Phenotypic characterization and antimicrobial susceptibility profiles of <i>Vibrio cholerae</i> isolates during the October 2022 and January 2023 outbreak in North-Kivu province, The Democratic Republic of Congo
Authors: Kabangwa R. K. S. , Mulasi K. H. , Moyengo B. T. , Byamungu J. M. , Mobile P. K. 
Published: August 2023

Background: Cholera is an infectious disease characterized by severe watery diarrhea, frequently occurring in outbreaks which affects many communities in the Democratic Republic of the Congo (DRC). At the end of October 2022, a cholera outbreak was declared in the camp of internally displaced people (IDP) of Kanyaruchinya, 20 kilometers north of Goma, the provincial capital of the North-Kivu province in DRC, as well as in other IDP camps and settlements around the city of Goma. The aim of this study was to phenotypically characterize Vibrio cholerae isolates associated with this outbreak, and to determinate their antimicrobial susceptibility profiles.

Methodology: Between October 31, 2022 and January 31, 2023, faecal swab samples were collected into Cary-Blair medium from 1604 and 538 patients with clinical signs of cholera at the Kanyaruchinya IDP, and IDPs camps and settlements around the city of Goma, respectively. After enrichment in 1% alkaline peptone water, the samples were cultured on thiosulphate-citrate-bile salt-sucrose (TCBS) agar for isolation and phenotypic characterization of V. cholerae O1 using conventional biochemical tests and serotyping technique. Antimicrobial susceptibility of selected isolates was peformed to a panel of 8 antibiotics by the disk diffusion method in accordance with EUCAST and CLSI guidelines.

Results: Vibrio cholerae was cultured from 807 samples (50.3%) of 1604 patients from the Kanyaruchinya IDP, and from 206 samples (38.3%) of 538 patients around the city of Goma (p<0.01). All the V. cholerae isolates from the Kanyaruchinya IDP (807/807, 100.0%) were serotyped as V. cholerae O1 Inaba whereas 136 (66.0%), 67 (32.5%), and 3 (1.5%) V. cholerae O1 isolates from around Goma were serotyped as V. cholerae O1 Ogawa, V. cholerae O1 Inaba, and Hikojima respectively. Antimicrobial susceptibility test on 174 and 62 isolates selected randomly from the 807 and 206 V. cholerae isolates from the Kanyaruchinya IDP camp, and from around the city of Goma respectively, showed that all the tested V. cholerae O1 isolates were resistant to polymyxin and cotrimoxazole, while being susceptible to tetracycline and azithromycin. All tested V. cholerae O1 isolates from Kanyaruchinya IDP camp displayed a unique antimicrobial susceptibility profile characterized by resistance to ampicillin, cotrimoxazole and chloramphenicol, and susceptiblility to ciprofloxacin, norfloxacin, azithromycin, tetracycline and doxycycline. Their counterparts from settlements around the city of Goma displayed a more variable antimicrobial susceptibility profile.

Conclusion: Our results suggest that a single V. cholerae O1 Inaba clone probably caused the cholera outbreak in the Kanyaruchinya IDP camp, whereas during the same period, several V. cholerae clones (Ogawa, Inaba and Hikojima) were associated with the cholera outbreak around the city of Goma.