Genyan Liu

Prevalence and Characterization of Class I Integrons among Pseudomonas aeruginosa and Acinetobacter baumannii Isolates from Patients in Nanjing, China

ABSTRACT Class I integrons were detected in 40.8% (40/98) of Pseudomonas aeruginosa strains and 52.8% (56/106) of Acinetobacter baumannii strains in the Nanjing area of China, including several cassette arrays not previously reported.

Comparison of the prevalence and changing resistance to nalidixic acid and ciprofloxacin of Shigella between Europe–America and Asia–Africa from 1998 to 2009

Shigella is becoming an increasing public health problem due to development of multiple antimicrobial resistance, frequently resulting in treatment failure. A systematic review was conducted based on a literature search of computerised databases. Random or fixed-effects models were used, based on the P-value considering the possibility of heterogeneity between studies, for meta-analysis. Statistical analyses were performed using STATA 10.0. In the area of Asia-Africa, resistance rates to nalidixic acid and ciprofloxacin were 33.6% [95% confidence interval (CI) 21.8-46.6%] and 5.0% (95% CI 2.8-7.8%), respectively, 10.5 and 16.7 times those of Europe-America. Moreover, resistance to nalidixic acid and ciprofloxacin in Asia-Africa progressively increased each year, reaching 64.5% (95% CI 13.8-99.3%) and 29.1% (95% CI 0.9-74.8%), respectively, in 2007-2009, whilst isolates in Europe-America remained at low levels of resistance (<5.0% and <1.0%, respectively). All Shigella flexneri strains showed higher resistance than Shigella sonnei in Europe-America: overall, 3.5% (95% CI 1.4-6.4%) vs. 2.6% (95% CI 1.0-5.0%) resistant to nalidixic acid and 1.0% (95% CI 0.3-2.2%) vs. 0.1% (95% CI 0.0-0.3%) resistant to ciprofloxacin. In Asia-Africa, a similar trend was found for ciprofloxacin [3.0% (95% CI 1.4-5.3%) vs. 0.5% (95% CI 0.2-0.8%)], whereas the trend was reversed for nalidixic acid [32.6% (95% CI 14.5-53.9%) vs. 44.3% (95% CI 26.9-62.5%). In conclusion, quinolone resistance in Shigella has increased at an alarming speed, reinforcing the importance of continuous monitoring of antimicrobial resistance in Shigella.

MALDI-TOF MS versus VITEK 2 ANC card for identification of anaerobic bacteria

BACKGROUND Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is an accurate, rapid and inexpensive technique that has initiated a revolution in the clinical microbiology laboratory for identification of pathogens. The Vitek 2 anaerobe and Corynebacterium (ANC) identification card is a newly developed method for identification of corynebacteria and anaerobic species. The aim of this study was to evaluate the effectiveness of the ANC card and MALDI-TOF MS techniques for identification of clinical anaerobic isolates. METHODS Five reference strains and a total of 50 anaerobic bacteria clinical isolates comprising ten different genera and 14 species were identified and analyzed by the ANC card together with Vitek 2 identification system and Vitek MS together with version 2.0 database respectively. 16S rRNA gene sequencing was used as reference method for accuracy in the identification. RESULTS Vitek 2 ANC card and Vitek MS provided comparable results at species level for the five reference strains. Of 50 clinical strains, the Vitek MS provided identification for 46 strains (92%) to the species level, 47 (94%) to genus level, one (2%) low discrimination, two (4%) no identification and one (2%) misidentification. The Vitek 2 ANC card provided identification for 43 strains (86%) correct to the species level, 47 (94%) correct to the genus level, three (6%) low discrimination, three (6%) no identification and one (2%) misidentification. CONCLUSIONS Both Vitek MS and Vitek 2 ANC card can be used for accurate routine clinical anaerobe identification. Comparing to the Vitek 2 ANC card, Vitek MS is easier, faster and more economic for each test. The databases currently available for both systems should be updated and further developed to enhance performance.

Necrotizing pneumonia and empyema caused by Neisseria flavescens infection.

