Non-tuberculousMycobacteriaisolated from lymph nodes and faecal samples of healthy slaughtered cattle and the abattoir environment

Mycobacterium kansasii Infection in a Farmed White-Tailed Deer (Odocoileus virginianus) in Florida, USA

A 7-year-old farmed white-tailed deer doe was transported to a Levy County, Florida property and began to decline in health, exhibiting weight loss and pelvic limb weakness. The doe prematurely delivered live twin fawns, both of which later died. The doe was treated with corticosteroids, antibiotics, gastric cytoprotectants, and B vitamins but showed no improvement. The doe was euthanized, and a post mortem examination was performed under the University of Florida's Cervidae Health Research Initiative. We collected lung tissue after the animal was euthanized and performed histological evaluation, using H&E and Ziehl-Neelsen (ZN) staining, and molecular evaluation, using conventional PCR, followed by Sanger sequencing. The microscopic observations of the H&E-stained lung showed multifocal granuloma, while the ZN-stained tissue revealed low numbers of beaded, magenta-staining rod bacteria inside the granuloma formation. Molecular analysis identified the presence of Mycobacterium kansasii. This isolation of a non-tuberculous Mycobacterium in a white-tailed deer emphasizes the importance of specific pathogen identification in cases of tuberculosis-like disease in farmed and free-ranging cervids. We report the first case of M. kansasii infection in a farmed white-tailed deer (Odocoileus virginianus) in Florida. Although M. kansasii cases are sporadic in white-tailed deer, it is important to maintain farm biosecurity and prevent farmed cervids from contacting wildlife to prevent disease transmission.

Non-tuberculous mycobacteria: occurrence in skin test cattle reactors from official tuberculosis-free herds

Non-tuberculous mycobacteria (NTM) are considered a relevant cause of non-specific reactions to the most widely applied bovine tuberculosis (bTB) test, the intradermal tuberculin test. In order to establish which NTM species might act as a potential source of such diagnostic interference, a collection of 373 isolates obtained from skin test positive cows from 359 officially tuberculosis-free (OTF) herds, culled in the framework of the bTB eradication campaign in Spain, were identified at the species level through PCR and Sanger sequencing of the 16S rDNA, hsp65 and rpoB genes. Of the 308 isolates for which a reliable identification was achieved, 32 different mycobacterial species were identified, with certain species being most represented: among M. avium complex members (n = 142, 46.1%), M. avium subsp. hominissuis (98; 69.0%) was the most abundant followed by M. avium subsp. avium (33, 23.2%), and M. intracellulare (7, 4.9%). Among non-MAC members (n = 166, 53.9%), M. nonchromogenicum (85; 27.6%) and M. bourgelatii (11; 5.6%) were the predominant species. In addition, mixed results were obtained in 53 isolates presenting up to 30 different genotypes, which could be indicative of new mycobacterial species. Our results represent a first step toward characterizing the diversity of NTM species that could interfere with official diagnostic tests for bTB eradication in Spain.

Identification of New Mycobacterium bovis antigens and development of a multiplexed serological bead-immunoassay for the diagnosis of bovine tuberculosis in cattle

