Antimicrobial susceptibility, plasmid profiles and haemocin activities of Avibacterium paragallinarum strains

In this study, 18 Avibacterium paragallinarum isolates collected in Taiwan from 1990 to 2003 were serotyped and tested for resistance to antimicrobial agents. Serotyping revealed that 13 isolates were Page serovar A and 5 isolates were Page serovar C. More than 75% of the isolates were resistant to neomycin, streptomycin and erythromycin. The most common resistance pattern (15 isolates, 83.3%) was neomycin-streptomycin. Furthermore, 88.9% of the isolates were resistant to two or more antibiotics. About 72% of isolates contained plasmids (pYMH5 and/or pA14). Plasmid pYMH5 encoded functional streptomycin, sulfonamide, kanamycin and neomycin resistance genes and revealed significant homology to a broad host-range plasmid, pLS88. Plasmid pA14 encoded a putative MglA protein and RNase II, both of which might be associated with virulence. Furthermore, seven isolates showed haemocin activity. Plasmid pYMH5 is the first multidrug-resistance plasmid reported in A. paragallinarum and it may facilitate the spread of antibiotic-resistance genes between bacteria. The putative virulence plasmid pA14 and haemocin-like activity in A. paragallinarum indicate two possible mechanisms which might be responsible for the pathogenesis.     

In vitro antimicrobial sensitivity of isolates of Yersinia pseudotuberculosis from deer

The in vitro sensitivity of 34 isolates of Yersinia pseudotuberculosis from red deer (Cervus elaphus) was determined by disc diffusion tests using 15 antimicrobial drugs. All isolates were sensitive to ampicillin, chloramphenicol, gentamycin, kanamycin, neomycin, “septrin” (combination of trimethoprim and sulphamethoxazole) streptomycin and tetracycline. Twenty isolates were sensitive to polymyxin B and 14 were resistant. All isolates were resistant to bacitracin, erythromycin, novobiocin and moderately resistant to furazolidone. The responses using sulphafurazole or trimethoprim were difficult to interpret accurately but most isolates were classified as sensitive.     

The resistance of antimicrobial agents in Salmonella from veterinary sources in Australia from 1975 to 1982

SUMMARY A survey of antibiotic resistance in 1,287 strains of Salmonella from bovine, porcine and avian sources in Australia was carried out from 1975 to 1982. Isolates were tested against ampicillin, chloramphenicol, furazolidone, neomycin, streptomycin and tetracycline. Resistance was found to streptomycin in 286 isolates and to tetracycline in 282 isolates. Resistance to other antimicrobials was low and was unrelated to source. One hundred and seventy-three isolates showed multiple resistance to 2 or more antimicrobial agents with resistance to streptomycin and tetracycline being the most common. The overall level of resistance did not change over the period examined.     

Characterisation of isolates of Haemophilus paragallinarum from Indonesia

OBJECTIVE: To characterise 18 isolates of Haemophilus paragallinarum isolated from chickens in Indonesia. PROCEDURE: The isolates were identified to species level by traditional phenotypic methods. Six of the isolates were also identified by a species-specific polymerase chain reaction. Fourteen of the isolates were examined for resistance to a panel of seven antimicrobial agents using a disc diffusion method. All 18 isolates were serotyped according to the Page scheme using reference antisera in a haemagglutination inhibition test. RESULTS: Four of the 18 isolates were obtained from indigenous (kampung) chickens, with the remainder being from typical intensive poultry production systems. The 18 isolates were obtained from 11 outbreaks that showed the typical clinical signs of infectious coryza and 11 of the isolates were obtained from chickens that had been vaccinated with infectious coryza vaccines. All 18 isolates were confirmed as H paragallinarum by biochemical testing and six isolates were also identified as H paragallinarum by the polymerase chain reaction test. Eleven isolates were resistant to erythromycin and streptomycin, 10 to neomycin, eight to oxytetracycline, five isolates to doxycycline, three to sulphamethoxazoltrimethoprim but only one to ampicillin. Seven isolates were Page serovar A, four were Page serovar B and seven were Page serovar C. CONCLUSION: The presence of all three Page serovars (A, B and C) has been confirmed for the first time in Indonesian chickens. As the majority of the infectious coryza vaccines in use in Indonesia contain only serovar A and C, the presence of serovar B in chickens indicates that the protection by these bivalent vaccines would be reduced. The use of trivalent infectious coryza vaccines that contain serovars A, B and C is recommended for use in Indonesia.     

