Browsing by Author "Wozniak, A."

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    Acquisition of resistance to ceftazidime-avibactam during infection treatment in Pseudomonas aeruginosa through D179Y mutation in one of two blaKPC-2 gene copies without losing carbapenem resistance
    (2022) García, P.; Brito, B.; Alcalde-Rico, M.; Munita, J.M.; Martínez, J.R.W.; Olivares-Pacheco, J.; Quiroz, V.; Wozniak, A.
    Ceftazidime/Avibactam (CAZ/AVI) is frequently used to treat KPC-producing Pseudomonas aeruginosa (KPC-PA) and Enterobacterales. CAZ/AVI resistance is driven by several mechanisms. In P. aeruginosa this mainly occurs through alteration of AmpC, porins, and/or efflux pump overexpression, whereas in Enterobacterales it frequently occurs through D179Y substitution in the active site of KPC enzyme. This aminoacid change abolishes AVI binding to the KPC active site, hence inhibition is impaired. However, this substitution also decreases KPC-mediated resistance to carbapenems (“see-saw” effect). The goal of this work was to characterize the in vivo acquisition of CAZ/AVI resistance through D179Y substitution in a KPC-PA isolated from a hospitalized patient after CAZ/AVI treatment. Two KPC-PA isolates were obtained. The first isolate, PA-1, was obtained before CAZ/AVI treatment and was susceptible to CAZ/AVI. The second isolate, PA-2, was obtained after CAZ/AVI treatment and exhibited high-level CAZ/AVI resistance. Characterization of isolates PA-1 and PA-2 was performed through short and long-read whole genome sequencing analysis. The hybrid assembly showed that PA-1 and PA-2A had a single plasmid of 54,030 bp, named pPA-1 and pPA-2 respectively. Each plasmid harbored two copies of the blaKPC-containing Tn4401b transposon. However, while pPA-1 carried two copies of blaKPC-2, pPA-2 had one copy of blaKPC-2 and one copy of blaKPC-33, the allele with the D179Y substitution. Interestingly, isolate PA-2 did not exhibit the “see-saw” effect. The blaKPC-33 allele was detected only through hybrid assembly using a long-read-first approach. The present work describes a KPC-PA isolate harboring a plasmid-borne CAZ/AVI resistance mechanism based on two copies of blaKPC-2-Tn4401b and D179Y mutation in one of them, that is not associated with loss of resistance to carbapenems. These findings highlight the usefulness of a fine-tuned combined analysis of short and long-read data to detect similar emerging resistance mechanisms.
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    M-protein gene-type distribution and hyaluronic acid capsule in group A Streptococcus clinical isolates in Chile: association of emm gene markers with csrR alleles
    (CAMBRIDGE UNIV PRESS, 2012) Wozniak, A.; Rojas, P.; Rodriguez, C.; Undabarrena, A.; Garate, C.; Riedel, I.; Roman, J. C.; Kalergis, A. M.; Garcia, P.
    Streptococcus pyogenes causes a variety of infections because of virulence factors such as capsular hyaluronic acid and M protein. The aim of this study was to determine emm types and capsule phenotype in 110 isolates of S. pyogenes from patients with invasive (sterile sites) and non-invasive (mainly pharyngitis) infections in Chile, and the relationship between both virulence factors. The most abundant types found were emm12, emm1, emm4 and emm28 and their distribution was similar to that seen in Latin America and developed countries, but very different from that in Asia and Pacific Island countries. Ten of 16 emm types identified in pharyngeal isolates were found in sterile-site isolates, and three of nine emm types of sterile-site isolates occurred in pharyngeal isolates; three emm subtypes were novel. The amount of hyaluronic acid was significantly higher in sterile-site isolates but did not differ substantially among emm types. Only three isolates were markedly capsulate and two of them had mutations in the csrR gene that codes for a repressor of capsule synthesis genes. We found a non-random association between emm types and csrR gene alleles suggesting that horizontal gene transfer is not freely occurring in the population.
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    Primer aislado de Pseudomonas aeruginosa productora de Sao Paulo metalo-β-lactamasa (SPM-1) en un paciente chileno
    (2021) Wozniak, A.; Rodríguez, N.; Alcalde-Rico, M.; Castillo, C.; García, P.
    Las enzimas VIM, IMP, y NDM son carbapenemasas de tipo metalo-β-lactamasas (MBLs) que se encuentran ampliamente distribuidas en el mundo. La SPM-1 (Sao Paulo metalo-β-lactamasa) es una MBL que fue descrita en Pseudomonas aeruginosa en Sao Paulo (Brasil) en 2002. Comunicamos por primera vez la presencia de SPM-1 en Chile, en un aislado de P aeruginosa resistente a meropenem e imipenem, detectado en un cultivo rectal de vigilancia de carbapenemasas desde un paciente internado en nuestra institución. La secuencia del producto de la RPC fue 100% idéntica a la secuencia de SPM-1 reportada en Brasil. El paciente tenía antecedentes de una angioplastía realizada en Brasil en 2004-2005. Como consecuencia de este hallazgo, la detección de SPM mediante RPC será incorporada a la búsqueda de rutina de carbapenemasas en P aeruginosa.