Comparison of Macrophage Immune Responses and Metabolic Reprogramming in Smooth and Rough Variant Infections of Mycobacterium mucogenicum.

Minji Kang,Byung Soo Lee,A-Reum Yu,Sung Ki Lee,Hwan-Woo Park,Jong-Seok Kim,Jeong Seong Yang,Ji Won Lee,Jake Whang,Seungwan Lee,Ho Won Kim,Hoe Sun Yoon,Seung Heon Lee

doi:10.3390/ijms23052488

Abstract

Mycobacterium mucogenicum (Mmuc), a rapidly growing nontuberculous mycobacterium (NTM), can infect humans (posttraumatic wound infections and catheter-related sepsis). Similar to other NTM species, Mmuc exhibits colony morphologies of rough (Mmuc-R) and smooth (Mmuc-S) types. Although there are several case reports on Mmuc infection, no experimental evidence supports that the R-type is more virulent. In addition, the immune response and metabolic reprogramming of Mmuc have not been studied on the basis of morphological characteristics. Thus, a standard ATCC Mmuc strain and two clinical strains were analyzed, and macrophages were generated from mouse bone marrow. Cytokines and cell death were measured by ELISA and FACS, respectively. Mitochondrial respiration and glycolytic changes were measured by XF seahorse. Higher numbers of intracellular bacteria were found in Mmuc-R-infected macrophages than in Mmuc-S-infected macrophages. Additionally, Mmuc-R induced higher levels of the cytokines TNF-α, IL-6, IL-12p40, and IL-10 and induced more BMDM necrotic death. Furthermore, our metabolic data showed marked glycolytic and respiratory differences between the control and each type of Mmuc infection, and changes in these parameters significantly promoted glucose metabolism, extracellular acidification, and oxygen consumption in BMDMs. In conclusion, at least in the strains we tested, Mmuc-R is more virulent, induces a stronger immune response, and shifts bioenergetic metabolism more extensively than the S-type. This study is the first to report differential immune responses and metabolic reprogramming after Mmuc infection and might provide a fundamental basis for additional studies on Mmuc pathogenesis.

Highlights

Nontuberculous mycobacteria (NTMs) are common in nature and exist in water sources, soil, and vegetation as environmental organisms
Most nontuberculous mycobacterium (NTM) that cause infections are challenging to treat and worsen the patient’s prognosis because they are resistant to the first-line drug for tuberculosis [4]. According to their growth rate, NTMs that grow on the media within or after 7 days are defined as rapidly growing mycobacteria (RGM) and slowly growing mycobacteria (SGM), respectively [5]
Determinants of respiratory and acidification parameters were calculated using the following equation (Supplemental Table S1). These results suggest that R-type Mycobacterium mucogenicum (Mmuc) is more virulent and induces a stronger immune response than S-type Mmuc, similar to other NTM species, such as M. avium complex and M. abscessus complex

Summary

Introduction

Nontuberculous mycobacteria (NTMs) are common in nature and exist in water sources, soil, and vegetation as environmental organisms. Relatively few species of NTMs cause disease in human, the incidence of human NTM infection appears to have increased significantly in recent decades due to causes such as an aging population, immunosuppression, and broad-spectrum antibiotic use [1–3]. Most NTMs that cause infections are challenging to treat and worsen the patient’s prognosis because they are resistant to the first-line drug for tuberculosis [4]. According to their growth rate, NTMs that grow on the media within or after 7 days are defined as rapidly growing mycobacteria (RGM) and slowly growing mycobacteria (SGM), respectively [5]. Mycobacterium mucogenicum (Mmuc) belongs to the RGM group [6]

Methods

Results

Conclusion