Molecular characterization of streptococcus agalactiae isolated from pregnant women in the Eastern Cape, South Africa and Windhoek, Namibia and antibacterial activities of some medicinal plant extracts on the isolates

Abstract

Streptococcus agalactiae (S. agalactiae) also known as group B Streptococcus (GBS) is one of the leading causes of bacterial morbidity and mortality among neonates worldwide. It is the cause of invasive Early Onset Disease (EOD), which occurs in the first 7 days of life and characterised by sepsis, pneumonia and meningitis and Late Onset Disease (LOD) occurring between 7 and 89 days of life. Late onset disease is characterised by meningitis and long term neurological sequelae such as cerebral palsy, hearing impairment and cognitive challenges. S. agalactiae does not only infect neonates, it also infects the elderly, immunocompromised individuals and pregnant and non-pregnant women, causing invasive disease. In the world, 10-40 percent of healthy women are rectally or vaginally colonised with GBS and they face the risk of passing it to their babies during the process of childbirth. During parturition, a GBS colonized pregnant woman transfers the bacterium to her new-born as the baby passes through the ruptured membrane, thus infecting the child. However, GBS has been reported to be transferred even without rupture of membranes. Once it infects the membranes, it is transferred into the amniotic fluid and subsequently infects the baby. It can be aspirated into the lungs causing pneumonia or it can infect the blood stream and disseminated round the body causing septicaemia, meningitis and other infections. Once in the neonate’s body, the bacteria is able to evade the immune system as the host immune system is not yet fully developed. Bacterial evasion of the immune system is enhanced by its various virulence factors which are deployed to help it escape the immune system. These include the polysaccharide capsule, haemolysin and the release of complement inactivating factors such C5a peptidase. The World Health Organisation (WHO) (2010) recommends universal screening of pregnant women to identify those colonised and who are at risk of passing the bacterium to their babies during birth. WHO also recommends identification of at risk women and providing Intrapartum Antibiotic Prophylaxis (IAP) using penicillin. However, problems arise in penicillin allergic women and while alternatives for IAP include erythromycin and clindamycin, there is increasing resistance to these drugs thereby limiting therapeutic options. Antimicrobial susceptibility testing is also not always possible in most resource constrained countries due to poor infrastructure, limited access to health care and the logistical problems in implementing the WHO guidelines. Alternative therapeutic options to GBS infection include developing new and potent antibiotics, development of a vaccine, use of medicinal plants and the use of bacteriophage therapy. While these look like better alternatives there is massive scientific work to be carried out to ensure proper characterisation and efficiency of such alternatives. This process should be followed by in vitro diagnostic testing, experiments with animal models and clinical trials. The problems encountered during vaccine development to curtail GBS infection are compounded by the multiplicity of S. agalactiae capsular types which vary in different geographic locations. Medicinal plants are a cheap and convenient option since they are widely used in communities but the phytochemical components of the plants have to be identified and subjected to in vitro testing to evaluate their therapeutic efficacy as antimicrobial agents. This study therefore sought to isolate GBS from pregnant women between 35 and 37 weeks gestation in Windhoek (Namibia) and the Eastern Cape (South Africa), to determine the prevalence of GBS colonisation in the vagina and rectum of the pregnant women, characterise the isolates by molecular techniques, determine the antimicrobial resistance profiles and genes of the isolates and explore the efficacies of medicinal plant extracts as possible candidates for therapeutic options