Salmonella : une bactérie multi-résistante aux antibiotiques dans nos assiettes

Prevalence and genomic investigation of Salmonella isolates recovered from animal food-chain in Xinjiang, China

Salmonella is a major foodborne pathogen worldwide, causing serious cases of morbidity and mortality due to the consumption of contaminated foods. Animal-borne foods were considered the main source of transferring Salmonella to humans; however, route surveillance by genomic platforms along the food-chain is limited in China. Here, we proceeded to the application of whole genome sequencing in the epidemiological analysis of Salmonella isolated along the food-chain in Xinjiang, China. A total of 2408 samples were collected from farms, slaughterhouses, and markets, and subjected to the isolation of Salmonella strains. 314 (13.04%) of the samples were positive for Salmonella. Phenotypic antimicrobial resistance was conducted by the broth dilution method using 14 antimicrobial agents belonging to ten classes for all 314 isolates. A selection of representative 103 isolates was subjected to whole-genome sequencing for understanding the Salmonella diversity, including serovars, antimicrobial and virulence genes, plasmid types, multi-locus sequence types, and allelic types. We found that S. Agona was the dominant serovar and O:4(B) was the dominant serogroup. The dominant genotype was ST13 and each serovar has a unique MLST pattern. Plasmids prediction reported Col(MGD2)_1 and Col(Ye4449)_1 as the dominant plasmids, in addition to the detection of IncFII(S)_1 and IncFIB(S)_1 carried by all S. Enteritidis isolates. Importantly, virulence genes prediction showed the presence of cdtB gene encoding typhoid toxins, spv genes, and pef gene cluster encoding fimbriae in the genomes of S. Indiana and S. Enteritidis. Phenotypic antimicrobial resistance identified 92.04% of the sampled isolates as multi-drug resistance (MDR), with high resistance to tetracycline (78.03%; 245/314), amoxicillin/ clavulanic acid (75.80%; 238/314), and ampicillin (70.70%; 222/314). Together, we firstly reported the prevalence of MDR Salmonella isolates harboring critical virulence factors transmission via animal-borne food-chain in Xinjiang, hence route surveillance by whole-genome sequencing platform could facilitate recognition and project early warning for the emerging MDR clones along the food-chain.

Chemical Composition and Antimicrobial Activity of the Essential Oils of Two Aromatic Plants Cultivated in Morocco (Cinnamomum cassia and Origanum compactum)

The present study aims to evaluate the antibacterial properties of natural products according to a pharmacodynamic approach in order to propose them as alternatives to synthetic products. Two essential oils (Cinnamomum cassia and Origanum compactum) were the subject of the chemical and biological study. First, we evaluated the sensitivity of the strains of avian Salmonella to the main antibiotics used and then to the chromatographic analysis of the composition of the two essential oils (EO); finally, we proceeded to the in vitro evaluation of the antibacterial activities of these EO (alone and in combination with antibiotics). The results obtained showed that carvacrol (35.2%), followed by γ-terpinene (20.1%), was the main constituent of the essential oil of O. compactum while cinnamaldehyde (69.1%) represents the major component of the essential oil of C. cassia. The antibioresistance profile of the Salmonella tested showed resistance to ampicillin (35%) and oxytetracycline (41.3%). Active products extracted from the essential oils studied showed antibacterial activity against Salmonella strains. C. cassia products were shown to be more active for Salmonella enteritidis (average inhibition diameter: 16.3 mm) and for Salmonella gallinarum (average inhibition diameter: 27.7 mm). The best synergistic activity with antibiotics has been obtained with the essential oil of C. cassia and its active product cinnamaldehyde. The minimum inhibitory concentration (MIC) of cinnamaldehyde is the lowest (0.05%). The results prove the presence of an antibacterial activity and a synergistic effect of two essential oils studied with the main antibiotics.

Antimicrobial resistance and genetic diversity of Salmonella Infantis isolated from foods and human samples in Morocco

OBJECTIVES

Genotyping of Salmonella strains is an important molecular tool to discriminate isolates and to improve epidemiological studies when an outbreak occurs. Among the DNA-based genotyping methods, pulsed-field gel electrophoresis (PFGE) is currently used to subtype Salmonella isolates. In this study, the feasibility of genotyping Salmonella enterica serotype Infantis strains using XbaI restriction enzyme was evaluated. Separation of restricted fragments was performed by PFGE.

METHODS

To test the possibility of applying this methodology to epidemiological investigation, a collection of 26 Salmonella Infantis strains were tested for their susceptibility to 14 antimicrobial agents and were analysed by XbaI macrorestriction followed by PFGE. Detection of class 1 integrons as well as intI1 and bla_TEM genes in resistant strains was also studied.

RESULTS

Antimicrobial susceptibility testing showed that 84.6% (22/26) of Salmonella Infantis isolates were susceptible to all of the antimicrobials tested, whereas 7.7% (2/26) had low-level resistance to β-lactams and harboured the bla_TEM gene. A class 1 integron (0.8kb) and the intI1 gene (898bp) were detected in one Salmonella Infantis strain. However, five different PFGE profiles were defined by XbaI macrorestriction.

CONCLUSIONS

The PFGE method demonstrated adequate typing ability and represents a powerful tool to discriminate the serotype Salmonella Infantis.

Prevalence, molecular and antimicrobial resistance of Salmonella isolated from sausages in Meknes, Morocco

Salmonella is among the most important food borne pathogens worldwide contaminating a wide range of animal products including meat products. The aims of this study go through two steps: The first step is to estimate the proportion of sausages products contaminated with Salmonella in Meknes city (Morocco), which were collected from various shopping sites: butchery, street vendors, supermarket and souk (Weekly market combines the population of the small villages around Meknes city). The second one is to identify serovars, to determine the antimicrobials resistance patterns of isolates and to detect the invA and spvC genes. 34 (21.79%) Salmonella were isolated, recovered 4 serogroups and 12 serotypes. The most prevalent serotypes were Salmonella Corvallis (23.53%) and Salmonella Kentucky (17.65%). All Salmonella isolates were tested for their susceptibility to 18 selected antimicrobials agents, of which 100% were resistant to at least one antimicrobial, 85.30% (29/34) were resistant to two or more antimicrobials and 44.12% (15/34) were resistant to at least three antimicrobials. All Salmonella are resistant to ampicillin, 76.47% to streptomycin, 20.59% to sulfonamides, 17.65% to Tetracycline and 11.77% to Ofloxacin. The "ACSSuT" penta-resistance pattern was observed in tow of the Salmonella Typhimurium strains. In addition, this study showed that all Salmonella strains (34) were positive for invasion gene invA and negative for the virulence gene spvC.