Serological assays for bovine tuberculosis diagnosis require the use of multiple Mycobacterium bovis specific antigens to ensure the detection of infected animals. In the present study, identification and selection process of antigens, based on data from published proteomic studies and involving the use of bioinformatics tools and an immuno-screening step, was firstly performed for identifying novel antigens that elicit an antibody response in M. bovis infection. Based on this approach, a panel of 10 M. bovis antigens [with known relevance (MPB70, MPB83, MPB70/83, and ESAT6/CFP10) and novel (Mb1961c, Mb1301c, Mb3871, Mb1403, Mb0592, and PE25/PPE41)] were constructed and thenused to develop a new multiplexed serological assay based on Luminex technology. The performance of the Luminex-bTB immunoassay was evaluated using sera from cattle with known tuberculosis status. Among the proteins whose ability to detect bovine tuberculosis was evaluated for the first time, PE25/PPE41 and Mb1403, but not Mb3871, showed good detection capacity. Following multiple antigen combination, the final Luminex-bTB immunoassay included seven antigens (MPB70, MPB83, MPB70/83, ESAT6/CFP10, PE25/PPE41, Mb1403, and Mb0592) and showed better global performance than the immunoassay using the four usual antigens (MPB70, MPB70/83, MPB83 and ESAT6/CFP10). The specificity and sensitivity values were, respectively, of 97.6% and 42.8% when the cut-off of two-positive antigens was used to classify samples as positive. With the use of the more-restrictive criterion of three-positive antigens, the specificity increased to 99.2% but the sensitivity decreased to 23.9%. The analysis of antigen profiles generated with the Luminex-bTB immunoassay showed that mainly serodominant proteins were recognized in samples from infected cattle. The detection of Mb1961c and Mb1301c appeared to be associated with presumed false-positive results. Moreover, sera from cattle originating from bTB-outbreaks but having inconclusive or negative skin test results were identified as positive by the Luminex-bTB immunoassay and showed an antigen pattern associated with M. bovis infection. The Luminex-bTB immunoassay including seven antigens may be useful as adjunct test for the detection of M. bovis-infected herds, and different cut-offs could be applied according to the bovine tuberculosis epidemiological context.

Beyond Tuberculosis: Diversity and implications of non-tuberculous mycobacteria at the wildlife-livestock interface

Non-tuberculous mycobacteria (NTM) circulate between the environment, animals and humans entailing a double concern: their ability to interfere with tuberculosis diagnosis and their potential to cause infections in their hosts. However, published records on NTM infections in animals are still scarce. The aims of the present study were to describe the diversity of NTM circulating among wild and domestic species from Spain, and to analyse their implications as potential pathogenic microorganisms or as sources of interferences in the diagnosis of bovine tuberculosis. Overall, 293 NTM isolates of 277 animals were obtained from tissue samples collected between 2012 and 2019, and analysed through a multigene approach for mycobacteria identification. Thirty-one species were identified, being M. avium subsp. avium (Maa) and M. avium subsp. hominissuis (Mah), but also M. bouchedurhonense, M. nonchromogenicum and M. lentiflavum, the most abundant ones. Maa and M. lentiflavum were isolated in several animals showing tuberculosis-like lesions. Maa, Mah and M. nonchromogenicum were recovered from many cattle that had reacted to the tuberculin skin test (TST). Other NTM were also associated to these phenomena. These four mycobacterial species were geographically associated between wild boar and other hosts. The findings of the present study suggest that a high diversity of NTM circulates among wildlife and livestock. Wild boar and M. avium seem to play a relevant role in this epidemiological scenario. This article is protected by copyright. All rights reserved.

Infection of a Free-Living Wild Boar (Sus scrofa) with a Bacterium from the Mycobacterium kansasii Complex

Simple Summary

Mycobacteriosis is a collective term for diseases caused by nontuberculous mycobacteria. Wild animals are a frequent source of mycobacteria infection in farm animals and humans; therefore, it is important to monitor the presence of these pathogens in free-living mammals. We isolated bacterium belonging to Mycobacterium kansasii complex from a submandibular lymph node obtained from a wild boar. This mycobacterium is a common cause of severe human lung diseases and is rarely responsible for animal diseases; therefore, its presence in the wild animal population is of great concern. The animal was apparently healthy, and we did not find any internal organ lesions despite the abundant growth of tissue-isolated bacteria on media. Thanks to our research, the specificity of wild boar mycobacteriosis caused by MKC will be better known.

Abstract

The most numerous group of bacteria in the genus Mycobacterium is the nontuberculous mycobacteria. Currently, over 200 species of bacteria have been classified as belonging to this group, of which approximately 30 are pathogenic to humans and animals. Mycobacterium kansasii complex numbers among these pathogenic species. The submandibular lymph nodes of a wild boar shot by a hunter were examined in order to confirm or exclude infection with bacteria of the genus Mycobacterium. In culture, a bacterial isolate was obtained after 12 days of incubation on Petragnani and Stonebrink media. A multiplex PCR clearly indicated that the isolate was a nontuberculous mycobacterium. The results of species identification attempts via both molecular biology methods and mass spectrometry confirmed that the isolated strain belonged to MKC. The described case of a wild boar infection with MKC is the first documented case in Poland and only the second in Europe, and in confirming the presence of this pathogen among free-living animals, this report implies that MKC is of great concern. Our research elucidates some specifics of wild boar mycobacteriosis and may be used to instill awareness in the public of the dangers of dressing hunt prey or consuming its meat in ignorance of safe procedures, which can contribute to the transmission of the pathogen to humans.

