Novel Insights Into The Classification of Staphylococcal β-Lactamases In Relation To The Cefazolin Inoculum Effect.

Novel Insights Into The Classification of Staphylococcal β-Lactamases In Relation To The Cefazolin Inoculum Effect. Antimicrob Agents Chemother. 2020 Feb 18;: Authors: Carvajal LP, Rincon S, Echeverri AM, Porras J, Rios R, Ordoñez KM, Seas C, Gomez-Villegas SI, Diaz L, Arias CA, Reyes J Abstract Cefazolin has become a prominent therapy for methicillin-susceptible Staphylococcus aureus (MSSA) infections. However, an important concern is the cefazolin-inoculum effect (CzIE), a phenomenon mediated by staphylococcal β-lactamases. Four variants of staphylococcal β-lactamases have been described based on serological methodologies and limited sequence information. Here, we sought to reassess the classification of staphylococcal β-lactamases and their correlation with the CzIE. We included a large collection of 690 contemporary bloodstream MSSA isolates recovered from Latin America, a region with high prevalence of the CzIE. We determined cefazolin MICs at standard and high-inoculum by broth-microdilution. Whole-genome-sequencing was performed to classify the β-lactamase based on the predicted full sequence of BlaZ. We used the classical schemes for β-lactamase classification and compared it to BlaZ allotypes found in unique sequences using the genomic information. Phylogenetic analyses were performed based on the BlaZ and core-genome sequences. The overall prevalence of the CzIE was 40%. Among 641 genomes, type C was the most predomi...
Source: Antimicrobial Agents and Chemotherapy - Category: Microbiology Authors: Tags: Antimicrob Agents Chemother Source Type: research