Mohammed Mahbub Alam

Analysis on Distribution and Genomic Diversity of High-Level Antiseptic Resistance Genes qacA and qacB in Human Clinical Isolates of Staphylococcus aureus

High-level antiseptic resistance of Staphylococcus aureus is mediated by multidrug efflux pumps encoded by qacA and qacB genes. We investigated distribution and genomic diversity of these antiseptic resistance genes in a total of 522 clinical strains of S. aureus isolated recently in a Japanese hospital. The qacA/B gene was detected in 32.6% of methicillin-resistant S. aureus (MRSA) and 7.5% of methicillin-susceptible S. aureus (MSSA), whereas the low-level resistance gene smr, which was examined simultaneously, was detected at lower frequencies in both MRSA (3.3%) and MSSA (5.9%). Epidemiologic typing of S. aureus isolates suggested that higher prevalence of qacA/B in MRSA may be due to spread of a single predominant MRSA strain carrying qacA/B in the hospital. Restriction fragment length polymorphism (RFLP) analysis indicated higher prevalence of the qacB-type gene (59.3%) than the qacA-type gene (40.7%) among the qacA/B genes detected. Nucleotide sequencing analysis revealed the presence of two genetic variants in qacA (V1 and V2) and four variants in qacB (V1-V4) that differ from the qacA prototype in pSK1 by 1-5 nucleotides and 7-9 nucleotides, respectively. Although most strains with qacA-V1, qacA-V2, qacB-V3, and qacB-V4 showed high-level resistance to ethidium bromide (EB)(MIC > 100 microg/ml), all of the S. aureus isolates carrying qacB-V1 and qacB-V2 showed lower MICs of EB and some monovalent cationic antiseptic substances. By analysis of the genomic organization of the qacA/B downstream region, divergent forms of this region rearranged with an insertion of IS256 or IS257 were found primarily for qacB. The downstream region of qacA-V1 was suggested to be an evolutionary origin for other divergent forms. These findings indicated that both qacA and qacB are prevalent in recent clinical isolates, especially in MRSA, and these genes consist of variable genetic variants that may be responsible for different resistance levels against antiseptic substances.

Complete genome constellation of a caprine group A rotavirus strain reveals common evolution with ruminant and human rotavirus strains.

This study reports the first complete genome sequence of a caprine group A rotavirus (GAR) strain, GO34. The VP7-VP4-VP6-VP1-VP2-VP3-NSP1-NSP2-NSP3-NSP4-NSP5 genes of strain GO34, detected in Bangladesh, were assigned to the G6-P[1]-I2-R2-C2-M2-A11-N2-T6-E2-H3 genotypes, respectively. Strain GO34 was closely related to the VP4, VP6-7 and NSP4-5 genes of bovine GARs and the NSP1 gene of GO34 to an ovine GAR. Strain GO34 shared low nucleotide sequence identities (<90 %) with VP2-3 genes of other GARs, and was equally related to NSP3 genes of human, ruminant and camelid strains. The VP1, VP6 and NSP2 genes of strain GO34 also exhibited a close genetic relatedness to human G2, G6, G8 and G12 DS-1-like GARs, whereas the NSP1 of GO34 was also closely related to human G6P[14] strains. All these findings point to a common evolutionary origin of GO34 and bovine, ovine, antelope, guanaco and human G6P[14] GARs, although phylogenetically GO34 is not particularly closely related to any other rotavirus strains known to date.

Phylogenetic analysis of rotaviruses with genotypes G1, G2, G9 and G12 in Bangladesh: evidence for a close relationship between rotaviruses from children and adults

To clarify the phylogenetic relatedness of rotaviruses causing gastroenteritis in children and adults, an epidemiologic investigation was conducted in Mymensingh, Bangladesh, during the period between July 2004 and June 2006. A total of 2,540 stool specimens from diarrheal patients from three hospitals were analyzed. Overall, rotavirus-positive rates in children and adults were 26.4 and 10.1%, respectively. Among the 155 rotavirus specimens examined genetically from both children and adults, the most frequent G genotype was G2 (detection rate: 54.0 and 47.6%, respectively), followed by G1 (21.2 and 26.2%, respectively), and G9 (15.9 and 9.5%, respectively). G12 was also detected in five specimens (3.2% in total; four children and one adult). Sequence identities of VP7 genes of G2 rotaviruses from children and adults were higher than 97.8%, while these Bangladeshi G2 viruses showed generally lower identities to G2 rotaviruses reported elsewhere in the world, except for some strains reported in African countries. Similarly, extremely high sequence identities between children and adults were observed for VP7 genes of G1, G9 and G12 rotaviruses, and also for the VP4 genes of P[4], P[6], and P[8] viruses. Rotaviruses from children and adults detected in this study were included in a single cluster in phylogenetic dendrograms of VP7 or VP4 genes of individual G/P types. Rotaviruses with two emerging types, G9 and G12, had VP7 genes that were phylogenetically close to those of individual G-types recently reported in Bangladesh and India and were included in the globally spreading lineages of these G-types. These findings suggested that genetically identical rotaviruses, including those with the emerging types G9 and G12, were circulating among children and adults in city and rural areas of Bangladesh.

