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 durat ion of eight months among 13 cholera convalescents by two-weekly surveillan ce cultures. Stools and rectal swabs were cultured on Thiosulphate citrate bile salts sucrose (TCBS) agar for the recovery of vibrio pathogens. Clinic al phase and convalescent phase V. cholerae strains were compared for antib iogram profiles. The population of vibrios recovered from faecal inocula wa s usually scanty (<10(3) vibrios/g). All clinical isolates except three wer e concordant with convalescent phase strains. Sensitivity to tetracycline w as uniform for concordant V. cholerae strains, with minimum inhibitory conc entration (MIC) ranging from 0.5-4.0 mu g/ml. Nine (69.2%) of the convalesc ents had positive faecal cultures for periods ranging from two weeks to mor e than seven months. Two adults whose excretions lasted several months also tested positive for human immune-deficiency virus (HIV) infections. The si gnificance of stool surveillance cultures for identifying asymptomatic infe ctions among convalescents who may need chemotherapy to abolish excretion i s emphasised. However, it could not be established with certainty if vibrio s excreted during convalescence were from enteric colonization by the causa tive strains, or re-infections with the common strains in circulation.