Antibiofilm activity of a lytic Salmonella phage on different Salmonella enterica serovars isolated from broiler farms

International Microbiology - Bacteriophages have been mainly used in treating infections caused by planktonic bacterial cells in the veterinary sector. However, their...     

Identification of Salmonella enterica subspecies I, Salmonella enterica serovars Typhimurium, Enteritidis and Typhi using multiplex PCR

This study was designed to develop a multiplex PCR method with five specific primer pairs for the detection of Salmonella spp., Salmonella subspecies I, Salmonella enterica serovars Typhimurium, Typhi and Enteritidis. A multiplex PCR was constructed with five primer pairs for the detection of Salmonella and pathogenic Salmonella serovars, including a specific primer pair for Salmonella Typhi, based on the sequence comparison between genomic DNA sequences of 12 Salmonella strains. Each primer pair was specifically targeted to Salmonella spp., Salmonella subspecies I, Salmonella Typhimurium, Typhi and Enteritidis. This multiplex PCR was evaluated with various DNAs of Salmonella serovars that yielded high specificity for amplifying the expected PCR products of Salmonella serovars. Using this primer pair, a set of multiplex PCR was performed for the rapid identification of salmonellae and major pathogenic Salmonella serovars. Although this multiplex PCR method will need to be evaluated for a wide range of Salmonella serovars among multilaboratories, it should be useful for identifying clinically significant strains of Salmonella serovars rapidly and accurately without the need for serological testing.     

Salmonellae isolated from captive animals in Ibadan, Western State of Nigeria

Six serotypes of salmonellae, Salmonella offa, S. glostrup, S. wimborne, S. dublin, S. saint-paul and S. webridge were isolated from captive wild animals in Ibadan, Western State of Nigeria. S. wimborne and S. glostrup are reported for the first time in Nigeria. All strains were sensitive to nitrofurantoin (200 mcg) and chloramphenical (10 mcg) but there wasmarked resistance to sulphafurazole (100 mcg) and penicillin (1.5 units).     

Antibiograms of pathogenic bacteria isolated from laboratory rabbits in Ibadan, Nigeria

Antibiotic sensitivity patterns of 21 bacterial isolates from some clinically ill New Zealand rabbits were evaluated against 12 commonly used antibiotics by the Kirby-Bauer disk-diffusion sensitivity testing method. The 21 isolates consisted of six Bordetella bronchiseptica, eight Pasteurella multocida, four Staphylococcus aureus and three Pseudomonas alcaligenes that were associated with snuffles, pneumonia, otitis media, genital infections and conjunctivitis in these groups of caged rabbits. The four bacteria species were all sensitive to kanamycin, gentamycin and enrofloxacin, with variable sensitivity to the other antibiotics tested. The results of this antibiogram could serve as a field guide in the treatment of very acute bacterial diseases of rabbit prior to the availability of the results of local sensitivity tests. Such sensitivity tests should be reviewed yearly to update this antibiogram.     

Detection of hilA gene sequences in serovars of Salmonella enterica subspecies enterica

hilA gene promoter, component of the Salmonella Pathogenicity Island 1, has been found in Salmonella serovar Typhimurium, being important for the regulation of type III secretion apparatus genes. We detected hilA gene sequences in Salmonella serovars Typhi, Enteritidis, Choleraesuis, Paratyphi A and B, and Pullorum, by polymerase chain reaction (PCR) and hybridization techniques. The primers to carry out PCR were designed according to hilA sequence. A low stringency hybridization with the probe pVV441 (hilA open-reading-frame plasmid) was carried out. To find hilA gene sequences in other Salmonella sp. suggest that these serovars could have similar sequences of this kind of virulence genes.     

