Antimicrobial activities of clarithromycin, gatifloxacin and sitafloxacin, in combination with various antimycobacterial drugs against extracellular and intramacrophage Mycobacterium avium complex

Polypharmacological strategies for infectious bacteria

Polypharmacological approaches have significant potential for the treatment of various complex diseases, including infectious bacteria-related diseases. Actually, multitargeting agents can achieve better therapeutic effects and overcome the drawbacks of monotherapy. Although multidrug multitarget strategies have demonstrated the ability to inactivate infectious bacteria, several challenges have been pointed out. In this way, multitarget direct ligands approaches appear to be a rational and sustainable strategy to combat antibiotic resistance. By combining different pharmacophores, antibiotic hybrids stand out as a promising application in the field of bacterial infections. These new chemical entities can achieve synergistic interactions that allow to extend the spectrum of action and target multiple pathways. In addition, antibiotic hybrids can reduce the likelihood of resistance development and provide improved chemical stability. It is worth highlighting that despite the efforts of the scientific community to discover new solutions for the most complex diseases, there is a significant lack of studies on biofilm-associated infections. This review describes the different polypharmacological approaches that can be used to treat bacterial infections with a particular focus, whenever possible, on those promoted by biofilms. By exploring these innovative approaches, we aim to inspire further research and progress in the search for effective treatments for infectious bacteria-related diseases, including biofilm-related ones. SIGNIFICANCE STATEMENT: The importance of the proposed topic lies in the escalating challenge of antibiotic resistance, particularly in the context of infectious bacteria-related infections. Polypharmacological approaches, such as antibiotic hybrids, represent innovative strategies to combat bacterial infections. By targeting multiple signaling pathways, these approaches not only enhance therapeutic effect but also reduce the development of resistance while improving the drug's chemical stability. Despite the urgent need to combat bacterial infectious diseases, there is a notable research gap, in particular in biofilm-related ones. This review highlights the critical importance of exploring polypharmacological approaches with the aim of motivating further research and advances in effective treatments for infectious bacteria, including biofilm related infections.

The synergetic effect of sitafloxacin-arbekacin combination in the Mycobacterium abscessus species

Mycobacterium abscessus species (MABS) is the most commonly isolated rapidly growing mycobacteria (RGM) and is one of the most antibiotic-resistant RGM with rapid progression, therefore, treatment of MABS is still challenging. We here presented a new combination treatment with sitafloxacin that targeted rough morphotypes of MABS, causing aggressive infections. Thirty-four clinical strains of MABS were isolated from various clinical samples at the Juntendo university hospital from 2011 to 2020. The susceptibility to a combination of sitafloxacin and antimicrobial agents was compared to that of the antimicrobial agents alone. Out of 34 MABS, 8 strains treated with sitafloxacin-amikacin combination, 9 of sitafloxacin-imipenem combination, 19 of sitafloxacin-arbekacin combination, and 9 of sitafloxacin-clarithromycin combination showed synergistic effects, respectively. Sitafloxacin-arbekacin combination also exhibited the synergistic effects against 10 of 22 Mycobacterium abscessus subspecies massiliense (Mma) strains and 8 of 11 Mycobacterium abscessus subspecies abscessus (Mab) strains, a highly resistant subspecies of MABS. The sitafloxacin-arbekacin combination revealed more synergistic effects in rough morphotypes of MABS (p = 0.008). We demonstrated the synergistic effect of the sitafloxacin-arbekacin combination against MABS. Further, this combination regimen might be more effective against Mab or rough morphotypes of MABS.

Efficacy and safety of fluoroquinolone-containing regimens in treating pulmonary Mycobacterium avium complex disease: A propensity score analysis

Background

Although combination therapy using clarithromycin, rifampicin, and ethambutol is recommended for patients with pulmonary Mycobacterium avium complex (MAC) disease, some patients do not tolerate it because of adverse effects or underlying diseases. The efficacy and safety of fluoroquinolone-containing combination regimens as an alternative remain uncertain. This study aimed to compare the efficacy and safety of fluoroquinolone-containing regimens with those of the standard regimens for treating pulmonary MAC disease.