Antimicrobial resistance of Salmonella isolated from finishing swine and the environment of 60 Alberta swine farms

The study objective was to describe and evaluate antimicrobial resistance profiles in Salmonella isolated from Alberta swine finishing farms. Salmonella isolates (n = 322) were obtained from 192 fecal and 84 environmental samples of the 60 Salmonella-positive swine finishing farms. Isolates were classified susceptible, intermediate or resistant based on NCCLS guidelines. More than half of the isolates (53.4%) were susceptible to all of the 18 antimicrobials in the testing panel. No resistance was observed to amikacin, amoxicillin/clavulanic acid, cefoxitin, ceftiofur, ceftriaxone, cephalothin, ciprofloxacin, imipenem or nalidixic acid. Less than 1% of isolates were resistant to apramycin, gentamicin and trimethoprim/sulfamethoxazole. Higher frequencies of resistance were observed for chloramphenicol (4.7%), ampicillin (7.8%), kanamycin (11.8%), sulfamethoxazole (21.1%), streptomycin (25.5%) and tetracycline (38.8%). Eleven Salmonella serovars had isolates with resistance to > or =3 antimicrobials. The most frequently resistant serovar was Salmonella Derby, with 27 (38.0%) isolates resistant to > or =3 antimicrobials, including resistance to five and six antimicrobials. An absence of resistance to cephalosporins and fluoroquniolones and a low proportion of isolates resistant to amikacin, amoxicillin/clavulanic acid, apramycin, gentamicin and trimethoprim/sulfamethoxazole are encouraging findings from public health and animal health perspectives. Frequent resistance observed for ampicillin, kanamycin, sulfamethoxazole, streptomycin and tetracycline, antimicrobials commonly used in veterinary medicine for decades, indicates an urgent need to utilize these antimicrobials more prudently if their benefits are to be preserved.     

Antibiotic resistance among indicator bacteria isolated from healthy pigs in New Zealand

AIM: To determine the resistance to antibiotics among the indictor bacteria, Escherichia coli and Enterococcus spp, isolated from the faeces of healthy pigs on three conventional pig farms and one organic farm in the North Island of New Zealand. METHODS: Faecal samples, collected at intervals between March and October 2001, were plated onto MacConkey agar and Slanetz-Bartley agar and examined after 1-3 days incubation for colonies resembling E. coli and Enterococcus spp, respectively. Typical colonies were subcultured for further identification and storage. The isolates were tested for antibiotic resistance, using disc diffusion, to ampicillin, gentamicin, streptomycin, and tetracycline. Escherichia coli isolates were also tested for resistance to ciprofloxacin, cotrimoxazole and neomycin. Enterococcus spp isolates were also tested for resistance to vancomycin, erythromycin and virginiamycin. RESULTS: A total of 296 E. coli and 273 Enterococcus spp isolates were obtained from the three conventional farms, and 79 E. coli and 80 Enterococcus spp isolates were obtained from the organic farm. All the E. coli isolates from both the conventional and organic pig farms were susceptible to ciprofloxacin, and all the Enterococcus spp isolates were susceptible to ampicillin, gentamicin and vancomycin. Isolates of E. coli from conventional pig farms were resistant to gentamicin (0.7%), neomycin (0.7%), ampicillin (2.7%), cotrimoxazole (11%), streptomycin (25%) and tetracycline (60%). Enterococcus spp isolates from the same farms were resistant to erythromycin (68%), tetracycline (66%), streptomycin (54%) and virginiamycin (49%). By contrast, for the organic pig farm 相似文献   

Antimicrobial drug susceptibility of Staphylococcus intermedius clinical isolates from canine pyoderma