Epidemiological analysis of Salmonella enterica ssp. enterica serovars Hadar, Brancaster and Enteritidis from humans and broiler chickens in Senegal using pulsed-field gel electrophoresis and antibiotic susceptibility

AIMS: Salmonella Hadar, Salmonella Brancaster and Salmonella Enteritidis are the main Salmonella enterica ssp. enterica serovars isolated from poultry in Senegal. Our objective was to analyse the pulsed-field gel electrophoresis (PFGE) and antibioresistance patterns of strains belonging to these serovars and to assess the significance of broiler-chicken meat as a source of human infection. METHODS AND RESULTS: A total of 142 Salmonella isolates were analysed: 79 were isolated from Senegalese patients with sporadic diarrhoea (11 S. Hadar, nine S. Brancaster and 59 S. Enteritidis) and 63 from poultry (30 S. Hadar, 17 S. Brancaster and 16 S. Enteritidis). The PFGE of XbaI- and SpeI-digested chromosomal DNA gave 20 distinct profiles for S. Hadar, nine for S. Brancaster and 22 for S. Enteritidis. Each serovar was characterized by a major pulsotype which was X3S1 in 42% of S. Hadar, X8S1 in 53.8% of S. Brancaster and X1S2 in 43% of S. Enteritidis isolates. Human and poultry isolates of Salmonella had common PFGE patterns. Antibiosensitivity tests showed multiresistance (more than two drugs) was encountered in 14.5% of S. Hadar and in 5% of S. Enteritidis isolates. Resistance to quinolones was considered to be of particular importance and 14.5% of S. Hadar isolates were found to be resistant to nalidixic acid. CONLCUSIONS: The sharing of similar PFGE profiles among isolates from humans and poultry provided indirect evidence of Salmonella transmission from contaminated broiler meat. But most of the Salmonella isolates remained drug sensitive. SIGNIFICANCE AND IMPACT OF THE STUDY: Efforts are needed to eliminate Salmonella from poultry meat intended for human consumption. This study has also highlighted the importance of continuous surveillance to monitor antimicrobial resistance in bacteria associated with animals and humans.     

Occurrence of sopE gene and its phenotypic expression among different serovars of Salmonella enterica isolated from man and animals

Salmonella pathogenesis is a complex phenomenon and a Type III secretion system plays a central role in the development of Salmonella-induced enteritis. One such Type III secretion protein is Salmonella outer protein E (SopE). Prevalence of sopE gene and its phenotypic expression (SopE protein) among different serovars of Salmonella enterica isolated from man and animals were investigated. Of 305 strains of S. enterica belonging to 11 serovars tested for the presence of sopE, 130 strains belonging to three serovars viz., Enteritidis, Gallinarum and Virchow were found to carry sopE gene irrespective of their source of isolation when tested by PCR amplification technique using its specific primers. Of these 130 strains, 112 strains were found to express SopE protein phenotypically as detected by Dot-ELISA using SopE antibody. Among the different serovars tested only serovars Gallinarum, Enteritidis and Virchow expressed SopE protein phenotypically in vitro. Role of SopE protein in pathogenesis of salmonellosis has been discussed.     

Prevalence of Salmonella enterica serovars and genovars from chicken carcasses in slaughterhouses in Spain

AIMS: To determine the prevalence of Salmonella enterica serovars in chicken carcasses in slaughterhouses in Spain and to examine genotypic relations among these serovars. METHODS AND RESULTS: A total of 336 chicken carcasses were collected from six slaughterhouses in Northwestern Spain. Salmonellae were isolated (ISO-6579-1993), serotyped, phage-typed, ribotyped and antibiotyped against 20 antibiotics. Salmonella strains were detected in 60 (17.9%) carcasses. Isolates belonged to nine different serotypes, with Salm. Enteritidis being the most common. Three strains (5%) were resistant to one antibiotic and 24 (40%) were multi-resistant (to more than one antibiotic). The most frequently encountered resistances were to sulphamides, fluoroquinolones and tetracycline. Ribotyping was able to differentiate isolates of the same serotype and phage type. CONCLUSIONS: The Salmonella serotypes and phage types detected are among those most frequently associated with human diseases in Spain. The large percentage of antimicrobial resistant strains is a matter for concern. A high genetic relationship between strains from different slaughterhouses was found. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides detailed information about Salmonella isolates from poultry in Spain. It emphasizes the importance of controlling this pathogen in poultry products, and suggests the need for more prudent use of antibiotics.     

