Comparative analysis of the genomes of clinical isolates of Mycobacterium avium subsp. hominissuis regarding virulence-related genes

Paratuberculosis is a chronic disease of ruminants caused by Mycobacterium avium subsp. Paratuberculosis (MAP). Since isolation of MAP type I (S) is rarely reported in Italy, our research was aimed at isolating, by an inexpensive liquid culture manual method, this type of MAP isolates. At first, we used an ELISA to point out to serologically positive samples from five flocks. Secondly, we used a fecal direct IS900-qPCR on the ELISA positive samples, in order to detect shedder animals. Feces from IS900-qPCR positive samples were inoculated in solid and liquid culture media. IS900-qPCR was further used to test the growth of MAP isolates in liquid medium, which were further confirmed by f57-qPCR and submitted to typing by specific PCR in order to identify the MAP type. Twenty-eight samples (24 fecal and four tissutal samples) were processed by culture methods, resulting in the isolation of six type I MAP field isolates. Notably, no isolates were recovered by solid media, underlining the utility of this liquid method. Few data about this type of MAP are currently available in Italy, and further analyses should be carried out in order to study the origin and epidemiology of type I strains circulating in Italy.

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Association between 16S rRNA gene mutations and susceptibility to amikacin in Mycobacterium avium Complex and Mycobacterium abscessus clinical isolates

Scientific Reports ◽

10.1038/s41598-021-85721-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Su-Young Kim ◽

Dae Hun Kim ◽

Seong Mi Moon ◽

Ju Yeun Song ◽

Hee Jae Huh ◽

...

Keyword(s):

16S Rrna ◽

16S Rrna Gene ◽

Mycobacterium Avium ◽

Inhibitory Concentration ◽

Gene Mutations ◽

Mycobacterium Abscessus ◽

Clinical Isolates ◽

Rrna Gene ◽

High Level ◽

Culture Conversion

AbstractWe evaluated the association between 16S rRNA gene (rrs) mutations and susceptibility in clinical isolates of amikacin-resistant nontuberculous mycobacteria (NTM) in NTM-pulmonary disease (PD) patients. Susceptibility was retested for 134 amikacin-resistant isolates (minimum inhibitory concentration [MIC] ≥ 64 µg/ml) from 86 patients. Amikacin resistance was reconfirmed in 102 NTM isolates from 62 patients with either Mycobacterium avium complex-PD (MAC-PD) (n = 54) or M. abscessus-PD (n = 8). MICs and rrs mutations were evaluated for 318 single colonies from these isolates. For the 54 MAC-PD patients, rrs mutations were present in 34 isolates (63%), comprising all 31 isolates with amikacin MICs ≥ 128 µg/ml, but only three of 23 isolates with an MIC = 64 µg/ml. For the eight M. abscessus-PD patients, all amikacin-resistant (MIC ≥ 64 µg/ml) isolates had rrs mutations. In amikacin-resistant isolates, the A1408G mutation (n = 29) was most common. Two novel mutations, C1496T and T1498A, were also identified. The culture conversion rate did not differ by amikacin MIC. Overall, all high-level and 13% (3/23) of low-level amikacin-resistant MAC isolates had rrs mutations whereas mutations were present in all amikacin-resistant M. abscessus isolates. These findings are valuable for managing MAC- and M. abscessus-PD and suggest the importance of phenotypic and genotypic susceptibility testing.

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