Variability in antimicrobial resistance among Salmonella enterica strains from fattening pigs and sows

The aim of this study was to determine the prevalence of antibiotic resistance and different resistance patterns for Salmonella isolates collected from Belgian sows and fattening pigs at different ages and at slaughter. The most frequently isolated serotypes were S. Typhimurium (42.3%), S. Derby (25.1%), S. Goldcoast (7.3%), and S. Infantis (4.8%). All 901 isolates were submitted to antimicrobial susceptibility testing for 14 compounds using the disc agar diffusion test. The highest percentage of resistance was found to oxytetracycline (34.2%), streptomycin (32.5%), sulfamethizole (27.6%), and ampicillin (24.9%). Three of the isolates showed resistance to cephalosporins and none to second-generation fluoroquinolones. Multiresistance (resistance to > or =2 antimicrobials) was observed in 33.2% of the strains. Differences in resistance patterns were observed between and within serotypes as well as genotypes. A significant lower proportion (p < 0.01) of resistant strains was recovered in fecal samples from sows (23/56) than from fattening pigs during the weaning (30/30), growing (79/85), and finishing periods (45/52). The proportion of resistant strains recovered from fecal samples taken at the herd (154/167) was higher than in the samples collected at the slaughterhouse (75/140). When designing antimicrobial resistance surveillance programs for Salmonella in pigs, it is important to take multiple samples within each herd from both sows and fattening pigs at different time points.     

Antimicrobial resistance and serotype distribution among Salmonella spp. in pigs and poultry in Iceland, 2001-2005

Little information is available on antimicrobial resistance of bacteria isolated from animals and animal products in Iceland. The objective of this study was to analyze serotype distribution and antimicrobial resistance patterns of Salmonella spp. isolated from healthy chickens and pigs in Iceland during 2001-2005. A total of 163 Salmonella strains, isolated in the national Salmonella surveillance program, were available for study. Isolates were tested for antimicrobial susceptibility using a microbroth dilution method (VetMIC) and resistant strains were compared using pulsed-field gel electrophoresis (PFGE) and phage typing. The most commonly isolated serotypes were Salmonella Infantis (61%) and S. Typhimurium (33%); other serotypes were less prevalent. The overall prevalence of resistance was 13.6% in chickens and 12.8% in pigs. Twenty one isolates (12.8%) were resistant to one or more antimicrobials, 19 S. Typhimurium strains, one S. Infantis strain, and one S. Worthington strain. Sixteen out of the 19 resistant S. Typhimurium strains were multiresistant (to > or =3 antimicrobial agents), and, of these, 15 had identical or closely related PFGE patterns (previously phage typed as DT104). The prevalence of antimicrobial resistance in Salmonella spp. in pigs and poultry in Iceland is low; however, we found a multiresistant S. Typhimurium clone that causes concern. Continuous resistance surveillance is important, and further research on the source of resistant clones and possible transmission to humans is needed.     

Antibacterial activity of black tea (Camelia sinensis) extract against Salmonella serotypes causing enteric fever

Alcoholic extract of black tea (Camelia sinensis) was assayed for its antibacterial activity against Salmonella serotypes causing enteric fever viz., Salmonella typhi and Salmonella paratyphi A. While all strains of S. paratyphi A tested were found sensitive, only 42.19% of S. typhi strains were inhibited by this extract. Further minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of black tea extract against S. paratyphi A was less compared with that against S. typhi.     

Development and evaluation of an experimental vaccination program using a live avirulent Salmonella typhimurium strain to protect immunized chickens against challenge with homologous and heterologous Salmonella serotypes.

