Investigation of mycobacterial colonisation and invasion of the respiratory mucosa

Cytokine and Chemokine Concentrations as Biomarkers of Feline Mycobacteriosis

Mycobacteriosis is an emerging zoonotic disease of domestic cats and timely, accurate diagnosis is currently challenging. To identify differential cytokine/chemokine concentrations in serum/plasma of cats, which could be diagnostic biomarkers of infection we analysed plasma/serum from 116 mycobacteria-infected cats, 16 healthy controls and six cats hospitalised for unrelated reasons was analysed using the Milliplex MAP Feline Cytokine Magnetic Bead multiplex assay. Three cytokines; sFAS, IL-13 and IL-4 were reduced while seven; GM-CSF, IL-2, PDGF-BB, IL-8, KC, RANTES and TNF-α were elevated in mycobacteria-infected cats compared to healthy controls. However, IL-8 and KC concentrations were not significantly different from cats hospitalised for other reasons. Elevations in TNF-α and PDGF-BB may have potential to identify M. bovis and M. microti infected cats specifically while GM-CSF, IL-2 and FLT3L were increased in MTBC infected cats. This study demonstrates potential use of feline tuberculosis as a spontaneously occurring model of this significant human disease. Cytokine profiling has clear diagnostic potential for mycobacteriosis of cats and could be used discriminate tuberculous from non-tuberculous disease to rapidly inform on zoonotic risk. Future work should focus on the in-field utility of these findings to establish diagnostic sensitivity and specificity of these markers.

Serum concentrations of clarithromycin and rifampicin in pulmonary Mycobacterium avium complex disease: long-term changes due to drug interactions and their association with clinical outcomes

Background

Concomitant use of clarithromycin (CAM) and rifampicin (RFP) for the treatment of pulmonary Mycobacterium avium complex (MAC) disease affects the systemic concentrations of both drugs due to CYP3A4–related interactions. To date, however, there has been no report that investigates the long–term relationship between the drug concentrations, CYP3A4 activity, and clinical outcomes. Our aim was to investigate the time course of the drug levels in long–term treatment of subjects with pulmonary MAC disease, and examine the correlation of these concentrations with CYP3A4 activity and clinical outcomes.

Methods

Urine and blood samples from nine outpatients with pulmonary MAC disease were collected on days 1, 15, and 29 (for four subjects, sample collections were continued on days 57, 85, 113, 141, 169, 225, 281, 337, and 365). Serum drug concentrations and urinary levels of endogenous cortisol (F) and 6 beta-hydroxycortisol (6βOHF), the metabolite of F by CYP3A4, were measured, and evaluated 6βOHF/F ratio as a CYP3A4 activity marker. In addition, the clinical outcomes of 4 subjects were evaluated based on examination of sputum cultures and chest images.

Results

The mean 6βOHF/F ratio increased from 2.63 ± 0.85 (n = 9) on the first day to 6.96 ± 1.35 on day 15 and maintained a level more than double initial value thereafter. The serum CAM concentration decreased dramatically from an initial 2.28 ± 0.61 μg/mL to 0.73 ± 0.23 μg/mL on day 15. In contrast, the serum concentration of 14-hydroxy-CAM (M-5), the major metabolite of CAM, increased 2.4-fold by day 15. Thereafter, both CAM and M-5 concentrations remained constant until day 365. The explanation for the low levels of serum CAM in pulmonary MAC disease patients is that RFP-mediated CYP3A4 induction reached a maximum by day 15 and remained high thereafter. Sputum cultures of three of four subjects converted to negative, but relapse occurred in all three cases.

Conclusions

Our study demonstrated that serum CAM concentrations in pulmonary MAC disease patients were continuously low because of RFP-mediated CYP3A4 induction, which may be responsible for the unsatisfactory clinical outcomes.

Retrospective investigation of combination therapy with clarithromycin and levofloxacin for pulmonary Mycobacterium avium complex disease

Background

Fluoroquinolones are often used for the treatment of refractory Mycobacterium avium complex (MAC) disease when the clinical efficacy of the recommended regimen, which includes clarithromycin (CAM), rifampicin (RFP), and ethambutol (EB), is insufficient. However, recent in vitro and in vivo studies have suggested that fluoroquinolones decreased the antibacterial activity of CAM when they were administered in combination. In this study, we retrospectively investigated the influence of the combination of CAM and levofloxacin (LVFX) on clinical outcomes for pulmonary MAC disease patients.

Methods

Pulmonary MAC disease patients from 2010 to 2012 were divided into two groups, those who received LVFX together with CAM (LVFX group) and those who received CAM without LVFX (control group). The number of patients who showed improvement was evaluated at 1, 3, 6 and 12 months after the start of therapy based on bacteriological examination (culture and smear examination) and the bacilli negative conversion rate.

