Assessment of antibiotic resistance phenotype and integrons in Salmonella enterica serovar Typhimurium isolated from swine

Salmonella enterica serovar Typhimurium (S. Typhimurium) isolated and identified from swine were subjected for the analysis of antibiotic resistance pattern and clinically important class 1 and 2 integrons. In addition, S. Typhimurium isolates exhibiting ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline and florfenicol (ACSSuTF) resistance pattern as described in most Salmonella enterica serotype Typhimurium definitive type 104 (DT104) were characterized by polymerase chain reaction. All the isolates were resistant to more than four antibiotics and showed the highest resistance to streptomycin (94.1%), followed by tetracycline (90.1%), ampicillin (64.7%), chloramphenicol (56.8%) and gentamicin (54.9%). MIC value for the ten isolates ranged between 0.125-2 mug/ml for ciprofloxacin. Among the beta-lactams used, only one of the isolate exhibited resistance to ceftiofur (MIC 8 microg/ml). Sixty eight percent of these multi drug resistance (MDR) S. Typhimurium isolates carried clinically important class 1 integron with 1kb (aadA) and/or 2kb (dhfrXII-orfF-aadA2) resistance gene cassettes. This study reports the increasing trend of multi drug resistance (MDR) S. Typhimurium with clinically important class 1 integron in pigs. In addition, emergence of the ACSSuTF-type resistance in S. Typhimurium PT other than DT104 may limit the use of resistance gene markers in its detection methods by PCR.     

Immunologic responses in healthy random-source cats fed N,N-dimethylglycine-supplemented diets.

The immunomodulatory capacities of N,N-dimethylglycine (DMG) were examined in random-source cats. Blood mononuclear leukocytes of healthy adult cats that had negative results to tests for FeLV and feline immunodeficiency virus were exposed in vitro to various concentrations of DMG (10 to 1,000 micrograms/ml) and were evaluated for proliferative responses to T- or B-cell phytomitogens. Although increased, mean lymphocyte blastogenic responses to phytolectins in DMG-treated cultures did not differ significantly from responses of untreated cultures. For in vivo studies, cats were given a solution containing either 100 mg of DMG or a control solution without DMG orally at 8 AM and 6 PM for 40 consecutive days. On post-treatment day 24 and 25, mean blastogenic responses to phytolectins in DMG-treated and control cats inoculated 10 days earlier with an inactivated feline virus vaccine were similar. Cats given DMG and inoculated twice in a 3-week interval with a commercial vaccine containing inactivated feline herpesvirus-1 and feline calicivirus had significantly (P = 0.045) lower virus neutralizing serum antibody titers against feline herpesvirus-1, compared with titers of control cats, whereas feline calicivirus titers were similar in both groups. On day 25, mean serum interferon activity, induced after IV inoculation of Newcastle disease virus, was significantly (P = 0.021) lower in the DMG-treated cats. Results of this study of DMG in healthy cats failed to demonstrate enhancement of either specific or nonspecific immunity.     

The incidence of antibiotic resistance among coliform bacteria isolated from food.

Three-hundred-and-seventy-eight strains of coliform bacteria were isolated from specimens of commonly sold milk and food products. Klebsiella and Enterobacter spp. were predominating. Resistance to sulphonamides, streptomycin, and chloramphenicol occurred in only 5, 1, and 2 strains, respectively. No tetracycline-resistant strains were found. Two-hundred-and-two strains (54 %) were resistant to ampicillin. In genetic crosses with a sensitive strain of E. coli Κ 12 W 3132 transmissible R factors could not be demonstrated in any of the resistant coliform strains.It is concluded that food is not a significant source of antibiotic resistant enteric bacteria. It may, however, be suggested that food is a source of potentially pathogenic gram-negative bacteria which points out the importance of strict hygienic surveillance of food production.     

鸡肉源与病鸡源沙门菌血清型及耐药状况的比较

为了解市售鲜鸡肉中污染的与临床病鸡感染的沙门菌在血清型与耐药性的差异,对2012-2014年间自南宁市售鲜生鸡肉和同期送检病鸡中分离到的沙门菌进行了血清型分析以及耐药性的比较。结果显示,32株鸡肉源性沙门菌的血清型分布广泛,包括有德比、纽兰和阿贡纳沙门菌等16种血清型;39株病鸡源性沙门菌的血清型则较为单一,只有鸡白痢、鼠伤寒和鸡伤寒沙门菌3种血清型;两种来源的沙门菌均对四环素、复方新诺明、甲氧苄啶,氨苄西林及阿莫西林有较高的耐药性;另外,病鸡源性分离株中多重耐药菌株的比例(89.7%)比鸡肉源性的(56.2%)高。本研究表明,南宁市售鲜生鸡肉与病鸡中的沙门菌分离株在血清型来源上完全不同,提示市售鸡肉中污染的食源性沙门菌并非来自饲养阶段的患病鸡;病鸡源性沙门菌的耐药情况较鸡肉源性沙门菌的更为严重。     

