Penetration of erythromycin through Staphylococcus epidermidis biofilm / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The catheter related infection caused by Staphylococcus epidermidis biofilm is increasing and difficult to treat by antimicrobial chemotherapy. The properties of biofilms that give rise to antibiotic resistance are only partially understood. This study aimed to elucidate the penetration of erythromycin through Staphylococcus epidermidis biofilm.</p><p><b>METHODS</b>The penetration ratio of erythromycin through Staphylococcus epidermidis biofilms of 1457, 1457-msrA, and wild isolate S68 was detected by biofilm penetration model at different time points according to the standard regression curve. The RNA/DNA ratio and the cell density within the biofilms were observed by confocal laser microscope and transmission electromicroscope, respectively.</p><p><b>RESULTS</b>The penetration ratios of erythromycin through the biofilms of 1457, 1457-msrA, and S68 after cultivation for 36 hours were 0.93, 0.55 and 0.4, respectively. The erythromycin penetration ratio through 1457 biofilm (0.58 after 8 hours) was higher than that through the other two (0.499 and 0.31 after 24 hours). Lower growth rate of the cells in biofilm was shown, with reduction of RNA/DNA proportion observed by confocal laser microscope through acridine orange stain. Compared with the control group observed by transmission electrmicroscope, the cell density of biofilm air face was lower than that of agar face, with more cell debris.</p><p><b>CONCLUSIONS</b>Erythromycin could penetrate to the Staphylococcus epidermidis biofilm, but could not kill the cells thoroughly. The lower growth rate of the cells within biofilm could help decreasing the erythromycin susceptibility.</p>

Study on the molecular epidemiological characteristics of norovirus in acute gastroenteritis of Beijing / 中华流行病学杂志

<p><b>OBJECTIVE</b>To study the prevalence, genotypes and molecular characteristics of norovirus (NoV) in acute gastroenteritis.</p><p><b>METHODS</b>RT-PCR was used to determine the molecular epidemiology of NoV.</p><p><b>RESULTS</b>Out of 685 samples, 66 positive specimens were identified and the prevalence was 9.6% (66/685), 9.9% in males and 9.4% in females, respectively, with no significant difference. The prevalence rates showed no differences between age groups or between inpatients and outpatients. NoV gastroenteritis did not present any seasonal distribution. 43 out of the 66 specimens were classified, with 10 (22.7%) belonged to GI including 2 GI.3, 1 GI.4, 4 GI.5 and 3 GI.7. Other 33 (77.3%) belonged to GII genogroup, including GII.4 accounted for 60.6% (20/33) and followed by 7 GII.12, 2 GII.6, 1 GII.2, 1 GII.3, 1 GII.5. Six specimens mixed with GI and GII and 3 specimens were classified as GI.3/GII.7, GI.5/GII.5 and GI.4/GII.4.</p><p><b>CONCLUSION</b>The main symptoms of acute gastroenteritis were abdominal pain, nausea, vomit and fever. There were many genotypes identified in our study and the main genotypes were GII.4/2006a and 2006b. GI and GII could be coinfected with each other.</p>

Viral shedding in Chinese young adults with mild 2009 H1N1 influenza / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The duration of viral shedding and the transmission of 2009 H1N1 influenza among individuals, especially among the younger population with mild illness, are not well understood now. The aim of this study was to determine the viral shedding of the young adult patients with mild 2009 H1N1 influenza in China.</p><p><b>METHODS</b>From September 2009 to January 2010, the clinical data and serial nasopharyngeal swabs of 67 patients with 2009 H1N1 influenza and 37 patients with seasonal influenza aged from 18 years to 35 years were collected. The nasopharyngeal swab samples were detected by real time RT-PCR to determine the viral shedding. All the patients did not receive the antiviral therapy but Chinese medicine for detoxicating.</p><p><b>RESULTS</b>Among the patients with H1N1 virus infection, 82.1% (55/67) patients presented with fever symptom, while more patients with high fever (≥ 39°C) were found in seasonal influenza patients (P < 0.05). For the H1N1 patients, the median interval between the symptom onset and the undetectable RNA was six days (4 - 10 days). But viral shedding was still found in 31.3% patients after 7 days following illness onset. The median interval between disappearance of fever and an undetectable viral RNA level was three days (2 - 8 days), and 17.9% patients were found to be viral shedding 6 days later after normalization of body temperature. For the seasonal influenza patients, 94.6% patients were detected out viral RNA within 7 days. The median interval of seasonal influenza between the symptom onset and the undetectable RNA was four days (3 - 8 days). The median interval between disappearance of fever and an undetectable viral RNA level was three days (2 - 6 days).</p><p><b>CONCLUSION</b>It suggests that 7 days isolation period from the illness onset or 24 hours after the resolution of fever and respiratory symptoms are not long enough to cut off the transmission among Chinese young adults with mild illness.</p>

