Mycobacterial Infection Research Articles

The Challenges of Diagnosing and Treating Nontuberculous Mycobacterial Infections in Low- and Middle-income Countries

The Challenges of Diagnosing and Treating Nontuberculous Mycobacterial Infections in Low- and Middle-income Countries

Analysis of alpha-1-antitrypsin (AAT)-regulated, glucocorticoid receptor-dependent genes in macrophages reveals a novel host defense function of AAT.

Alpha-1-antitrypsin (AAT) plays a homeostatic role in attenuating excessive inflammation and augmenting host defense against microbes. We demonstrated previously that AAT binds to the glucocorticoid receptor (GR) resulting in significant anti-inflammatory and antimycobacterial consequences in macrophages. Our current investigation aims to uncover AAT-regulated genes that rely on GR in macrophages. We incubated control THP-1 cells (THP-1control) and THP-1 cells knocked down for GR (THP-1GR-KD) with AAT, performed bulk RNA sequencing, and analyzed the findings. In THP-1control cells, AAT significantly upregulated 408 genes and downregulated 376 genes. Comparing THP-1control and THP-1GR-KD cells, 125 (30.6%) of the AAT-upregulated genes and 154 (41.0%) of the AAT-downregulated genes were significantly dependent on GR. Among the AAT-upregulated, GR-dependent genes, CSF-2 that encodes for granulocyte-monocyte colony-stimulating factor (GM-CSF), known to be host-protective against nontuberculous mycobacteria, was strongly upregulated by AAT and dependent on GR. We further quantified the mRNA and protein of several AAT-upregulated, GR-dependent genes in macrophages and the mRNA of several AAT-downregulated, GR-dependent genes. We also discussed the function(s) of selected AAT-regulated, GR-dependent gene products largely in the context of mycobacterial infections. In conclusion, AAT regulated several genes that are dependent on GR and play roles in host immunity against mycobacteria.

Exploring host-pathogen interactions in the Dictyostelium discoideum-Mycobacterium marinum infection model of tuberculosis.

Mycobacterium tuberculosis is a pathogenic mycobacterium that causes tuberculosis. Tuberculosis is a significant global health concern that poses numerous clinical challenges, particularly in terms of finding effective treatments for patients. Throughout evolution, host immune cells have developed cell-autonomous defence strategies to restrain and eliminate mycobacteria. Concurrently, mycobacteria have evolved an array of virulence factors to counteract these host defences, resulting in a dynamic interaction between host and pathogen. Here, we review recent findings, including those arising from the use of the amoeba Dictyostelium discoideum as a model to investigate key mycobacterial infection pathways. D. discoideum serves as a scalable and genetically tractable model for human phagocytes, providing valuable insights into the intricate mechanisms of host-pathogen interactions. We also highlight certain similarities between M. tuberculosis and Mycobacterium marinum, and the use of M. marinum to more safely investigate mycobacteria in D. discoideum.

Eosinophil Cell and Mass Appearance in Atypical Mycobacterium Infection of Lymphadenitis

Eosinophil Cell and Mass Appearance in Atypical Mycobacterium Infection of Lymphadenitis

Risk of lung diseases in patients with previous carbon monoxide poisoning: a nationwide population-based cohort study in the Republic of Korea

Introduction Carbon monoxide poisoning is associated with severe damage to various organs. In this study, we aimed to determine if previous carbon monoxide poisoning was associated with an increased risk of lung diseases. Methods The study population was derived from the National Health Insurance Service database of Korea between 1 January 2002 and 31 December 2021. Adults with carbon monoxide poisoning, with at least one visit to medical facilities between 2002 and 2021, were included. For comparison, an equal number of matched controls with the same index date were selected from the database. Results A total of 28,618 patients with carbon monoxide poisoning and 28,618 matched controls were included in this study. Approximately 42.8 per cent of the patient and control groups were female, with a mean age of 51.3 years. In patients with carbon monoxide poisoning, there was a significant increase in the risk of lung cancer (adjusted hazard ratio, 1.84; 95 per cent confidence interval, 1.42–2.39; P < 0.001), chronic obstructive pulmonary disease (adjusted hazard ratio, 1.60; 95 per cent confidence interval, 1.36–1.89; P < 0.001), pulmonary tuberculosis (adjusted hazard ratio, 1.46; 95 per cent confidence interval, 1.13–1.88; P = 0.003), and non-tuberculous mycobacterial infection (adjusted hazard ratio, 1.54; 95 per cent confidence interval, 1.01–2.36; P = 0.047). Discussion In this retrospective cohort study, previous carbon monoxide poisoning was associated with an increased risk of lung cancer, chronic obstructive pulmonary disease, pulmonary tuberculosis, and non-tuberculous mycobacterial infection. Further studies are needed to confirm such an association in other populations and the risk of lung diseases due to the toxic effect of carbon monoxide from different sources. Conclusions Previous carbon monoxide poisoning was associated with an increased risk of lung diseases, but the relative importance of the causes and sources of exposure was not known. The long-term management of survivors of acute carbon monoxide poisoning should include monitoring for lung cancer, chronic obstructive pulmonary disease, pulmonary tuberculosis, and non-tuberculous mycobacterial infection.

