Tobramycin and Colistin display anti-inflammatory properties in CuFi-1 cystic fibrosis cell line.

Current cystic fibrosis (CF) treatment strategies are primarily focused on oral/inhaled anti-inflammatories and antibiotics, resulting in a considerable treatment burden for CF patients. Therefore, combination treatments consisting of anti-inflammatories with antibiotics could reduce the CF treatment burden. However, there is an imperative need to understand the potential drug-drug interactions of these combination treatments to determine their efficacy. Thus, this study aimed to determine the interactions of the anti-inflammatory agent Ibuprofen with each of the CF-approved inhaled antibiotics (Tobramycin, Colistin and its prodrug colistimethate sodium/Tadim) and anti-bacterial and anti-inflammatory efficacy. Chemical interactions of the Ibuprofen:antibiotic combinations were elucidated using High-Resolution Mass-Spectrometry (HRMS) and 1H NMR. HRMS showed pairing of Ibuprofen and Tobramycin, further confirmed by 1H NMR whilst no pairing was observed for either Ibuprofen:Colistin or Ibuprofen:Tadim combinations. The anti-bacterial activity of the combinations against Pseudomonas aeruginosa showed that neither paired nor non-paired Ibuprofen:antibiotic therapies altered the anti-bacterial activity. The anti-inflammatory efficacy of the combination therapies was next determined at two different concentrations (Low and High) using in vitro models of NuLi-1 (healthy) and CuFi-1 (CF) cell lines. Differential response in the anti-inflammatory efficacy of Ibuprofen:Tobramycin combination was observed between the two concentrations due to changes in the structural conformation of the paired Ibuprofen:Tobramycin complex at High concentration, confirmed by 1H NMR. In contrast, the non-pairing of the Ibuprofen:Colistin and Ibuprofen:Tadim combinations showed a significant decrease in IL-8 secretion at both the concentrations. Importantly, all antibiotics alone showed anti-inflammatory properties, highlighting the inherent anti-inflammatory properties of these antibiotics.

Binary Medical Nanofluids by Combination of Polymeric Eudragit Nanoparticles for Vehiculization of Tobramycin and Resveratrol: Antimicrobial, Hemotoxicity and Protein Corona Studies.

The development of smart nanoparticles (NPs) became a trend to enhance the delivery of drugs. In the present work, Tobramycin (TB), an aminoglycoside antibiotic that displays several undesirable side effects, has been encapsulated into cationic Eudragit®E100 (E100) NPs for the treatment of infections caused by Pseudomonas aeruginosa. Combination with neutral Eudragit®NE30D (NE30D) NPs containing resveratrol (RSV), a strong natural antioxidant, increased the antimicrobial activity of TB (75% higher than free TB). NPs were stabilized with 1.0% (w/v) poloxamer 188 (P188) or poloxamer 407 (P407) as surfactants. E100 NPs showed 83.3 ± 8.5%, and 70.1 ± 2.7 encapsulation efficiency (EE) of TB with P188 and P407 coatings, respectively. The presence of NPs was confirmed by DLS and TEM studies. TB was controlled released from NPs for 6 h. Hemotoxicity tests of NPs in the range of MIC values on human blood gave negative results. Analysis of Surface Plasmon Resonance verified that NE30D/P407/RSV does not interact with plasma proteins BSA, IgG or fibrinogen, besides E100/P188/TB interact with BSA, findings that are compatible with a negligible in vivo clearance of the nanovehicles. The obtained results show a potential binary fluid composed of two NPs to highly improve the effectiveness of conventional antibiotics.

Ebselen attenuates tobramycin-induced ototoxicity in mice.

