BACKGROUND: FosA10-producing Enterobacterales have an extremely low incidence in Europe. PATIENTS AND METHODS: In March 2024, an 83-year-old woman, hospitalized in the Modena Province, developed an infection with fosfomycin-resistant Escherichia coli. The patient was treated with piperacillin/tazobactam and, after 10 days, the clinical picture was resolved. Fosfomycin MIC was evaluated with the reference agar dilution method and the production of FosA enzymes by phenotypic testing. Genomic characterization was assessed using long-read sequencing technology on the Sequel I platform. RESULTS: An E. coli isolate (FO_2) was collected from both blood and urine samples and showed high-level resistance to fosfomycin (MIC > 128 mg/L). The resistance to fosfomycin was ascribed to the production of FosA-like enzymes by phenotypic testing. The genomic analysis pointed to a FosA10-producing E. coli ST69. The fosA10 gene was carried by a highly conjugative IncB/O/K/Z plasmid that showed relevant similarities with other globally circulating plasmids. CONCLUSIONS: The acquisition of rare fosA-like genes in clinically relevant clones is concerning and the dissemination of FosA-producing E. coli should be continuously monitored.

• Publication type
• Journal Article MeSH

BACKGROUND: Wastewaters are considered as important players in the spread of antimicrobial resistance, thus affecting the health of humans and animals. Here, we focused on wastewaters as a possible source of carbapenemase-producing Enterobacterales for the environment. METHODS: A total of 180 presumptive coliforms from hospital and municipal wastewaters, and a river in the Czech Republic were obtained by selective cultivation on meropenem-supplemented media and tested for presence of carbapenemase-encoding genes by PCR. Strains carrying genes of interest were characterized by testing antimicrobial susceptibility, carbapenemase production and combination of short- and long- read whole-genome sequencing. The phylogenetic tree including publicly available genomes of Enterobacter asburiae was conducted using Prokka, Roary and RAxML. RESULTS: Three VIM-producing Enterobacter asburiae isolates, members of the Enterobacter cloacae complex, were detected from hospital and municipal wastewaters, and the river. The blaVIM-1 gene was located within a class 1 integron that was carried by different F-type plasmids and one non-typeable plasmid. Furthermore, one of the isolates carried plasmid-borne colistin-resistance gene mcr-10, while in another isolate chromosomally located mcr-9 without colistin resistance phenotype was detected. In addition, the analysis of 685 publicly available E. asburiae genomes showed they frequently carry carbapenemase genes, highlighting the importance of this species in the emergence of resistance to last-line antibiotics. CONCLUSION: Our findings pointed out the important contribution of hospital and community wastewaters in transmission of multi-drug resistant pathogens.

• Keywords
• mcr, Antimicrobial resistance, Carbapenemase, Environment,
• MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Drug Resistance, Bacterial genetics   MeSH
• Bacterial Proteins genetics   MeSH
• beta-Lactamases * genetics   MeSH
• Enterobacter * genetics   drug effects   isolation & purification   MeSH
• Phylogeny MeSH
• Colistin * pharmacology   MeSH
• Humans MeSH
• Microbial Sensitivity Tests MeSH
• Wastewater * microbiology   MeSH
• Plasmids genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Bacterial Proteins MeSH
• beta-Lactamases * MeSH
• carbapenemase MeSH Browser
• Colistin * MeSH
• Wastewater * MeSH
• VIM-1 metallo-beta-lactamase MeSH Browser

Fosfomycin (FOS) is an effective antibiotic against multidrug-resistant Enterobacterales, but its effectiveness is reducing. Little is known on the current prevalence of FosA enzymes in low-risk pathogens, such as Citrobacter freundii. The aim of the study was the molecular characterization of a carbapenemase- and FosA-producing C. freundii collected in Italy. AK867, collected in 2023, showed an XDR profile, retaining susceptibility only to colistin. AK867 showed a FOS MIC >128 mg/L by ADM. Based on WGS, AK867 belonged to ST116 and owned a wide resistome, including fosA3, blaKPC-2, and blaVIM-1. fosA3 was carried by a conjugative pKPC-CAV1312 plasmid of 320,480 bp, on a novel composite transposon (12,907 bp). FosA3 transposon shared similarities with other fosA3-harboring pKPC-CAV1312 plasmids among Citrobacter spp. We report the first case of FosA3 production in clinical carbapenemase-producing C. freundii ST116. The incidence of FosA3 enzymes is increasing among Enterobacterales, affecting even low-virulence pathogens, as C. freundii.