IQGAP1 domesticates macrophages to favor mycobacteria survival via modulating NF-κB signal and augmenting VEGF secretion

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), still ranks among the leading causes of annual human death by infectious disease. Mtb has developed several strategies to survive for years at a time within the host despite the presence of a robust immune response, including manipulating the progression of the inflammatory response and forming granulomatous lesions. Here we demonstrate that IQGAP1, a highly conserved scaffolding protein, compartmentalizes and coordinates multiple signaling pathways in macrophages infected with Mycobacterium marinum (Mm or M.marinum), the closest relative of Mtb. Upregulated IQGAP1 ultimately suppresses TNF-α production by repressing the MKK3 signal and reducing NF-κBp65 translocation, deactivating the p38MAPK pathway. Accordingly, IQGAP1 silencing and overexpression significantly alter p38MAPK activity by modulating the production of phosphorylated MKK3 during mycobacterial infection. Pharmacological inhibition of IQGAP1-associated microtubule assembly not only alleviates tissue damage caused by M.marinum infection but also significantly decreases the production of VEGF—a critical player for granuloma-associated angiogenesis during pathogenic mycobacterial infection. Similarly, IQGAP1 silencing in Mm-infected macrophages diminishes VEGF production, while IQGAP1 overexpression upregulates VEGF. Our data indicate that mycobacteria induce IQGAP1 to hijack NF-κBp65 activation, preventing the expression of proinflammatory cytokines as well as promoting VEGF production during infection and granuloma formation. Thus, therapies targeting host IQGAP1 may be a promising strategy for treating tuberculosis, particularly in drug-resistant diseases.

Tristetraprolin mediates immune evasion of mycobacterial infection in macrophages.

Immune evasion of Mycobacterium tuberculosis (Mtb) facilitates intracellular bacterial growth. The mechanisms of immune evasion, however, are still not fully understood. In this study, we reveal that tristetraprolin (TTP), one of the best characterized RNA-binding proteins controlling the stability of targeted mRNAs, mediates innate immune evasion of mycobacteria. We found that TTP knockout mice displayed reduced bacterial burden in the early stage after Mtb aerosol challenge. Macrophages deficient in TTP also showed an inhibition in intracellular mycobacterial growth. Live mycobacteria induced TTP protein expression in macrophages, which was blocked by the mTOR inhibitor rapamycin. Rapamycin and AZD8055 specifically blocked 4EBP1 phosphorylation in infected macrophages and suppressed intracellular BCG growth. Rapamycin promoted TTP protein degradation through the ubiquitination pathway, whereas the proteasome inhibitor MG-132 blocked rapamycin function and thus stabilized TTP protein. TTP induction suppressed the expression of iNOS/TNF-α/IL-12/IL-23, and weakened protective immune responses in macrophages, whereas rapamycin enhanced the bactericidal effects through TTP inhibition. Moreover, blocking TTP binding increased the expression of TNF-α and iNOS and suppressed intracellular mycobacterial growth. Overall, our study reveals a novel role for RNA-binding protein TTP in Mtb immune evasion mechanisms and provides a potential target for host-directed therapy against tuberculosis (TB).

