Selection,Recombination, and Virulence Gene Diversity among Group B Streptococcal Genotypes

Transmission of group B Streptococcus (GBS) from mothers to neonates during childbirth is a leading cause of neonatal sepsis and meningitis. Although subtyping tools have identified specific GBS phylogenetic lineages that are important in neonatal disease, little is known about the genetic diversity of these lineages or the roles that recombination and selection play in the generation of emergent genotypes. Here, we examined genetic variation, selection, and recombination in seven multilocus sequence typing (MLST) loci from 94 invasive, colonizing, and bovine strains representing 38 GBS sequence types and performed DNA sequencing and PCR-based restriction fragment length polymorphism analysis of several putative virulence genes to identify gene content differences between genotypes. Despite the low level of diversity in the MLST loci, a neighbor net analysis revealed a variable range of genetic exchange among the seven clonal complexes (CCs) identified, suggesting that recombination is partly responsible for the diversity observed between genotypes. Recombination is also important for several virulence genes, as some gene alleles had evidence for lateral gene exchange across divergent genotypes. The CC-17 lineage, which is associated with neonatal disease, is relatively homogeneous and therefore appears to have diverged independently with an exclusive set of virulence characteristics. These data suggest that different GBS genetic backgrounds have distinct virulence gene profiles that may be important for disease pathogenesis. Such profiles could be used as markers for the rapid detection of strains with an increased propensity to cause neonatal disease and may be considered useful vaccine targets.Group B Streptococcus (GBS) is a leading cause of neonatal sepsis, pneumonia, and meningitis (51) and causes infections in pregnant women, nonpregnant adults, and the elderly with underlying medical conditions. Maternal GBS colonization is a main risk factor for neonatal disease, and roughly 20 to 40% of pregnant women are colonized (14, 23). Colonization rates of up to 31% and 34% have been documented in young men (4) and nonpregnant women (4, 42), respectively, whereas a rate of 22% has been observed in individuals over 65 years of age (18). GBS has also been identified as the cause of bovine mastitis in up to 45% of symptomatic bovines (30). Nine distinct polysaccharide capsule types (serotypes) are known, and the serotype distribution varies by population.The genetic diversity of GBS populations has been studied using a variety of different methods, including restriction fragment length polymorphism (RFLP) (24), ribotyping (5, 25), pulsed-field gel electrophoresis (49), multilocus enzyme electrophoresis (MLEE) (45), random amplification of polymorphic DNA (36), restriction digestion pattern (RDP) typing (53), and multilocus sequence typing (MLST) (28). By utilizing methods that focus on conserved genetic changes within GBS strains, virulent GBS clones that have diversified genetically can be identified. Both MLEE and MLST can distinguish the major GBS serotype III clones associated with neonatal invasive disease as sequence type 17 (ST-17) in the MLST system (28, 29, 38) or electrophoretic type 1 in the MLEE system (45). This clone is also evident in the RDP system as RDP-III (53).A recent study of 75 GBS strains representing different sources and STs reported that the ST-17 lineage is relatively homogeneous and contains a unique set of surface proteins (9). Homogeneity within a GBS lineage that is significantly associated with neonatal disease is likely important for disease pathogenesis, though few studies have been conducted to identify specific differences in virulence characteristics between lineages. Similarly, the roles of selection and recombination in the generation of STs, as well as known virulence genes, have only recently been explored and require further investigation (9a). Here, we assess the genomic diversity of GBS strains representing a variety of common clonal genotypes, examine evidence for selection and recombination, and evaluate the extent of DNA polymorphism and allelic variation in several putative virulence genes.     

秦岭东缘龙池曼华山松径向生长对多源数据气候因子的响应

全球变暖影响着树木的结构和功能,反之影响着树木生长对气候变化的响应。秦岭是我国南北方的分界线,同时也是亚热带气候和温带气候的过渡带,作为区域气候变化的敏感地带,已有许多学者在该地区开展树轮气候学研究。基于秦岭东缘伏牛山龙池曼顶部的华山松(Pinus armandii Franch.)树轮宽度建立了不同年表,分析该地区树木生长对嵩县站器测气象数据(SX)和格点气象数据(CHN)的响应。结果表明:(1)树轮差值年表(RES)的统计参数优于标准年表(STD),含有较丰富的环境信息,适于树轮气候学研究;(2)RES年表与SX器测数据和CHN格点数据的相关分析结果都表明,龙池曼顶部华山松径向生长受上一年的气候条件影响较大,且对气温的响应高于降水,与上年7-8月和当年1月的平均气温以及上年5月降水量呈显著负相关,与上年8月的降水呈显著正相关;(3)CHN格点数据能更全面地揭示月平均最高温对华山松径向生长的影响,RES年表对两个数据集当年夏季(7-9月)的降水量都呈负相关,但达到显著负相关的月份有差异;(4)多源气候数据均表明该地区存在暖干化趋势,升温不利于华山松的生长。若未来暖干化持续,秦岭东缘龙池曼地区华山松生长会进一步受限,从而影响该地区的森林植被生产力和固碳潜力。     

The infrageneric classification of biscutella (Cruciferae)

A brief historical taxonomic sketch ofBiscutella is given. Revisionary study of the genus throughout its geographic areas has led to an infrageneric classification. Two subgenera are recognized, one with two sections.     

