Gene Sequencing and Phylogenetic Analysis: Powerful Tools for an Improved Diagnosis of Fish Mycobacteriosis Caused by Mycobacterium fortuitum Group Members

Abstract

The Mycobacterium fortuitum group (MFG) consists of about 15 species of fast-growing nontuberculous mycobacteria (NTM). These globally distributed microorganisms can cause diseases in humans and animals, especially fish. The increase in the number of species belonging to MFG and the diagnostic techniques panel do not allow to clarify their real clinical significance. In this study, biomolecular techniques were adopted for species determination of 130 isolates derived from fish initially identified through biochemical tests as NTM belonging to MFG. Specifically, gene sequencing and phylogenetic analysis were used based on a fragment of the gene encoding the 65 KDa heat shock protein (hsp65). The analyzes made it possible to confirm that all the isolates belong to MFG, allowing to identify the strains at species level. Phylogenetic analysis substantially confirmed what was obtained by gene sequencing, except for six strains; this is probably due to the sequences present in NCBI database. Although the methodology used cannot represent a univocal identification system, this study has allowed us to evaluate its effectiveness as regards the species of MFG. Future studies will be necessary to apply these methods with other gene fragments and to clarify the real pathogenic significance of the individual species of this group of microorganisms.

Clinical Relevance and Environmental Prevalence of Mycobacterium fortuitum Group Members. Comment on Mugetti et al. Gene Sequencing and Phylogenetic Analysis: Powerful Tools for an Improved Diagnosis of Fish Mycobacteriosis Caused by Mycobacterium fortuitum Group Members. Microorganisms 2021, 9, 797

“…Prior to a study by Mugetti et al [1], only M. fortuitum, M. peregrinum, M. porcinum, M. septicum and M. setense were described as fish pathogens. In their study, Mugetti et al [1] described for the first time five MFG members (M. alvei, M. arceuilense, M. brisbanense, M. conceptionense and M. senegalense) as species isolated from fish with mycobacteriosis (Table 1). These five MFG species were isolated from 10 genera of freshwater fish originally living in tropical and temperate zones.…”

“…Never reported Camels' milk isolates [5] For the first time reported in infected fish [1] Reported [4] 4 (3.1)…”

“…Rare pulmonary and extrathoracic pathogen [3] Never reported Fish directed for consumption [7], for the first time reported in infected fish [1] Reported [8] 4 (3.1)…”

“…Rare pulmonary and extrathoracic pathogen [14][15][16][17] Domestic and wild mammal pathogen [18][19][20][21][22] Fish pathogen [1,23] Reported [24] 38 (29.2)…”

“…We would like to comment on a recent article published in your journal by Mugetti et al [1]. This article is well written and discusses the diagnostics of all 17 members of the Mycobacterium fortuitum Group (MFG) currently known.…”