Molecular Basis of Rifampin and Isoniazid Resistance in Mycobacterium bovis Strains Isolated in Sardinia, Italy

Abstract

Fourteen of 22 (68%) Mycobacterium bovis strains isolated from cattle in Sardinia were found to be resistant to rifampin and isoniazid. Analysis of the rpoB and the katG, oxyR-ahpC, and inhA gene regions of these strains was performed in order to investigate the molecular basis of rifampin and isoniazid resistance, respectively. The most frequent mutation, encountered in 6 of 10 strains (60%), was in the rpoB gene; it occurred, at codon position 521 and resulted in leucine changed to proline. This suggests that codon 521 may be important for the development of rifampin resistance in M. bovis. Resistance to isoniazid is associated in Mycobacterium tuberculosis with a variety of mutations affecting one or more genes. Our results confirm the difficulty of interpreting the sequence variations observed in clinical strains of M. bovis. M. bovis strains isolated from the same geographic area showed similar mutations within the genes responsible for rifampin and isoniazid resistance. Our results represent the first study to elucidate the molecular genetic basis of drug resistance in M. bovis isolated from cattle.Mycobacterium bovis is the major cause of tuberculosis in domestic animals and can produce human disease which is indistinguishable from that caused by Mycobacterium tuberculosis (6,8). In many industrialized countries, M. bovis has been eradicated from cattle or reduced to very low levels through the implementation of control programs based on test-andslaughter principles. Bovine tuberculosis continues to be a major problem in countries which cannot afford such programs or where these programs have been only partially effective due to wildlife reservoirs of infection (6). These include the badger in the United Kingdom and the brush-tailed opossum in New Zealand (4, 5). In Sardinia, as a result of an eradication program, bovine tuberculosis was considered eradicated in 1964. Recently various M. bovis strains have been isolated from different herds (17); one of these strains was isolated from an animal imported from Cremona (northern Italy) in 1996. Moreover various wild animals present in Sardinia, such as the mouflon and the wild boar (Sus scrofa), could be reservoirs for M. bovis (2).The molecular basis of multidrug-resistant (MDR) tuberculosis has been well documented (3,13,14). The most common mechanisms of resistance to the primary antimycobacterial agents such as rifampin, isoniazid, and streptomycin in M. tuberculosis are mutations in the target genes. Consequently, virtually all isolates resistant to rifampin and related rifamycins carry mutations affecting a 27-amino-acid region of the coding sequence of the RNA polymerase beta subunit (15). The majority of isoniazid-resistant isolates carry mutations in the katG and inhA genes (13). Limited data are available regarding the genetic assessment of drug-resistant M. bovis strains (1), in particular M. bovis strains isolated from animals. Bovine tuberculosis remains a major infectious disease among cattle worldwide, making control of outbreaks and preventio...

Genotyping and rifampicin and isoniazid resistance in Mycobacterium bovis strains isolated from the lymph nodes of slaughtered cattle

“…These data contrast with those reported in studies on M. bovis strains obtained from Michigan's wild whitetailed deer (considered as the primary tuberculosis reservoirs for domestic cattle in Michigan), which did not find drug-resistance in the microorganisms using the proportions method and the Bac-tec™ system [17]. In contrast, in Italy, a study reported 22.7% of M. bovis as multidrug-resistant, as well as 22.7% RMP-resistant and 18.9% INH-resistant in strains from cattle herds [16].…”

“…Therefore, the complete identification of MTBC isolates at the species level is required for the appropriate treatment of the patient and for appropriate public health and epidemiological measures to be taken [15]. Furthermore, all over the world, few studies have investigated the resistance to isoniazid (INH) and rifampicin (RMP) in M. bovis strains from cattle, wildlife reservoirs and human cases of tuberculosis [4,16,17].…”

Use of the hupB Gene Encoding a Histone-Like Protein of Mycobacterium tuberculosis as a Target for Detection and Differentiation of M. tuberculosis and M. bovis

“…Deviations from standard patterns in all of the above tests have been reported, making it virtually impossible to differentiate between M. bovis, M. tuberculosis, and M. africanum (12,34,38,48). The high degree of variability in the phenotypic characteristics has made it important to develop reliable techniques to distinguish between members of the Mycobacterium tuberculosis and M. bovis (MTB) complex (22,41). Techniques based on the amplification of mycobacterial DNA sequences by PCR have been introduced in many laboratories as a promising alternative rapid, sensitive, and specific detection of M. tuberculosis in clinical specimens (2,7,14).…”

Prevalence of Multidrug Resistance Mycobacterium Bovis in Human: A Systematic Review and Meta-Analysis

“…Multidrug resistant Mycobacterium bovis was reported in Europe in Spain, France, Scotland, Netherland, and Italy [21][22][23][24][25]. In North America, the resistant bacteria of M.bovis had been isolated from patients in USA , Canada and Mexico [26], [27], [28].…”