Clinical recovery and limited cure in canine visceral leishmaniasis treated with aminosidine (paromomycin)

Three groups of three, six, and 12 dogs with parasitologically proven clinical visceral leishmaniasis (Leishmania chagasi infection) were treated with intramuscular aminosidine sulfate at doses of 20 mg/kg/day for 15 days; 80 mg/kg/day for 20 days, and 40 mg/kg/day for 30 days, respectively. Follow-up was by parasitologic examination of bone marrow and skin, serology using the indirect immunofluorescent antibody test, and clinical examination for signs of visceral leishmaniasis or adverse effects of treatment. In animals treated with 20 mg/kg/day, for 15 days, there was dramatic clinical improvement with disappearance of conjunctivitis, increase in appetite, weight gain, and recovery of normal skin condition and a healthy coat, but parasitologic relapse occurred between 50 and 100 days after initiation of treatment. Adverse effects were seen with treatment with 80 mg/kg/day for 20 days; three dogs died during or just after treatment, two showed temporary recovery, and one showed total clinical and parasitologic cure that was maintained for four years. Although adverse effects and relapses were seen in some dogs treated with 40 mg/kg/day for 30 days, three of 12 dogs showed complete parasitologic and clinical cure that was sustained for at least four years. Aminosidine treatment cannot be recommended as an alternative to the humane destruction of dogs for the control of canine visceral leishmaniasis because ineffective treatment may prolong carrier status or encourage development of drug resistance. This drug may be a therapeutic option if there is no danger of a dog acting as a reservoir of infection. Achievement of clinical recovery and limited cure with aminosidine suggests that further trials would be of value, possibly in combination with other anti-leishmanial drugs and with supportive measures to reduce adverse effects.

Visceral leishmaniasis in Teresina, State of Piauí, Brazil: preliminary observations on the detection and transmissibility of canine and sandfly infections

A Leishmania donovani-complex specific DNA probe was used to confirm the widespread dissemination of amastigotes in apparently normal skin of dogs with canine visceral leishmaniasis. When Lutzomyia longipalpis were fed on abnormal skin of five naturally infected dogs 57 of 163 (35%) flies became infected: four of 65 flies (6%) became infected when fed on apparently normal skin. The bite of a single sandfly that had fed seven days previously on a naturally infected dog transmitted the infection to a young dog from a non-endemic area. Within 22 days a lesion had developed at the site of the infective bite (inner ear): 98 days after infection organisms had not disseminated throughout the skin, bone marrow, spleen or liver and the animal was still serologically negative by indirect immunofluorescence and dot-enzyme-linked immunosorbent assay. When fed Lu. longipalpis were captured from a kennel with a sick dog known to be infected, 33 out of 49 (67%) of flies contained promastigotes. In contrast only two infections were detected among more than 200 sandflies captured in houses. These observations confirm the ease of transmissibility of L. chagasi from dog to sandfly to dog in Teresina. It is likely that canine VL is the major source of human VL by the transmission route dog-sandfly-human. The Lmet2 DNA probe was a useful epidemiological tool for detecting L. chagasi in sandflies.

Antimicrobial and Antibiofilm Activity of Lys-[Trp6]hy-a1 Combined with Ciprofloxacin Against Gram-Negative Bacteria

Background:

Ciprofloxacin (Cip) is the most commonly used quinolone in clinical practice; however large-scale use has favored the increase of multiresistant pathogenic microorganisms. Antimicrobial peptides (AMPs) appear to be a promising alternative in potentiating these conventional drugs.

Objective:

The aim of this study was to evaluate the effect of the peptide Lys-[Trp6]hy-a1 (lys-a1) on the antimicrobial and antibiofilm activity of ciprofloxacin against clinically relevant gram-negative bacteria.

Methods:

The antimicrobial effects of Cip and lys-a1 were assessed by determining the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). The synergistic action of Cip and lys-a1 was determined by checkerboard assay. The time-kill curve was constructed for the Cip/lys-a1 combination against Pseudomonas aeruginosa ATCC 9027. The antibiofilm activity of this combination was analyzed by crystal violet, colony-forming unit count and atomic force microscopy (AFM).

Results:

The data demonstrated that lys-a1 was able to inhibit planktonic growth of strains of P. aeruginosa and Klebsiella pneumoniae both at 125 μg/mL. The fractional inhibitory concentration index (FICi) showed a synergistic effect between Cip and lys-a1 against P. aeruginosa, decreasing the MICs of the individual antimicrobial agents by 4- and 8-fold, respectively. This effect was also observed for the death kinetics and antibiofilm activity. Analysis of the early biofilms (6 h) as well as isolated cells by AFM images evidenced the cell perturbation caused by Cip/lys-a1 treatment.

