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1.
Avian cellulitis in broiler chickens is primarily caused by Escherichia coli. Previous research found that the E. coli isolates of cellulitis origin were unique to each ranch, suggesting that these E. coli were endemic within the ranch environment. To test the hypothesis that the E. coli associated with cellulitis are endemic in the litter of the broiler house, we designed a study to determine whether E. coli DNA fingerprints associated with cellulitis persist over successive flocks that are grown in the same house. In addition, we assessed the impact of different cleaning and disinfection strategies on this persistence. Two broiler houses were followed on each of five farms over 3-4 flocks. A total of 353 E. coli isolates from cellulitis lesions were analyzed in this study, and 314 of these isolates (89%) were DNA fingerprinted by PFGE. In each ranch, there were several DNA fingerprint patterns that were present over successive flocks, regardless of the cleaning and disinfection strategy utilized. Isolates persisted as long as 191 days, implying that these E. coli are capable of persisting in the broiler house environment for long periods of time. In addition, these E. coli isolates were associated with cellulitis lesions in successive flocks. Thus, the isolates of E. coli that are associated with cellulitis in broiler chickens appear to be endemic in the litter environment of the broiler house.  相似文献   

2.
The purpose of this study was to identify Escherichia coli isolates that could be characterized as cellulitis pathogens. Twelve E. coli isolates from diagnostic cases of cellulitis or mixed infections with various serotypes were compared for ability to produce cellulitis and internal lesions indicative of systemic infection. Ranking of isolates was based on the premise that E. coli isolates that were "cellulitis-type" would cause cellulitis lesions without causing systemic infection. A quantitative scoring system was also used so both the time required for a lesion to develop and lesion severity could be evaluated as determinants of virulence. Escherichia coli isolates were inoculated by subcutaneous injection of a standardized dose in 24 broiler chickens per isolate. Necropsy was performed on four birds per group at 6, 12, 24, 36, 48, and 60 hr postinoculation (PI). Cellulitis lesions were scored on a 0 to 5 scale based on size, migration from the inoculation site, and gross characteristics. Lesions of the pericardium, liver, joint, or body cavity were evaluated. Gross lesion scores of 1 or 2 were evident by 6 hr PI with all isolates. Mortality occurred in 4 of 12 experimental groups. Internal lesions were observed in 3 to 12 birds per group. Escherichia coli was reisolated from all lesions. The four isolates with the highest lesion score and highest lesion points as determined by the quantitative scoring system did not vary. However, the rankings of two other isolates were affected. Four isolates that were below average for mean internal lesion score and above average for mean cellulitis points were characterized as cellulitis-type. Three isolates that were above average for internal lesion score and below average for mean cellulitis points were characterized as systemic-type. The E. coli serotype was not a determining factor for cellulitis-type pathogenicity. Isolates discriminated as cellulitis-type or septicemic-type E. coli in this study are being used to further investigate virulence factors involved in the pathogenesis of cellulitis in broiler chickens.  相似文献   

3.
Avian cellulitis in broiler chickens is characterized by subcutaneous lesions that result in economic losses because of the partial or complete condemnation of the carcasses at processing. Escherichia coli is the primary causative agent of this condition. Previous research with a biotyping system found that the E. coli of cellulitis origin were unique to each ranch, suggesting that these E. coli were endemic within the ranch environment. The objective of our study was to analyze the genetic variability of E. coli isolates associated with cellulitis. We analyzed the genetic relatedness of the isolates in relation to the houses, ranches, and complexes in which the broilers were grown. This analysis enabled us to assess the spatial heterogeneity, or genetic diversity on a spatial scale, of the isolates. Forty-nine broilers with cellulitis lesions were necropsied. These broilers came from six houses on four ranches on three complexes that had been placed with chicks from the same hatchery within a 2-wk period. Isolates of E. coli from the lesions were DNA fingerprinted by pulsed-field gel electrophoresis. Relatedness among isolates was determined with the Dice coefficient and an unweighted pair group method with average linkages cluster analysis. The complexes possessed isolates with a variety of DNA fingerprints, yet each complex appeared to have isolates with a unique set of DNA fingerprints. Isolates from the same complex tended to form clusters with similarity coefficients greater than 90%. Isolates from different complexes were genetically distinct. This heterogeneity at the level of the complex suggests that isolates were not disseminated from a source common to the complexes. The spatial heterogeneity of the E. coli isolates in this study implies an endemic population of cellulitis-associated E. coli exists in the broiler house environment.  相似文献   

