Proposal to elevate the genetic variant MAC-A, included in the Mycobacterium avium complex, to species rank as Mycobacterium chimaera sp. nov.
The possibility that the strains included within the Mycobacterium avium complex (MAC), but not belonging either to M. avium or to Mycobacterium intracellulare, may be members of undescribed taxa, has already been questioned by several taxonomists. A very homogeneous cluster of 12 strains characterized by identical nucleotide sequences both in the 16S rDNA and in the 16S-23S internal transcribed spacer was investigated. Similar strains, previously reported in the literature, had been assigned either to the species M. intracellulare on the basis of the 16S rDNA similarity or to the group of MAC intermediates. However, several phenotypical and epidemiological characteristics seem to distinguish these strains from all other MAC organisms. The unique mycolic acid pattern obtained by HPLC is striking as it is characterized by two clusters of peaks, instead of the three presented by all other MAC organisms. All of the strains have been isolated from humans and all but one came from the respiratory tract of elderly people. The clinical significance of these strains, ascertained for seven patients, seems to suggest an unusually high virulence. The characteristics of all the strains reported in the literature, genotypically identical to the ones described here, seem to confirm our data, without reports of isolations from animals or the environment or, among humans, from AIDS patients. Therefore, an elevation of the MAC variant was proposed and characterized here, with the name Mycobacterium chimaera sp. nov.; this increases the number of species included in the M. avium complex. The type strain is FI-01069T (=CIP 107892T=DSM 44623T).
Regional Reference Center for Mycobacteria, Microbiology and Virology Laboratory, Careggi Hospital, 50134 Florence, Italy.
Enrico
E
Tortoli
Department of Experimental Pathology, Medical Biotechnologies, Infectivology and Epidemiology, University of Pisa, 56127 Pisa, Italy.
Laura
L
Rindi
Department of Preventive Medicine, Autonoma University of Madrid, 28029 Madrid, Spain.
Maria J
MJ
Garcia
Microbiology and Virology Laboratory, S. Camillo-Forlanini Hospitals, 00149 Rome, Italy.
Patrizia
P
Chiaradonna
Department of Public Health, University of Florence, 50134 Florence, Italy.
Rosanna
R
Dei
Department of Experimental Pathology, Medical Biotechnologies, Infectivology and Epidemiology, University of Pisa, 56127 Pisa, Italy.
Carlo
C
Garzelli
German Collection of Microorganisms and Cell Cultures, 38124 Braunschweig, Germany.
Reiner M
RM
Kroppenstedt
Department of Experimental Pathology, Medical Biotechnologies, Infectivology and Epidemiology, University of Pisa, 56127 Pisa, Italy.
Nicoletta
N
Lari
Clinical Laboratory, Campo di Marte Hospital, 55100 Lucca, Italy.
Romano
R
Mattei
Genetics and Cytogenetics Unit, Careggi Hospital, 50134 Florence, Italy.|Regional Reference Center for Mycobacteria, Microbiology and Virology Laboratory, Careggi Hospital, 50134 Florence, Italy.
Alessandro
A
Mariottini
Microbiological and Virological Serum-immunology Laboratory, Careggi Hospital, 50134 Florence, Italy.|Regional Reference Center for Mycobacteria, Microbiology and Virology Laboratory, Careggi Hospital, 50134 Florence, Italy.
Gianna
G
Mazzarelli
Department of Preventive Medicine, Autonoma University of Madrid, 28029 Madrid, Spain.
Martha I
MI
Murcia
Department of Specialized and Experimental Clinical Medicine, Microbiology Division, University of Bologna, 40138 Bologna, Italy.
Anna
A
Nanetti
Regional Reference Center for Mycobacteria, S. Bortolo Hospital, 36100 Vicenza, Italy.
Paola
P
Piccoli
Regional Reference Center for Mycobacteria, S. Bortolo Hospital, 36100 Vicenza, Italy.
Claudio
C
Scarparo
D000368:Aged; D016172:DNA Fingerprinting; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry; D004275:DNA, Ribosomal / Q000737:chemistry; D021903:DNA, Ribosomal Spacer / Q000737:chemistry; D005260:Female; D020459:Genes, rRNA; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D008969:Molecular Sequence Data; D015269:Mycobacterium avium Complex / Q000737:chemistry / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D015270:Mycobacterium avium-intracellulare Infection / Q000382:microbiology; D009171:Mycolic Acids / Q000032:analysis; D009693:Nucleic Acid Hybridization; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D017385:Sequence Homology
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D009171:Mycolic Acids; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S