AUTHOR=Machado Elisabete , COQUE TERESA M., Cantón Rafael , Sousa João C., Peixe Luísa 

TITLE=Commensal Enterobacteriaceae as reservoirs of extended-spectrum beta-lactamases, integrons, and sul genes in Portugal

JOURNAL=Frontiers in Microbiology

VOLUME=4

YEAR=2013

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2013.00080

DOI=10.3389/fmicb.2013.00080

ISSN=1664-302X

ABSTRACT=<p>Bacteria colonizing the human intestine have a relevant role in the spread of antimicrobial resistance. We investigated the faecal carriage of extended-spectrum beta-lactamase (ESBL)-producing <italic>Enterobacteriaceae</italic> in healthy humans from Portugal and analyzed the distribution of <italic>sul</italic> genes and class 1 and 2 integrons. Faecal samples (<italic>n</italic> = 113) were recovered from healthy persons (North/Centre of Portugal, 2001–2004) and plated on MacConkey agar with and without ceftazidime (1 mg/L) or cefotaxime (1 mg/L). Isolates representing different morphotypes/plate and antibiotic susceptibility patterns (<italic>n</italic> = 201) were selected. Isolates resistant to sulfonamides and/or streptomycin, gentamicin, and trimethoprim were screened (PCR and sequencing) for <italic>sul</italic> genes (<italic>sul1, sul2, sul3</italic>) and class 1 and 2 integrons. Presence of ESBLs was inferred using the double disk synergy test (DDST) and further confirmed by PCR and sequencing. ESBL producers were selected for clonal analysis, plasmid characterization and conjugation assays by standard methods. ESBL-producing isolates were found in 1.8% (2/113) of samples, corresponding to <italic>Escherichia coli</italic> of phylogroups A (<italic>n</italic> = 1) and B1 (<italic>n</italic> = 1) carrying transferable <italic>bla</italic><sub>CTX-M-14</sub> and the new <italic>bla</italic><sub>TEM-153</sub>, respectively. A 80kb IncK plasmid bearing <italic>bla</italic><sub>CTX-M-14</sub> was found, being highly related to that widely spread among CTX-M-14 producers of humans and animals from Portugal and other European countries. <italic>sul</italic> genes were found in 88% (22/25; <italic>sul2</italic>-60%, <italic>sul1</italic>-48%, <italic>sul3-</italic>4%) of the sulfonamide resistant isolates. Class 1 integrons were more frequently found than class 2 (7%, 14/201 <italic>vs.</italic> 3%, 6/201). Interestingly, gene cassette arrangements within these platforms were identical to those commonly observed among <italic>Enterobacteriaceae</italic> from Portuguese food-producing animals, although <italic>aadA13</italic> is here firstly described in <italic>Morganella morganii</italic>. These results reinforce the relevance of human commensal flora as reservoir of clinically relevant antibiotic resistance genes including <italic>bla</italic><sub>ESBLs</sub>, and highly transferable genetic platforms as IncK epidemic plasmids.</p>