Pathogenic characterization of Klebsiella pneumoniae resistant to carbapenems and polymyxin / 中华预防医学杂志

Objective: Analysis and investigation of pathogenic characteristics of polymyxin-and carbapenem-resistant Klebsiella pneumoniae (PR-CRKP). Methods: A total of 23 PR-CRKP strains isolated from clinical specimens from the General Hospital of Southern Theater Command from March 2019 to July 2021 were retrospectively collected, Whole-genome sequencing was performed on 23 PR-CRKP strains, resistance genes were identified by comparison of the CARD and the ResFinder database, high-resolution typing of PR-CRKP strains was analyzed by core genomic multilocus sequencing (cgMLST) and single nucleotide polymorphism (SNP); polymyxin resistance genes were determined by PCR and sequencing. Results: All PR-CRKP strains were KPC-2 producing ST11 types. cgMLST results showed that the evolutionary distance between the PR-CRKP strains and Klebsiella pneumoniae in mainland China was 66.44 on average, which is more closely related than foreign strains; the 23 PR-CRKP strains were divided into 3 main subclusters based on SNP phylogenetic trees, with some aggregation among Clade 2-1 in the isolation department and date. The two-component negative regulatory gene mgrB has seven mutation types including point mutations, different insertion fragments and different insertion positions. Conclusion: The close affinity of PR-CRKP strains indicate the possibility of nosocomial clonal transmission and the need to strengthen surveillance of PR-CRKP strains to prevent epidemic transmission of PR-CRKP.

Efficacy of real-time PCR for detecting Clostridium difficile infection: comparison with enzyme-linked fluorescent spectroscopy-based approaches / 南方医科大学学报

<p><b>OBJECTIVE</b>To evaluate the diagnostic efficacy of real?time polymerase chain reaction (q?PCR) for Clostridium difficile infection (CDI) in comparison with routine culture and enzyme?linked fluorescent spectroscopy?based aprroaches.</p><p><b>METHODS</b>Stool samples were collected from suspected CDI cases in General Hospital of Guangzhou Military Command of PLA between May and December in 2016. All the samples were examined with 3 methods, namely enzyme?linked fluorescent spectroscopy for detecting Clostridium difficile toxin A/B (CDAB), detection of glutamate dehydrogenase (GDH), and q?PCR for amplification of Clostridium difficile?specific gene tpi and toxin gene (tcdA/tcdB), with the results of fecal culture as the reference for evaluating the diagnostic efficacy of the 3 methods.</p><p><b>RESULTS</b>Of the total of 70 fecal samples, 13 (18.57%) were found to be positive for Clostridium difficile, including toxin?producing strains in 6 (8.57%) samples. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic coincidence rate of q?PCR for tpi were 92.31%, 91.23%, 70.59%, 98.11% and 91.43%, respectively, which were significantly higher than those of GDH test (84.62%, 84.21%, 55.00%, 96.00%, and 84.29%, respectively; Χ=24.881, P<0.001). The sensitivity of q?PCR for tcdA/cdB was significantly higher than that of enzyme?linked fluorescent spectroscopy for CDAB in detecting CDI (66.67% vs 33.33%; Χ=35.918, P<0.001).</p><p><b>CONCLUSION</b>Both CDAB detection and q?PCR have a high specificity in detecting CDI, but GDH detection has a good sensitivity, and all these 3 methods have a high negative predictive value. Compared with other detection methods, amplification of tpi and tcdA/tcdB using q?PCR allows more rapid, sensitive and specific detection of CDI.</p>

Epidemiological survey of high-risk human papillomavirus among 2501 woman / 南方医科大学学报

