The genetic features of drug resistance to group A streptococcus and macrolides antibiotics among pediatric patients in Beijing 2012 / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate the genetic features of drug resistance to group A streptococcus(GAS) and macrolides antibiotics among pediatric patients in Beijing 2012.</p><p><b>METHODS</b>A total of 199 strains of GAS were collected from 36 hospitals in Beijing between May and July, 2012. All strains were isolated from oropharyngeal swabs. The minimum inhibitory concentrations (MICs) of ten antibiotics (penicillin, ampicillin, erythromycin, clindamycin, tetracycline, levofloxacin, tigecycline, vancomycin, linezolid and streptogramin) were detected by VITEK-2 compact with GPS-67 test kit. The genes encoding macrolides resistance (ermA, ermB and mefA ) were amplified and tested by PCR. The macrolides resistant phenotype of group A streptococcus was detected by double disc test (D-test).</p><p><b>RESULTS</b>Among 199 strains of GAS collected in this study, 101(50.8%) were from suburbs and the other 98(49.2%) were from urban areas. 111(55.8%) strains were collected from scarlet fever patients while the other 88(44.2%) were from oropharyngeal infection cases. All the strains were sensitive to penicillin and ampicillin, and the percentage of resistance to erythromycin, clindamycin and tetracycline were 96.5% (192/199), 95.5% (190/199) and 92.0% (183/199), respectively. All strains were susceptible to levofloxacin, tigecycline, vancomycin, linezolid and streptogramin. The rates of resistance to erythromycin, clindamycin and tetracycline were different in different districts, however, the difference in it between ages and clinical diagnosis did not show statistical significance (P > 0.05) . The detected rate of drug resistance gene ermB was 98.5% (196/199). The gene ermA was only detected out in 5 strains and the gene mefA was not detected out. 199 strains showed A macrolides resistant phenotype cMLS, while the phenotype iMLS was not found in this study.</p><p><b>CONCLUSION</b>This study demonstrates the high level of clindamycin resistance in group A streptococcus collected from children in Beijing, 2012. The macrolides resistance of group A streptococcus was highly prevalent in Beijing, and the dominant phenotype was cMLS mediated by gene ermB.</p>

Analysis on the whole genome of the influenza H1N1 virus of the mild and severe cases in Beijing in 2009 / 中华预防医学杂志

<p><b>OBJECTIVE</b>To explore the characteristics of the whole genome of the influenza H1N1 virus of the mild and severe cases in Beijing.</p><p><b>METHODS</b>A total of 21 samples of throat swabs were collected from surveillance-designated hospitals between June and December in 2009, including 10 severe cases (4 death cases) and 11 mild cases. RNA of the virus were extracted,and the amplified primers of the whole genome were designed.Reverse transcription and PCR were performed to the RNA and then the PCR product was sequenced by software to analyze the evolution of the viral genes and the variation of the amino acids.</p><p><b>RESULTS</b>Compared with the reference vaccine strain A/California/07/2009 (H1N1), the genetic nucleotide homology in the eight segments of the pandemic H1N1 virus in Beijing in 2009 was higher than 99%, without significant variation. Among them,the genetic distance of hemagglutinin (HA), neuraminidase (NA) and nucleoprotein (NP) was comparatively far, separately 0.0050, 0.0040 and 0.0040.The gene of HA, P83S, the gene of NA, N248D, the gene of polymerase (PA), P224S and the gene of NP, V100I and L122Q were found to mutate in all the samples. Genes of HA, NA, NP, PA, PB 2 and nonstructural protein (NS1) in severe cases showed obviously clustered evolution. The mutation of gene S128P and S203T of HA, gene R269R and D547E of PA, gene T588I of PB 2 and gene I123V of NS mainly happened in severe cases, separately counting 6, 9, 6, 7, 9 and 6 cases. The relevance between the mutation happened in S203T of HA, R269K and D547E of PA and the severeness of the cases showed statistical significance (P < 0.05). The mutations of HA gene were mainly on the Ca and Cb antigene domains. No drug resistant mutation was found on NA gene but happened on matrix protein 2 (M2 gene). None of the mutations were found on the virulence related genes.</p><p><b>CONCLUSION</b>A high homology was found between the pandemic H1N1 virus in Beijing in 2009 and the reference vaccine strain A/California/07/2009(H1N1). Mutational sites related with the severe and fatal cases were found, but not the virulence related mutation.</p>

