Phenotypic and genotypic antimicrobial resistance patterns of Escherichia coli isolated from dairy cows with mastitis

Pulsed field gel electrophoresis (PFGE) patterns, susceptibility to 26 antimicrobial agents used in veterinary and human medicine, and prevalence of antimicrobial resistance genes of Escherichia coli isolated from cows with mastitis were evaluated. Among 135 E. coli isolates, PFGE analysis revealed 85 different genetic patterns. All E. coli were resistant to two or more antimicrobials in different combinations. Most E. coli were resistant to antimicrobials used in veterinary medicine including ampicillin (98.4%, >or=32 microg/ml) and many E. coli were resistant to streptomycin (40.3%, >or=64 microg/ml), sulfisoxazole (34.1%, >or=512 microg/ml), and tetracycline (24.8%, >or=16 microg/ml). Most E. coli were resistant to antimicrobials used in human medicine including aztreonam (97.7%, >or=32 microg/ml) and cefaclor (89.9%, >or=32 microg/ml). Some E. coli were resistant to nitrofurantoin (38%, >or=128 microg/ml), cefuroxime (22.5%, >or=32 microg/ml), fosfomycin (17.8%, >or=256 microg/ml). All E. coli were susceptible to ciprofloxacin and cinoxacin. Almost 97% (123 of 127) of ampicillin-resistant isolates carried ampC. Eleven of 52 (21.2%) streptomycin-resistant isolates carried strA, strB and aadA together and 29 streptomycin-resistant isolates (55.8%) carried aadA alone. Among 44 sulfisoxazole-resistant E. coli, 1 isolate (2.3%) carried both sulI and sulII, 12 (27.3%) carried sulI and 10 (22.7%) isolates carried sulII. Among 32 tetracycline-resistant isolates, 14 (43.8%) carried both tetA and tetC and 14 (43.8%) carried tetC. Results of this study demonstrated that E. coli from cows with mastitis were genotypically different, multidrug resistant and carried multiple resistance genes. These bacteria can be a reservoir for antimicrobial resistance genes and can play a role in the dissemination of antimicrobial resistance genes to other pathogenic and commensal bacteria in the dairy farm environment.     

种鹅大肠杆菌分离鉴定及耐药性分析

为了解种鹅致病性大肠杆菌病的病原及其药物敏感性,2012年从广东地区患病种鹅器官和粪便中分离鉴定了62株大肠杆菌,采用琼脂稀释法测定了大肠杆菌对17种抗菌药物的敏感性。结果发现大肠杆菌耐药性严重,对大部分药物的耐药率超过60.0%,仅对头孢西丁、头孢他啶和黏菌素较敏感。联合药敏试验结果显示多西环素和氟苯尼考联用对耐药大肠杆菌产生协同抑菌作用,FIC指数为0.375～0.75。采用脉冲场凝胶电泳（PFGE）法对24株大肠杆菌进行分型,结果分为17种不同的PFGE型别。大肠杆菌系统进化分群结果显示43.5%属于系统进化组群的D组,其次是A组和B1组,分别为34.8%和21.7%,B2组未检测到。通过对种鹅大肠杆菌耐药性、PFGE分型及其系统发育群进行综合分析,为临床用药提供了参考依据。     

Prevalence of ESBLs and PMQR genes in fecal Escherichia coli isolated from the non-human primates in six zoos in China