A stable live avirulent, genetically modified delta cya delta crp Salmonella typhimurium vaccine strain, chi 3985, was used in several vaccination strategies to evaluate its use in the control of Salmonella infection in chickens. Oral vaccination of chickens at 1 and at 14 days of age with 10(8) CFU of chi 3985 protected against invasion of spleen, ovary, and bursa of Fabricius and colonization of the ileum and cecum in chickens challenged with 10(6) CFU of virulent homologous Salmonella strains from group B. Chickens challenged with heterologous Salmonella strains from groups C, D, and E were protected against visceral invasion of spleen and ovary, while invasion of the bursa of Fabricius and colonization of ileum and cecum was reduced in vaccinated chickens. Oral vaccination at 2 and at 4 weeks of age induced an excellent protection against challenge with virulent group B Salmonella serotypes and very good protection against challenge with group D or E Salmonella serotypes, while protection against challenge with group C Salmonella serotypes was marginal but significant. Vaccination at 2 and at 4 weeks of age also protected vaccinated chickens against challenge with 10(8) CFU of highly invasive S. typhimurium or S. enteritidis strains. The protection of chickens vaccinated with chi 3985 against challenge with homologous and heterologous Salmonella serotypes is outstanding, and the complete protection against ovarian invasion in chickens challenged with 10(8) CFU of highly invasive S. typhimurium or S. enteritidis strains suggests that vaccination of chickens with chi 3985 can complement the present hygiene- and sanitation-based Salmonella control measures. This paper reports a breakthrough in the use of live avirulent vaccine to control Salmonella carriers in chickens.     

Antimicrobial resistance of Salmonella serotypes isolated from slaughter-age pigs and environmental samples

The aim of this study was to determine the antimicrobial resistance patterns of Salmonella strains isolated from slaughter-age pigs and environmental samples collected at modern swine raising facilities in Brazil. Seventeen isolates of six serotypes of Salmonella enterica subsp. enterica were isolated out of 1,026 collected samples: Salmonella Typhimurium (1), Salmonella Agona (5), Salmonella Sandiego (5), Salmonella Rissen (1), Salmonella Senftenberg (4), and Salmonella Javiana (1). Resistance patterns were determined to extended-spectrum penicillin (ampicillin), broad-spectrum cephalosporins (cefotaxime and ceftriaxone), aminoglycosides (streptomycin, neomycin, gentamicin, amikacin, and tobramycin), narrow-spectrum quinolone (nalidixic acid), broad-spectrum quinolone (ciprofloxacin and norfloxacin), tetracycline, trimethoprim, and chloramphenicol. Antimicrobial resistance patterns varied among serotypes, but isolates from a single serotype consistently showed the same resistance profile. All isolates were resistant to tetracycline, streptomycin, and nalidixic acid. One isolate, Salmonella Rissen, was also resistant to cefotaxime and tobramycin. All serotypes were susceptible to ceftriaxone, norfloxacin, ciprofloxacin, ampicillin, gentamicin, and chloramphenicol. The high resistance to tetracycline and streptomycin may be linked to their common use as therapeutic drugs on the tested farms. No relation was seen between nalidixic acid and fluoroquinolone resistance.     

Lack of the alpha-1,2-linked N-acetyl-D-glucosamine epitope in the outer core structures of lipopolysaccharides from certain O serogroups and subspecies of Salmonella enterica.

A total of 176 strains of Salmonella enterica representing 116 serotypes were tested for the presence of the T6 epitope of the alpha-1,2-linked N-acetyl-D-glucosamine residue by reaction with a murine monoclonal antibody T6 specific for this structure in the Salmonella Ra core lipopolysaccharide (LPS). All 20 serotypes (70 strains) belonging to serogroups A to E were positive for the T6 epitope while 29% of the 96 serotypes (106 strains) belonging to O serogroups F to 67 were negative; 12 serotypes (12 strains) of subspecies IIIb Salmonella were positive for the T6 epitope, but 10 serotypes (11 strains) of subspecies IIIa Salmonella were found to lack this epitope. In T6-positive strains, the epitope was accessible to antibody binding in both the unsubstituted free rough core LPS and in the rough core LPS substituted with a few repeating units of O side chains. The presence or absence of the T6 epitope in Salmonella strains was not affected by culture conditions, the source of the isolate, the age of the culture or the presence of fimbriae antigens.     

Clonal nature of Salmonella typhi and its genetic relatedness to other salmonellae as shown by multilocus enzyme electrophoresis, and proposal of Salmonella bongori comb. nov

