Typing of drug resistant isolates of Mycobacterium tuberculosis from India using the IS6110 element reveals substantive polymorphism.

We investigated IS6110 polymorphism in clinical isolates of Mycobacterium tuberculosis from patients attending the outpatient department at various hospitals in northern India. DNA fingerprinting of 126 clinical isolates of M. tuberculosis was carried out using restriction fragment length polymorphism (RFLP) associated with the IS6110 element in M. tuberculosis genomes. A substantive degree of polymorphism was evident in the MDR M. tuberculosis isolates. The number of bands in the fingerprints varied from 0 to 19. However, the lack of common bands made it difficult to cluster the majority of these isolates. We were also unable to associate drug resistance with IS6110 copy number. Specific regions of the gyrA and katG genes from a representative number of these isolates were sequenced to determine the genotype. The majority of the isolates analyzed were found to belong to Group 1, indicating that these strains were evolutionarily older. We find no evidence of the W strain, prevalent in the US, in our study. The epidemiological patterns of the various strains in India seem to be very complex, as reflected by the presence of a large number of different strains (types) within north India.     

Minimal Diversity of Drug-Resistant Mycobacterium tuberculosis Strains,South Africa

Multidrug- (MDR) and extensively drug-resistant tuberculosis (XDR TB) are commonly associated with Beijing strains. However, in KwaZulu-Natal, South Africa, which has among the highest incidence and mortality for MDR and XDR TB, data suggest that non-Beijing strains are driving the epidemic. We conducted a retrospective study to characterize the strain prevalence among drug-susceptible, MDR, and XDR TB cases and determine associations between strain type and survival. Among 297 isolates from 2005–2006, 49 spoligotype patterns were found. Predominant strains were Beijing (ST1) among drug-susceptible isolates (27%), S/Quebec (ST34) in MDR TB (34%) and LAM4/KZN (ST60) in XDR TB (89%). More than 90% of patients were HIV co-infected. MDR TB and XDR TB were independently associated with mortality, but TB strain type was not. We conclude that, although Beijing strain was common among drug-susceptible TB, other strains predominated among MDR TB and XDR TB cases. Drug-resistance was a stronger predictor of survival than strain type. Key words: Mycobacterium tuberculosis, drug resistance, transmission, genotype, South Africa, HIV, bacteria, tuberculosis, tuberculosis and other mycobacteria, antimicrobial resistanceDrug-resistant tuberculosis (TB) has emerged as a substantial threat to advances in global TB control over the past several decades (1). Worldwide, an estimated 630,000 cases of multidrug-resistant (MDR) TB occurred in 2011, and extensively drug-resistant (XDR) TB has now been reported in 84 countries (2). MDR TB and XDR TB are each associated with very high mortality rates (3), and their transmission—both in community and health care settings—remains an ongoing challenge in resource-limited settings and in countries with high rates of HIV co-infection.In South Africa, the incidence of MDR TB has increased 5-fold since 2002 (2,4). MDR TB treatment is now estimated to consume more than half of the budget allocated for TB control in South Africa (5). The emergence of XDR TB, and its associated high mortality rates, have further underscored the need for clarifying the factors driving the drug-resistant TB epidemic to better focus control efforts (3,6,7).Drug-resistant TB is generally considered a human-made phenomenon that occurs when inadequate TB treatment creates selection pressure for the emergence of drug-resistant Mycobacterium tuberculosis subpopulations (acquired resistance) (1). Researchers initially believed that the mutations causing drug resistance would exert a “fitness cost,” rendering those strains too weak to be transmitted (8,9). Nonetheless, transmission of drug-resistant TB strains has now been well-documented (10–13), and laboratory studies have shown that clinical strains may have minimal fitness costs or even none (14). Emerging data suggest that most MDR TB and XDR TB cases in South Africa and worldwide are likely caused by primary transmission of drug-resistant strains (2,15–19).Although the M. tuberculosis W/Beijing strain family has been described among cases of drug-susceptible, MDR TB, and XDR TB in South Africa, numerous other strain types have also been identified (20,21). Little is known about the transmissibility and virulence of M. tuberculosis strains aside from the W/Beijing strain family (22,23). In the Eastern Cape and Western Cape Provinces of South Africa, strains from the W/Beijing family have most often been associated with transmission of drug-resistant TB (24–27). At our study site in KwaZulu-Natal Province, however, the LAM4/KZN strain type has predominated among MDR TB and XDR TB cases and has been linked to nosocomial transmission and high mortality rates (3,16,17,28,29). This strain is a member of the Euro-American strain family and was first described in this region in 1994, evolving into an increasingly resistant phenotype over time (29).The reasons for why the LAM4/KZN strain is prominent in KwaZulu-Natal Province, rather than the Beijing strain, which is seen globally and in other parts of South Africa, is unclear. Moreover, it is unknown whether the higher mortality among patients with MDR TB and XDR TB in KwaZulu-Natal can be explained, in part, by a difference in genotypic prevalence and associated differences in strain virulence (3,6,7,28). In this study, we sought to characterize the genotypic diversity of M. tuberculosis strains among isolates causing drug-susceptible TB, MDR TB, and XDR TB in KwaZulu-Natal Province, South Africa. We also examined the relationship between M. tuberculosis strain, drug resistance, and patient survival.     

