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【Objective】 To compare the macrolide resistance, molecular characteristics and multilocus antigen sequence typing (MAST) of Bordetella pertussis (Bp) collected from Xi’an and Shanghai so as to provide reference for prevention of pertussis and optimize vaccination strategies. 【Methods】 Erythromycin, azithromycin and clarithromycin susceptibility of clinical isolates collected from Xi’an and Shanghai during 2018 and 2019 were determined by E-test. PCR was used to detect the drug-resistant genes and mutation sites. MAST was employed to do molecular typing for the strains. The differences in macrolide resistance and MAST types between Xi’an and Shanghai were compared. 【Results】 Totally 34 strains from Xi’an and 26 strains from Shanghai were isolated. There were differences between Xi’an and Shanghai in the macrolide resistance (χ2=13.650, P<0.001). The composition ratio of MAST types of pertussis strains was also different between Xi’an and Shanghai (χ2=18.642, P<0.001) in that the prn1/ptxP1/ptxA1/fim3-1/fim2-1 strains dominated in Xi’an, while the prn1/ptxP1/ptxA1/fim3-1/fim2-1 and prn2/ptxP3/ptxA1/fim3-1/fim2-1 were almost half and half in Shanghai. A2047G site mutation was detected in all the macrolide-resistant strains, but not in all sensitive strains. Methylase genes ermA and ermB were detected in some macrolide-resistant strains. No other macrolide-resistant genes were found in resistant strains and no mutation or drug resistance gene was found in all the susceptible strains. 【Conclusion】 Differences existed between Xi’an and Shanghai in the macrolide resistance and MAST types of Bordetella pertussis strains. Further monitoring of Bordetella pertussis in China is required to better understand the resistance and evolution of the pathogen.
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Objective:To investigate the genetic diversity and molecular epidemiology of Bordetella pertussis in Shaanxi province, and analyze the possible reasons of resurgence in this region. Methods:We characterized clinical isolates collected during 2012-2017 using multilocus antigen sequence typing (MAST) and multilocus variable-number tandem repeat analysis (MLVA).Results:The circulating strains and vaccine strains were different in molecular characteristics. The majority (95%) of the isolates were typed as prn1/ ptxP1/ ptxA1/ fim3-1/ fim2-1. In addition, eight MLVA types (MTs) and eight PFGE profiles were identified, respectively. MT195, MT55 and MT104 were dominant and MT195 continually increased annually. Conclusions:The genetic characteristics of the current strains in Shaanxi province were different from those of the vaccine strain. The evolution through genetic variation might be one of the reasons for the recurrence of pertussis in this region.
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Objective:To analysis the macrolide resistance, molecular characteristics and plused-field gel electrophoresis(PFGE) type of Bordetella pertussis ( Bp), explore the possible resistance mechanism and the relationship between PFGE types and macrolide resistance profiles. Methods:Erythromycin, azithromycin and clarithromycin susceptibility of clinical isolates during 2016 to 2018 was determined by E-test. PCR was used to detect the drug-resistant genes and mutation sites. PFGE were employed to do molecular typing for the strains.Results:Thirty-five strains were isolated, of which 27 strains were resistant to all three antibiotics, two strains were resistant to erythromycin and azithromycin, and six strains were sensitive to all three antibiotics. Partial macrolide resistant strains carried the methylase gene ermA (27.6%, 8/29) and ermB (31.0%, 9/29); A2047G site mutation was detected in macrolide-resistant strains, while no drug-resistant genes or mutation sites were found in sensitive strains. Resistant strains were classified into BPSR23 and BPFINR9 types, while sensitive strains were other profiles. Conclusions:The clinical isolated Bp were seriously resistant to erythromy and showed signs of resistance to other macrolides. The acquisition of methylase gene and mutation of A2047G site might be the main mechanism of resistance. The macrolide resistance might have has a certain correlation with PFGE profile.
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This paper reviews the computer vision and image analysis studies aiming at automated diagnosis or screening of malaria in microscope images of thin blood film smears. On the basis of introducing the background and significance of automatic detection technology,the existing detection technologies are summarized and divided into several steps,including image acqui-sition,pre-processing,morphological analysis,segmentation,count,and pattern classification components. Then,the princi-ples and implementation methods of each step are given in detail. In addition,the promotion and application in automatic detec-tion technology of thick blood film smears are put forwarded as questions worthy of study,and a perspective of the future work for realization of automated microscopy diagnosis of malaria is provided.