MALDI-TOF Mass Spectrometry as a Rapid Screening Alternative for Non-tuberculous Mycobacterial Species Identification in the Veterinary Laboratory

Non-tuberculous mycobacteria (NTM) are difficult to identify by biochemical and genetic methods due to their microbiological properties and complex taxonomy. The development of more efficient and rapid methods for species identification in the veterinary microbiological laboratory is, therefore, of great importance. Although MALDI-TOF Mass Spectrometry (MS) has become a promising tool for the identification of NTM species in human clinical practise, information regarding its performance on veterinary isolates is scarce. This study assesses the capacity of MALDI-TOF MS to identify NTM isolates (n = 75) obtained from different animal species. MALDI-TOF MS identified 76.0% (n = 57) and 4% (n = 3) of the isolates with high and low confidence, respectively, in agreement with the identification achieved by Sanger sequencing of housekeeping genes (16S rRNA, hsp65, and rpoB). Thirteen isolates (17.3%) were identified by Sanger sequencing to the complex level, indicating that these may belong to uncharacterised species. MALDI-TOF MS approximated low confidence identifications toward closely related mycobacterial groups, such as the M. avium or M. terrae complexes. Two isolates were misidentified due to a high similarity between species or due to the lack of spectra in the database. Our results suggest that MALDI-TOF MS can be used as an effective alternative for rapid screening of mycobacterial isolates in the veterinary laboratory and potentially for the detection of new NTM species. In turn, Sanger sequencing could be implemented as an additional method to improve identifications in species for which MALDI-TOF MS identification is limited or for further characterisation of NTM species.

Evaluation of Three Commercial Interferon-γ Assays in a Bovine Tuberculosis Free Population

The interferon-γ assay has been used worldwide as an ancillary test for the diagnosis of bovine tuberculosis (bTB). This study aimed to describe, based on the bTB-free status in Switzerland, the difference of applying a more stringent cutoff point of 0.05 compared with 0.1 for bTB surveillance. Moreover, the effect of time between blood collection and stimulation, culture results, optical density values, and the influence of testing different breeds were evaluated. Blood samples from a total of 118 healthy cows older than 6 months were tested with three commercial interferon-gamma assays. To confirm the bTB-free status of the tested animals and to investigate potential cross-reactions with nontuberculous mycobacteria, pulmonary and abdominal lymph nodes in addition to ileal mucosa from each cattle were used for the detection of viable Mycobacteria spp. by specific culture. Significant differences regarding the proportion of false-positive results between the two Bovigam tests and between Bovigam 2G and ID Screen were found. Samples analyzed with Bovigam 2G were 2.5 [95% confidence interval (CI) 1.6–3.9] times more likely to yield a false-positive test result than samples analyzed with Bovigam TB. Similarly, the odds ratio (OR) for testing samples false-positive with ID Screen compared with Bovigam TB was 1.9 (95% CI 1.21–2.9). The OR for testing false-positive with ID Screen compared with Bovigam 2G was less to equally likely with an OR of 0.75 (95% CI 0.5–1.1). When using a cutoff of 0.05 instead of 0.1, the OR for a false-positive test result was 2.2 (95% CI 1.6–3.1). Samples tested after 6 h compared with a delayed stimulation time of 22–24 h were more likely to yield a false-positive test result with an OR of 3.9 (95% CI 2.7–5.6). In conclusion, applying a more stringent cutoff of 0.05 with the Bovigam 2G kit generates a questionable high number of false-positive results of one of three tested animals. Furthermore, specific breeds might show an increased risk to result false-positive in the Bovigam 2G and the ID Screen assays.

