Rapid identification of ST17 group B streptococcus using MALDI-TOF MS / 中华检验医学杂志

Objective:To establish a classification model for rapid identification of hypervirulent subtype ST17 clones of Group B Streptococcus (GBS) using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS).Methods:In a retrospective study, 235 strains of GBS strains were selected from multiple centers in China during 2015-2018. For model generation,45 strains of ST17 and 50 strains of non-ST17 (20 ST19, 15 ST12 and 15 ST10 strains) were enrolled as the modeling group. The remaining 90 main ST strains (40 ST17, 16 ST10, 17 ST12 and 17 ST19) were served as validation group. 50 GBS strains classified as other minor ST subtypes were regarded as taxonomic groups. MS spectra were collected by Bruker mass spectrometry, and then loaded for model generation and verification, and screening of differential peptide peaks by genetic algorithm (GA) and model verification on ClinProTools 3.0 software.Results:The recognition rate for ST17-GA model were 99.4% with cross validation value of 96.9%. Among the ten differential peptide peaks for the classification model, the weights of both two main peptide peaks m/z 2 956 and m/z 5 912 were greater than 1, while the weights of the all other eight peptide peaks were less than 0.5. Model validation showed only one of the ST17 was misjudged as non-ST17 strain, resulting in diagnostic accuracy of 98.9%, sensitivity of 97.5% and specificity of 100%, positive predictive value of 100% and negative predictive value of 98.0%, respectively. For other sporadic STs, 42.0% (21/50) of them were misdiagnosed as ST17 subtype.Conclusion:A MALDI-TOF MS classification model for hypervirulent subtype of ST17 GBS strains has been successfully established with good diagnostic efficacy.

Comparison of four screening methods for group B streptococcus / 中华检验医学杂志

Objective:To evaluate diagnostic performance of Todd-Hewitt (T-H) broth culture method, direct culture method, liquid chromogenic culture method, and loop-mediated isothermal amplification (LAMP) method for screening group B streptococcus (GBS) during late pregnancy.Methods:In the retrospective study, the rectal vaginal secretions samples were collected from pregnant women at 35 to 37 weeks at the obstetrics clinic of Guangzhou Women and Children′s Medical Center affiliated to Guangzhou Medical University during October 2016 to April 2018. For the purposes of clinical evaluation, T-H broth culture was used as the standard reference method, and double-blind trials were used to evaluate diagnostic performance of direct culture method, liquid chromogenic culture method, and LAMP method for screening group B streptococcus during late pregnancy in three research stages. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), coincidence rate and Yoden index for each method were calculated. Also, the level of agreement between each method and T-H broth was assessed using the kappa (k) coefficient.Results:A total of 969 specimens were detected by the T-H enrichment culture method, and 90 were positive (9.3%). The sensitivities from high to low were LAMP method [100% (25/25)], direct culture method [81.5% (22/27), 95 %CI:65.8%-97.1%], and liquid color culture method [71.1% (27/38), 95 %CI:55.9%-86.2%]. Specificities were direct culture method [100% (282/282)], liquid color culture method [98.1% (455/464), 95 %CI:96.8%-99.3%], and LAMP method [94.0% (125/133), 95 %CI: 89.9%-98.1%]. The coincidence rates were direct culture method [98.4% (22+282)/309], liquid color culture method [96.0% (27+455)/502], and LAMP method [94.9% (25+125)/158]. The Kappa values of the direct culture method (0.889), LAMP method (0.832) and the enrichment culture method were all ≥0.75, and that of the liquid color culture method was 0.708. The false negative rate of direct culture method was 18.5% (5/27), and no false negative case by LAMP method, but its false positive rate was 6.0% (8/133). The false negative rate and false positive rate of liquid color culture method were 28.9% (11/38) and 1.9% (9/464), respectively. Conclusions:Of the three screening methods compared in this study, only the LAMP method has the advantages in sensitivity, specificity, and coincidence rate compared with T-H enriched culture method, while the others have a certain degree of false negatives rate. The clinical laboratory can introduce these methods based on laboratory facilities and staffing, or refer to the European and American guidelines and combine the recommended antenatal GBS screening method with intrapartum nucleic acid amplification tests to best meet the clinical demands.

