Molecular characterization of group A human rotavirus among hospitalized children and adults in Bangladesh: finding of emerging G12 strain.

Between July 2004 and June 2006, a total of 1438 fecal samples were collected from Hospitalized children and adults with diarrhea at an Infectious Disease Hospital (SK Hospital) in Mymensingh, Bangladesh. The diversity of rotavirus strains were investigated using electropherotyping and reverse transcription-PCR amplification of the VP7 and VP4 genes. Group A rotavirus was detected in 171 of 1438(11.9%) specimens: 13.3%(72/543) from children 6 months to </=15 years of age and 11.0%(99/895) from individuals aged >15-76 years. The electrophoretic patterns of dsRNA of rotavirus showed 11 different migrations (7 long and 4 short) by polyacrylamide gel electrophoresis (PAGE). Representative 60 positive samples were selected for PCR genotyping. For the entire period, the common rotavirus G types G1 (27%), G2 (45%), and G9 (7%), comprised 79% of the strains, and common P types, P[4] (43%), P[6] (12%), and P [8] (20%), comprised 75% of the total P types. Of note, we detected a high percentage of unusual G-type P-type combination (11%) strains and specimens with mixed (10% G and 23% P) rotavirus infection with a variety of genomic constellation. Overall, the most frequent rotavirus strains were G2P[4] (36.7%) both in children and adults which were mostly associated with VP6 genotype I (subgroup I), and NSP4 genotype A or B, followed by G1P[8] (10.0%), G9P[8] (6.7%). G12 was detected for the first time in the study area and the detection rate was G12P[6] (3.4%), and G12P[4] (1.7%). The nucleotide sequence of VP7 gene was highly homologous among G12 strains isolated in Mymensingh suggesting recent emergence from a common ancestor. The study highlighted the diversity of rotaviruses isolated from children and adults. Due to the effect of antigenic diversity on rotavirus vaccines, it is important to continue careful monitoring of these strains as rotavirus vaccine programs are being implemented in Bangladesh.