Objective To investigate the reason of persisting positive rapid plasma reagin (RPR) in serofast syphilis patients, and to provide reference for clinical treatment and prognosis.Methods A total of 33 serofast patients and 23 healthy controls were enrolled in this study.The percentages and absolute counts of CD3+, CD4+, CD8+ T lymphocytes and natural killer (NK) cells were detected by flow cytometry.The comparison of two groups was analyzed by independent sample t test, and the correlation between change of lymphocyte subgroups and RPR titer in serofast syphilis patients was analyzed by bivariate linear correlation method.Results Compared with healthy controls, the percentages of CD3+, CD8+ T lymphocytes in serofast syphilis group were both increased significantly (75.75±5.76)% vs (68.37±5.80)%, (t=4.69, P<0.01);(27.34±7.02)% vs (24.33±1.95)%, (t=2.34, P=0.025), while both the percentage and absolute count of NK cells were significantly decreased (7.32±4.48)% vs (14.87±6.26)%, (t=5.269, P<0.01);(136.2±83.4)/μL vs (298.8±166.9)/μL, (t=4.311, P<0.01).RPR titer of the patients was negatively correlated with both percentage and absolute count of CD4+ T lymphocytes (r=-0.476 and-0.515, respectively, both P<0.01), and it was positively correlated of CD8+ lymphocytes (r=0.588 and 0.305, P<0.01 and P=0.804).Conclusion The imbalance of immune response of lymphocyte subsets observed in serofast syphilis may explain the RPR titers change.

Air ; analysis ; Chromatography, Gas ; Propane ; analogs & derivatives ; analysis ; Reproducibility of Results ; Workplace

Objective To investigate the dynamic changes of transcription profiles of mouse thymus gene expression in different times after 6 Gy γ-irradiation.Methods High-flux cDNA microarray technique was used irradiation,the numbers and types of differentially expressed genes were gradually decreased,for instance,the induced differential expression genes were involved in cell cycle,immunity and stress,apeptosis,signal transduction,transcription regulation,DNA synthesis and recombination,cystoskeleton,ion channel and transportation,metabolism,protein translation and synthesis,development and cell differentiation,etc.correlated cell cycle(3 up-regulating:Cyclin G,Anxal,Fgf1 and 2 down-regulating:Cdc2a,Cdc25b),5 genes correlated immune stress(4 up-regulating:IL-18,Casp1,IL-15,IL-7 and 1 down-regulating:Cd28),7 genes correlated apoptosis(4 up-regulating:Caspl,Anxal,Perp,IL-7 and 3 down-regulating:Pten,Api5 and Fas).Conclusions After 6 Gy irradiation,differentially expressed genes in mouse thymus is not only involved in many targets,levels and pathways,but also displayed an obvious difference in times.This reveals the regular pattern of differential expression genes in the process of injury and reconstitution in moderate dose irradiated mouse thymus.

Objective To analyze the disease burden caused by occupational coal workers' pneumoconiosis (CWP) in Anhui Methods Province. A total of 1 649 patients with occupational CWP diagnosed in Anhui Province from 1950 to 2019 were selected as the study subjects using a retrospective study method. Age, gender, survival time, location, working age of disease onset, age of death, stage and date of diagnosis of CWP, comorbidities at the time of investigation, hospitalization and outpatient expenses in the past year, cost of absence from work, cost of absence from work of caregivers, and cost of nutrition and transportation were investigated. The years of life lost, years lived with disability (YLDs), disability adjusted life years (DALYs) Results and economic losses were calculated. Among these patients, 1 405 cases survived and 244 cases died. In the age range - - - of 20.0 70.0 years, the YLDs of surviving patients were 2.12 22.20 (8.19±3.59) person years. The YLDs of patients with disease vs - P complications was higher than that of patients without complications [(8.55±3.95) (7.87±3.21) person years, <0.01]. The total - - DALYs of the patients was 14 031.59 person years, and the average per capita DALYs was 8.51 person years. Its YLDs accounted for 82.0 % of the total DALYs. The total economic loss caused by CWP in the 1 405 surviving patients was 354.903 0 Conclusion million yuan, and the average per capita economic loss was 252 600 yuan. The disease burden caused by CWP is relatively high in Anhui Province. In addition to early detection, diagnosis and treatment, it is necessary to focus on prevention and treatment of CWP complications to reduce the disease burden.