A total of 50 Staphylococcus intermedius strains isolated in France from canine pyodermas in 2002 were investigated for their susceptibility to various antimicrobial drugs. Antimicrobial susceptibility was assessed using a 2-fold serial dilution method in Mueller-Hinton agar, and the minimal inhibitory concentrations (MICs) were determined. About 62% of the 50 strains tested were producers of beta-lactamase and categorized as penicillin-resistant. About 26% demonstrated resistance to sulphonamides, 46% to oxytetracycline, 30% to chloramphenicol, 28% to streptomycin, kanamycin, neomycin or erythromycin, 22% to clindamycin, 6% to doxycycline, 2% to gentamicin, enrofloxacin, marbofloxacin or pradofloxacin. Acquired resistance was not observed to a clavulanic acid-amoxicillin combination, oxacillin, cephalosporins (cephalexin, ceftiofur and cefquinome), trimethoprim, a sulphamethoxazole-trimethoprim combination and florfenicol. About 42% were simultaneously resistant to three or more antimicrobial classes (multiresistance). All isolates with acquired resistance to erythromycin were also resistant to streptomycin and neomycin/kanamycin. About 22% of isolates exhibited cross-resistance between erythromycin and clindamycin and all clindamycin-resistant isolates also exhibited resistance to erythromycin. Resistance to penicillin, oxytetracycline and chloramphenicol was also positively associated with resistance to erythromycin and streptomycin.     

Serovars of Salmonella isolated from Danish turkeys between 1995 and 2000 and their antimicrobial resistance

The prevalence of Salmonella serovars and their antimicrobial resistance patterns were investigated among Danish turkeys between 1995 and 2000, by sampling the flocks approximately 14 days before they were slaughtered. Within the flocks, the prevalence of salmonella varied from 7.1 per cent to 25 per cent, and 24 different serovars were detected. The five most prevalent, which accounted for 58.5 per cent of the isolates were Salmonella Heidelberg (16.2 per cent of the isolates), Salmonella Agona (15.8 per cent), Salmonella Derby (12.4 per cent), Salmonella Muenster (7.3 per cent) and Salmonella Anatum (6.8 per cent). In addition, a few rough isolates and isolates belonging to the antigenically incomplete formulae 6,7:-:- and 4,12:b:- were found. The level of antimicrobial resistance was low; the highest resistance was recorded to ampicillin (13.7 per cent) and streptomycin (9.0 per cent) followed by tetracycline (8.5 per cent), sulphonamides (7.7 per cent) and spectinomycin (4.7 per cent). Resistance to quinolones was very low: four isolates were resistant to nalidixic acid, and only one was resistant to enrofloxacin. No resistance was recorded to colistin, apramycin, ceftiofur, florfenicol, or amoxycillin with clavulanic acid. Only 24 isolates were resistant to two or more compounds in various combinations of up to six compounds; one Salmonella Havana isolate was resistant to six compounds. Six isolates were serovar Typhimurium, but none of them belonged to phage type DT104.     

High prevalence of multiple resistance to antibiotics in Salmonella serovars isolated from a poultry slaughterhouse in Spain

Salmonellosis is a major foodborne infection in Spain, and strains that are resistant to a great variety of antibiotics have become a major public health concern. The aim of this study was to determine the level of antibiotic resistance in 133 Salmonella isolates obtained from a poultry slaughterhouse in Zaragoza (NE Spain). Antimicrobial resistance testing was performed by disk diffusion method using 19 antibiotics. Results were interpreted following the NCCLS criteria. Overall, the highest percentage of resistance was found to the following antimicrobial agents: sulfadiazine (96.2%), neomycin (53.4%), tetracycline (21.8%), and streptomycin (11.3%). All isolates were found to be resistant to one or more of the antibiotics tested. Multiple resistance was observed in 87 strains (65.4%). We found 23 different patterns of resistance in Salmonella Enteritidis. Resistance to sulfadiazine was the most common single resistance. The most frequent patterns of multiresistant strains were neomycin+sulfadiazine and neomycin+tetracycline+sulfadiazine. S. 4,5,12:b: showed the highest percentages of resistance to the tested drugs, with five different resistance patterns found. Ampicillin+chloramphenicol+streptomycin+sulphonamides+tetracycline (ACSSuT) resistance pattern, commonly associated with S. Typhimurium DT 104, was not detected in strains of the same phage type from broilers. The appearance of substantial multiresistance in foodborne Salmonella isolates suggests the need for more prudent use of antibiotics by farmers, veterinarians, and physicians.     