Molecular differentiation of Mycobacterium tuberculosis strains without IS6110 insertions

By using standard restriction fragment length polymorphism, 6 zero-copy IS6110 Mycobacterium tuberculosis isolates were identified from 1180 Maryland isolates as part of the National Tuberculosis Genotyping and Surveillance Network Project. By using various genotyping methods, we demonstrated that this zero band cluster can be differentiated into six genotypes.     

Instability of IS6110 patterns in multidrug-resistant strains of Mycobacterium tuberculosis

The stability of IS6110 restriction fragment length polymorphism (RFLP) pattern was determined in 31 isolates from patients with multidrug-resistant tuberculosis (MDR-TB). These patients were in actual chains of transmission and they referred to the National Institute of Tuberculosis and Lung Diseases, Tehran, Iran. Susceptibility testing against first- and second-line drugs were performed by the proportional method on Lowenstein-Jensen culture media. Thereafter, DNA fingerprinting by IS6110 with direct repeat (DR) region as a probe was performed by standard protocols. The rate of IS6110 changes was 16%, although, no variation was found in the DR region, in a time-span of 1-63 months. The strains with unstable IS6110 patterns were resistant to all drugs tested, and the majority of them (60%) were collected from HIV-positive patients. The results demonstrated that for a reliable interpretation of strain typing, it is better to use an additional marker along with IS6110 RFLP.     

Molecular typing of Mycobacterium tuberculosis strains with a common two-band IS6110 pattern

We conducted a program of population-based molecular typing of all Mycobacterium tuberculosis isolates obtained in Alabama since 1994. Of 2452 isolates, 1013 (41%) had fewer than 6 bands of IS6110; 348 (14%) had a single two-band pattern (JH2). With conventional epidemiologic methods, we identified three groups of related patients with JH2 isolates. Spoligotyping and pattern of variable number of tandem repeats identified 10 molecular groups; two found by conventional methods were subdivided.     

Extensively Drug-Resistant Mycobacterium tuberculosis from Aspirates,Rural South Africa

The yield from aspirating lymph nodes and pleural fluid for diagnosing extensively drug-resistant (XDR) tuberculosis is unknown. Mycobacterium tuberculosis was cultured from lymph node or pleural fluid aspirates of 21 patients; 7 (33%) cultures grew XDR M. tuberculosis. Additive diagnostic yield for XDR M. tuberculosis was found in parallel culture of sputum and fluid aspirate.Tuberculosis (TB) is the leading cause of death among HIV-infected persons in sub-Saharan Africa (1). Drug-resistant TB is an emerging public health threat in HIV-prevalent settings, but diagnosis is challenging because of the severely limited laboratory capacity for culture and drug-susceptibility testing (DST). TB diagnosis for HIV-infected patients is particularly challenging because these patients may be more likely to have smear-negative pulmonary disease or extrapulmonary TB (2,3). Extrapulmonary TB often is diagnosed by clinical findings, indirect measures (e.g., chemistry and cell count of cerebrospinal or pleural fluid, ultrasound of lymph nodes, or pericardial effusions), or smear microscopy for acid-fast bacilli from aspirated extrapulmonary fluid. However, drug-resistant TB is impossible to diagnose by these methods, instead requiring mycobacterial culture and DST (4,5).The prevalence of multidrug-resistant and extensively drug-resistant TB (XDR TB) in South Africa has risen exponentially during the past decade. At our rural study site, ≈10% of all TB cases now are drug resistant, and >90% of TB patients are HIV infected (6). Death from XDR TB exceeds 80%; most infected persons die before sputum culture and DST results are known (6). To improve case detection and decrease diagnostic delay of drug-resistant TB among patients with suspected extrapulmonary TB, we initiated a program to aspirate lymph nodes and pleural fluid for culture and DST. We quantified the yield of these lymph node and pleural fluid aspirates for diagnosing XDR TB.     