Unusual Presentation of Feline Leprosy Caused by Mycobacterium lepraemurium in the Alpine Region

A 9-year-old cat was referred with multiple, raised, ulcerative and non-ulcerative nodules in the periocular area, sclera and ear-base region, and on the ventral aspect of the tongue. In addition, a progressive ulcerative skin nodule on the tail was observed. Fine-needle aspirations of multiple nodules from the eyelid and sclera revealed the presence of histiocytes with numerous acid-fast intracellular bacilli. The replication of slowly growing mycobacteria in liquid media was detected from biopsied nodules after three months of incubation. The molecular characterization of the isolate identified Mycobacterium (M.) lepraemurium as the cause of the infection. The cat was treated with a combination of surgical excision and a four-week course of antimicrobial therapy including rifampicin combined with clarithromycin. This is an unusual manifestation of feline leprosy and the first molecularly confirmed M. lepraemurium infection in a cat with ocular involvement in Europe. The successful combination of a surgical and antimycobacterial treatment regimen is reported.

ISOLATION AND ANTIMICROBIAL SUSCEPTIBILITIES OF NONTUBERCULOUS MYCOBACTERIA FROM WILDLIFE IN JAPAN

Nontuberculous mycobacteria (NTM) are opportunistic pathogens of humans and animals and are transmitted among the environment, wildlife, livestock, and humans. The aim of this study was to investigate the rate of isolation and antimicrobial susceptibility of NTM in wildlife. In total, 178 samples of feces (n=131) and tissues (n=47) were collected from 11 wildlife species in Gifu Prefecture and Mie Prefecture, Japan, between June 2016 and October 2018. We isolated NTM from 15.3% (20/ 131) of fecal samples using Ogawa medium, and isolates were identified by sequencing the rpoB and hsp65 genes. The rpoB sequences were compared with those from other strains of human and environmental origin. The NTM isolates were obtained from sika deer (Cervus nippon), wild boar (Sus scrofa), Japanese monkey (Macaca fuscata), raccoon dog (Nyctereutes procyonoides), masked palm civet (Paguma larvata), and Japanese weasel (Mustela itatsi) and were classified as rapidly growing mycobacteria (RGM) and slowly growing mycobacteria (SGM). The 12 RGM identified were Mycolicibacterium peregrinum (n=5), Mycolicibacterium fortuitum (n=3), Mycolicibacterium septicum (n=3), and Mycolicibacterium thermoresistibile (n=1), and the eight SGM were Mycobacterium paraense (n=4), Mycolicibacter arupensis (n=2), Mycolicibacter virginiensis (n=1), and Mycobacterium nebraskense (n=1). The NTM from wildlife showed ≥99% similarity with strains from different sources including humans. The RGM were susceptible to the antimicrobial agents tested except for M. fortuitum, which was resistant to azithromycin and clarithromycin. The SGM showed multiple drug resistance qualities but were susceptible to amikacin, clarithromycin, and rifabutin. These results indicate that wildlife may be reservoir hosts of NTM in Japan. The presence of antimicrobial-resistant NTM in wildlife suggests that the trends of NTM antimicrobial susceptibility in wildlife should be monitored.

Role of abattoir monitoring in determining the prevalence of bovine tuberculosis: A systematic review and meta-analysis

Bovine tuberculosis (bTB) is one of the major zoonotic concerns of the world, as milk and meat from cattle are major products for human consumption. Bovine tuberculosis not only affects the health of cattle and poses an imminent zoonotic threat, but also causes significant economic loss in both developed and developing countries. This systematic review reports the prevalence of Mycobacterium tuberculosis complex (MTBC) organisms in slaughtered cattle showing tuberculosis-like lesion (TBL) with available literature worldwide. Appropriate keywords were used to search various databases to collect articles pertaining to slaughterhouse studies. Bovine TB prevalence, based on the prevalence of MTBC organisms in slaughtered cattle showing TBL by culture, microscopy, PCR and spoligotyping, was assessed in each study using a random-effects model and standardized mean with 95% confidence interval (CI). Heterogeneity was assessed by the I² statistic. Publication bias was evaluated using funnel plots. Out of 72 hits, 37 studies were selected based on title and abstract. Ten articles were excluded due to lack of desired data, and 27 studies were included in the final analysis. From the selected articles, it was found that 426 [95% CI: 302-560] per 1,000 slaughtered cattle with TBL were positive for the presence of MTBC organisms. The sensitivity analysis showed that no individual study alone influenced the estimation of pooled prevalence. The prevalence of MTBC organisms in slaughtered cattle showing TBL by culture, microscopy, PCR and spoligotyping was 474[95% CI: 342-610], 385 [95% CI: 269-515], 218 [95% CI: 132-338], 326 [95% CI: 229-442], respectively, per 1,000 slaughtered cattle. Most of the slaughtered cattle were from the same locality as the slaughterhouse. The results obtained in this study suggest that abattoir monitoring can give an estimate of the prevalence of bTB in that locality. This study also emphasizes the need to test cattle and animal handlers who were in contact with bTB-positive cattle.

