Occurrence and characteristics of enterohemorrhagic Escherichia coli O26 and O111 in calves associated with diarrhea

The aims of this study were: (1) to examine whether or not enterohemorrhagic Escherichia coli O26 and O111 (EHEC O26 and O111) are involved in neonatal calf diarrhea; (2) to determine the specific age periods at which the calves are vulnerable to these organisms, and (3) to reveal the biochemical, genetic and cytotoxic characteristics of the isolates. The study investigated the occurrence of EHEC O26 and O111 in calves associated with or without diarrhea. A total of 442 diarrheic and non-diarrheic young calves from 115 different farms were examined. Of the 257 calves with diarrhea, 37 (14.4%) and 32 (12.5%) tested positive for EHEC O26 and EHEC O111, respectively. Of the 185 non-diarrheic calves, 14 (7.6%) and 11 (5.9%) tested positive for EHEC O26 and EHEC O111, respectively. EHEC O26 and O111 were recovered from 14/69 (20%) and 11/69 (16%) diarrheic calves <2-weeks-old, respectively, and no EHEC O26 and O111 were detected in the non-diarrheic claves of this age group, suggesting that EHEC O26 and O111 are possible causes of the disease in infected neonatal calves. However, there were similar rates of occurrence in the diarrheic and non-diarrheic calves in the older animals (particularly, aged >10 weeks). PCR analysis showed that the isolates carried various virulence genes such as Ehly, eae, stx1 and stx2, which highlight the potential importance of these attributes for the infection, colonization and the possible pathogenesis of calf diarrhea. Cytotoxicity analysis revealed that many of the EHEC isolates showed high cytotoxicity to Vero cells, re-emphasizing the potential for cattle being a direct source of EHEC infections in humans.     

Antimicrobial resistant Escherichia coli isolates in cattle and house sparrows on two Czech dairy farms

Rectal smears of calves, cows and young bulls, as well as cloacal smears of house sparrows (Passer domesticus), from farms at the villages of Sumice and Troskotovice, Czech Republic, were examined for E. coli resistant to 12 antimicrobials. The resistant isolates were tested for antimicrobial-resistance genes and integrons. Totals of 40% (n=183), 3% (n=95), 0% (n=33), and 9% (n=54) of Escherichia coli isolates from calves, cows, young bulls and house sparrows, respectively, were antimicrobial resistant. The following genes were identified in cattle E. coli isolates: tetA, tetB (isolates resistant to tetracycline), bla(TEM) (beta-lactams), strA, aadA (streptomycin), sul1, sul2 (sulphonamides), and cat, floR (chloramphenicol). Seven of 16 antimicrobial-resistant calf isolates from the Sumice farm possessed class 1 integrons with the aadA1 gene cassette integrated, 1 kb in size. On the Troskotovice farm, eight of 57 antimicrobial-resistant calf isolates possessed class 1 integrons. Integrons of 1.5kb with the dhfr1- aadA1 gene cassette were found in four isolates, followed by a 1kb integron with the aadA1 gene found in three isolates, and a 1.7kb integron with the dhfr17-aadA5 gene cassette and the phenotype ASSuTSxtNaCipCCfG. The prevalence of resistant E. coli in calves compared to adult cattle was much higher and probably was influenced by oral antimicrobial usage in calves, feeding with milk and colostrum from treated cows, as well as mechanisms unrelated to antimicrobial drug selection. Although house sparrows lived together with the cattle and came into contact with cattle waste on the farm, they were not infected by resistant E. coli isolates with the same characteristics as those found in cattle.     

