Protection of chicks against environmental challenge with Salmonella enteritidis by 'competitive exclusion' and acid-treated feed

'Competitive exclusion' treatment protected chicks against an environmental challenge with Salmonella enteritidis phage type 4, whether or not feed containing antimicrobial organic acids was also used. Treatment reduced the incidence of Salmonella -positive caecal samples from 82 to 8%, with a corresponding reduction in liver infection from 52 to 13%. Although acid-treated feed had no influence on an environmental challenge with salmonellas, its compatibility with 'competitive exclusion' suggests an advantage in their combined use to maximize protection of poultry against Salmonella infection.     

Early antibody response in mice to either infection or immunization with Salmonella typhimurium

After immunization with either live or heat-killed Salmonella typhimurium, mice responded with an extremely rapid production of bactericidal antibody which was correlated with the appearance of immunity to a heavy challenge dose (100 ld(50)) of the virulent bacteria. Inactivation of sera with mercaptoethanol along with Sephadex fractionation indicated that the observed bactericidal activity was associated with a macroglobulin which was completely mercaptoethanol-sensitive. The unexpected finding, that a heat-killed vaccine gave excellent protection from a challenge dose which killed all unimmunized control mice, seriously challenges the theory attributing immunity against typhoid infection entirely to a cellular host factor produced only in response to a live vaccine.     

Salmonella control in poultry: the need for the satisfactory evaluation of probiotics for this purpose

The Editors of Letters in Applied Microbiology will, at their discretion, publish invited and submitted 'Opinions' on subjects in the general area of Applied Microbiology. They will not be subjected to the normal refereeing procedures and reprints will not be provided. The 'Opinions' will not necessarily represent the views of the Society for Applied Bacteriology or of the Editors. The Editors may invite or readers may submit 'Responses' to published 'Opinions' , provided that they are not merely polemics, and these will also be published at the discretion of the Editors. 'Responses' will be treated precisely like 'Opinions' . They should clearly indicate, in their first sentence, the 'Opinion' to which they are a response.     

Microbial-resistant Salmonella enteritidis isolated from poultry samples

Background:

Multidrug resistance in Salmonella enteritidis isolates is a public health problem worldwide; the present study, therefore, was designed for antimicrobial-resistance determination in this strain.

Methods:

Salmonella strains isolated from poultry samples by biochemical positive and negative tests were subjected to PCR and identified as Salmonella enteritidis. For detection and identification of Salmonella enteritidis isolates, sdfI gene-specific primers were used.

Results:

We found that 100% of isolates were resistant to ampicillin, 90% were resistant to cephalothin and streptomycin, 70% were resistant to cefotaxime, and 60% were resistant to kanamycin and gentamicin.

Conclusion:

Salmonella enteritidis isolates had antimicrobial resistance to mentioned antibiotics. Key Words: Antibiotic Resistance, PCR, Poultry, Salmonella enteritidis     

Antibiotic resistance and molecular characterization of poultry isolates of Salmonella by RAPD-PCR

The antibiotic resistance profile of 17 poultry isolates of Salmonella was studied against 24 different antibiotics. 69–88% of the Salmonella isolates displayed a high level of resistance, particularly against penicillin, rifampicin, erythromycin, clarithromycin, clindamycin, sulphamethoxazole and vancomycin. In contrast, a relatively low or moderate level of resistance was observed against furazolidone, spectinomycin, ciprofloxacin, chloramphenicol, cefepime, carbenicillin, nalidixic acid, streptomycin, oxacillin and cephalothin (11–59%). Moreover, resistance to multiple antibiotics (2–5) was also observed among the Salmonella strains, and none of the isolates was found susceptible to all the antibiotics used. Similarity coefficient among Salmonella strains by RAPD-PCR analysis varied from 0.60 to 0.86, and all the salmonellae could be classified into seven groups on the basis of dendrogram analysis. Generally, a very high level of concordance between RAPD-PCR profile and antibiotic profile was not observed, which indicates that genes for antibiotic resistance may not always be present on genomic DNA rather may be plasmid-borne.     

