The socio-economic impact of human Salmonella enteritidis infection

The Economic Burden of Non-Typhoidal Salmonella and Invasive Non-Typhoidal Salmonella Infection: A Systematic Literature Review

Non-typhoidal Salmonella (NTS) infection and invasive non-typhoidal Salmonella (iNTS) infection cause a significant global health and economic burden. This systematic review aims to investigate the reported economic burden of NTS and iNTS infection, identify research gaps, and suggest future research directions. Data from PubMed and Embase databases up to April 2022 were reviewed, and articles were screened based on predefined criteria. Cost data were extracted, categorized into direct medical costs (DMCs), direct non-medical costs (DNMCs), and indirect costs (ICs), and converted into US dollars (year 2022). Data primarily originated from high-income countries (37 out of 38), with limited representation from Africa and resource-limited settings. For inpatients, DMCs were the primary cost driver for both NTS and iNTS illnesses, with estimates ranging from USD 545.9 (Taiwan, a region of China) to USD 21,179.8 (Türkiye) for NTS and from USD 1973.1 (Taiwan, a region of China) to USD 32,507.5 (United States of America) for iNTS per case. DNMCs and ICs varied widely across studies. Although study quality improved over time, methodological differences persisted. This review underscores the lack of economic data on NTS and iNTS in resource-limited settings. It also highlights the need for economic burden data in resource-limited settings and a standardized approach to generate global datasets, which is critical for informing policy decisions, especially regarding future vaccines.

Regulation of mRNA and miRNA in the response to Salmonella enterica serovar Enteritidis infection in chicken cecum

BACKGROUND

Salmonella enterica, serovar Enteritidis (SE) is a food-borne pathogen, which can cause great threat to human health through consumption of the contaminated poultry products. Chicken is the main host of SE. The mRNA and microRNA (miRNA) expression profiles were analyzed on cecum of Shouguang chicken via next-generation sequencing and bioinformatics approaches. The treated group was inoculated SE, and the control group was inoculated with phosphate buffer saline (PBS).

RESULTS

There were 1760 differentially expressed mRNAs in the SE-infected group, of which 1046 were up-regulated mRNA, and 714 were down-regulated mRNA. In addition, a total of 821 miRNAs were identified, and 174 miRNAs were differentially expressed, of which 100 were up-regulated and 74 were down-regulated. Functional enrichment of differentially expressed mRNAs was similar to miRNA target genes. The functional analysis results of differentially expressed mRNAs and miRNAs were performed. Immune-related processes and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways were enriched by up-regulated mRNA. The down-regulated mRNAs were enriched in tissue development and metabolic-related KEGG pathways. The functional analysis of up-regulated miRNA target genes was similar to the down-regulated mRNAs. The down-regulated miRNA target genes were enriched in metabolic-related GO (Gene Ontology) -BP (Biological process) terms and KEGG pathways. The overlap of the up-regulated mRNA and the up-regulated miRNA target genes (class I) was 325, and the overlap of the down-regulated miRNA target genes (class II) was 169. The class I enriched in the immune-related GO-BP terms and KEGG pathways. The class II mainly enriched in metabolic-related GO-BP terms and KEGG pathways. Then we detected the expression of mRNA and miRNA through qRT-PCR. The results shown that the expression of HHIP, PGM1, HTR2B, ITGB5, RELN, SFRP1, TCF7L2, SCNN1A, NEK7, miR-20b-5p, miR-1662, miR-15a, miR-16-1-3p was significantly different between two groups. Dual-luciferase reporter assay was used to detect the relationship between miR-20b-5p and SCNN1A. The result indicated that miR-20b-5p regulate immune or metabolic responses after SE infection in Shouguang chickens by directly targeting SCNN1A.

CONCLUSIONS

The findings here contribute to the further analysis of the mechanism of mRNA and miRNA defense against SE infection, and provide a theoretical foundation for the molecular disease-resistant breeding of chickens.

