Modified use of real-time PCR detection of group B Streptococcus in pregnancy

Do NAAT-Based Methods Increase the Diagnostic Sensitivity of Streptococcus agalactiae Carriage Detection in Pregnant Women?

The aim of the study was to evaluate particular polymerase chain reaction primers targeting selected representative genes and the influence of a preincubation step in a selective broth on the sensitivity of group B Streptococcus (GBS) detection by nucleic acid amplification techniques (NAAT). Research samples were vaginal and rectal swabs collected in duplicate from 97 pregnant women. They were used for enrichment broth culture-based diagnostics, bacterial DNA isolation, and amplification, using primers based on species-specific 16S rRNA, atr and cfb genes. To assess the sensitivity of GBS detection, additional isolation of samples preincubated in Todd-Hewitt broth with colistin and nalidixic acid was performed and then subjected to amplification again. The introduction of the preincubation step increased the sensitivity of GBS detection by about 33-63%. Moreover, NAAT made it possible to identify GBS DNA in an additional six samples that were negative in culture. The highest number of true positive results compared to the culture was obtained with the atr gene primers, as compared to cfb and 16S rRNA primers. Isolation of bacterial DNA after preincubation in enrichment broth significantly increases the sensitivity of NAAT-based methods applied for the detection of GBS from vaginal and rectal swabs. In the case of the cfb gene, the use of an additional gene to ensure the appropriate results should be considered.

Group B Streptococcus among Pregnant Women and Neonates in Saudi Arabia: A Systemic Review

Sepsis caused by Group B Streptococcus (GBS) continues to cause mortality and morbidity in newborns, especially in developing countries. Bacterial sepsis in newborns varies nationally and even within countries. Developing countries have reported 34 deaths per 1000 live births compared to 5 in developed countries. This systemic review aimed to assess the prevalence of GBS colonization among pregnant women and the incidence of neonatal GBS sepsis in Saudi Arabia. A literature search of PubMed, MEDLINE Ovid, and Google Scholar was conducted. A total of 21 studies were found: 15 described maternal GBS colonization and 6 studies described neonatal GBS infections. The GBS colonization prevalence among pregnant women ranged from 2.1% to 32.8%. Inconsistencies in the reporting method for neonatal GBS infection rates were observed. Only two studies have the incidence of neonatal GBS as the primary outcome. No national multicenter studies exist on the GBS rates among neonates. Nationwide studies are warranted to assess the burden of GBS infections in neonates. These studies would guide appropriate GBS screening strategies during pregnancy for application in a national public health program.

Evaluation of Xpert GBS assay and Xpert GBS LB assay for detection of Streptococcus agalactiae

BACKGROUND

Group B Streptococcal (GBS) infection is the primary agent of neonatal morbidity and mortality. Rapid and simple methods to detect GBS are Xpert GBS and GBS LB assays based on real-time polymerase chain reaction (PCR). However, since the diagnostic accuracy of the two techniques in diagnosing GBS remains unclear, we designed this study to appraise the diagnostic accuracy of the aforementioned.

METHODS

A systematic search of all literature published before July 16, 2020 was conducted using Embase, PubMed, Web of Science, and Cochrane Library. The study quality was evaluated through Review Manager 5.3. Accordingly, data extracted in the included studies were analyzed using Meta-DiSc 1.4 and Stata 12.0 software. The diagnosis odds ratio (DOR) and bivariate boxplot were utilized to evaluate the heterogeneity. Publication bias was appraised by using Deeks' funnel plot.

RESULTS

A total of 13 studies were adopted and only 19 sets of data met the criteria. The sensitivity and specificity of Xpert GBS were 0.91 (95% CI 0.89-0.92) and 0.93 (95% CI 0.92-0.94). The area under the curve (AUC) was 0.9806. The sensitivity and specificity results of Xpert GBS LB were 0.96 (95% CI 0.95-0.98) and 0.94 (95% CI 0.92-0.95), respectively. The AUC was 0.9950. No publication bias was found.

CONCLUSIONS

The Xpert GBS and GBS LB assays are valuable alternative methods with high sensitivity and specificity. However, determining whether they can be used as clinical diagnostic standards for GBS is essential for the future.

