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Cefiderocol (FDC), a siderophore-cephalosporin conjugate, is the newest option for treating infection with carbapenem-resistant gram-negative bacteria. We identified a novel mechanism contributing to decreased FDC susceptibility in Klebsiella pneumoniae clinical isolates. The mechanism involves 2 coresident plasmids: pKpQIL, carrying variants of bla carbapenemase gene, and pKPN, carrying the ferric citrate transport (FEC) system. We observed increasing FDC MICs in an Escherichia coli model system carrying different natural pKpQIL plasmids, encoding different K. pneumoniae carbapenemase (KPC) variants, in combination with a conjugative low copy number vector carrying the fec gene cluster from pKPN. We observed transcriptional repression of fiu, cirA, fepA, and fhuA siderophore receptor genes in bla -fec-E. coli cells treated with ferric citrate. Screening of 27,793 K. pneumoniae whole-genome sequences revealed that the fec cluster occurs frequently in some globally distributed different KPC-producing K. pneumoniae clones (sequence types 258, 14, 45, and 512), contributing to reduced FDC susceptibility.

Background Campylobacter spp. infections present an urgent and significant global public health challenge. This study offers a genomic characterization of Campylobacter spp. isolates from human samples and chicken-origin food sources in Italy during 2023. Whole-genome sequencing, cluster analysis, genomic comparison of human and food of animal origin isolates, and characterization of antimicrobial resistance mechanisms were performed on 257 isolates. Results Campylobacter jejuni revealed considerable variability, with predominant types, including ST21, ST50 (ST21 CC), and ST3335 (ST206 CC), in human isolates, whereas ST50 and ST2116 (ST353 CC) prevailed in food sources. In contrast, C coli isolates were associated primarily with the ST828 CC. Cluster analysis based on core-genome multilocus sequence typing (cgMLST) revealed that 40.0% of the isolates formed 23 genetic clusters, suggesting potential outbreak scenarios. The isolates presented a high prevalence of ciprofloxacin resistance linked to mutations in GyrA (80.1%) and extensive tetracycline resistance attributed to tet genes (64.6%). Multidrug resistance was predominantly observed in C. coli (12.1%). Notably, the chromosomal erythromycin resistance gene erm (N) in food C. coli isolates was detected for the first time in Italy and for the first time worldwide in a veterinarian or food isolate. Conclusions This One Health study, which was based on genomic surveillance, improved our understanding of antimicrobial resistance and the epidemiology of Campylobacter spp. This study highlights the emergence of a novel antimicrobial resistance marker in Italy, erm (N), and reveals the prospective occurrence of multiple nationwide outbreak scenarios that demand immediate public health attention.

Background Livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) belonging to clonal complex 398 is recognized as an occupational hazard for workers employed in intensive animal husbandry, especially in the swine-breeding chain. In this study, we compared the prevalence and epidemiological type of MRSA isolates from swine and farm workers in a large area of southern Italy. Methods Between January and March 2018, 88 workers from 32 farms where we had previously performed a survey for MRSA colonization of farmed pigs, were sampled by nasal swabbing. A follow-up investigation was conducted on seven workers 1 year after primary screening. MRSA isolates were characterized by MLST, spa and SCC mec typing, and tested for susceptibility to 15 antimicrobials. Epidemiological correlations between human and swine MRSA isolates were supported by Rep-MP3 and RAPD PCR fingerprinting, and whole-genome sequencing. Results The overall colonization rate of MRSA in swine farm workers was 21.6%, being significantly higher in intensive farms and in workers with direct animal contact. All human MRSA isolates were multi-drug resistant, belonged to the ST398 livestock clade, and did not carry Panton-Valentine leukocidin and enterotoxin genes. Notably, 94.1% of human MRSA isolates belonged to the same epidemiological type as swine MRSA isolates from the corresponding farm. Persistent MRSA carriage was documented in some workers 1 year after primary sampling. Conclusions We report a high prevalence of MRSA among swine farm workers, with higher colonization rates associated with intensive breeding and animal exposure. Our findings suggest unidirectional animal-to-human transmission of LA-MRSA and denote the high zoonotic transmissibility of the ST398 livestock clade.

Bacteria belonging to the genus Aminobacter are metabolically versatile organisms thriving in both natural and anthropized terrestrial environments. To date, the taxonomy of this genus is poorly defined due to the unavailability of the genomic sequence of A. anthyllidis LMG 26462T and the presence of unclassified Aminobacter strains. Here, we determined the genome sequence of A. anthyllidis LMG 26462T and performed phylogenomic, average nucleotide identity and digital DNA-DNA hybridization analyses of 17 members of genus Aminobacter. Our results indicate that 16S rRNA-based phylogeny does not provide sufficient species-level discrimination, since most of the unclassified Aminobacter strains belong to valid Aminobacter species or are putative new species. Since some members of the genus Aminobacter can utilize certain C1 compounds, such as methylamines and methyl halides, a comparative genomic analysis was performed to characterize the genetic basis of some degradative/assimilative pathways in the whole genus. Our findings suggest that all Aminobacter species are heterotrophic methylotrophs able to generate the methylene tetrahydrofolate intermediate through multiple oxidative pathways of C1 compounds and convey it in the serine cycle. Moreover, all Aminobacter species carry genes implicated in the degradation of phosphonates via the C-P lyase pathway, whereas only A. anthyllidis LMG 26462T contains a symbiosis island implicated in nodulation and nitrogen fixation.

Campylobacter spp. infections present an urgent and significant global public health challenge. This study offers a genomic characterization of Campylobacter spp. isolates from human samples and chicken-origin food sources in Italy during 2023. Whole-genome sequencing, cluster analysis, genomic comparison of human and food of animal origin isolates, and characterization of antimicrobial resistance mechanisms were performed on 257 isolates. Campylobacter jejuni revealed considerable variability, with predominant types, including ST21, ST50 (ST21 CC), and ST3335 (ST206 CC), in human isolates, whereas ST50 and ST2116 (ST353 CC) prevailed in food sources. In contrast, C coli isolates were associated primarily with the ST828 CC. Cluster analysis based on core-genome multilocus sequence typing (cgMLST) revealed that 40.0% of the isolates formed 23 genetic clusters, suggesting potential outbreak scenarios. The isolates presented a high prevalence of ciprofloxacin resistance linked to mutations in GyrA (80.1%) and extensive tetracycline resistance attributed to tet genes (64.6%). Multidrug resistance was predominantly observed in C. coli (12.1%). Notably, the chromosomal erythromycin resistance gene erm(N) in food C. coli isolates was detected for the first time in Italy and for the first time worldwide in a veterinarian or food isolate. This One Health study, which was based on genomic surveillance, improved our understanding of antimicrobial resistance and the epidemiology of Campylobacter spp. This study highlights the emergence of a novel antimicrobial resistance marker in Italy, erm(N), and reveals the prospective occurrence of multiple nationwide outbreak scenarios that demand immediate public health attention.