Susceptibility to antibiotics of Escherichia coli strains isolated from diarrhoeic and non-diarrhoeic livestock in Trinidad.

The sensitivity of strains of Escherichia coli isolated from calves, piglets, lambs and kids in Trinidad to seven antibiotics was determined. Two hundred and sixty-four (91.3%) of 289 strains isolated from diarrhoeic animals and 173 (87.4%) of 198 strains from non-diarrhoeic animals exhibited resistance to one or more antibiotics. The difference was not statistically significant (P > or = 0.05; X2). Regardless of health status, isolates from lambs were least resistant (75.0%) and those from piglets most resistant (96.7%) and the difference was significant (P < or = 0.001; X2). Strains of E. coli were most resistant to streptomycin (81.3%) and tetracycline (78.9%) and least resistant to chloramphenicol (4.3%) and gentamycin (4.7%). The predominant antibiotic resistance pattern for isolates from all sources was streptomycin-tetracycline (27.9%). It was concluded that the widespread prevalence of resistance to antibiotics reflects their misuse in the local environment.     

Prevalence and antimicrobial resistance of Salmonella spp. in pet mammals, reptiles, fish aquarium water, and birds in Trinidad

The prevalence of Salmonella spp. was determined in 970 animals comprising 423 pet birds, 485 fish aquaria water and 62 other pets (40 pet mammals, 14 reptiles, eight others - crustaceans, snail, stingray) from both pet shops and households throughout Trinidad. The serotypes of Salmonella spp. isolated were identified and the resistance to various antimicrobial agents was determined. Overall nine (0.9%) of 970 pet animals were positive for Salmonella spp. Six isolates of Salmonella spp. were recovered from all pet birds with two isolates of serotype Aberdeen and one isolate each of Thompson, Rubislaw, Panama and Newport. The prevalence of Salmonella spp. in birds was 0.9%. Four isolates of Salmonella spp. were recovered from fish aquaria water, serotypes included Panama (two isolates), Newport (one isolate) and Virchow (one isolate). Prevalence of Salmonella spp. from fish aquaria was 0.4%. No isolate of Salmonella spp. was detected in pet mammals sampled while two isolates were recovered from reptiles, S. Enteritidis and S. Montevideo. One isolate of Salmonella spp. was recovered from a stingray, serotype unknown. Antimicrobial resistance was present is all animal types. The highest prevalence of resistance was to streptomycin among isolates from birds (83.3%) and other pets (100.0%) while isolates from fish aquarium water exhibited comparatively high resistance to cephalothin (50.0%). It was concluded that the isolation of Salmonella spp. from apparently healthy birds, fish aquarium water and other pet animals may pose a health risk to their owners and contacts as all serotypes are known to be potentially pathogenic depending on the oral dosage of the organism and the immune status of those in contact. The high prevalence of resistance to antimicrobial agents among Salmonella isolates across pet species may pose chemotherapeutic consequences to their owners and contacts.     

Detection and characterization of Shiga toxin-producing Escherichia coli in captive non-domestic mammals

Shiga toxin producing-Escherichia coli (STEC) is an important emerging pathogen, and ruminants are recognized as their main natural reservoir. The aim of this work was to establish the frequency of STEC in non-domestic mammals of the Zoo and Botanical Garden of La Plata City, Argentina, and to pheno-genotypically characterize STEC isolates. By polymerase chain reaction (PCR), Shiga toxin (stx) gene sequences were detected in 50.8% of 65 fecal samples. Twenty-five STEC strains were isolated from 38.5% of the Zoo's animals. Ten species of order Cetartiodactyla and one species of order Rodentia were recognized as new STEC carriers. STEC strains belonged to 7 different serotypes including new serotypes O12:H25 and O13:H6. Serotype O146:H28, previously associated with human infections, represented 24% of STEC isolates. The most frequent Shiga toxin identified were type 1c and type 2c. Nineteen strains were positive for iha gene, 8 strains were positive for ehxA gene. Moreover, all strains were positive for lpfAO113 and negative for rfbO157, eae, saa, lpfAO157/OI-141, lpfAO157/OI-154, efa1, and toxB genes. Results obtained by XbaI-pulsed-field gel electrophoresis (XbaI-PFGE) confirmed the transmission of STEC strains among different animal species and suborders. In addition, we observed a potential association between STEC-harboring animal and factors such as belonging to order Cetartiodactyla, living in a pit, and belonging to a non-autochthonous species. This is the first work developed with zoological mammals and STEC in Argentina.     