4.
This study was designed to compare virulence factors of cellulitis-derived Escherichia coli to colisepticemic E. coli in order to clarify whether E. coli associated with cellulitis comprise a unique subset of pathogenic E. coli. Isolates were tested for serotype, capsule, aerobactin production, colicin production, the presence of the iss gene, and serum resistance. Untypable isolates made up the greatest percentage of each group. Serotypes O2 and O78 were the most commonly identified among both groups of isolates. No statistical differences in the distribution of aerobactin or colicin production, capsule, or iss gene were observed between groups. Cluster analysis showed that 90% of the E. coli isolates had greater than 42% livability in serum-resistance tests. No separation of colisepticemic vs. cellulitis E. coli isolates was observed on the basis of SR. Colicin production by E. coli was highly correlated with serum resistance (P = 0.0029). These data suggest that cellulitis E. coli have virulence traits similar to those of colisepticemic E. coli.  相似文献   

5.
Cellulitis has emerged as an economically important disease of broiler chickens. The impact of environmental risk factors on the incidence of cellulitis has not been evaluated in the United States. Escherichia coli (E. coli), the causative agent, is introduced through skin scratches during the grow out. Our previous work suggested that the litter was an important reservoir for cellulitis-associated E. coli. We hypothesized that factors contributing to a positive environment for E. coli growth would increase the opportunity for exposure of a broiler to an infectious dose of E. coli, capable of initiating a cellulitis lesion. This prospective study of 304 flocks on five farms from two integrated broiler companies was conducted to determine the effect of environmental factors on the prevalence of cellulitis in California broiler flocks. Environmental variables included temperature, wind velocity, and relative humidity (RH) at the litter surface. Litter variables measured included E. coli and total gram-negative bacteria load (colony forming units/g dry matter), water activity, and pH. Management variables such as clean out, the number of flocks reared on the same litter (litter run, LR), and downtime (DT) between flocks were also evaluated. Cellulitis ranged from 0.197% to 6.04%. Significant associations were identified using linear regression between farm, LR, DT, ambient temperature during the brooding period, gram-negative bacteria load in the litter during the brooding period, RH mid-grow out, and E. coli load late in the grow out. The significant variation in the rate of cellulitis between farms combined with the strong association of LR and DT with cellulitis demonstrated that management choices were highly influential in this disease syndrome. Based on these data and our previous findings, managers would be advised to increase DT between flocks and perform a total clean out of the house when a flock processes with a high incidence of cellulitis.  相似文献   

6.
The pathogenicity of 197 Escherichia coli isolates obtained from clinically affected commercially grown broiler chickens and normal hatchery chicks was assessed by inoculating day-old broilers intratracheally. The degree of pathogenicity (high, intermediate, low) was judged according to mortality and lesions occurring within 7 days following inoculation. Serotype, metabolic activity, motility, and in vitro antibiotic sensitivity of each isolate were evaluated and related to pathogenicity. Seventy-five of the isolates of high to intermediate pathogenicity belonged to serogroup O2, O78, or O35. In addition, 51 pathogenic E. coli isolates could not be serotyped, and several had multiple serotypes. Most isolates had similar metabolic activity, as determined by amino acid decarboxylation and carbohydrate fermentation, regardless of pathogenicity. An exception was the fermentation of adonitol, which occurred more frequently with the highly pathogenic strains. Motility and in vitro antibiotic sensitivity were not related to pathogenicity. An age-associated resistance to intratracheal E. coli administration occurred by 15 days of age in uncompromised birds. Relative susceptibility of birds older than 2 weeks to intratracheal and/or intravenous E. coli inoculation could be increased by prior exposure to pathogenic reovirus 1733, adenovirus 3167, or infectious bursal disease virus (IBDV). Birds infected with IBDV at 3 weeks failed to clear apathogenic and pathogenic E. coli from circulating blood.  相似文献   