The resistance to chemotherapeutic agents of Escherichia coli from domestic dogs and cats

The prevalence of antibiotic resistant Escherichia coli in the rectal flora of 168 healthy dogs and 93 cats in the Brisbane area was investigated. Rectal swabs were plated on MacConkey agar with and without antibiotics, and 690 isolates confirmed as faecal E. coli were tested for resistance to tetracycline, streptomycin, chloramphenicol, ampicillin, neomycin, furazolidone and sulphanilamide. Resistant isolates were obtained from 101 (60%) of the dogs and 24 (26%) of the cats sampled. A high percentage of the isolates was resistant to tetracycline, streptomycin, ampicillin and sulphanilamide. Multiple resistance to 3 or more of the drugs was exhibited by the majority of isolates and a total of 31 different multiple resistance patterns was demonstrated. Of the 50 strains tested for transfer of resistance, 30 (60%) transferred some or all of their resistance determinants to an E. coli K12F - recipient.     

Prevalence and in-vitro antimicrobial sensitivity of Bordetella bronchiseptica in the nasal cavity of pigs

The prevalence of Bordetella bronchiseptica in the nasal cavity of pigs and the in-vitro sensitivity of isolates to a variety of antimicrobial agents was investigated. B.Bronchiseptica was recovered from 372 nasal swabs collected from 1000 (37.2%) pigs slaughtered at 20-30 weeks old at an abattoir. The swabs were collected from groups of 5-206 pigs derived from 25 herds. All isolates tested against bacitracin, clindamycin, furazolidone, penicillin, spectinomycin, streptomycin and tylosin were found to be resistant. Of the 372 isolates tested against ampicillin and erythromycin 22 (6%) were sensitive to the former and 365 (98%) were moderately sensitive to the latter, the remainder were resistant. All isolates tested against neomycin and tetracycline were sensitive and with few exceptions, (2%), they were also sensitive to chloramphenicol. Overall, 259 of the 372 (70%) isolates were sensitive to sulphonamides, identical results being obtained with sulphadiazine, sulphafurazole and a trimethoprim-sulphamethoxazole combination. An association between in-vitro resistance to sulphanomides and extensive use of this group of drugs was demonstrated on three of eight farms investigated.     

Antimicrobial resistance pattern of Salmonella serotypes isolated from food items and personnel in Addis Ababa, Ethiopia

Antimicrobial susceptibility test of 98 isolates of Salmonella was assayed from September 2003 to February 2004 using the guidelines of the National Committee for Clinical Laboratory Standards (NCCLS).The result revealed that 32.7% of Salmonella isolates were resistant to one or more of the 24 antimicrobials tested. Generally resistance for 13 different antimicrobial drugs was recognized. The most common resistance was to streptomycin (24/32, 75%), ampicillin (19/32, 59.4%), tetracycline (15/32, 46.9%), spectinomycin (13/32, 40.6%) and sulfisoxazole (13/32, 40.6%). All the three Salmonella Kentucky isolates showed resistance to at least 8 antimicrobials. Out of the 12 Salmonella Braenderup isolates, 10 (83.3%) showed multidrug resistance to ampicillin, spectinomycin, streptomycin, sulfisoxazole, sulfamethoxazole/trimethoprim, amoxicillin/clavulanic acid and trimethoprim. Among the 8 S. Hadar isolates 7 (86.5%) showed antimicrobial resistance. All the 6 S. Dublin isolates were resistant to carbadox (100%). All the 6 S. Haifa isolates were resistant for at least ampicillin, streptomycin and tetracycline. Up to ten different antimicrobial resistances pattern was observed. Multiple antimicrobial drug resistance was observed in 23 Salmonella isolates (23.5%). The level of antimicrobial resistance was significantly higher for isolates from chicken carcass (18/29, 62.1%) and pork isolates (5/22, 22.7%) (p = 0.003). The findings of the present study ascertain that significant proportion Salmonella isolates have developed resistance for routinely prescribed antimicrobial drugs and poses considerable health hazards to the consumers unless prudent control measures are instituted.     

THE RESISTANCE TO ANTIMICROBIAL AGENTS OF STAPHYLOCOCCUS AUREUS ISOLATED FROM THE BOVINE UDDER

SUMMARY Isolates of Staphylococcus aureus (total 1657) from bovine mastitis were collected from 13 laboratories throughout Australia from 1974 to 1979. They were tested for resistance to antimicrobial agents using an agar dilution method. Resistance shown was mainly to penicillin and streptomycin. Occasional strains were resistant to neomycin, lincomycin, erythromycin, tetracycline, chloramphenicol and furazolidone but multiple resistance was rare. No strain showed resistance to methicillin. Resistance to penicillin declined from 35% in 1974–75 to 7.1% in 1979. Most strains (1395) were retested to allow induction of penicillinase: 62% produced the enzyme.     