Comparison of Antimicrobial Resistance Profiles in Salmonella spp. from Swine Upon Arrival and Postslaughter at the Abattoir

Antimicrobial resistance (AMR) developed by Salmonella within animals used for food products is a major global issue. Monitoring AMR in animals destined for slaughter is, therefore, critical. Abattoirs may serve as potential candidate checkpoints for monitoring resistance patterns on farms. A complicating factor, however, is the impact of lairage on Salmonella detected in pigs at slaughter. This study sought to compare AMR patterns in Salmonella spp. in swine collected upon arrival (fecal samples) at the abattoir with those at postslaughter (cecal samples) and evaluate the feasibility of using slaughterhouse samples for surveillance of prevailing AMR Salmonella on farms. Eighty-four Salmonella isolates were recovered from a large, midwestern U.S. abattoir between September and November 2013. Isolates were tested for phenotypic AMR to 12 antimicrobials using the broth microdilution assay. Whole-genome sequencing identified the AMR genes harbored by the strains. Significant differences were observed in the isolate phenotypes and genotypes; however, no significant difference was observed in genotypic resistance patterns. Hence, the AMR profiles of Salmonella spp. postslaughter cannot be predicted from preslaughter samples. Further research considering the genetic diversity of isolates and statistical power of the genotypic analysis is warranted to improve the performance of WGS-inferred antimicrobial susceptibility.

Changing of the Genomic Pattern of Salmonella Enteritidis Strains Isolated in Brazil Over a 48 year-period revealed by Whole Genome SNP Analyses

Salmonella Enteritidis became the main serovar isolated from gastroenteritis cases in Brazil after the 90's. In this study we used whole genome sequence analysis to determine the phylogenetic relationships among a collection of strains isolated in Brazil to identify possible genomic differences between the strains isolated in the pre and post-epidemic period. Also, we compared our data from strains isolated in Brazil to strains available in the public domain from other South American countries. Illumina technology was used to sequence the genome of 256 Salmonella Enteritidis strains isolated over a 48 year-period in Brazil, comprising the pre- and post-epidemic period. Phylogenetic analyses revealed distinct lineages for strains isolated before and after 1994. Moreover, the phage region SE20 that may be related to the emergence of Salmonella Enteritidis worldwide was present only in strains of the post-epidemic cluster. In conclusion, our results showed that the genomic profile of Salmonella Enteritidis strains isolated in Brazil shifted after 1994, replaced by a global epidemic group of strains. It may be hypothesized that the presence of the prophage SE20 might have conferred to these strains a better ability to colonize chicken and consequently to infect and cause disease in humans, which might better explain the increase in the number of S. Enteritidis cases in Brazil and other South American countries. However, to verify this hypothesis further studies are needed.

Fnr and ArcA Regulate Lipid A Hydroxylation in Salmonella Enteritidis by Controlling lpxO Expression in Response to Oxygen Availability

Lipid A is the bioactive component of lipopolysaccharide, and presents a dynamic structure that undergoes modifications in response to environmental signals. Many of these structural modifications influence Salmonella virulence. This is the case of lipid A hydroxylation, a modification catalyzed by the dioxygenase LpxO. Although it has been established that oxygen is required for lipid A hydroxylation acting as substrate of LpxO in Salmonella, an additional regulatory role for oxygen in lpxO expression has not been described. The existence of this regulation could be relevant considering that Salmonella faces low oxygen tension during infection. This condition leads to an adaptive response by changing the expression of numerous genes, and transcription factors Fnr and ArcA are major regulators of this process. In this work, we describe for the first time that lipid A hydroxylation and lpxO expression are modulated by oxygen availability in Salmonella enterica serovar Enteritidis (S. Enteritidis). Biochemical and genetic analyses indicate that this process is regulated by Fnr and ArcA controlling the expression of lpxO. In addition, according to our results, this regulation occurs by direct binding of both transcription factors to specific elements present in the lpxO promoter region. Altogether, our observations revealed a novel role for oxygen acting as an environment signal controlling lipid A hydroxylation in S. Enteritidis.

Engineering serendipity: High-throughput discovery of materials that resist bacterial attachment

Controlling the colonisation of materials by microorganisms is important in a wide range of industries and clinical settings. To date, the underlying mechanisms that govern the interactions of bacteria with material surfaces remain poorly understood, limiting the ab initio design and engineering of biomaterials to control bacterial attachment. Combinatorial approaches involving high-throughput screening have emerged as key tools for identifying materials to control bacterial attachment. The hundreds of different materials assessed using these methods can be carried out with the aid of computational modelling. This approach can develop an understanding of the rules used to predict bacterial attachment to surfaces of non-toxic synthetic materials. Here we outline our view on the state of this field and the challenges and opportunities in this area for the coming years.

