Molecular epidemiology and antimicrobial resistance features of Acinetobacter baumannii clinical isolates from Pakistan

Abstract

Background: Acinetobacter baumannii is a Gram-negative opportunistic pathogen with a notorious reputation of being resistant to antimicrobial agents. The capability of A. baumannii to persist and disseminate between healthcare settings has raised a major concern worldwide. Methods: Our study investigated the antibiotic resistance features and molecular epidemiology of 52 clinical isolates of A. baumannii collected in Pakistan between 2013 and 2015. Antimicrobial susceptibility patterns were determined by the agar disc diffusion method. Comparative sequence analyses of the ampC and bla OXA-51-like alleles were used to assign the isolates into clusters. The whole genomes of 25 representative isolates were sequenced using the MiSeq Desktop Sequencer. Free online applications were used to determine the phylogeny of genomic sequences, retrieve the multilocus sequence types (ST), and detect acquired antimicrobial resistance genes.Results: Overall, the isolates were grouped into 7 clusters and 3 sporadic isolates. The largest cluster, Ab-Pak-cluster-1 (bla OXA-66 and ISAba1-ampC-19) included 24 isolates, belonged to ST2 and International clone (IC) II, and was distributed between two geographical far-off cities, Lahore and Peshawar. Ab-Pak-clusters-2 (bla OXA-66 , ISAba1-ampC-2), and -3 (bla OXA-66 , ISAba1-ampC-20) and the individual isolate Ab-Pak-Lah-01 (ISAba1-bla OXA-66 , ISAba1-ampC-2) were also assigned to ST2 and IC II. On the other hand, Ab-Pak-clusters-4 (bla OXA-69 , ampC-1), -5 (bla OXA-69 , ISAba1-ampC-78), and -6A (bla OXA-371 , ISAba1-ampC-3) belonged to ST1, while Ab-Pak-cluster-6B (bla OXA-371 , ISAba1-ampC-8) belonged to ST1106, with both ST1 and ST1106 being members of IC I. Five isolates belonged to Ab-Pak-cluster-7 (bla . This cluster corresponded to ST158, showed a well-delineated position on the genomic phylogenetic tree, and was equipped with several antimicrobial resistance genes including bla OXA-23 and bla . Conclusions:Our study detected the occurrence of 7 clusters of A. baumannii in Pakistan. Altogether, 6/7 of the clusters and 45/52 (86.5%) of the isolates belonged to IC I (n = 9) or II (n = 36), making Pakistan no exception to the global domination of these two clones. The onset of ST158 in Pakistan marked a geographical dispersal of this clone beyond the Middle East and brought up the need for a detailed characterization.

Diversity of carbapenem-resistantAcinetobacter baumanniiand bacteriophage-mediated spread of the Oxa23 carbapenemase

“…In addition, two isolates belonged to ST PAS 15, which are members of IC4, and two isolates belonged to ST PAS 25, which are members of IC7 (Table 1). All isolates belonging to the ICs carried the oxaAb allele previously shown to be associated with their respective IC, with isolates in CC PAS 1 (IC1) carrying oxaAb (69), isolates in CC PAS 2 (IC2) carrying oxaAb (66), isolates in ST PAS 15 (IC4) carrying oxaAb (51), and isolates in ST PAS 25 (IC7) carrying the oxaAb (64) allele (57). Isolates in ST PAS 158 carried oxaAb (65) alleles, which are usually associated with CC PAS 79 and IC5.…”

“…The allele profiles of the founder sequence types of CC PAS 158 and CC PAS 79 (ST PAS 158 and ST PAS 79 respectively) are quite different, sharing only 1 of the 7 alleles (rplB allele 4), which at the nucleotide level translates to 13 SNPs. It is therefore clear that in this instance, numbering the oxaAb alleles based upon their amino acid sequence can mask important epidemiological information and that, as suggested by Karah et al (64), these genes should be numbered according to their nucleotide sequences as has been done for the Acinetobacter ampC genes (69).…”

Acinetobacter baumannii isolados em amostras de pacientes pediátricos internados em um hospital especializado em doenças infectocontagiosas / Acinetobacter baumannii isolated from samples of pediatric patients admitted to a hospital specializing in infectious diseases

“…11,12 Sua capacidade de sobreviver por longos períodos em superfícies é notória e é provavelmente importante para a transmissão dentro do ambiente de cuidados de saúde. 10,13 Em geral, acomete pacientes hospitalizados que foram submetidos a procedimentos invasivos, ou imunodeprimidos, tais como pacientes com síndrome da imunodeficiência adquirida, transplantados e em uso de antineoplásicos. 14 A característica alarmante deste patógeno é sua capacidade de desenvolver diversos mecanismos de resistência a drogas existentes, levando a falhas terapêuticas recentemente.…”

“…8,17 A resistência bacteriana continua a aumentar e os pesquisadores de medicamentos e as indústrias manufatureiras não estão produzindo novos medicamentos para substituir os antimicrobianos existentes contra os quais a resistência se desenvolveu. 13 Entre as bactérias Gram-negativas, a produção de betalactamases é a principal forma de resistência bacteriana aos antimicrobianos betalactâmicos. Betalactamases são enzimas que promovem a degradação do anel betalactamico, inativando o antimicrobiano e impedindo que ele apresente atividade contra as enzimas responsáveis pela síntese da parede celular bacteriana.…”

“…Betalactamases são enzimas que promovem a degradação do anel betalactamico, inativando o antimicrobiano e impedindo que ele apresente atividade contra as enzimas responsáveis pela síntese da parede celular bacteriana. 13 Os carbapenêmicos são antimicrobianos bactericidas da B-lactama com eficácia comprovada em infecções graves causada por bactérias produtoras de β-lactamase de espectro estendido ESBL. O modo de ação dos carbapenêmicos é iniciado primeiro pela penetração na parede celular bacteriana e pela ligação a enzimas conhecidas como proteínas de penicilina.…”