Fecal carriage of MDROs in Lebanese elderly : dynamics and impact on bacterial fitness

Abstract

High fecal carriage rates of resistant Enterobacteriaceae were reported in Lebanese nursing home. The presence of these resistant bacteria increases the risk of endogenous infections. Possible fitness cost exhibited by bacteria carrying resistant genes may lead to its decrease in frequency. The aim of this study is to identify possible correlation between the fecal carriage and the fitness cost of β-lactamase producing Enterobacteriaceae, and in particular in E.coli isolates. In the present study, fecal carriage of resistant Enterobacteriaceae was investigated in 10 elderly patients, residing in a nursing home located in Tripoli, north Lebanon, and previously reported as carriers. During the period between June 29th and December 1st , 2015,6 fecal sampling were performed at regular intervals. Susceptible as well as resistant Gram negative bacilli were screened and their phenotypic susceptibility profiles were identified. ESBL, MBL, AmpC and KPC production was detected using plain Muller Hinton agar (MHA) plates, MHA plates impregnated with 5mM of EDTA, 10mg/mL of Phenyl Boronic Acid (PBA) and 250μg/mL of Cloxacillin (embedded). Identification of isolates was performed using API 20E. Afterwards, through a separate set of experiments, in-vitro competition assays were conducted on combinations of isolates selected from the collected sensitive, OXA, AmpC, and ESBL producing E.coli isolates. During the study, 9 out of the 10 recruited elderly were identified as "at least one time carriers" of resistant Enterobacteriaceae. Over a totalof117collected isolates, 8.5% were ESBL producer and 6% were AmpC producers. The majority of the collected isolates were identified as E. coli (71.2%). As for the in-vitro competition assays, with the sensitive E. coli being the fittest, a decrease in fitness was majorly observed with OXA producer, followed respectively by AmpC and ESBL producing E.coli. The observed trends of fecal carriage along with the relative fitness of β-lactamase producing E.coli leads to consider reducing antimicrobial agents use and even adopting less damaging alternative therapeutic options for the management of colonization by resistant bacteria.