The distribution of Staphylococcus sp. on bovine meat from abattoir deboning rooms

Epidemiology and antimicrobial resistance of staphylococci other than Staphylococcus aureus from domestic animals and livestock in Africa: a systematic review

Introduction

Staphylococci other than Staphylococcus aureus (SOSA) in animals are becoming more pathogenic and antibiotic resistant and can potentially disseminate to humans. However, there is little synthesized information regarding SOSA from animals in Africa. This systematic review provides a comprehensive overview of the epidemiology and antimicrobial resistance of SOSA in companion animals (pets) and livestock in Africa.

Method

This systematic review (PROSPERO-CRD42021252303) was conducted according to the PRISMA guidelines, and 75 eligible studies from 13 countries were identified until August 2022. Three electronic databases (Pubmed, Scopus and Web of Science) were employed.

Results

The frequently isolated SOSA were S. epidermidis, S. intermedius, S. pseudintermedius, S. xylosus, S. chromogenes, S. hyicus, M. sciuri, S. hominis, and S. haemolyticus. Thirty (40%) studies performed antibiotic susceptibility testing (AST). Penicillin (58%) and tetracycline (28%) resistance were most common across all SOSA with high rates of resistance to aminoglycosides, fluoroquinolones, and macrolides in some species. Resistance to last-resort antibiotics such as linezolid and fusidic acid were also reported. Limited data on strain typing and molecular resistance mechanisms precluded analysis of the clonal diversity of SOSA on the continent.

Conclusion

The findings of this review indicate that research on livestock-associated SOSA in Africa is lacking in some regions such as Central and Western Africa, furthermore, research on companion animals and more advanced methods for identification and strain typing of SOSA need to be encouraged.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier: CRD42021252303.

Development of two specific multiplex qPCRs to determine amounts of Pseudomonas, Enterobacteriaceae, Brochothrix thermosphacta and Staphylococcus in meat and heat-treated meat products

Culturing methods are conventionally applied to investigate the contamination of food with several microorganisms after heat processing. However, with these methods, it is not possible to evaluate whether heat-treated meat products, such as cooked sausages, contained parts of spoiled meat. Therefore, two specific multiplex qPCRs were developed in this study in order to determine the microbiological quality of the raw materials used for these products. The PCR targets focused on four bacterial groups often found on meat (family Enterobacteriaceae, genus Pseudomonas, genus Staphylococcus and species Brochothrix thermosphacta). Specificity as well as sensitivity of the developed multiplex qPCRs, validated by using 68 microbial species, were 100%. The applicability of both multiplex qPCRs compared to culturing methods was performed using 96 meat samples (fresh and naturally spoiled) and 12 inhouse-made "Lyoner" sausages containing variable ratios of spoiled meat (0%, 5%, 12% and 25%; n = 3 for each group). Both methods showed similar results by evaluating the ∆log₁₀ cfu/g, the relative accuracy and the t-test analysis (p > 0.05). Comparing qPCR results of the different sausage groups, a significant difference between sausages containing fresh meat and sausages containing spoiled meat (12% and 25%) was found only for Pseudomonas and B. thermosphacta in both raw and cooked sausages. The statistical difference between 5% vs. 12% and 25% spoiled meat in cooked sausages, was also found only for these two bacterial groups. The developed multiplex qPCRs were further applied to 30 commercially available "Bologna-type" sausages. The results showed a total of 14 sausages considered to be suspicious for Food Fraud. While the role of Staphylococcus spp. in meat spoilage remains unclear, Pseudomonas, Enterobacteriaceae and B. thermosphacta could together be used as an indicator for "spoiled meat" used in sausages. The developed qPCR systems in this study allow the detection of four relevant bacterial groups in the heated Bologna-type sausages and provide information about the hygienic quality of raw materials used. This method could thus be helpful for screening food suspected of Food Fraud.

Changes in the composition and architecture of staphylococcal biofilm by nisin

Bacterial biofilms are involved in various medical infections and food contamination episodes and, for this reason, it is of great importance to developing new strategies of its prevention and control. The subinhibitory concentration of nisin was determined, and its effect against Staphylococcus aureus and Staphylococcus epidermidis biofilms was evaluated. Results obtained by confocal laser microscopy demonstrated morphological changes in the architecture of the structure of biofilms. The main components (polysaccharides, proteins, and extracellular DNA (eDNA)) of the biofilm matrix were determined by spectrophotometry and showed that the formation of staphylococcal biofilms in the presence of nisin results in a less dense matrix structure with modification in its constituents. These results contribute to increase the knowledge of the composition and architecture of the extracellular matrix of biofilms of S. aureus, as well as evidence that the investigation of alternative products to assist in the control and combat of biofilms is a promising strategy.

