Faecal excretion of Vibrio cholerae during convalescence of cholera patients in Calabar, Nigeria.

The pattern of faecal excretion of Vibrio cholerae was studied over a duration of eight months among 13 cholera convalescents by two-weekly surveillance cultures. Stools and rectal swabs were cultured on Thiosulphate citrate bile salts sucrose (TCBS) agar for the recovery of vibrio pathogens. Clinical phase and convalescent phase V. cholerae strains were compared for antibiogram profiles. The population of vibrios recovered from faecal inocula was usually scanty (<10(3) vibrios/g). All clinical isolates except three were concordant with convalescent phase strains. Sensitivity to tetracycline was uniform for concordant V. cholerae strains, with minimum inhibitory concentration (MIC) ranging from 0.54-4.0 microg/ml. Nine (69.2%) of the convalescents had positive faecal cultures for periods ranging from two weeks to more than seven months. Two adults whose excretions lasted several months also tested positive for human immuno-deficiency virus (HIV) infections. The significance of stool surveillance cultures for identifying asymptomatic infections among convalescents who may need chemotherapy to abolish excretion is emphasised. However, it could not be established with certainty if vibrios excreted during convalescence were from enteric colonization by the causative strains, or re-infections with the common strains in circulation.