Emergence and clonal spread of KPC-2-producing clinical Klebsiella aerogenes isolates in a hospital from northwest Argentina

Introduction. Klebsiella aerogenes is a nosocomial pathogen associated with drug resistance and healthcare-associated infections.Gap Statement. K. aerogenes is associated with hospital-acquired infections with the ability to acquire mechanisms of resistance to reserve antimicrobials; its clinical behaviour has been poorly documented.Objective. We proposed to investigate an outbreak of carbapenem-resistant K. aerogenes in a hospital that persisted for 4 months.Methods. The primary aim was to evaluate the molecular characteristics and the clonal relationships among the isolates. We characterized isolates by polymerase chain reaction (PCR) and pulsed-field gel electrophoresis (PFGE). The information was integrated with clinical and epidemiological data.Results. Fourteen strains were disseminated in an intensive care unit and different wards at the hospital. The overall mortality was 42.8 %, and mortality attributed to infection was 21.4 %; strains showed high rates of resistance to most of the antimicrobials tested and carried bla _KPC-2, bla _SHV-2 and bla _CTXM-15 genes. PFGE analysis indicated 2 PFGE groups; 12/14 isolates were associated with subgroup A and were likely to be primarily responsible for the first isolation and subsequent dissemination. The outbreak characteristics data showed prolonged hospitalization and previous use of antibiotics as potential risk factors.Conclusion. We consider that it is essential to perform phenotypic and genotypic identification of early genetic resistance mechanisms in K. aerogenes isolates, not only from infection sites but also from colonization, to prevent the spread of these multidrug-resistant (MDR) isolates.

[Impact of an active surveillance program and infection control measures on the incidence of carbapenem-resistant Gram-negative bacilli in an intensive care unit]

Hospital-acquired infections caused by carbapenem-resistant Gram-negative bacteria (CRGNB) have been increasingly reported worldwide and are associated with high rates of mortality especially in intensive care units(ICUs). Early identification through rectal surveillance cultures and implementation of infection control measures(ICM) including contact precautions, staff education on cleaning and hand hygiene may reduce the spread of these microorganisms. The aim of this work was to assess the impact of enhanced ICM on CRGNB colonization and to describe the molecular epidemiology of these bacteria in a polyvalent ICU in a tertiary level hospital. A prospective study including audits and active surveillance culture program, with molecular characterization, was conducted before and after the implementation of prevention programs and infection control measures. Microbiological screening was performed in chromogenic media; PCR targeting β-lactamases genes (bla_KPC, bla_NDM, bla_VIM and bla_OXA-48, bla_SHV and bla_CTX-M), molecular typing by PFGE; and MLST in K. pneumoniae were performed. CRGNB colonization was reduced from 16.92% to 9.67% upon implementing the infection control measures. In K. pneumoniae the most frequent carbapenemase type was KPC-2 associated with SHV-2 and CTX-M-15, and was disseminated in various STs (ST17, ST13, ST2256, ST353); there was no persistence of particular clones and virulence factors showed no association with hypervirulence. IMP-1 carbapenemase predominated in A. baumannii and the PFGE analysis individualized 3 clusters, assuming that the dissemination in the ICU was clonal. The early detection of patients colonized with CRBGN by using epidemiological surveillance cultures and the implementation of prophylactic measures are key to reducing the incidence of these microorganisms.

Topographic organization of sensory projections to the olfactory bulb

The detection of odorant receptor mRNAs within the axon terminals of sensory neurons has permitted us to ask whether neurons expressing a given receptor project their axons to common glomeruli within the olfactory bulb. In situ hybridization with five different receptor probes demonstrates that axons from neurons expressing a given receptor converge on one, or at most, a few glomeruli within the olfactory bulb. Moreover, the position of specific glomeruli is bilaterally symmetric and is constant in different individuals within a species. These data support a model in which exposure to a given odorant may result in the stimulation of a spatially restricted set of glomeruli, such that the individual odorants would be associated with specific topographic patterns of activity within the olfactory bulb.