7.
Four hundred twenty-nine isolates of Escherichia coli from calves were tested for the production of HeLa cell cytotoxin(s). Isolates that produced enough cytotoxin to be detected in culture supernatants of iron-depleted broth were considered to produce increased amounts of cytotoxins. Isolates also were tested for homology with a DNA probe for a gene that encodes localized adherence of human enteropathogenic E coli. Four isolates produced increased amounts of cytotoxin that was neutralized by Shiga antitoxin (toxin designated as Shiga-like toxin-I [SLT-I]). A 5th isolate produced increased amounts of cytotoxin (SLT+) that was not neutralized by the Shiga antitoxin, but was neutralized by antitoxin against a variant of SLT (toxin designated as SLT-II). None of the isolates hybridized with the probe for the localized adherence gene. Three of the SLT+ isolates belonged to human enteropathogenic E coli serogroups O26 and O111. All 5 of the SLT+ isolates were from calves with diarrhea, but none of the 5 SLT+ isolates contained genes for classic heat-labile or heat-stable enterotoxins, for K99 fimbriae, or for invasiveness; neither did any of them adhere to HeLa cells in culture. Three of the 5 SLT+ isolates had attaching and effacing activities when inoculated into ligated intestinal loops of rabbits. One of the isolates with attaching and effacing activity in rabbits was originally isolated from a calf with lesions characteristic of those produced by attaching effacing E coli (AEEC). Calves inoculated with this SLT+ AEEC isolate developed focal colonic lesions characteristic of those produced by AEEC, but did not develop diarrhea.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

8.
It has been shown that Escherichia coli isolates from lesions of cellulitis belong to a limited number of clonal groups distinct from those of isolates found in the environment of these birds. In this study, different in vitro methods were used to evaluate adherence properties of E. coli isolates from cellulitis lesions and environments of high- and low-cellulitis prevalence broiler flocks. One hundred isolates were tested by hemagglutination. Adherence to frozen sections of chicken skin and binding to soluble fibronectin were examined for 40 of these 100 isolates by immunofluorescence and by immunocytofluorometry, respectively. Localization of bacterial adherence to skin tissues was confirmed by immunohistochemistry. It was demonstrated that O78:K80 isolates from cellulitis lesions adhered to skin sections to a much greater extent in deeper than in superficial tissue layers. A greater bacterial adherence following growth in TSB at 37 C was demonstrated for isolates from flocks with high prevalence of cellulitis than for isolates from flocks with low prevalence of cellulitis. MANOVA analysis results showed a significant difference between superficial and deep tissue layers only for one set of isolates from flocks with high prevalence of cellulitis. Hemagglutinating activity was variable among the O78:K80 isolates obtained from flocks with high prevalence of cellulitis. The results obtained for some O78:K80 isolates following growth in TSB suggest a role for type 1 fimbriae or F1 in adherence to skin sections. This was reinforced by the finding that adherence was inhibited by D-mannose. Poultry E. coli isolates that express F1 had no affinity for soluble fibronectin, although localization of the adherence in skin sections suggested a role for extracellular matrix components such as collagen and insoluble fibronectin.  相似文献   