Results

There were no significant differences between the LVFX group (n = 18, 64.5 ± 6.5 years old) and the control group (n = 57, 71.0 ± 7.0 years old) in terms of gender, age, etiologic agent, baseline culture examination score, concomitant medication, and dosage of each drug. The clinical outcomes in the LVFX group were inferior to those in the control group at all endpoints and observational periods, and we found a significant difference in the percent improvement of the smear examination by fluorescence microscopy method (38 % vs. 83 %) and the bacilli negative conversion rate (38 % vs. 79 %) at 3 months. Our study suggests that the combination of CAM and LVFX causes unfavorable clinical outcomes for pulmonary MAC disease treatment. There was no significant difference between both groups in terms of frequency of adverse events.

Conclusion

The possibility that combined administration of CAM and LVFX causes unfavorable clinical outcomes for pulmonary MAC disease treatment was suggested.

Non-tuberculous mycobacterial disease is common in patients with non-cystic fibrosis bronchiectasis

BACKGROUND

Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms. Cystic fibrosis (CF) patients are susceptible to NTM, but data about NTM in patients with non-CF bronchiectasis are limited.

METHODS

We conducted a retrospective, descriptive study at the University of Illinois Medical Center. All patients diagnosed with bronchiectasis (code 494) using the International Classification of Diseases, ninth revision (ICD-9), between 1999 and 2006, were identified. Clinical data including lung function, radiology studies, and presence of NTM in sputum were abstracted for those who met the study criteria.

RESULTS

One hundred eighty-two patients were enrolled in the study. Patients were divided into two groups: bronchiectasis with NTM isolates (n = 68) and bronchiectasis without isolates (n =114), and compared for clinical characteristics and underlying diseases. Mycobacterium avium complex (MAC) was the most common isolate. Fifty-five patients (30%) met the American Thoracic Society criteria for diagnosis of NTM disease. Gram-negative rods were commonly co-isolated. The probability of NTM isolation was significantly higher in elderly female patients (p = 0.04). Moreover, the probability of NTM isolation was significantly higher in the female group with low body mass index (BMI) (p = 0.002).

CONCLUSIONS

NTM infections are common in non-CF bronchiectasis. MAC is the most frequently isolated NTM in these patients. There is also great variability in age and sex characteristics for NTM in non-CF bronchiectasis patients. Female patients with a low BMI are a high risk group for NTM infection in non-CF bronchiectasis. Routine screening for NTM is strongly recommended in this patient population.

Interaction of Bordetella bronchiseptica and Its Lipopolysaccharide with In Vitro Culture of Respiratory Nasal Epithelium

The nasal septa of fetal rabbits at 26 days of gestation were harvested by cesarean section of the does while under anesthesia and then exposed to Bordetella bronchiseptica or its lipopolysaccharide (LPS) for periods of 2 and 4 hours. A total of 240 explants were used. The tissues were examined using the Hematoxylin & Eosin technique. Then, semithin sections (0.5 μm) were stained with toluidine blue and examined with indirect immunoperoxidase (IPI) and lectin histochemistry. The most frequent and statistically significant findings were as follows: (1) cell death and increased goblet cell activity when exposed to bacteria and (2) cell death, cytoplasmic vacuolation and infiltration of polymorphonuclear leukocytes when exposed to LPS. The lesions induced by the bacterium were more severe than with LPS alone, except for the cytoplasmic vacuolation in epithelial cells. IPI stained the ciliated border of the epithelium with the bacterium more intensely, while LPS lectin histochemistry preferentially labeled the cytoplasm of goblet cell. These data indicate that B. bronchiseptica and its LPS may have an affinity for specific glycoproteins that would act as adhesion receptors in both locations.

Conversion of Mycobacterium smegmatis to a pathogenic phenotype via passage of epithelial cells during macrophage infection

Mycobacteria encounter many different cells during infection within their hosts. Although alveolar epithelial cells play an essential role in host defense as the first cells to be challenged upon contact with mycobacteria, they may contribute to the acquisition of mycobacterial virulence by increasing the expression of virulence or adaptation factors prior to being ingested by macrophages on the side of pathogens. From this aspect, the enhanced virulence of nonpathogenic Mycobacterium smegmatis (MSM) passed through human alveolar A549 epithelial cells (A-MSM) was compared to the direct infection of MSM (D-MSM) in THP-1 macrophages and mouse models. The intracellular growth rate and cytotoxicity of A-MSM were significantly increased in THP-1 macrophages. In addition, compared to D-MSM, A-MSM induced relatively greater interleukin (IL)-1β, IL-6, IL-8, IL-12, TNF-α, MIP-1α, and MCP-1 in THP-1 macrophages. As a next step, a more persistent A-MSM infection was observed in a murine infection model with the development of granulomatous inflammation. Finally, 58 genes induced specifically in A-MSM were partially identified by differential expression using a customized amplification library. These gene expressions were simultaneously maintained in THP-1 infection but no changes were observed in D-MSM. Bioinformatic analysis revealed that these genes are involved mainly in bacterial metabolism including energy production and conversion, carbohydrate, amino acid, and lipid transport, and metabolisms. Conclusively, alveolar epithelial cells promoted the conversion of MSM to the virulent phenotype prior to encountering macrophages by activating the genes required for intracellular survival and presenting its pathogenicity.

