Showing papers by "Jim Gray published in 2001"

Reassortment In Vivo: Driving Force for Diversity of Human Rotavirus Strains Isolated in the United Kingdom between 1995 and 1999

Abstract: The G and P genotypes of 3,601 rotavirus strains collected in the United Kingdom between 1995 and 1999 were determined (M. Iturriza-Gomara et al., J. Clin. Microbiol. 38:4394–4401, 2000). In 95.4% of the strains the most common G and P combinations, G1P[8], G2P[4], G3P[8], and G4P[8], were found. A small but significant number (2%) of isolates from the remaining strains were reassortants of the most common cocirculating strains, e.g., G1P[4] and G2P[8]. Rotavirus G9P[6] and G9P[8] strains, which constituted 2.7% of all viruses, were genetically closely related in their G components, but the P components of the G9P[8] strains were very closely related to those of cocirculating strains of the more common G types (G1, G3, and G4). In conclusion, genetic interaction by reassortment among cocirculating rotaviruses is not a rare event and contributes significantly to their overall diversity.

Rotavirus epidemiology and surveillance.

Abstract: There is extensive antigenic and genomic diversity among co-circulating human rotaviruses. They are differentiated into groups, subgroups and types. There are at least 7 groups (A-G) and 4 subgroups within group A. To distinguish types within group A, a dual classification system has been established with the glycoprotein VP7 defining G types, and the protease-sensitive protein VP4 defining P types. At least 14 G types and more than 20 P types have been distinguished, of which at least 10 G types and at least 11 P types have been found in humans. Using the typing system, the complex molecular epidemiology of rotaviruses was investigated. Rotaviruses of different G and P types co-circulate. The main types found are G1P1A[8], G2P1B[4], G3P1A[8], G4P1A[8]; their relative incidence rates change over time in any one location and are different at the same time between different locations. Viruses with G/P constellations such as G1P1B[4] and G2P1A[8] are mostly natural reassortants of the co-circulating main virus types emerging after double infection of hosts. Viruses carrying G and or P types not represented in the four most common types, e.g. G8P[8], G1P[6] or G9P[6], could be introduced into the population by reassortment with animal viruses, or directly from animals or exotic human sources. Naturally circulating rotaviruses constantly undergo point mutations which can be used to classify lineages and sublineages within types. The full significance of human infections with group B and C rotaviruses remains to be established. Surveillance of rotavirus types in different parts of the world is essential to monitor the emergence of new types or of new G/P constellations which may predominate over time. The efficacy and effectiveness of any future rotavirus vaccine may differ depending on the predominant natural strain types. Detailed epidemiological and molecular surveillance data should be utilized to study the transmission dynamics of rotaviruses.

Amino Acid Substitution within the VP7 Protein of G2 Rotavirus Strains Associated with Failure To Serotype

Abstract: Rotavirus strains collected in the United Kingdom during the 1995-1996 season and genotyped as G2 by reverse transcription-PCR failed to serotype in enzyme-linked immunosorbent assays using three different G2-specific monoclonal antibodies. The deduced amino acid sequences of the antigenic regions A (amino acids 87 to 101), B (amino acids 142 to 152), and C (amino acids 208 to 221) of VP7 revealed that a substitution at position 96 (Asp→Asn) correlated with the change in ability to serotype these G2 strains.

Rapid screening technique for class 1 integrons in Enterobacteriaceae and nonfermenting gram-negative bacteria and its use in molecular epidemiology.

Abstract: A screening technique for integrons in members of the family Enterobacteriaceae and nonfermenting gram-negative bacteria by real-time PCR is reported. A total of 226 isolates of gram-negative bacteria obtained from a variety of clinical specimens were screened for class 1 integrons by real-time PCR performed on a LightCycler instrument. This technique used a primer pair specific for a 300-bp conserved region at the 5' ends of class 1 integrons. The screening assay was evaluated by comparison with results obtained by the conventional, thermal-block PCR (long PCR) by using established conditions and primers for the detection of class 1 integrons, and the real-time PCR technique was thus shown to be both sensitive and specific. DNA from 50 of 226 (22%) isolates screened was identified as containing an integron by the screening PCR, and sequence data were obtained across the integron for 34 of 50 (68%) of these isolates. In an attempt to study the molecular epidemiology of antimicrobial resistance genes carried within integrons, a comparison of the types of gene cassettes carried by isolates from different patients was made. Adenyltransferase genes conferring resistance to streptomycin and spectinomycin were the predominant gene cassettes amplified in the study. Resistance to trimethoprim was also frequently found to be encoded within integrons. Furthermore, multiple bacterial isolates obtained from one patient over a 5-month period were all shown to carry an integron containing the same single adenyltransferase gene cassette, suggesting that these elements were relatively stable in this case.

Rotavirus G and P genotypes in rural Ghana.

Abstract: An epidemiological study of rotavirus infection was conducted on specimens collected from patients with gastroenteritis and domiciled in the rural Upper Eastern Region of Ghana during 1998. Fifty isolates, randomly selected from 165 human group A rotavirus-positive samples, were G and P characterized by a reverse transcription (RT)-PCR assay using a seminested multiplex method. Rotaviruses of the G3 genotype were found to be the predominant strain (78%), followed by G2 (14%) and G1 (2%). Mixed infections, as shown by combinations of G3 and G2 (4%) and G3 and G1 (2%), were also observed. P typing showed P[4] (72.34%) to be the prevalent strain, followed by P[6] (21.3%), P[8] (2.13%), and a combination of P[4] and P[6] (4.3%).