STATEMENT OF SIGNIFICANCE

This opinion article on high throughput screening methods reflects one aspect of how the field of biomaterials research has developed and progressed. The piece takes the reader through key developments in biomaterials discovery, particularly focusing on need to reduce bacterial colonisation of surfaces. Such bacterial resistant surfaces are increasingly required in this age of antibiotic resistance. The influence and origin of high-throughput methods are discussed with insights into the future of biomaterials development where computational methods may drive materials development into new fertile areas of discovery. New biomaterials will exhibit responsiveness to adapt to the biological environment and promote better integration and reduced rejection or infection.

Oral and intranasal administration of somatostatin DNA vaccine mediated by attenuated Salmonella enterica serovar Typhimurium to promote growth of piglets

An attenuated strain of Salmonella typhimurium has been used as a carrier for oral and intranasal genetic immunization. Here, we evaluate the efficacy of a vaccine strain of S. typhimurium. CSO22 (pGM-CSF/SS, plasmid granulocyte-macrophage colony-stimulating factor/somatostatin) expressing two copies of SS genes. A total of 115 piglets, aged 2 months old, were either orally or intranasally immunized against the vaccine strain CSO22 (pGM-CSF/SS) with three dosages (5 × 10(10) colony forming units (CFU), 5 × 10(9) CFU and 5 × 10(8) CFU). For oral immunization, the specific anti-SS antibodies were detected in the immunized piglets. The levels of SS antibodies in the high-dose immunized group (5 × 10(10) CFU) were significantly higher than that in the phosphate buffered saline immunized group (P < 0.01) and 40% of animals were positive in SS antibodies in the high-dose immunized group. Moreover, the weight gain of the high-dose group was increased by 20.86%, 10.26% and 15.30% during 4, 8 and 12 weeks, respectively, after immunization in comparison to the control. For intranasal immunization, the growth of the low-dose group was increased by 10.23% in the whole test period (12 weeks). In conclusion, our results suggest that the recombinant strain could elicit anti-SS antibodies and improve the growth performance of immunized piglets, and that the oral immunization program is better than the intranasal program.

Animal contact as a source of human non-typhoidal salmonellosis

Non-typhoidal Salmonella represents an important human and animal pathogen world-wide. Most human salmonellosis cases are foodborne, but each year infections are also acquired through direct or indirect animal contact in homes, veterinary clinics, zoological gardens, farm environments or other public, professional or private settings. Clinically affected animals may exhibit a higher prevalence of shedding than apparently healthy animals, but both can shed Salmonella over long periods of time. In addition, environmental contamination and indirect transmission through contaminated food and water may complicate control efforts. The public health risk varies by animal species, age group, husbandry practice and health status, and certain human subpopulations are at a heightened risk of infection due to biological or behavioral risk factors. Some serotypes such as Salmonella Dublin are adapted to individual host species, while others, for instance Salmonella Typhimurium, readily infect a broad range of host species, but the potential implications for human health are currently unclear. Basic hygiene practices and the implementation of scientifically based management strategies can efficiently mitigate the risks associated with animal contacts. However, the general public is frequently unaware of the specific disease risks involved, and high-risk behaviors are common. Here we describe the epidemiology and serotype distribution of Salmonella in a variety of host species. In addition, we review our current understanding of the public health risks associated with different types of contacts between humans and animals in public, professional or private settings, and, where appropriate, discuss potential risk mitigation strategies.

[Socioeconomic costs of food-borne disease using the cost-of-illness model: applying the QALY method]

OBJECTIVES

This study estimated the annual socioeconomic costs of food-borne disease in 2008 from a societal perspective and using a cost-of-illness method.

