title: High virulence in hamsters of four dominant Leptospira serovars isolated from rats in the Philippines.
abstract: Leptospirosis is caused by pathogenic species of Leptospira. The aim of this study was to determine and characterize the pathogenicity of four dominant Leptospira isolates prevailing among rats in the Philippines. The isolates were Leptospira interrogans serovar Manilae strain K64, L. interrogans serovar Losbanos strain K37, L. interrogans serovar Ratnapura strain K5 and Leptospira borgpetersenii serovar Javanica strain K6. Pathogenicities were studied using hamsters, which reproduce severe human leptospirosis. The minimum lethal doses were 10(0) ( = 1) leptospires for K64, K37 and K5, and 10(1) leptospires for K6. Weight loss amongst the Leptospira-infected hamsters was observed from 1 day before death (K64-, K37- and K5-infected hamsters) to as much as 1 week before death for K6-infected hamsters. Similar and varied gross and microscopic lesions were observed amongst infected hamsters, even for strains belonging to the same species (i.e. L. interrogans). The most significant and common histopathological findings were congestion of the glomerulus, disarrangement of hepatic cords and erythrophagocytosis. Other findings were foamy splenic macrophages for K6, severe petechial pulmonary haemorrhage for K64, and hematuria and severe pulmonary congestion for K37. Immunostaining and culture revealed the presence of leptospires in different organs of the infected hamsters. Based on these results, Leptospira isolates from rats in the Philippines were shown to be highly virulent, causing pulmonary haemorrhage, severe hepato-renal damage and death in hamsters even at lower doses. The present findings on experimental leptospirosis support clinical data showing that patients with severe manifestations of leptospirosis, such as pulmonary haemorrhage, are increasing in the Philippines. These findings may serve as a basis to strengthen the early diagnosis and treatment of human leptospirosis.
authors.affiliation: Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Sharon Y A M
authors.initials: SYAM
authors.lastname: Villanueva
authors.affiliation: Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Saito
authors.affiliation: Department of Pathology, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tsutsumi
authors.affiliation: Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Takaya
authors.initials: T
authors.lastname: Segawa
authors.affiliation: Department of Medical Microbiology, College of Public Health, University of the Philippines-Manila, Manila 1000, Philippines.
authors.forename: Rubelia A
authors.initials: RA
authors.lastname: Baterna
authors.affiliation: Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Antara
authors.initials: A
authors.lastname: Chakraborty
authors.affiliation: Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Tatsuma
authors.initials: T
authors.lastname: Asoh
authors.affiliation: Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Miyahara
authors.affiliation: Department of Medical Microbiology, College of Public Health, University of the Philippines-Manila, Manila 1000, Philippines.
authors.forename: Yasutake
authors.initials: Y
authors.lastname: Yanagihara
authors.affiliation: Department of Medical Microbiology, College of Public Health, University of the Philippines-Manila, Manila 1000, Philippines.
authors.forename: Lolita L
authors.initials: LL
authors.lastname: Cavinta
authors.affiliation: Department of Medical Microbiology, College of Public Health, University of the Philippines-Manila, Manila 1000, Philippines.
authors.forename: Nina G
authors.initials: NG
authors.lastname: Gloriani
authors.affiliation: Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Yoshida
mesh_terms: D000825:Animal Structures / Q000382:microbiology / Q000473:pathology; D000818:Animals; D001835:Body Weight; D006224:Cricetinae; D004195:Disease Models, Animal; D007919:Leptospira / Q000145:classification / Q000302:isolation & purification* / Q000472:pathogenicity*; D007922:Leptospirosis / Q000382:microbiology* / Q000473:pathology*; D010679:Philippines; D051381:Rats; D012703:Serotyping; D016019:Survival Analysis; D014774:Virulence