AIM:To investigate the effect of ozone bath on the pathological changes and the expression of cyto-kines,platelet-derived growth factor (PDGF), transforming growth factor-β3(TGF-β3), and tumor necrosis factor-α (TNF-α),in the wounds of deep second-degree burns in rats. METHODS:Male clean-grade SD rats(n=80) were ran-domly divided into 2 groups, ozone bath group and routine dressing group (control group), with 40 rats in each group. Deep second-degree burn wound was established on the back of the rats,and then the examinations were conducted at 3 d, 7 d,14 d and 21 d after burn. For the routine dressing group,the wound was cleaned by normal saline and covered with io-dophor vaseline gauze every 2 d. For the ozone bath group,before the dressing,the rats were put into the clean foam box to accept ozone fumigation for 20 min(50 mg/L),and then accepted dressing change as the same as that in control group every 2 d. At each time point,the tissue specimens from these rat wounds(at wound center) were taken. The rats in ozone bath group received cleaning by saline cotton and then the ozone bath fumigation, while the rats in control group only re-ceived cleaning by saline. After that,the tissue specimens were taken again for HE staining,immunohistochemical staining and semiquantitative observation combined with image data analysis. The concentrations of the cytokines PDGF, TGF-β3 and TNF-α in the wound were measured by double-antibody sandwich ELISA. RESULTS:In ozone bath group, the wounds were smooth with clear edge and slight inflammatory reaction,swelling and exudation were weaker,and the wound healing rate was higher than that in control group with significant difference. Under microscopic observation with HE stai-ning,slighter inflammatory reaction in ozone bath group was observed than that in control group at each time point,and the numbers of fresh capillaries,fibroblasts and epithelial cells were significantly larger than those in control group. The ex-pression levels of PDGF and TGF-β3in the wound tissue homogenate in ozone bath group were higher,and the expression level of TNF-α was significantly lower than those in control group at each time point with significant difference. CONCLU-SION:The ozone bath therapy improves the local pathological changes and promotes the expression of cytokines PDGF and TGF-β3,which are associated with wound healing,as well as reduces the expression of inflammatory mediator TNF-α in the rats with deep second-degree burns,thus promoting the wound healing and anti-inflammatory responses.

BACKGROUNDAberrant DNA methylation plays a key role in human carcinogenesis. 5-aza-2'-deoxycytidine inhibits DNA methylation and induces the expression of genes putatively silenced by promoter methylation in vitro. There are few studies of the biological and clinical significance of 5-aza-2'-deoxycytidine in human hepatocellular carcinoma. This study explored the mechanism of 5-aza-2'-deoxycytidine targeting transcriptional repressor complexes affecting global gene expression in hepatocellular carcinoma cell line.

METHODSHigh density oligonucleotide gene expression microarrays were used to examine the effects of 5-aza-2'-deoxycytidine treatments on human hepatocellular carcinoma cell line SMMC-7721. The 5' ends of the genes upregulated or downregulated in this manner were compared with BLAST database to determine whether they might have promoter CpG islands. Flow cytometry was used to detect stages of the cell cycle and apoptosis of SMMC-7721 after being treated with 5-aza-2'-deoxycytidine.

RESULTSData obtained 3 days after 4 days of treatment with 5-aza-2'-deoxycytidine showed that more genes were induced in tumorigenic cells including genes that function in cell proliferation, differentiation, regulation of transcription, and cytokine signalling. Approximately 30% of induced genes did not have CpG islands within their 5' regions, suggesting that some genes activated by 5-aza-2'-deoxycytidine may not result from the direct inhibition of promoter methylation. This phenomenon may contribute to a number of upregulated genes involving regulation of transcription in the treated cell. Results showed that 100 micromol/L 5-aza-2'-deoxycytidine blocked cell cycle at S/G2-M phase increasing rate of apoptosis. Notably, we found differential expression of molecular action in the methylation although DNA methyltransferases did not show significant difference in the treated cell line.

CONCLUSION5-aza-2'-deoxycytidine could restore some silenced genes expression independently of DNA methylation inhibition and expression of DNA methyltransferases.