Targeted delivery of amikacin into granuloma

RATIONALE

Nontuberculous mycobacterial (NTM) infection is a growing problem in the United States and remains underrecognized in the developing world. The management of NTM infections is further complicated by several factors, including the need to use high systemic doses of toxic agents, the length of therapy, and the development of drug resistance.

OBJECTIVES

We have evaluated the use of monocyte-derived dendritic cells (DCs) as a delivery vehicle for a luminescent derivative of amikacin prepared by conjugation to fluorescein isothiocyanate (FITC) (amikacin-FITC) into granulomas formed in the tissues of mice infected with Mycobacterium avium.

METHODS

Amikacin-FITC was prepared and quantitative fluorescence was used to track the intracellular uptake of this modified antibiotic. The antibiotic activity of amikacin-FITC was also determined to be comparable to unmodified amikacin against M. avium. Amikacin-FITC-loaded DCs were first primed with M. avium, and then the cells were injected into the tail vein of infected mice. After 24 hours, the mice were sacrificed and the tissues were analyzed under fluorescence microscope.

MEASUREMENTS AND MAIN RESULTS

We found that we were able to deliver amikacin into granulomas in a mouse model of disseminated mycobacterial infection. No increase in levels of monocyte chemoattractant protein-1 and its CCR2 as markers of inflammation were found when DCs were treated with amikacin-FITC.

CONCLUSIONS

DC-based drug delivery may be an adjunct and useful method of delivering high local concentrations of antibiotics into mycobacterial granulomas.

Critical assessment of an in vitro bovine respiratory organ culture system: a model of bovine herpesvirus-1 infection

A bovine in vitro organ culture (BIVOC) system was evaluated as a model to study host and pathogen events during the course of bovine herpesvirus-1 infection. Upper respiratory tract epithelium, from slaughtered animals, was cultured in an air-liquid interface system and integrity, viability, and TNF-alpha gene expression of tissue explants were monitored over 72h in the presence or absence of infection by bovine herpesvirus type 1 (BHV-1). Uninfected explants maintained viability and integrity over the 72h time course although histological signs of degeneration were first visible from 24h of culture. Explants were productively infected with BHV-1 and typical, dose dependent, cytopathic changes were observed in response to infection. Regulation of TNF-alpha gene expression in uninfected explants varied over time and was region-specific but there was significant down-regulation of TNF-alpha gene expression at 2h post-infection when compared to uninfected controls at the same time point. Taking caveats into consideration the BIVOC system shows promise as a tool for analysis of immediate or early events in host-pathogen interaction.

Internalization of a non-pathogenic mycobacteria by macropinocytosis in human alveolar epithelial A549 cells

Mycobacterium smegmatis (MSM) a non-pathogenic mycobacterium is often employed as a tool to understand many aspects of the mycobacterial infections. However, its own biology and particularly its mechanism of entry into non-phagocytic cells are not well known. Previously, we demonstrated that Mycobacterium tuberculosis (MTB) invades epithelial cells by macropinocytosis. In the present study, we investigated whether MSM also invades human epithelial type II pneumocytes (A549) by macropinocytosis. Infection of A549 cells with MSM elicited actin filaments redistribution, lamellipodia formation and increased fluid phase uptake, suggesting macropinocytosis. Furthermore, macropinocytosis inhibitors like cytochalasin D and amiloride caused inhibition of fluid phase and bacterial uptake. We can conclude that MSM, like MTB, takes advantage of macropinocytosis for entry into epithelial cells, however, unlike MTB, internalized MSM are killed by host cells. These findings suggest that induction of macropinocytosis and cell invasion is not an exclusive feature of pathogenic organisms.