Neisseria flavescens is an uncommon pathogen of human infection, pneumonia and empyema caused by N. flavescens is rarely reported. Herein, we report a 56-year-old diabetic patient presenting necrotising pneumonia and empyema due to N. flavescens infection. The main clinical manifestation of this patient was high fever, sticky pus and gradually aggravating dyspnea. The chest computed tomography (CT) scan showed there are mass of high density areas around hilus of the left lung, hollow sign with inflammation also appeared. A biopsy specimen was taken from the left principal bronchus by lung puncture biopsy and showed necrosis and inflammation. Microscopic examination of direct smear and culture of sticky pus, much more gram-negative diplococcus was present, pathogen was further identified by Vitek NH card, Vitek MS and confirmed as N. flavescens by 16S rRNA gene sequencing finally. Anti-infection therapy following the antimicrobial susceptibility test results was effectively. To our knowledge, this is the first report of pulmonary infection caused by N. flavescens.

Comparison of resistance to third-generation cephalosporins in Shigella between Europe-America and Asia-Africa from 1998 to 2012

We conducted a systematic review to compare resistance to third-generation cephalosporins (TGCs) in Shigella strains between Europe-America and Asia-Africa from 1998 to 2012 based on a literature search of computerized databases. In Asia-Africa, the prevalence of resistance of total and different subtypes to ceftriaxone, cefotaxime and ceftazidime increased markedly, with a total prevalence of resistance up to 14·2% [95% confidence interval (CI) 3·9-29·4], 22·6% (95% CI 4·8-48·6) and 6·2% (95% CI 3·8-9·1) during 2010-2012, respectively. By contrast, resistance rates to these TGCs in Europe-America remained relatively low--less than 1·0% during the 15 years. A noticeable finding was that certain countries both in Europe-America and Asia-Africa, had a rapid rising trend in the prevalence of resistance of S. sonnei, which even outnumbered S. flexneri in some periods. Moreover, comparison between countries showed that currently the most serious problem concerning resistance to these TGCs appeared in Vietnam, especially for ceftriaxone, China, especially for cefotaxime and Iran, especially for ceftazidime. These data suggest that monitoring of the drug resistance of Shigella strains should be strengthened and that rational use of antibiotics is required.

Prevalence and trends of aminoglycoside resistance in Shigella worldwide, 1999-2010.

Shigellosis causes diarrheal disease in humans in both developed and developing countries, and multi-drug resistance in Shigella is an emerging problem. Understanding changing resistance patterns is important in determining appropriate antibiotic treatments. This meta-analysis systematically evaluated aminoglycoside resistance in Shigella. A systematic review was constructed based on MEDLINE and EMBASE databases. Random-effect models or fixed-effect models were used based on P value considering the possibility of heterogeneity between studies for meta-analysis. Data manipulation and statistical analyses were performed using software STATA 11.0. By means of meta-analysis, we found a lower resistance to three kinds of aminoglycosides in the Europe-America areas during the 12 year study period than that of the Asia-Africa areas. Kanamycin resistance was observed to be the most common drug resistance among Shigella isolates with a prevalence of 6.88% (95%CI: 6.36%-7.43%). Comparison of data from Europe-America and Asia-Africa areas revealed that Shigella flexneri resistance was greater than the resistance calculated for Shigella sonnei. Importantly, Shigella sonnei has played a significant role in aminoglycoside-resistance in recent years. Similarly, data showed that resistance to these drugs in children was higher than the corresponding data of adults. In conclusion, aminoglycoside-resistant Shigella is not an unusual phenomenon worldwide. Distribution in Shigella resistance differs sharply based on geographic areas, periods of time and subtypes. The results from the present study highlight the need for continuous surveillance of resistance and control of antibiotic usage.

