Abstract
Culture is considered the gold standard for definitive diagnosis of mycobacterial infections. However, consensus about the most suitable culture procedure for isolation of nontuberculous mycobacteria is lacking. The study compared the recoveries of mycobacteria after decontamination of spiked and fresh avian feces with 4% sodium hydroxide (NaOH), 12% sulfuric acid (H2SO4), or 1% cetylperidinium chloride (CPC), with and without mixture of three antibiotics, namely vancomycin (VAN, 100 μg/ml), nalidixic acid (NAL, 100 μg/ml), and amphotericin B (AMB, 100 μg/ml). The antibiotic mixture was referred to as VNA. Decontamination procedures were evaluated using two (n = 2) avian fecal samples spiked with 106, 104, and 102 CFU/ml of Mycobacterium avium subsp. avium (ATCC 15769) and fresh avian feces (n = 42). M. avium subsp. avium was detected on the culture media from spiked samples (106 and 104 CFU/ml) decontaminated with NaOH, NaOH-VNA, H2SO4, and H2SO4 -VNA for 2−6 weeks. These bacteria were detected in 2–4 weeks when using CPC and CPC-VNA. M. avium subsp. avium cannot be isolated on culture media from spiked samples (102 CFU/ml) decontaminated with any decontaminating agent. Two mycobacterial isolates, namely, Mycobacterium terrae and M. engbaekii, were isolated from field samples decontaminated with NaOH and CPC-VNA. With regard to the contamination rate, the use of CPC-VNA showed lower contamination rates (5.5% and 19.0%) from spiked and field samples than those of the other methods (NaOH: 22.2% and 59.5%, NaOH-VNA: 16.7% and 21.4%, H2SO4: 11.1% and 40.5%, H2SO4-VNA: 5.5% and 21.4%, and CPC: 66.7% and 50%). In conclusion, the decontamination of fecal samples following a two-step procedure with 1% CPC and VNA can ensure high recovery rate of many mycobacteria with the lowest contamination in cultures.
Highlights
Mycobacterium avium complex (MAC) includes two closely related species, namely, M. avium and M. intracellulare, which are saprophytes and opportunistic pathogens to human and animals [1]
Given that the decontamination method of fecal samples is one of the main factors affecting the isolation of MAC from culture media, the present study aimed to evaluate three decontaminating agents, namely, 4% NaOH, 12% H2SO4, and 1% cetylperidinium chloride (CPC), with the presence or absence of VAN, nalidixic acid (NAL), and amphotericin B (AMB) (VNA) antibiotics to recover MAC on Lowenstein–Jensen (L–J) culture medium from spiked fecal samples and fresh avian feces
M. avium subsp. avium was recovered significantly higher with CPC-VNA than those with NaOH-VNA and 1% CPC (27.8%; χ2 test, p = 0.01) (Table 1)
Summary
Mycobacterium avium complex (MAC) includes two closely related species, namely, M. avium and M. intracellulare, which are saprophytes and opportunistic pathogens to human and animals [1]. MAC is an emerging pathogen with considerable public health importance [2,3] because it can cause severe disseminated diseases in patients immunocompromised due to AIDS, cystic fibrosis, leukemia [4,5,6], and pulmonary disease in immunocompetent people [4,7,8]. M. intracellulare causes 40% respiratory disease in immunocompetent patients with chronic lung disease [4]. Birds may cause environmental contamination with MAC through fecal droppings, thereby increasing public health concern [1]. Immunocompromised patients may contract the pathogen during handling of infected birds or consumption of meat from infected birds [11,12]
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