Methods

We retrospectively included consecutive MAC patients who were treated in our hospital between January 2011 and May 2019. Patients treated with fluoroquinolone-containing regimens who had relapsed after treatment with standard regimens were excluded. A propensity score analysis was conducted to reduce selection bias, and the proportions of clinical improvement, defined by chest imaging findings and sputum conversion, were compared between the fluoroquinolone-containing regimen and standard regimen groups.

Results

We analyzed 28 patients who received fluoroquinolone-containing regimens and 46 who received the standard regimen. Fluoroquinolone-containing regimens were more likely selected for patients with cavitary lesions, diabetes mellitus, culture negativity, a low daily physical activity level, a decreased lymphocyte count and an increased CRP level. The propensity score was calculated using these variables (C-statistic of the area under the receiver operating characteristic curve of the propensity score: 0.807, p < 0.0001). The fluoroquinolone-containing regimens were significantly inferior to the standard regimen in clinical improvements (p = 0.002, Log-rank test) in the univariate analysis, but the significance was lost after adjusting for the propensity score (HR 0.553, 95% CI 0.285–1.074, p = 0.080). Six (21%) patients in the fluoroquinolone-containing regimen group and ten (22%) patients in the standard regimen group experienced low-grade adverse effects.

Conclusions

There was no significant difference in clinical improvement between these regimens after propensity score adjustment. A large-scale prospective study is required to validate these results.

Mycobacterium avium Complex Disease

Despite the ubiqitous nature of Mycobacterium avium complex (MAC) organisms in the environment, relatively few of those who are infected develop disease. Thus, some degree of susceptibility due to either underlying lung disease or immunosuppression is required. The frequency of pulmonary MAC disease is increasing in many areas, and the exact reasons are unknown. Isolation of MAC from a respiratory specimen does not necessarily mean that treatment is required, as the decision to treatment requires the synthesis of clinical, radiographic, and microbiologic information as well as a weighing of the risks and benefits for the individual patient. Successful treatment requires a multipronged approach that includes antibiotics, aggressive pulmonary hygiene, and sometimes resection of the diseased lung. A combination of azithromycin, rifampin, and ethambutol administered three times weekly is recommend for nodular bronchiectatic disease, whereas the same regimen may be used for cavitary disease but administered daily and often with inclusion of a parenteral aminoglycoside. Disseminated MAC (DMAC) is almost exclusively seen in patients with late-stage AIDS and can be treated with a macrolide in combination with ethambutol, with or without rifabutin: the most important intervention in this setting is to gain HIV control with the use of potent antiretroviral therapy. Treatment outcomes for many patients with MAC disease remain suboptimal, so new drugs and treatment regimens are greatly needed. Given the high rate of reinfection after cure, one of the greatest needs is a better understanding of where infection occurs and how this can be prevented.

Effects of Fluoroquinolones and Azithromycin on Biofilm Formation of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an opportunistic pathogen that causes respiratory and urinary tract infections, as well as wound infections in immunocompromised patients. This pathogen is difficult to treat due to increased resistance to many antimicrobial agents. We investigated the in vitro biofilm formation of S. maltophilia, including effects of fluoroquinolones (FQs) and azithromycin on biofilm formation. The organism initiated attachment to polystyrene surfaces after a 4 h incubation period, and reached maximal growth at 18–24 h. In the presence of FQs (moxifloxacin, levofloxacin or ciprofloxacin), the biofilm biomass was significantly reduced (P < 0.05). A lower concentration of moxifloxacin (10 μg/mL) exhibited a better inhibiting effect on biofilm formation than 100 μg/mL (P < 0.01), but with no difference in effect compared to the 50 μg/mL concentration (P > 0.05). However, the inhibitory effects of 10 μg/mL of levofloxacin or ciprofloxacin were slightly less pronounced than those of the higher concentrations. A combination of azithromycin and FQs significantly reduced the biofilm inhibiting effect on S. maltophilia preformed biofilms compared to azithromycin or FQs alone. We conclude that early use of clinically acceptable concentrations of FQs, especially moxifloxacin (10 μg/mL), may possibly inhibit biofilm formation by S. maltophilia. Our study provides an experimental basis for a possible optimal treatment strategy for S. maltophilia biofilm-related infections.