• Keywords
• Citrobacter freundii, carbapenemases, fosA3 gene, fosfomycin, fosfomycin resistance,
• MeSH
• Anti-Bacterial Agents * pharmacology   MeSH
• Bacterial Proteins * genetics   metabolism   MeSH
• beta-Lactamases * genetics   metabolism   MeSH
• Citrobacter freundii * genetics   enzymology   drug effects   MeSH
• Enterobacteriaceae Infections * microbiology   MeSH
• Fosfomycin * pharmacology   MeSH
• Humans MeSH
• Microbial Sensitivity Tests MeSH
• Drug Resistance, Multiple, Bacterial genetics   MeSH
• Plasmids genetics   MeSH
• Whole Genome Sequencing MeSH
• DNA Transposable Elements MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Italy epidemiology   MeSH
• Names of Substances
• Anti-Bacterial Agents * MeSH
• Bacterial Proteins * MeSH
• beta-Lactamases * MeSH
• carbapenemase MeSH Browser
• Fosfomycin * MeSH
• DNA Transposable Elements MeSH

Fosfomycin-resistant FosA8-producing Enterobacterales are uncommon strains with extremely low incidence in Europe, based on only three reports in the literature. We detected FosA8-producing Escherichia coli ST131 in clinical isolates from two patients admitted in February 2023 to a rehabilitation unit in Italy. The occurrence of rare fosA-like genes in the high-risk clone ST131 is of clinical relevance. The dissemination of FosA-producing E. coli, although still at low levels, should be continuously monitored.

• Keywords
• E. coli ST131, FosA8, Fosfomycin, Fosfomycin resistance,,
• MeSH
• Anti-Bacterial Agents * pharmacology   therapeutic use   MeSH
• Drug Resistance, Bacterial MeSH
• beta-Lactamases genetics   metabolism   MeSH
• Escherichia coli * isolation & purification   genetics   drug effects   MeSH
• Fosfomycin pharmacology   therapeutic use   MeSH
• Escherichia coli Infections * microbiology   epidemiology   MeSH
• Humans MeSH
• Microbial Sensitivity Tests MeSH
• Multilocus Sequence Typing MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Case Reports MeSH
• Geographicals
• Italy epidemiology   MeSH
• Names of Substances
• Anti-Bacterial Agents * MeSH
• beta-Lactamases MeSH
• Fosfomycin MeSH

Antimicrobial resistance is well-known to be a global health and development threat. Due to the decrease of effective antimicrobials, re-evaluation in clinical practice of old antibiotics, as fosfomycin (FOS), have been necessary. FOS is a phosphonic acid derivate that regained interest in clinical practice for the treatment of complicated infection by multi-drug resistant (MDR) bacteria. Globally, FOS resistant Gram-negative pathogens are raising, affecting the public health, and compromising the use of the antibiotic. In particular, the increased prevalence of FOS resistance (FOSR) profiles among Enterobacterales family is concerning. Decrease in FOS effectiveness can be caused by i) alteration of FOS influx inside bacterial cell or ii) acquiring antimicrobial resistance genes. In this review, we investigate the main components implicated in FOS flow and report specific mutations that affect FOS influx inside bacterial cell and, thus, its effectiveness. FosA enzymes were identified in 1980 from Serratia marcescens but only in recent years the scientific community has started studying their spread. We summarize the global epidemiology of FosA/C2/L1-2 enzymes among Enterobacterales family. To date, 11 different variants of FosA have been reported globally. Among acquired mechanisms, FosA3 is the most spread variant in Enterobacterales, followed by FosA7 and FosA5. Based on recently published studies, we clarify and represent the molecular and genetic composition of fosA/C2 genes enviroment, analyzing the mechanisms by which such genes are slowly transmitting in emerging and high-risk clones, such as E. coli ST69 and ST131, and K. pneumoniae ST11. FOS is indicated as first line option against uncomplicated urinary tract infections and shows remarkable qualities in combination with other antibiotics. A rapid and accurate identification of FOSR type in Enterobacterales is difficult to achieve due to the lack of commercial phenotypic susceptibility tests and of rapid systems for MIC detection.

• Keywords
• Enterobacterales, epidemiology, fosfomycin, fosfomycin-resistance, fosfomycin-resistant determinant,
• MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Drug Resistance, Bacterial genetics   MeSH
• Escherichia coli genetics   MeSH
• Fosfomycin * pharmacology   MeSH
• Klebsiella pneumoniae genetics   MeSH
• Escherichia coli Proteins * genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Fosfomycin * MeSH
• Escherichia coli Proteins * MeSH