鸭源大肠杆菌分离株药物敏感性测定

自永定肉鸭养殖场分离到17株大肠杆菌,对其进行了常用抗生素敏感性测定。结果显示所检测的25种抗生素中,无高敏药,中敏药物仅为阿米卡星、头孢类药物。由此表明鸭大肠杆菌分离菌株的耐药性在不断增强、耐药谱在拓宽。     

Escherichia coli strains isolated from diarrheic piglets in the Province of Quebec.

During 1972 to 1974, 112 Escherichia coli strains isolated from diarrheic piglets were recieved from different parts of the Province of Quebec, Canada. Fifty-six strains elicited a positive gut loop response in three week old piglets and were then considered as Moon's class 1 enteropathogens, while four of the 56 remaining strains reacted only in ten day old piglets and were classified as class 2 enteropathogens. Forty-eight strains produced both a heat-labile and a heat-stable enterotoxin, while 12 isolates which included the four class 2 enteropathogens produced only a heat-stable enterotoxin. Fifty-one enterotoxigenic strains could be serogrouped using OK antisera against E. coli strains commonly associated with colibacillosis in piglets. The most common serogroups encountered were O157: K "V17"; 88a,c, O149:K91; 88a.c. O157:K"V1c, O149:K91; 88a.c, O157:K"V17"; 88 a,c or a,b and O45:K"E5"; 88a,c. No significant difference was observed in the fermentation patterns, antibiotic susceptibility, colicin production, production of a filterable hemolysin and transferable tetracycline resistance between the enterotoxigenic and the nonenterotoxigenic strains.     

Characterization of Escherichia coli strains isolated from pigs with edema disease.

Escherichia coli strains belonging to serogroups O 138 and O 139 isolated from pigs with edema disease, were characterized with respect to the presence of genes encoding Shiga-like toxin I, Shiga-like toxin II and Shiga-like toxin IIv (SLT I, SLT II and SLT IIv). Genes coding for the heat-stable and heat-labile enterotoxins (ST I and LT I) were also detected. Plasmid profiling, restriction enzyme digestion of total DNA, and ribotyping were performed for further characterization of the strains. The oligonucleotide probes applied in this study appeared to be useful tools for detecting genes coding cytotoxins and enterotoxins. DNA from 12 of 16 strains hybridized with two SLT II probes, and DNA from two SLT IIv encoding strains also hybridized with the ST I probe. DNA from one SLT IIv negative strain hybridized with the LT I probe. The results from plasmid profiling, restriction enzyme digestion, and ribotyping were compared with serogrouping in attempts to distinguish between the different E. coli edema disease isolates. Fourteen different plasmid profiles were identified, and as restriction patterns barely did, and ribotyping patterns did not, reveal any information useful for differentiation of the strains beyond serogroup level, plasmid profiling seemed to be the most suitable method for discrimination between the edema disease strains investigated here.     

