Emergence of Colistin-Resistant Acinetobacter junii in China

Area of Science:

• Microbiology
• Genomics
• Antimicrobial Resistance

Background:

• Multidrug-resistant Gram-negative bacteria pose a significant global health threat.
• Colistin resistance in Acinetobacter junii is infrequently reported, making it an emerging concern.
• The study focuses on a specific clinical isolate, AJ6079, to understand resistance mechanisms.

Purpose of the Study:

• To characterize a colistin-resistant Acinetobacter junii clinical isolate.
• To investigate the phenotypic and genomic features associated with colistin resistance.
• To identify potential genetic mutations contributing to colistin resistance in this species.

Main Methods:

• Phenotypic analysis including colony morphology and bacterial suspension formation.
• Transmission electron microscopy to examine outer membrane structure.
• Comparative whole-genome sequencing and analysis of resistance-related genes.
• Growth rate determination to assess fitness cost.

Main Results:

• A colistin-resistant Acinetobacter junii isolate (AJ6079) was identified from a blood sample.
• AJ6079 displayed a dry colony phenotype, difficulty in suspension, and a thickened outer membrane.
• Genomic analysis revealed novel point mutations in PmrB, LpxA, and LpxD, potentially linked to colistin resistance.
• The resistant isolate exhibited a slower growth rate, indicating a potential fitness cost.

Conclusions:

• Novel point mutations in colistin-resistance-related genes may confer resistance in Acinetobacter junii.
• The colistin-resistant isolate shows phenotypic differences and a potential fitness cost.
• Further research is required to validate these findings and elucidate the precise mechanisms of colistin resistance.