The aim of this study is to characterize the prevalence of extended-spectrum β-lactamases (ESBLs) and plasmid-mediated quinolone resistance (PMQR) genes in Escherichia coli from captive non-human primates. A total of 206 E. coli isolates were collected from primates in six zoos in China in 2009 and their susceptibility to 10 antimicrobials were tested by broth microdilution. The susceptibility patterns of E. coli strains varied greatly among different zoos reflecting different backgrounds of antimicrobial usage. Both the ESBL-encoding genes and the PMQR genes were detected by PCR. Of the 206 strains, 65 (32%) were confirmed as phenotypic ESBL producers with bla(CTX-M) (27%, bla(CTX-M-15), n=31, bla(CTX-M-3), n=23 and bla(CTX-M-14), n=2) mainly mediating the ESBL phenotype. qnrS1 (18%, n=36) and oqxAB (15%, n=31) were the predominant PMQR genes and the prevalence of PMQR genes was much higher among phenotypic ESBL producers than that among phenotypic non-ESBL producers from any zoo. Notably, the PMQR genes qnrS1 and oqxAB and β-lactamase genes bla(TEM-1) and bla(CTX-M-3) were found together in 23 E. coli isolates in two zoos in Shanghai. PFGE analysis of these 23 isolates demonstrated nearly identical PFGE profiles (similarity matrix >97%) indicating this specific E. coli genotype was prevalent in these two zoos. To the best of our knowledge, this is the first report of these four genes coexisting in an E. coli genotype and the first report of antimicrobial resistance profiles in E. coli isolated from primates in China.     

The characterisation of E. coli O157:H7 isolates from cattle faeces and feedlot environment using PFGE

The objectives of this study were to investigate the diversity of Escherichia coli O157:H7 isolates obtained over a 3-month period from a cattle feedlot in order to assess the relationship between environmental and faecal isolates and to determine the pattern of transmission of E. coli O157:H7 between groups of cattle. Faecal samples were obtained from cattle housed in four adjacent feedlot pens at monthly intervals, with environmental pen samples collected simultaneously. All E. coli O157:H7 isolates obtained were examined by pulsed field gel electrophoresis (PFGE), polymerase chain reaction (PCR) to detect eaeA, ehxA, stx1 and stx2 genes and antibiotic sensitivity profiling. Ten isolates were subjected to acid shock to imitate conditions in the acidic cattle abomasum and assess the effect on PFGE profiles. E. coli O157:H7 was isolated from 69 faecal samples and 26 environmental samples. All isolates (n=95) carried the genes for eaeA, ehxA and stx2 and were sensitive to all antibiotics tested. The PFGE profiles of all isolates differed by no more than two bands and clustered within 80% similarity following dendrogram analysis. Acid shock had no effect on the subsequent PFGE patterns. A total of 8.7% (6/69) of cattle were shedding E. coli O157:H7 in the first month with faecal shedding increasing to 52% (36/69) by the third month of the study. A single isolate of E. coli O157:H7 may be passed rapidly through cattle pens, with the environment acting as a significant reservoir for transmission. PFGE is a useful tool for tracking the direct and indirect transmission of E. coli O157:H7 isolates on the farm.     

Phylogenetic background, virulence gene profiles, and genomic diversity in commensal Escherichia coli isolated from ten mammal species living in one zoo

Three hundred commensal Escherichia coli recovered from healthy herbivorous, carnivorous, and omnivorous mammals from one zoo were characterized for their phylogenetic origin, intestinal virulence gene (VG) prevalence, and genomic diversity. The phylogenetic structure of the E. coli (groups A, B1, B2, and D) from the herbivores was homogenous, with a prevailing representation of group B1. In the carnivores and omnivores, the phylogenetic diversity was species specific with a higher representation of group A compared to the herbivores. Of 16 intestinal VGs in the whole set, 8 were detected and they formed 13 VG profiles. In the herbivores, all the VG-positive isolates belonged to group B1 and harboured the genes eaeA, eastI, ehxA, stx1, and stx2, which separately or in combination formed 8 VG profiles. In the carnivores and omnivores, the VG-positive isolates frequently belonged to group A and harboured the estI and estII genes or a combination of eastI and estI, forming three VG profiles. Single genes cnf2, in group B2, and eastI, in group D, were found. Similarity analysis of pulsed-field gel electrophoresis (PFGE) patterns revealed closer relatedness between the isolates from carnivores and omnivores than those from herbivores. The comparison between the prevalence of phylogenetic groups and the phylogenetic origin of VG-positive isolates in the examined E. coli suggested, that E. coli from group B1 in herbivores and E. coli from group A rather than B1 in carnivores and omnivores are "best adapted" to the host organism. The groups revealed different preferences in the acquisition and maintenance of intestinal VGs.     