Antimicrobial resistance of Escherichia coli isolates from canine urinary tract infections

This study determined the antimicrobial resistance profiles of Escherichia coli isolates from dogs with a presumptive diagnosis of urinary tract infection (UTI). Urine samples from 201 dogs with UTI diagnosed through clinical examination and urinalysis were processed for isolation of Escherichia coli. Colonies from pure cultures were identified by biochemical reactions (n=114) and were tested for susceptibility to 18 antimicrobials. The two most frequent antimicrobials showing resistance in Urinary E. coli isolates were oxytetracycline and ampicillin. Among the resistant isolates, 17 resistance patterns were observed, with 12 patterns involving multidrug resistance (MDR). Of the 69 tetracycline-resistant E. coli isolates, tet(B) was the predominant resistance determinant and was detected in 50.9% of the isolates, whereas the remaining 25.5% isolates carried the tet(A) determinant. Most ampicillin and/or amoxicillin-resistant E. coli isolates carried bla_TEM-1 genes. Class 1 integrons were prevalent (28.9%) and contained previously described gene cassettes that are implicated primarily in resistance to aminoglycosides and trimethoprim (dfrA1, dfrA17-aadA5). Of the 44 quinolone-resistant E. coli isolates, 38 were resistant to nalidixic acid, and 6 were resistant to nalidixic acid, ciprofloxacin and enrofloxacin. Chromosomal point mutations were found in the GyrA (Ser83Leu) and ParC (Ser80Ile) genes. Furthermore, the aminoglycoside resistance gene aacC2, the chloramphenicol resistant gene cmlA and the florfenicol resistant gene floR were also identified. This study revealed an alarming rate of antimicrobial resistance among E. coli isolates from dogs with UTIs.     

仔猪腹泻源大肠杆菌耐药性调查及耐药基因检测

对泰州地区分离的仔猪腹泻源大肠杆菌的耐药性及其携带的相关耐药基因情况进行检测,为养殖场今后合理用药提供科学依据。采用微量肉汤稀释法对分离的49株大肠杆菌进行8种抗菌药物的药敏试验;采用PCR方法对多黏菌素耐药基因mcr-1及超广谱β-内酰胺酶(ESBL)耐药基因blaCTX-M、blaSHV和blaTEM进行检测。药敏试验结果显示:大肠杆菌对氯霉素、氟苯尼考、氨苄西林、四环素、庆大霉素和恩诺沙星等的耐药率分别达到100%、97.96%、95.92%、89.80%、59.18%和51.02%;而对多黏菌素E和头孢噻呋的耐药率也达到44.90%和32.65%。进一步耐药基因检测结果显示:ESBL耐药基因中blaCTX-M的检出率最高,达到12.24%(6/49);其次为blaSHV,8.16%(4/49);有一株大肠杆菌携带blaTEM基因。其中一株同时携带blaCTX-M和blaSHV。多黏菌素耐药基因mcr-1的检出率达到30.61%(15/49),其中4株同时携带blaCTX-M基因。泰州地区分离大肠杆菌耐药情况和多重耐药现象较为严重,多黏菌素耐药基因mcr-1及ESBL耐药基因blaCTX-M、blaSHV和blaTEM的广泛分布表明这些耐药基因存在快速传播的风险。因此,有必要加强猪场细菌耐药性监测。     

Plasmid-mediated quinolone resistance gene detected in Escherichia coli from cattle

Fluoroquinolones resistance in bacteria can be due to chromosomal and plasmid-mediated mechanisms. Of growing concern is the acquisition of genes encoding quinolone resistance in combination with other resistance mechanisms such as extended-spectrum beta-lactamases. In this study we describe the identification of an isolate of Escherichia coli from cattle which carried qnrS1 in combination with a blaCTX-M gene, although they were not co-localised on the same plasmid. In addition, using a DNA array it was possible to identify several other antimicrobial resistance genes in this isolate. This is the first report of a qnr gene in E. coli from cattle in the UK and highlights the need for surveillance of these emerging resistance mechanisms.     