Characteristics and related factors related to the resistance on antibiotics among group A streptococcus strains isolated from children in Beijing, during May and July 2011 / 中华流行病学杂志

Objective To analyze the characteristics of antibiotic resistance on group A streptococcus isolated from pediatrics in Beijing in 2011,to provide reference for clinical drug administration.Methods Strains of group A streptococcus were collected from the Departments of Pediatrics in 36 hospitals at different Districts of Beijing,from May to July 2011.Minimal inhibitory concentrations (MIC) with ten antibiotics of these isolates were tested by VITEK 2 Compact method.All the Susceptibility rate (S％),Intermediate rate (I％) and Resistance rate (R％) were calculated according to their MIC values.The macrolides resistant phenotype of group A streptococcus was detected by D-test.Results A total of 633 (19.1％) group A streptococcus strains were cultured from 3315 throat swabs.All the isolates were susceptible to penicillin,ampicillin,streptogramin,linezolid,tigecycline,vancomycin,while 96.5％ (611/633) of the isolates were susceptible to levofloxacin.A total of the 96.1％ (608/633) isolates exhibited resistance to erythromycin.The resistance rates to clindamycin and tetracycline were 79.3％ (502/633)and 93.7％ (593/633),respectively.A total of 9 different resistant patterns were observed,with the dominant patterns as:concomitant resistance to erythromycin,clindamycin and tetracycline (72.7％,460/633),followed by combined resistance to erythromycin and tetracycline (18.0％,114/633).The most commonly seen macrolide resistant phenotype was cMLS type (83.2％).In total,97 strains belonged to iMLS type and 5 strains to M type.Data through multivariate logistic regression analysis showed that factors as occupation and samples being collected from the sub-unban areas etc.were significantly associated with the resistance rates to tetracycline and the odds ratio (95％CI) as 2.43 (1.16-5.09) and 2.35 (1.47-3.73).Isolates collected from the sub-unban areas were significantly associated with resistance rates to clindamycin,with the odds ratio (95％CI) being 0.48(0.25-0.92).Conclusion All the isolates acquired from the Pediatrics Departments in Beijing were susceptible to penicillin and ampicillin.The high resistance rates of erythromycin,clindamycin and tetracycline resistance to group A streptococcus were observed,with the major resistant phenotype as cMLS.Factors as occupation and the collection site of samples were significantly associated with the resistance rates to tetracycline while the sites of sample collection were significantly associated with the resistance rates to clindamycin.

Study on types of M protein gene in group A streptococcus isolated from children in Beijing, 2011 / 中华预防医学杂志

<p><b>OBJECTIVE</b>To explore the distribution characteristics of the types of M protein gene (emm) in group A streptococcus (GAS) isolated from children in Beijing in the year 2011.</p><p><b>METHODS</b>During May to July in 2011, a total of 3315 patients who were diagnosed scarlet fever or pharyngeal infection by doctors in pediatric outpatient and emergency units of 36 hospitals, were selected as subjects. Their throat swab samples were collected and isolated the strains of GAS. Gene emm was then amplified and sequenced by PCR method, and the differences in types of gene emm between different populations and diseases were compared.</p><p><b>RESULTS</b>A total of 633 strains of GAS were isolated from the 3315 throat swab samples, 610 strains out of which were gene emm positive and were recruited in the study. Out of the 610 recruited strains, 448 (73.4%) were isolated from scarlet fever patients, the other 162 (26.6%) were isolated from pharyngeal infection patients; 397 (65.1%) were from urban, the other 213 (34.9%) were from suburb; 240 (39.4%) were from patients aging between 1 - 5 years old, the other 369(60.6%) were from patients aging 6 - 18 years old. A total of 8 types of gene emm (scarlet fever: 6 types, pharyngeal infection: 4 types) and 21 subtypes of gene emn (scarlet fever: 16 subtypes, pharyngeal infection: 10 subtypes) were identified. Three new subtypes were found in the study, naming emm1.63, emm12.62 and st5144.20. Among them, emm1.63 was found both in scarlet fever and pharyngeal infection patients, while emm12.62 and st5144. 20 were only found in pharyngeal infection patients. Among all the types of gene-emm, emm12 accounted for the highest percentage as 80.5% (491/610) and then followed by emm1 (18.0% (110/610)). Among all the subtypes, the dominant subtype was emm12.00, accounting for 69.0% (421/610), following by emm1.00 (16.9% (103/610)) and emm12.19 (6.1% (37/610)). All the above types and subtypes of gene emm were the most prevalent strains in scarlet fever patients and pharyngeal infection patients. Significant differences in the distribution of prevalent strains were observed among various aging patients and regions. The constituent ratios of emm1, emm1.00 and emm12.19 were higher in patients from suburb (emm1: 22.1% (47/213), emm1.00: 19.2% (40/213), emm12.19: 8.0% (17/213)) than those in urban areas (emm1: 15.9% (63/397), emm1.00: 15.6% (62/397), emm12.19: 5.0% (20/397)). The difference showed statistical significance (P < 0.05). The constituent ratio of emm1.00 was higher among patients aging 6-18 years old (19.2% (71/369)) than those aging 1 - 5 years old (13.3% (32/240)). The difference also showed statistical significance (χ(2) = 8.45, P < 0.05).</p><p><b>CONCLUSION</b>Among the types of gene emm in GAS isolated from children in Beijing in year 2011, the most prevalent two were emm12 and emm1, and the most prevalent emm subtypes were emm12.00, emm1.00 and emm12.19. A significant difference in their distribution between various aging patients and isolated places can be obviously found.</p>