Characterization of pathogenic Escherichia coli isolated from humans in Austria: phenotypes, toxin gene types and epidemiology

One hundred and ten clinical Escherichia coli isolates of serovar O157 (n = 102) and O26 (n = 8) were characterized for the presence of putative virulence genes by PCR. All but one of these isolates contained the eae gene. The EHEC-hly gene could be detected in all E. coli O157 and in 50% of E. coli O26 isolates. Forty-five (40.9%) of the 110 E. coli were positive for both stx(1) and stx(2) genes, 2 (1.8%) isolates were positive for stx(1) and 57 isolates (51.8%) were positive for stx(2) only. Among the 102 stx(2) positive isolates, 14 (13.7%) E. coli O157 contained also the stx(2c) variant gene. No other stx(2) variant was identified. Six clinical isolates (five E. coli O157:H7 and one E. coli O26) did not contain stx genes. Ten non-pathogenic E. coli isolates which were amplified as controls didn't contain any stx and eae gene but two of the ten strains contained the EHEC-hly gene. By their growth on chromogenic media, all but two of 50 E. coli O157 could be differentiated from eight E. coli O26 and 10 non-pathogenic E. coli. Sixty-one of the O157:H7 isolates were further subjected to pulsed-field gel electrophoresis (PFGE) which identified 49 distinguishable patterns. In five cases where contact infection among family members was suspected, indistinguishable PFGE patterns confirmed the epidemiological relatedness of the isolates. Moreover, two PFGE clusters were identified which comprised five and three strains, respectively. These findings indicate the occurrence of both family and diffuse outbreaks of E. coli O157 infections in Austria during recent years and demonstrate the need for molecular subtyping of these pathogens.     

Transmission of multiple antimicrobial-resistant Staphylococcus intermedius between dogs affected by deep pyoderma and their owners

The occurrence of antimicrobial-resistant Staphylococcus intermedius strains was investigated in 13 dogs affected by deep pyoderma, their owners and 13 individuals without daily contact with dogs (control group). A total of 90 canine and 33 human S. intermedius isolates were typed by pulsed field gel electrophoresis (PFGE) to determine their possible identity. The occurrence of S. intermedius in dog-owners was significantly higher compared with the control group (Fisher's exact test, P=0.03), with S. intermedius being detected in seven dog-owners and in one individual not exposed to dogs. The results of the PFGE analysis showed that six out of 13 (46%) owners carried strains identical to those isolated from their dogs. Strains detected in both dogs and humans were resistant up to five different antimicrobial classes, including penicillins, fusidic acid, macrolides/lincosamides, tetracycline and chloramphenicol. Based on the results of this study, owners of dogs affected by deep pyoderma often carry multiple antimicrobial-resistant strains of S. intermedius occurring in their dogs. Independent of the direction and modalities of transmission, this finding raises questions concerning the possible transfer of resistance genes from canine S. intermedius to human pathogenic staphylococci.     

Prevalence and patterns of antimicrobial resistance of fecal Escherichia coli among pigs on 47 farrow-to-finish farms with different in-feed medication policies in Ontario and British Columbia

The main objectives of this study were to determine the prevalence and patterns of antimicrobial resistance in pigs on farms that medicated swine ration and those that did not. A total of 940 isolates of Escherichia coli from 188 pooled fecal samples obtained from weaner and finisher pigs on 47 farrow-to-finish swine farms (34 farms used in-feed medication and 13 did not) were tested for susceptibility to 21 antimicrobials using a breakpoint concentration method. The prevalence of resistance varied widely (0.0% to 81.3%) among the antimicrobials tested. Ninety percent of all the isolates tested were resistant to one or more antimicrobials. The most common multi-drug resistance patterns were to 2 to 6 antimicrobials. Resistance was significantly more frequent (P < 0.01) on farms that used in-feed medication compared to those that did not, and significantly more frequent (P < 0.01) in weaner pigs compared to finisher pigs. These findings indicate that resistance to a broad range of antimicrobials was prevalent among fecal E. coli isolates of pigs on study farms, and that this constitutes a potential reservoir for resistance genes that could spread to pathogens. The findings also provide further evidence that use of medication in swine rations provides selective pressure for antimicrobial resistance in E. coli in pigs.     