Opportunistic Infections, Mortality Risk, and Prevention Strategies in Patients With Vacuoles, E1 Enzyme, X-Linked, Autoinflammatory, Somatic (VEXAS) Syndrome

Abstract Background VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome is a genetic disorder characterized by bone marrow failure and systemic inflammation, putting patients at risk for infections. This study comprehensively examines the prevalence of opportunistic infections in patients with VEXAS, evaluating their impact on clinical outcomes and potential preventive measures. Methods Patients with confirmed VEXAS were included. Survival analysis and logistic regression were used to identify associations between opportunistic infections and mortality. Infection rates (IRs) for Pneumocystis jirovecii pneumonia (PJP) and alphaherpesviruses were calculated over a prospective 8-month observation period in relationship to prophylaxis. Results Of 94 patients with VEXAS, 6% developed PJP; 15% had alphaherpesvirus reactivation, with varicella zoster virus (VZV) being the most common herpesvirus; and 10% contracted a nontuberculous mycobacterial (NTM) infection. Risk of death was significantly increased per month following a diagnosis of PJP (hazard ratio [HR], 72.41 [95% confidence interval {CI}, 13.67–533.70]) or NTM (HR, 29.09 [95% CI, 9.51–88.79]). Increased odds for death were also observed in patients with a history of herpes simplex virus (HSV) reactivation (odds ratio [OR], 12.10 [95% CI, 1.29–114.80]) but not in patients with VZV (OR, 0.89 [95% CI, .30–2.59]). Prophylaxis for PJP (IR, 0.001 vs 0 per person-day, P &amp;lt; .01) and VZV (IR, 0.006 vs 0 per person-day, P = .04) markedly decreased infection rates with a number needed to treat of 4 and 7, respectively. Conclusions Opportunistic infections are common in patients with VEXAS. Patients who develop PJP, HSV, or NTM are at increased risk for death. Prophylaxis against PJP and VZV is highly effective.

Fatal co-infection by multiple pathogens in an indigenous woman with autoimmune hemolytic anemia and tuberculosis: a case report

BackgroundTuberculosis (TB), one of the leading causes of death worldwide, has a higher incidence among indigenous people. Albeit uncommon, autoimmune hemolytic anemia (AIHA) has been deemed a risk condition to develop mycobacterial infection, as a result of the immunosuppressive treatments. TB, in turn, can be a predisposing factor for secondary infections.Case presentationHere we present a case of a 28-year-old indigenous woman from Colombia, previously diagnosed with AIHA and pulmonary TB. Despite various treatments, therapies and medical interventions, the patient died after severe medullary aplasia of multiple causes, including secondary myelotoxicity by immunosuppressive therapy and secondary disseminated infections, underlining infection by Staphylococcus aureus, Klebsiella pneumoniae and Candida glabrata, which were identified as drug-resistant microorganisms. Together, this led to significant clinical complications. Invasive aspergillosis was diagnosed at autopsy.ConclusionsThis report presents a rarely finding of AIHA followed by TB, and highlights the great challenges of dealing with co-infections, particularly by drug resistant pathogens. It also aims to spur governments and public health authorities to focus attention in the prevention, screening and management of TB, especially among vulnerable communities, such as indigenous people.

Non-tuberculous mycobacterial infection over abdomen: an interesting case report

Non-tuberculous mycobacterial infection over abdomen: an interesting case report

PDCD4 as a marker of mTOR pathway activation and therapeutic target in mycobacterial infections.

This study emphasizes the critical role of the mammalian target of rapamycin (mTOR) pathway in macrophage responses to mycobacterial infections, elucidating how mycobacteria activate mTOR, resulting in PDCD4 degradation. The utilization of the (Tor)-signal-indicator (TOSI) vector for real-time monitoring of mTOR activity represents a significant advancement in understanding mTOR regulation during mycobacterial infection. These findings deepen our comprehension of mycobacteria's innate immune mechanisms and introduce PDCD4 as a novel marker for mTOR activity in infectious diseases. Importantly, this research laid the groundwork for high-throughput screening of mTOR inhibitors using FDA-approved drugs, offering the potential for repurposing treatments against mycobacterial infections. The identification of drugs that inhibit mTOR activation opens new avenues for host-directed therapies, marking a significant step forward in combating tuberculosis and other mycobacterial diseases.

