Promethazine improves antibiotic efficacy and disrupts biofilms of Burkholderia pseudomallei

Efflux pumps are important defense mechanisms against antimicrobial drugs and maintenance of Burkholderia pseudomallei biofilms. This study evaluated the effect of the efflux pump inhibitor promethazine on the structure and antimicrobial susceptibility of B. pseudomallei biofilms. Susceptibility of planktonic cells and biofilms to promethazine alone and combined with antimicrobials was assessed by the broth microdilution test and biofilm metabolic activity was determined with resazurin. The effect of promethazine on 48 h-grown biofilms was also evaluated through confocal and electronic microscopy. The minimum inhibitory concentration (MIC) of promethazine was 780 mg l^-1, while the minimum biofilm elimination concentration (MBEC) was 780-3,120 mg l^-1. Promethazine reduced the MIC values for erythromycin, trimethoprim/sulfamethoxazole, gentamicin and ciprofloxacin and reduced the MBEC values for all tested drugs (p<0.05). Microscopic analyses demonstrated that promethazine altered the biofilm structure of B. pseudomallei, even at subinhibitory concentrations, possibly facilitating antibiotic penetration. Promethazine improves antibiotics efficacy against B. pseudomallei biofilms, by disrupting biofilm structure.

Farnesol increases the susceptibility of Burkholderia pseudomallei biofilm to antimicrobials used to treat melioidosis

AIMS

The aim of this study was to analyse the in vitro activity of farnesol alone and combined with the antibacterial drugs amoxicillin, doxycycline, ceftazidime and sulfamethoxazole-trimethoprim against Burkholderia pseudomallei biofilms.

METHODS AND RESULTS

Susceptibility was assessed by the broth microdilution test and cell viability was read with the oxidation-reduction indicator dye resazurin. The biofilms were evaluated through three microscopic techniques (optical, confocal and electronic microscopy). The minimum biofilm erradication concentration (MBEC) for farnesol was 75-2400 mmol l(-1). In addition, farnesol significantly reduced the MBEC values for ceftazidime, amoxicillin, doxycycline and sulfamethoxazole-trimethoprim by 256, 16, 4 and 4 times respectively (P < 0·05). Optical, confocal and electronic microscopic analyses of farnesol-treated B. pseudomallei biofilms demonstrated that this compound damages biofilm matrix, probably facilitating antimicrobial penetration in the biofilm structure.

CONCLUSIONS

This study demonstrated the effectiveness of farnesol against B. pseudomallei biofilms and its potentiating effect on the activity of antibacterial drugs, in particular ceftazidime, amoxicillin, doxycycline and sulfamethoxazole-trimethoprim.

SIGNIFICANCE AND IMPACT OF THE STUDY

The intrinsic antimicrobial resistance of B. pseudomallei is a serious challenge for the treatment of melioidosis. Thus, this paper reports the inhibitory potential of farnesol against B. pseudomallei biofilms, as well as highlights the favourable pharmacological interaction of farnesol with antibiotics tested, not only on cell viability, but also in the structural morphology of biofilms.

RYP1 gene as a target for molecular diagnosis of histoplasmosis

This study analyzed the RYP1 gene as a target for the molecular diagnosis of histoplasmosis. This assay detected fungal DNA in 13/13 blood samples from HIV/AIDS-patients with histoplasmosis. Therefore, the detection of RYP1 gene in whole blood sample is a quick and sensitive test to diagnose histoplasmosis.

