Salmonellaserovars and their antimicrobial resistance in British turkey flocks in 1995 to 2006

Salmonella Control in Swine: A Thoughtful Discussion of the Pre- and Post-Harvest Control Approaches in Industrialized Countries

Pork is among the major sources of human salmonellosis in developed countries. Since the 1990s, different surveys and cross-sectional studies, both national and international (i.e., the baseline studies performed in the European Union), have revealed and confirmed the widespread non-typhoidal Salmonella serotypes in pigs. A number of countries have implemented control programs with different approaches and degrees of success. The efforts could be implemented either at farms, in post-harvest stages, or both. The current review revises the current state of the art in Salmonella in swine, the control programs ongoing or conducted in the past, and their strengths and failures, with particular attention to the weight of pre- and post-harvest control and the implications that both have for the success of interventions or mitigation after outbreaks. This review provides a novel perspective on Salmonella control in swine, a matter that still includes uncertainties and room for improvement as a question of public health and One Health.

Salmonella Prophages, Their Propagation, Host Specificity and Antimicrobial Resistance Gene Transduction

Salmonella enterica subsp. enterica is a zoonotic bacterial pathogen that causes foodborne outbreaks in humans. Lytic bacteriophages to control Salmonella in food production are already being used in scientific studies and some are commercially available. However, phage application is still controversial. In addition to virulent phages, which are used in phage therapy and lyse the bacterial host, lysogenic phages coexist in the environment and can reside as prophages in the bacterial host. Therefore, information about Salmonella prophages is essential to understand successful phage therapy. In 100 Salmonella food isolates of the serovars Enteritidis and Typhimurium, we propagated prophages by oxidative stress. In isolates of the serovars Typhimurium and Enteritidis, 80% and 8% prophages could be activated, respectively. In the phage lysates from the serovar Typhimurium, the following antibiotic resistance genes or gene fragments were detected by PCR: sul1, sul2, blaTEM, strA and cmlA; however, no tetA,B,C, blaOXA, blaCMY, aadA1, dfr1,2 or cat were detected. In contrast, no resistance genes were amplified in the phage lysates of the serovar Enteritidis. None of the phage lysates was able to transduce phenotypic resistance to WT 14028s. Most of the prophage lysates isolated were able to infect the various Salmonella serovars tested. The high abundance of prophages in the genome of the serovar Typhimurium may counteract phage therapy through phage resistance and the development of hybrid phages.

A longitudinal observational study of Salmonella shedding patterns by commercial turkeys during rearing and fattening, showing limitations of some control measures

1. The onset and progression of Salmonella infections was investigated in commercial turkey flocks from placement at 1 d old until slaughter in "brood and move" systems using a longitudinal observational approach based on faeces and environmental sampling with subsequent culture of Salmonella. 2. Persistent Salmonella Newport contamination was found within rearing houses and on their external concrete aprons after cleaning and disinfection between crops of heavily shedding young birds. 3. Salmonella shedding was often detected by 5 d of age and the frequency of positive samples peaked at 14-35 d. Thereafter Salmonella isolations declined, especially in the later (fattening) stages. Samples were still Salmonella-positive at low prevalence in half of the intensively sampled houses at slaughter age. 4. A number of management interventions to combat Salmonella infection of flocks, including sourcing policy, competitive exclusion cultures and cleaning and disinfection, were inadequate to prevent flock infection, although improved disinfection on one unit was associated with a delay in the onset of flock infection.

Serotype distribution of Salmonella isolates from turkey ground meat and meat parts

The aim of the study was to find out the serotype distribution of 169 Salmonella colonies recovered from 112 Salmonella positive ground turkey (115 colonies) and 52 turkey meat parts (54 colonies). Out of 15 Salmonella serotypes: S. Corvallis, S. Kentucky, S. Bredeney, S. Virchow, S. Saintpaul and S. Agona were identified as the predominant serovars at the rates of 27%, 13%, 12%, 12%, 11%, and 10%, respectively. Other serotypes were below 6% of the total isolates. All S. Kentucky and S. Virchow and most of the S. Corvallis (39/46) and S. Heidelberg (9/9) serotypes were recovered from ground turkey. The results indicate that turkey ground meat and meat parts were contaminated with quite distinct Salmonella serotypes. This is the first study reporting Salmonella serotype distribution in turkey meat and S. Corvallis as predominant serotype in poultry meat in Turkey.

Distribution of Salmonella serovars and antimicrobial susceptibility of Salmonella Enteritidis from poultry in Zimbabwe

A study was carried out to determine the distribution and antimicrobial susceptibility profiles of Salmonella serovars from chickens from large-scale commercial (LSC), small-scale commercial (SSC), and rural free-range (RFR) farms of Zimbabwe. Pooled cloacal swabs were collected for culture and isolation of Salmonella spp. A chi-square test was used to assess distribution differences of salmonellas among the farming sectors. Approximately 10% (283/2833) of the swabs were positive for Salmonella enterica, with only subspecies enterica (98.6%) and arizonae (1.4%) being detected. The prevalence of S. enterica varied significantly (P<0.05) among areas, with Harare (27.8%) and Buhera (1.3%) recording the highest and the least prevalence, respectively. S. enterica was only isolated from LSC and SSC farms, with the former having a significantly (P<0.001; χ(2)=155.3) higher prevalence than the latter. S. arizonae was only isolated from the SSC farms while none were obtained from the RFR farms. The serovars isolated were Salmonella Enteritidis (72.8%), Group C (20.1%), Group B (4.2%), Salmonella Typhimurium (1.1%) and Salmonella Gallinarum (0.4%). S. Enteritidis predominated in the urban/periurban areas. Approximately 26% (53/206) of S. Enteritidis isolates were resistant to one or more antimicrobial agents. Resistance to tetracycline was the most common, while no resistance was detected for furazolidone, neomycin and trimethoprim-sulfamethoxazole. There were 12.1% multi-drug-resistant S. Enteritidis isolates, and the resistance to ampicillin/kanamycin was predominant. The identification of multi-drug-resistant S. Enteritidis is of public health concern. Thus, stringent control of S. Enteritidis will reduce the public health risk of human salmonellosis.