Colistin Resistance Mechanism in Enterobacter hormaechei subsp. steigerwaltii Isolated from Wild Boar (Sus scrofa) in France.

Wild animals may act as efficient antimicrobial-resistance reservoirs and epidemiological links between humans, livestock, and natural environments. By using phenotypic and genotypic characterization, the present study highlighted the occurrence of an antimicrobial-resistant (i.e., amoxicillin, amoxicillin-clavulanic acid, cephalothin, and colistin) Enterobacter hormaechei subsp. steigerwaltii strain in wild boar (Sus scrofa) from France. The molecular analysis conducted showed non-synonymous mutations in the pmrA/pmrB and phoQ/phoP operons and the phoP/Q regulator mgrB gene, leading to colistin resistance. The present data highlight the need for continuous monitoring of multidrug-resistant bacteria in wild animals to limit the spread of these threatening pathogens.

Development of real-time PCR assay allowed describing the first clinical Klebsiella pneumoniae isolate harboring plasmid-mediated colistin resistance mcr-8 gene in Algeria.

OBJECTIVES: We aimed to develop here a specific real-time PCR assay with TaqMan® probe to detect efficiently bacterial strains harboring the new plasmid mediated-colistin resistance mcr-8 gene. METHODS: Specific primers and probe for mcr-8 gene were designed from sequences alignment of all mcr genes variants. Specificity of the designed primers and probe were first checked par BlastN analysis and by in silico PCR. The analytical sensitivity and specificity tests were performed in vitro on a panel of 290 genomic DNA of Gram-negative bacteria and 250 metagenomic DNA from human stool samples. Whole genome sequencing (WGS) was performed here using MiSeq technology. RESULTS: Designed primers and probe were 100% specific tomcr-8 gene by BlastN and in silico PCR analysis. Real-time PCR screening of a collection of clinical isolates resulted to one positive Klebsiella pneumoniae isolate (KP95). WGS confirmed that this isolate harbored the mcr-8 gene and other resistance genes such as blaOXA-48, blaCTX-M-15 ß-lactamases. Our real-time PCR was highly sensitive on a 10-fold dilution serie from a calibrated inoculum at 108 CFU/mL with a limit of detection at 55 CFU/mL. CONCLUSION: To the best of our knowledge, we propose here, the first real-time PCR assay targeting mcr-8 gene with high specificity and sensitivity, able to detect mcr-8 gene in less than 2 h from any DNA sample. This real-time PCR assay allowed the first description of a clinical K. pneumoniae strain harboring the mcr-8 gene in Algeria.

Investigation of urban birds as source of ß-lactamase-producing Gram-negative bacteria in Marseille city, France.

BACKGROUND: We investigate here the presence of multidrug-resistant bacteria isolated from stool samples of yellow-legged gulls and chickens (n = 136) in urban parks and beaches of Marseille, France. Bacterial isolation was performed on selective media, including MacConkey agar with ceftriaxone and LBJMR medium. Antibiotic resistance genes, including extended-spectrum ß-lactamases (ESBL) (i.e. blaCTX-M, blaTEM and blaSHV), carbapenemases (blaKPC, blaVIM, blaNDM, blaOXA-23, blaOXA-24, blaOXA-48 and blaOXA-58) and colistin resistance genes (mcr-1 to mcr-5) were screened by real-time PCR and standard PCR and sequenced when found. RESULTS: Of the 136 stools samples collected, seven ESBL-producing Gram-negative bacteria (BGN) and 12 colistin-resistant Enterobacteriaceae were isolated. Among them, five ESBL-producing Escherichia coli and eight colistin-resistant Hafnia alvei strains were identified. Four blaTEM-1 genes were detected in yellow-legged gulls and chickens. Three CTX-M-15 genes were detected in yellow-legged gulls and pigeons, and one CTX-M-1 in a yellow-legged gull. No mcr-1 to mcr-5 gene were detected in colistin-resistant isolates. Genotyping of E. coli strains revealed four different sequence types already described in humans and animals and one new sequence type. CONCLUSIONS: Urban birds, which are believed to have no contact with antibiotics appear as potential source of ESBL genes. Our findings highlight the important role of urban birds in the proliferation of multidrug-resistant bacteria and also the possible zoonotic transmission of such bacteria from wild birds to humans.