9.
Eleven avian adenoviruses were isolated in monolayer cultures of specific pathogen free chicken kidney cells which were inoculated with suspensions of liver, intestine or bursa obtained from 15 broiler flocks experiencing outbreaks of inclusion body hepatitis (10 isolates) and from five unaffected flocks (one isolate). Of the 11 isolates obtained, nine were identified by virus neutralisation tests as serotype 8, one as serotype 1 and one as serotype 12. Adeno-associated viruses were only observed in combination with adenoviral particles of the serotype 12 isolate which was derived from a relatively mild outbreak of inclusion body hepatitis. Only the serotype 1 isolate, obtained from the unaffected broiler flock, consistently caused the death of embryos with marked pathological changes. All of the isolates produced basophilic intranuclear inclusion bodies surrounded by clear halos in chicken kidney cell cultures. DNA preparations, obtained from six strains of serotype 8 avian adenovirus (two New Zealand isolates, three Australian isolates and the reference strain HVI) after digestion with the restriction enzymes EcoRI and BamHI, gave electrophoretic patterns showing the New Zealand isolates to be similar to one another and to strain HVI, but quite distinct from the Australian isolates.  相似文献   

10.
The role of birds as sources of Shiga toxin-and intimin-producing Escherichia coli was studied. Fecal samples from live gulls (n=86), pigeons (n=33) and broiler chickens (n=199) from 23 flocks were analyzed for stx and eae by PCR. No stx positive samples were detected. In contrast, eae E. coli were highly prevalent among gulls (40%), and was also found in pigeons (7%) and chickens (57% of the flocks contaminated). The eae positive isolates were analyzed genetically and O-serogrouped. One isolate from a pigeon was found to have stx (2f). The isolates of gulls differed from those of pigeons and chickens, and all eae E. coli isolates from birds differed from human pathogenic strains by the lack of EHEC-hlyA and bfp/EAF as well as distribution of O-serogroups. Thus, birds cannot be regarded as important carriers of zoonotic stx or eae E. coli in Finland.  相似文献   

11.
OBJECTIVE: To genetically type Campylobacter jejuni isolates from broiler houses or the external environment to identify the source of Campylobacter organisms in broiler chickens. SAMPLE POPULATION: Environmental samples associated with broiler chickens, in commercial grow-out houses. PROCEDURE: Polymerase chain reaction (PCR) was used to amplify flaB, and the amplicon was digested with Sau3A to create a restriction fragment length polymorphism assay; PCR was also used to detect a transcribed spacer region in the 23S rRNA gene. RESULTS: Isolates possessing a 23S spacer region were more prevalent outside broiler houses than inside. Houses that had previously contained chickens or lacked biosecurity procedures were more likely to contain isolates possessing the 23S spacer. One house contained only isolates possessing the spacer, whereas an adjacent house contained only isolates lacking the spacer. The flaB type detected in broiler houses was different from the type detected in the environment; however, many isolates within the broiler houses contained untypable flaB genotypes. CONCLUSIONS AND CLINICAL RELEVANCE: Most isolates from within houses were genetically distinct from isolates from outside houses that were examined by bacteriologic culture, suggesting an undetected source of C jejuni. Detection of isolates containing the 23S spacer appeared to be an indicator of environmental contamination of the houses. The observation of completely different C jejuni genetic types simultaneously within adjacent houses suggests that some types do not compete successfully during the grow-out period. In addition, the diversity of genotypes identified within broiler houses indicates the complexity of the ecologic features of C jejuni in the chicken environment.  相似文献   

12.
In the course of our molecular studies of virulence factors associated with invasive avian Escherichia coli infections, it was first necessary to distinguish between common E. coli and those that cause septicemia in poultry. We found a direct correlation between the ability of clinical isolates of E. coli to bind Congo red dye (CR) and their ability to cause septicemic infection in chickens. This finding was supported by bacteriological studies of 30 broiler flocks (26 sick and 4 healthy) and by virulence studies in chickens and mice. All 144 isolates of E. coli from internal tissues of diseased birds were determined to be CR-positive (red colonies). Congo-red-positive E. coli colonies were isolated from air sacs, pericardium, liver, lung, joint fluid, and heart blood of chickens with lesions of colisepticemia. In contrast, of 170 E. coli isolates from the poultry house environment and from the trachea and cloaca of healthy birds, more than half were CR-negative (white colonies). No CR-negative (white) E. coli colonies were found in internal organs from birds with typical lesions of colisepticemia. We feel that these preliminary findings suggest that the CR dye binding could be used as a phenotypic marker to distinguish between invasive and noninvasive isolates.  相似文献   