Direct PCR on Tissue Samples To Detect Mycobacterium tuberculosis Complex: an Alternative to the Bacteriological Culture

Bovine tuberculosis (bTB) is an ongoing issue in several countries within the European Union. Microbiological culture is the official confirmation technique for the presence of Mycobacterium tuberculosis complex (MTBC) members in bovine tissues, but several methodological issues, such as moderate sensitivity and long incubation times, require the development of more sensitive and rapid techniques. This study evaluates the analytical and diagnostic performance, comparative to culture, of a real-time PCR targeting the MTBC-specific IS6110 transposon using a panel of bovine tissue samples sourced from the Spanish bTB eradication campaign. Robustness and repeatability were evaluated in an interlaboratory trial between European Union National Reference Laboratories. The limit of detection with 95% confidence was established at 65 fg/reaction of purified genomic equivalents. Diagnostic sensitivity (Se) and specificity (Sp) were, respectively, 96.45% and 93.66%, and the overall agreement (κ) was 0.88. Cross-reactivity was detected against two mycobacterial isolates identified as Mycobacterium marinum and "Mycobacterium avium subsp. hominissuis," and whole-genome sequencing (WGS) analysis of the latter isolate revealed an IS6110-like sequence with 83% identity. An identical IS-like element was found in other Mycobacterium avium complex species in the NCBI nucleotide and WGS databases. Despite this finding, this methodology is considered a valuable alternative to culture, and the strategy of use should be defined depending on the control or eradication programs.

Isolation and Histopathological Changes Associated with Non-Tuberculous Mycobacteria in Lymph Nodes Condemned at a Bovine Slaughterhouse

Background: non-tuberculous mycobacteria (NTM) infect humans and animals and have a critical confounding effect on the diagnosis of bovine tuberculosis. The Official Mexican Standard (Norma Oficial Mexicana, NOM-ZOO-031-1995) for food safety regulates Mycobacterium bovis in cattle, but not the NTM species. The study's objective was to isolate and identify the NTM present in condemned bovine lymph nodes in a slaughterhouse, characterize the histological lesions, and correlate bacteriological and microscopic findings with the antemortem tuberculin skin test. Methods: from 528 cattle, one or two pooled samples of lymph nodes from each animal were cultured for Mycobacteria spp. and processed for histopathology. Results: mycobacteria were isolated from 54/528 (10.2%) of the condemned lymph nodes; 25/54 (46.2%) of these isolates were NTM; 4 bacteriological cultures with fungal contamination were discarded. Granulomatous and pyogranulomatous inflammation were present in 6/21 (28.6%) and 7/21 (33.3%) of the NTM-positive lymph nodes, respectively. The species of NTM associated with granulomatous lymphadenitis were M. scrofulaceum, M. triviale, M. terrae, and M. szulgai, while those causing pyogranulomatous lesions were M. szulgai, M. kansasii, M. phlei, and M. scrofulaceum. Conclusions: the NTM infections can cause false-positive results in the tuberculin test because of cross immune reactivity and interference with the postmortem identification of M. bovis in cattle.