Antimetabolites, Antineoplastic ; pharmacology ; Apoptosis ; drug effects ; Azacitidine ; analogs & derivatives ; pharmacology ; Carcinoma, Hepatocellular ; drug therapy ; genetics ; pathology ; Cell Cycle ; drug effects ; Cell Line, Tumor ; CpG Islands ; DNA Modification Methylases ; genetics ; Gene Expression Regulation, Neoplastic ; drug effects ; Humans ; Liver Neoplasms ; drug therapy ; genetics ; pathology ; Transcriptional Activation

Objective: To investigate the effects and mechanism of diammonium glycyrrhizinate (DG) on liver injury in severely scalded rats. Methods: The experimental research method was used. Fifty-four female Sprague-Dawley rats aged 7-9 weeks were divided into sham injury group with simulated injury on the back, and simple scald group and scald+DG group with scald of 30% total body surface area on the back, with 18 rats in each group. Rats in sham injury group were not specially treated after injury, and rats in simple scald group and scald+DG group were rehydrated for antishock. Besides, rats in scald+DG group were injected intraperitoneally with 50 mg/kg DG at post injury hour (PIH) 1, 25, and 49. Rats in the three groups were collected, the serum content of liver function injury related indexes including aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), total protein, and albumin was measured by automatic biochemical assay analyzer, and serum content of ornithine carbamoyl transferase (OCT) was measured by enzyme-linked immunosorbent assay method at PIH 24, 48, and 72; hepatic histopathological changes at PIH 72 were observed by hematoxylin-eosin staining; the mRNA expressions of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), glucose regulated protein 78 (GRP78), activating transcription factor 4 (ATF4), and protein kinase R-like endoplasmic reticulum kinase (PERK) in liver tissue were detected by real-time fluorescent quantitative reverse transcription polymerase chain reaction at PIH 24, 48, and 72. The protein expressions of Bcl-2, Bax, GRP78, PERK, and ATF4 in liver tissue were detected by Western blotting at PIH 72 in sham injury group and PIH 24, 48, and 72 in simple scald group and scald+DG group. The number of samples was 6 in each group at each time point. Data were statistically analyzed with analysis of variance for factorial design, one-way analysis of variance, and Bonferroni test. Results: Compared with that in sham injury group, the serum content of AST, ALT, and LDH was significantly increased (P<0.01), and the serum content of total protein and albumin was significantly decreased (P<0.05 or P<0.01) of rats in simple scald group at all post-injury time points. Compared with those in simple scald group, the serum AST content of rats in scald+DG group at PIH 24 was decreased significantly (P<0.05); the serum AST, ALT, and LDH content of rats in scald+DG group at PIH 48 was decreased significantly (P<0.01), and the serum total protein content was increased significantly (P<0.01); the serum AST, ALT, and LDH content of rats in scald+DG group at PIH 72 was decreased significantly (P<0.01), and the serum total protein and albumin content was increased significantly (P<0.01). At PIH 24, 48, and 72, the serum OCT content of rats in simple scald group was (48.5±3.9), (40.8±2.4), and (38.7±2.0) U/L, which was significantly higher than (15.1±2.5), (15.7±2.6), and (16.4±3.7) U/L in sham injury group (P<0.01), and (39.0±4.5), (31.8±2.0), and (22.1±2.6) U/L in scald+DG group (P<0.05 or P<0.01). At PIH 72, the cells in liver tissue of rats in sham injury group had normal morphology and regular arrangement, with no obvious inflammatory cell infiltration; the cells in liver tissue of rats in simple scald group had disordered arrangement, diffuse steatosis, and moderate inflammatory cell infiltration; the cells in liver tissue of rats in scald+DG group arranged regularly, with scattered steatosis and a small amount of inflammatory cell infiltration. Compared with those in sham injury group, the Bcl-2 mRNA (P<0.05 or P<0.01) and protein expressions of liver tissue were significantly decreased, and the mRNA (P<0.01) and protein expressions of Bax were significantly increased in rats in simple scald group at PIH 24, 48, and 72. Compared with those in simple scald group, the mRNA (P<0.05) and protein expressions of Bax in liver tissue of rats in scald+DG group were decreased significantly at PIH 48; the mRNA (P<0.01) and protein expressions of Bax in liver tissue of rats in scald+DG group were significantly decreased, and the mRNA (P<0.01) and protein expressions of Bcl-2 were significantly increased at PIH 72. Compared with those in sham injury group, the mRNA (P<0.05 or P<0.01) and protein expressions of ATF4, GRP78, and PERK in liver tissue were significantly increased in rats in simple scald group at all post-injury time points. Compared with those in simple scald group, the mRNA (P<0.01) and protein expressions of ATF4 in liver tissue of rats in scald+DG group at PIH 48 were significantly decreased, and the mRNA (P<0.05 or P<0.01) and protein expressions of ATF4, GRP78, and PERK were significantly decreased in liver tissue of rats in scald+DG group at PIH 72. Conclusions: DG can effectively reduce the degree of liver injury in rats after severe scald, and the mechanism may involve alleviating endoplasmic reticulum stress and mitigating mitochondrial damage.
Albumins/pharmacology* ; Animals ; Burns/pathology* ; Female ; Glycyrrhizic Acid/pharmacology* ; Liver ; RNA, Messenger/genetics* ; Rats ; Rats, Sprague-Dawley ; bcl-2-Associated X Protein/pharmacology*