13.
In a previous study we investigated pulsed-field gel electrophoresis (PFGE) genotype diversity and prevalence of the netB toxin gene in Clostridium perfringens (CP) isolates recovered from a broiler flock (flock 1) affected by necrotic enteritis (NE). In this follow-up work, we examined samples collected before placement of flock 1, to see if NE during rearing could be traced back to the cleaned and empty building or the day-old chicks. Litter from the next flock in the same building (flock 2) was also examined. We detected 25 different PFGE genotypes, five of which were found only in litter from flock 2. Six genotypes which had been found in flock 1 during rearing were detected in samples collected before placement. NetB positive isolates belonging to two of these genotypes had been recovered from NE lesions during rearing, suggesting that virulent strains were transmitted from the cleaned and disinfected broiler house. NetB frequency among isolates from the empty building was 45%, indicating that netB positive strains were prevalent in a building that previously had housed a healthy flock offered in-feed narasin (flock 0). NetB frequency among isolates from litter used by flock 2 was 22%, indicating that netB positive strains were present in the environment of a 14-days-old healthy flock offered in-feed narasin. Two prevalent genotypes were consistently either netB negative or netB positive. However, the presence of genotypes represented by both negative and positive isolates may suggest that the gene can spread horizontally among different CP strains.  相似文献   

14.
OBJECTIVE: To determine whether duration of hospitalization in the intensive care unit (ICU) of a veterinary teaching hospital was associated with prevalence of antimicrobial resistance among rectal Escherichia coli isolates from dogs, whether antimicrobial treatment was associated with prevalence of antimicrobial resistance, and whether there were associations among antimicrobial drugs to which isolates were resistant. DESIGN: Prospective observational study. ANIMALS: 116 dogs hospitalized in an ICU for >or= 3 days. PROCEDURES: Rectal swab specimens were obtained every 3 days and submitted for bacterial culture for E coli. Isolates were tested for susceptibility to 12 antimicrobial agents by means of disk diffusion. RESULTS: For each additional day that a dog was hospitalized in the ICU, the odds of being colonized with an E coli isolate resistant to 1 or more of the 12 antimicrobials tested increased by a factor of 1.5, independent of antimicrobial treatment. Dogs that were treated with enrofloxacin were 25.6 times as likely to be colonized by a quinolone-resistant E coli strain as were dogs that did not receive any antimicrobials. Significant correlations were found for resistance to agents in the extended-spectrum cephalosporin group and the quinolone group. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that the proportion of rectal E coli isolates obtained from dogs housed for >or= 3 days in a veterinary teaching hospital ICU that were resistant to antimicrobial agents increased as the duration of hospitalization in the ICU increased. Thus, ICU hospitalization time should be as short as possible to prevent development of antimicrobial resistance among rectal E coli isolates.  相似文献   

15.
Erysipelothrix rhusiopathiae is well known to cause disease in dolphins. This disease occurs either in an peracute way, leading to mortality even before clinical signs are observed or in a sub-acute way, characterized by rhomboidal skin lesions, that can be treated with penicillin or its derivatives. Commercial swine vaccines, containing inactivated serotype 2 strains, are currently used for vaccination but it is not known whether these vaccines induce protection against E. rhusiopathiae isolates from dolphins. In the present study, it was demonstrated in a mouse model that vaccination with a commercial swine vaccine (Eurovac Ery, Eurovet, Belgium) containing inactivated serotype 2 E. rhusiopathiae strains induced protection against challenge with three E. rhusiopathiae isolates from dolphins. The duration of the protection varied, depending on the challenging isolate, between 8 and >23 weeks. There was however no positive correlation between the amount of antibodies at the moment of challenge and the observed protection.In conclusion, vaccination trials in mice indicate that commercial serotype 2 swine Erysipelothrix vaccines induce protection against erysipelas caused by dolphin pathogenic isolates.  相似文献   