Antimicrobial susceptibility of pathogenic Escherichia coli isolated from sick cattle and pigs in Japan

We examined the 12 antimicrobial susceptibilities of 175 E. coli isolates from sick cattle and pigs by an agar dilution method. Resistance was found in 78.3% of isolates for oxytetracycline, 70.3% of isolates for dihydrostreptomycin, and 49.1% of isolates for ampicillin. When compared with healthy animals reported by Kijima-Tanaka et al., resistance rates for 11 antimicrobial agents were higher in sick cattle than in healthy cattle, and resistance rates for all antimicrobial agents were higher in sick pigs than in healthy pigs. Comparing cattle and pigs, resistance rates to colistin was higher in porcine isolates than in bovine isolates, but was lower in porcine isolates than in bovine isolates for cefazolin. With regard to the association of virulence factors, higher resistance rates to colistin and enrofloxacin were observed in STEC (61 strains) than in non-STEC (57 strains) among porcine isolates, while there were no significant differences in bovine isolates. In conclusion, these results can be considered helpful for adequate selection and prudent use of antimicrobial agents for several types of colibacillosis.     

Antimicrobial resistance and virulence factors in Escherichia coli from swedish dairy calves

Background

In Sweden, knowledge about the role of enteropathogenic Escherichia coli in neonatal calf diarrhea and the occurrence of antimicrobial resistance in E. coli from young calves is largely unknown. This has therapeutic concern and such knowledge is also required for prudent use of antimicrobials.

Methods

In a case control study Esherichia coli isolated from faecal samples from dairy calves were phenotyped by biochemical fingerprinting and analyzed for virulence genes by PCR. Antimicrobial susceptibility was tested by determination of minimum inhibitory concentration (MIC). Farm management data were collected and Fisher''s exact test and univariable and multivariable logistic regression analysis were performed.

Results

Of 95 E. coli tested for antimicrobial susceptibility 61% were resistant to one or more substances and 28% were multi-resistant. The virulence gene F5 (K99) was not found in any isolate. In total, 21 out of 40 of the investigated virulence genes were not detected or rarely detected. The virulence genes espP, irp, and fyuA were more common in resistant E. coli than in fully susceptible isolates (P < 0.05). The virulence gene terZ was associated with calf diarrhea (P ≤ 0.01).The participating 85 herds had a median herd size of 80 lactating cows. Herds with calf diarrhea problems were larger (> 55 cows; P < 0.001), had higher calf mortality (P ≤ 0.01) and calf group feeders were more in use (P < 0.05), compared to herds without calf diarrhea problems.There was no association between calf diarrhea and diversity of enteric E. coli.

Conclusions

Antimicrobial resistance was common in E. coli from pre-weaned dairy calves, occurring particularly in calves from herds experiencing calf diarrhea problems. The results indicate that more factors than use of antimicrobials influence the epidemiology of resistant E. coli.Enteropathogenic E. coli seems to be an uncommon cause of neonatal calf diarrhea in Swedish dairy herds. In practice, calf diarrhea should be regarded holistically in a context of infectious agents, calf immunity, management practices etc. We therefore advice against routine antimicrobial treatment and recommend that bacteriological cultures, followed by testing for antimicrobial susceptibility and for virulence factors, are used to guide decisions on such treatment.     

Characterisation of Escherichia coli O157 isolates from Danish cattle and human patients by genotyping and presence and variants of virulence genes

An important objective in vaccination strategies is to activate lymphocytes with particular effector functions. Cellular immunity and the type I cytokine IFN-gamma have been implicated in protective immunity to heartwater. Furthermore, low molecular weight proteins of Cowdria ruminantium have been shown to induce peripheral blood mononuclear cells to proliferate. To determine which lymphocyte subset responds when stimulated with fractionated C. ruminantium proteins, specific short-term lymphocyte cultures were established from cattle immunized with the Welgevonden isolate. Four cattle were immunized, two by infection and treatment and two with inactivated organisms. Cell surface phenotypic analysis of the cultures indicated that CD4+ lymphocytes were enriched over time. This coincided with increased antigen-specific proliferation and IFN-gamma production. Proteins of molecular weights 13-18kDa induced the CD4+-enriched T-cell cultures, derived from each of the animals, to proliferate and produce IFN-gamma. Although the two groups of cattle were immunized differently, their lymphocytes responded similarly. These results extend previous findings by identifying the responder cells as being predominantly IFN-gamma producing CD4+ lymphocytes. This cytokine has been implicated in immunity to the parasite. The low molecular weight proteins that induced CD4+ lymphocytes to proliferate and produce IFN-gamma are therefore likely to be important in protection against heartwater and may have a role in vaccine development.     