Colloidal gold and dot-ELISA rapid tests for screening influenza A virus / 南方医科大学学报

<p><b>OBJECTIVE</b>To evaluate the diagnostic efficiency of colloidal gold and dot ELISA rapid tests in clinical screening of influenza A virus.</p><p><b>METHODS</b>The pharyngeal swabs were collected from 297 outpatients suspected of influenza between June and October, 2009 for detection with colloid gold and dot ELISA rapid test, with real-time PCR as the golden methods. The discrepant results of colloid gold and dot ELISA methods were confirmed by sequencing, and the diagnostic efficiency of the two methods was evaluated.</p><p><b>RESULTS</b>Among the 166 samples with influenza A virus infection as confirmed by real-time PCR and sequencing, the diagnostic sensitivity of dot ELISA and colloid gold methods was 54.82% (91/166) and 4.22% (7/166), respectively. The total concordance rate with PCR was 66.67% (Kappa value of 0.35). Among the 133 samples negative for influenza A virus, the specificity of dot ELISA and colloid gold methods was 81.68% (107/131) and 98.47% (129/131), respectively, with a total concordance rate with PCR of 45.79% (Kappa value 0.02). Of the 99 H1N1 influenza samples confirmed by real-time PCR, the detection rate of dot ELISA was 67.3%, whereas that of colloid gold was 5.1%. Out of the 107 dot ELISA-positive but colloid gold-negative samples, 84 were confirmed to be influenza A virus-positive by real-time PCR and sequencing. One sample negative for dot ELISA but positive for colloid gold test was confirmed to be influenza A virus-negative. The detection rate and diagnostic concordance rate for influenza A virus by dot ELISA were significantly higher than those of colloid gold (P<0.05).</p><p><b>CONCLUSION</b>Dot ELISA is better than colloid gold in influenza A virus detection and shows great prospect in clinical screening.</p>

Clinical manifestations and epidemic factors of autumn-winter type scrub typhus in children from northern new endemic area / 中华儿科杂志

<p><b>OBJECTIVE</b>Scrub typhus is an infectious disease due to Orientia tsutsugamushi transmitted by infected chigger mites. Scrub typhus has long been recognized to occur in southern areas of China, but has recently been increasingly often reported from the north since the first case was reported in Mengyin County, Shandong Province in 1986. The key objectives of the present study were to investigate the clinical manifestations and epidemic factors of scrub typhus in children from the northern new natural foci.</p><p><b>METHODS</b>The case records of 56 children with scrub typhus who were admitted to the 5 hospitals of Fei County from September 1993 to January 2004 were reviewed. Orientia tsutsugamushi (Ot) was isolated from the cases. Based on ecological observations on the composition, seasonal fluctuation of animal hosts and chigger mites, Ot was isolated from rodents and chiggers. IgG antibodies to Ot was detected by IFA. Genotypes of the Ot isolates were also identified by nested PCR.</p><p><b>RESULTS</b>Among 56 children scrub typhus cases, 46 were male, 10 were female; 96% exhibited typical eschars or ulcers, 100% cases had high fever, skin rashes were observed in 55 cases (98%), and regional lymphadenopathy occurred in 48 cases (86%). All cases came from countryside, and all had histories of exposure to the crop field. fifty-one serum samples of suspected patients with scrub typhus were collected, 48 were positive for antibodies to Ot. The serotypes were Gilliam types. The cases only appeared in September to December with the peak at mid and late October. Leptotrombidium (L.) scutellare was the most important vector causing scrub typhus in the foci. Apodemus (A.) agrarius was the main host animals of Ot in the crop field. Totally 26 strains were isolated from patients, rodents, and chigger mites. The serotypes of 24 out of the 26 isolates were Gilliam types, while the genotypes of these isolates were Kawasaki types. The serotypes of the other 2 isolates were identical and both were Karp types.</p><p><b>CONCLUSION</b>Children scrub typhus patients were frequently seen in the new natural foci of Shandong province. Exposure history, typical eschars or ulcers, and presence of IgG antibody were the important indexes to diagnose the disease.</p>