Piloting Laboratory Quality System Management in Six Health Facilities in Nigeria

Background

Achieving accreditation in laboratories is a challenge in Nigeria like in most African countries. Nigeria adopted the World Health Organization Regional Office for Africa Stepwise Laboratory (Quality) Improvement Process Towards Accreditation (WHO/AFRO– SLIPTA) in 2010. We report on FHI360 effort and progress in piloting WHO-AFRO recognition and accreditation preparedness in six health facility laboratories in five different states of Nigeria.

Method

Laboratory assessments were conducted at baseline, follow up and exit using the WHO/AFRO– SLIPTA checklist. From the total percentage score obtained, the quality status of laboratories were classified using a zero to five star rating, based on the WHO/AFRO quality improvement stepwise approach. Major interventions include advocacy, capacity building, mentorship and quality improvement projects.

Results

At baseline audit, two of the laboratories attained 1- star while the remaining four were at 0- star. At follow up audit one lab was at 1- star, two at 3-star and three at 4-star. At exit audit, four labs were at 4- star, one at 3-star and one at 2-star rating. One laboratory dropped a ‘star’ at exit audit, while others consistently improved. The two weakest elements at baseline; internal audit (4%) and occurrence/incidence management (15%) improved significantly, with an exit score of 76% and 81% respectively. The elements facility and safety was the major strength across board throughout the audit exercise.

Conclusion

This effort resulted in measurable and positive impact on the laboratories. We recommend further improvement towards a formal international accreditation status and scale up of WHO/AFRO– SLIPTA implementation in Nigeria.     

Seasonal chemical composition, in vitro fermentation and in sacco dry matter degradation of four indigenous multipurpose tree species in Nigeria

A study was carried out to estimate the nutritive value of four indigenous multi-purpose tree (MPT) species (Enterolobium cyclocarpum, Treculia africana, Gliricidia sepium and Millettia griffoniana) by the evaluation of their seasonal chemical composition, in vitro fermentation and in sacco dry matter (DM) degradation. The main objective of the study was to assess the potential of these indigenous MPT in supplementing the feed of ruminant animals during the dry season when grasses are scarce and their quality generally fall short of animal requirements. Leaf samples were randomly collected from the trees for estimation of DM, crude protein (CP), ether extract (EE), ash, neutral detergent fibre (NDFom), acid detergent fibre (ADFom), lignin (sa), in vitro fermentation and in sacco DM degradation. Samples were collected three times to represent seasonal variations as follows: November: early dry; February: mid-dry and April: late dry seasons. All samples had high CP (160–199 g/kg DM) and moderate fibre concentrations (NDFom, 380–580 g/kg DM; ADFom, 290–400 g/kg DM and lignin (sa), 75–107 g/kg DM). T. africana recorded the highest (180–199 g/kg DM) (P<0.001) CP content throughout the seasons. The values obtained for the in vitro fermentation characteristics and in sacco DM degradation of these indigenous MPT indicated the presence of potentially degradable nutrients in the MPT. Data from this study showed that E. cyclocarpum, T. africana, G. sepium and M. griffoniana have potentials that could be harnessed as feed supplements for ruminant animal production in Nigeria during the dry season.     

Lessons from the Ebola epidemics and their applications for COVID‐19 pandemic response in sub‐Saharan Africa

COVID‐19, caused by a novel coronavirus named SARS‐CoV‐2, was identified in December 2019, in Wuhan, China. It was first confirmed in sub‐Saharan Africa in Nigeria on 27 February 2020 and has since spread quickly to all sub‐Saharan African countries, causing more than 111,309 confirmed cases and 2,498 deaths as of 03 June 2020. The lessons learned during the recent Ebola virus disease (EVD) outbreaks in some sub‐Saharan African countries were expected to shape and influence the region’s responses to COVID‐19 pandemic. However, some of the challenges associated with the management of the EVD outbreaks persist and create obstacles for the effective management of the COVID‐19 pandemic. This article describes the commonalities between the EVD epidemics and COVID‐19 pandemic, with a view to draw on lessons learned to effectively tackle the ongoing pandemic. Key successes, failures and lessons learned from previous EVD outbreaks are discussed. Recommendations on how these lessons can be translated to strengthen the COVID‐19 response in sub‐Saharan Africa are provided.     

