[The genetic features of drug resistance to group A streptococcus and macrolides antibiotics among pediatric patients in Beijing 2012].

OBJECTIVE: To investigate the genetic features of drug resistance to group A streptococcus(GAS) and macrolides antibiotics among pediatric patients in Beijing 2012. METHODS: 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). RESULTS: 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. CONCLUSION: 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.

[Application of EARS in early-warning of influenza pandemic in Beijing].

OBJECTIVE: To illustrate the efficiency of cumulative sum (CUSUM) in pre-warning of the influenza peak in Beijing. METHODS: CUSUM was used to analyze the data of influenza like illness (ILI), and the results of the influenza laboratory surveillance was regarded as the gold standard to judge the approaching of the influenza peak. RESULTS: The surveillance was launched in 421 hospitals in Beijing during the 2009 to 2010 influenza season, while the influenza laboratory surveillance was launched by 7 collaborative laboratories. From Jun. 2009 to Apr. 2010, the average ILI percentage in the 421 hospitals was 2.56%. In the study, 19 262 pharyngeal swab samples were collected from the ILI cases in 11 hospitals and 5 045 of them were tested positive for the influenza virus, with the novel swine-origin influenza A H1N1 virus dominating. After analyzing of the ILI surveillance data with CUSUM, it was found that the ILI surveillance in Beijing could make a satisfactory early warning for the approaching of the influenza peak referring to the gold standard based on the influenza laboratory results. CONCLUSION: It could give the prediction and early warning for the influenza peak efficiently and precisely, by using CUSUM to analyze the influenza surveillance data of Beijing.

[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].

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-urban 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-urban 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].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

[Comparisons of epidemiological and clinical characteristics in children with hand-foot-mouth disease caused by Enterovirus 71 and Coxackievirus A16].

OBJECTIVE: To compare the differences of epidemiological and clinical characteristics in children with hand-foot-mouth disease (HFMD) caused by Coxsackievirus A16 (CA16) and Enterovirus 71 (EV71). METHODS: The samples of vesicle fluid and throat swabs of 108 children with HFMD were collected and detected for enterovirus by RT-PCR. The clinical data of children with EV71 and CA16 infection were retrospectively reviewed and compared. RESULTS: The total positive rate of enterovirus was 97.2% (105/108). Of the 105 cases, 56 cases were positive for EV71 (51.9%), 39 cases were positive for CA16 (36.1%), 2 cases were positive for other enterovirus (1.9%), and 8 cases were co-infected by EV71 and CA16 (7.4%). There were no significant differences in age and sex between EV71 and CV16 infected cases. The univariate analysis showed that the incidences of herpes of mouth, erythra of knees, and nose running in children infected by CA16 were higher than in those infected by EV71. The multivariate logistic regression analysis showed that the HFMD children who had erythra of knees had higher probability of CA16 infection. CONCLUSIONS: EV71 should be considered as the pathogen in children with HFMD who have no herpes of mouth, erythra of knees, and nose running.

[Epidemiological characteristics and molecular typing of Salmonella in Beijing from 2008 to 2009].

OBJECTIVE: To study the epidemiological characteristics and molecular phenotypes of Salmonella by pulsed-field gel electrophoresis (PFGE) in Beijing from 2008 to 2009. METHODS: A total of one hundred thirty-seven isolates recovered from the WHO Global Salmonella Surveillance system and entero clinic surveillance system were identified by biochemical tests and serotyping. The related epidemiological informations were also analyzed. The isolates were further typed by PFGE. RESULTS: The prevalence of Salmonella from 2008 to 2009 showed obvious seasonal character. High incidence occurred from June to September, and 64.1% (84/131) isolates were recovered in this period. Patients of 18 - 40 year-old were 46.1% (58/128) and 80 patients were male and 40 patients were female with the ratio of 1.57:1. These 137 Salmonella isolates belonged to 20 serotypes, including Enteritidis (46.7%, 64/137) and Typhimurium (17.5%, 24/137) as the dominant serotype. In total, 71 PFGE profiles were identified. Four PFGE patterns of S. Enteritidis isolates (JEGX01.CN0001, JEGX01.CN0003, JEGX01.CN0002, JEGX01.CN0019) and S. Typhimurium pattern of JPXX01.CN0001 were dominant patterns. CONCLUSION: The prevalence of Salmonella from 2008 to 2009 showed distribution characteristics of sex, age and seasons. The numerous PFGE patterns of Salmonella showed diversity of these isolates and different clones existed in Beijing.

Serologic survey of pandemic influenza A (H1N1 2009) in Beijing, China.

OBJECTIVE: To examine the frequency and distribution of antibodies against pandemic influenza A (H1N1 2009) [H1N1] in populations in Beijing and elucidate influencing factors. METHODS: In January 2010, a randomized serologic survey of pandemic influenza A (H1N1 2009) was carried out. Six districts that were randomly selected with a total of 4601 participants involved in the survey have their antibody level tested by hemagglutination inhibition assay. RESULTS: Among the 4601 participants, the overall seropositive rate for pandemic influenza A (H1N1 2009) antibodies was 31.7%. The seropositivity prevalence in participants who received the pandemic H1N1 vaccination was 60.9%. Only 53.1% of the pandemic influenza A (H1N1 2009) seropositive individuals who had not received the vaccination experienced respiratory tract infection symptoms. Multivariate logistic regression revealed that factors such as age, occupation, dwelling type, whether the participant's family included students in school, and the vaccination history with pandemic influenza A (H1N1 2009) were associated with antibody titers (p<0.05). CONCLUSIONS: Our data indicated that almost 30.0% of the residents had appropriate antibody titers against pandemic influenza A (H1N1 2009) in Beijing, and these titers may provide an immune barrier.

[Etiological characteristics of influenza A (H1N1) 2009 virus in Beijing].

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.