Conclusion:

These data suggest that lys-a1 has biotechnological potential as a therapeutic tool for the treatment of infections caused by clinically relevant microorganisms, especially P. aeruginosa.

Anti-Staphylococcal Activity of Cinnamomum zeylanicum Essential Oil against Planktonic and Biofilm Cells Isolated from Canine Otological Infections

The aim of this study was to evaluate the phytochemical profile of Cinnamomum zeylanicum essential oil (CZEO) and their antimicrobial and antibiofilm activity against Staphylococcus strains isolated from canine otitis. First, the CZEO chemical composition was determined by gas chromatography-mass spectrometry (CG-MS). External otitis samples collected from dogs were submitted to staphylococcal isolation, followed by MALDI-TOF mass spectrometry identification. The antimicrobial action was tested against the isolates using the disk-diffusion and microdilution methods. The antibiofilm activity was evaluated by CZEO-based concentrations, subMIC for biofilm formation and supraMIC against preformed biofilm, quantified by crystal violet (CV) staining and CFU counting. The chemical analysis revealed that (E)-cinnamaldehyde, eugenol and (E)-cinnamyl acetate were the main compounds in the CZEO, representing 77.42, 8.17 and 4.50%, respectively. Two strains of three different species, S. saprophyticus, S. schleiferi and S. pseudintermedius, were identified. The disk-diffusion test showed an inhibitory zone diameter, ranging from 34.0 to 49.5 mm, while the MIC and MBC values were around 500 and 1000 µg/mL. SubMIC demonstrated an inhibition on biofilm formation against 4 out the 6 strains tested. On mature biofilm, the CZEO-based supraMIC groups had slightly change on biomass, however, the biofilm cell viability decreased the CFU in 3 magnitude orders.

Enhancement of chlorhexidine activity against planktonic and biofilm forms of oral streptococci by two Croton spp. essential oils from the Caatinga biome

This work investigates the ability of two Croton spp. essential oils (EO) to enhance chlorhexidine (CHX) activity against oral streptococci. EO's chemical composition of Croton argyrophyllus and C. pluriglandulosus was determined by GC-MS/FID. The microbial growth kinetics and minimum inhibitory concentration (MIC) of EOs and CHX were determined, followed by their synergism against S. mutans UA159 and ATCC 25175, S. salivarius ATCC 7073 and S. sp. ATCC 15300. The microplate-based method was used to determine the EO/CHX activity against 24-h-old biofilms. The major compounds were α-pinene (54.74%) and bicyclogermacrene (16.08%) for EOAr and 1,8-cineole (17.41%), methyleugenol (16.06%) and elemicin (15.99%) for EOPg. Both EO had MIC around 16,000 µg/mL. EOs/CHX presented a synergistic effect against most strains (FICi from 0.133 to 0.375), and OE/CHX-treated biofilms showed a reduction in biomass and cell viability compared to CHX, only (p < 0.01). Thus, the EOs works as natural adjuvants for CHX.

Preliminary observations on the diagnosis and transmissibility of canine visceral leishmaniasis in Teresina, n.e. Brazil

A pilot group of 49 dogs and control groups from non-endemic areas were examined serologically for the presence of visceral leishmaniasis (VL) by direct agglutination test (DAT), indirect immunofluorescence (IFAT) enzyme-linked immunosorbent assay (ELISA) and DOT-ELISA. Results indicated that DAT is less sensitive than the other assays and that serology with filter paper blood samples is less sensitive than with serum. Promastigote infections were common in fed Lutzomyia longipalpis taken from a dog kennel inhabited by a dog carrying Leishmania chagasi. Colony-bred Lu. longipalpis readily acquired L. chagasi infection when fed on skin lesions of dogs naturally infected with L. chagasi: a small proportion of flies also became infected when fed on apparently normal skin. Widespread distribution of amastigotes in normal skin of asymptomatic animals was shown both by intensive microscopy and by probing skin biopsy samples with the Lmet2 L. donovani-complex specific DNA probe. It was demonstrated that an immunologically naive dog could be infected by a single experimentally infected sand fly. Abundant amastigotes present within the resultant lesion 22 days later were transmissible to sand flies but serology remained negative at least 45 days after the infective bite. Experimental transmission of canine VL by sand fly bite is a valuable approach for determining which diagnostic procedures are most sensitive, specific and suitable for field application in suburban households.