Antagonistic effects of indoloquinazoline alkaloids on antimycobacterial activity of evocarpine

AIMS

The interaction of quinolone and indoloquinazoline alkaloids concerning their antimycobacterial activity was studied.

METHODS AND RESULTS

The antimycobacterial and modulating activity of evodiamine (1), rutaecarpine (2) and evocarpine (3) was tested on mycobacteria including three multidrug-resistant (MDR) clinical isolates of Mycobacterium tuberculosis. Antagonistic effects were concluded from fractional inhibitory concentration (FICI) values. Interaction energies of the compounds were calculated using GLUE docking module implemented in GRID. 1 and 2 exhibited weak inhibition of rapidly growing mycobacteria, however, 1 was active against Myco. tuberculosis H37Rv (MIC = 10 mg l(-1) ) while 2 was inactive. Both 1 and 2 showed a marked antagonistic effect on the susceptibility of different mycobacterial strains to 3 giving FICI values between 5 and 9. The interaction energies between compounds 1 and 2 with compound 3 suggested the possibility of complex formation in solution.

CONCLUSIONS

Indoloquinazoline alkaloids markedly reduce the antimycobacterial effect of the quinolone alkaloid evocarpine. Complex formation may play a role in the attenuation of its antimycobacterial activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study gives a striking example of antagonism between compounds present in the same plant extract which should be considered in natural product based screening projects.

Activities of moxifloxacin in combination with macrolides against clinical isolates of Mycobacterium abscessus and Mycobacterium massiliense

Infections caused by Mycobacterium abscessus and Mycobacterium massiliense are on the rise among humans. Although macrolides, including clarithromycin (CLR) and azithromycin (AZM), are key antibiotics for the treatment of M. abscessus and M. massiliense infections, treatment regimens for these infections are still largely undefined. In this study, we evaluated the in vitro, ex vivo, and in vivo activities of moxifloxacin (MXF) in combination with macrolides against clinically isolated M. abscessus and M. massiliense strains. Overall, CLR, AZM, and MXF alone showed activity against both species in vitro, ex vivo, and in vivo. When MXF was combined with a macrolide against M. abscessus isolates, antagonism was observed in 65.4% (17/26) of the strains with CLR and 46.2% (12/26) of the strains with AZM in vitro as well as in 66.7% (10/15) of the strains with CLR and 40.0% (6/15) of the strains with AZM in macrophages as determined by the fractional inhibitory concentration index. In contrast, either indifferent or synergistic effects of the MXF-macrolide combinations were observed against only M. massiliense strains. Moreover, a murine infection model showed similar results. Antagonism between the MXF and macrolide combinations was observed in five out of seven M. abscessus strains, while indifferent and synergistic effects for these combinations were observed for three of the six M. massiliense strains tested, respectively. In conclusion, the activity of MXF in combination with a macrolide differed for M. abscessus and M. massiliense infections and the addition of MXF to macrolide therapy had no benefit for the treatment of M. abscessus infections.

Relationship between clinical efficacy for pulmonary MAC and drug-sensitivity test for isolated MAC in a recent 6-year period

There are a few recent reports about the relationship between the clinical effect and drug-sensitivity test. We investigated the relationship between the clinical efficacy of treatment for pulmonary Mycobacterium avium complex (MAC) and drug-sensitivity test for isolated MAC by comparison between data from 2005 to 2007 and from 2008 to 2010. We studied 60 patients who satisfied diagnostic criteria of nontuberculous mycobacterial infection established by the American Thoracic Society in 2007 and who received combination therapy using rifampicin (RFP), ethambutol (EB), streptomycin (SM), and clarithromycin (CAM). Average CAM dosage was increased from the early (517 mg/day) to the later (800 mg/day) period. Sputum conversion rate increased from 63% in the early period to 83% in the later period. Clinical improvement also increased from 38% in the early period to 53% in the later period. The causative microorganisms isolated were M. avium in 35 patients and M. intracellulare in 25. In both periods, isolated MAC strains showed excellent minimum inhibitory concentration (MIC) for CAM. Regarding the relationship between clinical efficacy and MICs of RFP, EB, CAM, and SM, most patients with good clinical effects showed low MIC for CAM in both periods. Good clinical efficacy, including the sputum conversion rate, was obtained with an increased dose of CAM in the later period. We speculate that the increased dose of CAM influenced the good clinical effect in both periods.