Objective To explore the association of nocturnal serum cortisol levels with diabetic microvascular complications in overweight or obese patients with type 2 diabetes mellitus. Methods Serum cortisol levels of 316 overweight or obese type 2 diabetic patients were tested at midnight by the method of chemiluminescence. Diabetic microvascular complications were compared among various groups according to nocturnal serum cortisol levels. All the patients with nocturnal serum cortisol level > 50 nmol/L were asked to undergo overnight low-dose dexamethasone suppression test to rule out the possibility of subclincal Cushing's syndrome. The incidences of diabetic nephropathy ( DN ) , diabetic retinopathy ( DR ) , and diabetic peripheral neuropathy ( DPN ) were examined in all the patients. Results (1)The incidence of DN was gradually increased from 13.3％to 27.7％and 44.2％in patients with low, medium, and high cortisol level groups, showing a statistical difference among 3 groups ( P<0.05) . The incidences of DR in medium and high cortisol level groups were higher than that in low cortisol level group (40.6％and 47.7％vs 22.7％, both P<0.01). The incidence of DPN in high cortisol level group was higher as compared with low cortisol level group (60.5％ vs 38.7％, P<0.01). (2) Nocturnal serum cortisol level in patients with diabetic microvascular complications was higher than that in patients without complications [ (136.87 ± 105.78 vs 97.55 ± 93.48) nmol/L, P<0.01]. Nocturnal serum cortisol level in patients with multiple diabetic microvascular complications was higher than that in patients with single diabetic microvascular complication [ (151.66±114.54vs117.69±90.26)nmol/L,P<0.05].(3)Singlefactorlogisticregressionanalysisshowedthat higher nocturnal serum cortisol level was a risk factor for diabetic microvascular complications in addition to female, age, longer diabetic duration, higher fasting plasma glucose ( FPG ) . Multivariate logistic regression analysis showed that higher nocturnal serum cortisol level was still a risk factor for diabetic microvascular complications after adjusted by diabetic duration, FPG, HbA1C, and the use of insulin (P=0.013). Conclusion Nocturnal serum cortisol level seems to be a risk factor for diabetic microvascular complications in overweight or obese patients with type 2 diabetes mellitus.