Occurrence and characterization of verocytotoxigenic Escherichia coli (VTEC) strains from dairy farms in Trinidad

A cross-sectional study was conducted to determine the prevalence and characteristics of verocytotoxigenic Escherichia coli (VTEC) on 25 dairy farms each located in Waller field and Carlsen field farming areas in Trinidad. On each selected farm, faecal samples were collected from milking cows, calves and humans; rectal swabs were obtained from pet farm dogs; bulk milk was sampled as well as effluent from the milking parlour. Escherichia coli was isolated from all sources on selective media using standard methods. Isolates of E. coli were subjected to slide agglutination test using E. coli O157 antiserum, vero cell cytotoxicity assay to detect verocytotoxin (VT) and heat labile toxin (LT) production, the polymerase chain reaction (PCR) to detect VT genes, and the dry spot test to screen for E. coli O157 and non-O157 strains. In addition, faecal samples from animal and human sources were tested for VT genes using PCR. Of a total of 933 E. coli isolates tested by the slide test, eight (0.9%) were positive for the O157 strain. The vero cell cytotoxicity assay detected VT-producing strains of E. coli in 16.6%, 14.6%, 3.2% and 7.1% of isolates from cows, calves, farm dogs and humans respectively (P < 0.05; chi(2)). For LT production, the highest frequency was detected amongst isolates of E. coli from calves (10.8%) and the lowest (0.0%) amongst isolates from humans and bulk milk (P < 0.05; chi(2)). Of the 61 VT-producing isolates by vero cell cytotoxicity assay tested by PCR, the VT, LT and eae genes were detected in 62.3%, 4.9% and 1.6% respectively (P < 0.05; chi(2)). Amongst the 45 E. coli isolates that were VT positive (vero cell) or VT-gene positive by PCR, 2.2%, 2.2%, 4.4% and 6.7% belonged to non-O157 strains O91, O111, O103 and O157, respectively, as determined by the Dry spot test. Detection of VTEC strains in milk and dairy animals poses a health risk to consumers of milk originating from these farms. In addition, the demonstration of VTEC strains in humans, VT gene in faecal samples and E. coli isolates as well as non-O157 VTEC strains of E. coli are being documented for the first time in the country.     

Virulence genes of Escherichia coli strains isolated from mastitic milk

Escherichia coli, a Gram-negative environmental pathogen associated with bovine mastitis was isolated from the milk of 34 symptomatic cows that had been diagnosed with clinical mastitis. Eighty isolates were obtained over a 17-month period and these isolates were screened by DNA amplification for the following E. coli virulence genes: cnf1, cnf2, eaeA, eagg, einv, ltx1, stx1, stx2 and vt2e. Thirty of the bacterial isolates, obtained from 23 different cows, had toxin genes identified in their DNA. The most common virulence gene detected was stx1, with a prevalence of 31%, followed by cnf2 (7.5%), vt2e (6.25%) and eaeA (4%). The possession of different virulence genes by the bacterial isolates had no discernable impact on the health status of the cows as there was no correlation between the potential for toxin production by the E. coli isolates and the systemic clinical condition of the respective infected cows.     

Occurrence of fimbriae and enterotoxins in Escherichia coli strains isolated from piglets in Poland.

1125 and 1146 E. coli strains isolated from suckling and weaned piglets with diarrhea, respectively, and 724 strains from healthy piglets were tested for the presence of fibriae and production of enterotoxins. The fimbriae were determined by hemagglutination and slide agglutination tests, enterotoxins—by the use of ileal loop test in piglets (LT and STb enterotoxins) and suckling mouse assay (STa enterotoxin). It was found that 72.8 and 53.0% strains, isolated from diseased suckling and weaned piglets, respectively, possessed specific fimbrial hemagglutinins, in most cases with K88 antigen. Additionally, 987P fimbriae were detected in 14.0 and 0.7% strains isolated from piglets with diarrhea. Only 5 strains (0.7%) recovered from healthy piglets had specific fimbriae, usually with undetermined antigenic structure. F1 fimbriae (called common or unspecific) were found in strains isolated both from diseased (15.2 and 16.3% strains, respectively) and healthy piglets (27.1% strains). It was noted that the strains isolated from suckling and weaned piglets with diarrhea in most cases were enterotoxigenic (90.5 and 69.1% strains, respectively) and most frequently produced heat-labile toxin LT alone or with STb. 18.5% of enterotoxigenic strains isolated from healthy piglets produced STa toxin.     