Mycobacterial infections in wild boars (Sus scrofa) from Southern Switzerland: Diagnostic improvements, epidemiological situation and zoonotic potential

The occurrence of mycobacterial infections in different hosts and their implication as obligate or opportunistic pathogens remain mainly unclear. In addition to the well-known pathogenic members of the Mycobacterium tuberculosis - complex (MTBC), over 180 non-tuberculous mycobacteria (NTM) species have been described. Although the large majority of the NTM is assumed to be non-pathogenic to most individuals, an increasing trend in NTM infections has been observed over the last decades. The reasons of such augmentation are probably more than one: improved laboratory diagnostics, an increasing number of immunocompromised patients and individuals with lung damage are some of the possible aspects. Mandibular lymph nodes of 176 hunted wild boars from the pre-Alpine region of Canton Ticino, Switzerland, were collected. Following gross inspection, each lymph node was subjected to culture and to an IS6110 based real-time PCR specific for MTBC members. Histology was performed of a selection of lymph nodes (n = 14) presenting gross visible lesions. Moreover, accuracy of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) species identification was compared with sequence analysis of a combination of housekeeping genes. Mycobacteria of the MTBC were detected in 2.8% of the wild boars (n = 5; CI_95% 1.2-6.5) and were all confirmed to be Mycobacterium microti by molecular methods. In addition, based on the examined lymph nodes, NTM were detected in 57.4% (n = 101; CI_95% 50.0-64.5) of the wild boars originating from the study area. The 111 isolates belonged to 24 known species and three potentially undescribed Mycobacterium species. M. avium subsp. hominissuis thereby predominated (22.5%) and was found in lymph nodes with and without macroscopic changes. Overall, the present findings show that, with the exception of undescribed Mycobacterium species where identification was not possible (3.6%; 4/111), MALDI-TOF MS had a high concordance rate (90.1%; 100/111 isolates) to the sequence-based reference method.

Identification and molecular characterization of mycobacteria isolated from animal sources in a developing country

The essential role of animals in the transmission of infectious diseases has long been recognized. Apart from zoonosis due to Mycobacterium bovis in domestic cattle, acquired mycobacterial zoonosis from animals are vastly under-reported worldwide. This is partly the result of not recognizing that animals can be the source of zoonotic nontuberculous mycobacteria (NTM) infection. The present study intended to be a contribution to the knowledge of somewhat neglected role of animals in harboring, maintenance and dissemination of NTM in the environment. A total of 326 samples from 250 animals were collected and analyzed for the presence of mycobacteria using standard protocols. The preliminary identification and Runyon's classification of isolates were performed by conventional tests. The PCR amplification of a 228 bp fragment of 65-kDa heat shock protein (hsp) gene was applied for the genus identification and the partial sequence analysis of 16S rRNA was applied for the species identification. In total 32 isolates including 26 rapidly growing and 6 slowly growing mycobacteria were recovered from 250 animal samples (12.8%). The isolates recovered from 21 (65.60%) fish, 8 (25%) insects and 3 (9.4%) house cats, dogs and mice. M. fortuitum was the most frequent Mycobacterium spp (13 isolates; 40.6% of all isolates), followed by M. abscessus-chelonae-M. saopaulense group, (5 isolates; 15.6% of all isolates), M. iranicum (3 isolates; 9.4% of all isolates),and M. marinum, M. terrae complex and M. chlorophenolicum (2 isolates each; 18.8% of all isolates), and the single isolates of M. mucogenicum, M. neoaurum, M. conceptionense, M. virginiense, and M. gordonae (5 isolates; 15.6% of all isolates). The current study indicates that a variety of animals can be a permanent or transient source of mycobacterial agents. This ensures the life cycle of the bacteria and the chance of their survival in the environment, which may pose a potential threat to human health.

Disseminated Mycobacterium kansasii infection in a white-tailed deer and implications for public and livestock health

We document a case of Mycobacterium kansasii, a rare, zoonotic bacterium, in a white-tailed deer (WTD; Odocoileus virginianus) in East Baton Rouge Parish, Louisiana. Grossly, the deer had fibrinous pleuropneumonia with yellow, mineralized nodules scattered throughout the lungs and extending to the pleura. The kidneys were enlarged and had numerous pale foci in the cortex. Microscopically, the pulmonary architecture was replaced by variably sized, multifocal-to-coalescing granulomas with peripheral histiocytes and fewer multinucleate giant cells, and necrotic centers with mineralization and hemorrhage. The latter rarely contained one to a few acid-fast, slender, 7-µm long bacteria, for which beaded morphology was sometimes evident. Similar acid-fast bacteria were also within histiocytes in the kidney. PCR assay of fresh lung sample and subsequent sequencing revealed a non-tuberculosis mycobacterium, M. kansasii. These lesions were similar to those that result from infection with M. bovis in WTD. Both M. bovis and M. kansasii are zoonotic. WTD are a reservoir of M. bovis, which is a major concern in regions in which WTD and cattle can come into close contact.