<p><b>OBJECTIVE</b>To survey the prevalence of high-risk human papillomavirus (HPV) in woman in Guangzhou during the period from 2013 to 2014.</p><p><b>METHODS</b>A total of 2501 women in Guangzhou seeking medical attention in our hospital underwent high-risk HPV genotype screening of cervical specimens using real-time PCR.</p><p><b>RESULTS</b>The prevalence of high-risk HPV infection among the women was 14.85% (146/983) in the year 2013, similar to the rate of 14.56% (221/1518) in 2014 (Χ(2)=0.041, P=0.839); no significant differences were found in the high-risk HPV infection rates between different age groups in either 2013 (Χ(2)=2.916, P=0.572) or 2014 (Χ(2)=6.494, P=0.165). The constituent ratio of the 13 types of high-risk HPV showed no significant difference between 2013 and 2014 (Χ(2)=11.872, P=0.452). The 13 HPV genotypes detected, listed in a descending order of the constituent ratios, included HPV-52, -16, -58, -56, -39, -51, -68, -59, -31, -35, -18, -33 and -45 in 2013, and were HPV-52, -16, -58, -68, -18, -51, -56, -39, -31, -33, -59, -35 and-45 in 2014.</p><p><b>CONCLUSION</b>We report a high prevalence of high-risk HPV among women in Guangzhou, which suggests the necessity of screening for high-risk HPV-DNA among women at all ages for prevention and early detection of cervical cancer.</p>

Clinical evaluation of the application of gene chip for identifying pathogens in blood cultures / 南方医科大学学报

<p><b>OBJECTIVE</b>To explore the feasibility of using gene chip method to identify pathogens in blood cultures.</p><p><b>METHODS</b>Clinical blood samples were obtained and cultured using an automated blood culture system. A gene chip diagnostic kit was used to detect the pathogenic bacteria in these blood cultures following the procedures of target gene extraction and amplification, hybridization and result analysis. The conventional method was also used to isolate and identify the bacteria from the clinical blood cultures, and the results of the two methods were compared.</p><p><b>RESULTS</b>In the 86 clinical blood samples, 74 were positive and 12 negative according to the conventional method, while 48 were positive and 38 negative as found by the gene chip method, showing significant differences in the results (P<0.05). The two methods only had a concordance rate of 69.77%.</p><p><b>CONCLUSION</b>The gene chip diagnostic kit has low concordance rate with the conventional method for detecting pathogens in clinical blood cultures and awaits further improvement.</p>

Variability analysis of S2 gene of SARS-CoV / 南方医科大学学报

<p><b>OBJECTIVE</b>To determine the sequence of S2 gene of SARS-associated coronavirus (SARS-CoV) GD322 and analyze the phyletic evolution of S2 gene.</p><p><b>METHOD</b>S2 gene fragment was amplified from SARS-CoV GD322 genome with RT-PCR and ligated to pGEM-T vector for sequence analysis after transformation of the plasmid into E. coli DH5a. The variability of S2 genes and S2 proteins from 12 strains isolated in the early, intermediate and advanced stages of the SARS outbreak were analyzed and the phylogenetic tree was constructed with Lasergene, Clustal X, DNAman and Treeview. T cell antigen epitopes of S2 protein were predicted on the basis of Internet database.</p><p><b>RESULT</b>With the epidemic spread of SARS-CoV, the S2 genes of the virus tended to become stable. Homology of S2 genes of SARS-CoV isolated in advanced stage of the outbreak reached 99.9%. Prediction of T cell antigen epitope showed that mutation at the 57th amino acid effected T cell antigen epitope.</p><p><b>CONCLUSION</b>S2 gene of GD322 SARS-CoV is relatively stable during the epidemic spread of the virus, and mutation at the 57th amino acids of S2 protein may affect the T cell antigen epitope.</p>

Construction and identification of genomic cDNA subclones of dengue 2 virus NGC strain / 南方医科大学学报

<p><b>OBJECTIVE</b>To construct the cDNA subclones spanning the entire genome of dengue 2 virus NGC strain for further construction of full-length infectious viral cDNA clone.</p><p><b>METHODS</b>Two pairs of primers were designed according to the restriction endonuclease sites in the viral genome of dengue 2 virus NGC strain. After viral RNA extraction from the brain of infected new-born mice, two parts of full-length viral cDNA were amplified by long RT-PCR and cloned into the vector pCR-XL-TOPO. The partial sequence of the recombinant plasmid was determined.</p><p><b>RESULTS AND CONCLUSION</b>Sequence analysis and digestion with restriction enzymes demonstrated that the two cDNA subclones were specific for dengue 2 virus NGC strain, suggesting the successful construction of the two cDNA subclones of dengue 2 virus NGC strain.</p>