Species Pervasiveness Within the Group of Coagulase-Negative Staphylococci Associated With Meat Fermentation Is Modulated by pH

During spontaneous meat fermentations, Staphylococcus equorum, Staphylococcus saprophyticus, and Staphylococcus xylosus are generally the most prevailing species within the communities of coagulase-negative staphylococci (CNS). There is an interest to introduce CNS isolates from artisan-style spontaneous meat fermentations as starter cultures in more industrialized processes, as to confer additional quality benefits. However, staphylococcal competitiveness within the meat matrix is affected by the processing conditions, which vary considerably among product types. A major factor of variability relates to the intensity of acidification, driven by the concentration of added carbohydrates. The effect of pH on CNS prevalence was studied in both a mince-based meat fermentation model and in fermented sausages produced on pilot scale. Roughly, from all experiments combined, it appeared that a pH of 5.3 corresponded with a breakpoint for CNS selection. Above this value, a general prevalence by S. xylosus was found, even overruling the addition of starter cultures consisting of S. equorum and S. saprophyticus strains. At pH values below 5.3, S. xylosus was also accompanied by S. equorum (following a mild pH drop) and S. saprophyticus (following a stronger pH drop). Still, addition of starter cultures affected the volatile profile compared to the control batch, even if those starter cultures were not able to dominate during the ripening process. This study nonetheless provides a warning for an overly confident use of specific CNS species as starter cultures, especially when in a given processing context the prevailing conditions do not allow superior growth compared to the CNS from the background microbiota.

Trichoderma asperelloides ethanolic extracts efficiently inhibit Staphylococcus growth and biofilm formation

Fungi from the widely distributed genus Trichoderma are of great biotechnological interest, being currently used in a vast range of applications. Here, we report that high-molecular weight fraction (HWF) derived from Trichoderma asperelloides ethanolic extract exhibits antibiotic activity against staphylococcal biofilms. The antibacterial and anti-biofilm properties of T. asperelloides extracts were evaluated by well-established assays in Staphylococcus aureus ATCC strains (29213 and 6538) and in one clinical isolate from bovine mastitis. The HWF from T. asperelloides eradicated S. aureus by causing substantial matrix de-structuring and biomass reduction (p < 10-5) at concentrations as low as 2.3 μg mL-1. Additionally, we present ultra-structure analysis by the use of scanning electron microscopy as well as transmission microscopy, which showed that T. asperelloides killed cells through cell wall and membrane disturbance. Remarkably, the HWF from T. asperelloides killed S. aureus and eradicated its biofilms in a greater performance than gentamicin (p < 10-5), a known potent antibiotic against S. aureus. Our results indicate that extract from T. asperelloides may represent a promising candidate for the development of new antibiotics against gram-positive bacteria.

Food safety management systems performance in African food processing companies: a review of deficiencies and possible improvement strategies

This study seeks to provide insight into current deficiencies in food safety management systems (FSMS) in African food-processing companies and to identify possible strategies for improvement so as to contribute to African countries' efforts to provide safe food to both local and international markets. This study found that most African food products had high microbiological and chemical contamination levels exceeding the set (legal) limits. Relative to industrialized countries, the study identified various deficiencies at government, sector/branch, retail and company levels which affect performance of FSMS in Africa. For instance, very few companies (except exporting and large companies) have implemented HACCP and ISO 22000:2005. Various measures were proposed to be taken at government (e.g. construction of risk-based legislative frameworks, strengthening of food safety authorities, recommend use of ISO 22000:2005, and consumers' food safety training), branch/sector (e.g. sector-specific guidelines and third-party certification), retail (develop stringent certification standards and impose product specifications) and company levels (improving hygiene, strict raw material control, production process efficacy, and enhancing monitoring systems, assurance activities and supportive administrative structures). By working on those four levels, FSMS of African food-processing companies could be better designed and tailored towards their production processes and specific needs to ensure food safety.

