Abstract :
Cholera is a severe diarrheal illness caused by Vibrio cholerae, which produces
a virulence factor named El Tor hemolysin encoded by the hlyA gene.
Objectives: This study meant to analyze the phenotypic characteristics and presence of
hlyA gene in V. cholerae isolated from patients in Iran. The hlyA gene which codes for hemolysin,
plays an essential role in manifestation of cholera ,and could be used to diagnose
pathogenic V. cholerae El Tor O1 strains.
Patients and Methods: One hundred stool samples from the patients with cholera during
2002-2003 were collected from Tehran, Kashan, Kermanshah and Ahvaz cities, which
were subject to diagnostic tests. Serotyping, and antibiotic susceptibility tests were applied
and polymerase chain reaction (PCR) was also used to detect the hlyA gene.
Results: The group specific antisera identified the isolates as Ogawa, Inaba, Hikojima
and NAG (Non-agglutinable) in 74%, 3%, 0% and 23% of the isolates, respectively. Antibiotic
susceptibility test showed that all of the strains were sensitive to ciprofloxacin,
gentamycin and doxycyclin but the isolates showed resistance to sulfamethoxazole/trimethoprim
(74%), erythromycin (64%) and tetracycline (50%). V. cholerae El Tor isolates
were 100% positive for hlyA gene, but hemolysis phenotype characteristics were found
in 95% of the cases.
Conclusions:The results indicated that Ogawa serotype was identified as the dominant
serotype which revealed multiple antibiotic resistances to sulfamethoxazole/trimethoprim,
oxytetracycline, erythromycin, tetracycline and chloramphenicol. The presence
of hlyA gene in nonhemolytic strains of V. cholerae O1 biotype El Tor indicated that
some factors prevent expression of the hemolysin gene.