BACKGROUND: Cystic fibrosis patients are often adminstered tobramycin to treat pulmonary infections. Unfortunately, a common side effect is hearing loss, which can fluctuate. Ebselen has known anti-inflammatory properties and could reduce the incidence and severity of tobramycin-induced hearing loss. METHODS: In vitro: neonatal cochlear cultures were treated with tobramycin or cotreated with tobramycin and ebselen for 3 days. In vivo: adult mice were injected with tobramycin or tobramycin and ebselen for 14 days. ABRs were collected in a repeated measures design until 56 days after treatments. ABR threshold shifts were analyzed and a novel cochleotoxic criteria applied to determine the incidence of ototoxicity. Cochlear immunohistology was analyzed for IHC and OHC loss. RESULTS: Tobramycin leads to significant IHC and OHC loss in cochlear explant cultures. Ebselen co-treatment at 1:20 concentrations resulted in significant otoprotection. Tobramycin leads to significant ABR threshold shifts that are ameliorated by ebselen co-treatment. Hearing loss did not correlate with significant IHC or OHC loss. CONCLUSIONS: This mouse model of tobramycin-induced ototoxicity is clinically relevant in that it results in an incidence and severity of hearing loss recently documented in clinic. The in vitro experiments show that tobramycin kills hair cells and that ebselen co-treatment can attenuate this ototoxicity. The in vivo model shows tobramycin-induced hearing loss is ameliorated by ebselen co-treatment, but this is not explained by concomitant hair cell loss. These preclinical data support the testing of ebselen in CF patients receiving tobramycin treatment.

Comparison of the Anti-Inflammatory and Cytotoxic Potential of Different Corticosteroid Eye Drop Preparations.

PURPOSE: To compare the immunosuppressive and cytotoxic effects of three anti-inflammatory eye drops formulations containing betamethasone plus chloramphenicol (B+C), dexamethasone plus netilmicin (D+N) or dexamethasone plus tobramycin (D+T).Methods: The eye drops formulations have been tested at different dilutions on cytokine synthesis by mouse or human cultured macrophages, as well as proliferation and viability of cultured human corneal cells (HCE).Results: B+C reduced IL6 and TNFα production by cultured mouse or human macrophages more potently than D+N and D+T, with the tree formulations having the same impact on IL-10 expression. We also found that the eye drops preparations reduced proliferation of HCE cells, with D+T showing the higher anti-proliferative potency and B+C showing the lower cytotoxic potential.Conclusion: Our study points out that it may be erroneous to consider routinely-used anti-inflammatory eye drops preparations with analogous formulations as readily interchangeable and of similar potency and tolerability.

Intravenously delivered aminoglycoside antibiotics, tobramycin and amikacin, are not ototoxic in mice.

Many drugs on the World Health Organization's list of critical medicines are ototoxic, destroying sensory hair cells within the ear. These drugs preserve life, but patients can experience side effects including permanent hearing loss and vestibular dysfunction. Aminoglycoside ototoxicity was first recognised 80 years ago. However, no preventative treatments have been developed. In order to develop such treatments, we must identify the factors driving hair cell death. In vivo, studies of cell death are typically conducted using mouse models. However, a robust model of aminoglycoside ototoxicity does not exist. Previous studies testing aminoglycoside delivery via intraperitoneal or subcutaneous injection have produced variable ototoxic effects in the mouse. As a result, surgical drug delivery to the rodent ear is often used to achieve ototoxicity. However, this technique does not accurately model clinical practice. In the clinic, aminoglycosides are administered to humans intravenously (i.v.). However, repeated i.v. delivery has not been reported in the mouse. This study evaluated whether repeated i.v. administration of amikacin or tobramycin would induce hearing loss. Daily i.v. injections over a two-week period were well tolerated and transient low frequency hearing loss was observed in the aminoglycoside treatment groups. However, the hearing changes observed did not mimic the high frequency patterns of hearing loss observed in humans. Our results indicate that the i.v. delivery of tobramycin or amikacin is not an effective technique for inducing ototoxicity in mice. This result is consistent with previously published reports indicating that the mouse cochlea is resistant to systemically delivered aminoglycoside ototoxicity.

Heterodimeric Rifampicin-Tobramycin conjugates break intrinsic resistance of Pseudomonas aeruginosa to doxycycline and chloramphenicol in vitro and in a Galleria mellonella in vivo model.