The significance of different sample types in study of pandemic A (H1N1) influenza diagnosis / 中华预防医学杂志

<p><b>OBJECTIVE</b>To explore the value of different types of samples, including throat swabs, stools, bloods in pandemic A (H1N1) influenza diagnosis and virus shedding patterns.</p><p><b>METHODS</b>From May to June in 2009, 135 samples were collected from 23 confirmed cases of pandemic influenza A (H1N1) infection, including 99 throat swabs, 14 stools, 11 bloods, 1 respiratory tract washing from 13 confirmed cases and 10 blood samples from other confirmed cases. The virus was detected by real-time RT-PCR, the antibody was detected by haemagglutination inhibition assay.</p><p><b>RESULTS</b>For 99 throat swabs of 13 patients, the median time of the first positive real-time RT-PCR was 1 day (ranged from 0 to 7 days) after the onset of the symptoms of illness; the median length of time duration of positive real-time RT-PCR results from throat swabs was 3 days (ranged from 1 to 15 days). Four cases intermittently released virus. One respiratory tract washing sample was positive. In 14 stools, 8 stools were real-time RT-PCR positive, the positive rate was 57.14%. The median time of the positive real-time RT-PCR was 3 days (ranged from 1 to 4 days) after the onset of the symptoms of illness. In 21 blood samples collected at 2 to 9 days of onset, 1 blood sample was real-time RT-PCR positive, the positive rate was 4.76%. All these 21 blood samples were antibody negative.</p><p><b>CONCLUSION</b>Throat swabs and stools samples can be used as A (H1N1) influenza early diagnosis. The length of time duration of positive real-time RT-PCR in throat swabs was longer than stool samples and intermittently releasing of virus were found in throat swabs. Influenza A H1N1 cases showed the presence of small amount of viremia and antibody was negative in early blood samples (< 9 days).</p>

Etiological characteristics of influenza A (H1N1) 2009 virus in Beijing / 中华流行病学杂志

Objective To analyze the results of detection on influenza A (H1N1) 2009 virus in Beijing from May 2009 to December 2009 and to understand the epidemiologic characteristics during the pandemic period. Methods The study was conducted from the May 1 to December 27,2009. A total of 101 852 throat swab samples were detected with the real-time RT-PCR assay by the Beijing Network Laboratory. Data was statistically analyzed. Results 9843 samples showed influenza A (H1N1) 2009 positive, with an overall positive rate as 9.66%. In terms of the positive rates, they were 2.85% from May to June, 3.32% from July to August and 8.35% from September to October. The peak month fell in November (29.67%) and December (24.33%). The positive rates among the following subpopulations were: 8.40% among the suspected cases, 4.75% among close contact cases, 11.46% among the influenza-like illness cases and 7.33% among the cluster cases with fever. Positive cases mainly fell in age groups 5-14 and 15-24. The ratio of male to female was 1.5:1.Conclusion During the pandemic period of influenza A (H1N1) 2009, positive cases gradually increased during May to November but slowly decreasing in December.