Whole genomic characterization of a human rotavirus strain B219 belonging to a novel group of the genus rotavirus

Novel rotavirus strains B219 and ADRV‐N derived from adult diarrheal cases in Bangladesh and China, respectively, are considered to belong to a novel rotavirus group (species) distinct from groups A, B, and C, by genetic analysis of five viral genes encoding VP6, VP7, NSP1, NSP2, and NSP3. In this study, the nucleotide sequences of the remaining six B219 gene segments encoding VP1, VP2, VP3, VP4, NSP4, and NSP5 were determined. The nucleotide sequences of the group B human rotavirus VP1 and VP3 genes were also determined in order to compare the whole genome of B219 with those of group A, B, and C rotavirus genomes. The nucleotide and deduced amino acid sequences of all B219 gene segments showed considerable identity to the ADRV‐N (strain J19) sequences (87.7–94.3% and 88.7–98.7%, respectively). In contrast, sequence identity to groups A–C rotavirus genes was less than 61%. However, functionally important domains and structural characteristics in VP1‐VP4, NSP4, and NSP5, which are conserved in group A, B, or C rotaviruses, were also found in the deduced amino acid sequences of the B219 proteins. Hence, the basic structures of all B219 viral proteins are considered to be similar to those of the known rotavirus groups. J. Med. Virol. 80:2023–2033, 2008.

Full genomic analyses of two human G2P[4] rotavirus strains detected in 2005: identification of a caprine-like VP3 gene.

Although G2P[4] rotaviruses are common causes of infantile diarrhoea, to date only the full genomes of the prototype (strain DS-1) and another old strain, TB-Chen, have been analysed. We report here the full genomic analyses of two Bangladeshi G2P[4] strains, MMC6 and MMC88, detected in 2005. Both the strains exhibited a DS-1-like genotype constellation. Excluding the VP4 and VP7 genes, and except for VP3 of MMC88, the MMC strains were genetically more closely related to the contemporary G2P[4] and several non-G2P[4] human strains than the prototype G2P[4] strain. However, by phylogenetic analyses, the VP2, VP3 (except MMC88), NSP1 and NSP3-5 genes of these strains appeared to share a common origin with those of the prototype strain, whilst their VP1, VP6 and NSP2 genes clustered near a caprine strain. The VP3 gene of MMC88 exhibited maximum relatedness to a local caprine strain, representing the first reported human G2P[4] strain with a gene of animal origin.

Analysis of genetic diversity and molecular evolution of human group B rotaviruses based on whole genome segments

Group B rotavirus (GBR) is a rare enteric pathogen that causes severe diarrhoea, primarily in adults. Nearly full-length sequences of all 11 RNA segments were determined for human GBRs detected recently in India (IDH-084 in 2007, IC-008 in 2008), Bangladesh (Bang117 in 2003) and Myanmar (MMR-B1 in 2007), and analysed phylogenetically with the sequence data of GBRs reported previously. All RNA segments of GBR strains from India, Bangladesh and Myanmar showed >95 % nucleotide sequence identities. Among the 11 RNA segments, the VP6 and NSP2 genes showed the highest identities (>98 %), whilst the lowest identities were observed in the NSP4 gene (96.1 %), NSP5 gene (95.6 %) and VP8*-encoding region of the VP4 gene (95.9 %). Divergent or conserved regions in the deduced amino acid sequences of GBR VP1-VP4 and NSP1-NSP5 were similar to those in group A rotaviruses (GARs), and the functionally important motifs and structural characteristics in viral proteins known for GAR were conserved in all of the human GBRs. These findings suggest that, whilst the degree of genetic evolution may be dependent on each RNA segment, human GBR may have been evolving in a similar manner to GAR, associated with the similar functional roles of individual viral proteins.

Characterization of full-length VP4 genes of OP354-like P[8] human rotavirus strains detected in Bangladesh representing a novel P[8] subtype

The G1 and G9 rotavirus strains MMC71 and MMC38 (subgroup II, NSP4 genogroup B), respectively, isolated from children in Bangladesh, were analyzed genetically. Full-length VP4 genes of these strains had 98.9% identity to each other and showed 83.9–89.4% identity to those of the P[4] and P[8] rotaviruses. Phylogenetic analysis of VP4 nucleotide sequences revealed that strains MMC38 and MMC71 were located in a lineage of P[8] strains. However, the cluster was highly divergent from the previously established P[8] strains. The VP8* portions of strains MMC38 and MMC71 showed more than 93.9% nucleotide sequence identity to OP354-like P[8] strains, and these strains were clustered into the same lineage. These findings indicate that the VP4 of these strains should be classified into a subtype of the P[8] genotype (P[8]b) that is distinct from that of common P[8] rotaviruses (P[8]a).

Genomic Rearrangement of the mec Regulator Region Mediated by Insertion of IS431 in Methicillin-Resistant Staphylococci

ABSTRACT Genomic diversification of the mec regulator region mediated by IS431 was investigated for clinical isolates of methicillin-resistant staphylococci. A single rearranged form of themecR1 gene due to IS431 insertion was detected in the three staphylococcal species, while another type ofmecR1 truncation with IS431 and an IS431 located downstream of mecI were found only in Staphylococcus haemolyticus. Genetic differentiation of IS431 and staphylococcal isolates suggested transmission of mecDNA with IS431-mediated rearrangement among different staphylococcal species.