Selection of colistin-resistant Acinetobacter baumannii isolates in postneurosurgical meningitis in an intensive care unit with high presence of heteroresistance to colistin.
hyperproduction of the chromosomal enzymes, as well as resistant strains without synergy, were disregarded. During the first period, 15 (2.1%) of 707 outpatients were carriers of Escherichia coli (14 patients) or Proteus mirabilis (1 patient) with ESBL. This percentage increased during the second period, when 17 (3.8%) of 454 outpatients were carriers of E. coli with ESBL, and again in the third period, when 12 (7.5%) of 160 were carriers of E. coli (11 patients) or Enterobacter cloacae (1 patient) with ESBL. Characterization of the different ESBL isolated during the three study periods is in process. Although Klebsiella pneumoniae carrying ESBL has been detected in our hospital (7), as well as in other hospitals in Barcelona (8), no ESBL-producing K. pneumoniae strains were identified in this survey. Although we did not disregard either the patients’ previous treatment with antibiotics or previous hospitalization, these patients came to the hospital from the community carrying strains that express ESBL. Moreover, during these three periods we observed a significant increase in the frequency of ESBL carriers (from 2.1% to 7.5%; p<0.005). These data suggest that the community could be a reservoir for these enzymes, as occurs with other microorganisms (9–11). Many questions remain unanswered regarding the diffusion mechanisms of this resistance in the community. Confirmation of community-based transmission of ESBL would indicate a need for heightened vigilance and further studies to determine the reservoirs and vehicles for dissemination of ESBL within the community.