Crude cell extracts of 26 isolates of Salmonella serotype typhi (S. typhi) and 48 other Salmonella isolates representing 28 serotypes and seven DNA hybridization subgroups were analyzed for electrophoretic variants of 24 metabolic enzymes by starch gel electrophoresis. All strains of S. typhi had identical isoenzyme patterns, indicating that they were a single clone. All of the enzymes detected in the remaining strains were polymorphic, and the degree of genetic variation was quite high. The average number of alleles per enzyme locus was 4.7, and the mean genetic diversity per locus was 0.556. Thirty-two distinct allele profiles, or electrophoretic types (ETs), were found in these 48 strains of Salmonella serotypes other than S. typhi. Analysis of the genetic relationships of the ETs to each other showed that, with one exception, the ETs formed subgroups that were consistent with the subgroupings based on DNA hybridization studies. ET profiles were not always linked to specific serologic patterns. These data show that multilocus enzyme electrophoresis has a potential application in epidemiologic and taxonomic studies of salmonellae, although it is not differential for S. typhi. We also propose a new species, Salmonella bongori comb. nov., a new combination base on the elevation of Salmonella choleraesuis subsp. bongori to the level of species.     

Correlation between the presence of sequences homologous to the vir region of Salmonella dublin plasmid pSDL2 and the virulence of twenty-two Salmonella serotypes in mice.

Large plasmids encoding important virulence properties have been found in several Salmonella serotypes. We have studied the relationship between the presence of a highly conserved 4-kilobase (kb) EcoRI fragment from the plasmid virulence region and pathogenicity for mice of 53 isolates representing 22 serotypes of Salmonella. Only strains possessing the homologous 4-kb region were virulent for mice. In addition, we transferred the virulence plasmid from S. dublin into nine different serotypes, including S. typhi and S. paratyphi A, that lack a native virulence plasmid. Only S. heidelberg and S. newport were rendered mouse virulent by the introduction of the S. dublin plasmid. This study demonstrates that plasmid-mediated virulence sequences are required for Salmonella virulence in mice, but many strains, including the agents of human typhoid fever, also lack chromosomal genes necessary to produce lethal systemic disease in mice. Since all the major Salmonella strains that are host-adapted to animals carry virulence plasmids, it appears that these plasmids are important in mediating systemic infection in animals and may contribute to septicemic, nontyphoid salmonellosis in humans.     

佛山市食源性和人源沙门氏菌血清型分布与耐药性研究

目的了解佛山市食源性和人源沙门氏菌的血清型分布和耐药性关系。为今后的防制工作及l临床合理用药提供参考。方法采用国家标准检测方法进行沙门氏菌检验,纸片扩散法进行抗微生物药物敏感性试验。结果48株沙门氏菌分离出6个群别17种血清型,其中23株食源性沙门氏菌分离出6个群别13种血清型,25株人源沙门氏菌分离出5个群别12种血清型,2个来源中有8种共同血清型,以B群、Cl群、E1群为主。食源性和人源沙门氏菌分别对10类13种和7类7种抗生素有耐药株,耐药率分别为72．2％和38．9％;有5种药敏谱相同;14株3种以上耐药的沙门氏菌有lO种多重耐药谱。结论佛山市食源性和人源沙门氏菌血清型差异不大,有多重耐药现象．提示应从动物和人类两方面引导抗生素的合理使用,建立从源头治理到最终消费目标明确的理性筛选控制体系。     

Distribution and expression of the astA gene (EAST1 toxin) in Escherichia coli and Salmonella

The distribution and expression of the astA gene (EAST1 toxin) among 358 strains of Enterobacteriaceae were studied. The gene was found in 32.6% and 11.9% of Escherichia coli and Salmonella strains, respectively. The majority of E. coli EAST1-positive strains were found among EHEC (88.0%), EAggEC (86.6%), and A-EPEC (58.3%). The gene was present in 16.6% of E. coli strains without known virulence genes. There was no significant variation among the different serotypes of E. coli tested regarding the presence of the gene. For EPEC, 13.7% of the tested strains were astA-positive. Among atypical EPEC (eae+, bfp-, EAF-) and (eae+, bfp+, EAF-) 46.2 and 72.7%, respectively, were positive. The majority of the A-EPEC (87%) and EaggEC (83%) strains expressed the EAST-1 toxin as judged from Ussing chamber experiments. Of 32 EIEC strains studied, 2 possessed and expressed the gene as determined in Ussing chamber experiments. Among the Salmonella strains studied, five strains isolated from food were positive for astA and one strain of S. agona showed biological activity in Ussing chamber experiments.     