Prevalence of antimicrobial resistance and resistance genes in faecal Escherichia coli isolates recovered from healthy pets

Faecal samples of healthy dogs (n=39) and cats (n=36) obtained in Northern Portugal were seeded on Levine agar plates, and two Escherichia coli isolates per sample were recovered (78 of dogs and 66 of cats). The susceptibility to 16 antimicrobial agents was tested in this series of 144 E. coli isolates. Almost 20% of them showed tetracycline resistance and 12 and 15% presented ampicillin or streptomycin resistance, respectively. The percentage of resistance to the other antimicrobial agents was in all cases below 4%, and no resistant isolates were detected for ceftazidime, imipenem, cefoxitin or amikacin. Two isolates (from one dog) showed cefotaxime-resistance and harboured both the CTX-M-1 and OXA-30 beta-lactamases. A bla(TEM) gene was detected in 12 of 17 ampicillin-resistant isolates, the aac(3)-II gene in the three gentamicin-resistant isolates, aadA in 7 of 22 streptomycin-resistant isolates, and tet(A) and/or tet(B) gene in all 28 tetracycline-resistant isolates. The gene encoding class 1 integrase was detected in six E. coli isolates, including the four trimethoprim-sulfamethoxazole-resistant isolates and those two harbouring CTX-M-1 and OXA-30 beta-lactamases; different gene cassette arrangements were identified: dfrA1+aadA1 (two isolates), dfrA12+orfF+aadA2 (two isolates) and bla(OXA30)+aadA1 (two isolates). One amino acid change in GyrA protein (Ser83Leu or Asp87Tyr) was detected in four nalidixic acid-resistant and ciprofloxacin-susceptible isolates and two amino acid changes in GyrA (Ser83Leu+Asp87Asn) and one in ParC (Ser80Ile) were identified in one nalidixic acid- and ciprofloxacin-resistant isolate. Faecal E. coli isolates of healthy pets could be a reservoir of antimicrobial resistance genes.     

Passive transfer of antibodies to Shiga toxin-producing Escherichia coli O26, O111 and O157 antigens in neonatal calves by feeding colostrum

To study whether or not passive immunity of neonatal calves against Shiga toxin-producing Escherichia coli (STEC) O26, O111, and O157 was obtained by colostrum administration, serum antibodies in calves after the feeding were determined by enzyme-linked immunosorbent assay (ELISA) in comparison with antibodies in colostrum and sera from donor dams. The highest antibody titers to STEC in colostrum from dams were detected soon after parturition. The antibody titers were found to be elevated in sera of neonatal calves (4-9 hr after birth) orally administered with colostrum with high antibody titers, suggesting that passive immunity of neonatal calves to STEC infection may be obtained by feeding colostrum. These results suggest that colostrum administration to neonatal calves may play an important role in elevating serum antibodies against STEC in neonatal calves.     

Surveillance of dairy production holdings supplying raw milk to the farmhouse cheese sector for Escherichia coli O157, O26 and O111