Virulence-associated factors of uropathogenic Escherichia coli strains isolated from pigs

Thirty one Escherichia coli strains isolated from pigs with urinary tract infections were investigated for presence of virulence factors and plasmid DNA profile. The most frequent virulence factors presented by these strains were mannose-resistant fimbriae, including P. fimbriae (54.8%) and aerobactin production (45.2%). The pap) operon, detected by PCR, was found in 54.8% of the strains, which is similar to its frequency in human strains. Other characteristics such as the presence of mannose-sensitive hemagglutinin (16.1%), indicative of type 1 pili, and production of hemolysin (25.8%), colicin (38.7%) and toxins (22.6% for LT and for VT) were less frequent. No strains were positive for STa production. Plasmid profiles were variable among isolates from either the same or different farms.     

Curli expression by Escherichia coli strains isolated from bovine mastitis

The aim of the study was to determine the expression of mannose-sensitive and mannose-resistant adhesins by agglutination of cattle, sheep, goat, rabbit, horse, and chicken red blood cell assay, and curli fimbriae by Congo red binding assay among 341 E. coli strains isolated from 51 milk samples of clinically recognized bovine mastitis. Curli fimbriae expression within biofilms created on an inert surface was also investigated. To determine whether curli fimbriae are expressed both in conditions optimal for their production and in conditions resembling the host organism, the study was conducted in anaerobic atmosphere at 37 degrees C, and at room temperature in aerobic atmosphere. The results demonstrated that although the E. coli isolates examined were deprived of mannose-sensitive and mannose-resistant adhesins they were able to produce curli fimbriae in both aerobic and anaerobic conditions at room and higher temperature, indicating that these adhesins may be involved in the pathogenesis of bovine mastitis.     

Characterization of shiga toxin-producing Escherichia coli strains isolated from calves in Poland

Fecal samples from 67 3–5-months-old calves with diarrhea were screened for the presence of shiga toxin-producing Escherichia coli (STEC). Several accessory virulence factors genes were also tested. Among 192 E.coli isolates tested, 15 (7.6%) were found to harbour the shiga toxin 1 or 2 (stx1 or stx2) genes. The stx2-carrying samples were further subtyped by PCR for the stx2c, stx2d, and stx2e toxin variants. It was shown that stx2-positive bacteria mainly possessed the stx2c shiga toxin type gene. The enterohemolysin (hlyA) and intimin (eae) genes were found in seven (46.7%) STEC strains whereas the cytotoxic necrotizin factor 1 and 2 or the P fimbrial genes were detected in two isolates only. This study confirmed that calves are a reservoir of STEC strains (with all pathogenicity genes) that may be virulent for humans.     

O-serovar distribution and antibiotic sensitivity of Pseudomonas aeruginosa strains from birds and reptiles

100 strains of Pseudomonas aeruginosa (P.a.) from birds and reptiles were compared by determination of their O-serovars and their resistance to chemotherapeutic agents. A great number of isolates (birds 17.4%, reptiles 29.6%) were serologically untypable using 17 O-antisera by slide-agglutination-technique. The prevalence of O-serovar 0:6 was found in birds (39%) and reptiles (18.5%), followed by bird-isolates 0:1 and 0:3 (each 13%) and reptile-isolates 0:16 (14.8%). The serological distribution was different among bird- and reptile-isolates and also among the human and animal strains. All strains were resistant to penicillin G and ampicillin, more than 90% to nitrofurantoin, sulfamethoxazole-trimethoprim, chloramphenicol and erythromycin. Resistance to tetracycline was found to be 87%, resistance to sulfonamide 81%, respectively. 32% of all isolates were resistant to streptomycin, 61% to kanamycin. All isolates were susceptible to genta- and neomycin. Also all isolates, except one reptile-strain, were susceptible to gyrase-blocker (Bay VP 2674). 2 isolates were resistant to polymyxin B.