobacter between farms indicating multiple sources of infection; but specific clones had the ability to colonize the broiler farms. The antimicrobial resistance patterns were not related to any specific PFGE pattern suggesting that resistance was due to the selective pressure of antibiotic usage. Campylobacter with similar genotypes were circulating in both human and poultry. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is important for the understanding of the epidemiology of Campylobacter in broiler farms in Senegal. It also emphasizes the need for a more stringent policy in the use of antimicrobial agents in food animals.     

Antibacterial activity of rifampicin against the causative agents of suppurative, septic diseases]

The antibacterial activity of rifampicin was studied in comparison with other antibiotics with respect to clinical strains isolated from cases with various purulent inflammatory processes caused by Staphylococcus, E. coli, Ps. aeruginose, Proteus. The aim of the study was to define the role of rifampicin in the treatment of the above infections. No rifampicin resistant strains were found among staphylococci belonging to the phenotype carrying the determinants of resistance to 2-8 antibiotics. Rifampicin was less active against gramnegative organisms. High heterogeneity of the microbial population of rifampicin was shown with respect to all microbial strains tested. The rate of the spontaneous mutants was high. The average rate of the mutants was 1-7.7-10-8. The studies on the dynamics of the rifampicin resistance increase in the strains of Staphylococci, E. Coli, Ps. aeruginosa and Proteus showed that the resistance increased after 1-2 passages, which means that one-stage mutation was characteristic rifampicin.     

Antimicrobial resistance patterns of Campylobacter from feedlot cattle*

AIMS: This study examined 448 Campylobacter strains isolated in 1999 and 2000 from US feedlot cattle for resistance to 12 antimicrobials. METHODS AND RESULTS: Isolates were tested for antimicrobial susceptibility using the E-test method. Approximately 60% (n = 267) were resistant to one or more antimicrobials, and 19.6% (n = 88) were resistant to two or more antimicrobials. Of the Campylobacter jejuni isolates, 49.1% (n = 187) were resistant to tetracycline, 10.2% (n = 39) were resistant to nalidixic acid, 8.4% were resistant to trimethoprim/sulfamethoxazole, and 1.8% (n = 7) were resistant to ciprofloxacin. Resistance to any of the other eight antimicrobials was 1.3% or less, but 14.4% (n = 55) were resistant to two or more antimicrobials. In the Campylobacter coli group, 65.7% (n = 44) were resistant to tetracycline, 52.2% (n = 35) were resistant to trimethoprim/sulfamethoxazole, 22.4% (n = 15) were resistant to nalidixic acid, and 9.0% (n = 6) were resistant to ciprofloxacin. Resistance to any of the remaining eight antimicrobials was 3.0% or less, although 49.3% (n = 33) were resistant to two or more antimicrobials. CONCLUSIONS: Although antimicrobials are widely used in US feedlot cattle production, our results demonstrate generally low levels of resistance to a broad range of commonly used antimicrobials relative to other recent studies. SIGNIFICANCE AND IMPACT OF THE STUDY: Resistance data on Campylobacter isolated from this major US livestock commodity is lacking. This overview enhances current knowledge and provides a basis for further studies.     

Antibiotic resistance and resistance mechanisms in Campylobacter jejuni and Campylobacter coli

Campylobacter jejuni and Campylobacter coli are recognized as the most common causative agents of bacterial gastroenteritis in the world and infections with these organisms occur more frequently than do infections due to Salmonella species, Shigella species, or Escherichia coli 0157:H7. The incidence of human Campylobacter infections has increased markedly in both developed and developing countries worldwide and, more significantly, so has the rapid emergence of antibiotic-resistant Campylobacter strains, with evidence suggesting that the use of antibiotics, in particular the fluoroquinolones, as growth promoters in food animals and the veterinary industry is accelerating this trend. In this minireview, the patterns of emerging resistance to the antimicrobial agents useful in treatment of the disease are presented and the mechanisms of resistance to these drugs in Campylobacter spp are discussed.     

