Browsing by Author "Roman, Juan C."
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- ItemPorin alterations present in non-carbapenemase-producing Enterobacteriaceae with high and intermediate levels of carbapenem resistance in Chile(SOC GENERAL MICROBIOLOGY, 2012) Wozniak, Aniela; Villagra, Nicolas A.; Undabarrena, Agustina; Gallardo, Natalia; Keller, Nicole; Moraga, Marcela; Roman, Juan C.; Mora, Guido C.; Garcia, PatriciaThe main goal of this work was to identify the mechanisms responsible for carbapenem resistance in 61 Chilean clinical isolates of Enterobacteriaceae (Enterobacter spp., Serratia marcescens, Morganella morganii, Escherichia coli and Klebsiella pneumoniae) with reduced susceptibility to at least one carbapenem (ertapenem, imipenem or meropenem). All of the isolates were analysed for the presence of carbapenemases, extended spectrum beta-lactamases (ESBLs), AmpC enzymes and outer-membrane proteins. None of the isolates exhibited carbapenemase activity nor did they have any of the carbapenemase genes that were screened for. Most of the 61 strains produced at least one ESBL and/or one AmpC enzyme and either lost their porins or had altered porins according to sequence analysis. The distribution of ESBLs and AmpC enzymes was different among the species studied. Resistance in K. pneumoniae and E. coli isolates was associated with ESBLs; in M. morganii isolates, resistance was attributed to overexpression of an AmpC enzyme; and in Enterobacter spp. isolates, resistance was associated with both types of enzymes. In K. pneumoniae isolates, porin integrity was more a determinant of carbapenem resistance than the presence of ESBLs, whereas in isolates of Enterobacter spp., M. morganii and S. marcescens, the presence of an overexpressed AmpC enzyme was associated with higher imipenem and meropenem MIC values. Therefore, carbapenem resistance in Chilean isolates is not due to true carbapenemases but rather to a combination of porin loss/alteration and beta-lactamase activity. The fact that carbapenemases were not detected in this study is unique, given that many countries in the region have already reported the presence of these enzymes.
- ItemPresence of Bordetella holmesii in an outbreak of pertussis in Chile(SOC CHILENA INFECTOLOGIA, 2013) Miranda, Carolina; Wozniak, Aniela; Castillo, Claudia; Geoffroy, Enrique; Zumaran, Cecilia; Porte, Lorena; Roman, Juan C.; Potin, Marcela; Garcia, PatriciaThe incidence of whooping cough in Chile ranges from 4.1 and 7.5 per hundred thousand inhabitants. B. pertussis detection is performed by Real Time PCR (Q-PCR) directed to the insertion sequence IS481. However, this sequence is also found in the genome of B. bronchiseptica and B. holmesii. The latter is also a respiratory pathogen whose clinical features are similar to B. pertussis. However, it is important to differentiate between these species because in immunosuppressed patients B. holmesii is more likely to cause bacteremia and is less susceptible to erythromycin. The goal of this work is to measure prospectively and retrospectively the presence of B. holmesii in samples reported positive for B. pertussis in the period 2010-2011. During this period, 1994 nasopharyngeal specimens entered the laboratory for Bordetella sp. PCR, of which 224 were positive. The analysis by Q-PCR directed to the recA gene of B. holmesii of all 224 positive samples determined a prevalence of B. holmesii of 0.6% (12/1994). Because of its more aggressive behavior in immunosupressed patients and its different resistance pattern, routine screening of B. pertussis and B. holmesii is currently performed for all samples in which Bordetella sp PCR is initially detected.