Biomedical subjects

Diana R Martin

Publications and source records attributed to Diana R Martin.

5 recordsLinked to original sources

PubMed2005

Sequence variation in the porB gene from B:P1.4 meningococci causing New Zealand's epidemic.

Since mid-1991, New Zealand has experienced an epidemic of meningococcal disease. The epidemic has been caused by serogroup B meningococci expressing PorA type P1.7-2,4, belonging to the ST-41/ST-44 complex, lineage III. Most B:P1.7-2,4 meningococci express type 4 PorB (87.0%), although case isolates with porB other than type 4 have been identified throughout the duration of the epidemic. To assess the genetic relatedness of case isolates with an alternative porB gene, multilocus restriction typing validated against multilocus sequence typing was used. This determined that B:P1.7-2,4 meningococci with a porB gene that was other than type 4 had the same clonal origin. It was concluded that strains with alternative porB genes had diverged from the original type 4 porB. Variation in porB was also shown to be associated with the uptake of DNA encoding one or two of the PorB variable regions leading to mosaic porB. Point mutation rather than horizontal transfer and recombination was implicated as the mechanism of sequence variation in some strains. This work will serve as a reference point to determine if the administration of a strain-specific vaccine increases the level of porB divergence and variation already observed in New Zealand case isolates. It also complements the study undertaken of PorA stability which showed that variation in P1.7-2,4 PorA was almost exclusively due to deletions in the P1.4 epitope of the epidemic strain.

Amino Acid Sequence↗

PubMed2004

Evaluation of porB PCR-amplicon restriction endonuclease analysis as a method to determine porB variable-region sequences in nonserotypeable meningococci.

porB PCR-amplicon restriction endonuclease analysis is a rapid, simple method developed to assess porB variation in nonserotypeable meningococci isolated during New Zealand's epidemic of meningococcal disease. Most nonserotypeable meningococci isolated between 1990 and 1999 inclusively either were type 4 (40.5%) or contained the porB variable region 1 (VR1)-19, VR2-D, VR3-7, and VR4-14a sequences (45.1%).

Amino Acid Sequence↗

PubMed2004

Multilocus restriction typing method to predict the sequence type of meningococci.

A multilocus restriction typing (MLRT) method was developed to reduce the number of sequencing reactions required to determine the clonal relationships among serogroup B meningococci causing an epidemic in New Zealand. MLRT was a rapid, simple, and inexpensive method, and the results had an excellent correlation with multilocus sequence typing results.

Alleles↗

PubMed2002

Late antenatal carriage of group B Streptococcus by New Zealand women.

OBJECTIVES: To determine in New Zealand women the prevalence of group B Streptococcus (GBS) carriage late in pregnancy and to identify GBS colonisation risk factors, antibiotic susceptibility and serotype distribution. DESIGN: Prospective, observational study. SETTING: Community and hospital antenatal clinics in Wellington and Auckland during 1998-1999. SAMPLE: Convenience sample of 240 women between 35-37 weeks gestation. METHODS: Sociodemographic data, obstetric details and anogenital swabs were collected from each subject. Swabs were inoculated into selective media. GBS isolates underwent serotyping and antibiotic susceptibility testing. RESULTS: Two hundred and forty women (9% Maori, 11% Pacific) aged 15-41 years were recruited. Fifty-two (22%; 95% CI 17, 27) were colonised by GBS. Carriage was independently associated with younger age (59% < or = 30 years; adjusted OR 3.25; 95% CI 1.53, 6.95) and least social deprivation (57% NZ Dep 96 score +/- 3; adjusted OR 1.22; 95% CI 1.06,1.39). All GBS isolates were penicillin-susceptible, but resistance to clindamycin (15%) and erythromycin (7.5%) was detected and associated with serotype V strains. Predominant serotypes were: III (29%), Ia (21%), Ib (20%) and V (20%). CONCLUSIONS: Approximately 20% of New Zealand women carry GBS late in pregnancy, with young age a major risk factor. Increased risk in the socially advantaged, development of resistance to erythromycin and clindamycin, and emergence of new GBS serotypes are findings with important implications for prevention strategies requiring further confirmation.

Adolescent↗

PubMed2001

Extension of the Lancefield classification for group A streptococci by addition of 22 new M protein gene sequence types from clinical isolates: emm103 to emm124.

Classic M protein serotyping has been invaluable during the past 60 years for the determination of relationships between different group A streptococci (GAS) strains and the varied clinical manifestations inflicted by these organisms worldwide. Nonetheless, during the past 20 years, the difficulties of continued expansion of the serology-based Lancefield classification scheme for GAS have become increasingly apparent. By use of a less demanding sequence-based methodology that closely adheres to previously established strain criteria while being predictive of known M protein serotypes, we recently added types emm94-emm102 to the Lancefield scheme. Continued expansion by the addition of types emm103 to emm124 are now proposed. As with types emm94-emm102, each of these new emm types was represented by multiple independent isolates recovered from serious disease manifestations, each was M protein nontypeable with all typing sera stocks available to international GAS reference laboratories, and each demonstrated antiphagocytic properties in vitro by multiplying in normal human blood.

Antigens, Bacterial↗