Association of Group B Streptococcus Colonization and Bovine Exposure: A Prospective Cross-Sectional Cohort Study

Background

While Group B Streptococcus (GBS) human colonization and infection has long been suspected as originating from cows, several investigators have suggested that ongoing interspecies GBS transmission is unlikely due to genotyping data demonstrating that human and bovine-derived GBS strains represent mostly distinct populations. The possibility of ongoing transmission between humans and their livestock has not been systematically examined.

Methodology/Principal Findings

To examine ongoing interspecies transmission, we conducted a prospective cross-sectional cohort study of 68 families and their livestock. Stool specimens were collected from 154 people and 115 livestock; GBS was detected in 19 (12.3%) humans and 2 (1.7%) animals (bovine and sheep). Application of multilocus sequence typing (MLST) identified 8 sequence types (STs or clones), with STs 1 and 23 predominating. There were 11 families in which two members submitted stools and at least one had GBS colonization. In 3 of these families, both members (consisting of couples) were colonized, yielding a co-colonization rate of 27% (95% CI: 7%–61%). Two of these couples had strains with identical MLST, capsule (cps) genotype, susceptibility, and RAPD profiles. One couple co-colonized with ST-1 (cps5) strains also had a bovine colonized with the identical strain type. On multivariate analysis of questionnaire data, cattle exposure was a predictor of GBS colonization, with each unit increase in days of cattle exposure increasing the odds of colonization by 20% (P = 0.02). These results support interspecies transmission with additional evidence for transmission provided by the epidemiological association with cattle exposure.

Conclusions/Significance

Although GBS uncommonly colonizes livestock stools, increased frequency of cattle exposure was significantly associated with human colonization and one couple shared the same GBS strains as their bovine suggesting intraspecies transmission. These results set the framework for GBS as a possible zoonotic infection, which has significant public health implications.     

Thialysine-Resistant Mutant of SALMONELLA TYPHIMURIUM with a Lesion in the thrA Gene

A mutant of Salmonella typhimurium was selected for its spontaneous resistance to the lysine analog, thialysine (S-2-aminoethyl cysteine). This strain, JB585, exhibits a number of pleiotropic properties including a partial growth requirement for threonine, resistance to thiaisoleucine and azaleucine, excretion of lysine and valine, and inhibition of growth by methionine. Genetic studies show that these properties are caused by a single mutation in the thrA gene which encodes the threonine-controlled aspartokinase-homoserine dehydrogenase activities. Enzyme assays demonstrated that the aspartokinase activity is unstable and the threonine-controlled homoserine dehydrogenase activity absent in extracts prepared from the mutant. These results explain the growth inhibition by methionine because the remaining homoserine dehydrogenase isoenzyme would be repressed by methionine, causing a limitation for threonine. The partial growth requirement for threonine during growth in glucose minimal medium may also, by producing an isoleucine limitation, cause derepression of the isoleucine-valine enzymes and provide an explanation for both the valine excretion, and azaleucine and thiaisoleucine resistance. The overproduction of lysine may confer the thialysine resistance.     

Detection of Chlamydia trachomatis in pregnant women by the Papanicolaou technique, enzyme immunoassay and polymerase chain reaction

OBJECTIVE: To compare Papanicolaou staining, enzyme immunoassay (EIA) and the polymerase chain reaction (PCR) techniques for detecting Chlamydia trachomatis in pregnant women. STUDY DESIGN: Endocervical specimens were taken randomly from 125 pregnant women with or without symptoms. These women attended their first medical consultation at the Regional General Ignacio Zaragoza Hospital. Samples were analyzed for detection of C trachomatis. When results differed between tests, specimens were evaluated by direct immunofluorescence staining. RESULTS: The prevalence of chlamydial infection was 2.4%. The characteristics of patients positive for Chlamydia were: average age, 24 years; first sexual encounter at age 21 years, one partner and six to nine months of gestation. The sensitivity, specificity, accuracy, positive predictive values and negative predictive values were 100%, 99.18%, 99.20%, 75% and 100%, respectively, for Papanicolaou staining; 100%, 92.62%, 92%, 25% and 100% for EIA; and 100%, 100%, 100% and 100% for PCR. CONCLUSION: Both Papanicolaou staining and PCR were adequate for diagnosis of C trachomatis infection. EIA was not reliable and therefore is not recommended for use as a diagnostic technique in a pregnant population with low risk and low prevalence.