Interpreting genotype cluster sizes of Mycobacterium tuberculosis isolates typed with IS6110 and spoligotyping

Molecular techniques such as IS6110-RFLP typing and spacer oligonucleotide typing (spoligotyping) have aided in understanding the transmission patterns of Mycobacterium tuberculosis. The degree of clustering of isolates on the basis of genotypes is informative of the extent of transmission in a given geographic area. We analyzed 130 published data sets of M. tuberculosis isolates, each representing a sample of bacterial isolates from a specific geographic region, typed with either or both of the IS6110-RFLP and spoligotyping methods. We explored common features and differences among these samples. Using population models, we found that the presence of large clusters (typically associated with recent transmission) as well as a large number of singletons (genotypes found exactly once in the data set) is consistent with an expanding infectious population. We also estimated the mutation rate of spoligotype patterns relative to IS6110 patterns and found the former rate to be about 10-26% of the latter. This study illustrates the utility of examining the full distribution of genotype cluster sizes from a given region, in the light of population genetic models.     

鲍氏不动杆菌脉冲场凝胶电泳和扩增片段长度多态性基因分型的研究

目的利用脉冲场凝胶电泳（PFGE）和扩增片段长度多态性（AFLP）分型方法,了解医院鲍氏不动杆菌菌株亲缘性。方法采用NCCLS方法研究药物敏感性;采用PFGE和AFLP技术研究鲍氏不动杆菌基因型;对检测结果作聚合分析讨论菌株亲缘性。结果鲍氏不动杆菌利用PFGE分型可以分为4个亚型、利用AFLP分型可以分为2个亚型;聚合分析具有一致性。结论AFLP分型更具有实用价值。     

Differentiation of highly prevalent IS6110 single-copy strains of Mycobacterium tuberculosis from a rural community in South India with an ongoing DOTS programme.

We have prospectively analysed the DNA fingerprinting of Mycobacterium tuberculosis strains in a rural community from high prevalence area in South India with an ongoing DOTS programme. Strains from 451 culture-positive cases, diagnosed during July 1999-December 2000, were fingerprinted initially by both IS6110 and DR probes followed by polymorphic GC-rich repeat sequences (PGRS) typing only on low-copy strains. The results were correlated with selected epidemiological and clinical data. Forty one percent of strains showed single copy of IS6110, which further got differentiated into 62 DR and 27 PGRS patterns. One predominant DR pattern (5B/2) was found in 20% of the low-copy strains and was also involved in clusters. In all, 183 patients out of 451 (40%) were clustered in total 44 clusters when analysed by IS6110 and DR probes. With additional PGRS typing, the number of patients clustered was further reduced to 106 (23%). More number of patients (131) were clustered in IS6110 single-copy group. The maximum number of clusters was found with two or three patients. Only a small percentage (16%) of the patients reported direct epidemiological links while remaining patients might have had indirect links or casual contacts. Thus, a combination of two to three genetic markers is able to differentiate the most endemic strains of M. tuberculosis in areas with a high incidence of tuberculosis. The epidemiological data do not suggest any major outbreaks or a hot-spot hypothesis of transmission in this region. Phylogenetic analysis using IS6110, DR and PGRS RFLP (restriction fragment length polymorphism, RFLP) fingerprints showed that isolates exhibited clonal evolutionary pattern. The predominance of certain genotypes and agreement between the phylogenetic trees indicated that these strains were closely related and might have evolved or propagated from the common ancestor.     