Antimicrobial resistance patterns and serotype distribution among Salmonella enterica strains in Turkey, 2000–2002

Since Turkey currently lacks a national reference center for Salmonella infections, the present study was conducted to document the distribution of serotypes and antimicrobial resistance patterns among Salmonella enterica isolates recovered from clinical samples in ten Turkish provinces over a 2-year period. Among the 620 Salmonella enterica isolates recovered between 1 July 2000 and 30 June 2002, strains belonging to the serotypes Enteritidis (47.7%), Typhimurium (34.7%), Paratyphi B (6.0%), Typhi (2.9%), Paratyphi A (0.2%) and serogroup C (8.5%) were found. Resistance to multiple antimicrobial agents was particularly high among Salmonella Typhimurium isolates (76.7%), and resistance or decreased susceptibility to ciprofloxacin (MIC0.125 mg/l) was demonstrated in Salmonella Paratyphi B, Salmonella Typhimurium and Salmonella Enteritidis strains. All of the Salmonella Typhi isolates were susceptible to ciprofloxacin. The results indicate that decreased susceptibility to ciprofloxacin is an emerging problem in Salmonella enterica in Turkey, particularly in multiresistant strains.     

Rapid detection of Salmonella enterica with primers specific for iroB.

The iroB gene of Salmonella enterica is absent from the chromosome of the related organism Escherichia coli. We determined the distribution of this gene among 150 bacterial isolates, representing 51 serotypes of different Salmonella species and subspecies and 8 other bacterial species which are frequent contaminants during routine enrichment procedures by Southern hybridization. An iroB-specific DNA probe detected homologous sequences in all strains of S. enterica, including serotypes of S. enterica subsp. enterica (I), salamae (II), diarizonae (IIIb), and houtenae (IV). No hybridization signal was obtained with strains of Salmonella bongori or other bacterial species. In contrast, hybridization with a DNA probe specific for purD, a purine biosynthesis gene, detected homologs in all bacterial species tested. Primers specific for iroB were used to amplify this gene from 197 bacterial isolates by PCR. The iroB gene could be PCR amplified from S. enterica subsp. enterica (I), salamae (II), diarizonae (IIIb), houtenae (IV), arizonae (IIIa), and indica (VI), but not from S. bongori or other bacterial species. Thus, PCR amplification of iroB can be used to distinguish between S. enterica and other bacterial species, including S. bongori. A combination of preenrichment in buffered peptone water supplemented with ferrioxamine E and amplification of iroB by magnetic immuno-PCR allowed detection of S. enterica in albumen within 24 h. In conclusion, PCR amplification of iroB is a new sensitive and selective method which has the potential to rapidly detect S. enterica serotypes.     

Indirect antigen-trap ELISAs using polyclonal antisera for detection of group B and D Salmonellas in chickens

Indirect antigen-trap ELISAs able to detect Salmonella typhimurium and S. enteritidis are described. Their limits of sensitivity were about 10(7) organisms in nutrient broth culture. With the ELISA developed for S. typhimurium, 76 of 77 strains gave optical density (OD) readings of 1.06 to 1.40. Three other serotypes from group B in the Kaufmann-White scheme gave high values: S. saintpaul produced an OD of 1.40, S. schwarzengrund 0.93 and S. derby 0.88. Twenty other serotypes all produced OD values of 0.39 to 0.66. Four Citrobacter strains and an E. coli produced lower values. With the S. enteritidis ELISA, seven strains of this serotype produced OD values of 1.13 to 1.23 and 13 other serotypes gave OD values of 0.14 to 0.87. There was good correlation between the ELISA and bacteriological culture after examining selenite broth cultures of cloacal swabs taken from experimentally infected chickens. A few samples were positive by ELISA and negative by culture and vice versa. Similar results were obtained from cloacal swabs taken from a commercial flock known to be infected with S. typhimurium. Much closer correlation existed between the two methods for identifying artificially contaminated eggs or for spleens taken from experimentally infected birds.     