Flagellin expressed by live Salmonella vaccine strains induces distinct antibody responses following delivery via systemic or mucosal immunization routes

Salmonella flagellin, expressed as flagella in live attenuated vaccine strains, elicits distinct systemic (IgG) and secreted (IgA) antibody responses in mice following delivery via mucosal (nasal/oral) or parenteral (intraperitoneal (i.p.)) immunization routes. Reduced flagellin-specific antibodies were detected either systemically or locally following delivery of flagellated derivatives of aroA Salmonella enterica serovar Dublin SL1438 via the nasal route, the most effective mucosal site for activation of immune responses in mice. In contrast, flagellin represents the most potent Salmonella antigen for the generation of specific serum antibody (IgG) responses following i.p. inoculations. The distinct immunogenic properties of Salmonella flagellin could not be ascribed to deficient colonization, reduced invasive ability or loss of the flagellin expression by the flagellated vaccine strains.     

Growth/survival of Salmonella enteritidis on fresh poultry and fish stored under vacuum or modified atmosphere

G.-J.E. NYCHAS AND C.C. TASSOU. 1996. The effect of vacuum and modified atomosphere packaging on the growth/survival of Samonella entertidis on fresh poultry and fish (Boops boos) is described. Salmonella enteritidis survived but did not grow significantly in all samples (poultry or fish) at 3^oC. At 10^oC the numbers of Salm. enteritidis increased rapidly in vacuum-packed samples and in samples flushed with 100% N₂, 20%, CO²/80% O² of both types of proteinaceous food. Growth was also evident in fish and poultry flushed with 100% CO²; however the rate of growth was greater in fish samples rather than in poultry.     

Advances in enteropathogen control in poultry production

Poultry meat has been associated frequently and consistently with the transmission of enteric pathogens, including Salmonella and Campylobacter. This association has resulted in the development of HACCP‐based intervention strategies. These strategies (hurdles) begin with elite breeder flocks and filter down the production pyramid. These hurdles include those already established, such as biosecurity, vaccination, competitive exclusion, pre‐ and probiotics, feed and water control, and those more experimental, such as bacteriophage or immunoglobulin therapy. The reduction in enteropathogens entering the processing plant, which employs critical control points, further reduce the exposure of consumers to these organisms. The synergistic application of hurdles will result in an environment that is restrictive and detrimental to enteropathogen colonization and contamination.     

Identification by a multiplex PCR-based assay of Salmonella Typhimurium and Salmonella Enteritidis strains from environmental swabs of poultry houses

A multiplex-PCR-based assay (m-PCR) was developed for the detection of Salmonella and for the identification of the two serotypes Enteritidis and Typhimurium. Three sets of primers selected from different genomic sequences amplified a 429 bp fragment specific for the genus Salmonella within a randomly cloned sequence, a 559 bp target specific for Salmonella Typhimurium within the fliC gene and a 312 bp fragment specific for Salmonella Enteritidis within the sefA gene. The m-PCR-based assay was used for detecting Salmonella from 1078 environmental swabs of poultry houses. Prior to PCR, these swabs were pre-enriched in phosphate-buffered peptone water for 18-20 h and then sub-cultured on a Modified Semi-solid Rappaport Vassiliadis medium (MSRV) for 18-20 h. The m-PCR combined with MSRV had a better sensitivity (95%) than the bacteriological method (92.5%). The MSRV-m-PCR assay and the bacteriological method had an agreement rate of 95.6%.     

