Drug Susceptibility of Non-tuberculous Strains of Mycobacterium Isolated from Birds from Poland

The genus Mycobacterium consists of more than 180 species with validly published names (Parte 2014). Most of them are saprophytic species widely distributed in the environment, some of which are pathogenic to humans and animals, including birds (Tan et al. 2016). Tuberculosis caused by the Mycobacterium tuberculosis complex has been found in birds that had contact with humans. Although in most of these cases the source of infection was human, domestic birds not only can be infection vectors, but also can show symptoms typical of the open form of tuberculosis, which results in active mycobacteria release to the environment, sometimes for long time periods (Washko et al. 1998; Montali et al. 2001; Steinmetz et al. 2006; Peters et al. 2007; Ledwoń et al. 2008; Lanteri et al. 2011). In birds, mycobacteriosis caused by non-tuberculous mycobacteria (NTM) is definitely a more common problem than tuberculosis. Clinical manifestations of mycobacteriosis in birds include emaciation, depression and diarrhea along with a marked atrophy of the breast muscle. Tubercular nodules can be seen in the liver, spleen, intestine and bone marrow. Granulomatous lesions without calcification are a prominent feature. The disease is rare in the well-organized poultry sector due to improved farm practices, but occurs in backyard poultry, zoos and aviaries (Portaels et al. 1996; Shitaye et al. 2008; Dhama et al. 2011; Pfeiffer et al. 2017). Mycobacterioses also pose a constantly and increasingly growing threat to human health, especially in people with weakened immunity (Schitaye et al. 2008; Slany et al. 2016; Titmarsh 2017). The mycobacteria most frequently isolated from birds with mycobacteriosis are Mycobacterium avium and Mycobacterium genavense. These bacteria are also a frequent cause of disease in people infected with Human Immunodeficiency Virus (HIV) (Ristola et al. 1999) or those receiving immunosuppressive treatment after transplantation or other systemic diseases (Tortoli 2006; Lastours de et al. 2008; Tan et al. 2016). A study conducted by Garcia-Marcos et al. (2017) showed a correlation between the occurrence of mycobacteriosis in children and their exposure to chickens. But NTM can also cause disease in adult immunocompetent patients (Piersimoni and Scarparo 2006; Santos et al. 2014). Because backyard poultry, pet birds and synanthropic animals live in the immediate vicinity of humans, it is important to study strains with potential pathogenicity for humans, as well as to assess the risk posed by their antibiotic resistance.

Mycobacteriosis was found in 46 birds belonging to 17 bird species (Table I). Gallinaceous birds were diagnosed with only M. avium infections, while pet birds were also diagnosed with M. genavense and M. xenopi infections. One dead canary was found to be infected with both M. genavense and M. xenopi. In wild birds, M. avium predominated, although M. genavense was found in one buzzard. Positive Ziehl-Neelsen staining (AFB +) was observed in 43 cases analysed. The growth of bacterial colonies on the Löwenstein-Jensen and Bactec MGIT 960 media was noticed for 34 samples collected. 31 isolates of M. avium and three isolates of M. xenopi were cultured. Drug susceptibility was tested for 28 M. avium and three M. xenopi strains (Table II and Table III). M. avium strains from common pheasant (Phasianus colchicus) and wood pigeons (Columba palumbus) did not demonstrate any growth on the media used for the assessment of drug resistance. Ten samples were identified as M. genavense, five of which were cultured on the Middlebrook 7H9 medium with Mycobactin J. Two samples were identified as Mycobacterium spp. These mycobacteria were also incapable of growing on the medium for susceptibility testing.

M. avium and M. genavense have been the main causes of mycobacterioses described to date in birds (Tell et al. 2001; Shivaprasad and Palmieri 2012; Pfeffer et al. 2017). Our study confirmed the results published by other authors. Mycobacterioses caused by M. xenopi are very rarely diagnosed in birds (St-Jean et al. 2018). In our investigations, even though only three isolates were obtained, it should not be underestimated. M. xenopi has recently been isolated from water (Slozarek et al. 1993) which is also a source of infection for humans and animals. Birds that were diagnosed with this bacterial infection, however, came from various breeders, so it could not be concluded that they infected themselves with the same water intake.

M. genavense is very difficult to be cultured on the media, and its diagnostics are mainly based on molecular methods (Hoop et al. 1993; Portaels et al. 1996; Ledwoń et al. 2009; Palmieri et al. 2013). Therefore, the drug susceptibility tests used in this study may not be useful for testing of these mycobacteria. Strains of M. avium (Table II) demonstrated 100% resistance to isoniazid, rifampicin and ethambutol, while strains tested on ethionamide showed a good susceptibility to that antibiotic. These results differ from those described in a study by Parvandar et al. (2016) in which all M. avium strains isolated from pigeons for drug susceptibility tests were shown to be resistant to streptomycin, kanamycin, ethionamide and thiophene carboxylic acid hydrazide. Moreover, single isolates were susceptible to isoniazid, rifampicin and ethambutol (Parvandar et al. 2016). In the cases described by Stepień-Pyśniak et al. (2016), M. avium strains isolated from birds demonstrated resistance to isoniazid, rifampicin, ethambutol, ethionamide, capreomycin and ofloxacin, and were susceptible to streptomycin and cycloserine. M. xenopi isolated from birds (Table III) presented resistance similar to that of isolates originating from humans (van Ingen et al. 2010). These isolates were resistant to isoniazid, slightly less resistant to rifampicin and ethambutol, and fully susceptible to other antibiotics. All three species of mycobacteria identified from the cases of mycobacteriosis in birds are able to cause mycobacteriosis in humans, particularly in immunocompromised hosts (Coyle et al. 1992; Ristola et al. 1999; Bluth et al. 2009; Shah et al. 2016; Adzic-Vukicevic et al. 2018). Therefore, mycobacterioses in birds living in a direct proximity to humans should be taken seriously, since they can constitute a potential reservoir of infection with mycobacteria resistant to multiple antimycobacterial drugs.