Detection of a streptomycin-resistant Mycobacterium bovis strain through antitubercular drug susceptibility testing of Tunisian Mycobacterium tuberculosis complex isolates from cattle

Saif Eddine Djemal,Salma Smaoui,Mariam Siala,Feriele Messadi-Akrout,Radhouane Gdoura,Cristina Camperio,Cinzia Marianelli,Federica Armas

doi:10.1186/s12917-018-1623-9

Abstract

BackgroundA rising isolation trend of drug-resistant M. bovis from human clinical cases is documented in the literature. Here we assessed Mycobacterium tuberculosis complex isolates from cattle for drug susceptibility by the gold standard agar proportion method and a simplified resazurin microtitre assay (d-REMA). A total of 38 M. tuberculosis complex strains, including M. bovis (n = 36) and M. caprae (n = 2) isolates, from cattle in Tunisia were tested against isoniazid, rifampin, streptomycin, ethambutol, kanamycin and pyrazinamide.ResultsM. caprae isolates were found to be susceptible to all test drugs. All M. bovis strains were resistant to pyrazinamide, as expected. In addition, one M. bovis isolate showed high-level resistance to streptomycin (MIC > 500.0 μg/ml). Concordant results with the two methods were found. The most common target genes associated with streptomycin resistance, namely the rrs, rpsL and gidB genes, were DNA sequenced. A non-synonymous mutation at codon 43 (K43R) was found in the rpsL gene. To the best of our knowledge, this is the first report describing the isolation of a streptomycin-resistant M. bovis isolate from animal origin.ConclusionsAntitubercular drug susceptibility testing of M. bovis isolates from animals should be performed in settings where bTB is endemic in order to estimate the magnitude of the risk of drug-resistant tuberculosis transmission to humans.

Highlights

A rising isolation trend of drug-resistant M. bovis from human clinical cases is documented in the literature
The situation is profoundly different in unindustrialized countries where the World Health Organization (WHO), in conjunction with Food and Agriculture Organization (FAO) and Organization for Animal Health (OIE), has classified bovine tuberculosis (bTB) as a neglected zoonosis
M. tuberculosis complex strains A total of 38 M. tuberculosis complex strains, including M. bovis (n = 36) and M. caprae (n = 2) previously isolated in Tunisia and molecular typed by spoligotyping and MIRU-VNTR analysis [34], were provided by the University of Sfax (Tunisia)

Summary

Introduction

A rising isolation trend of drug-resistant M. bovis from human clinical cases is documented in the literature. A total of 38 M. tuberculosis complex strains, including M. bovis (n = 36) and M. caprae (n = 2) isolates, from cattle in Tunisia were tested against isoniazid, rifampin, streptomycin, ethambutol, kanamycin and pyrazinamide. The World Organization for Animal Health (OIE) has recognized bovine tuberculosis (bTB) as an important animal disease and zoonosis [1]. BTB causes significant economic losses to farmers due to livestock deaths, reduced productivity and restrictions for trading animals. The main causal agents of bTB are Mycobacterium bovis and, to a lesser extent, Mycobacterium caprae, both members of the Mycobacterium tuberculosis complex. Animal test-and-slaughter schemes have successfully reduced the prevalence of bTB in most industrialized countries. In South Africa, as in other regions in Africa, the lack of bTB control programmes [6] makes communities with high HIV/AIDS infection rates and those living in close contact with infected animals or animal products more vulnerable to zTB [7, 8]

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