Salmonella Enteritidis bacteriophage candidates for phage therapy of poultry

Aims: Salmonella is a worldwide foodborne pathogen causing acute enteric infections in humans. In the recent years, the use of bacteriophages has been suggested as a possible tool to combat this zoonotic pathogen in poultry farms. This work aims to isolate and perform comparative studies of a group of phages active against a collection of specific Salmonella Enteritidis strains from Portugal and England. Also, suitable phage candidates for therapy of poultry will be selected. Methods and Results: The Salm. Enteritidis strains studied were shown to have a significantly high occurrence of defective (cryptic) prophages; however, no live phages were found in the strains. Bacteriophages isolated from different environments lysed all except one of the tested Salm. Enteritidis strains. The bacteriophages studied were divided into different groups according to their genetic homology, RFLP profiles and phenotypic features, and most of them showed no DNA homology with the bacterial hosts. The bacteriophage lytic efficacy proved to be highly dependent on the propagation host strain. Conclusions: Despite the evidences shown in this work that the Salm. Enteritidis strains used did not produce viable phages, we have confirmed that some phages, when grown on particular hosts, behaved as complexes of phages. This is most likely because of the presence of inactive phage‐related genomes (or their parts) in the bacterial strains which are capable of being reactivated or which can recombine with lytic phages. Furthermore, changes of the bacterial hosts used for maintenance of phages must be avoided as these can drastically modify the parameters of the phage preparations, including host range and lytic activity. Significance and Impact of the Study: This work shows that the optimal host and growth conditions must be carefully studied and selected for the production of each bacteriophage candidate for animal therapy.     

Enzyme-linked immunosorbent assay for detection of Salmonella lipopolysaccharide in poultry specimens

An enzyme-linked immunosorbent assay (ELISA) for detection of salmonellae was developed and evaluated by using artificially contaminated specimens of poultry feed, feces, litter, or carcass rinsings, and naturally contaminated water samples. Specimens containing salmonellae of serogroups B or C2 inhibited the binding of polyvalent anti-O serum to microtiter plate wells coated with lipopolysaccharide of Salmonella typhimurium (serogroup B) or Salmonella albany (serogroup C2), respectively. Treatment of specimens with Rhozyme 41 (a protease) inhibited nonspecific reactions. The ELISA detected 106 of 111 culture-positive specimens contaminated with salmonellae of serogroups B or C2. Nineteen of 20 specimens containing salmonellae of serogroup C1 and all of 36 culture-negative specimens were ELISA negative. All seven water samples that contained salmonellae of serogroups B or C2, including three that were culture positive only after delayed secondary enrichment, were ELISA positive. Seven of the nine water samples that contained salmonellae of other serogroups, and all 38 culture-negative samples, were ELISA negative. The ELISA was simple to perform, produced results in 48 h, and was more economical than culture methods.     

Enzyme-linked immunosorbent assay for detection of Salmonella lipopolysaccharide in poultry specimens.

An enzyme-linked immunosorbent assay (ELISA) for detection of salmonellae was developed and evaluated by using artificially contaminated specimens of poultry feed, feces, litter, or carcass rinsings, and naturally contaminated water samples. Specimens containing salmonellae of serogroups B or C2 inhibited the binding of polyvalent anti-O serum to microtiter plate wells coated with lipopolysaccharide of Salmonella typhimurium (serogroup B) or Salmonella albany (serogroup C2), respectively. Treatment of specimens with Rhozyme 41 (a protease) inhibited nonspecific reactions. The ELISA detected 106 of 111 culture-positive specimens contaminated with salmonellae of serogroups B or C2. Nineteen of 20 specimens containing salmonellae of serogroup C1 and all of 36 culture-negative specimens were ELISA negative. All seven water samples that contained salmonellae of serogroups B or C2, including three that were culture positive only after delayed secondary enrichment, were ELISA positive. Seven of the nine water samples that contained salmonellae of other serogroups, and all 38 culture-negative samples, were ELISA negative. The ELISA was simple to perform, produced results in 48 h, and was more economical than culture methods.     