Objective: To investigate the effects and molecular mechanism of exogenous L-carnitine on hepatic pyroptosis mediated by excessive endoplasmic reticulum stress in severely scald rats. Methods: The experimental research method was adopted. According to the random number table (the same group method below), fifteen female Sprague Dawley rats aged 6-8 weeks were divided into sham-injury group, scald alone group, and scald+carnitine group (with 5 rats in each group), and full-thickness scald of 30% total body surface area were made on the back of rats in scald alone group and scald+carnitine group, and rats in scald+carnitine group were additionally given intraperitoneal injection of L-carnitine. At post injury hour (PIH) 72, The levels of aspartate aminotransferase (AST) and alanine dehydrogenase (ALT) of biochemical indicators of liver injury were detected by automatic biochemical analyzer with the sample number of 5. At PIH 72, liver tissue damage was detected by hematoxylin-eosin staining. At PIH 72, The mRNA levels of nucleotide-binding oligomerization domain-containing protein-like receptor family pyrin domain containing 3 (NLRP3), cysteine aspartic acid specific protease 1 (caspase-1), gasderminD (GSDMD), and interleukin 1β(IL-1β) in liver tissue as pyroptosis-related markers and glucose regulatory protein 78 (GRP78) and CCAAT/enhancer binding protein homologous protein (CHOP) in liver tissue as endoplasmic reticulum stress-related markers were detected by real-time fluorescence quantitative reverse transcription polymerase chain reaction (RT-qPCR). Protein expression levels of GRP78, CHOP, NLRP3, caspase-1, caspase-1/p20, GSDMD-N, and cleaved IL-1β in liver tissue were detected by Western blotting, and the sample numbers were all 5. HepG2 cells as human liver cancer cells were divided into dimethyl sulfoxide (DMSO) group, 0.1 μmol/L tunicamycin (TM) group, 0.2 μmol/L TM group, 0.4 μmol/L TM group, and 0.8 μmol/L TM group and were treated accordingly. After 24 h of culture, cell viability was detected by cell counting kit 8, and the intervention concentration of TM was screened, and the sample number was 5. HepG2 cells were divided into DMSO group, TM alone group, and TM+carnitine group, and treated accordingly. After 24 h of culture, the protein expression levels of GRP78, CHOP, NLRP3, caspase-1, caspase-1/p20, GSDMD-N, and cleaved IL-1β in cells were detected by Western blotting, and the sample numbers were all 3. Data were statistically analyzed with one-way analysis of variance and least significant difference-t test. Results: At PIH 72, the AST and ALT levels of serum in scald alone group were (640±22) and (157±8) U/L, which were significantly higher than (106±13) and (42±6) U/L in sham-injury group, respectively, with t values of -46.78 and -25.98, respectively, P<0.01. The AST and ALT levels of serum in scald+carnitine group were (519±50) and (121±10) U/L, which were significantly lower than those in scald alone group, respectively, with t values of 4.93 and 6.06, respectively, P<0.01. At PIH 72, the morphology of liver tissue of rats in sham-injury group were basically normal with no obvious inflammatory cell infiltration; compared with those in sham-injury group, the liver tissue of rats in scald alone group showed a large number of inflammatory cell infiltration and disturbed cell arrangement; compared with that in scald alone group, the liver tissue of rats in scald+carnitine group showed a small amount of inflammatory cell infiltration. At PIH 72, the mRNA expression on levels of NLRP3, caspase-1, GSDMD, and IL-1β in liver tissue of rats in scald alone group were significantly higher than those in sham-injury group (with t values of 34.42, 41.93, 30.17, and 15.68, respectively, P<0.01); the mRNA levels of NLRP3, caspase-1, GSDMD, and IL-1β in liver tissue of rats in scald+carnitine group were significantly lower than those in scald alone group (with t values of 34.40, 37.20, 19.95, and 7.88, respectively, P<0.01). At PIH 72, the protein expression levels of NLRP3, caspase-1, caspase-1/p20, GSDMD-N, and cleaved IL-1β in liver tissue of rats in scald alone group were significantly higher than those in sham-injury group (with t values of 12.28, 26.92, 5.20, 10.02, and 24.78, respectively, P<0.01); compared with those in scald alone group, the protein expression levels of NLRP3, caspase-1, caspase-1/p20, GSDMD-N, and cleaved IL-1β in liver tissue of rats in scald+carnitine group were significantly decreased (with t values of 10.99, 27.96, 12.69, 8.96, and 12.27, respectively, P<0.01). At PIH 72, the mRNA levels of GRP78 and CHOP in liver tissue of rats in scald alone group were significantly higher than those in sham-injury group (with t values of 21.00 and 16.52, respectively, P<0.01), and the mRNA levels of GRP78 and CHOP in liver tissue of rats in scald+carnitine group were significantly lower than those in scald alone group (with t values of 8.92 and 8.21, respectively, P<0.01); the protein expression levels of GRP78 and CHOP in liver tissue of rats in scald alone group were significantly higher than those in sham-injury group (with t values of 22.50 and 14.29, respectively, P<0.01), and the protein expression levels of GRP78 and CHOP in liver tissue of rats in scald+carnitine group were significantly lower than those in scald alone group (with t values of 14.29 and 5.33 respectively, P<0.01). After 24 h of culture, the cell survival rates of 0.1 μmol/L TM group, 0.2 μmol/L TM group, 0.4 μmol/L TM group, and 0.8 μmol/L TM group were significantly decreased than that in DMSO group (with t values of 4.90, 9.35, 18.64, and 25.09, respectively, P<0.01). Then 0.8 μmol/L was selected as the intervention concentration of TM. After 24 h of culture, compared with that in DMSO group, the protein expression levels of GRP78 and CHOP in cells in TM alone group were significantly increased (with t values of 10.48 and 17.67, respectively, P<0.01), and the protein expression levels of GRP78 and CHOP in TM+carnitine group were significantly lower than those in TM alone group (with t values of 8.08 and 13.23, respectively, P<0.05 or P<0.01). After 24 h of culture, compared with those in DMSO group, the protein expression levels of NLRP3 and GSDMD-N in cells in TM alone group were significantly increased (with t values of 13.44 and 27.51, respectively, P<0.01), but the protein expression levels of caspase-1, caspase-1/p20, and cleaved IL-1β in cells were not significantly changed (P>0.05); compared with that in TM alone group, the protein expression levels of NLRP3 and GSDMD-N in cells in TM+carnitine group were significantly decreased (with t values of 20.49 and 21.95, respectively, P<0.01), but the protein expression levels of caspase-1, caspase-1/p20, and cleaved IL-1β in cells were not significantly changed (P>0.05). Conclusions: In severely scald rats, exogenous L-carnitine may play a protective role against liver injury by inhibiting the pathways related to excessive endoplasmic reticulum stress-mediated pyroptosis.
Animals ; Burns ; Carnitine/pharmacology* ; Caspase 1/pharmacology* ; Dimethyl Sulfoxide/pharmacology* ; Endoplasmic Reticulum Stress ; Female ; Humans ; Liver ; NLR Family, Pyrin Domain-Containing 3 Protein ; Pyroptosis ; RNA, Messenger ; Rats ; Rats, Sprague-Dawley

