Isolation and characterization of toxigenic Corynebacterium ulcerans from 2 closed colonies of cynomolgus macaques (Macaca fascicularis) in Japan

Abstract

The aim of the present study was to determine the prevalence of infection by toxigenic Corynebacterium ulcerans in cynomolgus macaques (Macaca fascicularis) housed in an animal facility in Japan. Samples from the pharynges of animals from 2 closed colonies (colony A, n = 47; colony B, n = 21) were cultured. C. ulcerans grew from 43% and 47% of the samples from colonies A and B, respectively. The toxigenicity of these isolates was assessed by using PCR analysis for the diphtheria toxin gene and the Elek test and Vero cytotoxicity assay to detect diphtheria toxin. The proportion of macaques harboring toxigenic C. ulcerans was 6% in colony A and 29% in colony B. Analysis of diphtheria antitoxin neutralization titers in the sera revealed that 23% and 33% of macaques from colonies A and B, respectively, had a history of infection with toxigenic C. ulcerans. Pulsed-field gel electrophoresis of the toxigenic isolates showed that all of those recovered from macaques in colony B showed an identical genotype, suggesting that transmission of the organism occurred within the colony. However, isolates from colony A macaques showed 3 different genotypes, one of which was identical to the isolate from colony B. Additional studies evaluating the prevalence and transmission of toxigenic C. ulcerans within colonies of nonhuman primates are necessary to help control the spread of the infection. The current study is the first description of the isolation and characterization of toxigenic C. ulcerans from nonhuman primates in Japan.

Figure 1.

PFGE patterns of the 9 toxigenic C. ulcerans isolates from cynomolgus macaques derived from 2 different closed breeding colonies in Japan (colony A and colony B). Toxigenic isolates, MT11, 122 and 128 were isolated from colony A macaques, while MA150, 153, 154, 156, 160 and 162 were isolated from colony B macaques. Five nontoxigenic isolates were analyzed as references. A) PFGE patterns. Genomic DNA was digested with SfiI and subjected to PFGE as described in the Materials and Methods. Lambda phage DNA ladders were used as molecular mass markers. B) Phylogenetic analysis. Similarities between the PFGE patterns of the different isolates were analyzed using the UPGME method.