Comparison of four screening methods for group B streptococcus / 中华检验医学杂志

Objective@#To evaluate diagnostic performance of Todd-Hewitt (T-H) broth culture method, direct culture method, liquid chromogenic culture method, and loop-mediated isothermal amplification (LAMP) method for screening group B streptococcus (GBS) during late pregnancy.@*Methods@#In the retrospective study, the rectal vaginal secretions samples were collected from pregnant women at 35 to 37 weeks at the obstetrics clinic of Guangzhou Women and Children′s Medical Center affiliated to Guangzhou Medical University during October 2016 to April 2018. For the purposes of clinical evaluation, T-H broth culture was used as the standard reference method, and double-blind trials were used to evaluate diagnostic performance of direct culture method, liquid chromogenic culture method, and LAMP method for screening group B streptococcus during late pregnancy in three research stages. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), coincidence rate and Yoden index for each method were calculated. Also, the level of agreement between each method and T-H broth was assessed using the kappa (k) coefficient.@*Results@#A total of 969 specimens were detected by the T-H enrichment culture method, and 90 were positive (9.3%). The sensitivities from high to low were LAMP method [100% (25/25)], direct culture method [81.5% (22/27), 95%CI:65.8%-97.1%], and liquid color culture method [71.1% (27/38), 95%CI:55.9%-86.2%]. Specificities were direct culture method [100% (282/282)], liquid color culture method [98.1% (455/464), 95%CI:96.8%-99.3%], and LAMP method [94.0% (125/133), 95%CI: 89.9%-98.1%]. The coincidence rates were direct culture method [98.4% (22+282)/309], liquid color culture method [96.0% (27+455)/502], and LAMP method [94.9% (25+125)/158]. The Kappa values of the direct culture method (0.889), LAMP method (0.832) and the enrichment culture method were all ≥0.75, and that of the liquid color culture method was 0.708. The false negative rate of direct culture method was 18.5% (5/27), and no false negative case by LAMP method, but its false positive rate was 6.0% (8/133). The false negative rate and false positive rate of liquid color culture method were 28.9% (11/38) and 1.9% (9/464), respectively.@*Conclusions@#Of the three screening methods compared in this study, only the LAMP method has the advantages in sensitivity, specificity, and coincidence rate compared with T-H enriched culture method, while the others have a certain degree of false negatives rate. The clinical laboratory can introduce these methods based on laboratory facilities and staffing, or refer to the European and American guidelines and combine the recommended antenatal GBS screening method with intrapartum nucleic acid amplification tests to best meet the clinical demands.

Clinical analysis of 2 siblings with late-onset meningitis caused by group B streptococcus which were homogenous to the colonization bacteria of their mother / 中华实用儿科临床杂志

Objective To raise awareness of the late-onset meningitis caused by group B streptococcus (GBS) which was homogenous to the maternal colonization.Methods The clinical data of late-onset GBS meningitis in neonates twins whose pathogens were homogenous to their maternal colonization were collected from Department of Neonatology,Guangzhou Women and Children's Medical Center.The general conditions,clinical symptoms,laboratory tests and drug treatment of the twins and their mother were retrospectively analyzed,and the GBS homology during inpatient care was tested.And the progress of the twins' condition was investigated by telephone follow-up.Results The mother had two pregnancies without prenatal GBS screening or intrapartum antimicrobial intervention for GBS,everything was normal during pregnancy and delivery.Twins were born through cesarean section.The elder sister was discharged with Linezolid taken orally after 167 days in hospital without convulsions,shaking or other discomfort.The elder sister was followed up for every 2 weeks,and in the last time of follow-up,cerebrospinal fluid white blood cell counts were 45 × 106/L,protein level was 1.52 g/L and Linezolid was withdrawn.The younger brother was discharged after 58 days in hospital with follow-up for every 2 weeks,and in the last time of follow-up,cerebrospinal fluid white blood cell counts were 30 × 106/L,protein level was 0.66 g/L.During the hospitalization and follow-up without convulsions and irritation,and the cranial magnetic resonance imaging of the twin brother was normal.Test results showed that the GBS bacteria strain for twins and their mother were all serotype Ⅲ.The possibility of the GBS homology was more than 90％.Conclusions The toxicity of serotype Ⅲ GBS strain was strong.More proactive precautions should be considered to apply for the mother whose first birth already had GBS infection.Early identification and intervention of infection risk factors would help optimize the anti-infection treatment program and reduce nerve system damage and other adverse outcomes caused by invasive GBS infection.

Clinical analysis and serotypes distribution of neonatal purulent meningitis caused by group B streptococcus / 实用医学杂志

Objective To investigate the clinical characteristics,antibiotic susceptibilities and serotypes of Group B Streptococcus(GBS)isolated from neonatal meningitis to provide references for the prevention and treatment of neonatal GBS meningitis. Methods From June 2013 to June 2016,we surveyed the GBS strains iso-lated from purulent meningitis of < 90 days infants from Guangzhou Women and Children′s Medical Center. The GBS isolates were identified and the minimum inhibitory concentration of the antibiotics was determined by Vitek 2 Compact automatic bacterial identification system.GBS serotyping was performed using Strep-B-Latex?rapid latex agglutination test kit. Results A total of 46 cases of neonatal GBS meningitis,15 cases of early-onset infection and 31 cases of late-onset infection were diagnosed. 78.3% of GBS meningitis with varying degrees of complica-tions.Among 41 survivors with 3~24 months follow-up,50% of the early-onset and 44.8% of the late-onset GBS meningitis with varying degrees of neurological sequelae.Four capsular types were identified among the 46 isolates, serotype-Ⅲwas the most prevalent(73.9%),followed by Ib(19.6%),V(4.3%)and Ia(2.2%).All the isolates were susceptible to penicillins,cephalosporins,linezolid and vancomycin. Conclusion The highly pathogenic serotype-Ⅲ was the predominant serotype among neonatal GBS meningitis in Guangzhou,Therefore,it is neces-sary to strengthen the epidemiological surveillance of GBS invasive infection and the effective implementation of pre-ventive measures.

