IncFIB plasmids carrying the resistance gene blaCTX-M-15 in ESBL-producing Escherichia coli clones from pediatric patients.

INTRODUCTION: The emergence of extended-spectrum ß-lactamases (ESBLs)-producing Escherichia coli clones are a public health concern worldwide. Scarce information does exist about the spread of ESBLs-producing E. coli in pediatric patients from developing countries. METHODOLOGY: E. coli strains were analyzed by multilocus-sequence-typing, pulsed-field-gel-electrophoresis and phylogenetic group. The antimicrobial-resistance genes were detected by PCR, and plasmid content by the PCR-based replicon-typing. Horizontal transfer was tested by conjugation and the location of the blaCTX-M-15 gene by Southern blot hybridization. RESULTS: Thirty-two cefotaxime-resistant E. coli were recovered. Eleven of them were ESBL-producing isolates, which were well characterized and ascribed to seven sequence types and five phylogroups. The ESBL CTX-M-15 was the most prevalent enzyme (9 of 11). Plasmids of variable sizes (40-220 kb) were visualized, and the incompatibility (Inc) group FIB plasmid-replicon was detected in the ESBL strains and transferred by conjugation in 45.45% of them. Plasmid-borne toxin-antitoxin systems were the most frequently detected systems, strongly associated to IncF plasmids. The CTX-M-15-encoding gene was located on IncFIB plasmids. CONCLUSIONS: Even though a small number of ESBL-producing strains was recovered, we evidenced that IncFIB plasmids carry the blaCTX-M-15 gene, highlighting the role of IncF-type plasmids in facilitating the spread and maintenance of ESBL-encoding genes, which further favors the rapid increase of the antimicrobial resistance dissemination in disease-causing E. coli strains in pediatric patients.

Antibiotic resistance mechanisms in Acinetobacter spp. strains isolated from patients in a paediatric hospital in Mexico.

OBJECTIVES: The aim of this study was to identify Acinetobacter spp. strains from paediatric patients, to determine their genetic relationship, to detect antibiotic resistance genes and to evaluate the role of efflux pumps in antibiotic resistance. METHODS: A total of 54 non-duplicate, non-consecutive Acinetobacter spp. isolates were collected from paediatric patients. Their genetic relationship, antibiotic resistance profile, efflux pump activity, antibiotic resistance genes and plasmid profile were determined. RESULTS: The isolates were identified as 24 Acinetobacter haemolyticus, 24 Acinetobacter calcoaceticus-baumannii (Acb) complex and 1 strain each of Acinetobacter junii, Acinetobacter radioresistens, Acinetobacter indicus, Acinetobacter lwoffii, Acinetobacter ursingii and Acinetobacter venetianus. The 24 A. haemolyticus were considered genetically unrelated. One strain was resistant to carbapenems, two to cephalosporins, two to ciprofloxacin and sixteen to aminoglycosides. The antibiotic resistance genes blaOXA-214 (29%), blaOXA-215 (4%), blaOXA-264 (8%), blaOXA-265 (29%), blaNDM-1 (4%), aac(6')-Ig (38%) and the novel variants blaOXA-575 (13%), blaTEM-229 (75%), aac(6')-Iga (4%), aac(6')-Igb (13%) and aac(6')-Igc (42%) were detected. Among 24 Acb complex, 5 were multidrug-resistant, carbapenem-resistant strains carrying blaOXA-51 and blaOXA-23; they were genetically related and had the same plasmid profile. Other species were susceptible. In some strains of A. haemolyticus and Acb complex, the role of RND efflux pumps was evidenced by a decrease in the MICs for cefotaxime, amikacin and ciprofloxacin in the presence of an efflux pump inhibitor. CONCLUSIONS: This study identified isolates of A. haemolyticus carrying new ß-lactamase variants and shows for the first time the contribution of efflux pumps to antibiotic resistance in this species.

First evidence of polar flagella in Klebsiella pneumoniae isolated from a patient with neonatal sepsis.

The genus Klebsiella belongs to the family Enterobacteriaceae, and is currently considered to be non-motile and non-flagellated. In the present work, 25 Klebsiella strains isolated from nosocomial infections were assessed for motility under different growth conditions. One Klebsiella isolate, KpBUAP021, demonstrated a swim-like motility phenotype. The K. pneumoniae genotype was confirmed by 16S rRNA and rpoB gene sequence analysis. Multilocus sequence typing analysis also revealed that the KpBUAP021 strain places it in the ST345 sequence type, and belongs to the phylogenetic Kpl group. Transmission electron microscopy and the Ryu staining technique revealed that KpBUAP021 expresses polar flagella. Finally, the presence of fliC, fliA and flgH genes in this K. pneumoniae strain was confirmed. This report presents the first evidence for flagella-mediated motility in a K. pneumoniae clinical isolate, and represents an important finding related to its evolution and pathogenic potential.