Clinically healthy domestic animals can harbour Escherichia coli O157 and other verocytotoxigenic E. coli (VTEC) strains in their faeces. Milk filters can be used to microbiologically monitor direct milk secretion and environmental contamination for these pathogens. The aim of this study was to establish baseline data on the prevalence and characteristics of VTEC organisms in lactating animals (bovine, ovine and caprine) supplying milk to the farmhouse cheese sector, with particular emphasis on serogroups O157, O111 and O26. Fifty-six bovine, 13 caprine and 5 ovine herds/flocks, the majority of which supplying milk for farmhouse cheese production, were surveyed from May 2004 to July 2005. Milk filters were analysed by immunomagnetic separation followed by PCR, on a serogroup-specific basis for E. coli O157, O26 and O111. Positive isolates were examined using a multiplex PCR protocol, for their potential to produce verocytotoxins (vt1/vt2), the haemolysin-encoding gene (hlyA) and the gene encoding attaching and effacement (eae). Five verocytotoxigenic and 22 non-virulent E. coli O157 isolates were detected. Seventeen E. coli O26 isolates were also detected, four of which were verocytotoxigenic, seven isolates contained the eae gene only and six isolates were devoid of any of the virulence factors. The VTEC O157 and O26 isolates contained the hlyA and eae genes along with the verocytotoxin genes. No E. coli O111 isolates were detected. Some of the herds were positive on more than one occasion and multiple E. coli serogroups were isolated from the same milk filter sample. Although all food products tested were VTEC negative, routine surveillance for such pathogens in raw milk/raw milk products is of public health importance. Herd-level surveillance along with subsequent risk management action may be a cost-effective component of risk reduction strategies for food production, drinking water supplies and the protection of public health.     

Virulence characteristics of Escherichia coli isolates obtained from broiler breeders with salpingitis

Thirty isolates of Escherichia coli from broiler breeders with salpingitis were studied. Using the slide agglutination test, the isolates were found to belong to serogroups O1, O2, O5, O36, O45, O53 and O78. Pathogenicity for day-old chicks was determined by air sac inoculation and isolates were categorized as having high, intermediate or low virulence. Growth on iron starvation medium was observed together with aerobactin production. Based on the results of in vitro adherence tests, attachment to oviduct epithelium from old birds was found to be superior to that observed using corresponding material from young birds. DNA hybridization testing for type 1, P, and S fimbriae revealed predominant expression of type 1, correlating with mannose-sensitive hemagglutination using guinea-pig erythrocytes. In this study, P and S fimbriae were not considered to be important adherence factors. Study findings would suggest that, as far as salpingitis is concerned, type 1 fimbriae can play an important role in E. coli infection in breeders. An interesting result to emerge from the study was the observation that E. coli isolates were completely resistant to serum from young breeders, whereas they were completely sensitive using serum from older breeders. Based on serogroups involved, pathogenicity for day-old chicks and virulence indicators, the salpingitis isolates were similar to those from cases of chronic respiratory disease.     

Antimicrobial drug resistance in porcine enterotoxigenic Escherichia coli of 0-group 149 and non-enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) strains (104) and 96 non-ETEC, all isolated from herds with piglet diarrhea in 1981 and 1982, were investigated with regard to antimicrobial drug resistance and colicinogeny. Eighty strains (77%) of the ETEC were drug resistant as compared to 66 strains (69%) of the non-ETEC. There were no significant differences between ETEC and non-ETEC in the frequencies of the drug resistance determinants investigated, except for tetracycline, to which 51 (49%) of the former and 30 (31%) of the latter strains were resistant (0.05 greater than P greater than 0.01). Of all strains 116 (58%) were resistant to streptomycin, 93 (47%) to sulphadimidin, 81 (41%) to tetracycline, 20 (10%) to trimethoprim, 14 (7%) to ampicillin, 11 (6%) to neomycin, 6 (3%) to chloramphenicol and none to nitrofurantoin. The frequencies of the different drug resistance determinants correlated well with the total amount of active substance of each drug used in farm animals in Sweden in 1981. Of the ETEC, 97 (93%) were colicinogenic whereas only 13 (14%) of the non-ETEC were colicinogenic.     

Antimicrobial resistance in commensal faecal Escherichia coli of hospitalised horses

The objective of this study was to examine the impact of hospitalisation and antimicrobial drug administration on the prevalence of resistance in commensal faecal E. coli of horses. Faecal samples were collected from ten hospitalised horses treated with antimicrobials, ten hospitalised horses not treated with antimicrobials and nine non-hospitalised horses over a consecutive five day period and susceptibility testing was performed on isolated E. coli. Results revealed that hospitalisation alone was associated with increased prevalence of antimicrobial resistance and multidrug resistance in commensal E. coli of horses. Due to the risk of transfer of resistance between commensal and pathogenic bacteria, veterinarians need to be aware of possible resistance in commensal bacteria when treating hospitalised horses.     