In vitro activity of a new isothiazoloquinolone, ACH-702, against Mycobacterium tuberculosis and other mycobacteria

In this work, we describe the activity of ACH-702 against clinical isolates of Mycobacterium tuberculosis and six different nontuberculous mycobacteria. The MIC(50) and MIC(90) of both susceptible and drug-resistant M. tuberculosis strains tested were 0.0625 and 0.125 microg/ml, respectively. The MIC(50) and MIC(90) values for Mycobacterium fortuitum isolates were 0.0625 microg/ml in both cases; Mycobacterium avium complex isolates showed MIC(50) and MIC(90) values of 0.25 and 4 microg/ml, respectively.

Rifampicin-loaded liposomes for the passive targeting to alveolar macrophages: in vitro and in vivo evaluation

Mycobacterium avium complex (MAC), the most frequent cause of opportunistic nontuberculous pulmonary infection, is made up of a group of intracellular pathogens that are able to survive and multiply inside lung alveolar macrophages. As nebulized liposomes are reported to be effective to target antibacterial agents to macrophages, in this work we have prepared and characterized re-dispersible freeze-dried rifampicin (RFP)-loaded vesicles by using soy lecithin (SL) and a commercial, enriched mixture of soy phosphatidylcholine (Phospholipon 90, P90) with or without cholesterol. The obtained results showed that RFP could be loaded stably in SL vesicles only when cholesterol was not present in the film preparation, whereas with P90 vesicles, the highest stability was obtained with formulations prepared with P90/cholesterol 7:1 or 4:1 molar ratios. RFP-liposome aerosols were generated using an efficient high-output continuous-flow nebulizer, driven by a compressor. After the experiments, nebulization efficiency (NE%) and nebulization efficiency of the encapsulated drug (NEED%) were evaluated. The results of our study indicated that nebulization properties and viscosity of formulations prepared with the low-transition-temperature phospholipids, SL and P90, are affected by vesicle composition. However, all formulations showed a good stability during nebulization and they were able to retain more than 65% of the incorporated drug. The effect of liposome encapsulation on lung levels of RFP following aerosol inhalation was determined in rats. The in vitro intracellular activity of RFP-loaded liposomes against MAC residing in macrophage-like J774 cells was also evaluated. Results indicated that liposomes are able to inhibit the growth of MAC in infected macrophages and to reach the lower airways in rats.

In vitro and in vivo activities of novel fluoroquinolones alone and in combination with clarithromycin against clinically isolated Mycobacterium avium complex strains in Japan

The recommended treatments for Mycobacterium avium complex (MAC) infectious disease are combination regimens of clarithromycin (CLR) or azithromycin with ethambutol and rifamycin. However, these chemotherapy regimens are sometimes unsuccessful. Recently developed antimicrobial agents, such as newer fluoroquinolones (FQs) containing C-8 methoxy quinolone (moxifloxacin [MXF] and gatifloxacin [GAT]), are expected to be novel antimycobacterial agents. Here, we evaluated the in vitro and in vivo antimycobacterial activities of three FQs (MXF, GAT, and levofloxacin) and CLR against clinically isolated MAC strains. Subsequently, the in vitro and in vivo synergic activities of FQ-CLR combinations against MAC strains were investigated. CLR and the individual FQs alone showed promising activity against MAC strains in vitro, and the bacterial counts in organs (lungs, liver, and spleen) of MAC-infected mice treated with single agents were significantly reduced compared to control mice. CLR showed the best anti-MAC effect in vivo. When the three FQs were individually combined with CLR in vitro, mild antagonism was observed for 53 to 57% of the tested isolates. Moreover, mice were infected with MAC strains showing mild antagonism for FQ-CLR combinations in vitro, and the anti-MAC effects of the FQ-CLR combinations were evaluated by counting the viable bacteria in their organs and by histopathological examination after 28 days of treatment. Several FQ-CLR combinations exhibited bacterial counts in organs significantly higher than those in mice treated with CLR alone. Our results indicate that the activity of CLR is occasionally attenuated by combination with an FQ both in vitro and in vivo and that this effect seems to be MAC strain dependent. Careful combination chemotherapy using these agents against MAC infectious disease may be required.