Interpretation of the guideline or consensus on screening strategy and detection methods for prevention of perinatal group B streptococcal infection in European and American countries / 中华检验医学杂志

Group B streptococcus ( GBS) is the most common cause of neonatal invasive infections in western countries , leading to severe pneumonia , sepsis and meningitis with high mortality and morbidity . Neonatal GBS infections are mainly transmitted from mother to baby .Since the end of 1990 s, prevention strategies of antenatal GBS screening and intrapartum antibiotic prophylaxis ( IAP) have been implemented by European and American area , decreasing the incidence of neonatal GBS disease significantly .The harm of GBS to neonates has been recognized and valued in recent years in China , but the authorized prevention measures are still lacking.Efficacy of IAP-based prevention depends on the accuracy of GBS screening results during pregnancy .Here, the GBS prevention guideline or consensus recommended by European and American CDC, including the screening strategies , detection methods, sample collection, storage and transportation were interpreted .

Deep sequencing of the T cell receptor Vb CDR3 repertoire of peripheral CD4+T cells in primary biliary cirrhosis / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To determine the immune repertoires of peripheral CD4+T cell receptor (TCR) Vb CDR3 in primary biliary cirrhosis (PBC) and analyze TCR diversity and preferred usage at sequence-level resolution.</p><p><b>METHODS</b>ARM-PCR and high-throughput sequencing were used to obtain millions of TCR Vb CDR3 sequences from peripheral CD4+T cells isolated from 7 patients with PBC and healthy volunteers. All sequencing data were analyzed, together with corresponding clinical information, by bioinformatic software. The Mann-Whitney U test was used for statistical analysis.</p><p><b>RESULTS</b>The PBC patients showed a lower level of diversity among the peripheral CD4+TCR Vb CDR3 than the healthy volunteers, and patients with higher level progression of the disease showed a greater lack of diversity. In addition, 4 specific preferred-usage amino acid sequences were discovered for the PBC patients: ASSFTGGPVEQY, ASSLISSGNNEQF, ATSRDTLAGGPGDTQY, and SASLEGNTEAF; these sequences were also found in higher frequencies in patients with later stages of PBC.</p><p><b>CONCLUSIONS</b>Decreased TCR Vb CDR3 diversities and specific preferred usage of TCR CDR3 sequences in peripheral CD4+T lymphocytes in PBC suggest that clonal expansion of a large number of CD4+T cells may be an important factor for PBC progression. These data provide a better understanding about the general characteristics of CD4+T cells in PBC patients and related to pathogenesis of the disease, and may provide useful insights into potential targets for immunotherapy.</p>

Evaluation of hepatic fibrosis using Aspartate aminotransferase-to-Platelet Ratio Index in children with biliary atresia / 中华检验医学杂志

Objective To investigate the correlation between the degree of liver fibrosis and Aspartate aminotransferase-to-Platelet Ratio Index ( APRI ) in children with biliary atresia ( BA ) , and evaluate the clinical significance of liver fibrosis in biliary atresia.Methods A total of 97 patients with diagnosed BA were recruited between January 2010 and June 2013.AST, PLT and APRI were determined one week before laparotomy.The severity of hepatic tibrosis was.Judged by Metavir system the correlation among AST, PLT, APRI and severity of liver fibrosis were evaluated, and their diagnostic value for degree of liver fibrosis was analyzed by ROC.Results Sera AST levels and PLT counts of BA patients were found to be positively(r=0.367, P<0.01) and negatively(r=-0.403, P<0.01) correlated with Metavir scores of liver fibrosis, respectively.There existed positive correlation between APRI and the severity of hepatic fibrosis (r=0.541, P<0.01).The area under ROC curve of APRI to diagnose none or mild fibrosis and moderately severe fibrosis was 0.78, with sensitivity of 77.9%and specificity of 62.1%at the optimal cut-off value of 0.75; the area under ROC curve of APRI to diagnose moderately severe fibrosis with liver cirrhosis arrived 0.85, with sensitivity of 75.0% and specificity of 89.4% at the optimal cut-off value of 1.77.The accuracy of none or mild fibrosis, moderate fibrosis and cirrhosis diagnosed by APRI were 73.2%, 64.9%, 87.6%, respectively.Conclusion APRI can be used as a non-invasive parameter to assess the severity of hepatic fibrosis with BA.