Heat inactivation of Salmonella spp. in fresh poultry compost by simulating early phase of composting process

Aims: The purpose of this study was to determine the effect of moisture on thermal inactivation of Salmonella spp. in poultry litter under optimal composting conditions. Methods and Results: Thermal inactivation of Salmonella was studied in fresh poultry compost by simulating early phase of composting process. A mixture of three Salmonella serotypes grown in Tryptic soy broth with rifampin (TSB‐R) was inoculated in fresh compost with 40 or 50% moisture at a final concentration of c. 7 log CFU g^?1. The inoculated compost was kept in an environmental chamber which was programmed to rise from room temperature to target composting temperatures in 2 days. In poultry compost with optimal moisture content (50%), Salmonella spp. survived for 96, 72 and 24 h at 50, 55 and 60°C, respectively, as compared with 264, 144 and 72 h at 50, 55 and 60°C, respectively, in compost with suboptimal moisture (40%). Pathogen decline was faster during the come‐up time owing to higher ammonia volatilization. Conclusions: Our results demonstrated that Salmonella spp. survived longer in fresh poultry compost with suboptimal moisture of 40% than in compost with optimal moisture of 50% during thermophilic composting. High nitrogen content of the poultry compost is an additional factor contributing to Salmonella inactivation through ammonia volatilization during thermal exposure. Significance and Impact of the Study: This research validated the effectiveness of the current composting guidelines on Salmonella inactivation in fresh poultry compost. Both initial moisture level and ammonia volatilization are important factors affecting microbiological safety and quality of compost product.     

Prevalence and characterization of motile Salmonella in commercial layer poultry farms in Bangladesh

Salmonella is a globally widespread food-borne pathogen having major impact on public health. All motile serovars of Salmonella enterica of poultry origin are zoonotic, and contaminated meat and raw eggs are an important source to human infections. Information on the prevalence of Salmonella at farm/holding level, and the zoonotic serovars circulating in layer poultry in the South and South-East Asian countries including Bangladesh, where small-scale commercial farms are predominant, is limited. To investigate the prevalence of Salmonella at layer farm level, and to identify the prevalent serovars we conducted a cross-sectional survey by randomly selecting 500 commercial layer poultry farms in Bangladesh. Faecal samples from the selected farms were collected following standard procedure, and examined for the presence of Salmonella using conventional bacteriological procedures. Thirty isolates were randomly selected, from the ninety obtained from the survey, for serotyping and characterized further by plasmid profiling and pulsed-field gel electrophoresis (PFGE). Results of the survey showed that the prevalence of motile Salmonella at layer farm level was 18% (95% confidence interval 15-21%), and Salmonella Kentucky was identified to be the only serovar circulating in the study population. Plasmid analysis of the S. Kentucky and non-serotyped isolates revealed two distinct profiles with a variation of two different sizes (2.7 and 4.8 kb). PFGE of the 30 S. Kentucky and 30 non-serotyped isolates showed that all of them were clonally related because only one genotype and three subtypes were determined based on the variation in two or three bands. This is also the first report on the presence of any specific serovar of Salmonella enterica in poultry in Bangladesh.     

Enumeration of Salmonella from poultry carcass rinses via direct plating methods

Aim: To evaluate direct plating methods for the estimation of Salmonella load in poultry carcass rinses. Methods and Results: Two direct plating tools, the spiral plate count method (SPCM) and the hydrophobic grid membrane filtration (HGMF) method, were adapted to support quantification of Salmonella during poultry processing. Test samples consisted of 180 broiler carcasses from a commercial abattoir, 60 from each of three points in the processing line [pre‐inside–outside bird wash (pre‐IOBW), prechill and postchill]. The SPCM was used to estimate Salmonella load in pre‐IOBW rinses, while HGMF was used to estimate Salmonella levels in prechill and postchill rinses. Carcass rinses were also evaluated for Salmonella prevalence by enrichment methods. Mean prevalences of Salmonella were 95%, 100% and 41·7%, and the geometric mean loads were 3·7 × 10¹, 5·6 × 10⁰ and 5·0 × 10^?2 CFU ml^?1 for pre‐IOBW, prechill and postchill rinses, respectively. Conclusions: The methods described are useful for estimating the concentration of viable and typical Salmonella in poultry carcass rinses. Significance and Impact of the Study: Direct plating enumeration methods can facilitate the monitoring of Salmonella load on poultry carcasses throughout the production process, and the evaluation of new processing intervention strategies.