Uropathogenic virulence factors in isolates of Escherichia coli from clinical cases of canine pyometra and feces of healthy bitches

Escherichia coli is commonly isolated in canine pyometra, but little is known of the virulence factors that may be involved in the precipitation of this disease. The aim of this study was to compare the prevalence of uropathogenic virulence factor (UVF) genes in E. coli isolates from canine pyometra and from feces of healthy bitches to evaluate their role in the pathogenesis of pyometra. E. coli from 23 cases of canine pyometra and from the feces of 24 healthy bitches were analyzed, by polymerase chain reaction, for UVF genes associated with canine and human urinary tract infections (UTIs). The prevalences of UVFs in E. coli from canine pyometra were similar to that in canine and human uropathogenic E. coli. The prevalence of pap was greater (P=0.036) for E. coli from pyometra (52%) than for fecal isolates (21%), and the papGIII allele was present in all pap-containing isolates. The prevalences of genes for alpha-haemolysin and cytotoxic necrotising factor 1 were not significantly higher (P=0.075) in E. coli from pyometra than from feces. The proportion of pyometra strains with >or=3 UVFs was higher (P=0.039) than that of fecal strains, suggesting that possession of >or=3 UVF genes enhances the pathogenicity of the strain. Our findings demonstrate that E. coli associated with canine pyometra are similar to uropathogenic strains, and that operons that encode P fimbriae, alpha-haemolysin and cytotoxic necrotising factor 1 probably enhance the virulence and pathogenicity of the strain in the canine genital tract.     

Antimicrobial susceptibility of Escherichia coli isolates from dairy farms using organic versus conventional production methods

OBJECTIVE: To compare antimicrobial susceptibility patterns of Escherichia coli isolates cultured from fecal samples from cows and calves on dairy farms that used organic (ie, no or severely limited antimicrobial use) versus conventional production methods. DESIGN: Cross-sectional study. SAMPLE POPULATION: Fecal samples from 10 cows and 10 calves on each of 30 organic dairy farms and 30 neighboring conventional dairy farms in Wisconsin. PROCEDURE: E. coli isolates obtained from the fecal samples were tested for susceptibility to 17 antimicrobials by means of a microbroth dilution test. Prevalence of antimicrobial resistance was compared between organic and conventional dairy farms. RESULTS: E. coli was isolated from 1,121 (94%) fecal samples. Farm type (organic vs conventional) and animal age (cow vs calf) were significantly associated with odds that E. coli isolates would be resistant to various antimicrobials. After controlling for age, logistic regression analyses indicated that isolates from conventional dairy farms had significantly higher rates of resistance to ampicillin, streptomycin, kanamycin, gentamicin, chloramphenicol, tetracycline, and sulfamethoxazole than did isolates from organic dairy farms. However, no significant differences were detected for the 10 other antimicrobials that were tested. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that compared with isolates from conventional dairy farms, E. coli isolates from organic dairy herds have significantly lower prevalences of resistance to 7 antimicrobials; however, prevalence of resistance was not significantly different for 10 other antimicrobials. Resistance was more common for isolates from calves than for isolates from adult dairy cows.     