Objective: To characterize the prevalence and genomic epidemiology of Vibrio parahaemolyticus from acute diarrheal patients in Shenzhen City from 2013 to 2021. Methods: Based on the Shenzhen Infectious Diarrhea Surveillance System, acute diarrheal patients were actively monitored in sentinel hospitals from 2013 to 2021. Whole-genome sequencing (WGS) of Vibrio parahaemolyticus isolates was performed, and the genomic population structure, serotypes, virulence genes and multilocus sequence typing were analyzed. Outbreak clusters from 2019 to 2021 were explored based on single-nucleotide polymorphism analysis. Results: A total of 48 623 acute diarrhea cases were monitored in 15 sentinel hospitals from 2013 to 2021, and 1 135 Vibrio parahaemolyticus strains were isolated, with a positive isolation rate of 2.3%. Qualified whole-genome sequencing data of 852 isolates were obtained. Eighty-nine serotypes, 21 known ST types and 5 new ST types were identified by sequence analysis, and 93.2% of strains were detected with toxin profile of tdh+trh-. 8 clonal groups (CGs) were captured, with CG3 as the absolute predominance, followed by CG189. The CG3 group was dominated by O3:K6 serotype and ST3 sequence type, while CG189 group was mainly O4:KUT, O4:K8 serotypes and ST189a and ST189 type. A total of 13 clusters were identified, containing 154 cases. About 30 outbreak clusters with 29 outbreak clusters caused by CG3 strains from 2019 to 2021. Conclusion: Vibrio parahaemolyticus is a major pathogen of acute infectious diarrhea in Shenzhen City, with diverse population structures. CG3 and CG189 have been prevalent and predominant in Shenzhen City for a long time. Scattered outbreaks and persistent sources of contamination ignored by traditional methods could be captured by WGS analysis. Tracing the source of epidemic clone groups and taking precise prevention and control measures are expected to significantly reduce the burden of diarrhea diseases caused by Vibrio parahaemolyticus infection in Shenzhen City.
Humans ; Vibrio parahaemolyticus/genetics* ; Diarrhea/epidemiology* ; Foodborne Diseases/epidemiology* ; Serogroup ; Genomics ; Dysentery ; Vibrio Infections/epidemiology* ; Serotyping