Molecular epidemiology of Mycobacterium tuberculosis isolates from Kerala,India using IS6110-RFLP,spoligotyping and MIRU-VNTRs

Tuberculosis (TB) continues to be a major health problem in India, and there is very little information about the prevalent genotypes of tubercle bacilli that cause TB in India, especially in Kerala. Our aim was to study the different circulating strains of Mycobacterium tuberculosis (MTB) that are prevalent in Kerala, India. We analyzed 168 MTB isolates from as many pulmonary TB patients using IS6110-RFLP, spoligotyping and MIRU-VNTRs. The results of IS6110-RFLP revealed that majority of isolates had null copy (10.89%) or single copy (44.87%) of IS6110 insertion. Low copy (<6) isolates accounted for 71.5% in the isolates studied. Genotypic clade designations were done by comparing with the SITVIT2 database which showed 68 patterns; of which 51 corresponded to different shared types whereas 17 patterns were orphans. Among the 51 SITs recorded, 42 SITs matched a preexisting SIT in the SITVIT2 database, whereas 9 SITs were newly-created. Majority of the isolates (64.28%) belonged to the ancestral East-African Indian (EAI) lineage. MIRU-40 and 31 (HGDI = 0.6555 and 0.6524) showed highest discrimination, while MIRU-2 and 20 (HGDI = 0.0354 and 0.0696) had the least discriminatory power. ETR-A and B (HGDI 0.7382 and 0.6743) discriminated better as compared to other MIRU loci. The overall HGDI for MIRU-VNTRs at 0.9735 (calculated for 166 isolates) showed a better discriminatory power than spoligotyping used alone. This study of MTB genotypic diversity was useful by providing a first snapshot of circulating MTB genotypic clones in Kerala.     

利用限制性片段长度多态性分析检测乙醛脱氢酶基因2的基因型

人类摄入酒精主要通过Ⅰ型酒精脱氢酶和乙醛脱氢酶共同催化。为建立乙醛脱氢酶基因２（ＡＬＤＨ２）的基因型检测方法，本研究应用限制性片段长度多态性分析法（ＲＦＬＰ－ＰＣＲ）测定ＡＬＤＨ２的基因型。根据ＡＬＤＨ２的基因序理资料，设计一含一个碱基替代的限制性内切酶ＭｂｏⅡ的可识别位点。随后ＤＮＡ模板在下列条件扩增；变性；９４，１ｍｉｎ，退火；５７℃，３ｍｉｎ，延伸；７２℃１ｍｉｎ。３５个循环。聚合酶链反应产     

限制性片段长度多态性分析方法应用于中国麻疹野病毒基因型别的鉴定

目的　建立和应用麻疹野病毒基因型快速诊断方法 ,及时监测麻疹流行株基因型动态 ,尽早发现异型输入病例。方法　应用一种适用于我国现流行麻疹野病毒的基因型别筛查、定型的分析方法 ,即逆转录 聚合酶链反应 限制性片段长度多态性分析方法 (RT PCR RFLP) ,对吉林省 2 0 0 1～ 2 0 0 3年分离到、经中国疾病预防控制中心病毒病预防控制所国家麻疹实验室用脱氧核糖核酸 (DNA)序列分析证实为H1基因型的 9株野病毒进行验证。结果　 9株麻疹病毒分离阳性株的RT PCR-RFLP基因分型结果与核酸序列分析结果完全一致 ,均为H1基因型。并应用该方法对吉林省 2 0 0 3年分离的 2株麻疹病毒进行基因型别鉴定 ,亦为H1基因型。同时对 2 0 0 1～ 2 0 0 3年的 46份麻疹病例的临床标本 ,应用新建立的RT-PCR-RFLP方法直接进行麻疹病毒核糖核酸 (RNA)提取、RT-PCR反应及基因型别鉴定。 46例临床标本经直接RT-PCR扩增后的 31例RT-PCR阳性产物 ,经RFLP法酶切、电泳结果均为H1基因型。结论　RFLP分析方法是一种快速、简便又经济实用的中国麻疹野病毒基因定型筛查方法 ,对快速掌握麻疹病毒基因型流行动态及地理分布 ,以及麻疹野病毒的输入、变异情况 ,具有广泛应用的意义和价值     

Molecular epidemiology of tuberculosis in Prague and South Moravia, Czech Republic: genetic analysis of Mycobacterium tuberculosis isolates by IS6110-RFLP fingerprinting and spoligotyping