Amplification and restriction fragment length polymorphism analysis on the complete sequence of Sta56 gene of Orientia tsutsugamushi isolated from Shandong area / 中华流行病学杂志

<p><b>OBJECTIVE</b>To analyze the genetic differences of Orientia tsutsugamushi (Ot) Sta56 gene between Shandong isolates and other strains deposited in GenBank.</p><p><b>METHODS</b>PCR and restriction fragment length polymorphism (RFLP) were used to amplify the complete sequence of Ot-Sta56 gene. RFLP profiles of Ot were predicted by a computer program according to their complete sequences of Ot-Sta56 gene. PCR amplicon from XDM2 strain was sequenced and analyzed by Clustal X (1.8) and PHYLIP software.</p><p><b>RESULTS</b>The complete sequences (about 1.6 kbp) of Ot-Sta56 gene were amplified from B16 strain (isolated from patients), FXS2 strain (isolated from A. agrarius) and XDM2 strain. Four species of restriction endonucleases (Hha I, Hinf I, Hae III, Pst I) were used to digest the PCR amplicons from the 3 isolates. When comparing with the RFLP profiles of prototype Ot, the RFLP profiles of PCR amplicons from the 3 isolates were similar to those of Japan Kawasaki strain, but were quite different from the international reference strains Gilliam, Karp, Kato. Results from DNA sequence analysis showed that the complete sequence of Ot-Sta56 gene homology to Japan Kawasaki strain of XDM2 strain was 97%, and deduced amino acid sequence was 92%.</p><p><b>CONCLUSION</b>Data from the complete sequence of Sta56 gene indicated that the genotypes of Ot isolates in Shandong province were similar, but with distinction from the Kawasaki strain.</p>

Hypothesis on generating and tracer gas study regarding transmission of severe acute respiratory syndrome through ventilation system in a general hospital / 中华流行病学杂志

<p><b>OBJECTIVE</b>By measuring airflow and ventilation distribution of ward building, to explore and verify the hypothesis of airborne transmission and risk factor of severe acute respiratory syndrome (SARS) nosocomial infection.</p><p><b>METHODS</b>Tracer gas (perfume of plant oil) was emitted to the bathroom of wards when SARS index patient lived. Six different experimental situations were designed to control the status of exhaust fan in bathrooms, exhaust fan in the top of building and fresh air exchange system. The concentration of perfume was separately measured by 4 groups of lab workers and recorded blindly by the scores of "tenth degree".</p><p><b>RESULTS</b>Tracer gas was detected from the wards of 8th to 13th floor.</p><p><b>CONCLUSION</b>Architecture and ventilation system of the inpatient building in the hospital contributed to the aerodynamic condition of SARS nosocomial infection through airborne transmission. The distribution of tracer gas in the wards was associated with SARS patients in this building. It was possible that SARS could have been transmitted to for distance by aerosol or other carriers.</p>

Preliminary result on the nosocomial infection of severe acute respiratory syndrome in one hospital of Beijing / 中华流行病学杂志

<p><b>OBJECTIVE</b>To study the transmission route of severe acute respiratory syndrome (SARS) nosocomial infection.</p><p><b>METHODS</b>Ten identified SARS patients were selected from a general hospital in March. Survey was carried out through a standardized questionnaire provided by Chinese Center for Disease Control and Prevention. Contents of the questionnaire would include: history of contact with SARS patient, route of infection, methods used for protection and so on.</p><p><b>RESULTS</b>(1) Distribution os SARS patients were confined to 3 wards: 4, 5, and 6 on the 7, 8, 12, 13 and 14 floors in the west unit of the inpatient building. Most of the inpatients were elderly and having severe original diseases. (2) Index patients were the first generation source of transmission and they infected inpatients and medical staff, making them the second generation. People with latent infection who had close contact with SARS patients might also serve as the possible source of transmission. (3) The major transmission routes were: near distant droplet infection and close contact infection. There was also a clue to the probability of aerosol or droplet nuclei infection through air-conditioning and ventilation system.</p><p><b>CONCLUSION</b>Nosocomial infection appeared to be the main characteristic of the SARS epidemic in the early stage of this hospital. Other than close contact and near space airborne transmission of SARS virus, the possibility of long-distance aerosol transmission called for further epidemiological and experimental studies in the future.</p>