A clinical case of non-tuberculosis mycobacterial infection of the lungs and larynx

ABSTRACT. An actual clinical case of the diagnosis and course features of non-tuberculosis mycobacterial infection (NTMI) of the lungs and larynx in a patient treated at the Zaporizhzhia Regional Phthisiopulmonology Clinical Treatment and Diagnostic Center is presented. The clinical case demonstrates the difficulty of differential diagnosis of NTMI of the lung caused by scotochromogenic mycobacterium and tuberculosis, since the clinical and radiological manifestations for both diseases are identical, and there are no pathognomonic symptoms of NTMI. NTM affect the respiratory system and mimic the symptoms of tuberculosis, which significantly complicates not only timely differential diagnosis, but also leads to “treatment failure” of tuberculosis, which the patient did not have. After a month of antimycobacterial treatment an ulcerative lesion of the right vocal fold was diagnosed in the patient. Detection of the culture of NTM 1.5 months after its inoculation was the only one method of diagnosis in this case, the diagnosis NTMI of both the lungs and the larynx was made considering those results. The patient did not receive appropriate treatment before receiving the results of the bacteriological examination, which led to the development of negative clinical and radiological dynamics. But, despite the late diagnosis of NTMI, after 6 months of appropriate treatment the patient had a positive clinical and X-ray dynamics with healing of the ulcerative lesion of the right vocal fold. Thus, the presented case shows that despite the late diagnosis of NTMI of the lungs, which was complicated by NTMI of the larynx during antimycobacterial therapy, in the absence of severe concomitant lung diseases in the patient, after 6 months of appropriate treatment of NTMI, it was possible to achieve positive clinical and radiological dynamics with complete healing of the ulcerative lesion of the right vocal fold.

Promoter characterization of relZ-bifunctional (pp)pGpp synthetase in mycobacteria.

The second messenger guanosine 3',5'-bis(diphosphate)/guanosine tetraphosphate (ppGpp) and guanosine 3'-diphosphate 5'-triphosphate/guanosine pentaphosphate (pppGpp) ((p)ppGpp) has been shown to be crucial for the survival of mycobacteria under hostile conditions. Unexpectedly, deletion of primary (p)ppGpp synthetase-Rel did not completely diminish (p)ppGpp levels leading to the discovery of novel bifunctional enzyme-RelZ, which displayed guanosine 5'-monophosphate,3'-diphosphate (pGpp), ppGpp, and pppGpp ((pp)pGpp) synthesis and RNAseHII activity. What conditions does it express itself under, and does it work in concert with Rel? The regulation of its transcription and whether the Rel enzyme plays a role in such regulation remain unclear. In this article, we have studied relZ promoter and compared its activity with rel promoter in different growth conditions. We observed that the promoter activity of relZ was constitutive; it is weaker than rel promoter, lies within 200 bp upstream of translation-start site, and it increased under carbon starvation. Furthermore, the promoter activity of relZ was compromised in the rel-knockout strain in the stationary phase. Our study unveils the dynamic regulation of relZ promoter activity by SigA and SigB sigma factors in different growth phases in mycobacteria. Importantly, elucidating the regulatory network of RelZ would enable the development of the targeted interventions for treating mycobacterial infections.

First report of Mycobacterium chimaera infection in a patient with chronic granulomatous disease

Chronic granulomatous disease (CGD) is an inborn error of immunity. NADPH oxidase is an enzyme complex that produces various reactive oxygen species, such as superoxide anions and hydrogen peroxide. Mycobacterial infections in CGD are commonly observed in countries with a high prevalence of these microorganisms, such as those receiving the BCG vaccination at birth or having a high prevalence of tuberculosis. Non-tuberculous mycobacteria (NTM) infections are rare in CGD. The patient also presented with hemophagocytic lymphohistiocytosis, which resolved with gammaglobulin and cyclosporine. Herein, we describe the first case of M. chimaera infection in a female patient with autosomal recessive CGD caused by a pathogenic variant in CYBA.