METHODS

Our model employed a comprehensive set of diagnostic disease codes to define food-borne diseases with using the Korea National Health Insurance (KNHI) reimbursement data. This study classified the food borne illness as three types of symptoms according to the severity of the illness: mild, moderate, severe. In addition to the traditional method of assessing the cost-of-illness, the study included measures to account for the lost quality of life. We estimated the cost of the lost quality of life using quality-adjusted life years and a visual analog scale. The direct cost included medical and medication costs, and the non-medical costs included transportation costs, caregiver's cost and administration costs. The lost productivity costs included lost workdays due to illness and lost earnings due to premature death.

RESULTS

The study found the estimated annual socioeconomic costs of food-borne disease in 2008 were 954.9 billion won (735.3 billion won-996.9 billion won). The medical cost was 73.4 - 76.8% of the cost, the lost productivity cost was 22.6% and the cost of the lost quality of life was 26.0%.

CONCLUSIONS

Most of the cost-of-illness studies are known to have underestimated the actual socioeconomic costs of the subjects, and these studies excluded many important social costs, such as the value of pain, suffering and functional disability. The study addressed the uncertainty related to estimating the socioeconomic costs of food-borne disease as well as the updated cost estimates. Our estimates could contribute to develop and evaluate policies for food-borne disease.

Illness and injury presenting to a Norwegian travel insurance company's helpline

INTRODUCTION

Travel abroad is increasing, yet little attention has been paid to the use of health services by specific groups of travellers. This study describes the prevalence of illness, injury and subsequent changes to homeward bound travel and the costs for a group of Norwegian travellers.

METHODS

In 2003, 1787 cases were registered in the data base of the helpline of Norway's largest insurance company. This data were analyzed for prevalence of illness and injury according to age, gender, type of illness or injury, travel destination, type of travel, and the impact on return travel.

RESULTS

Illness and injury accounted for 76.2% and 23.8% of the notifications, respectively. Travellers over the age of 60 accounted for 32.3% of the total number of illnesses. The illness reported most frequently was infection (20.3%), with the highest prevalence of infections occurring in Southern and Eastern Europe (10.2%). The results obtained in this study were compared with studies of other populations of European travellers, revealing that infectious diseases are the most prevalent illness. Differences were noted in the incidence of cardiovascular disease and the destinations where this occurred, and of fatality.

CONCLUSION

The results of this study when compared with those of other European travellers revealed that sufficient difference occurs. As a consequence pre-departure information needs to target better specific population groups with respect to minimizing the risk of illness and injury. As well, the collection of data by the insurance company misses the opportunity of acquiring data of real value for future travellers, the insurance company and the medical profession. It is argued that there is a need to develop a comprehensive data base of greater use than available currently.

Burden and cost of gastroenteritis in a Canadian community

This study estimated the health burden and costs associated with gastroenteritis in the City of Hamilton (Ontario, Canada). The number of cases, number of different resource units used, and cost per resource unit were represented by probability distributions and point estimates. These were subsequently integrated in a stochastic model to estimate the overall burden and cost in the population and to depict the uncertainty of the estimates. The estimated mean annual cost per capita was Can dollar 115. The estimated mean annual cost per case was Can dollar 1,089 and was similar to other published figures. Gastroenteritis represented a significant burden in the study population, with costs high enough to justify prevention efforts. These results, currently the most accurate available estimates for a Canadian population, can inform future economic evaluations to determine the most cost effective measures for reducing the burden and cost of gastroenteritis in the community.

Oral vaccination of BALB/c mice with Salmonella enterica serovar Typhimurium expressing Pseudomonas aeruginosa O antigen promotes increased survival in an acute fatal pneumonia model

Pseudomonas aeruginosa is a leading cause of nosocomial pneumonia. We compared the efficacies of oral and intraperitoneal (i.p.) vaccinations of BALB/c mice with attenuated Salmonella enterica serovar Typhimurium SL3261 expressing P. aeruginosa serogroup O11 O antigen to protect against P. aeruginosa infection in an acute fatal pneumonia model. Oral and i.p. vaccines elicited O11-specific serum immunoglobulin G (IgG) antibodies, but IgA was observed only after oral immunization. Challenge of orally vaccinated mice with an O11 strain (9882-80) at 6 and 12 times the 50% lethal dose showed increased survival in mice that received the vaccine compared to phosphate-buffered saline (PBS)- and vector-treated controls; no difference in survival was seen with a heterologous strain, 6294 (serogroup O6). In addition, significant protection against 9882-80 was not observed in i.p. vaccinated animals. Bronchoalveolar lavage fluid taken from immunized mice harbored O11-specific IgA and IgG in orally immunized mice but only modest levels of IgG in i.p. vaccinated mice. To correlate protection, opsonophagocytosis assays were performed with pooled sera from orally immunized animals. Efficient killing of five O11 clinical isolates was observed, while no killing was noted with 6294, indicating that the recombinant SL3261 oral vaccine induces an O11-specific reaction. We next determined the ability of orally vaccinated animals to clear bacteria from their lungs. Following P. aeruginosa challenge, the numbers of viable bacteria were significantly fewer in orally vaccinated animals than in PBS- and vector-treated controls. Our results suggest that oral immunization with recombinant SL3261 is efficacious in protection against pneumonia caused by P. aeruginosa.