Effect of Lactobacillus spp. cell-free supernatant against planktonic growth and biofilm formation of foodborne Escherichia coli isolates

The aim of this work was to evaluate the anti-Escherichia coli effect of cell-free supernatant (CFS) of Lactobacillus spp. against planktonic and biofilm forms of foodborne isolates. Escherichiacoli strains (P12, P25, P35 and P36), previously isolated from fresh filets of fish, were subjected to antimicrobial susceptibility determination by the disc-diffusion agar method. Subsequently, the antagonistic effect between probiotic and pathogenic strains was determined by spot overlay assay. Finally, the CFS activity against pre-established (12 h) biofilms was demonstrated through biomass quantification by crystal violet staining and scanning electron microscopy (SEM). All isolates presented some pattern of resistance, primarily to ampicillin and tetracycline. Probiotic strains presented high antagonistic effects against all E. coli strains, presenting inhibition zones (R) ranging from 15.60 to 20.67 mm. Additionally, the residual biomass of pre-established (12 h) biofilm was drastically reduced about 50% after CFS treatment (P < 0.01). What can be noted by SEM images, which show less surface-attached cells of CFS-treated biofilms of E. coli (P12). Thus, cell-free preparations produced from Lactobacillus spp. may represent a tool in the battle against planktonic cells and biofilm forms of antibiotic-resistant E. coli.

K-aurein: A notable aurein 1.2-derived peptide that modulates Candida albicans filamentation and reduces biofilm biomass

Candida albicans is considered one of the most important opportunistic fungi due to the large arsenal of virulence factors that help throughout the progress of the infection. In this sense, antimicrobial peptides (AMPs) appear as an alternative, with great antifungal action. Among these, aurein 1.2 has been widely explored, becoming the basis for the discovery of new AMPs, such as K-aurein (K-au). Thus, this study evaluated the anti-C. albicans potential of K-au against virulence factors, planktonic growth, and biofilm formation of clinical isolates. Firstly, K-au antifungal activity was determined by the microdilution method and time-kill curve. The inhibition of hydrolytic enzyme secretion (proteinase, phospholipase, and hemolysin) and germ tube formation was tested. Then, the antibiofilm potential of K-au was verified through biomass quantification and scanning electron microscopy (SEM). All tests were compared with the classical antifungal drug, amphotericin B (AmB). The outcomes showed fungicidal action of K-au at 62.50 µg mL-1 for all isolates, with a time of action around 150-180 min, determined by the time-kill curve. K-au-treated cells decreased by around 40% of the germinative tube compared to the control. Additionally, K-au inhibited the biofilm formation by more than 90% compared to AmB and the control group. SEM images show apparent cellular disaggregation without the formation of filamentous structures. Therefore, the findings suggest a promising anti-C. albicans effect of K-au due to its fungicidal activity against planktonic cells, or its ability to inhibit important virulence factors like germ tube and biofilm formation. Thus, this peptide could be explored as a useful compound against C. albicans-related infection.

Anxiolytic and Anticonvulsant Potential of Biosynthetic Limonene Derivatives in Adult Zebrafish

This study investigated the anxiolytic and anticonvulsant effects and safety profile of limonene enantiomers and their oxidized derivatives. The toxicity test was performed by monitoring the animals for 96 hours, with no deaths or significant toxicity observed up to the highest dose, which allowed the determination of the LD50. Doses of 4, 20 and 40 mg/kg were tested, with no toxicity observed up to 96 h (LD50>40 mg/kg). Anxiolytic activity was measured in a preference test for light and dark areas, and the effect of the compounds was evaluated in the presence of serotonergic antagonists. The (S)-(-)-LIM and (R)-(+)-LIM enantiomers showed anxiolytic effects, with (S)-(-)-LIM being effective at all doses. In the anticonvulsant test, the oxidized derivatives, such as perilyl acid (PAC), significantly delayed PTZ-induced seizures, an effect blocked by flumazenil (FMZ). The oxidized derivatives, especially perilyl acid (PAC), showed anxiolytic effects at all doses and significantly delayed the three PTZ-induced seizure events. This effect was blocked by FMZ, suggesting a relationship between PAC and the GABAergic pathway. PAC, being the most oxidized derivative, was the most effective for both anxiety and delaying seizure progression, suggesting that oxidation of limonene compounds may increase their therapeutic efficacy.