Intrinsic resistance in Pseudomonas aeruginosa, defined by chromosomally encoded low outer membrane permeability and constitutively over-expressed efflux pumps, is a major reason why the pathogen is refractory to many antibiotics. Herein, we report that heterodimeric rifampicin-tobramycin conjugates break this intrinsic resistance and sensitize multidrug and extensively drug-resistant P. aeruginosa to doxycycline and chloramphenicol in vitro and in vivo. Tetracyclines and chloramphenicol are model compounds for bacteriostatic effects, but when combined with rifampicin-tobramycin adjuvants, their effects became bactericidal at sub MIC levels. Potentiation of tetracyclines correlates with the SAR of this class of drugs and is consistent with outer membrane permeabilization and efflux pump inhibition. Overall, this strategy finds new uses for old drugs and presents an avenue to expand the therapeutic utility of legacy antibiotics to recalcitrant pathogens such as P. aeruginosa.

Vestibulotoxicity in a patient without renal failure after inhaled tobramycin.

Aminoglycoside antibiotics have a long history of use in the control of gram-negative bacterial infections, but their systemic use has been complicated by known ototoxicity and nephrotoxicity. Because of the utility of these medications in patients with frequent pulmonary infections, there has been a move towards the use of inhaled agents, in particular tobramycin, due to a lower rate of systemic complications. Inhaled tobramycin is generally consider to be safe from otologic complications, with only two previous reports of ototoxicity, both in patients who had underlying chronic renal disease. Here we present the first case of a patient developing isolated vestibular toxicity, without associated hearing loss or evidence of renal insufficiency, in a patient receiving inhaled tobramycin. This is an extremely rare complication of an inhaled aminoglycoside and underscores the importance of careful monitoring despite perceived safety.

In vitro approach to study the synergistic effects of tobramycin and clarithromycin against Pseudomonas aeruginosa biofilms using prokaryotic or eukaryotic culture media.

Recurrent Pseudomonas aeruginosa infections involving biofilm formation are frequent in cystic fibrosis, aggravating the respiratory distress. Co-administration of clarithromycin and classical tobramycin could improve the health status of patients. Antibiotic toxicity was assessed on epithelial (CFBE41o(-)) and macrophagic (THP-1) cell lines. Non-toxic concentrations of antibiotics alone or in combination were applied twice daily for 12 days on mature (12-day-old) biofilms of three P. aeruginosa strains, developed either in prokaryotic culture broth [tryptic soy broth (TSB)] or in a eukaryotic cell culture medium (RPMI-FCS) more similar to an in vivo environment. The antibiofilm and bactericidal effects of antibiotics were assessed. No toxicity of tobramycin was observed on eukaryotic cell lines at concentrations up to 500µg/mL, whilst 100µg/mL was selected as the clarithromycin upper safe limit. The amount of biofilm was strongly reduced by 100µg/mL and 500µg/mL tobramycin for each strain in both media, whilst clarithromycin was only effective in RPMI-FBS, with synergistic (PAO1 strain) and additive (PYO2 strain) effects detected when combining tobramycin 4µg/mL and clarithromycin 100µg/mL. Finally, tobramycin at ≥100µg/mL exerted strong bactericidal effects on each strain in both media. Clarithromycin also exerted bactericidal effects on each strain in both media; its effect was weaker than tobramycin in TSB but was similar in RPMI-FBS. Synergistic effects were observed on PAO1 and MUCO biofilms, e.g. when combining tobramycin 4µg/mL and clarithromycin 100µg/mL. These in vitro data show that co-administration of clarithromycin and tobramycin acts synergistically against in vitro P. aeruginosa biofilms.

Interaction of amikacin and tobramycin with melanin in the presence of Cu2+ and Zn2+ ions.

Aminoglycoside antibiotics such as amikacin and tobramycin are the most commonly used treatment against Gram-negative bacterial infections. The widely used aminoglycosides have the unfortunate side-effect of targeting sensory hair cells of the inner ear, so that treatment often results in permanent hair cell loss. Because melanin can act as an antioxidant as well as drug and metal chelator, evidence for its role in protecting the stria and organ of Corti against noise, ototoxins, and aging has long been sought. Protective properties of melanin may derive from its ability to bind cations and metals and to scavenge free radical. The aim of the presented work was to examine the amikacin and tobramycin binding to melanin in the presence of Cu2+ and Zn2+ ions. It has been demonstrated that amikacin and tobramycin form stable complexes with melanin in the presence of metal ions and the amount of aminoglycoside antibiotics bound to melanin increases with the increasing of initial drugs concentration. For amikacin and tobramycin complexes with [melanin-Cu2+] and [melanin-Zn2+] one class of binding sites with the association constant K 10(3)M(-1) has been found. It has been also shown that Cu2+ and Zn2+ ions administered to melanin before complexing with drugs decrease the amount of aminoglycosides bound to melanin, probably by blocking some active centers in the melanin molecule.

