disinfectant susceptibility of mycobacteria 789
table 3. Mycobactericidal Effects of Oxidizing High-Level Disinfectants and a Quaternary Ammonium Compound Against GTA- Susceptible and GTA-Resistant Mycobacterium Isolates in Suspension Testsa
Mmas CIP
Product Tested
108297 (GTAS)
Reliance DG, 50°C 0 min 2 min 6 min
S40, 50°C 0 min 2 min 6 min
Resert XL, 25°C 0 min 4 min 8 min
CTAB, 25°C 0 min
8.39 0 0
8.63 0 0
8.63 0 0
8.39
Sterile Water, 50°C 0 min 2 min 6 min
nd nd nd
Mch Mmas
CRM-0270 (GTAS)
8.42 0 0
8.73 0 0
8.73 8.42
60 min 5.97±0.01 6.15±0.02 1,440 min 6.27
nd nd
Mmas
CRM-0019 (GTAR)
9.00 0 0
9.11 0 0
3.12±0.18 3.51±0.22 0
9.11 0
9.00 nd
8.80
8.27±0.11 8.24±0.13
ATCC 35752 (GTAS)
8.79 0 0
8.58 0 0
8.58 0 0
8.79
nd nd nd
Mch 9917 (GTAR)
7.54 0 0
7.75 0 0
7.89 0 0
7.89 nd
Harefield (GTAR)
Mch
8.13 0 0
7.92 0 0
7.92 8.13 8.20 Mch
Epping (GTAR)
7.05 0 0
7.91 0 0
4.17±0.11 0 0
8.40 0
8.40 8.33±0.02 7.61±0.03 7.97±0.04 nd nd
nd 7.96±0.02 nd nd 8.00±0.12 nd
M. bovis BCG
(Pasteur) (GTAS)
6.92 0 0
6.92 0 0
nd nd nd
nd nd
5.55±0.12 7.16±0.05 5.05±0.90 6.46±0.16 7.43±0.01 6.35±0.03 nd nd
nd nd nd
M. avium 104
(GTAS)
9.15 0 0
9.15 0 0
9.15 0 0
nd nd nd
nd nd nd
M. terrae ATCC 15755 (GTAS)
7.92 0 0
7.92 0 0
nd nd nd
nd nd nd
nd nd nd
NOTE. GTA, glutaraldehyde; OPA, ortho-phthalaldehyde; CFU, colony-forming units; GTAR, GTA-resistant; GTAS, GTA-susceptible; CTAB,
cetyl trimethylammonium bromide; nd, not determined. aControl suspension tests using the GTA-susceptible isolate, M. massiliense CIP 108297, confirmed the neutralizing efficacy of the neutralizing broth with each disinfectant product. The detection limit of the suspension tests is 1 CFU/mL.
detectable CFU counts at the recommended time point of 5 minutes for all M. chelonae strains except M. chelonae Harefield. However, this strain was reduced to no detectable CFU by the 10-minute time point at 25°C and to no detectable CFU by the recommended 12-minute time point at 20°C (Table 1). When 0.3% OPA was tested using the carrier-disk method, all test strains were reduced to no viable CFU within 5 minutes (Table 2).
Oxidizing Agents and Other Disinfectant Products
For the 2 disinfectants used in automated endoscope washers at 50°C, S40 and Reliance DG (2 peracetic acid-based pro- ducts), CFU counts for all tested strains were reduced below detection levels within 2 minutes of exposure under suspen- sion testing, and by the 6-minute time point under carrier-disk testing (Tables 2 and 3). To assess the impact of the 50°C temperature on the viability of mycobacteria, 2 GTA-resistant strains, M. abscessus subsp. massiliense CRM-0019 and M. chelonae Harefield, were exposed to sterile water at 50°C for up to 6 minutes; in both cases, no significant loss of viability was detected (Table 3). For Resert XL (a hydrogen-peroxide– based product), viable bacterial counts were reduced>7-log10 within 8 minutes under both the suspension and carrier-disk
methods (Tables 2 and 3). Finally, suspension testing of a quaternary ammonium compound found in many disin- fectants and antiseptics (10% CTAB) demonstrated, as expected,22 very modest bactericidal activity against rapidly growing mycobacteria, with <4-log10 reduction in CFU for all tested strains after 24 hours (Table 3).
discussion
Whereas OPA is now the leading high-level disinfectant in the United States, activated alkaline GTA at ambient temperature remains one of the most widely used high-level disinfectants worldwide for its broad-spectrum microbicidal activity, rela- tively low cost, ease of use, and nondamaging effects on medical equipment and reprocessors. The emergence of globally circulating virulent clones of M. abscessus complex species25 has caused great concern, coupled with reports of rapidly growing mycobacteria presenting resistance to aldehyde-based products, including the recent largest outbreak ever reported of M. abscessus complex infections in Brazil.3,4,6 In addition, some of the mechanisms of resistance to aldehydes evolved by NTM may confer cross-resistance to other disin- fectants and antibiotics.17,19 Taken together, these factors led us to systematically investigate the susceptibility profile of a
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