Disseminated Mycobacterium avium infection in young cats: overrepresentation of Abyssinian cats

Disseminated Mycobacterium avium-intracellulare complex (MAC) infection was diagnosed in 10 young cats (1-5 years of age) from Australia or North America between 1995 and 2004. A further two cats with disseminated mycobacteriosis (precise agent not identified) were recognised during this period. Of the 12, 10 were Abyssinian cats, one was a Somali cat and one was a domestic shorthair cat. None of the cats tested positive for either FeLV antigen or FIV antibody. The clinical course of these infections was indolent, with cats typically presenting for weight loss, initially in the face of polyphagia, with a chronicity of up to several months. Additional clinical features included lower respiratory tract signs and peripheral lymphadenomegaly. A marked diffuse interstitial pattern was evident in thoracic radiographs, even in cats without overt respiratory involvement. Hair clipped to perform diagnostic procedures tended to regrow slowly, if at all. Diagnosis was generally made by obtaining representative tissue specimens from mesenteric lymph nodes, liver or kidney at laparotomy, or from a popliteal lymph node. The primary antecedent event was most likely colonisation of either the alimentary or respiratory tract, followed by local invasion and eventual lymphatic and haematogenous dissemination. Nine cases were treated using combination therapy with agents effective for MAC infection in human patients. Two cats are still undergoing initial therapy and have responded. Of the remaining seven, all responded during long courses (5-14 months) of clarithromycin combined with either clofazimine or rifampicin, and a fluoroquinolone or doxycycline. Of these, three cats remain well (with durations between 2 months and 2 years following therapy); two developed recurrent disease (at 3 months and 2 years, respectively, following therapy) and have restarted therapy. The remaining two cats improved 1 year and 5 months, respectively, after diagnosis but ultimately succumbed. The two cats in which therapy was restarted have improved dramatically. Certain lines of Abyssinian and Somali cats likely suffer from a familial immunodeficiency that predisposes them to infection with slow-growing mycobacteria such as MAC.

Relationship between clinical efficacy of treatment of pulmonary Mycobacterium avium complex disease and drug-sensitivity testing of Mycobacterium avium complex isolates

We prospectively investigated the relationship between the clinical efficacy of treatment of pulmonary Mycobacterium avium complex (MAC) disease and drug-sensitivity testing of MAC isolates for antituberculous drugs, new quinolone antibiotics, and clarithromycin (CAM). Fifty-two patients who satisfied the diagnostic criteria of the American Thoracic Society (ATS) and who received treatment between April 1998 and December 2005, using combined therapy of rifampicin (RFP), ethambutol (EB), streptomycin (SM), and CAM, were enrolled in this study. The causative microorganisms isolated were Mycobacterium avium in 30 patients and M. intracellulare in 22 patients. Although separation of the two strains showed drug sensitivity testing to have slightly better minimal inhibitory concentrations (MIC) for M. intracellulare than for M. avium, there were no significant differences in the sputum eradication rate or clinical improvement between the two strains. The MICs of various antibiotics for the isolated MAC strains were as follows: RFP, 0.125-8 microg/ml; CAM, 0.25-16 microg/ml; SM, 2-128< or =microg/ml; EB, 128< or = microg/ml; levofloxacin (LVFX), 1-32 microg/ml; sparfloxacin (SPFX), 0.5-16 microg/ml; and gatifloxacin (GFLX), 0.25-8 microg/ml. The isolated MAC strains showed the same excellent drug sensitivity test results for RFP, new quinolones, and CAM, but they showed resistant drug-sensitivity results for EB and SM. Regarding the relationship between clinical efficacy and the MICs of RFP, EB, CAM, and SM, there was a good relationship only for CAM. Although the ATS has not yet recommended routine drug susceptibility testing of CAM, we believe that drug susceptibility testing of CAM should be performed before the initial treatment is undertaken for pulmonary MAC disease.

