Virulence factors in Escherichia coli strains isolated from urinary tract infection and pyometra cases and from feces of healthy dogs

The aim of this study was to compare the prevalence of virulence genes in 158 Escherichia coli strains isolated from 51 clinical cases of UTIs, 52 of pyometra and from 55 fecal samples from healthy dogs by PCR. papC was found in 12 (23.5%) strains isolated from UTIs, 19 (36.5%) from pyometra and 10 (18.2%) from feces. papGII was observed in 3 (5.8%) strains from pyometra, and papGIII in 10 (19.6%) from UTIs, 15 (28.8%) from pyometra and 9 (16.4%) from feces. sfaS was detected in 22 (43.1%) strains from UTIs, 24 (46.1%) from pyometra and 19 (34.5%) from feces. hlyA was observed in 17 (33.3%) strains from UTIs, 18 (34.6%) from pyometra and 7 (12.7%) from feces, while cnf-1 was detected in 11 (21.6%) from UTIs, 21 (40.4%) from pyometra and 9 (16.4%) from feces. iucD was observed in 12 (23.5%) strains from UTIs, 9 (17.3%) from pyometra and 1 (1.8%) from feces. usp was found 17 (33.3%) isolates from UTIs and 36 (69.9%) from pyometra.     

Characterization of Escherichia coli isolated from healthy dogs

Five month old dogs from a Midwestern research kennel occasionally developed bloody diarrhea after shipment to other facilities. As previous diagnostic efforts failed to reveal any potential pathogens in feces from normal and diarrheic dogs, Escherichia coli was investigated for select virulence properties that may contribute to the occurrence of bloody diarrhea. Fecal swabs from 52 healthy dogs were examined for E. coli. Two hundred and sixty E. coli-like colonies were screened by PCR for the attaching and effacing (eae) gene, Shiga toxin (stx) genes, and the heat-stable enterotoxin type A (sta) gene. One hundred forty two of the 260 E. coli-like colonies (54.6%) from 43 dogs were eae or sta positive; and 60 of the eae and/or sta positive isolates were examined further. Among the 60 isolates, 23 (38.3%) possessed the eae gene, 32 (53.3%) possessed the sta gene, and five (8.3%) possessed both eae and sta genes (eae⁺/sta⁺). Of the 60 isolates, six sta⁺ and one eae⁺/sta⁺ isolates were hemolytic. When examined in the suckling mouse assay, five of six sta⁺ isolates and three of four eae⁺/sta⁺ isolates gave gut-to-remaining carcass ratios ≥0.083, indicating expression of heat-stable enterotoxin. These enterotoxin-producing isolates belonged to serogroups O42, O170, and O-negative.     

Antimicrobial resistance of Escherichia coli isolated from chickens

Faecal Escherichia coli isolated from healthy farm chickens, from farm chickens with avian influenza, and from chickens with diarrhoea were more resistant to antimicrobial agents (94-100%) than those isolated from healthy domestic chickens (20%). Transfer of drug resistance was readily achieved from strains isolated from both healthy and sick farm chickens, and from diarrhoeic chickens; it was more difficult to demonstrate in strains from domestic chickens. Resistant E. coli showing serotypes suspected to be enteropathogenic for man, i.e 0126:K71(B16), 044:K74 (L) and 0119:K69(B14), were isolated from faecal samples of healthy and sick farm chickens, but not from healthy domestic birds.     

Characteristics of alpha-hemolytic strains of Escherichia coli isolated from dogs with gastroenteritis