Distribution and expression of esat-6 and cfp-10 in non-tuberculous mycobacteria isolated from lymph nodes of slaughtered cattle in Switzerland

The most commonly used tools for tuberculosis testing in cattle, the tuberculin skin test and the interferon-γ release assay, detect immune reactivity to various antigens of Mycobacterium bovis, including ESAT-6 and CFP-10. However, some non-tuberculous mycobacteria (NTM) can also harbor the cfp-10 and/or esat-6 genes, which can lead to false-positive results. We tested 77 NTM isolates belonging to 22 different species from lymph nodes of healthy slaughtered cattle for the occurrence of cfp-10 and esat-6. Most isolates did not harbor cfp-10 and esat-6. However, M. gordonae, 'M. lymphaticum', M. kansasii, and M. persicum were cfp-10 positive. The esat-6 gene was found in M. kansasii and M. persicum. Protein expression of cfp-10 and esat-6 could be detected for M. kansasii and M. persicum. An effective tuberculosis control program based on interferon-γ release assays and tuberculin skin testing is dependent on further monitoring and characterization of NTM in a cattle population.

Second line molecular diagnosis for bovine tuberculosis to improve diagnostic schemes

Surveillance of bovine tuberculosis (bTB) is partly based on the sanitary inspection of carcasses at the abattoir to detect bTB-like lesions which, in compliance with EU recommendations, are analysed by bacteriology and histopathology to disclose Mycobacterium bovis (or M. caprae) infection. Moreover, since 2012, a PCR method with similar sensitivity and specificity values of histopathology and bacteriology respectively is additionally employed in France, partially compensating for the weaknesses of classical diagnostic methods. We analysed a collection of bTB-like lesions from cattle presenting positive histological results albeit with negative PCR results. We present here the results of these samples, recovered from 292 animals culled between 2013 and 2016, analysed with a second line molecular diagnosis approach that consists in a combination of PCRs targeting the M. tuberculosis-M. avium complexes as well as the Mycobacterium genus and sequencing of hsp65 gene. These molecular analyses disclosed to identify the presence of non-tuberculous bacteria which could be responsible for most of these non-specific TB lesions: non tuberculous mycobacteria (24%) or Actinomycetales (56%) such as Rhodococcus equi (53%); 24% of the samples were negative. M. bovis -or any other MTBC members- was neither detected by molecular methods nor isolated in any of them at the end of the 3 months of culture. In conclusion, these results highlight the lack of specificity of histopathology and the usefulness of a first line PCR with a second line molecular diagnostic test to circumvent it. This diagnostic strategy makes it possible to reduce the number of suspect bTB cases raised at the abattoir or shortening their lock-up periods. By simplifying diagnostic schemes, the use of this tool could improve bTB surveillance and make eradication programs more efficient in the future.

First report of nodular skin lesions caused by Mycobacterium nebraskense in a 9-year-old cat

Case summary

A 9-year-old cat was referred with multiple, raised, ulcerative skin nodules in the region of the neck and dorsal head. Histopathological findings of a biopsied nodule were granulomatous dermatitis and panniculitis without multinucleated giant cells or caseous necrosis. In addition, by Ziehl–Neelsen staining numerous acid-fast intracellular bacilli were observed within the lesions. Mycobacterial culture showed growth of rough scotochromogenic colonies after 3 weeks of incubation. Molecular characterisation of the isolate identified Mycobacterium nebraskense as the cause of the infection. No phenotypic resistance was detected for the antimycobacterial agents tested. The cat was successfully treated with a combination of surgical excision and a 12 week course of antimicrobial therapy, including rifampicin combined with clarithromycin.

Relevance and novel information

To our knowledge, this is the first documented case of mycobacterial granulomatous dermatitis and panniculitis due to M nebraskense infection in a cat. The successful surgical and antimycobacterial treatment regimen is described.