Mutation of the maturase lipoprotein attenuates the virulence of Streptococcus equi to a greater extent than does loss of general lipoprotein lipidation

Streptococcus equi is the causative agent of strangles, a prevalent and highly contagious disease of horses. Despite the animal suffering and economic burden associated with strangles, little is known about the molecular basis of S. equi virulence. Here we have investigated the contributions of a specific lipoprotein and the general lipoprotein processing pathway to the abilities of S. equi to colonize equine epithelial tissues in vitro and to cause disease in both a mouse model and the natural host in vivo. Colonization of air interface organ cultures after they were inoculated with a mutant strain deficient in the maturase lipoprotein (DeltaprtM(138-213), with a deletion of nucleotides 138 to 213) was significantly less than that for cultures infected with wild-type S. equi strain 4047 or a mutant strain that was unable to lipidate preprolipoproteins (Deltalgt(190-685)). Moreover, mucus production was significantly greater in both wild-type-infected and Deltalgt(190-685)-infected organ cultures. Both mutants were significantly attenuated compared with the wild-type strain in a mouse model of strangles, although 2 of 30 mice infected with the Deltalgt(190-685) mutant did still exhibit signs of disease. In contrast, only the DeltaprtM(138-213) mutant was significantly attenuated in a pony infection study, with 0 of 5 infected ponies exhibiting pathological signs of strangles compared with 4 of 4 infected with the wild-type and 3 of 5 infected with the Deltalgt(190-685) mutant. We believe that this is the first study to evaluate the contribution of lipoproteins to the virulence of a gram-positive pathogen in its natural host. These data suggest that the PrtM lipoprotein is a potential vaccine candidate, and further investigation of its activity and its substrate(s) are warranted.

Ciliostasis is a key early event during colonization of canine tracheal tissue by Bordetella bronchiseptica

The primary site of infection for Bordetella bronchiseptica, Bordetella pertussis and Bordetella parapertussis is the ciliated respiratory epithelium. Previous studies have implicated adherence of bacteria to cilia, induction of mucus production, induction of ciliostasis and damage to the ciliated epithelium in Bordetella pathogenesis. This paper describes the use of an air-interface organ culture system using canine tracheal tissue infected with B. bronchiseptica to assess the temporal relationship between these pathologies. Ciliostasis occurs very early during the host tissue-pathogen interaction, before mucus production and obvious signs of epithelial damage occur. A B. bronchiseptica bvg mutant does not colonize the organ culture model, induce ciliostasis or cause damage to the epithelial cell layer, but it does induce similar amounts of mucus release as does infection by wild-type bacteria. The authors propose that ciliostasis is a key early event during the B. bronchiseptica-host tissue interaction that abrogates the muco-ciliary defences of the host tissue, renders it susceptible to colonization by the bacteria and allows subsequent damage to the epithelium. The organ culture model described offers a physiologically relevant tool with which to characterize the molecular basis for interactions between Bordetella and its primary site of infection, the ciliated respiratory epithelium.

Inhibition of adherence of Mycobacterium avium complex and Mycobacterium tuberculosis to fibronectin on the respiratory mucosa

Mycobacterium species adhere to the respiratory mucosa via mucus and fibronectin of extracellular matrix exposed by damaged epithelium. We have investigated whether inhibiting adherence to fibronectin influences subsequent infection of human respiratory tissue by Mycobacterium avium complex and Mycobacterium tuberculosis. Human respiratory tissue was pretreated with mycobacterial fibronectin attachment proteins prior to infection with M. avium complex and M. tuberculosis and the number of recoverable bacteria over time was compared to untreated controls. Inhibition significantly reduced recovery of M. avium complex at 15min (P= 0.02), 7days (P = 0.04), and 14 days (P= 0.03); whereas recovery of M. tuberculosis was only reduced at 15 min (P = 0.01) and not at later timepoints. We conclude that M. avium complex and M. tuberculosis infection of the mucosa proceeds by different mechanisms, since M. tuberculosis infection is independent of fibronectin adherence.

Interaction between mycobacteria and mucus on a human respiratory tissue organ culture model with an air interface

Mycobacteria adhere specifically to extracellular matrix (ECM) and mucus with a fibrous, but not globular, appearance, in organ cultures of human respiratory mucosa examined by scanning electron microscopy. Previously, light microscopy sections made of tissue infected for 7 days demonstrated mycobacteria associated with mucus on the organ culture surface, and within submucosal glands in areas of damaged epithelium. The authors have now investigated the interactions between Mycobacterium avium complex (MAC), Mycobacterium tuberculosis (MTB), and Mycobacterium smegmatis (MS) and mucus by preincubating bacteria with purified mucins MUC5AC and MUC5B prior to inoculation onto the organ culture mucosal surface. They have also measured mucin production by the organ culture after mycobacterial infection. Mucus did not cause clumping of mycobacteria. There was a significant (P=.03) increase in the amount of fibrous mucus, but not globular mucus, observed on tissue inoculated with mucins compared to controls. The number of bacteria adhering to ECM was markedly reduced after incubation with mucins, which could indicate a protective effect. Mycobacterial infection did not increase mucin production by the organ culture. Mycobacterial adherence to mucins may play a role in the pathogenicity of mycobacteria in diseases such as cystic fibrosis, bronchiectasis, and chronic obstructive pulmonary disease (COPD), in which there are changes in mucus composition and clearance.