Plasmid-mediated antimicrobial resistance in Salmonella enterica

The selective pressure imposed by the use of antimicrobials in both human and veterinary medicine promotes the spread of multiple antimicrobial resistance. The dissemination of antimicrobial resistance in Salmonella enterica strains, causing severe enteritis in human, has been reported worldwide and is largely attributed to conjugative DNA exchange. In the present review, the relevance of plasmids to the dissemination of antimicrobial resistance in S. enterica is discussed. Recent examples of plasmid-mediated resistance to expanded-spectrum cephalosporins are reported to illustrate the severity of current situation in enteric pathogens. The exchanges between plasmid(s) and the bacterial chromosome and the integration of resistance genes into specialised genetic elements, called integrons, play a major role in acquisition and dissemination of resistance genes. The evolution of a plasmid through the acquisition of integrons is reported, describing novel mechanisms for short-term accumulation of resistance determinants in plasmids circulating in Salmonella.     

Rapid detection of Salmonella enterica serovars by multiplex PCR

A multiplex PCR based assay was developed for the identification of the genus Salmonella. Five sets of primers from different genomic sequences such as fimA, himA, hns, invA and hto genes were selected for the identification of serogroups of Salmonella enterica such as S. Typhi, S. ParatyphiA, S. Typhimurium, S. Enteritidis and S. Weltevreden. The selected primers amplified products with the sizes of 85, 123, 152, 275 and 496 bp, respectively, for the genus Salmonella. This assay was found to be highly sensitive, as it could detect 5 cells of Salmonella and 1,000 fg of genomic DNA. Amplification of DNA extracted from other genera viz. V. cholerae and E. coli yielded negative results. This assay provides specific and reliable results and allows for the cost–effective detection of Salmonella in one reaction tube in mixed bacterial communities.     

Inhibition of Salmonella enterica serovars by microcin J25

Escherichia coli microcin J25 (MccJ25) is a 2107-Da peptide antibiotic whose uptake into E. coli is mediated by the outer-membrane receptor FhuA and the inner membrane proteins TonB, ExbB, ExbD, and SbmA. A survey of the sensitivity of several Salmonella enterica serovars showed that the antibiotic was highly active against some serovars, while S. Typhimurium, S. Derby, and some S. Enteritidis strains were completely resistant. Resistant strains became hypersensitive to MccJ25 when given the fhuA gene of E. coli, indicating that insensitivity is due to the inability of the FhuA protein to mediate penetration of MccJ25. Whereas in E. coli MccJ25 targets RNA polymerase, in S. Typhimurium it inhibits not only RNA synthesis but also cell respiration. Fluorescence viability staining showed that S. Typhimurium cells exposed to MccJ25 remain viable but are unable to form colonies.     

Colicinogeny in Salmonella serovars isolated in Brazil

A study of colicinogeny was made in 748 strains of Salmonella (97 serovars) isolated from different sources: human (291), animal (119), environmental (141), food (102) and animal feed (95). Colicin production was detected in 64 strains (8.6%), particularly isolated from foods (30.4%). Col E1 (53) and Ia (44) were the most frequently observed, especially in S. agona for environment and food sources. Col V production was identified in 5 strains of S. typhimurium within 8 producer cultures isolated from humans. Its relationship with the sources and serovars of Salmonella are discussed.     

Fluoroquinolone resistance in Salmonella serovars isolated from humans and food animals

Quinolone-resistant Salmonella enterica usually contain a mutation in gyrA within the region encoding the quinolone resistance determining region of the A subunit of DNA gyrase. These mutations confer substitutions analogous to Escherichia coli Ser83-->Phe and Asp87-->Gly or Tyr, or a novel mutation resulting in Ala119-->Glu or Val. Mutations in gyrB are rare, and no mutations in parC or parE have been described. Quinolone-resistant Salmonella can also be cross-resistant to other agents including chloramphenicol and tetracycline. Increased efflux has been demonstrated and for some strains this has been associated with increased expression of acrB. Mutation in soxR has also been shown for one isolate. Detection of low level resistance (minimum inhibitory concentrations <0.5 microg ml(-1)) to fluoroquinolones is proving an increasing problem in the treatment of invasive Salmonella infections.     

