Silent mutations in ribosomal protein genes are associated with high-risk clones of carbapenem-resistant Acinetobacter baumannii prevalent in Brazil

OBJECTIVES

To analyze the relationship of ribosomal protein mutations and clonality of high-risk clones Acinetobacter baumannii.

METHODS

Seventy-nine carbapenem-resistant A. baumannii were subjected to whole-genome sequencing (Illumina NextSeq), and codifying sequences of ribosomal proteins were extracted and screened for mutations. MALDI-TOF MS analysis (Bruker Biotyper) and Spectra data from MALDI-TOF was employed to generate a dendrogram based on principal component analysis (PCA) data. Clones were identified by Multilocus sequencing typing (MLST) based on WGS.

RESULTS

Ribosomal RNA protein sequences extracted from the genomes identified mutations that were associated with clonal complexes, but most of them were silent. PCA did not cluster the isolates according to their clonality identified by MLST.

CONCLUSIONS

By comparing the nucleotide and amino acid sequences of diversified A. baumannii, and Bruker Biotyper profiles, we showed that silent mutations in ribosomal RNA nucleotides are associated with clonal complexes, but since most of the mutations were silent, MALDI-TOF MS raw data was not a useful tool for typing the high-risk clones of this species.

Genomic and Clinical Characterization of IMP-1-Producing Multidrug-Resistant Acinetobacter bereziniae Isolates from Bloodstream Infections in a Brazilian Tertiary Hospital

Acinetobacter baumannii is the main species of the Acinetobacter genus; however, non-baumannii Acinetobacter (NBA) species causing infections have been described for the past years, as well as antimicrobial resistance. In this study, we describe the occurrence of two multidrug-resistant (MDR) IMP-1-producing Acinetobacter bereziniae isolates recovered from bloodstream infections in different patients but in the same intensive care unit among 134 carbapenem-resistant Acinetobacter screened. Antimicrobial susceptibility testing revealed resistance to carbapenems, extended spectrum, and antipseudomonad cephalosporins, amikacin, and trimethoprim-sulfamethoxazole. Both A. bereziniae isolates shared the same ApaI-pulsed-field gel electrophoresis (PFGE) pattern. Whole-genome sequencing of both isolates revealed that bla_IMP-1 was embedded into an In86 Class I integron carrying also sul1, aac(6')-31, and aadA genes. A new sequence type (ST1309 Pasteur) was deposited. The virulence genes lpxC and ompA, seen in A. baumannii, were detected in the A. bereziniae strains. Recognition of A. bereziniae causing invasive MDR infection underscores the role of NBA species as human pathogens especially in at-risk patients.