Antiretroviral drugs saquinavir and ritonavir reduce inhibitory concentration values of itraconazole against Histoplasma capsulatum strains in vitro

Recent studies have shown that some drugs that are not routinely used to treat fungal infections have antifungal activity, such as protease inhibitor antiretroviral drugs. This study investigated the in vitro susceptibility of Histoplasma capsulatum var. capsulatum to saquinavir and ritonavir, and its combination with the antifungal itraconazole. The susceptibility assay was performed according to Clinical and Laboratory Standards Institute guidelines. All strains were inhibited by the protease inhibitor antiretroviral drugs. Saquinavir showed minimum inhibitory concentrations ranging from 0.125 to 1μgmL(-1) for both phases, and ritonavir presented minimum inhibitory concentrations ranging from 0.0312 to 4μgmL(-1)and from 0.0625 to 1μgmL(-1) for filamentous and yeast phase, respectively. Concerning the antifungal itraconazole, the minimum inhibitory concentration values ranged from 0.0019 to 0.125μgmL(-1) and from 0.0039 to 0.0312μgmL(-1) for the filamentous and yeast phase, respectively. The combination of saquinavir or ritonavir with itraconazole was synergistic against H. capsulatum, with a significant reduction in the minimum inhibitory concentrations of both drugs against the strains (p<0.05). These data show an important in vitro synergy between protease inhibitors and itraconazole against the fungus H. capsulatum.

Evidence of Fluconazole-Resistant Candida Species in Tortoises and Sea Turtles

The aim of this study was to evaluate the antifungal susceptibility of Candida spp. recovered from tortoises (Chelonoidis spp.) and sea turtles (Chelonia mydas, Caretta caretta, Lepidochelys olivacea, Eretmochelys imbricata). For this purpose, material from the oral cavity and cloaca of 77 animals (60 tortoises and 17 sea turtles) was collected. The collected specimens were seeded on 2% Sabouraud dextrose agar with chloramphenicol, and the identification was carried out by morphological and biochemical methods. Sixty-six isolates were recovered from tortoises, out of which 27 were C. tropicalis, 27 C. famata, 7 C. albicans, 4 C. guilliermondii and 1 C. intermedia, whereas 12 strains were obtained from sea turtles, which were identified as Candida parapsilosis (n = 4), Candida guilliermondii (n = 4), Candida tropicalis (n = 2), Candida albicans (n = 1) and Candida intermedia (n = 1). The minimum inhibitory concentrations for amphotericin B, itraconazole and fluconazole ranged from 0.03125 to 0.5, 0.03125 to >16 and 0.125 to >64, respectively. Overall, 19 azole-resistant strains (14 C. tropicalis and 5 C. albicans) were found. Thus, this study shows that Testudines carry azole-resistant Candida spp.

Virulence and antimicrobial susceptibility of clinical and environmental strains of Aeromonas spp. from northeastern Brazil

The aims of the present study were to isolate and identify clinical and environmental strains of Aeromonas spp. by means of biochemical tests and the automated method VITEK 2 and to investigate the presence of the virulence genes cytotoxic enterotoxin (act), hemolysin (asa-1), and type III secretion system (ascV), and also the in vitro antimicrobial susceptibility of the strains. From the clinical isolates, 19 Aeromonas hydrophila, 3 Aeromonas veronii bv. sobria, and 1 Aeromonas caviae were identified, while from the environmental strains, 11 A. hydrophila, 22 A. veronii bv. sobria, 1 A. veronii bv. veronii, and 1 A. caviae were recovered. The gene act was detected in 69.5% of clinical isolates, asa-1 in 8.6%, and ascV in 34.7%. In the environmental strains, the detection rates were 51.4%, 45.7%, and 54.2% for the genes act, asa-1, and ascV, respectively. Resistance to amoxicillin-clavulanate and piperacillin-tazobactam was observed in 15 and 3 clinical strains, respectively, and resistance to ceftazidime, meropenem, imipenem, ciprofloxacin, and trimethoprim-sulfamethoxazole was observed in 1 strain for each drug. Resistance to amoxicillin-clavulanate and piperacillin-tazobactam was detected in 17 and 1 environmental strain, respectively. Higher resistance percentages were observed in clinical strains, but environmental strains also showed this phenomenon and presented a higher detection rate of virulence genes. Thus, it is important to monitor the antimicrobial susceptibility and pathogenic potential of the environmental isolates.