Salmonella enteritidis clearance and immune responses in chickens following Salmonella vaccination and challenge

Our previous work showed that the cell-mediated immunity (CMI) was enhanced by live Salmonella vaccine (LV). The objective of this study was to evaluate the impact of live and killed Salmonella vaccines on Salmonella enteritidis (SE) clearance and to determine if the clearance was mediated by cell-mediated and/or humoral immunity. Chickens were first immunized at 2 weeks of age followed by a booster dose at 4 weeks, challenged with live SE 2 weeks later (6-week-old) and tested for CMI, antibody response and SE clearance 1-week post SE-challenge (7-week-old). Spleen cell proliferation induced by SE-flagella and Concanavalin A (Con A) were significantly higher and SE shedding was significantly lower in the LV group. The splenic CD3 population was significantly lower and B cells were higher in the control group compared to all the SE-challenged groups (with and without vaccination). Serum antibody to SE-flagella and envelope were significantly higher in the KV group compared to all the other groups. These results suggest that LV protects against SE infection, probably by enhancing the CMI.

A description of travel medicine in general practice: a postal questionnaire survey

BACKGROUND

Travel-related diseases are important aspects of public health. The number of UK residents traveling abroad is increasing at a rate of 16% a year, thereby increasing exposure to travel-related morbidity. Provision of comprehensive pretravel health advice is essential to reduce this trend. In the UK, pretravel health advice is predominantly provided through general practices.

METHODS

A postal questionnaire was sent to all 91 general practices in South Cheshire Health Authority. The questionnaires were to be completed by the lead advisor in travel medicine for each practice. Questions were asked on service provision, training and reference resources used, subjects advised on, and health promotion material used. Nonresponders were contacted and sent a further questionnaire.

RESULTS

A response rate of 86% (78/91) was achieved. Of the lead advisors, 97% were nurses and 3% general practitioners. Thirty-eight sources of advice were quoted, the commonest of which comprised wall immunization charts (72%). Duration of consultation ranged from less than 5 min to over 30 min, with a median and mode of 11 to 15 min. Most respondents reported advising on most travel-associated risks, 40% of practices lacked a protocol, and 83% of providers had attended a training course on travel medicine for 2 days or less.

CONCLUSIONS

This survey identified inadequacies of training and use of multiple sources of reference which may lead to inconsistencies in advice. Most practitioners could not define their workload in travel medicine. For effective protection of travelers, a careful risk assessment, clear risk communication and health education with detailed health promotion are necessary, but these are not likely to be provided within an average consultation time of 11 to 15 min. There is no evidence of consistent governance, planned training and monitoring of service quality of travel medicine practice. This may be due to lack of a national policy on best practice and guidance in this subject. National protocols with validated information resources, set standards of training, along with adequate consultation time for educating, advising, and prescribing, will lead to improved health of the traveling public.