Twenty-four hemolysin producing (Hly+) strains of Escherichia coli isolated from dogs with gastroenteritis were investigated for their virulence markers and their phenotypic properties. The strains were distributed over eleven known E. coli O-serogroups and most of them were heterogeneous for their phenotypes. All strains were found to produce alpha-hemolysin which was detected by Southern hybridization and colony immunoblotting using a specific gene probe and a monoclonal antibody. Eight strains were carrying plasmids encoding alpha-hemolysin sequences (hly-plasmids) and 16 strains carried chromosomal hly-determinants. Twelve of the strains showed enterotoxic activities which were tested for in different assays. Among these, three O42:H37 and two O70:H-strains carrying hly-plasmids were found to harbour other plasmids encoding the heat-stable enterotoxin STA1. The other seven strains showing enterotoxicity in the ileal loop or the suckling mouse assay were negative for STA1, STA2, or LT. None of the 24 strains were positive for invasiveness or for production of Vero (Shiga-like) toxins. The production of alpha-hemolysin was closely associated with the production of cytotoxic necrotizing factor (CNF), which was detected in 17 of 24 strains. Of these, 16 elaborated CNF1 and one strain produced an unknown CNF type. Surprisingly, all strains carrying ST-plasmids and six of eight strains carrying hly-plasmids were negative for CNF. Thus, in canine E. coli strains CNF production seems to be closely associated with production of chromosomally encoded alpha-hemolysin whereas hly-plasmids are more often associated with ST-producing, CNF negative isolates.     

Cytotoxins in non-enterotoxigenic strains of Escherichia coli isolated from feces of diarrheic calves

We have examined the cytotoxic responses produced in HeLa and Vero cell cultures by sonicates from 15 non-enterotoxigenic (STa-, LT-) strains of E. coli, highly lethal for mice parenterally LD50 less than 3 X 10(7) CFU), which had been isolated from feces of diarrheic calves. Three types of cytotoxic responses were observed. Type 1 (five strains) consisted of enlargement, rounding and polynucleation of HeLa cells, an effect previously reported with cytotoxic necrotizing factor (CNF) in E. coli from infant and piglet enteritis. Type 2 toxicity (three strains and the control Vir strain S5) was also characterized by enlargement and polynucleation of HeLa cells, but in contrast to Type 2 effect, cells were elongated. Sonicates from the latter strains were lethal for chickens, producing the lesions previously described with Vir strains. Type 3 toxicity (two strains and the control VT strain H19), produced an extensive destruction of both Vero and HeLa cell cultures. Cytotoxic effects were completely abolished upon heating for 1 h at 60 degrees C for Type 1 and 2 extracts and at 80 degrees C for Type 3 extracts. Seroneutralization assays showed that cytotoxins of the same type were closely related antigenically. In addition, a slight cross-neutralization was observed between Type 1 (CNF) and Type 2 (Vir) toxins.     

Enrofloxacin resistance in Escherichia coli isolated from dogs with urinary tract infections

OBJECTIVE: To assess the strain heterogeneity of enrofloxacin-resistant Escherichia coli associated with urinary tract infections in dogs at a veterinary medical teaching hospital (VMTH). In addition, strains from other veterinary hospitals in California were compared with the VMTH strains to assess the geographic distribution of specific enrofloxacin-resistant E. coli isolates. DESIGN: Bacteriologic study. SAMPLE POPULATION: 56 isolates of E. coli from urine samples (43 isolates from dogs at the VMTH, 13 isolates from dogs from other veterinary clinics in California). PROCEDURES: Pulsed field gel electrophoresis was performed on 56 isolates of E. coli from urine samples from 56 dogs. All 56 isolates were tested for susceptibility to amoxicillin, chloramphenicol, enrofloxacin, tetracycline, trimethoprim-sulphamethoxazole, cephalexin, and ampicillin. Enrofloxacin usage data from 1994 to 1998 were obtained from the VMTH pharmacy. RESULTS: Several strains of enrofloxacin-resistant E. coli were collected from urine samples from the VMTH, and strains identical to those from the VMTH were collected from other veterinary clinics in California. For the isolates that did share similar DNA banding patterns, variable antibiotic resistance profiles were observed. CONCLUSIONS AND CLINICAL RELEVANCE: The increased occurrence of enrofloxacin-resistant E. coli from urine samples from dogs at the VMTH was not likely attributable to a single enrofloxacin-resistant clone but may be attributed to a collective increase in enrofloxacin resistance among uropathogenic E. coli in dogs in general.     