Antimicrobial resistance in generic fecal Escherichia coli from 29 beef farms in Ontario

The occurrence of antimicrobial resistance in generic Escherichia coli can serve as an indicator of the pool of resistance genes potentially available for transfer to pathogenic organisms. This study was conducted on 29 volunteer beef farms in Ontario to describe the prevalence and patterns of antimicrobial resistance in E. coli, and to describe changes in the prevalence of resistance during the feedlot stage of production. From the pooled fecal samples on 28 of the 29 farms, 31% of isolates from feedlots (n = 993) and 12% of isolates from cow-calf farms (n = 807) were resistant to one or more of 16 antimicrobials tested. No isolates were resistant to ceftriaxone, ciprofloxacin, gentamicin, or nalidixic acid, and < 1% of the pooled isolates were resistant to ceftiofur. Two percent of both feedlot and cow-calf isolates were resistant to > or = 5 antimicrobials. Cow-calf farms were at significantly lower risk than feedlots for having E. coli isolates that were resistant to streptomycin, sulfamethoxazole, and tetracycline. On average, the prevalence of sulfamethoxazole resistant E. coli isolates was significantly higher in calves than in cows. No resistance was observed to ceftriaxone or ciprofloxacin among isolates (n = 1265) obtained from individually sampled feedlot animals on 2 farms. Less than 1% of these isolates were resistant to gentamicin, nalidixic acid, and ceftiofur. From the individually sampled feedlot animals, resistance to streptomycin (on 1 farm), sulfamethoxazole, and tetracycline increased significantly from arrival to mid-point during the feeding period, and these levels persisted until market-readiness.     

猪源大肠杆菌对20种抗生素的敏感试验

1935年第一个磺胺类药物-百浪多息的出现,开创了抗生素治疗的新纪元。抗生素的应用,对疾病的控制和预防发挥了巨大的作用,然而随着抗菌药物的广泛、持续和不当使用,细菌对抗菌药物的耐药性日趋普遍[1]。大肠杆菌是人和动物肠道的正常菌群成员之一,但某些血清型的大肠杆菌是病原菌,尤其对婴儿和幼畜(禽),常引起严重的腹泻和败血症。随着规模化养殖业的发展,病原性大肠杆菌对畜牧业所造成的损失已日益明显[2]。并且大肠杆菌血清型种类繁多,毒力因子组成各异,严重影响了临床大肠杆菌病的预防和控制。另一方面,随着细菌耐药性研究的不断深入,目…     

Antimicrobial resistance in fecal Escherichia coli isolated from growing chickens on commercial broiler farms

To investigate the effects of rearing practices of commercial broiler chickens on the incidence of antimicrobial resistance in commensal Escherichia coli isolates, fecal E. coli isolates obtained in 4 farms were screened for anitimicrobial resistance. Ten E. coli isolates were recovered from each of the fecal samples collected from 10 birds in the farms at the ages of 2 days, 14-17 days, and 47-50 days. In 2 out of the 4 farms, no antimicrobials were used during the rearing period. In the other two farms, following collection of the fecal samples at 14 and 15 days of age, oxytetracycline (OTC), sulfadimethoxine (SDMX), and tylosin were given to birds on one farm and SDMX was used in the other. Isolates resistant to ampicillin and OTC that were obtained from an untreated flock at different sampling times were closely related to each other by pulsed-field gel electrophoresis patterns (PFGE) of XbaI-digested chromosomal DNA. PFGE analysis together with in vitro conjugation experiments suggested that diversity of resistance phenotypes within a clone may be resulted from the acquisition and loss of R-plasmids in an untreated and a treated flock. The numbers of resistance phenotypes observed among fecal isolates increased during the growth of the chickens in all the farms. The results in the present study suggest that persistence of commensal E. coli strains resistant to antimicrobials even in the absence of antimicrobial administration. It is also hypothesized that horizontal transmission of resistance determinants resulted in the emergence of different resistance phenotypes in those farms.