Clonal spread of antimicrobial-resistant Escherichia coli isolates among pups in two kennels

Although the dog breeding industry is common in many countries, the presence of antimicrobial resistant bacteria among pups in kennels has been infrequently investigated. This study was conducted to better understand the epidemiology of antimicrobial-resistant Escherichia coli isolates from kennel pups not treated with antimicrobials. We investigated susceptibilities to 11 antimicrobials, and prevalence of extended-spectrum β-lactamase (ESBL) in 86 faecal E. coli isolates from 43 pups in two kennels. Genetic relatedness among all isolates was assessed using pulsed-field gel electrophoresis (PFGE). Susceptibility tests revealed that 76% of the isolates were resistant to one or more of tested antimicrobials, with resistance to dihydrostreptomycin most frequently encountered (66.3%) followed by ampicillin (60.5%), trimethoprim-sulfamethoxazole (41.9%), oxytetracycline (26.7%), and chloramphenicol (26.7%). Multidrug resistance, defined as resistance against two or more classes of antimicrobials, was observed in 52 (60.5%) isolates. Three pups in one kennel harboured SHV-12 ESBL-producing isolates. A comparison between the two kennels showed that frequencies of resistance against seven antimicrobials and the variation in resistant phenotypes differed significantly. Analysis by PFGE revealed that clone sharing rates among pups of the same litters were not significantly different in both kennels (64.0% vs. 88.9%), whereas the rates among pups from different litters were significantly different between the two kennels (72.0% vs. 33.3%, P < 0.05). The pups in the two kennels had antimicrobial-resistant E. coli clones, including multidrug-resistant and ESBL-producing clones. It is likely that resistant and susceptible bacteria can clonally spread among the same and/or different litters thus affecting the resistance prevalence.     

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.     

International disease surveillance. International disease monitoring, October to December 2004

To assess whether the rates of antimicrobial susceptibility in bacteria isolated from the urine of dogs with urinary tract infections are similar to those of bacteria isolated from bitches with pyometra, the antimicrobial resistance of Escherichia coli isolated from the two groups were determined and compared. The samples were collected in Sweden between April 2002 and March 2003, and potential changes over time were assessed by comparing the results with corresponding data from 1991 to 1993. Among 80 isolates of E coli from cases of pyometra, the proportions that were resistant to the antimicrobials used in canine practice were generally low (ampicillin 10 per cent, enrofloxacin 4 per cent, gentamicin 0 per cent, streptomycin 5 per cent, sulfamethoxazole 8 per cent, tetracycline 4 per cent and trimethoprim 2 per cent) and similar to the proportions reported previously. Significantly lower proportions of resistance were recorded among the pyometra isolates than among 92 isolates from urine samples submitted by animal hospitals to ampicillin (P=0.04), streptomycin (P=0.002) and tetracycline (P=0.03), but there were no differences between the pyometra isolates and 113 isolates from urine samples submitted by animal clinics.     

Detection of a novel clone of Acinetobacter baumannii isolated from a dog with otitis externa

In this study, the isolation of Acinetobacter baumannii in a dog with clinical bilateral otitis externa is described. Moreover, to investigate the zoonotic potential of the isolate, microbiological examinations on the family members were performed. An A. baumanniistrain was isolated from nasal swab in one of the dog owners. The identity of bacterial strains, either from dog and owner, was confirmed by phenotypic and molecular typing (wgMLST). Furthermore, to assess the pathogenic potential of the isolates a deep characterization of virulence and antibiotic resistance genes was done by Whole Genome Sequencing (WGS). Finally, the susceptibility towards a wide panel of antimicrobials was investigated. In our knowledge, this is the first recorded case of A. baumanniiisolation from canine auricular swabs in Italy. And interestingly, this study underlines the possible spread of this microorganism from human to animal.     

Molecular epidemiology of Salmonella Heidelberg in an equine hospital

From 1992 to 1997, multi-drug resistant (MDR) Salmonella Heidelberg isolates were cultured from a number of horses hospitalised in a veterinary hospital in Victoria, Australia. To examine the relationships between the cases, 28 isolates from the hospital were compared by pulsed field gel electrophoresis (PFGE), IS200 element profiles, antimicrobial resistance patterns, plasmid profiles and phage typing. The PFGE patterns following digestion with XbaI and BlnI restriction endonucleases showed that the isolates from the veterinary hospital originated from a common source. These isolates also had indistinguishable IS200 profiles. However, PFGE was more discriminatory than IS200 profiles. All the veterinary hospital isolates and one independent isolate had the same antimicrobial resistance pattern and had at least one plasmid in common. Localisation of antimicrobial resistance genes indicated that the veterinary hospital isolates had more than one plasmid carrying resistance genes and that the genes encoding sulphathiazole and trimethoprim resistance were not on these plasmids. Phage typing was ineffective as 22 of the 28 isolates were untypeable. In conclusion, the combination of different methods used for epidemiological studies suggested that a single strain of MDR S. Heidelberg was isolated from horses admitted to the hospital for 6 years and caused salmonellosis in susceptible horses within that period with no apparent correlation between the antimicrobials used and retention of its MDR phenotype.     