Incidence and antibiotic resistance of Salmonella spp. in ground turkey meat

1.?The objectives of this study were to isolate Salmonella spp. by conventional culture technique from ground turkey samples, to determine the seasonal distribution of Salmonella spp., to verify the isolates by PCR using primers based on oriC gene sequence, and to determine the antibiotic susceptibility profiles of the isolates. A total of 240 packaged fresh ground turkey samples marketed in Ankara were analysed between July 2004 and June 2005.

2.?One hundred and ten out of 240 (45?8%) samples were positive for Salmonella spp. and confirmed by PCR. The distribution of Salmonella spp. was determined as 48?3, 55?0, 63?3 and 16?6%, during spring, summer, autumn and winter, respectively. Statistical analysis showed a significant difference for the prevalence of Salmonella spp. between winter and the other seasons.

3.?Of the isolates, 54 out of 110 (49?0%) were resistant to one or more antibiotics tested. The highest resistance was observed to nalidixic acid (25?4%), followed by streptomycin (17?2%) and tetracycline (15?4%).

4.?In conclusion, this is a disturbing finding, both for the high prevalence of Salmonella and the extent of antibiotic resistance. Ground turkey should be produced under suitable hygienic and technological conditions and the use of antimicrobials must be controlled by governmental agencies to protect public health from salmonellosis and from the consequences of increased resistance to the antibiotics.     

深圳地区动物肉源沙门菌的分离鉴定及耐药性分析

在改进沙门菌分离方法的基础上,分离并鉴定深圳市动物肉源沙门菌,并进行耐药性分析。结果:采集自深圳地区的1 055个动物肉源样品的沙门菌总阳性率为21. 04%,其中:鸡肉(28. 71%)>猪肉(24. 95%)>牛肉(15. 00%)>虾肉(2. 82%)。基于最小抑菌浓度(MIC)测定去除重复的耐药表型,得到370株非重复沙门菌株;其中的75. 2%多重耐药,53株(14. 10%)表现ACSSuT^R耐药表型。经血清型鉴定,得到38种血清型及327株确定血清型的沙门菌,优势血清型包括Derby、1,4,[5],12: i: -、Rissen、Agona和8,20: z23,z4: -。在分离动物肉源沙门菌的过程中,四硫酸盐肉汤(TT)相比于氯化镁孔雀绿肉汤(RV)更有效。本研究表明,深圳地区动物肉源样品中,沙门菌分离率鸡肉和猪肉高于牛肉和虾肉,血清型以Derby、1,4,[5],12: i: -、Rissen、Agona和8,20: z23,z4: -为主,且多重耐药比例较高。     

鸡源性沙门氏菌耐药基因检测与耐药相关性分析

为研究沙门氏菌耐药基因与其耐药性之间的关系,本研究以K-B纸片法对临床分离的29株鸡源性沙门氏菌进行10种抗菌药物敏感性测定,应用PCR技术进行这些抗菌药物相关耐药基因检测.并通过质粒接合试验证明了耐药性及耐药基因的转移.结果显示:29株分离株对氨苄西林耐药率为31.0％,对头孢唑啉耐药率为10.3％,对四环素耐药率为44.8％,对复合磺胺耐药率为41.4％,对氯霉素耐药率为3.4％,对环丙沙星、氧氟沙星、诺氟沙星的耐药率均为37.9％,但对庆大霉素和卡那霉素均敏感.本实验共检测到8种耐药基因,其中blatem-1阳性率为31.0％,tetA和tetB阳性率为44.8％,sull和sul2阳性率为41.3％,aadAl阳性率为3.4％,dfrA1阳性率为10.3％,qnr阳性率为37.9％,而tetG、blaCMY-2和catI均未检出.此外,通过与非耐药菌接合后绝大部分接合子均获得了供体菌质粒编码的相应抗性表型,耐药基因在接合过程也发生了转移,赋予被接合细菌新的耐药性.以上结果表明沙门氏菌的耐药性与其相关耐药基因的检出率基本一致,而且耐药性通过质粒进行转移.     