Visual multiple cross displacement amplification for the rapid identification of S. agalactiae immediately from vaginal and rectal swabs

Streptococcus agalactiae (S. agalactiae) is an important pathogen that can lead to neonatus and mother infection. The current existing techniques for the identification of S. agalactiae are limited by accuracy, speed and high-cost. Therefore, a new multiple cross displacement amplification (MCDA) assay was developed for test of the target pathogen immediately from vaginal and rectal swabs. MCDA primers screening were conducted targeting S. agalactiae pcsB gene, and one set of MCDA primers with better rapidity and efficiency was selected for establishing the S. agalactiae-MCDA assay. As a result, the MCDA method could be completed at a constant temperature of 61 °C, without the requirement of special equipment. The detection limit is 250 fg (31.5 copies) per reaction, all S. agalactiae strains displayed positive results, but not for non-S. agalactiae strains. The visual MCDA assay detected 16 positive samples from 200 clinical specimen, which were also detected positive by enrichment/qPCR. While the CHROMagar culture detected 6 positive samples. Thus, the MCDA assay is prefer to enrichment/qPCR and culture for detecting S. agalactiae from clinical specimen. Particularly, the whole test of MCDA takes about 63.1 min, including sample collection (3 min), DNA preparation (15 min), MCDA reaction (45 min) and result reporting (6 s). In addition, the cost was very economic, with only US$ 4.9. These results indicated that our S. agalaciae-MCDA assay is a rapid, sensitive and cost-efficient technique for target pathogen detection, and is more suitable than conventional assays for an urgent detection, especially for 'on-site' laboratories and resource-constrained settings.

Raman microspectroscopy differentiates perinatal pathogens on ex vivo infected human fetal membrane tissues

Streptococcus agalactiae, also known as Group B Streptococcus (GBS), is a major cause of chorioamnionitis and neonatal sepsis. This study evaluates Raman spectroscopy (RS) to identify spectral characteristics of infection and differentiate GBS from Escherichia coli and Staphylococcus aureus during ex vivo infection of human fetal membrane tissues. Unique spectral features were identified from colonies grown on agar and infected fetal membrane tissues. Multinomial logistic regression analysis accurately identified GBS infected tissues with 100.0% sensitivity and 88.9% specificity. Together, these findings support further investigation into the use of RS as an emerging microbiologic diagnostic tool and intrapartum screening test for GBS carriage.

Outcome of a screening program for the prevention of neonatal early-onset group B Streptococcus infection: a population-based cohort study in Inner Mongolia, China

PURPOSE

Invasive early-onset group B Streptococcus infection (EOGBS) is an important cause of severe neonatal complications but study on comprehensive GBS screening is lacking in China. This study aims to investigate the outcome of a regional anterpartum screening program for EOGBS prevention and to estimate the pros and cons of a new GBS screening strategy employed.

METHODS

We performed an optimized hospital strategy for GBS screening, which targeted expectant mothers (including those with preterm births) from January 2016 to December 2016 in a population-based cohort. Three common screening strategies were simulated to estimate the availability of the hospital strategy used in this study.

RESULTS

Altogether, 9770 eligible women were tested and the rate of GBS carriage was 2.7  % (266/9770). In total, 198 of the 266 maternal GBS carriers accepted intrapartum antibiotic prophylaxis (IAP) treatment. Among the 9860 neonates of 9770 mothers, four cases of EOGBS infection were identified and one case was missed (EOGBS incidence with screening and IAP: 0.5/1000). Risk factors for maternal GBS colonization included preterm birth (between 35 and 37 weeks) [odds ratio (OR)=1.7 (95  % confidence interval: 1.22-2.33)], region of origin, resident areas, maternal age (older than 34 years) [OR=1.5 (1.06-2.09)], prelabour rupture of membranes [OR=1.8 (1.34-2.35)], gestational diabetes mellitus [OR=1.6 (1.14-2.28)] and maternal mild anemia (Hb: 90-110 g dl^-1) [OR=1.5 (1.16-2.06)]. This new screening strategy resulted in less antibiotic exposure and least number of cases missed.

CONCLUSIONS

Our findings illustrate that this perinatal screening (including preterm births) for prevention of EOGBS infection can be implemented in the Inner Mongolian area.