Antimicrobial susceptibilities, serogroups, and molecular characterization of avian pathogenic Escherichia coli isolates in Japan

In total, 83 avian pathogenic Escherichia coli (APEC) isolates from avian colibacillosis during a period from 2001 to 2006 in Japan were investigated for serogroups, typical virulence factors, antimicrobial susceptibility, and genetic relatedness. The most common serogroup was O78 (30.1%); 80.7% of isolates harbored the iss gene and 55.4% of isolates harbored the tsh gene. Antimicrobial resistance of the isolates was found for ampicillin (77.1%), oxytetracycline (75.9%), kanamycin (36.1%), fradiomycin (33.7%), trimethoprim (25.3%), enrofloxacin (21.7%), and florfenicol (6.0%). Although multiple antimicrobial-resistant phenotypes (three or more antimicrobials) accounted for 54.2% of isolates, no isolate exhibited resistance to all agents tested. The fluoroquinolone-resistant isolates had point mutations in GyrA (Ser83 --> Leu, Asp87 --> Asn) and ParC (Ser80 --> Ile, Glu84 --> Gly). Of 18 enrofloxacin-resistant E. coli isolates, nine isolates belonged to serotype O78. In PFGE analysis, eight of the nine enrofloxacin-resistant O78 isolates were classified into an identical cluster. This suggests that a specific genotype of fluoroquinolone-resistant O78 APEC may be widely distributed in Japan.     

Mutant-prevention concentrations of enrofloxacin for Escherichia coli isolates from chickens

OBJECTIVE: To investigate the development of enrofloxacin resistance among Escherichia coli isolates obtained from chickens by determining mutant-prevention concentrations (MPCs) and sequence the quinolone resistance-determining regions (QRDRs) of gyrA and parC genes in selected isolates. SAMPLE POPULATION: 15 chicken-derived E coli isolates. PROCEDURES: For all isolates, MPC and minimal inhibition concentration (MIC) of enrofloxacin were determined. The MPCs and maximum serum drug concentrations attained with enrofloxacin doses recommended for treatment of E coli infections in chickens were compared. Mutation frequencies and QRDR sequence changes in gyrA and parC were also determined. RESULTS: In 2 of 15 E coli strains, MPCs were low (0.016 and 0.062 microg/mL), MPC:MIC ratios were 2 and 4, and the GyrA and ParC proteins had no mutations. In 9 susceptible isolates with a GyrA point mutation, MPCs ranged from 2 to 16 microg/mL. For isolates with double mutations in GyrA and a single mutation in ParC, MPCs were > 32 microg/mL (several fold greater than the maximal plasma concentration of enrofloxacin in chickens); mutation frequencies were also much lower, compared with frequencies for single-mutation isolates. CONCLUSIONS AND CLINICAL RELEVANCE: For E coli infections of chickens, MPC appears to be useful for determining enrofloxacin-dosing strategies. The high MPC:MIC ratio may result in enrofloxacin-treatment failure in chickens infected with some wild-type gyrA E coli isolates despite the isolates' enrofloxacin susceptibility (MICs 0.125 to 1 microg/mL). For infections involving isolates with high MPCs, especially those containing mutations in gyrA and parC genes, treatment with combinations of antimicrobials should be adopted.     

