The pathogenicity of Malaysian isolates of Orientia tsutsugamushi was investigated by a mouse virulence assay. The isolates could be differentiated as low (4 isolates), moderately (3 isolates) and highly virulent (2 isolates) based on the different responses in infected mice. No direct correlation between severity of human scrub typhus infections and virulence of the O. tsutsugamushi in mice was observed. Mice infected with virulent strains of O. tsutsugamushi showed splenomegaly, ascitis accumulation and enlargement of kidneys and livers whereas avirulent O. tsutsugamushi strains were asymptomatic and exhibited ruffled fur for a short period after infection. There was low antibody response in mice infected with isolates of low pathogenicity as compared with those of highly virulent isolates. Upon dissection of the infected mice, enlargement of mouse organs such as spleen, kidney and liver was noted. Presence of rickettsemia in mice was confirmed by the growth of O. tsutsugamushi in the L929 cells when inoculated with blood from infected mice. O. tsutsugamushi was also cultured from the peritoneal exudates of the infected mice. However, DNA of O. tsutsugamushi was only detected in the peritoneal exudates (by PCR) and blood (by cell culture) and not from other tissue samples.
Eighty-six clinical isolates of Aeromonas hydrophila were studied for their ability to produce four exotoxins: a haemolysin active against rabbit erythrocytes, cytotoxin and enterotoxin detectable with Vero cell cultures, and the cholera toxin-like factor detected by an enzyme-linked immunosorbent assay. At least one exotoxin was produced by 80% of enteric and 96% of non-enteric isolates. The exotoxin profiles of non-enteric isolates were more restricted than those of enteric isolates, with haemolysin and cytotoxin producers preponderant. Although haemolysin and cytotoxin were produced by isolates from all sources, the enterotoxin and cholera toxin-like factor were more common amongst enteric isolates. The production of haemolysin and cytotoxin were closely related but the association between the enterotoxin and the cholera toxin-like factor was not significant.
Peritonitis is the leading complication of peritoneal dialysis, which is primarily caused by bacteria rather than fungi. Peritonitis is responsible for approximately 18% of the infection-related mortality in peritoneal dialysis patients. In this paper, we report the isolation of a rare fungus, Quambalaria cyanescens, from the peritoneal fluid of a man after he switched from continuous ambulatory peritoneal dialysis to nocturnal intermittent peritoneal dialysis. Based on the morphological examination and multigene phylogeny, the clinical isolate was confirmed as Q. cyanescens. This pathogen exhibited low sensitivity to all tested echinocandins and 5-flucytosine. Interestingly, morphological characterization revealed that Q. cyanescens UM 1095 produced different pigments at low temperatures (25°C and 30°C) on various culture media. It is important to monitor the emergence of this rare fungus as a potential human pathogen in the tropics. This study provides insight into Q. cyanescens UM 1095 phenotype profiles using a Biolog phenotypic microarray (PM). Of the 760 nutrient sources tested, Q. cyanescens UM 1095 utilized 42 compounds, and the fungus can adapt to a broad range of osmotic and acidic environments. To our knowledge, this is the first report of the isolation of Q. cyanescens from peritoneal fluid, revealing this rare fungus as a potential human pathogen that may be misidentified using conventional methods. The detailed morphological, molecular and phenotypic characterization of Q. cyanescens UM 1095 provides the basis for future studies on its biology, lifestyle, and potential pathogenicity.