Antibiotic-Resistant Phenotype and Genotype of S. suis serotype 2 (SS2) Isolated from Humans in Bali, Indonesia

Background: In recent times, meningitis, an infection primarily attributed to the zoonotic bacteria Streptococcus suis, has emerged as a significant public health concern in Bali, Indonesia. Their resistance to a multitude of antibiotics has emerged as a contemporary threat, as opposed to their virulence. There is a current lack of reported information regarding the genetic or phenotypic susceptibility pattern of S. suis to antibiotics in Bali. Objective: The objective of this research endeavor was to ascertain the antibiotic susceptibility pattern of S. suis isolates in Bali, either through phenotypic or genetic means. Methods: Glycerol stock isolates of S. suis from various specimen sources, including CSF, blood, and pleural fluid from April 2016 until April 2022 which had been assessed for species identification and antimicrobial susceptibility test (AST) using the VITEK 2 Compact (Biomeriuex®) were subjected to determine the serotype and antibiotic resistance genetically. Results: Successful isolation of sixty-six S. suis isolates occurred primarily from cerebrospinal fluid. The results demonstrated that all isolates exhibited phenotypic resistance to tetracycline, with one isolate (MKPNH0071) demonstrating co-resistance to tetracycline and erythromycin. It is additionally corroborated genetically through the amplification of the tetM gene in every isolate, including those that exhibited concurrent resistance to erythromycin and tetracycline. The intTn gene, a member of the conjugate transposon Tn916 family which plays a role as horizontal media gene transfer on plasmids for carrying the resistance genes ermB and tetM, was amplified in an isolate that exhibited tetracycline co-resistance with erythromycin (MKPNH0071). Conclusion: This research represents the initial investigation into the antibiotic resistance phenotype and genotype of S. suis serotype 2 (SS2) isolated from human subjects in Bali, Indonesia. Our findings suggest that the isolate of SS2 (MKPNH0071), which demonstrated tetracycline co-resistance with erythromycin, might be facilitated by the horizontal acquisition of the genetic element Tn916