Antimycobacterial agents differ with respect to their bacteriostatic versus bactericidal activities in relation to time of exposure, mycobacterial growth phase, and their use in combination

A number of antimycobacterial agents were evaluated with respect to their bacteriostatic activity (growth inhibition) versus the bactericidal activity against a clinical isolate of Mycobacterium avium (Mycobacterium avium complex [MAC] strain 101) in relation to the time of exposure and the growth phase of the mycobacteria. In terms of growth inhibition the MAC in the active phase of growth was susceptible to clarithromycin, ethambutol, rifampin, amikacin, and the quinolones moxifloxacin, ciprofloxacin, and sparfloxacin. In terms of bactericidal activity in relation to the time of exposure these agents differed substantially with respect to the killing rate. An initial high killing capacity at low concentration was observed for amikacin, which in this respect was superior to the other agents. The bactericidal activity of clarithromycin and ethambutol was only seen at relatively high concentrations and increased with time. Killing by rifampin was concentration dependent as well as time dependent. The bactericidal activity of moxifloxacin was marginally dependent on the concentration or the time of exposure. The activity of clarithromycin in combination with ethambutol was not significantly enhanced compared to single-agent exposure. Only an additive effect was observed. The addition of rifampin or moxifloxacin as a third agent only marginally effected increased killing of MAC. However, by addition of amikacin the activity of the clarithromycin-ethambutol combination was significantly improved. The combination of amikacin and amoxicillin-clavulanic acid exhibited synergistic antimycobacterial activity. Towards MAC at low growth rates, only the quinolones exhibited a bactericidal effect.

Usefulness of various antibiotics against Mycobacterium avium-intracellulare, measured by their mutant prevention concentration

This study looked the selection of resistant mutants in Mycobacterium avium-intracellulare during antibiotic treatment. The mutant prevention concentration (MPC) of 20 Mycobacterium avium and 12 Mycobacterium intracellulare isolates was determined. Fifty percent of Mycobacterium avium strains had MPC (MPC50) values lower than 16, 64, 40, 55 and 60 mg/L for rifabutin, rifampicin, ciprofloxacin, levofloxacin and moxifloxacin, respectively. In the case of Mycobacterium intracellulare, 50% had MPC (MPC50) values below 60, 30, 35, 16, 2.5 and 14 mg/L for linezolid, rifabutin, levofloxacin, gatifloxacin, moxifloxacin and clarithromycin, respectively. The high capacity for selecting resistant mutants of all the antibiotics studied emphasises the need to restore the immune system if necessary and to administer combined treatments in order to cure patients.

Activities of sitafloxacin (DU-6859a), either singly or in combination with rifampin, against Mycobacterium ulcerans infection in mice

Efficacy of a new fluoroquinolone, sitafloxacin (DU-6859a), against Mycobacterium ulcerans was evaluated in vivo using the mouse footpad system. The growth of M. ulcerans in mouse footpads was completely inhibited when mice were fed with sitafloxacin at a dose of 25 mg/kg body weight per day; on the other hand similar effects were observed with ofloxacin at a dose of 100 mg/kg body weight per day. In the presence of rifampin, the above dose of sitafloxacin could be reduced by 75% to achieve total inhibition, while, under similar circumstances, the dose of ofloxacin could be reduced by only 50%. Either used singly or in combination with rifampin, the effects of sitafloxacin were bactericidal. The results suggest that sitafloxacin should be evaluated as a chemotherapeutic agent against M. ulcerans infection.

Anti-Mycobacterium tuberculosis activities of new fluoroquinolones in combination with other antituberculous drugs

OBJECTIVES

Studies were undertaken in order to assess the anti- Mycobacterium tuberculosis (MTB) activities of newly developed fluoroquinolones in combination with other antituberculous drugs.

METHODS

A new C-8-methoxyl fluoroquinolone, gatifloxacin (GFLX), and a new C-8-chloro fluoroquinolone, sitafloxacin (STFX), in combination with other drugs were examined for their activities against extracellular growing MTB organisms and those replicating in RAW264.7 macrophages (RAW-M phis s).

RESULTS

STFX but not GFLX potentiated the activities of rifampin and rifalazil against extracellular MTB. Both GFLX and STFX exhibited combined activities against intramacrophage MTB, when used in combination with rifampin, rifalazil, isoniazid, pyrazinamide, ethambutol, streptomycin, or clofazimine.

CONCLUSIONS

Although the observed combined effects varied to some extent from case to case depending on drug combinations, the present findings suggest the usefulness of these new fluoroquinolones in multi-drug regimens for tuberculosis patients.