Rare and novel complications of botulinum neurotoxin type A and dermal filler injections

Botulinum neurotoxin type A (BoNTA) and filler injection procedures usually provide predicted outcomes with a low incidence of complications. Most of the complications after these procedures have been extensively discussed. In this study, we report on these injectables’ less well-known, recently reported, and novel complications and attempt to clarify the underlying mechanisms. Counterfeit or mishandled BoNTA has been associated with botulism. BoNTA has been linked to uncommon complications, including morphea-like lesions, nontuberculous mycobacterial infections, vascular occlusion, and pseudoaneurysm of the superficial temporal artery. Unusual complications from filler injection include nonscarring alopecia, intraoral necrosis, nontuberculous mycobacterial infections, xanthelasma-like reactions, intracranial perforation, and pneumosinus dilatans. Post-BoNTA injection nodules and filler infection from bone destruction due to cocaine use are new complications. These complications pose a challenge for diagnosis and treatment. This publication aims to assist in promptly identifying and managing these rare and novel complications when necessary.

Epidemiological assessment of non-tuberculous mycobacterial cervicofacial lymphadenitis: A PHIS database study

ObjectiveCervicofacial lymphadenitis caused by non-tubercular mycobacterial (NTM) infections has the highest infection rate in children. Our objective was to assess patient demographics, treatment methods, and the impact of weather and geography on the incidence of disease in patients with NTM cervicofacial lymphadenitis. MethodsThe Pediatric Health Information System (PHIS) database was queried for data on all patients diagnosed with concurrent cervicofacial lymphadenopathy and NTM infection from 2004 to 2022. We assessed the association between weather patterns and NTM cervicofacial lymphadenitis by collecting monthly weather data from the NOAA National Center for Environmental Information. Incidence rates were calculated by dividing the number of cases by the total hospital discharges during the study period. ResultsAmong 47 PHIS hospitals, there were 992 diagnoses of NTM cervicofacial lymphadenitis. The average age at diagnosis was 2 [IQR, 2–4], with 59 % female. Drainage of skin abscesses or lesions was performed for 93 (9.4 %) patients, while 15 (1.5 %) had an excisional procedure of the CPT codes assessed. The most common antibiotics utilized were cephalosporins (28 %), macrolides (27 %), and rifampin (12 %). The most common treatment method was surgery with antibiotics (37 %) followed by no treatment at all (35 %), surgery alone (17 %), and antibiotics alone (10 %). Of the 28 states included in the analysis, Washington (IR: 3.5) and Nebraska (IR: 3.3) had the highest incidence rates (IR) of NTM cervical lymphadenitis. The cases were relatively equally distributed across the different weather seasons within each U.S. geographic region. However, the overall average wind speed was weakly associated with increasing the risk of diagnosis when utilizing a mixed effect zero-inflated negative binomial model (Incidence Ratio: 1.07, 95 % CI: (1.01–1.14), p = 0.035). ConclusionsOur results indicate that the most common treatment method utilized in patients within our cohort with NTM cervicofacial lymphadenitis was the concurrent use of surgery and antibiotics. Our results also indicate there may be variation in the incidence rate among different states, but additional studies are needed as our cohort only included approximately 50 % of states within the U.S.

Mapping Crohn's Disease Pathogenesis with Mycobacterium paratuberculosis: A Hijacking by a Stealth Pathogen.

Mycobacterium avium ssp. paratuberculosis (MAP) has been implicated in the development of Crohn's disease (CD) for over a century. Similarities have been noted between the (histo)pathological presentation of MAP in ruminants, termed Johne's disease (JD), and appearances in humans with CD. Analyses of disease presentation and pathology suggest a multi-step process occurs that consists of MAP infection, dysbiosis of the gut microbiome, and dietary influences. Each step has a role in the disease development and requires a better understanding to implementing combination therapies, such as antibiotics, vaccination, faecal microbiota transplants (FMT) and dietary plans. To optimise responses, each must be tailored directly to the activity of MAP, otherwise therapies are open to interpretation without microbiological evidence that the organism is present and has been influenced. Microscopy and histopathology enables studies of the mycobacterium in situ and how the associated disease processes manifest in the patient e.g., granulomas, fissuring, etc. The challenge for researchers has been to prove the relationship between MAP and CD with available laboratory tests and methodologies, such as polymerase chain reaction (PCR), MAP-associated DNA sequences and bacteriological culture investigations. These have, so far, been inconclusive in revealing the relationship of MAP in patients with CD. Improved and accurate methods of detection will add to evidence for an infectious aetiology of CD. Specifically, if the bacterial pathogen can be isolated, identified and cultivated, then causal relationships to disease can be confirmed, especially if it is present in human gut tissue. This review discusses how MAP may cause the inflammation seen in CD by relating its known pathogenesis in cattle, and from examples of other mycobacterial infections in humans, and how this would impact upon the difficulties with diagnostic tests for the organism.