A 10-year survey of antimicrobial susceptibility of streptococcus suis isolates from swine in Japan

A number of 689 Streptococcus suis isolates collected nationwide from diseased and healthy pigs from 1987 to 1996 were surveyed for antibiotic susceptibilities to 11 drugs. No isolates resistant to amoxicillin, chloramphenicol, and sulfamethoxazole/trimethoprim were found. Isolates were highly susceptible to penicillins (penicillin G, ampicillin, and amoxicillin) except cloxacillin. They were not susceptible to tetracycline, streptomycin, and kanamaycin (MIC90 50 microg/ml, > or = 100 microg/ml, and > or = 100 microg/ml, respectively). Multiple-resistant isolates (> or = 3 antimicrobial agents) were found in 20.3% of all isolates tested.     

Characterization of Escherichia coli isolated from cases of avian colibacillosis.

Forty-four western Canadian isolates of Escherichia coli associated with colibacillosis of turkeys and chickens were examined for serotype, antibiotic resistance, and production of aerobactin. The isolates belonged to fourteen O serogroups, with 39% of the strains being non-typeable. A high frequency of resistance to tetracycline, kanamycin, neomycin, cephalothin, streptomycin and erythromycin was observed. Most isolates produced aerobactin. Ten E. coli belonging to serogroups O1, O2 and O78 were also examined for pili production, hemagglutination, serum sensitivity, production of iron-regulated outer membrane proteins (IROMPS), and virulence. All isolates examined produced pili, exhibited mannose-sensitive hemagglutination of avian red blood cells and produced IROMPS under iron-restricted growth conditions. The five isolates of serogroup O1 and O2 were resistant to killing by turkey serum and were highly virulent. Only two of the five isolates of serogroup O78 were serum resistant. No correlation between serum resistance and virulence was observed in serogroup O78.     

Occurrence of multidrug resistant Salmonella in antimicrobial-free (ABF) swine production systems

This cross-sectional study was conducted to determine the prevalence and antimicrobial resistance of Salmonella species in swine reared in the intensive (indoor) and extensive (outdoor) ABF production systems at farm and slaughter in North Carolina, U.S.A. We sampled a total of 279 pigs at farm (extensive 107; intensive 172) and collected 274 carcass swabs (extensive 124; intensive 150) at slaughter. Salmonella species were tested for their susceptibility against 12 antimicrobial agents using the Kirby-Bauer disk diffusion method. Serogrouping was done using polyvalent and group specific antisera. A total of 400 salmonellae were isolated in this study with a significantly higher Salmonella prevalence from the intensive (30%) than the extensive farms (0.9%) (P<0.001). At slaughter, significantly higher Salmonella was isolated at the pre- and post-evisceration stages from extensively (29% pre-evisceration and 33.3% post-evisceration) than the intensively (2% pre-evisceration and 6% post-evisceration) reared swine (P<0.001). The isolates were clustered in six serogroups including B, C, E1, E4, G and R. Highest frequency of antimicrobial resistance was observed against tetracycline (78.5%) and streptomycin (31.5%). A total of 13 antimicrobial resistance patterns were observed including the pentaresistant strains with ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline resistance pattern observed only among isolates from the intensive farms (n=28) and all were serotype Salmonella typhimurium var. Copenhagen. In conclusion, this study shows that multidrug resistant Salmonella are prevalent in ABF production systems despite the absence of antimicrobial selection pressure. In addition, it also highlights the possible role played by slaughterhouse and other environmental factors in the contamination and dissemination of antimicrobial resistant Salmonella in ABF production systems.     