OBJECTIVES: To genetically characterize and compare Mycobacterium tuberculosis isolates among culture-confirmed TB cases in two regions in the Czech Republic in 1998. METHODS: Consecutive M. tuberculosis isolates from 111 TB patients in Prague and 120 patients in the South Moravia region were genotyped using the standardized IS6110 Southern blot hybridization method and by spoligotyping. RESULTS: Eighty of the Prague patients (72.1%) had isolates with unique RFLP patterns, while 31 (27.9%) had isolates which belonged to 10 clusters. Seventy-eight (64.7%) of the South Moravia strains displayed unique RFLP pattern and 42 (35.3%) were assigned into 15 clusters. The spoligotype profiles previously identified in the U.S. were found in 69 (33%) samples and newly identified Czech spoligotypes in 24 (11.4%) of the total number of examined strains. CONCLUSIONS: The present population-based molecular epidemiological study performed in two regions of the Czech Republic in 1998 demonstrated the distribution of individual genotypes as well as clustered strains of M. tuberculosis isolated from TB patients, and confirmed the similarity between the Czech strain collection and the European Community TB Database, that includes countries with low TB rate. The sporadic import of TB cases from foreign countries and recent transmission events probably do not play significant roles in the epidemiological situation in the Czech Republic.     

用PCR-限制性长度多态性鉴定结核分枝杆菌和非结核分枝杆菌

目的通过PCR和限制性长度多态性分析,建立鉴定分枝杆菌的PCR-限制性长度多态性分析方法 ,为早期诊断结核分枝杆菌(MTB)与非结核分枝杆菌(NTM)病提供新的工具。方法设计分枝杆菌属特异性通用引物,用MspⅠ对PCR产物进行限制性酶切,对酶切结果进行聚类分析,建立鉴定分枝杆菌的PRA方法。结果本实验所设计的一对引物具有良好的通用性和特异性,PRA法鉴定98株分枝杆菌的结果与传统鉴定法完全一致,其灵敏度、特异度和准确度均为100%,方法学评价指标结果达到诊断性实验的要求。结论 PRA法快速灵敏,可直接检测标本中的分枝杆菌而无需培养增菌,其成本低廉、结果准确,不会因耐药突变而影响结果判断。     

Random Amplified Polymorphic DNA Typing of Clinical and Environmental Aeromonas hydrophila Strains from Limpopo Province, South Africa

The aim of the present study was to determine the genetic relatedness of strains isolated from diarrhoeal stool and water specimens collected from water-storage containers from different geographical areas in the Limpopo province. In total, 32 Aeromonas strains isolated from stool specimens collected from HIV/AIDS patients suffering from gastroenteritis and their household drinking-water stored in 20-L and 25-L containers were analyzed by random amplified polymorphic DNA PCR (RAPD). The RAPD fingerprints obtained proved reproducible when repeated on three different occasions using whole-cell DNA isolated from the Aeromonas strains. In total, 12 unique RAPD fingerprints were found. The results revealed a tendency of the isolates to cluster according to their origin of isolation (best-cut test 0.80 and bootstrap values >50%). However, a certain degree of similarity was also observed between isolates of water sources and clinical sources which indicated genetic relatedness. There were also genetic similarities between the clinical and the environmental strains of Aeromonas spp. isolated from different geographical areas. This study has demonstrated the genetic relatedness of Aeromonas hydrophila isolates from household drinking-water and clinical sources in South Africa, which may be due to cross-contamination from water to patients or vice-versa. This observation is of public-health significance, particularly in the era of HIV/AIDS. This study points to the importance of monitoring and evaluating infection-control measures for improved hygiene and to prevent cross-contaminations.Key words: Aeromonas, Aeromonas hydrophila, Diarrhoea, Genotyping, South Africa     

IS6110限制性片段多态性分析标准方法的建立及其在结核分枝杆菌分子分型中的应用

目的 建立IS6110限制性片段多态性分析(IS6110-RFLP)标准方法 并评价该方法 的分型能力.方法 采用核酸提取、PCR、限制性内切酶分析、Southern杂交、琼脂糖凝胶电泳等技术,结合Gel-Pro analyzer 3.1和BioNumeries(Version 5.0)软件,对78株结核分枝杆菌插入序列IS6110-RFLP进行分析.结果 确定标准化的IS6110-RFLP技术,包括核酸提取、PCR、限制性内切酶分析、Southern杂交、琼脂糖凝胶电泳等实验步骤及标化参数的相关数据分析软件的使用;采用该技术,将78株结核分枝杆菌分为75个不同的基因型,分别归属于11个基因簇,其中有52株归属于同一个基因簇,占菌株总数的66.7%(52/78).结论 建立标准化的IS6110-RFLP技术方案,该方法 具有很强的基因分型和株水平鉴定能力,可用于结核病的病原学监测.     