Serotypes and virulence factors of Escherichia coli strains isolated from dogs and cats

E. coli strains isolated from urine of dogs and cats with urinary tract infections (UTI) and from feces of healthy one's were serotyped, and the serotypes were correlated with uropathogenic virulence factors. The most prevalent O-serotypes, O4 and O6, were isolated from dogs and cats with UTI. In contrast, O11 and O102 strains were the most frequently found from feces of healthy dogs and cats. Most of type O4 and O6 strains possessed such virulence factors as pil, pap, sfa, hly, and cnf1, while most type O11 and O102 strains pil only or pil and aer. All strains of type O75 possessed afaI and aer. K1 antigen was negative in all strains obtained from UTI.     

Antibiotic resistance of Escherichia coli strains isolated from chickens with colisepticaemia in Morocco

Sixty-two strains of Escherichia coli were isolated in 58 farms from broiler chickens showing respiratory signs and lesions characteristic of avian colibacillosis. Serological examination of these strains showed that the types 078, 01 and 02 (for the somatic antigen) and K1 (for the capsular antigen) were the most frequently found. Newcastle disease virus was also isolated in two cases. All the strains of E. coli isolated were sensitive to colistin, flumequine and gentamicin. A few strains were resistant to neomycin, nalidixic acid and trimethoprim. The frequency of strains resistant to nitrofurans, sulfonamides, chloramphenicol, spectinomycin and ampicillin was intermediate. Most strains were resistant to tetracycline. Multiple resistance was common.     

Profile of Shiga toxin-producing Escherichia coli strains isolated from dogs and cats and genetic relationships with isolates from cattle, meat and humans

Pets can be reservoirs of Shiga toxin-producing Escherichia coli (STEC) strains. The aim of this study was to examine nine strains belonging to several serotypes (O91:H21, O91:H16, O178:H19, O8:H19, O22:H8, O22:HNT, ONT:H8), previously recovered from cats or dogs. To this end, we assessed a set of additional virulence genes (stx(2) subtype, subAB, ehxA, eae and saa), cytotoxic activity, and genetic relationships with strains isolated from cattle, meat and humans using pulsed-field gel electrophoresis (PFGE). Most of the isolates carried the stx(2) and/or stx(2vh-b) sequences, while only the O91:H21 isolate presented the mucus-activatable stx(2d) variant, as confirmed by sequencing the genes of subunits A and B. All the strains showed cytotoxic activity in cultured cells. One of the two O178:H19, selected for its high level of cytotoxicity in Vero cells, showed the ability to cause functional alterations in the human colon mucosa in vitro. None of the strains possessed the subAB, eae or saa genes and only the strains belonging to serotype O8:H19 carried the ehxA gene. The isolates shared 90-100% similarity by PFGE to epidemiologically unrelated strains of the corresponding serotypes recovered from cattle, meat or humans. Our results demonstrate that dogs and cats may have a role in the infection of humans by STEC, probably serving as a vehicle for bovine strains in the cycle of human infection, and thus emphasize the health risks for owners and their families.     

Antimicrobial susceptibility of Escherichia coli isolated from feces of wild cranes migrating to Kagoshima, Japan

Susceptibility to 13 antimicrobial agents was examined for 138 Escherichia coli isolates obtained from 192 fecal samples of wild cranes that migrated for wintering to the Izumi plain, Kagoshima prefecture in Japan. The numbers of isolates that were resistant to the antimicrobials used in this study are as follows: oxytetracycline (OTC), 22 isolates; minocycline, 7 isolates; ampicillin (ABPC), 4 isolates; nalidixic acid, 4 isolates; enrofloxacin, 2 isolates; kanamycin, one isolate. Multidrug resistant isolates exhibiting 2-4 drug resistances were obtained. All of the OTC-resistant isolates carried either the tet (A) or tet(B) gene. The bla(TEM) gene was found in all of the ABPC-resistant isolates.     

