Mycobacterium massiliense is an environmental opportunistic pathogen that has been associated with soft tissue infection after minor surgery. We studied the acute immune response of C57BL/6 and BALB/c mice infected intravenously with 10 6 CFU of an M. massiliense strain isolated from a nosocomial infection in Brazil. The results presented here show that M. massiliense is virulent and pathogenic to both C57BL/6 and BALB/c mice, inducing a granulomatous inflammatory reaction that involves the activation of macrophages, dendritic cells, and natural killer cells induced by gamma interferon and interleukin-17 (IL-17) in C57BL/6 mice and by IL-12 in BALB/c mice.Mycobacteria that do not belong to the complex Mycobacterium tuberculosis are known as nontuberculous mycobacteria (NTM) or atypical mycobacteria. NTM are ubiquitous microorganisms found worldwide in soil and water (3,23,38). These environmental mycobacteria are considered emerging and environmental opportunistic pathogens (6, 23).Mycobacterium massiliense is an environmental nonphotochromogenic, rapidly growing Mycobacterium strain that has been associated with soft-tissue infection after minor surgery or intramuscular injection (3,5,17,22,26,46) and with pulmonary infection due to diseases, such as cystic fibrosis (29,41). This species differs only slightly from Mycobacterium abscessus, sharing a 99.6% sequence identity of their 16S rRNA genes; genetic differences can be observed by comparative sequence analysis of the rpoB and hsp65 genes (1,25,42). Infections with these agents tend to respond poorly to macrolidebased chemotherapy (3), even though the organisms are susceptible to clarithromycin (15,44,47).M. massiliense infection mainly affects immunocompetent individuals and occasionally is associated with disseminated disease (8). An outbreak of M. massiliense occurred in Goiania, Brazil, where 30 individuals were infected after undergoing knee joint and laparoscopic surgery (5). Despite the fact that the infected individuals were from different hospitals, a unique M. massiliense strain was identified and characterized by pulsed-field gel electrophoresis.Disease pathogenesis involves host-pathogen interactions that directly affect parasite clearance. Typically, when environmental bacteria are passively introduced into the host, rapid bacterial clearance occurs due to an efficient innate immune response (30). Nonetheless, accidental infections with M. massiliense have been described as having a chronic evolution and, in some cases, the disease is disseminated irrespective of the host's immune status. Such findings raise the possibility that this species is more virulent and/or pathogenic than other environmental mycobacteria, such as M. chelonae and M. abscessus.Recently, a murine model of M. abscessus infection was described, and isogenic mice were shown to be good models to address the immune response of the host (34, 39). In the present study, we analyzed the immune response of C57BL/6 and BALB/c mice infected with a clinical isolate of M. massiliense ob...
Tuberculosis is a disease that infects approximately two billion people worldwide. The current diagnostic test utilizes purified protein derivative (PPD) obtained from Mycobacterium tuberculosis cultures to elicit a host delayed type hypersensitivity reaction to identify infected individuals. This reaction is manifested as an induration at 48 hours following intradermal i njection. These experiments demonstrate that in a mouse model, repeated administrations of PPD do not elicit a positive tuberculin skin test (TST). However, prior sensitization to environmental mycobacteria does induce a positive TST when administered via the intraperitoneal or oral route. This work has important implications regarding the specificity of the PPD reagent, disease diagnosis, and environmental mycobacteria.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.