Occurrence of plasmid-mediated fosfomycin resistance (fos genes) among Escherichia coli isolates, Portugal.

OBJECTIVES: To evaluate the occurrence of plasmid-mediated fos genes among fosfomycin-resistant Escherichia coli isolates collected from patients in Lisbon, Portugal, and characterize the fos-positive strains. METHODS: A total of 19 186 E. coli isolates were prospectively collected between April 2022 and January 2023 from inpatients and outpatients at a private laboratory in Lisbon. Fosfomycin resistance was initially assessed by semi-automated systems and further confirmed by the disc diffusion method. Resistant isolates were investigated for plasmid-mediated fos genes (fosA1-fosA10, fosC and fosL1-fosL2) and extended-spectrum beta-lactamases (ESBLs) by PCR and sequencing. Multilocus sequence typing was performed to evaluate the clonal relationship among fos-carrying isolates. RESULTS: Out of the 19 186 E. coli isolates, 100 were fosfomycin-resistant (0.5%), out of which 15 carried a fosA-like gene (15%). The most prevalent fosfomycin-resistant determinant was fosA3 (n = 11), followed by fosA4 (n = 4). Among the 15 FosA-producing isolates, 10 co-produced an ESBL (67%), being either of CTX-M-15 (n = 8) or CTX-M-14 (n = 2) types. The fosA3 gene was carried on IncFIIA-, IncFIB-, and IncY-type plasmids, whereas fosA4 was always located on IncFIB-type plasmids. Most FosA4-producing isolates belonged to a single sequence type ST2161, whereas isolates carrying the fosA3 gene were distributed into nine distinct genetic backgrounds. CONCLUSION: The prevalence of fosfomycin-resistant E. coli isolates is still low in Portugal. Notably, 15% of fosfomycin-resistant isolates harbour a transferable fosA gene, among which there is a high rate of ESBL producers, turning traditional empirical therapeutical options used in Portugal (fosfomycin and amoxicillin-clavulanic acid) ineffective.

Spontaneous bacterial peritonitis by Brucella in a cirrhotic patient.

Spontaneous bacterial peritonitis (SBP) is a frequent form of decompensation of end-stage liver disease, with an incidence of 15-20% and a short-term mortality of 10-33%. The usual causative agents (90% of SBP) are enteric Gram-negative bacteria-Escherichia coli and Klebsiella pneumoniae. Brucella is known to be a possible, but exceedingly rare, causative agent of SBP. We present the case of a 47-year-old Egyptian man, with hepatitis C cirrhosis, and a 2 week history of ascites, jaundice, encephalopathy, fever and pain on his right shoulder that started while travelling in the Middle East. Laboratory and imaging studies were undertaken and he was diagnosed an SBP that failed to respond to Imipenem. Brucella was identified both in the ascitic fluid and blood; he was started on doxycycline plus rifampin with immediate clinical improvement. The antibiotic regimen was kept for 8 weeks. The patient is currently under evaluation for liver transplantation.