Antibiogram of staphylococcal strains isolated from milk and milk-products

A study of the resistance patterns of 248 staphylococcal isolates from milk and milk products to eight antimicrobial agents using the disc method showed that 80 (32.3%) were resistant to sulphafurazole, 75 (30.2%) to penicillin G, 63 (25.4%) to ampicillin, 23 (9.3%) to cloxacillin, 19 (7.7%) to tetracycline, 17 (6.9%) to streptomycin, 14 (5.6%) to erythromycin and 12 (4.8%) to chloramphenicol. One hundred and sixteen (46.8%) of the 248 staphylococcal isolates were sensitive to all the agents tested. A significant percentage (P less than 0.05) of the isolates from raw milk were resistant to erythromycin, sulphafurazole, cloxacillin, penicillin G and streptomycin compared to isolates from fermented milk. The minimum inhibitory concentrations (MIC) as determined by the tube method for isolates resistant by the disc method, were greater than or equal to 16 micrograms for ampicillin in 5 (11.9%) isolates; greater than or equal to 40 micrograms for cloxacillin, 9 (36.0%) and greater than or equal to 12 international units for penicillin G amongst 12 (22.2%) isolates. MIC values of greater than or equal to 40 micrograms were recorded for 9 (90.0%), 9 (69.2%), 8 (73.7%) and 7 (70.0%) isolates to chloramphenicol, streptomycin, erythromycin and tetracycline respectively. The relatively high level of resistance to antimicrobial agents is a reflection of misuse or abuse of these agents in the environment.     

In vitro susceptibility of Escherichia coli strains isolated from diarrhoeic lambs and goat kids to 14 antimicrobial agents

The in vitro activities of 14 anti-microbial agents were determined against 92 strains of E. coli isolated from lambs (60 strains) and kids (32 strains) affected by neonatal diarrhoea. The overall percentage of resistant strains to streptomycin, sulphadimethoxine and tetracycline was very high (above 70%). A high level of resistance (from 30% to 50%) to ampicillin, kanamycin, neomycin and chloramphenicol was also detected. The E. coli strains were highly susceptible to cephalosporins, polymyxin and quinolones. Most of the strains showed multiresistance: 77.2% of isolates were resistant to at least two antibiotics, 55.4% were resistant to at least four antibiotics and 33.7% were resistant to at least six antibiotics. A total of 34 antibiotypes could be distinguished.     

Antimicrobial resistance of fecal coliforms from pigs in a herd not exposed to antimicrobial agents for 126 months

Patterns of antimicrobial resistance were determined for lactose-fermenting fecal coliforms obtained during a 20-month period from pigs in a herd without exposure to antimicrobial drugs for 126 months. Mean percent resistance to cephalothin, chloramphenicol, kanamycin, naladixic acid, streptomycin and tetracycline was lower (P less than 0.01) for isolates obtained during the 20-month period (Group 2) than for isolates obtained during the first 13 months (Group 1) after the withdrawal of antibiotics. Mean tetracycline resistance was 40.5% for Group 2 isolates. Approximately 44% of the Group 2 isolates were resistant to the 10 antimicrobial agents compared with 74.9% for the Group 1 isolates (P less than 0.01). Multiple resistance was lower (P less than 0.01) in the Group 2 isolates than in the Group 1 isolates. Four resistance patterns (tetracycline, tetracycline-streptomycin, tetracycline-sulfisoxazole, tetracycline-streptomycin-sulfisoxazole) accounted for 74% of the resistant isolates.     

Molecular and virulence characteristics of multi-drug resistant Salmonella Enteritidis strains isolated from poultry

Forty-six Salmonella enterica subspecies enterica serovar Enteritidis (S. Enteritidis) strains were isolated from chicken meat, faeces, and eggshells collected from hatcheries throughout Korea. The strains were examined for the presence of antimicrobial resistance and virulence genes. All 46 isolates were resistant to at least one of 21 antibiotics used in this study, 30 (65.2%) were resistant to three or more antimicrobials, and a single remarkable isolate was resistant to 15 antimicrobials. The isolates were primarily resistant to penicillins, sulfisoxazole, streptomycin, tetracycline and quinolones.The high rate of resistance in S. Enteritidis strains, sometimes to multiple drugs, may complicate future options for treating human infections. Nineteen of the 21 penicillin resistant isolates carried the bla_TEM gene, while one strain, resistant both to penicillins and ceftriaxone, carried the bla_CTX-M gene. Thirty-seven of the 45 sulfisoxazole resistant isolates carried sul2, and 23/24 streptomycin resistant isolates carried both strA and strB. All 10 tetracycline resistant isolates carried the tet(A) gene. Most isolates harboured both SPI-1 and SPI-2-associated genes, and the spv operon, which are known to be associated with human infections. The presence of these genes suggests that these strains could give rise to public health problems if dispersed in the general human population.