Ototoxicity caused by topical administration of gentamicin versus tobramycin in rabbits.

AIM: To investigate the possible differences in cochleotoxic effects in rabbits between twice-daily administration of topical gentamicin and tobramycin throughout the perforated tympanic membrane with the use of distortion-product otoacoustic emissions (DPOAEs). MATERIALS AND METHODS: Twenty female rabbits were studied prospectively daily for 21 days. The rabbits' ears were divided into two groups: right and left ear groups. Twice-daily for 21 days after paracentesis, 0.3% gentamicin was administered topically in the left ears, and 0.3% tobramycin was administered topically in the right ears. For 21 days, the cochlear activity of the right and left ears of all rabbits was examined every 7 days using DPOAEs. The numerical values of the distortion product (DP) intensity recorded on days 7, 14 and 21 of drug administration were compared between the two groups. RESULTS: Cochlear activity was reduced earlier in the gentamicin group in the 2-4kHz frequencies compared to the tobramycin group in the second DPOAE measurement (day 7 of the experiment). In two rabbits in the gentamicin group, the third DPOAE measurement showed that cochlear activity was reduced in all frequencies. In six rabbits in the tobramycin group, the third DPOAE measurement showed that cochlear activity was reduced in all frequencies. There was no statistical significance between the two groups except day 7 in the 2 and 3kHz frequencies (p<0.05). CONCLUSION: We concluded that low frequencies (2 and 3kHz) are more sensitive to the administration of topical gentamicin than to topical tobramycin. Early cessation of tobramycin drops may be minimally cochlear toxic compared to gentamicin within the first 7 days when these drugs are misused in treating chronic otitis media.

Tinnitus onset rates from chemotherapeutic agents and ototoxic antibiotics: results of a large prospective study.

BACKGROUND AND PURPOSE: To report on the incidence and relative risk of tinnitus onset from a variety of drug therapies known to be ototoxic. Two main questions were asked: (1) What is the prevalence and incidence of tinnitus among patients treated with cisplatin, carboplatin, or ototoxic antibiotic therapies? (2) Do commonly reported treatment or subject factors confound or modify the incidence of tinnitus onset? DATA COLLECTION AND ANALYSIS: A prospective observational study design was used to evaluate occurrence of significant otologic changes in 488 veterans (962 ears) receiving chemotherapeutic agents (cisplatin, carboplatin), ototoxic antibiotics (primarily aminoglycoside), or nonototoxic drugs (control medications). A subset of 260 veterans lacking tinnitus prior to drug exposure was used to compare rates of tinnitus onset. Subjects were tested prior to, during, and following their treatment. Planned comparisons using logistic regression, analysis of variance (ANOVA), and chi(2) statistics were made among groups by the type of medication taken, age, presence of preexisting hearing loss, days on drug, and cumulative dose of drug. RESULTS: Baseline tinnitus rates were high (nearly 47%) relative to the general population of a similar age. Subjects with exposure to ototoxic medications had significantly increased risk for developing tinnitus. Those on chemotherapeutic agents were found to have the greatest risk. Cisplatin elevated the risk by 5.53 times while carboplatin increased the risk by 3.75 over nonototoxic control medications. Ototoxic antibiotics resulted in borderline risk (2.81) for new tinnitus. Contrary to other reports, we did not find that subject factors (increased age or pre-existing hearing loss) or treatment factors (days on drug or cumulative dose) contributed to rates of tinnitus onset during treatment. CONCLUSIONS: This large prospective study confirms that new tinnitus during treatment is associated with chemotherapy and with certain ototoxic antibiotic treatment. Cisplatin and carboplatin were found to be the most potent ototoxic agents causing tinnitus at much greater numbers than the other drugs studied. Implications for counseling and audiological resource allocation are discussed.