16.
Gharaibeh S 《Avian diseases》2008,52(1):106-110
A low pathogenic avian influenza virus (AIV) serotype H9N2 affected many commercial flocks in the Middle East in late 1990s and early 2000s. Due to the varying pathogenicity ofAIV H9N2 reported in previous studies, this study was carried out to determine the pathogenicity of a Jordanian isolate of H9N2 in broiler and specific-pathogen-free (SPF) chickens. Mild tracheal rales were observed in the broilers but not in the SPF birds starting 3 days postinfection (DPI) and until the end of the experiment at 16 DPI. Infected chickens had gross and histologic changes limited to the respiratory system (sinuses, trachea, lungs, and air sacs) characterized by congestion and lymphoplasmacytic inflammation. However, the lesions in the broiler chickens were more severe than those in the SPF chicks. Furthermore, the virus caused significant (P = 0.004) reduction (230 g) in average body weight of the infected broiler group compared with the uninfected broiler group. Both broiler and SPF-infected groups seroconverted, and they had a geometric mean titer of 2(8.2) and 2(9.3), respectively, on the hemagglutination inhibition test at 16 DPI. Cloacal virus shedding was not detected by 9 DPI and 15 DPI in broiler and SPF-infected groups, respectively. This study demonstrated the pathogenic nature of the local Jordanian H9N2 isolate and the variation from what it has been reported in other countries of the region. Regional effort should be directed to start an eradication program of this disease because of its pathogenicity for chickens, wide distribution, and possible interference with surveillance for H5N1 serotype.  相似文献   

17.
Public pressure to reduce or eliminate antimicrobials as ingredients of feed for poultry and other agricultural animals is mounting, primarily due to the fear of multidrug-resistant bacteria in clinical infections in both animals and humans. Exploration of the occurrence of antibiotic resistance in the gut flora of wildlife avian flocks that presumptively do not receive antimicrobials will determine the rate of resistance in a na?ve population. Fecal samples collected from a healthy population of the yellow-headed blackbirds (YHB) (Xanthocephalus xanthocephalus) in North Dakota were cultured to determine what genera and species of gram-negative facultative anaerobic bacteria these wild birds carry in their intestinal flora and to evaluate the antimicrobial susceptibility profiles. Isolates of Escherichia coli were further characterized for the presence of putative virulence factors and for pathogenic potential using the chicken embryo lethality assay (ELA). The ELA was performed in chicken embryos with challenges at both 12 days and 16 days of incubation to determine whether the 16-day-old embryos were better able to fight the infection and subsequent disease and also to determine whether the ELA could distinguish between primary and secondary avian Escherichia coli pathogens. After screening 33 isolates from the 21 fecal samples, only two E. coli isolates were identified. The predominant genus and species of bacterium identified was Pantoea agglomerans. Collectively, 12 of the 33 isolates (36%) exhibited no resistance to any antimicrobial tested. However, several multidrug-resistant isolates of varying genera were identified. Among the antimicrobial resistances observed, the most common was to ampicillin (60%), followed by cephalothin (33%). Neither E. coli isolate belonged to serogroups that are notorious for causing major outbreaks of colibacillosis in poultry, and only one E. coli isolate retained resistance to any antibiotics; nevertheless, the ELA results indicate that at least one of these E. coli may be a primary pathogen of chickens. This study demonstrates that antibiotic resistance occurs in the gut flora of natural populations of YHB despite the absence of antibiotic pressure. In addition, these results indicate that YHB will harbor E. coli isolates that are potentially pathogenic in poultry. However, these E. coli isolates are not a significant reservoir for multiple antibiotic resistances nor are they widespread in the population of YHB surveyed in North Dakota.  相似文献   