Prevalence of antibiotic resistance genes in staphylococci isolated from ready-to-eat meat products

Prevalence of mecA, blaZ, tetO/K/M, ermA/B/C, aph, and vanA/B/C/D genes conferring resistance to oxacillin, penicillin, tetracycline, erythromycin, gentamicin, and vancomycin was investigated in 65 staphylococcal isolates belonging to twelve species obtained from ready-to-eat porcine, bovine, and chicken products. All coagulase negative staphylococci (CNS) and S. aureus isolates harbored at least one antibiotic resistance gene. None of the S. aureus possessed more than three genes, while 25% of the CNS isolates harbored at least four genes encoding resistance to clinically used antibiotics. In 15 CNS isolates the mecA gene was detected, while all S. aureus isolates were mecA-negative. We demonstrate that in ready-to-eat food the frequency of CNS harboring multiple antibiotic resistance genes is higher than that of multiple resistant S. aureus, meaning that food can be considered a reservoir of bacteria containing genes potentially contributing to the evolution of antibiotic resistance in staphylococci.     

The antibiotic resistance of pathogenic staphylococci and streptococci isolated from dogs

The antibiotic resistance of strains of Staphylococcus aureus and beta–haemolytic streptococci of canine origin were assessed against eight drugs using the disc diffusion technique. Of 398 strains of Staph, aureus eight were resistant to neomycin, 15 to ampicillin, 23 to lincomycin, while of 87 streptococci, one was resistant to ampicillin, two to lincomycin and four to penicillin. In addition 4 of 340 Staph, aureus strains tested against cloxacillin were resistant.     

Characterization of integron mediated antimicrobial resistance in Salmonella isolated from diseased swine

Forty-two Salmonella isolates obtained from diseased swine were genetically characterized for the presence of specific antimicrobial resistance mechanisms. Twenty of these isolates were characterized as S. Typhimurium DT104 strains. Pulsed-field gel electrophoresis was used to determine genetic relatedness and revealed 20 distinct genetic patterns among the 42 isolates. However, all DT104 isolates fell within 2 closely related genetic clusters. Other Salmonella isolates were genetically grouped together according to serotype. All DT104 isolates displayed the penta-resistance phenotype to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline. Resistance to sulfamethoxazole, tetracycline, streptomycin, kanamycin, and ampicillin was most common among the non-DT104 Salmonella isolates. All DT104 strains contained 2 chromosomal integrons of 1000 and 1200 base pairs. The DNA sequencing revealed that the 2 integrons contained genes encoding a resistance to streptomycin and ampicillin, respectively. None of the non-DT104 strains showed the same pattern, although several strains possessed integrons of 1000 base pairs or larger. However, the majority of non-DT104 Salmonella strains did not possess any integrons. Two Salmonella isolates displayed tolerance to the organic solvent cyclohexane, indicating the possibility that they are overexpressing chromosomal regulatory genes marA or soxS or the associated multidrug efflux pump, acrAB. This research suggests that integrons contribute to antimicrobial resistance among specific swine Salmonella serotypes; however, they are not as widely disseminated among non-Typhimurium swine Salmonella serotypes as previously thought.     

Differences in antibiotic resistance in Escherichia coli,isolated from East-European swine herds with or without prophylactic use of antibiotics

The aim of the study was to compare the resistance patterns of Escherichia coli isolates from pig herds with or without prophylactic use of anti-microbial substances. The presented pig units received either antibiotics or oregano as preventive feed additives. The trial was performed from April to October 2001, in the large 'country-corner', Hungary-Rumania-Serbia. Thirty of 39 evaluated herds suffered E. coli O139 K88 ac or ad LT STb caused losses, the remaining were negative for E. coli O139. Thirteen of the selected 30 herds produced with oregano feed supplementation (Oregpig Pecs, Hungary) antibiotic-free pigs. These units had no history of prophylactic antibiotic use since 1995. The remaining 17 herds routinely used prophylactic antibiotic feed supplementation. In each herd, pigs of four different age groups (suckling piglets, weaners. fattening swine and breeding sows), showing the clinical symptoms of wasting, were investigated. E. coli O139 K88 ac or ad LT STb were tested for their resistance to antibiotics, available in this region. Oregano-fed herds demonstrated high significantly (P < 0.001) lower MICs (microg/ml) for ampicillin, doxycyclin, enrofloxacin, gentamycin, oxytetracyclin and sulfamethacin compared to herds with prophylactic use of antibiotics. Resistance to ceftiofur revealed significant (P < 0.05) differences between the antibiotic- or oregano-treated units. The present results confirm literature data, that prophylactic use of antibiotics likely plays a role in inducing resistance of E. coli and other intestinal bacteria. Thus, imposing greater restrictions on antibiotic use in animal agriculture is likely to reduce but not eliminate the occurrence of resistant isolates.