Purpose of Review
In this article, we aim to provide an overview of the occurrence and characteristics of livestock-associated (LA-) meticillin-resistant
Staphylococcus aureus
(MRSA). We further ...question the role of LA-MRSA as a potential foodborne pathogen. We investigate recent findings and developments from a One Health perspective also highlighting current strategies and initiatives aiming to improve reporting, control, and prevention of LA-MRSA.
Recent Findings
While the overall number of invasive MRSA infections in humans is decreasing (in most European countries and the USA) or steadily increasing (in the Asia-Pacific region), the role of LA-MRSA as causative agent of invasive disease and as potential foodborne pathogen is still poorly understood. LA-MRSA prevalence in livestock remains high in many geographical regions and the acquisition of new virulence and resistance determinants constitutes a growing threat for human health.
Summary
The true incidence of LA-MRSA infections due to occupational exposure is unknown. Improved MRSA monitoring and tracking procedures are urgently needed. Strain typing is crucial to enable improved understanding of the impact of LA-MRSA on human and animal health.
In recent years, several quantitative risk assessments for
Campylobacter in broiler meat have been developed to support risk managers in controlling this pathogen. The models encompass some or all of ...the consecutive stages in the broiler meat production chain: primary production, industrial processing, consumer food preparation, and the dose–response relationship. The modelling approaches vary between the models, and this has supported the progress of risk assessment as a research discipline. The risk assessments are not only used to assess the human incidence of campylobacteriosis due to contaminated broiler meat, but more importantly for analyses of the effects of control measures at different stages in the broiler meat production chain.
This review paper provides a comparative overview of models developed in the United Kingdom, Denmark, the Netherlands and Germany, and aims to identify differences and similarities of these existing models. Risk assessments developed for FAO/WHO and in New Zealand are also briefly discussed.
Although the dynamics of the existing models may differ substantially, there are some similar conclusions shared between all models. The continuous introduction of
Campylobacter in flocks implies that monitoring for
Campylobacter at the farm up to one week before slaughter may result in flocks that are falsely tested negative: once
Campylobacter is established at the farm, the within-flock prevalence increases dramatically within a week. Consequently, at the point of slaughter, the prevalence is most likely to be either very low (<
5%) or very high (>
95%). In evaluating control strategies, all models find a negligible effect of logistic slaughter, the separate processing of positive and negative flocks. Also, all risk assessments conclude that the most effective intervention measures aim at reducing the
Campylobacter concentration, rather than reducing the prevalence. During the stage where the consumer handles the food, cross-contamination is generally considered to be more relevant than undercooking. An important finding, shared by all, is that the tails of the distributions describing the variability in
Campylobacter concentrations between meat products and meals determine the risks, not the mean values of those distributions.
Although a unified model for risk assessment of
Campylobacter in the broiler meat production would be desirable in order to promote a European harmonized approach, it is neither feasible nor desirable to merge the different models into one generic risk assessment model. The purpose of such a generic model has yet to be defined at a European level and the large variety in practices between countries, especially related to consumer food preparation and consumption, complicates a unified approach.
•5.4% and 1.1% prevalence of MSSA and MRSA respectively.•19 different spa types were detected including a novel type (t16571).•Low risk perception and poor hygiene practices employed by abattoir ...workers in the study areas.•Formal education and occupation were associated with S. aureus knowledge levels.•Several risk factors predispose abattoir workers to bacterial colonization.
Staphylococcus aureus is a zoonotic pathogen of significant public health concern. Information on the prevalence and risk factors facilitating bacterial colonization and spread under abattoir settings in Nigeria are scarce. This cross-sectional study was designed to determine prevalence of S. aureus as well as risk factors on knowledge and practices facilitating pathogen carriage among workers and slaughter animals in two municipal abattoirs of Ilorin and Ibadan, Nigeria. Swab samples (n = 1671) from nostrils of cattle, goats, pigs and abattoir workers, and from meat tables and abattoir walls were collected for detection of S. aureus. A questionnaire was administered to 275 workers to elucidate risk factors of pathogen carriage applying a logistic regression model. S. aureus prevalence was 6.5%. In total, MSSA and MRSA were detected at a frequency of 5.4% and 1.1%. Molecular analysis of the isolates revealed 19 different spa types, including a novel spa type (t16751). Gender, marital status, occupation and abattoir location were factors influencing worker’s practices in relation to pathogen carriage and spread in the abattoir setting. This present study detected not only low MSSA and MRSA prevalence, in both abattoirs but also low risk perception and hygiene practices employed by abattoir workers. Good practices among workers at Nigerian abattoirs are needed to mitigate S. aureus carriage. Further studies expounding the antibiotic resistance and relationships of MSSA and MRSA strains detected in this study are needed to complement understanding of the spread of S. aureus in the abattoir food chain.
Staphylococcus aureus MRSA strains belonging to the clonal complex 398 (CC398) are highly prevalent in livestock and companion animals but may also cause serious infections in humans. CC398 strains ...in livestock usually do not possess well-known virulence factors that can be frequently found in other MRSA sequence types (ST). Since many staphylococcal virulence genes are residing on the genomes of temperate phages, the question arises why livestock-associated (LA-) CC398 strains are only rarely infected by those phages. We isolated and characterized four temperate phages (P240, P282, P630 and P1105) containing genes of the immune evasion cluster (IEC) and/or for the Panton-Valentine leucocidin (PVL). Sequence analysis of the phage genomes showed that they are closely related to known phages and that the DNA region encoding lysis proteins, virulence factors and the integrase exhibits numerous DNA repeats which may facilitate genomic rearrangements. All phages lysed and lysogenized LA-CC398 strains. Integration of IEC phage P282 was detected at ten sites of the hosts' chromosome. The prophages were stably inherited in LA-CC398 and enterotoxin A, staphylokinase and PVL toxin were produced. The data demonstrate that lysogenic conversion of LA-CC398 strains by virulence-associated phages may occur and that new pathotypes may emerge by this mechanism.