18.
A total of 136 Shiga toxin-producing Escherichia coli (STEC) isolated during a longitudinal survey of three Australian dairy farms were examined to determine their virulence factors, serotype and genomic relationships. This study aimed to assess the potential of these STEC to cause disease in humans and to analyse the on-farm ecology of STEC. Virulence factors (stx, eae, ehxA) were used as determinants of potential to be enterohaemorrhagic E. coli (EHEC) and were examined using polymerase chain reaction (PCR). Among the cattle groups tested, calves, both before and during weaning, shed the most putative EHEC and were the main source of serotypes commonly associated with human disease. E. coli O157:H7 and E. coli O26:H11 represented 9.4 and 7.8% of cattle STEC isolates respectively, with other putative EHEC serotypes reported for the first time from cattle. Based on serotype and virulence factors, 20% of STEC were putative EHEC. Pulsed-field gel electrophoresis (PFGE) was used to compare the genomic profiles of STEC from dairy farms. Isolates common to cattle and the farm environment were identified. Multiple strains of STEC with high clonal turnover were detected in the faeces of cattle, and isolates appeared to be specific to individual farms. To fully assess the pre-slaughter EHEC risk factors on-farm, examination of STEC virulence is as important as determination of STEC prevalence.  相似文献   

19.
为了解四川省藏香猪源大肠埃希菌致病性、血清型及耐药性情况,从四川省藏香猪养殖场中无菌采集腹泻仔猪肝脏、肛拭子及粪便等组织病料253份中,分离得到155株大肠埃希菌。采用人工感染小鼠致病性试验、玻板凝集试验和KB药敏纸片法分别测定155株大肠埃希菌分离菌株的致病性、血清型及耐药性。结果显示,小鼠致病性试验表明155株分离菌中120株有致病性;玻板凝集试验表明120株致病性大肠埃希菌分离株属于14个血清型,以O111、O147、O109和O119为主要流行的优势血清型;耐药性试验表明120株致病性大肠埃希菌分离株对阿莫西林、氨苄西林、新霉素、磺胺间甲氧嘧啶4种药物耐药较严重,耐药率在94.2%~98.3%之间,对庆大霉素、氟苯尼考、多西环素等6种药物耐药率在44.2%~85.0%之间,对其他药物耐药率在15.0%~37.5%之间。说明该地区藏香猪源致病性大肠埃希菌血清型呈多样性分布,耐药性严重。  相似文献   

20.
The prevalence of verocytotoxin-producing Escherichia coli and Salmonella in Ontario broiler chickens was determined by culturing cloacal samples from 500 individual birds selected from 50 poultry farms. Resistance to antimicrobials was determined for each of the isolates. In addition, abattoir and farm-level management data were obtained to evaluate variables that may be considered risk factors for infection. The variables selected included: Percentage of birds condemned at slaughter, percentage of birds dead-on-arrival, bird weight, truck number, farm size, hatchery source, litter source and type, feed source, mortality levels, type of water drinker, water sanitization, down time, barn clean out and history of antibiotic treatment. None of the cloacal samples revealed the presence of verocytotoxin-producing E. coli, though 19/500 (3.8%) contained Salmonella organisms. Nine different Salmonella serotypes were isolated; the most common being S. hadar, S. heidelberg and S. mbandaka. Resistance to tetracycline and streptomycin was common among Salmonella (63%) and E. coli (25.2%) isolates. Resistance to two or more antimicrobials occurred in 420/500 (84%) of the E. coli isolates. No statistically significant associations between abattoir or farm-level management variables and the Salmonella-status of farms were demonstrated.  相似文献   

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