Hull, N. M. | Search bioRxiv

bioRxiv2025

Mycobacterium intracellulare ABSURDO is a novel clinical isolate with three colony morphotypes that vary in pathogenicity and sequence at the PKS and MtrA loci

Mycobacterium intracellulare is a nontuberculous mycobacteria (NTM) species which can cause serious and sometimes fatal disease in immunocompromised individuals. Other NTM species, including M. avium and M. abscessus, commonly exhibit two colony morphotypes (smooth and rough) which vary in appearance and liquid growth properties. Here we characterize a novel clinical isolate of M. intracellulare which exhibits three (not two) colony morphotypes which differ in appearance, liquid growth properties, acid-fastness and in vivo survival following infection of mice via an inhalational exposure model. The genome of this isolate, which we have termed ABSURDO, as well as the genome of each morphotype components, aligns with that of M. intracellulare yet contains [~]16% more protein coding sequences than the M. intracellulare type strain ATCC 13590T. Variation analysis of each morphotype genome revealed that across the three morphotypes there were only two mutations which had a high likelihood of causing a phenotype due to a genetic change: one in the gene encoding modular polyketide synthase (PKS), and another in the two component system response regulator MtrA. Neither of these genes have been previously implicated in the morphotype shifting of an NTM. In summary, M. intracellulare ABSURDO is a novel pathogenic isolate with a genome that aligns with (but is nevertheless larger than) the M. intracellulare type strain and comprises three morphotype components which differ in two genes that have not been implicated in NTM appearance, acid-fastness, in vitro and in vivo growth.

microbiology↗

bioRxiv2021

Viability of MS2 and Phi6 Bacteriophages on Carpet and Dust

Respiratory viral illnesses are commonly spread in the indoor environment through multiple transmission routes, including droplets, aerosols, and direct/indirect contact. Indoors, resuspension of dust from flooring is a major source of human exposure. However, it is critical to determine viral persistence on dust and flooring to better characterize human exposure. The goal of this work is to determine viral viability on two carpet types (cut and looped) and house dust over time and after four different cleaning methods. MS2 and Phi6 bacteriophages were used to represent non-enveloped and enveloped viruses, respectively. These viral surrogates were placed in an artificial saliva solution and nebulized onto carpet or dust. Viability was measured at various time points (0, 1, 2, 3, 4, 24, and 48 hours) and after cleaning (vacuuming, hot water extraction with stain remover, steam, and a disinfection spray). Viability decay was modeled as first-order. MS2 bacteriophages showed slower viability decay rates in dust (-0.11 hr-1), cut carpet (-0.20 hr-1), and looped carpet (-0.09 hr-1) compared to Phi6 (-3.36 hr-1, -1.57 hr-1, and - 0.20 hr-1 respectively). The difference between phages was statistically significant in dust and cut carpet (p<0.05). Viral RNA demonstrated minimal degradation that in most cases was not statistically different from zero over the 48 hours measured (p>0.05). Viable viral concentrations were reduced to below the detection limit for steam and disinfection for both MS2 and Phi6 (p<0.05), while vacuuming and hot water extraction with stain remover showed no significant changes in concentration from uncleaned carpet (p>0.05). This study used viral surrogates and did not model risk of viral transmission via dust. Overall, these results demonstrate that MS2 and Phi6 bacteriophages can remain viable in carpet and dust for several hours to days, and cleaning techniques with heat and disinfectants may be more effective than standard vacuuming for viral removal. Future work should model risk from exposure via dust and flooring for various viruses such as influenza, SARS-CoV-2, and RSV. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=99 SRC="FIGDIR/small/444479v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@1cc0ad9org.highwire.dtl.DTLVardef@dc440corg.highwire.dtl.DTLVardef@f787dcorg.highwire.dtl.DTLVardef@f8bda3_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