Haemolytic Escherichia coli isolated from dogs with diarrhea have characteristics of both uropathogenic and necrotoxigenic strains

Twenty-four haemolytic Escherichia coli strains were isolated from dogs with diarrhea. The strains were serotyped and analysed by polymerase chain reaction (PCR) for genes encoding virulence factors associated with E. coli that cause diarrhea in animals. Adhesion antigen production was deduced from haemagglutination experiments. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of heat extracts was also used as an indication for the production of adhesive structures. The majority of the strains was shown to produce this type of virulence factor. Adhesion and invasion tests of the strains and Caco-2 cells showed that all strains adhered and that two were invasive. The two invasive strains were positive in the intimin PCR and one of them also contained genes encoding CS31A. The PCR for heat stable toxin (ST) was positive in only four strains, as was the presence of F17 fimbrial genes. Surprisingly, 19 strains had intact P fimbrial operons, coding for an adhesin involved in urinary tract infection (UTI). The cytotoxic necrotising factor 1 (CNF1) gene, also mainly found in UTI was likewise detected in these 19 strains. Cytolethal distending toxin (Cdt) genes were found in five strains. The high number of strains positive for CNF1 and P fimbriae prompted us to test the strains in a multiplex PCR used to test E. coli isolated from UTI in various species for 30 virulence associated genes. The data showed that the majority of the diarrhea isolates have virulence factor profiles highly similar to UTI E. coli isolates from dogs. This raises the question whether these isolates are real intestinal pathogens or "innocent bystanders". However, since CNF1 producing necrotoxic E. coli (NTEC) strains isolated from humans, pigs and calves with diarrhea appear to be highly related to our strains, it might be that in dogs this type of isolate is capable of causing not only UTI, but also diarrhea. If this is the case and this type of isolate is "bifunctional", domestic animals likely constitute a reservoir of NTEC strains which can be also pathogenic for humans.     

我国健康猪源大肠杆菌对四环素类药物耐药性的Meta分析

旨在系统评价我国健康猪源大肠杆菌对四环素类药物耐药性的情况,为养殖业合理用药决策提供依据.计算机搜索PubMed、Web“sci-ence、SinoMed、CNKI等10个数据库.应用Revman 5.3软件进行Meta分析,并对各研究间异质性进行评价.共纳入20篇符合条件的研究,共4 343株分离自健康猪源的大肠杆菌...     

Antimicrobial susceptibility of Staphylococcus intermedius isolated from healthy and diseased dogs

A total of 90 strains of Staphylococcus intermedius isolated from dogs were examined for antimicrobial susceptibility. There were no significant differences in the distribution patterns of MICs between strains from 1982 to 1985 and those from 1999, and between strains from healthy dogs and those from diseased dogs. All of the strains were susceptible to ABPC, DMPPC, CEX, TDM, ERFX, BFLX, and FF at concentrations of 0.05 to 6.25 microg/ml. The MICs of OTC, KM, EM, AIV-TS, and LCM were distributed in a broad range of 0.1 to >100 microg/ml, indicating the existence of resistant as well as susceptible populations of S. intermedius. Thirty-three strains (36.7%) were resistant to one or more anitmicrobial agents such as OTC (n=32), KM (n=9), EM (n=7), AIV-TS (n=7), and LCM (n=7).     

Characterization of integrons-mediated antimicrobial resistance among Escherichia coli strains isolated from bovine mastitis

To assess the prevalence of antimicrobial resistance and class I integrons in Escherichia coli strains (n=58) isolated from bovine mastitis in Inner Mongolia, antimicrobial susceptibility and the presence of various types of integrons were characterized. Most isolates were susceptible to amikacin, colistin, ceftazidime, gentamicin and kanamycin, while those also exhibited high resistant incidence rates to ampicillin, amoxicillin, sulfadiazine and sulfamethoxydiazine. The integrase gene of integrons was amplified by PCR using degenerate primers. The integrons were confirmed by restriction fragment length polymorphism (RFLP) analysis of positive PCR products. Neither class II nor class III integron was detected, while 56.90% (n=33) of the isolates were positive for the presence of intI1 gene. Sequencing analysis of gene cassettes revealed that seven gene cassettes were found, which encoded resistance to trimethoprim (dfrA1 and dfrA17), aminoglycosides (aacA4, aadA1 and aadA5) and chloramphenicol (catB3), respectively. Of them, the gene cassette array dfrA17-aadA5 was found most prevalent (62.96%). The percentage of positive-integron among the isolates whose resistant profile was relatively broad (n> or =7) is 100.00%, while the one in narrow-profile isolates (n=2-6) is 30.56%. The correlation analysis revealed the incidence of integrons among the isolates were highly related to the resistant profile, indicating integrons play an important role in the dissemination and spread of the antimicrobial resistant strains.