Nonimmunized egg yolk powder can suppress the colonization of Salmonella typhimurium, Escherichia coli O157:H7, and Campylobacter jejuni in laying hens

If colonized, poultry shed enteric pathogens in the feces. Of those that colonize poultry Salmonella spp., Campylobacter jejuni (C. jejuni), and Escherichia coli (E. coli) O157:H7 are the most concern to the industry. The authors previously discovered that the introduction of 5% dried nonimmunized egg yolk powder in the regular feed could eliminate and prevent Salmonella enteritidis intestinal colonization of laying hens. Hence, the efficacy of nonimmunized dried egg yolk powder supplement in controlling the colonization of laying hens with Salmonella typhimurium (S. typhimurium), C. jejuni, and E. coli O157:H7 was investigated in this study. The 10% (wt/ wt) egg yolk powder eliminated S. typhimurium after 2 wk of feeding and the 5 and 7.5% (wt/wt) supplements significantly (P < 0.05) reduced the frequency of colonization. Similarly, 7.5 and 10% egg yolk powder reduced the colonization of C. jejuni and E. coli O157:H7 significantly (P < 0.05) after 1 wk of feeding. In the prevention trial, pathogen-free chickens were fed supplemented feed (10% egg yolk powder) for 4 wk and were then infected. S. typhimurium was prevented from colonizing the intestine throughout the 4-wk test, and E. coli O157:H7 colonization was delayed for 2 wk. C. jejuni and E. coli O157:H7 populations in the intestine were significantly (P < 0.05) suppressed by egg yolk powder supplementation throughout the test. None of the supplement concentrations affected BW or the mean weight and number of the eggs laid per hen. At the end of the study, the organisms were absent or significantly (P < 0.05) reduced in the intestine, ovary, oviduct, and spleen of hens fed the egg yolk powder treatment. This study indicates that nonimmunized egg yolk powder is able to reduce the frequency of colonization of foodborne pathogens and prevent these organisms from colonizing the intestinal tract. Addition of egg yolk powder to the regular feed at a concentration of 7.5 to 10% (wt/wt) may be a simple means of reducing or inhibiting S. typhimurium, C. jejuni, and E. coli O157:H7 colonization in laying hens.

Interaction with avian cells and colonisation of specific pathogen free chicks by Shiga-toxin negative Escherichia coli O157:H7 (NCTC 12900)

The prevalence of Escherichia coli O157:H7 infection in birds is low but several deliberate inoculation studies show that poultry are readily and persistently infected by this organism indicating a possible threat to public health. The mechanisms of colonisation of poultry are not understood and the aim is to establish models to study the interaction of E. coli O157:H7, at the cellular and whole animal levels. A non-toxigenic E. coli O157:H7 (NCTC 12900) was used in adherence assays with an avian epithelial cell line (Div-1) and used to inoculate 1-day-old SPF chicks. In vitro, NCTC 12900 induced micro-colonies associated with cytoskeletal arrangements and pedestal formation with intimate bacterial attachment. In the 1-day-old SPF chick, a dose of 1 x 10(5) cfu resulted in rapid and extensive colonisation of the gastrointestinal tract and transient colonisation of the liver and spleen. The number of E. coli O157:H7 organisms attained approximately 10(8) cfu/ml caecal homogenate 24h after inoculation and approximately 10(7) cfu/ml caecal homogenate was still present at day 92. Faecal shedding persisted for 169 days, ceasing 9 days after the birds came into lay and 6% of eggs were contaminated on the eggshell. Histological analysis of tissue samples from birds dosed with 1x10(7) cfu gave evidence for E. coli O157:H7 NCTC 12900 induced micro-colonies on the caecal mucosa, although evidence for attaching effacing lesions was equivocal. These models may be suitable to study those factors of E. coli O157:H7 that mediate persistent colonisation in avian species.

How many foodborne outbreaks of Salmonella infection occurred in France in 1995? Application of the capture-recapture method to three surveillance systems

Despite control measures, foodborne outbreaks of non-typhi Salmonella infection continue to occur in developed countries. The authors aimed to assess the number of foodborne Salmonella outbreaks that occurred in France in 1995 using a capture-recapture approach. Data from three sources--the National Public Health Network (NPHN), the Ministry of Agriculture (MA), which receives mandatory notification, and the National Salmonella and Shigella Reference Center (NRC)-were collected. Matching algorithms permitted identification of matched outbreaks. The total number of outbreaks was estimated by log-linear modeling taking into account source dependencies and the variable catchability. The final estimate was adjusted for the positive predictive value (66%) of the NRC case definition. The dependence between the NPHN and the MA was also evaluated by means of a qualitative survey. A total of 716 foodborne Salmonella outbreaks were reported to the three sources, and 108 matches were identified. The best-fitting model, taking into account a positive dependence between the NPHN and MA sources, gave an estimate of 757 outbreaks. The sensitivity was 15% for the NPHN, 10% for the MA, and 50% for the NRC. In France, routine mandatory reporting of foodborne Salmonella outbreaks is very incomplete, and it is not representative of the serotype and the type of outbreak.