Antimicrobial resistance of Campylobacter jejuni and Campylobacter coli isolates from broiler chickens isolated at an Irish poultry processing plant

AIMS: The antibiotic susceptibility of Campylobacter jejuni and Campylobacter coli isolates from broiler chickens were determined in order to evaluate the level of antibiotic resistance of Campylobacter species in the Irish poultry industry. METHODS AND RESULTS: Seventy-eight Camp. jejuni and 22 Camp. coli strains were examined for susceptibility to eight antibiotics using the disc diffusion assay. The highest level of resistance of the Camp. jejuni isolates was recorded to ampicillin (35.9%), followed by 20.5% to tetracycline, 20.5% to naladixic acid, 17.9% to ciprofloxacin, 10.2% to erythromycin, 2.5% to streptomycin and 1.2% to kanamycin. Multidrug resistance to two or more antibiotics was seen for 30.7% of Camp. jejuni strains. Resistance of the Camp. coli isolates was shown to ampicillin (9%) and tetracycline (18.2%). CONCLUSIONS: The majority of Camp. jejuni strains were susceptible to antibiotics commonly used for human therapy. Camp. coli strains showed very low resistance levels and were susceptible to six of the eight antimicrobial agents studied. SIGNIFICANCE AND IMPACT OF THE STUDY: Levels of Camp. jejuni and Camp. coli antimicrobial resistance in Irish poultry production was assessed to determine the current situation in Ireland. The prevalence of antibiotic resistance of Campylobacter strains isolated from broiler chickens was low.     

Factors affecting the pressure resistance of some Campylobacter species

AIMS: To compare pressure resistance between strains of Campylobacter jejuni, Campylobacter coli, Campylobacter lari and Campylobacter fetus, and to investigate the effect of suspending medium on pressure resistance of sensitive and more resistant strains. METHODS AND RESULTS: Six strains of C. jejuni and four each of C. coli, C. lari and C. fetus were pressure treated for 10 min at 200 and 300 MPa. Individual strains varied widely in pressure resistance but there were no significant differences between the species C. jejuni, C. coli and C. lari. Campylobacter fetus was significantly more pressure sensitive than the other three species. The pressure resistance of C. jejuni cultures reached a maximum at 16-18 h on entry into stationary phase then declined to a minimum at 75 h before increasing once more. Milk was more baroprotective than water, broth or chicken slurry but did not prevent inactivation even of a resistant strain at 400 MPa. CONCLUSIONS: Pressure resistance varies considerably between species of Campylobacter and among strains within a species, and survival after a pressure challenge will be markedly influenced by culture age and food matrix. SIGNIFICANCE AND IMPACT OF THE STUDY: Despite the strain variation in pressure resistance and protective effects of food, Campylobacter sp. do not present a particular problem for pressure processing.     

合肥地区动物源性大肠埃希菌的血清型分布与耐药性分析

目的了解安徽省合肥地区动物源性大肠埃希菌的血清型分布和耐药状况,以期筛选出菌苗株和指导临床合理用药。方法对46份疑似大肠埃希菌病病料进行细菌分离培养、生化编码鉴定和致病性测定。采用玻片凝集试验对分离到的46株致病性大肠埃希菌进行血清型鉴定。同时分别采用K-B纸片琼脂扩散法和双纸片增效法检测致病性大肠埃希菌的耐药性和ESBLs阳性菌株。结果46株致病性大肠埃希菌中,除7株细菌未能定型外,其余39株细菌分布于10个血清型,O127：K63血清型为优势血清型,占定型菌株的33．33％。46株致病性大肠埃希菌对21种抗菌药物均呈现不同程度的耐药性,15个ESBLs阳性菌株表现为多重耐药,对各种抗菌药物的耐药率均高于ESBLs阴性菌株。结论O127：K63血清型为优势血清型,可作为菌苗株。合肥地区动物源性大肠埃希菌耐药性较为严重,尤其是产ESBLs大肠埃希菌多重耐药更为突出。     

Effect of oregano essential oil on chicken lactobacilli andE. coli

The effect of the oregano essential oil (EO) on lactobacilli and E. coli isolated from chicken was showed in the series of in vitro and in vivo experiments. Minimum inhibitory concentrations of amikacin, apramycin, streptomycin, neomycin against E. coli strains increased after oral application of EO.     