The prevalence of MRSA in the turkey meat production chain in Germany was estimated within the national monitoring for zoonotic agents in 2010. In total 22/112 (19.6%) dust samples from turkey farms, ...235/359 (65.5%) swabs from turkey carcasses after slaughter and 147/460 (32.0%) turkey meat samples at retail were tested positive for MRSA. The specific distributions of spa types, SCCmec types and antimicrobial resistance profiles of MRSA isolated from these three different origins were compared using chi square statistics and the proportional similarity index (Czekanowski index). No significant differences between spa types, SCCmec types and antimicrobial resistance profiles of MRSA from different steps of the German turkey meat production chain were observed using Chi-Square test statistics. The Czekanowski index which can obtain values between 0 (no similarity) and 1 (perfect agreement) was consistently high (0.79-0.86) for the distribution of spa types and SCCmec types between the different processing stages indicating high degrees of similarity. The comparison of antimicrobial resistance profiles between the different process steps revealed the lowest Czekanowski index values (0.42-0.56). However, the Czekanowski index values were substantially higher than the index when isolates from the turkey meat production chain were compared to isolates from wild boar meat (0.13-0.19), an example of a separated population of MRSA used as control group. This result indicates that the proposed statistical method is valid to detect existing differences in the distribution of the tested characteristics of MRSA. The degree of similarity in the distribution of spa types, SCCmec types and antimicrobial resistance profiles between MRSA isolates from different process stages of turkey meat production may reflect MRSA transmission along the chain.
Purpose of Review
We present recent insights on
S. aureus
as a foodborne pathogen, thus providing readers with an update of current findings impacting prevention and control measures.
Recent Findings
...Advances in disease burden assessment show the burden of
S. aureus
foodborne disease around the globe. In recent years, recent research has provided valuable new data improving the understanding of the pathobiology of
S. aureus
foodborne disease as well as proteomics and genomics of this foodborne pathogen. In particular, recent findings shed new light on the role of newly described enterotoxins and methicillin-resistant
S. aureus
. These new findings guide the way towards improved prevention and control strategies.
Summary
S. aureus
is the leading cause of foodborne intoxications worldwide. Control strategies are focused on hygiene measures to avoid food contamination and limit
S. aureus
growth. Outbreak investigations remain challenging and would strongly benefit from additional data on enterotoxin formation under stress conditions and novel tools allowing for detection of newly described enterotoxins.
Abstract Background Staphylococcus aureus (S. aureus) is a bacterium of public health importance. The zoonotic spread of this pathogen through animal-derived foods has been reported. This systematic ...literature review investigates the prevalence, distribution, antimicrobial resistance (AMR) profiles, and molecular characteristics of S. aureus in the food chain in Nigeria. Methods A systematic search of online databases (Pub Med, Google Scholar, and Web of Science) for published articles from January 2002 to January 2022 was performed using the Prisma guideline. Results Fifty articles were included from an initial 511 extracted documents. These papers included research carried out in 22 states across Nigeria. S. aureus detection in most studies was above the satisfactory level for foods (≥ 104 CFU/g). The prevalence of S. aureus ranged from 1.3% in raw cow meat to 72.5% in fresh poultry meat. Most S. aureus isolates demonstrated multiple drug resistance patterns, especially being resistant to beta-lactams. There is a lack of information on the molecular typing of the S. aureus isolates. The different spa types of S. aureus isolated were t091, t314, t1476, and t4690, categorized into Multi-Locus-Sequence Types ST8, ST121, ST152, and ST789. Virulence genes detected include pvl, sea, see, spa, coa, edin, tsst, and hly. Certain AMR-encoding genes were detected, such as mecA, blaZ, fos, tet, and dfsr.. Factors contributing to the presence of S. aureus were reported as poor processing, poor sanitary conditions of the food processing units, inadequate storage units, and poor handling. Conclusion We showed that S. aureus is a major food contaminant in Nigeria despite the need for more information on the molecular typing of strains from animal-derived food sources. There is a need to control S. aureus by targeting specific entry points based on the findings on risk factors and drivers of food contamination.
Staphylococcus aureus is an important food-borne pathogen due to the ability of enterotoxigenic strains to produce staphylococcal enterotoxins (SEs) in food. Methicillin-resistant S. aureus (MRSA) is ...also an important pathogen for humans, causing severe and hard to treat diseases in hospitals and in the community due to its multiresistance against antimicrobials. In particular, strains harbouring genes encoding for the Panton–Valentine leukocidin (PVL) toxin are of concern from a public health perspective as they are usually capable of causing severe skin and soft tissue infections (sSSTIs) and occasionally necrotizing pneumonia which is associated with high mortality. This is the first report on the detection of MRSA with genes encoding for PVL in wild boar meat. Among the 28 MRSA isolated from wild boar meat in the course of a national monitoring programme in Germany, seven harboured PVL-encoding genes. Six of the isolates were identical according to the results of spa-, MLST-, microarray- and PFGE-typing. They could be assigned to the epidemic MRSA clone USA300. Epidemiological investigations revealed that people handling the food were the most likely common source of contamination with these MRSA. These findings call again for suitable hygienic measures at all processing steps of the food production chain. The results of the study underline that monitoring along the food chain is essential to closely characterise the total burden of MRSA for public health.
•First report on the occurrence of PVL-positive MRSA in wild boar meat samples•Seven out of 28 MRSA strains carried the PVL genes.•Six almost identical PVL strains (USA300) could be epidemiologically linked.•A common entry path could not be clearly identified.•Humans are the most likely source of contamination.
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