Applications and advances in molecular diagnostics: revolutionizing non-tuberculous mycobacteria species and subspecies identification.

Non-tuberculous mycobacteria (NTM) infections pose a significant public health challenge worldwide, affecting individuals across a wide spectrum of immune statuses. Recent epidemiological studies indicate rising incidence rates in both immunocompromised and immunocompetent populations, underscoring the need for enhanced diagnostic and therapeutic approaches. NTM infections often present with symptoms similar to those of tuberculosis, yet with less specificity, increasing the risk of misdiagnosis and potentially adverse outcomes for patients. Consequently, rapid and accurate identification of the pathogen is crucial for precise diagnosis and treatment. Traditional detection methods, notably microbiological culture, are hampered by lengthy incubation periods and a limited capacity to differentiate closely related NTM subtypes, thereby delaying diagnosis and the initiation of targeted therapies. Emerging diagnostic technologies offer new possibilities for the swift detection and accurate identification of NTM infections, playing a critical role in early diagnosis and providing more accurate and comprehensive information. This review delineates the current molecular methodologies for NTM species and subspecies identification. We critically assess the limitations and challenges inherent in these technologies for diagnosing NTM and explore potential future directions for their advancement. It aims to provide valuable insights into advancing the application of molecular diagnostic techniques in NTM infection identification.

Tribbles1 is host protective during in vivo mycobacterial infection.

Tuberculosis is a major global health problem and is one of the top 10 causes of death worldwide. There is a pressing need for new treatments that circumvent emerging antibiotic resistance. Mycobacterium tuberculosis parasitises macrophages, reprogramming them to establish a niche in which to proliferate, therefore macrophage manipulation is a potential host-directed therapy if druggable molecular targets could be identified. The pseudokinase Tribbles1 (Trib1) regulates multiple innate immune processes and inflammatory profiles making it a potential drug target in infections. Trib1 controls macrophage function, cytokine production, and macrophage polarisation. Despite wide-ranging effects on leukocyte biology, data exploring the roles of Tribbles in infection in vivo are limited. Here, we identify that human Tribbles1 is expressed in monocytes and is upregulated at the transcript level after stimulation with mycobacterial antigen. To investigate the mechanistic roles of Tribbles in the host response to mycobacteria in vivo, we used a zebrafish Mycobacterium marinum (Mm) infection tuberculosis model. Zebrafish Tribbles family members were characterised and shown to have substantial mRNA and protein sequence homology to their human orthologues. trib1 overexpression was host-protective against Mm infection, reducing burden by approximately 50%. Conversely, trib1 knockdown/knockout exhibited increased infection. Mechanistically, trib1 overexpression significantly increased the levels of proinflammatory factors il-1β and nitric oxide. The host-protective effect of trib1 was found to be dependent on the E3 ubiquitin kinase Cop1. These findings highlight the importance of Trib1 and Cop1 as immune regulators during infection in vivo and suggest that enhancing macrophage TRIB1 levels may provide a tractable therapeutic intervention to improve bacterial infection outcomes in tuberculosis.

MYCOLICIBACTERIUM FORTUITUM INFECTION IN EX SITU EMERALD TREE BOA (Corallus batesii).

Emerald tree boas (Corallus batesii) are boids that in situ occurs in forested habitats in the Amazon Basin. The mycobacterial species can infect reptiles but the species Mycolicibacterium fortuitum was identified only in feces samples of ex situ Python regius and was isolated from granulomatous lesions of an ex situ Iguana iguana when was still part of the genus Mycobacterium. This article aims to report a mycobacteria infection case in a female Corallus batesii kept under human care. The animal presented apathy and 2months of anorexia, being found dead. The necropsy revealed presence of tracheal and pulmonary nodules besides multifocal, bacterial, granulomatous pneumonia. After Fite-Faraco histochemical staining, immunohistochemistry, semi-nested polymerase chain reaction (PCR) and genetic sequencing the Mycolicibacterium fortuitum complex was diagnosed with 99.54% of nucleotide similarity. This mycobacterial species was already pointed out as an important nosocomial pathogen and more studies are necessary to explore their zoonotic potential.