Kinetics of Leptospira interrogans Infection in Hamsters after Intradermal and Subcutaneous Challenge

Abstract

BackgroundLeptospirosis is a zoonosis caused by highly motile, helically shaped bacteria that penetrate the skin and mucous membranes through lesions or abrasions, and rapidly disseminate throughout the body. Although the intraperitoneal route of infection is widely used to experimentally inoculate hamsters, this challenge route does not represent a natural route of infection.Methodology/Principal FindingsHere we describe the kinetics of disease and infection in hamster model of leptospirosis after subcutaneous and intradermal inoculation of Leptospira interrogans serovar Copenhageni, strain Fiocruz L1-130. Histopathologic changes in and around the kidney, including glomerular and tubular damage and interstitial inflammatory changes, began on day 5, and preceded deterioration in renal function as measured by serum creatinine. Weight loss, hemoconcentration, increased absolute neutrophil counts (ANC) in the blood and hepatic dysfunction were first noted on day 6. Vascular endothelial growth factor, a serum marker of sepsis severity, became elevated during the later stages of infection. The burden of infection, as measured by quantitative PCR, was highest in the kidney and peaked on day 5 after intradermal challenge and on day 6 after subcutaneous challenge. Compared to subcutaneous challenge, intradermal challenge resulted in a lower burden of infection in both the kidney and liver on day 6, lower ANC and less weight loss on day 7.Conclusions/SignificanceThe intradermal and subcutaneous challenge routes result in significant differences in the kinetics of dissemination and disease after challenge with L. interrogans serovar Copenhageni strain Fiocruz L1-130 at an experimental dose of 2×106 leptospires. These results provide new information regarding infection kinetics in the hamster model of leptospirosis.

Real-Time PCR Reveals Rapid Dissemination of Leptospira interrogans after Intraperitoneal and Conjunctival Inoculation of Hamsters

“…1). Similar to what was found in other studies (15,19), our final bacterial burdens before death ( Fig. 1 and 4 and Table 2) were similar among the different doses and routes of infection.…”

“…Little is known about the rates of spread to various tissues and their consequences for the pathogenesis of the disease. Recent studies have shown that different routes of infection result in changes in dissemination kinetics (15,19). However, given the use of different animal models and methods of detection of the agent, major questions remain regarding the effect of the dose on dissemination and the relevance of this approach to understanding pathogenesis.…”

“…Leptospires can be detected in the bloodstream within minutes after intraperitoneal (i.p.) inoculation (14) and are present in visceral organs 2 days later (13,(15)(16)(17)(18)(19), reaching a range of 10 6 to 10 7 organisms per milliliter of blood or per gram of tissue of patients and animals (16,19,20). In 1957 and 1964, Faine (17) and Green and Arean (18) studied the kinetics of the leptospiral infection using dark-field microscopy and culture, respectively.…”

“…Although experimental inoculation is typically performed by intraperitoneal inoculation (24,25), this route does not reflect natural transmission of the pathogen. Relatively few studies have examined challenge routes that mimic natural entry of leptospires via the skin or mucous membranes (15,19,26,27). Although quantitative-PCR assays have been extensively evaluated as a diagnostic tool, few studies have applied the technique to pathogenesis studies in animal models of leptospirosis.…”

Leptospira Infection Interferes with the Prothrombinase Complex Assembly during Experimental Leptospirosis

“…After that, we noted the gradual clearance of the leptospires from the lungs and livers, while bacteria apparently persisted on the kidneys, as previously reported (Ko et al, 2009; Coutinho et al, 2014). The progression of the disease was associated with tissue pathologies and marked alterations of liver, kidney, and lung structures.…”