Koizumi Nobuo, Muto Maki Mizutani, Izumiya Hidemasa, Suzuki Motoi, Ohnishi Makoto
Department of Bacteriology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku, Tokyo 162-8640, Japan.
Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, Nagasaki 852-8523, Japan.
J Med Microbiol. 2015 Mar;64(Pt 3):288-294. doi: 10.1099/jmm.0.000027. Epub 2015 Jan 16.
Canine leptospirosis occurs worldwide; however, information on the relationship between Leptospira serotypes/genotypes and virulence in dogs remains limited. We investigated the molecular characteristics of Leptospira interrogans canine isolates belonging to three serogroups using multiple-locus variable-number tandem repeat analysis (MLVA) and the effects of each serotype/genotype on the clinical characteristics of leptospirosis in dogs. MLVA using 11 loci of the three major L. interrogans serogroups in Japan, Australis (32 strains from 21 dogs), Autumnalis (12; 7) and Hebdomadis (66; 39), revealed more divergent genetic heterogeneity within each serogroup than multilocus sequence typing (MLST), and they formed two, three and five clusters (CLs), respectively. Lethal infections were caused by all Leptospira serogroup isolates (70.3 % with Hebdomadis, 83.3 % with Australis and 100 % with Autumnalis) or Leptospira isolates belonging to all the CLs (57.1-100 %) without any significant differences. A significant difference in hyperaemia and haemorrhage of mucus membrane was observed between serogroups Australis and Autumnalis (P = 0.03). Leptospira isolates of Australis CL2 caused no hyperaemia and haemorrhage from mucus membrane, whereas those of Australis CL1, Autumnalis CL3 and Hebdomadis CL1 and CL3 did (P<0.05). Significant differences in creatinine (Cre) levels were observed between serogroups Australis and Hebdomadis (P = 0.02). In addition, significant differences in blood urea nitrogen levels were observed between serogroups Australis and Hebdomadis (P = 0.004) and Australis and Autumnalis (P = 0.02). Based on MLVA types, a significant difference in Cre levels was observed between Hebdomadis CL1 and CL4 (P = 0.0018). Our results indicated that MLVA had a higher discriminatory power and was more concordant with serotyping than MLST. Although all Leptospira serotypes and genotypes caused lethal infections in dogs, the L. interrogans serogroup Australis strains were more likely to cause severe kidney damage than Autumnalis and Hebdomadis, which may be more critical to the outcome of infected dogs than haemorrhage. Our results also suggest that the virulence mechanisms and target organs in dogs may differ by Leptospira genotype.
犬钩端螺旋体病在全球范围内均有发生；然而，关于钩端螺旋体血清型/基因型与犬类毒力之间关系的信息仍然有限。我们使用多位点可变数目串联重复序列分析（MLVA）研究了属于三个血清群的问号钩端螺旋体犬分离株的分子特征，以及每种血清型/基因型对犬钩端螺旋体病临床特征的影响。对日本三个主要问号钩端螺旋体血清群的11个位点进行MLVA分析，其中澳洲群（来自21只犬的32株菌株）、秋季群（12株；7只犬）和七日热群（66株；39只犬），结果显示每个血清群内的遗传异质性比多位点序列分型（MLST）更为明显，它们分别形成了两个、三个和五个簇（CL）。所有钩端螺旋体血清群分离株（七日热群为70.3%，澳洲群为83.3%，秋季群为100%）或属于所有CL的钩端螺旋体分离株（57.1 - 100%）均导致了致命感染，且无显著差异。在澳洲群和秋季群之间观察到黏膜充血和出血存在显著差异（P = 0.03）。澳洲群CL2的钩端螺旋体分离株未引起黏膜充血和出血，而澳洲群CL1、秋季群CL3以及七日热群CL1和CL3的分离株则引起了充血和出血（P<0.05）。在澳洲群和七日热群之间观察到肌酐（Cre）水平存在显著差异（P = 0.02）。此外，在澳洲群和七日热群之间（P = 0.004）以及澳洲群和秋季群之间（P = 0.02）观察到血尿素氮水平存在显著差异。基于MLVA类型，在七日热群CL1和CL4之间观察到Cre水平存在显著差异（P = 0.0018）。我们的结果表明，MLVA具有更高的鉴别力，并且与血清分型相比，比MLST更具一致性。尽管所有钩端螺旋体血清型和基因型都能导致犬类致命感染，但问号钩端螺旋体澳洲群菌株比秋季群和七日热群更易引起严重的肾脏损伤，这对感染犬的预后可能比出血更为关键。我们的结果还表明，犬类中钩端螺旋体的毒力机制和靶器官可能因基因型而异。