A negative role for MyD88 in the resistance to starvation as revealed in an intestinal infection of Drosophila melanogaster with the Gram-positive bacterium Staphylococcus xylosus

Drosophila melanogaster is a useful model to investigate mucosal immunity. The immune response to intestinal infections is mediated partly by the Immune deficiency (IMD) pathway, which only gets activated by a type of peptidoglycan lacking in several medically important Gram-positive bacterial species such as Staphylococcus. Thus, the intestinal host defense against such bacterial strains remains poorly known. Here, we have used Staphylococcus xylosus to develop a model of intestinal infections by Gram-positive bacteria. S. xylosus behaves as an opportunistic pathogen in a septic injury model, being able to kill only flies immunodeficient either for the Toll pathway or the cellular response. When ingested, it is controlled by IMD-independent host intestinal defenses, yet flies eventually die. Having excluded an overreaction of the immune response and the action of toxins, we find that flies actually succumb to starvation, likely as a result of a competition for sucrose between the bacteria and the flies. Fat stores of wild-type flies are severely reduced within a day, a period when sucrose is not yet exhausted in the feeding solution. Interestingly, the Toll pathway mutant MyD88 is more resistant to the ingestion of S. xylosus and to starvation than wild-type flies. MyD88 flies do not rapidly deplete their fat stores when starved, in contrast to wild-type flies. Thus, we have uncovered a novel function of MyD88 in the regulation of metabolism that appears to be independent of its known roles in immunity and development.

Safety-related properties of staphylococci isolated from food and food environments

AIMS

To test some safety-related properties within 321 staphylococci strains isolated from food and food environments.

METHODS AND RESULTS

The isolates were identified as Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus saprophyticus, Staphylococcus pasteuri, Staphylococcus sciuri, Staphylococcus warneri and Staphylococcus xylosus. Decarboxylase activity was quite common for the various Staphylococcus spp., and tyrosine was the most frequently decarboxylated amino acid. The frequency of antibiotic resistance was highest in Staph. pasteuri and Staph. xylosus. Several of the isolates were tolerant to QAC compounds, and in some cases, QAC tolerance was present in antibiotic-resistant strains. Most of the strains displayed moderate to high adhesion rates to stainless steel and Teflon(®). The strains that readily formed biofilms belonged to the species Staph. aureus, Staph. epidermidis and Staph. pasteuri.

CONCLUSIONS

An high incidence of some safety hazards was found within the staphylococcal strains of food origin tested in this study. In particular, amino acid decarboxylase activity and biofilm-forming ability were common within strains, and antibiotic resistance and tolerance to QAC-based compounds occurred frequently as well. These characteristics are an important safety concern for food industry.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work gives a first picture of safety hazards within staphylococcal species isolated from food environments. The presence of disinfectant-resistant staphylococci is a concern because resistance can be genetically transferred between the various Staphylococcus species. This could lead an increase and spread of resistant enterotoxic staphylococci and/or pathogenic staphylococci.

Genomic diversity in Staphylococcus xylosus

Staphylococcus xylosus is a commensal of the skin of humans and animals and a ubiquitous bacterium naturally present in food. It is one of the major starter cultures used for meat fermentation, but a few strains could potentially be hazardous and are related to animal opportunistic infections. To better understand the genetic diversity of S. xylosus intraspecies, suppressive and subtractive hybridization (SSH) was carried out with the S. xylosus C2a strain, a commensal of human skin, used as the driver for three tester strains, S04002 used as a starter culture, S04009 isolated from cow mastitis, and 00-1747, responsible for mouse dermatitis. SSH revealed 122 tester-specific fragments corresponding to 149 open reading frames (ORFs). A large proportion of these ORFs resembled genes involved in specific metabolisms. Analysis of the distribution of the tester-specific fragments in 20 S. xylosus strains of various origins showed that the S. xylosus species could be divided into two clusters with one composed only of potentially hazardous strains. The genetic content diversity of this species is colocalized in a region near the origin of replication of the chromosome. This region of speciation previously observed in the Staphylococcus genus corresponded in S. xylosus species to a strain-specific region potentially implicated in ecological fitness.

The impact of extrinsic sources on selected indicator organisms in a typical deboning room

Meat is a highly perishable product and the microbiological safety thereof is an extremely important issue for both the consumer and the meat industry. In this study, samples were randomly collected from various working surfaces, from raw meat and from the air in the deboning room of a high throughput red meat abattoir. The samples were analysed for the presence of total staphylococci counts as well as for total viable counts. The mean staphylococci counts from working surfaces were 19 CFU x cm(-2), and the staphylococci levels for the meat samples were well below the proposed maximum limit of 100 CFU x g(-1). Maximum staphylococcal bioaerosol counts of 10 CFU x m(-3) were also enumerated. Total viable counts from the workers' hands and working surfaces were high compared to the staphylococcal levels. Twelve staphylococci species were identified from the samples used in this study. Recontamination during the deboning process was identified as the major source of contamination, suggesting proper implementation of quality processing practices within the abattoir environment.