河南省结核分枝杆菌IS6110DNA指纹图谱特征分析

目的：从分子流行病学角度探讨河南省结核分支杆菌的分布特征。方法：样本的获得采用全省范围等比例分层整群随机抽样;构建以IS6110 RFLPDNA指纹方法和以DR为基础的Spoligotyping DNA指纹方法;采用Gel compare4．1软件对DNA指纹图谱进行聚类（cluster）分析。结果：共获得66株可进行IS6110 RFLP DNA指纹分析的结核分支杆菌;其中59．09％（39／66）用Spoligotyping DNA指纹方法鉴定为“北京基因型”菌株。结论：北京基因型结核分支杆菌在河南省呈较高水平的流行。     

用IS6110限制性片段长度多态性方法分析中国南方部队结核分支杆菌DNA指纹特征

目的：分析南方部队结核病患者和当地患者中结核分支杆菌分离株DNA指纹特征，探讨南方部队结核病的分子流行病学特征。方法：用限制性内切酶PvuⅡ消化结核分支杆菌DNA，后用琼脂糖凝胶电泳，再用Southern免疫转印，用[α^32P]-dCTP标记的DNA IS6110序列中的245bp片段作探针，进行杂交后得到限制性片段长度多态性图谱，结合一般流行病学资料加以分析比较。结果：共检测185株结核分支杆菌分离株。检测菌株的IS6110拷贝数范围为1～22。部队患者和当地患者的IS6110拷贝数分布差异无显著姓。部队患者结核菌分离株的IS6110拷贝数主要集中在6～20个，当地分离株主要集中在7～20个；全部菌株指纹特征分成8个组，部队分离株和当地分离株均主要集中在Ⅰ、Ⅱ、Ⅲ 3个组里。耐药菌株指纹特征在各组中的分布与敏感菌株差异有显著性；患者是否接种卡介苗在各组中的分布差异无显著性。结论：南方部队患者与当地患者结核菌分离株在遗传关系上较接近，在基因水平上相关程度较强。提示部队结核病的发生与当地结核分支杆菌菌株的传播密切相关。     

限制性酶切片段长度多态性分析用于乙型流行性感冒病毒巴拿马株与维多利亚株的快速鉴定

利用限制性酶切片段长度多态性分析(RFLP)鉴别乙型流行性感冒(流感)病毒的巴拿马株与维多利亚株,对乙型流感病毒血凝素(HA)基因采用逆转录-聚合酶链反应(RT-PCR)扩增后,用HindⅢ做酶切反应并进行琼脂糖凝胶电泳.结果显示:乙型流感病毒维多利亚株或巴拿马株HA基因均能被特异性引物所扩增,且与甲1与甲3型流感病毒无交叉反应.该片段经HindⅢ酶切后,乙型流感病毒巴拿马株在电泳谱上出现603bp与242bp的2个片段,而乙型流感病毒维多利亚株在该片段无HindⅢ酶切位点,仍呈872bp的一个片段.表明该方法不仅可作为常规血清学方法的补充,对乙型流感病毒维多利亚株与巴拿马株作出正确判定,而且可快速敏感地从临床标本中直接对两类乙型流感毒株进行鉴别.     

用PCR/RFLP技术对黑龙江沿岸蜱类和鼠类中北亚蜱传斑点热的检测

为了解黑龙江沿岸部分地区斑点热自然疫源地存在情况，作者用PCR／RFLP的方法检测该地区蜱类及鼠类中的斑点热群（spottedfevergroup，SFG）立克次体。结果从该地区的森林革蜱、嗜群血蜱、黑线姬鼠、东方田鼠、麝鼠及棕背中均扩增出了斑点热群立克次体的特异片段，而对斑疹伤寒立克次体、恙虫病立克欢体、Q热立克次体则为阴性。PCR产物经PstⅠ及RsaⅠ酶切后发现它们的酶切图谱与西伯利亚立克次体完全相同，而有别于其它斑点热群立克次体标准株。作者认为黑龙江沿岸调查点可能存在北亚蜱传斑点热的自然疫源地。