Profile of Salmonella enterica subsp. enterica (subspecies I) serotype 4,5,12:i:- strains causing food-borne infections in New York City

Strains of newly emerging Salmonella enterica subsp. enterica (subspecies I) serotype 4,5,12:i:- causing food-borne infections, including a large food poisoning outbreak (n = 86) characterized by persistent diarrhea (14% bloody), abdominal pain, fever, and headache, were examined. The organisms were found in the stool samples from the patients. The biochemical profile of the organisms is consistent with that of S. enterica subsp. I serotypes, except for decreased dulcitol (13%) and increased inositol (96%) utilization. Twenty-eight percent of the strains showed resistance to streptomycin, sulfonamides, or tetracycline only; all three antimicrobial agents; or these agents either alone or in combination with ampicillin, trimethoprim, and trimethoprim-sulfamethoxazole. None of the serotype 4,5,12:i:- strains showed resistance or decreased susceptibility to chloramphenicol or ciprofloxacin. On pulsed-field gel electrophoresis (PFGE), the strains showed 11 or 12 resolvable genomic fragments with 18 banding patterns and three PFGE profile (PFP) clusters (i.e., PFP/A, PFP/B, and PFP/C). Seventy-five percent of the isolates fingerprinted were closely related (zero to three band differences; similarity [Dice] coefficient, 86 to 100%); 63% of these were indistinguishable from each other (PFP/A(1)). PFP/A(1) was common to all strains from the outbreak and 11 hospital sources. Strains from six other hospitals shared clusters PFP/B and PFP/C. PFP/C(4), of the environmental isolate, was unrelated to PFP/A and PFP/B. Nine band differences (similarity coefficient, 61%) were noted between PFP/A(1) and PFP/E of the multidrug-resistant S. enterica subsp. enterica serotype Typhimurium definitive type 104 strains. Whether these emerging Salmonella strains represent a monophasic, Dul(-) variant of serotype Typhimurium or S. enterica subsp. enterica serotype Lagos or a distinct serotype of S. enterica subsp. I is not yet known. Some of the phenotypic and genotypic properties of the serotype 4,5,12:i:- strains are described here.     

An attempt to identify the evolutionary origin of a novel serotype of Salmonella enterica isolated from harbour porpoises

The isolation since 1991 of a new serotype of Salmonella enterica (antigenic formula 4,12:a:-) from harbour porpoises (Phocoena phocoena) at post-mortem examination raised the question of its evolutionary origin. Representative strains of S. enterica serotype 4,12:a:- and strains of eight other serotypes of serogroup 04 with phase-1 flagellar antigen H 'a' were examined by EcoRI ribotyping, IS200 fingerprinting and PCR-based profiling. Statistical analysis of results of multiple typing showed that strains of Salmonella serotype 4,12:a:- were genetically distant from those of antigenically similar salmonella serotypes, none of which seemed likely to be the progenitor of the 'porpoise' serotype.     

Development of a multiplex PCR technique for detection and epidemiological typing of salmonella in human clinical samples

We have developed a multiplex PCR assay for Salmonella detection and epidemiological typing. Six sets of primers were designed to detect the major Salmonella serotypes and phage types in Spain. An internal amplification control was designed in order to detect PCR inhibition. The different amplification profiles obtained allowed us to detect Salmonella bacteria and to distinguish the clinically prevalent Salmonella enterica serotypes Enteritidis, Typhimurium and subspecies I serotype 4,5,12:i:-. Using this method, we could detect a specific band for DT104 and U302 phage types in Salmonella serotype Typhimurium. Salmonella enterica serotype Hadar and other C2 serogroup strains showed two specific band profiles. In the validation stage, the assay was reproducible for all serotypes studied, apart from some C2 serogroup strains. When the technique was applied to clinical stool specimens, the prevalent serotypes Enteritidis and Typhimurium were detected with a sensitivity of 93%, specificity of 100%, and efficiency of 98%. Also, a low PCR inhibition rate (8%) was obtained. The overall agreement of the multiplex PCR with conventional culture-based techniques was 95% for Salmonella typing using Cohen's kappa index.     

Multiple drug resistance in salmonellae in England and Wales: a comparison between 1981 and 1988.