Antimicrobial resistance and plasmid profiles of Campylobacter jejuni and Campylobacter coli from human and animal sources

AIMS: The purpose of this study was to determine the susceptibility of Campylobacter jejuni and Campylobacter coli isolates to antimicrobial agents and to investigate the presence of plasmid DNA. METHODS AND RESULTS: A total of 15 clinical isolates from children faeces, and 29 animal isolates of Campylobacter jejuni (n=22) and Campylobacter coli (n=22) were tested for susceptibility to 9 antimicrobial agents using a disc diffusion method, and screened for the presence of plasmid DNA by agarose gel electrophoresis. Of the 44 isolates, 56.8% were resistant to sulphonamide, 25% to norfloxacin, 18.2% to erythromicin, ciprofloxacin and ampicillin, and 13.6% to tetracycline. All isolates were susceptible to gentamicin, chloramphenicol and cefotaxime. Plasmids were detected in one Camp. jejuni (4.54%) strain isolated from sheep and in six (27.27%) Camp. coli strains isolated from rhesus monkey(3), swine(2), and poultry(1) with sizes ranging from 3.4 to 50 kb. CONCLUSIONS: The majority of the human isolates were susceptible to antibiotics commonly used for the treatment of campylobacteriosis. SIGNIFICANCE AND IMPACT OF THE STUDY: The origin and spread of Campylobacter resistance to antibiotics are discussed, with particular respect to the current situation in Brazil.     

Characterization of vaginal lactobacilli coaggregation ability with Escherichia coli

The coaggregation abilities of probiotic strains might enable it to form a barrier that prevents colonization by pathogenic bacteria. In the present study, the characterization of the coaggregation ability of 19 vaginal lactobacilli was studied. Coaggregation ability of all lactobacilli with Escherichia coli ATCC 11229 was positive. Only the highest coaggregation percentage of Lactobacillus acidophilus S1 was obtained with E. coli ATCC 11229 under both aerobic (71%) and anaerobic conditions (62%). The coaggregation abilities of strains occurred higher at acidic pH than at basic pH values. Moreover, the coaggregation abilities of tested strains against E. coli decreased after heat treatment (70 or 85 °C). Also, the relationship between hydrophobicity and coaggregation of strains was found to be significant. The effect of sonication, some enzymes (lipase and pepsin) and sodium periodate on coaggregation ability of L. acidophilus S1, which is one of the highest potentials on coaggregation ability, was investigated. Sodium periodate did not have a significant effect on coaggregation ability of L. acidophilus S1. The sonicated cell showed lower coaggregation than the control, the supernatant fluid of this sonicated cells showed similar coaggregation ability to the control. Coaggregation abilities of bacteriotherapeutic lactobacilli with pathogenic bacteria can be used for preliminary screening in order to identify potentially probiotic bacteria suitable for human use against urogenital tract infections.     

Effects of dietary lactose and purified diet on intestinal microflora of rats

In the rats fed on lactose-containing purified diet (PDL), bifidobacteria remarkably increased in number in both the jejunum and cecum as compared with those fed on control diet (PD) or conventional diet (NMF). Besides, lactobacilli, streptococci, staphylococci, and Escherichia coli increased in number in the jejuna and/or ceca of rats fed on PDL as compared with those fed on PD. The incidence and numbers of Lactobacillus species were remarkably different between the rats fed on PDL and those on any of the other diets. Indole-producing Bacteroides spp. were rarely isolated from the PDL-fed rats. The cecum was markedly enlarged in the PDL rats and reduced in the PD rats as compared with that in the NMF animals.     

Effect of conventional and organic production practices on the prevalence and antimicrobial resistance of Campylobacter spp. in poultry

Intestinal tracts of broilers and turkeys from 10 conventional broiler farms and 10 conventional turkey farms, where antimicrobials were routinely used, and from 5 organic broiler farms and 5 organic turkey farms, where antimicrobials had never been used, were collected and cultured for Campylobacter species. A total of 694 Campylobacter isolates from the conventional and organic poultry operations were tested for antimicrobial resistance to nine antimicrobial agents by the agar dilution method. Although Campylobacter species were highly prevalent in both the conventional and organic poultry operations, the antimicrobial resistance rates were significantly different between the organic operations and the conventional operations. Less than 2% of Campylobacter strains isolated from organically raised poultry were resistant to fluoroquinolones, while 46% and 67% of Campylobacter isolates from conventionally raised broilers and conventionally raised turkeys, respectively, were resistant to these antimicrobials. In addition, a high frequency of resistance to erythromycin (80%), clindamycin (64%), kanamycin (76%), and ampicillin (31%) was observed among Campylobacter isolates from conventionally raised turkeys. None of the Campylobacter isolates obtained in this study was resistant to gentamicin, while a large number of the isolates from both conventional and organic poultry operations were resistant to tetracycline. Multidrug resistance was observed mainly among Campylobacter strains isolated from the conventional turkey operation (81%). Findings from this study clearly indicate the influence of conventional and organic poultry production practices on antimicrobial resistance of Campylobacter on poultry farms.