Direct costs associated with a nosocomial outbreak of Salmonella infection: an ounce of prevention is worth a pound of cure

BACKGROUND

Nosocomial outbreaks of Salmonella infections in Australia are an infrequent but significant source of morbidity and mortality. Such an outbreak results in direct, measurable expenses for acute care management, as well as numerous indirect (and less quantifiable) costs to those affected, the hospital, and the wider community. This article describes the significant direct costs incurred as a result of a nosocomial outbreak of Salmonella infection involving patients and staff.

METHOD

Information on costs incurred by the hospital was gathered from a number of sources. The data were grouped into 4 sections (medical costs, investigative costs, lost productivity costs, and miscellaneous) with use of an existing tool for calculating the economic impact of foodborne illness.

RESULTS

The outbreak cost the hospital more than AU $120, 000. (US $95,000). This amount is independent of more substantial indirect costs.

CONCLUSION

Salmonella infections are preventable. Measures to aid the prevention of costly outbreaks of nosocomial salmonellosis, although available, require an investment of both time and money. We suggest that dedication of limited resources toward such preventive strategies as education is a practical and cost-effective option for health care facilities.

Prevention of Salmonella typhimurium caecal colonisation by different preparations for competitive exclusion

The number of Salmonella typhimurium per gram of caecal contents of chicks, given orally prior to infection with different preparations containing protective intestinal flora, was significantly lower than in the control group. The best results were obtained when the lyophilised caecal rinses were given orally to 1-day-old chicks. Less effective methods of protection of the alimentary tract proved to be oral application to chicks of fresh faeces or lyophilised faeces and administration of the lyophilised caecal rinses with drinking water. Oral application of undefined anaerobic caecal culture to chicks proved to be the least effective of the methods investigated of protecting them against Salmonella colonisation, although even these results differed statistically from those of the controls. The percentage of infected birds 7 days after challenge confirmed the efficacy of oral application of lyophilised caecal rinses--only 30% of individuals from the group treated in this way proved to be Salmonella positive. In contrast, the percentage of infected birds in other experimental groups ranged from 50% to 75% and was 100% in the controls.

Application of random amplified polymorphic DNA analysis to differentiate strains of Salmonella enteritidis

A random amplified polymorphic DNA (RAPD) fingerprinting method has been developed to differentiate Salmonella enteritidis isolates. A total of 65 arbitrary primers were screened with S. enteritidis isolates of different phage types. This allowed selection of a panel of primers capable of detecting DNA polymorphisms among S. enteritidis isolates. This panel was used to examine a panel of 29 isolates of S. enteritidis which had been previously characterized by other subtyping methods, including phage typing (PT) (n = 7), ribotyping (RT) (n = 13), and pulsed-field gel electrophoresis (PFGE). Applied collectively, these three methods resolved the collection into 20 different subtypes. However, by the RAPD fingerprinting method alone, 14 RAPD subtypes were revealed. Eight isolates of S. enteritidis phage type 8 that failed to be discriminated by other typing methods (PT, RT, and PFGE) were resolved into three different subtypes by RAPD analysis. In contrast, isolates that were derived from the same sources were not differentiated by any of the subtyping methods employed, including PT, RT, PFGE, and RAPD analysis. This RAPD approach to S. enteritidis subtyping provided more discriminatory power than did any of several other subtyping methods applied individually. Once the challenging step of primer identification was accomplished, determinations of the appropriate concentrations of arbitrary primer, DNA template, and MG2+ ion were also necessary for optimal discriminatory power. The bacterial DNA used in this RAPD protocol was obtained by boiling the bacterial sample. This simple procedure yielded DNA that produced fingerprint patterns as consistent as those obtained from phenol-chloroform-extracted DNA. Clearly, when appropriately constituted primer sets are identified and employed, RAPD analysis provides a simple, rapid, and powerful subtyping method for S. enteritidis.