Comparison of four DNA extraction methods for detecting Mycobacterium tuberculosis by real-time PCR and its clinical application in pulmonary tuberculosis

OBJECTIVES China is one of the countries with a high burden of Mycobacterium tuberculosis (MTB) infection. One challenge for the earlier diagnosis of tuberculosis is the DNA extraction of MTB. This study was to compare four MTB DNA extraction methods, and use the best one in the diagnosis of pulmonary tuberculosis. METHODS A total of 43 serum and 94 plasma samples were collected from 124 clinical diagnosed pulmonary tuberculosis patients. Four different MTB DNA extraction methods, including phenol-chloroform method, Qiagen kit, Omega kit and magnetic bead method, were compared to determine which method displayed the highest sensitivity. A quantitative fluorescent PCR assay was also designed for the detection of MTB DNA. RESULTS The highest DNA extraction efficiency (52.8%) and the best reproducibility (coefficient of variance =26.7%) were observed using the magnetic bead method. For 39 of the 124 (31.5%) pulmonary tuberculosis patients, MTB DNA was detected in their plasma or serum samples. Interestingly, 35.3% (12/34) of smear-negative cases were MTB DNA positive. CONCLUSIONS In conclusion, magnetic bead method is the best one for the DNA extraction of MTB. The detection of MTB DNA may provide valuable information for the diagnosis of acid-fast bacilli (AFB) negative pulmonary tuberculosis patients.

Changing trend of antimicrobial resistance among pathogens isolated from lower respiratory tract at a university-affiliated hospital of China, 2006-2010

OBJECTIVE To investigate the distribution and the antimicrobial resistance of pathogens in lower respiratory tract infection from 2006 to 2010. METHODS The sputum specimens from inpatients with lower respiratory tract infection in the First Affiliated Hospital of Nanjing Medical University during the past five years were cultured and identified; the antimicrobial resistance was analyzed by the software WHONET 5.4. RESULTS A total of 12,191 isolates were characterized in sputum samples: 73.5% were Gram-negative bacteria, 13.7% were Gram-positive bacteria, and 12.8% were fungi. The isolation rate of Acinetobacter was significantly increasing from 12.8% in 2006 to 26.4% in 2010. The Gram-negative bacterial resistance rate to the second and third generation cephalosporin increased year by year. Decreasing trend, 78.7% in 2006 decreased to 63.5% in 2010 (R(2)=0.93 and P<0.01), in resistance to clindamycin against Staphylococcus aureus was observed. Worth noting is the drug resistance of Acinetobacter and Klebsiella pneumoniae to carbapenem significantly increased (R(2)>0.3 and P≤0.05). CONCLUSIONS The antimicrobial resistance of pathogens in lower respiratory tract infection increased in recent years. The hospitals and government departments should strengthen management of the use of some antibiotics, such as the second/third generation cephalosporin and carbapenem, in order to enhance the effectiveness of medication.

Emergence of linezolid resistance in a clinical Staphylococcus capitis isolate from Jiangsu Province of China in 2012

Linezolid (LZD) is an important antimicrobial agent for the treatment of infections caused by Gram-positive organisms, including methicillin-resistant Staphylococci. And until now, LZD resistance in clinical is still rare. Here we reported the first case of LZD resistance Staphylococcus capitis in Jiangsu, China. This strain was isolated from a 92-year old female who received long-term and repeatedly antibiotics treatment because of recurrent pulmonary infections in August 2012. Isolated from blood, the Staphylococcus capitis showed a resistance to LZD with a minimal inhibitory concentration (MIC) of 64 µg/mL, and the followed gene detection showed that the isolates existed C2190T and C2561Y point mutations in the 23S rRNA. Moreover, the isolation was also found carrying the cfr gene.

Prevalence and characterization of class 1 integrons in multi-drug resistant Salmonella sp. from China in 2010.

Prevalence and characterization of class 1 integrons in multi-drug resistant Salmonella sp. from China in 2010 Dandan Shen, Yanling Xu, Shiyang Pan, Yun Li, Yuan Lu, Ting Xu, Wenying Xia, Genyan Liu, Bing Gu Department of Laboratory Medicine, The First Affiliated Hospital of Nanjing Medical University, China, National Key Clinical Department of Laboratory Medicine, Nanjing, China, Department of Respiratory Medicine, The First Affiliated Hospital of Nanjing Medical University, China, Institute of Clinical Pharmacology, The First Hospital, Peking University, Beijing, China