Hotspots sequences of gyrA, gyrB, parC, and parE genes encoded for fluoroquinolones resistance from local Salmonella Typhi strains in Jakarta.

Background: Infection of Salmonella enterica subsp. enterica serovar Typhi is the primary etiology of typhoid fever globally and is common in many developing countries, especially those with dense populations and poor environmental sanitation. Antibiotic fluoroquinolones were used for the treatment in the 1980s due to the resistance to the first-line antibiotics. However, many cases of treatment failure of fluoroquinolones in typhoidal patients have been reported from numerous countries in Asia, Europe, Africa, and America. Mutations in quinolone resistance determining regions (QRDR) genes, gyrA, gyrB, parC, and parE, are found in fluoroquinolone-resistant Salmonella Typhi. Contrast reports came from the S. Typhi isolates in Indonesia, mainly Jakarta and the surroundings, obtained from patients with typhoid fever, with good sensitivity to the fluoroquinolones, i.e., nalidixic acid, ciprofloxacin, moxifloxacin, and levofloxacin. The present study, therefore, aimed to identify the hotspot sequences of gyrA, gyrB, parC, and parE genes of the local S. Typhi strains based on their susceptibility to fluoroquinolones from patients with typhoid fever in Jakarta and its satellite cities.

Results: A total of 28 isolates were identified as S. Typhi. All isolates were susceptible to nalidixic acid, levofloxacin, and moxifloxacin. Twenty-seven isolates (96.4%) were susceptible to ciprofloxacin, with one isolate (3.6%) being intermediate. The hotspot sequences of gyrA, gyrB, parC, and parE genes from all isolates were identical to the fluoroquinolone-sensitive reference sequence Salmonella enterica subsp. enterica serovar Typhi Ty2 (NCBI GenBank AE014613.1), including the isolate with intermediate susceptibility. The mutation was not found, and amino acid deduced from all hotspots in susceptible and intermediate isolates showed no replacement in all reported codons.

Conclusions: This study showed that the local S. Typhi strains from Jakarta and surroundings were susceptible to fluoroquinolones (nalidixic acid, ciprofloxacin, levofloxacin, and moxifloxacin), and the hotspot sequences of the gyrA, gyrB, parC, and parE genes were all identical to the reference sequence. Thus, the hotspot sequences of the gyrA, gyrB, parC, and parE genes seemingly were conserved in Jakarta's local S. Typhi strains and could be considered wild type. The phenotypic susceptibility was consistent with the genotypic characteristic without non-synonymous mutations associated with drug resistance.