RAPD PCR detects co-colonisation of multiple group B streptococcus genotypes: A practical molecular technique for screening multiple colonies

Abstract

Group B Streptococcus (GBS) is a leading cause of neonatal meningitis, pneumonia, and sepsis. The biggest contributing factor of neonatal infections is due to vertical transmission from maternal colonisation of GBS in the genitourinary tract. Multiple serotype colonisation is often not investigated in epidemiological studies, but it is an important consideration for serotype-based vaccine development and implementation to ensure less abundant serotypes are not under-represented. In this study, we show that RAPD PCR is a quick tool useful in screening the presence of genetically different strains using multiple colony picks from a single patient swab. We observed a maximum of five different GBS strains colonising a single patient at a specific time.

Keywords: Co-colonisation; Genetic diversity; Group B Streptococcus; Multiple serotypes; RAPD PCR; S. agalactiae; Screening.

Fig. 1

Node plots of (A) serotype and (B) sequence type (ST) highlighting the co-colonisation pairings from 31 swabs that had two or more serotypes/ST present per swab. Six swabs with more than two serotypes/ST are shown by the purple, blue, light green, dark green, pink, and red lines representing the same swab in (A) and (B). The swab represented by the dark green line failed WGS DNA amplification and we were therefore unable to extrapolate ST data for one isolate. Grey lines represent the combinations of only two serotypes/ST during co-colonisation identified from the same swab. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

RAPD PCR typing results from two infant rectal swabs where genetic differences were identified through unique RAPD patterns. (A) Five unique RAPD patterns identified five STs and four serotypes amongst ten GBS isolates, lanes 1–5: 1 kb DNA ladder, GBS serotype reference strains NCTC 9993 (serotype Ia), NCTC 8187 (serotype Ib), NCTC 11080 (serotype III), and a negative water control (B) four unique RAPD patterns identified three serotypes and four STs.

Fig. 3

Distribution of the number of different RAPD patterns according to the anatomical origins of the 96 swabs. No statistical significance was observed when comparing between each anatomical site using an one-way ANOVA (p > 0.05).

Fig. 4

Multiple serotype colonisation of GBS from 96 rectovaginal/breastmilk/nasopharyngeal/rectal swabs originating from 21 mothers and 23 infants where serotype information was extrapolated from WGS. The circles represent the number of different serotypes cultured from each swab. The grey background represents maternal swabs, and the white background represent infant swabs. The swabs were taken at three different timepoints at day 0 (birth), day 6–9 and day 60–89 post-delivery of the infant. * = swab where there was at least one RAPD pattern that was not analysable by WGS. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)