Each year from 1981 through to 1988 the most common serotypes isolated from man in England and Wales and identified at the Division of Enteric Pathogens were S typhimurium, S enteritidis, and S virchow. In 1981 these three serotypes accounted for 45%, 12%, and 7% of isolations. The remaining 35% comprised strains belonging to a further 188 different serotypes, none of which accounted for more than 1% of the total. In 1988 S typhimurium accounted for 24% of isolations, S enteritidis 57%, and S virchow 4%. The remaining 15% comprised strains of a further 184 serotypes. The resistances to the common antimicrobial drugs in non-typhoidal salmonellas isolated in England and Wales in 1981 and 1988 were reported with particular reference to resistance to four or more antimicrobial drugs (multiple resistance). For S typhimurium the overall percentage of resistant strains varied little, but multiple resistance more than doubled from 5% to 12%; in S enteritidis the incidence remained the same. In S virchow the percentages of strains resistant to all the antimicrobial drugs and in particular, to chloramphenicol, streptomycin, trimethoprim and furazolidone, rose from 0.2% to 10.4%. Salmonella enteritis in man is usually a self limiting disease and antimicrobial treatment is seldom required; but should spread beyond the intestine occur, effective antimicrobial treatment is essential. Under these circumstances a knowledge of the likelihood of resistances to commonly available drugs could be of considerable value to the clinician.     

Initial observations in Upper-Volta on 41 serotypes of Salmonella isolated at Muraz Center

Among 186 Salmonella strains isolated at the Muraz Center from 1966 to 1976, representing 45 serotypes, the authors describe 41 serotypes identified for the first time in Upper-Volta, 3 of which constituting new serotypes: S. bobo, S. kua, S. farakan. A few remarks show the significance of Salmonella circulation in a west-africa area where the incidence of bacterial enteric diseases is a constant problem of public health.     

Host specificity of Salmonella infection in chickens and mice is expressed in vivo primarily at the level of the reticuloendothelial system.

By experimental infection, host-specific Salmonella serotypes were shown to demonstrate specificities for chickens, mice, and other laboratory animals. Following oral inoculation, four strains of Salmonella gallinarum and two S. pullorum strains, isolated from diseased poultry, were more virulent for chickens than for mice. By contrast, four strains each of S. choleraesuis and S. dublin, isolated from diseased pigs and cattle, respectively, were more virulent for mice than for chickens. These results were also reflected in the degree of virulence expressed after parenteral inoculation. In addition, S. choleraesuis, but not other serotypes, killed rats, guinea pigs, and rabbits. S. typhimurium strains varied widely in their virulence, and some strains were virulent for both mice and chickens. Four other serotypes isolated from poultry or human food poisoning cases and a nonpathogenic Escherichia coli strain were much less virulent for both experimental host species. Most of the host-specific Salmonella serotypes studied were able to colonize the distal alimentary tract and invade the tissues in both mice and chickens to various degrees. There was, however, a greater difference in the ability to survive and multiply in the visceral organs, particularly the spleen and the liver, once invasion had occurred which correlated with the virulence for the host species involved.     

Antimicrobial resistance and serotype prevalence of Salmonella isolated from dairy cattle in the southwestern United States

Mature dairy cattle were sampled over a 2-year period (2001-2002) on six farms in New Mexico and Texas. Fecal samples (n = 1560) were collected via rectal palpation and cultured for Salmonella, and one isolate from each positive sample was serotyped. Three isolates of each serotype, with the exception of Salmonella Newport (n = 12), were examined for susceptibility to 17 antimicrobial agents. Twenty-two different serotypes were identified from a total of 393 Salmonella isolates. Montevideo was the predominant serotype (27%) followed by Mbandaka (15%), Senftenberg (11.4%), Newport (6.4%), Anatum (4.8%), and Give (4.8%). Salmonella Typhimurium and Dublin, two frequently reported serotypes, accounted for only 1% of the observed serotypes in this study. Sixty-four percent of the serotypes were susceptible to all 17 antimicrobials, 14% were resistant to a single agent, and 22% were multiresistant (2-11 types of resistance). All isolates tested were susceptible to amikacin, apramycin, imipenem, ceftriaxone, nalidixic acid, and ciprofloxacin. The most frequent types of resistance were to sulfamethoxazole, tetracycline, streptomycin, kanamycin, chloramphenicol, and ampicillin (ranging from 8.9 to 22.4%). Serotypes demonstrating multiple resistance included Dublin and Give (resistant to three or more antibiotics), Typhimurium (resistant to five antibiotics), and Newport (four and two isolates resistant to six and nine antibiotics, respectively). Class 1 integrons were present in only two Salmonella Dublin isolates and one Salmonella Newport isolate. The most prevalent resistance patterns observed in this study were toward antimicrobial agents commonly used in cattle, while all Salmonella isolates were susceptible to ceftriaxone and ciprofloxacin, antibiotics used in human medicine.