Interaction between tobramycin and CSA-13 on clinical isolates of Pseudomonas aeruginosa in a model of young and mature biofilms.

The bactericidal activity of a cholic acid antimicrobial derivative, CSA-13, was tested against eight strains of Pseudomonas aeruginosa (both reference and clinical strains) and compared with the response to tobramycin. In planktonic cultures, the minimal inhibitory and minimal bactericidal concentrations of CSA-13 and tobramycin were in the 1-25 mg/L range except for one mucoid clinical strain which was much less sensitive to tobramycin (minimal bactericidal concentration, 65-125 mg/L). In young (24 h) biofilms, the sensitivity to CSA-13 was reduced (half-maximal concentration CSA-13 averaged 88 mg/L) and varied among the eight strains. The sensitivity to tobramycin was also very variable among the strains and some were fully resistant to the aminoglycoside. The combination of tobramycin with CSA-13 was synergistic in five strains. Only one strain showed antagonism between the two drugs at low concentrations of CSA-13. One reference and five clinical strains were tested in mature (12 days) biofilms. The effect of CSA-13 was delayed, some strains requiring 9 days exposure to the drug to observe a bactericidal effect. All the strains were tolerant to tobramycin but the addition of CSA-13 with tobramycin was synergistic in three strains. CSA-13 permeabilized the outer membrane of the bacteria (half-maximal concentration, 4.4 mg/L). At concentrations higher than 20 mg/L, it also permeabilized the plasma membrane of human umbilical vein endothelial cells. In conclusion, CSA-13 has bactericidal activity against P. aeruginosa even in mature biofilms and cationic steroid antibiotics can thus be considered as potential candidates for the treatment of chronic pulmonary infections of patients with cystic fibrosis. Considering its interaction with the plasma membrane of eukaryotic cells, less toxic derivatives of CSA-13 should be developed.

Vestibulotoxicity as a consequence of systemically administered tobramycin in cystic fibrosis patients.

CONCLUSION: The reported prevalence of vestibulotoxicity (30.4%) in cystic fibrosis (CF) patients supports vestibulotoxicity screening in CF patients during or after tobramycin exposure. Prospective longitudinal investigation is required for a more specific evidence-based proposal. OBJECTIVE: To investigate the prevalence of tobramycin-induced vestibulotoxicity in CF patients, as it had not been investigated before. PATIENTS AND METHODS: In this observational cohort study, 23 CF patient volunteers from the Haga Teaching Hospital Adult CF centre who had been exposed to at least one treatment with systemically administered tobramycin were included. Subjective feelings of dizziness were measured using validated questionnaires and vestibular symptoms were assessed by physical examination. Electronystagmography (ENG) with caloric irrigation was used as the gold standard. RESULTS: Peripheral vestibular loss was found in seven patients (7/23 = 30.4%). Central vestibular loss was found in one patient. Analysis of the 19 completed questionnaires showed that 12 patients (12/19 = 63.2%) did not experience dizziness and 3 patients (3/19 = 15/8%) experienced specific vestibular symptoms. The results of the questionnaire could not predict the results of ENG with caloric irrigation. Physical examination showed no abnormalities in any patients. No age- or dose-related predictive factors were found.

Protective effect of edaravone against tobramycin-induced ototoxicity.

CONCLUSION: It is suggested that simultaneous treatment with the radical scavenger edaravone has an effective protective effect against tobramycin ototoxicity in rat. Even if the edaravone treatment is postponed for 7 days, it can still prevent hearing loss, but a 14 day delay cannot protect from ototoxicity. OBJECTIVES: With the aim of alleviating hearing loss caused by aminoglycoside ototoxicity, we performed a trial to assess the hearing protective efficacy of the radical scavenger edaravone. MATERIALS AND METHODS: In part one of the study, 21 male Sprague-Dawley albino rats were used; 2 rats served as controls for the safety of edaravone. Eight rats each received 10 subcutaneous injections (s.c.) of tobramycin (160 mg/kg b.w.) once daily and saline injection intraperitoneally for 2 weeks. Eleven rats were given 10 s.c. tobramycin injections simultaneously with an intraperitoneal injection of edaravone (3 mg/kg b.w.). In part two, tobramycin was injected in 13 rats (as above). Five of these received two edaravone injections 7 days later and four rats similarly 14 days later. Auditory brainstem response (ABR) was used to assess hearing. RESULTS: All rats treated only with tobramycin showed a deterioration of hearing. None of the rats given simultaneous treatment with tobramycin and edaravone demonstrated hearing loss. A 7 day delay in edaravone injection still prevented hearing loss, but a 14 day delay had only a temporary prophylactic effect.