Comparison of antimicrobial resistance in generic Escherichia coli and Salmonella spp. cultured from identical fecal samples in finishing swine

The objectives of this study were to investigate the associations between antimicrobial resistance patterns in generic Escherichia coli and Salmonella spp. isolates recovered from identical pen pooled fecal samples, and to evaluate potential clustering of multiple isolates of these organisms within identical fecal samples. Up to 5 generic E. coli (n = 922 isolates) and Salmonella spp. (n = 922 isolates) isolates were obtained from each of 188 pen pooled fecal samples that had been collected from 45 finishing swine farms in Alberta in 2000, and tested for susceptibility to 15 antimicrobials. No isolates of either organism were resistant to 3rd generation cephalosporins or fluoroquinolones, which in Canada are considered antimicrobials of very high importance to human health. Approximately twice as many generic E. coli isolates as Salmonella spp. isolates were resistant to at least 1 antimicrobial. In addition, E. coli isolates showed more multidrug-resistance patterns. No significant association was observed between the resistance phenotypes of Salmonella spp. and E. coli at the fecal sample level. More clustering at the sample level was observed for proportions of antimicrobial resistance (AMR) in Salmonella spp. isolates than E. coli indicating that in future studies it might be sufficient to test fewer than 5 Salmonella spp. isolates per sample.     

Characterization of Escherichia coli strains obtained from layer chickens affected with colibacillosis in a commercial egg-producing farm

The present study reports colibacillosis of layer chickens in a commercial egg-producing farm in western Japan. Three flocks of chicken at 18-21 weeks of age were affected during the initiation of egg lay. Postmortem examination revealed pericarditis, perihepatitis, airsacculitis, subcutaneous inguinal lesion, and injured cloaca. Escherichia coli was isolated from the lesions of the affected birds. Twenty-two of 26 E. coli isolates (84.6%) obtained from 18 birds in the 3 flocks showed pulsed-field gel electrophoresis (PFGE) patterns that were considered to be closely associated to each other and arbitrarily designated as pattern A. All the 22 isolates with the PFGE pattern A harbored the putative virulence genes, astA, iss, iucD, tsh, and cva/cvi. Additional 2 PFGE patterns (B and C) were also found in E. coli isolates obtained from the affected flocks and had the putative virulence genes in combinations different from those in the pattern A strains. The results suggested that certain E. coli virulence genes and host factors, such as initiation of egg lay may be associated with occurrence of colibacillosis.     

Susceptibility of canine and feline Escherichia coli and canine Staphylococcus intermedius isolates to fluoroquinolones

OBJECTIVES AND DESIGN: 1) A prospective study to determine in vitro concentrations for a range of fluoroquinolones, gentamicin and amoxycillin-clavulanate required to inhibit growth of recently collected, feline and canine Escherichia coli and canine Staphylococcus intermedius isolates. 2) A comparative retrospective study to compare the minimum inhibitory concentrations (MICs) of ciprofloxacin, enrofloxacin and amoxycillin-clavulanate for archived canine E coli and S intermedius isolates collected ten to twenty years earlier, with those for recently collected isolates. PROCEDURE: Susceptibility was assessed using disk diffusion, agar dilution susceptibility testing and Epsilometer tests (E-tests) for both recently collected and archived isolates. RESULTS: All feline E coli isolates and recently collected canine S intermedius isolates were susceptible to all fluoroquinolones. There was a statistically significant increase in the MIC range of ciprofloxacin and enrofloxacin for recently collected E coli, and in the MIC range of amoxycillin-clavulanate for recently collected S intermedius isolates compared to archived isolates. Twelve of 59 recently collected canine E coli isolates were resistant to both ciprofloxacin and enrofloxacin. Resistant canine E coli isolates were associated with complicating host or infection site factors. CONCLUSION: This is the first report comparing the MICs for all veterinary fluoroquinolones currently available in Australia for a representative sample of canine and feline E coli and canine S intermedius isolates. Importantly, this study identified 12 of 59 canine E coli isolates resistant to fluoroquinolones and identified the development of low level resistance in canine E coli to ciprofloxacin and enrofloxacin and canine S intermedius to amoxycillin-clavulanate.