Figure 7.

Reduced histopathologic injury and invasion of ΔhslUV mutant in hamsters. (A) Attenuated histopathologic injury in the ΔhslUV mutant-infected hamsters, examined by microscopy after hematoxylin and eosin staining. The wild-type strain- or CΔhslUV mutant-infected hamsters showed the visible congestion (3 days), hemorrhage (7 days) and inflammatory cell infiltration (3 and 7 days) in lungs; inflammatory cell infiltration (3 and 7 days) and focal hepatocyte necrosis (7 days) in liver; and congestion and inflammatory cell infiltration (3 days), and serious congestion and focal nephric tubular epithelial cell necrosis (3 and 7 days) in kidney. In contrast, the histopathologic injury in the ΔhslUV mutant-infected hamsters was markedly attenuated. (B) Decreased invasion in the lungs, liver and kidneys of ΔhslUV mutant-infected hamsters, assessed by microscopy after silver staining. The arrows indicate the leptospires in tissues. (C) Fewer colonies from the lung, liver and kidney samples of ΔhslUV mutant-infected hamsters, determined by CFU enumeration. *P<0.05 vs the CFU number of wild-type L. interrogans strain Lai and the CΔhslUV mutant. (D) Fewer colonies from the peripheral blood samples of ΔhslUV mutant-infected hamsters, determined by CFU enumeration. *P<0.05 vs the CFU number of wild-type L. interrogans strain Lai and the CΔhslUV mutant. (E) Decreased leptospiral loading in urine from ΔhslUV mutant-infected hamsters, examined by microscopy after silver staining. The urine samples were condensed by 50-fold (at 7 days during infection) and 5-fold (at 14 days during infection) in volume for leptospiral counting. (F) Decreased leptospiral numbers in the urine from ΔhslUV mutant-infected hamsters. Statistical data from experiments such as shown in E. Bars show the means±sd of three separate samples of at least five animals. *P<0.05 vs the leptospiral number in the urine samples from wild-type L. interrogans strain Lai- or the CΔhslUV mutant-infected animals.