Molecular fingerprinting of Salmonella enterica subsp. enterica Typhimurium and Salmonella enterica subsp. enterica derby isolated from tropical seafood in South India

Salmonella enterica subsp. enterica Typhimurium and Salmonella enterica subsp. enterica Derby strains isolated from different seafood were genotyped by PCR-ribotyping and ERIC-PCR assays. This study has ascertained the genetic relatedness among serovars prevalent in tropical seafood. PCR-ribotyping exhibited genetic variation in both Salmonella serovars, and ribotype profile (II) was most predominant, which was observed in 10/18 of Salmonella enterica subsp. enterica Typhimurium and 7/17 Salmonella enterica subsp. enterica Derby isolates. Cluster analysis of ERIC-PCR for Salmonella enterica subsp. enterica Typhimurium strains exhibited nine different banding patterns and four strains showed >95% genetic homology within the cluster pairs. ERIC-PCR produced more genetic variations in Salmonella enterica subsp. enterica Typhimurium; nevertheless, both methods were found to be comparable for Salmonella enterica subsp. enterica Derby isolates. Discrimination index of PCR-ribotyping for Salmonella enterica subsp. enterica Typhimurium isolates was obtained at 0.674 and index value 0.714 was observed for Salmonella enterica subsp. enterica Derby strains. Molecular fingerprinting investigation highlighted the hypothesis of diverse routes of Salmonella contamination in seafood as multiple clones of Salmonella enterica subsp. enterica Typhimurium and Salmonella enterica subsp. enterica Derby were detected in same or different seafood throughout the study period.     

Salmonella enterica serotype Bredeney: antimicrobial susceptibility and molecular diversity of isolates from Ireland and Northern Ireland.

Salmonella enterica serotype Bredeney has emerged as the third most commonly identified serotype among human clinical isolates referred to the Irish National Salmonella Reference Laboratory in the years 1998 to 2000. A collection of 112 isolates of S. enterica serotype Bredeney collected during the period 1995 to 1999 from animal, food, and human sources from both Ireland and Northern Ireland were studied. Antimicrobial susceptibility testing, pulsed-field gel electrophoresis (PFGE), and DNA amplification fingerprinting (DAF) were performed on all isolates. Plasmid profiles were examined on a subset of 33 isolates. A high proportion (74%) of isolates were susceptible to all antimicrobial agents tested. Resistance to both sulfonamide and trimethoprim was observed in 21% of isolates, and resistance to multiple (five) antimicrobial agents was observed in a single isolate (0.9%). Eight different PFGE patterns were obtained, with 87% of isolates grouping as PFGE type A. PFGE type A was predominant in animals, food, and humans. There was good overall concordance between the groups identified by PFGE and DAF. Overall results indicate that most S. enterica serotype Bredeney isolates in Ireland and Northern Ireland from animal and human sources are clonally related.     

Genetic diversity and antimicrobial susceptibility of motile aeromonads isolated from rainbow trout (Oncorhynchus mykiss, Walbaum) farms

A total of 22 motile Aeromonas strains were detected in 48 (18.53%) of 259 fish and 6 (10.71%) of 56 water samples obtained from seven commercial rainbow trout ( Oncorhynchus mykiss , Walbaum) farms in the province of Mersin, Turkey. These strains were identified by conventional microbiological techniques and by using an ID32GN system. Of these isolates 20 (91.3%) were identified as Aeromonas hydrophila and 2 (8.7%) as Aeromonas sobria . While 8 of the A. hydrophila strains were isolated from water samples, 12 isolates were from fish samples. Whereas A. hydrophila strains were found in all farms, A. sobria was detected in only two farms. Genetic diversity by arbitrarily primed polymerase chain reaction (AP-PCR) and antimicrobial sensitivity tests were carried out on eight A. hydrophila isolates obtained from water samples, and isolates from seven A. hydrophila and one A. sobria from fish samples. The AP-PCR band patterns of motile aeromonads demonstrated weak similarity to the A. hydrophila reference strain ATCC 7966. Five A. hydrophila strains in the water samples displayed genetic similarity, but three others were different. Aeromonas hydrophila isolates from fish samples possessed slight similarities, and A. sobria was genetically distant to all A. hydrophila strains. An antimicrobial sensitivity test of 16 isolates revealed that 100% were sensitive to gentamicin, 87.5% to sulphamethoxazole–trimethoprim, 62.5% to enrofloxacin, 43.8% to oxytetracycline, 37.5% to neomycin, 18.75% to streptomycin and 6.25% to erythromycin. All isolates were resistant to novobiocin.