Posgrado en Ciencias de la Tierra, Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Ciudad de México, México.
Unidad de Investigación en Enfermedades Infecciosas Área de Genética Bacteriana, Hospital Infantil de México Federico Gómez, Ciudad de México, México.
PLoS One. 2022 May 10;17(5):e0266742. doi: 10.1371/journal.pone.0266742. eCollection 2022.
Pseudomonas aeruginosa has different resistant mechanisms including the constitutive MexAB-OprM efflux pump. Single nucleotide polymorphisms (SNPs) in the mexR, nalC, and nalD repressors of this efflux pump can contribute to antimicrobial resistance; however, it is unknown whether these changes are mainly related to genetic lineages or environmental pressure. This study identifies SNPs in the mexR, nalC, and nalD genes in clinical and environmental isolates of P. aeruginosa (including high-risk clones). Ninety-one P. aeruginosa strains were classified according to their resistance to antibiotics, typified by multilocus sequencing, and mexR, nalC, and nalD genes sequenced for SNPs identification. The mexAB-oprM transcript expression was determined. The 96.7% of the strains were classified as multidrug resistant. Eight strains produced serine carbapenemases, and 11 strains metallo-β-lactamases. Twenty-three new STs and high-risk clones ST111 and ST233 were identified. SNPs in the mexR, nalC, and nalD genes revealed 27 different haplotypes (patterns). Sixty-two mutational changes were identified, 13 non-synonymous. Haplotype 1 was the most frequent (n = 40), and mainly identified in strains ST1725 (33/40), with 57.5% pan drug resistant strains, 36.5% extensive drug resistant and two strains exhibiting serin-carbapenemases. Haplotype 12 (n = 9) was identified in ST233 and phylogenetically related STs, with 100% of the strains exhibiting XDR and 90% producing metallo-β-lactamases. Haplotype 5 was highly associated with XDR and related to dead when compared to ST1725 and ST233 (RRR 23.34; p = 0.009 and RRR 32.01; p = 0.025). A significant relationship between the mexR-nalC-nalD haplotypes and phylogenetically related STs was observed, suggesting mutational changes in these repressors are highly maintained within genetic lineages. In addition, phylogenetically related STs showed similar resistant profiles; however, the resistance was (likely or partly) attributed to the MexAB-OprM efflux pump in 56% of the strains (only 45.05% showed mexA overtranscription), in the remaining strains the resistance could be attributed to carbapenemases or mechanisms including other pumps, since same SNPs in the repressor genes gave rise to different resistance profiles.
铜绿假单胞菌具有不同的耐药机制，包括组成型 MexAB-OprM 外排泵。该外排泵的 mexR、nalC 和 nalD 抑制剂中的单核苷酸多态性 (SNP) 可能导致抗菌药物耐药性；然而，尚不清楚这些变化主要与遗传谱系还是环境压力有关。本研究鉴定了临床和环境分离株（包括高风险克隆）中铜绿假单胞菌 mexR、nalC 和 nalD 基因中的 SNP。根据其对抗生素的耐药性，对 91 株铜绿假单胞菌菌株进行分类，采用多位点测序，对 mexR、nalC 和 nalD 基因进行测序以鉴定 SNP。测定了 mexAB-oprM 转录物的表达。96.7%的菌株被归类为多药耐药菌。8 株产生丝氨酸碳青霉烯酶，11 株产生金属β-内酰胺酶。鉴定了 23 个新的 ST 和高风险克隆 ST111 和 ST233。mexR、nalC 和 nalD 基因中的 SNP 显示出 27 种不同的单倍型（模式）。鉴定出 62 种突变，其中 13 种是非同义突变。单倍型 1 最为常见（n=40），主要存在于 ST1725 中（33/40），57.5%的泛耐药菌株、36.5%的广泛耐药菌株和 2 株产丝氨酸碳青霉烯酶。单倍型 12（n=9）存在于 ST233 和系统发育相关的 ST 中，100%的菌株表现出 XDR，90%的菌株产生金属β-内酰胺酶。单倍型 5 与 XDR 高度相关，与 ST1725 和 ST233 相比，与死亡相关（RRR 23.34；p=0.009 和 RRR 32.01；p=0.025）。观察到 mexR-nalC-nalD 单倍型与系统发育相关的 ST 之间存在显著关系，表明这些抑制剂中的突变在遗传谱系中得到高度维持。此外，系统发育相关的 ST 表现出相似的耐药谱；然而，耐药性（可能或部分）归因于 MexAB-OprM 外排泵，在 56%的菌株中（只有 45.05%表现出 mexA 过转录），在其余菌株中，耐药性可能归因于碳青霉烯酶或包括其他泵在内的机制，因为抑制剂基因中的相同 SNP 导致了不同的耐药谱。
