Antimicrobial resistance of Salmonella enterica Typhi in the Western and Southern Regions of the Democratic Republic of the Congo: Phenotypic profile and molecular characterization of isolates associated with epidemics of Typhoid Fever

Abstract

Background: This study has its foundation following the emergence of the phenomenon of antimicrobial resistance of Salmonella enterica enterica Typhi associated with severe complications, such as intestinal perforations with a significant lethality. Objectives: Of this antimicrobial resistance, to determine the phenotypic profile, to detect the chromosomal molecular markers (CMMs) such as the class 1 integrons (intl-1) and ESBLs (blaTEM-1, blaOXA-1 and blaCTX-M-1) and to measure the association between the phenotypic profile and CMMs of typhoid isolates in concerned areas. Methods: Salmonella Typhi strains of typhoid epidemic areas were confirmed by serotyping tests. The antimicrobial susceptibility testing was conducted by disc diffusion method using the following commercial antimicrobials: Chloramphenicol-C, Ampicillin-AMP, Sulfamethoxazole-RL and Trimethoprim-W (former first-line antimicrobials), Ciprofloxacin-CIP or Cefotaxime-CTX, Ceftriaxone-CRO, Ceftazidime-CAZ (first-line antimicrobials), Tetracycline-TE, Amoxicillin-Potassium clavulanate-AMC, Nalidixic acid-NA, Cefoxitine-FOX, Gentamicin-CN (varied antimicrobials) and FEP-Cefepime (4GC). The phenotypic antimicrobial resistance profile was determined by Kirby-Bauer diffusion method on Mueller-Hinton agar. To perform the molecular characterization, the Salmonella Typhi isolates DNA has been extracted by Sigma Aldrich kit and the CMMs detection was performed by DNA Engine for PCR test. The association between phenotypic profile and CMMs has been measured by Pearson’s chi-square test. Results: Out of 320 Salmonella Typhi isolates, 50 were identified conform. The phenotypic profile of antimicrobial resistance was 59.5% in all the Western and Southern regions and 61% in the provinces of Kinshasa City and Bas-Congo to the former antimicrobials of first intention and the mean of CMMs rates were 22.5% and 27.4%, respectively. Those isolates showed a significant resistance profile to AMP, C and RL in those last two provinces. Conclusion: The rate of phenotypic multidrug-resistance of Salmonella Typhi isolates was more than 50% with the predominance of CMMs in Kinshasa and Bas-Congo. This study suggests to give up the use of AMP, C and RL in those two provinces. This may also indicate that the antimicrobial resistance surveillance system would be one strategy to manage food borne pathogens.