Experimental study of a new vascular graft prebonded with antibiotic: healing, toxicity, and antibiotic retention.

Despite refinements in surgical techniques, routine antibioprophylaxis, and anesthesiology, vascular prosthetic infections remain a serious complication of reconstructive vascular surgery. The purpose of this study was to evaluate the healing, the toxicity, and the antibiotic delivery of a new vascular graft, preloaded with rifampin and tobramycin. Sixteen dogs underwent infrarenal aortic bypass. They were divided into three groups. In test group 1 (n = 8), dogs received grafts loaded with a standard concentration of antibiotics. In test group 2 (n = 4), dogs received grafts loaded with twice the standard concentration of antibiotics. A control group (n = 4) received a commercial gelatin-sealed graft. Grafts were harvested after different periods of time and submitted to histological evaluation and antibiotic dose determination. Liver and kidney toxicities were evaluated from dosages performed on serum samples taken at different time periods between graft implantation and harvesting. The healing of antibiotic-loaded grafts was similar to that of commercial grafts, without any signs of toxicity. These results suggest resistance to infection of these prebonded grafts in an animal model.

Antibiotics for local delivery systems cause skeletal cell toxicity in vitro.

Antibiotic concentrations associated with antibiotic bone cements may cause skeletal cell toxicity and prevent fracture healing. We investigated toxicity effects of dose and treatment time after exposure to three antibiotics commonly used in orthopaedic local drug delivery systems. We hypothesized a threshold exists for toxicity of osteoblasts and chondrocytes after treatment with ciprofloxacin, vancomycin, or tobramycin. To test this hypothesis, we first determined whether treatment with antibiotics caused differences in cellular morphology. Cells exposed to ciprofloxacin showed considerable changes in spread, cell membrane, and extensions. We next asked what dosage of antibiotic would cause reductions in osteoblast and chondrocyte cell numbers. Ciprofloxacin at a dose greater than 100 microg/mL and vancomycin and tobramycin at doses greater than 2000 microg/mL severely decreased cellular proliferation. Finally, we questioned whether observed decreases in cell numbers were the result of increased cellular toxicity or senescence. Released lactate dehydrogenase ratios were severely increased in osteoblasts. These data suggest the balance between the targeted microbicidal effects and host cellular toxicity is critical for skeletal cell survival and function.

Population pharmacokinetics of tobramycin administered thrice daily and once daily in children and adults with cystic fibrosis.

BACKGROUND: Tobramycin pharmacokinetics have not been evaluated previously in a large series of data collected in children and adults with CF receiving once (OD) or three times daily (TD) tobramycin. METHODS: Therapeutic drug monitoring data in children and adults with CF who participated in a randomised clinical trial evaluating efficacy and toxicity of OD versus TD tobramycin (TOPIC study) were analysed retrospectively. Population pharmacokinetic models stratified to treatment schedule were created, and individual pharmacokinetic parameters were calculated. RESULTS: In paediatric patients, volume of distribution per kg body weight (V1) was greater with OD treatment compared to TD (0.401+/-0.092 versus 0.354+/-0.041, p=0.003). Elimination rate was reduced in all patients receiving OD tobramycin compared to TD (children: 0.00197+/-0.00027 versus 0.00291+/-0.00041, p<0.001, adults: 0.00252+/-0.00008 versus 0.00322+/-0.00050, p<0.001). Tobramycin V1 decreased with increasing age (R(2)=0.3, p<0.001). CONCLUSIONS: The reduced elimination rate in OD may either be caused by circadian pharmacokinetic behaviour of tobramycin or indicates early renal damage caused by high tobramycin doses not detected by biochemical measurements. However, results of our previous work suggest that OD tobramycin may be less nephrotoxic. The higher V1 in children implies that a relative higher tobramycin dose in these patients is needed for the same target peak serum concentration.