Analysis on genotypes and their epidemiology of MLS_B resistant Staphylococcus epidermidis isoloates causing nosocomial infections / 中华检验医学杂志

Objective To determine the genotypes and their epidermiology of microlide, lincosamide and streptogramin B(MLS_B)resistant S.epidermidis isolates causing nosocomial infection.Method 126 isolates were collected from inpatients in three hospitals in Beijing from 2003-2004 for testing the antibiotic susceptibility to the macrolide erythromycin,the lincosamide clindamycin.The resistance phenotypes of erythromycin-resistant isolates were determined by the double-disc test with erythromycin and clindamycin.The presence of the relative genes(ermA,ermB,ermC and msrA)to MLS_B resistance was identified by PCR and the similarity of the isolates was analyzed by PFGE.Result The isolates were mostly resistant to macrolide and lincosamide.In the constitutive phenotype cMLS_B isolates,the methicillin resistant S.epidermidis(MRSE)proportion appeared high(78.5%),whereas high methicillin susceptible S.epidermidis(MSSE)proportion was found in the inducible MLS_B phenotype(iMLS_B) (69.2%).ermC was shown as the most frequent determinant to the resistance,not only in MRSE and MSSE (70.8% and 6.8%),but also in iMLS_B and cMLS_B(76.9% and 90.3%).No specific endemic strain was found by PFGE analysis.The same resistance phenotype pattern was not clustered together and distributed into type A～F at the similarity of 60%.Among the phenotypes(cMLS_B,iMLS_B and MS phenotype),no significant difference was shown in the PFGE genotype distribution.Conclusion Our results indicate that the MLS_B resistance in S.epidermidis causing nosocomial infection is prevalent in the hospital and MLS_B antibiotics should be used iudiciously,ermC was shown as the most frequent determinant to the resistance.

Biofilm Production in Staphylococcus epidermidis Isolated from Hosocomial Infection / 微生物学通报

To determine the relationship between the intercellular adhesion operon (ica) and the biofilm production in Staphylococcus epidennidis isolates from nosocomial infection, and the affection of ica on the antibiotic susceptibility of the isolates, we collected 106 strains, epidermidis isolates from nosocomial infection specimen to detect their biofilm production by quantitative and qualitative method and investigate the existence of ica operon by PCR. The minimal inhibitory concentration (MIC) to erythromycin, ampicillin, cefoxitin, ceftriaxone, teco-planin, ciprofloxacin, tetracycline, trimethoprim-sulfamethoxazole and vancomycin were tested. Among the isolates, 33 (31. 1% ) of them were detected out carrying ica operon. The rate of biofilm production of the ica-posi-tive isolates was higher than that of the ica-negative (P =0. 001) . By adding glucose and NaCl into the culture the detection rate of biofilm production could be increased. The antibiotic susceptibility of the plankton cells of ica-positive isolates to erythromycin, cefoxitin and ceftriaxone , except ampicillin, ciprofloxacin, tetracycline and tremethoprim-sulfamethoxazole, were lower than those of ica-negative isolates. This study showed that the existence of ica operon was close related to the biofilm formation in 5. epidermidis isolates from nosocomial infection. However, the mechanism of antibiotic resistance of the strains inside the biofilm still needed to be illustrated.

Bacterial Disinfectant Resistance / 微生物学通报

Bacterial disinfectant resistance is the phenomenon that minimal inhibitory concentration or minimal bactericidal concentration of a certain disinfectant increases after a certain bacterium contacts with it many times. It exists widespread. Many species of bacteria are may resistant to a certain disinfectant, and a species of bacterium is may resistant to many disinfectant Disinfectant selectivity pressure is the extrinsic agent of bacterial disinfectant resistance. Resistance mechanisms include bacterial biochemistry structure, genetics pathway and enzymology pathway. There is relationship in disinfectant resistance and drug resistance. We should strengthen study and monitoring, enact unified standard and application specification to reduce bacterial disinfectant resistance.