Antibiotics as intermicrobial signaling agents instead of weapons.

It has been widely assumed that the ecological function of antibiotics in nature is fighting against competitors. This made them a good example of the Darwinian struggle-for-life in the microbial world. Based on this idea, it also has been believed that antibiotics, even at subinhibitory concentrations, reduce virulence of bacterial pathogens. Herein, using a combination of genomic and functional assays, we demonstrate that specific antibiotics (namely tobramycin, tetracycline, and norfloxacin) at subinhibitory concentrations trigger expression of determinants influencing the virulence of the major opportunistic bacterial pathogen Pseudomonas aeruginosa. All three antibiotics induce biofilm formation; tobramycin increases bacterial motility, and tetracycline triggers expression of P. aeruginosa type III secretion system and consequently bacterial cytotoxicity. Besides their relevance in the infection process, those determinants are relevant for the ecological behavior of this bacterial species in natural, nonclinical environments, either by favoring colonization of surfaces (biofilm, motility) or for fighting against eukaryotic predators (cytotoxicity). Our results support the notion that antibiotics are not only bacterial weapons for fighting competitors but also signaling molecules that may regulate the homeostasis of microbial communities. At low concentrations, they can even be beneficial for the behavior of susceptible bacteria in natural environments. This is a complete change on our vision on the ecological function of antibiotics with clear implications both for the treatment of infectious diseases and for the understanding of the microbial relationships in the biosphere.

Ototoxicidade, otoproteção e autodefesa das células ciliadas da cóclea / Ototoxycity, otoprotection and self defense of the coclear outer hair cells

Ototoxicoses são afecções provocadas por drogas medicamentosas de forma iatrogênica, comprometendo a função auditiva e/ou do sistema vestibular periférico. São caracterizadas por uma perda auditiva neurossensorial de mais de 25 dB em uma ou mais freqüências na faixa de 250 a 8000 Hz, com ou sem manifestações de vertigem ou desequilíbrio. Dentre as drogas ototóxicas as mais estudadas são os antibióticos aminoglicosídeos e antineoplásicos como a cisplatina que é largamente utilizada para o tratamento do câncer, tanto em adultos quanto em crianças. Estudos têm tentado identificar drogas que, associadas aos ototóxicos possam atuar como otoprotetores. Sabe-se que o mecanismo da ototoxicidade de aminoglicosídeos e da cisplatina está relacionado a alterações nos mecanismos antioxidantes das células ciliadas, principalmente as células ciliadas externas da cóclea. Além disso, existem relatos do fenômeno de autodefesa das células ciliadas externas a aminoglicosídeos e a cisplatina.

Effect of aminoglycoside otic drops on isolated cochlear outer hair cells with and without liver extract activation.

OBJECTIVE: To assess the ototoxicity of commercially available Gentacidin and TobraDex ear drops with and without liver extract activation using isolated cochlear outer hair cells (OHCs). MATERIAL AND METHODS: OHCs from adult chinchilla cochleae were exposed to standard bathing solution (SBS), liver extract alone and Gentacidin and TobraDex ear drops with and without liver extract. All experiments were performed at an osmolality of 305 +/-5 mOsm, at room temperature and for up to 60 min. OHC images were recorded using an inverted microscope and analyzed electronically. Time to cell death and changes in cell length were measured. RESULTS: The time to cell death and the percent change in cell length were significantly shorter in the Gentacidin+liver extract group than in the Gentacidin alone group (p < 0.05). The TobraDex+liver extract group showed a significantly decreased time to cell death compared to the SBS control group (p < 0.05). There were no significant differences in cell length or time to cell death between the TobraDex+liver extract group and the TobraDex alone group (p > 0.05). CONCLUSION: This study suggests that the cytotoxicity of aminoglycoside ear drops to isolated OHCs in vitro requires