Antibacterial efficacy and drug-induced tooth discolouration of antibiotic combinations for endodontic regenerative procedures.

Elimination of microbial contamination from the root canal system is a precondition for successful root canal treatment. Teeth with immature root development, necrotic pulps and apical periodontitis present multiple challenges for successful treatment. Disinfection is achieved by irrigation followed by the placement of an intracanal medicament. A mixture of ciprofloxacin, metronidazole and minocycline (3-MIX S) has been shown to be very effective in eliminating endodontic pathogens in vitro and in vivo. Among the components of the mixture, minocycline can induce tooth discolouration after long-term oral use. Therefore, the elimination of minocycline from the above-mentioned combination has been suggested to prevent the occasion of this undesirable effect. The aim of this study was to investigate the potential antimicrobial efficacy of alternative antibiotic combinations [3-MIX C (clarithromycin); 3-MIX F (fosfomycin)] against bacteria from infected root canals. An additional objective was to evaluate their discolouration potential as possible alternatives to minocycline-based intracanal medicaments. Our in vitro results clearly demonstrated that 3-MIX C and 3-MIX F had a greater antimicrobial activity than 3-MIX S, underlying that clarithromycin still had a higher capacity to kill endodontic pathogens in vitro compared to fosfomycin. Both 3-MIX C and 3-MIX F were able to avoid the permanent staining effect of the crown.

Antimicrobial efficacy of cryotreatment against Enterococcus faecalis in root canals.

The purpose of this investigation was to evaluate intracanal bacterial reduction by cryotreatment using a dental instrument equipped with a duct and connected to a cryogenic fluid source. A total of 86 roots were infected with Enterococcus faecalis and incubated. After incubation, the contaminated roots were divided into three study groups: 35 roots irrigated with 2 ml of a 5% sodium hypochlorite (NaOCl) solution, 35 roots irrigated with 2 ml of a 5% NaOCl solution and further treated with cryo and 10 roots irrigated with 2 ml of saline solution, plus positive and negative controls. Subsequent to each irrigation treatment, the residual bacterial colonies were counted. The use of cryo-instrumentation in association with NaOCl irrigation significantly reduced the number of Ent. faecalis (P < 0·01) in the root canal compared with controls. The interesting potential of cryotreatment should be further investigated through clinical studies aimed to establish a correct irrigation protocol. Within the limits of the study, the cryotreatment seems to have a greater effect on the reduction in bacteria compared to a standard NaOCl irrigation.

Faecal microbiota in breast-fed infants after antibiotic therapy.

AIM: To evaluate modifications of gut microbiota after antibiotic therapy in breast-fed infants. STUDY DESIGN: Twenty-six exclusively breast-fed infants younger than 5 months hospitalized for pneumonia treated with ceftriaxone (50 mg per kilo per day administered intramuscularly) were recruited. Intestinal microbiota at day 0 - before starting antibiotic administration - at the end of the therapy (5 days after) and after 15 days after the stop was analysed. Stool samples were collected and immediately diluted and cultured on selective media to detect total bacteria, Enterobacteriaceae, enterococci and lactobacilli. Statistical analysis was performed by using Wilcoxon test. RESULTS: After 5 days of antibiotic therapy, we observed a significant reduction in total faecal bacterial count (p = 0.003) in Enterobacteriaceae (p = 0.001) and enterococci (p < 0.001), in comparison with day 0. After 5 days of therapy, lactobacilli are no longer detected. Conversely, bacterial count values for all bacteria detected after 15 days from the end of therapy are significantly increased and similar to day 0. CONCLUSION: Our findings showed that gut microbiota was significantly modified after 5 days of antibiotic therapy; exclusively, breast-feeding may be relevant in promoting the re-establishment of gut microbiota composition in early infancy.

The erythromycin-resistance in S. pyogenes does not limit the human polymorphonuclear cell antimicrobial activity.

In order to highlight the potential erythromycin immunomodulatory properties related to different antibiotic resistance patterns in Streptococcus spp., we evaluated the influence of the macrolide on the PMNs primary functions against erythromycin-susceptible (Ery-S) and erythromycin-resistant (Ery-R) S. pyogenes strains. A total of 438 S. pyogenes were isolated over the period 2005-2007. On the basis of the triple disk testing, 345 out of 438 S. pyogenes isolates were Ery-S and 93 were Ery-R; among the resistant strains, 65 displayed the cMLSB phenotype, 23 had the M phenotype and 5 had iMLSB phenotype. Concerning antibacterial activity of PMNs, our results showed that erythromycin did not modify bacterial uptake, but significantly increased the phagocyte intracellular killing, compared with controls, for both Ery-S and Ery-R strains. Consequently, this report underlines that in immunocompetent hosts the dichotomy between the in vitro resistance and clinical trial data for antimicrobial agents should be thoroughly re-evaluated.

Role of fosfomycin tromethamine in modulating non-specific defence mechanisms in chronic uremic patients towards ESBL-producing Escherichia coli.

Antimicrobial agents and polymorphonuclear cells (PMNs) have the potential to interact in such a way that improve the therapy for infectious diseases. In immunocompromised patients highly susceptible to microbial infections with high morbidity and mortality, several metabolic and functional alterations in PMNs, mostly related to microbicidal activity, are observed. Therefore, the antibiotic of choice should have a good antimicrobial effect without impairing host defences. The aim of this study is to evaluate in vitro effects of sub-inhibiting fosfomycin tromethamine (FT) concentrations on the primary functions of PMNs from healthy subjects and immunocompromised patients (haemodialysed and renal transplant recipients), against an ESBL-producing Escherichia coli, the most common aetiological agent in urinary tract infections (UTIs). FT is considered a first line drug in the eradication of UTIs due to its appropriate antimicrobial spectrum, oral bioavailability and minimal risk of microbial resistance. Our results provide evidence that FT is able to induce enhancement of the depressed phagocytic response of PMNs from patients on chronic haemodialysis and from renal transplant recipients, restoring their primary functions in vitro against ESBL-producing E. coli. All these data permit the conclusion that uremic-infected patients might additionally benefit from the immunomodulating properties of FT.

In vitro compared activity of telithromycin and azithromycin against northwest Italian isolates of Streptococcus pyogenes and Streptococcus pneumoniae with different erythromycin susceptibility.

AIMS: This study compared the in vitro activity of telithromycin with that of azithromycin against 438 Streptococcus pyogenes and 198 Streptococcus pneumoniae, isolated over the period 2005-2007 from specimens of different human origin obtained in three Piemonte Region's hospitals. METHODS AND RESULTS: The determination of antimicrobial activity was evaluated by the microdilution broth method and the erythromycin-resistant (Ery-R) phenotypes by the triple-disc test. Exactly 78.8% of S. pyogenes and 69.2% of S. pneumoniae were erythromycin-susceptible (Ery-S). Concerning S. pyogenes, telithromycin was active against M and inducible MLS(B), subtype-C, phenotypes but not against constitutive MLS(B) strains. Telithromycin acted well against all S. pneumoniae, irrespective of their mechanism of macrolide-resistance. On the contrary, the Ery-R isolates, both S. pyogenes and S. pneumoniae, were resistant to azithromycin. CONCLUSIONS: Our results indicate that macrolide resistance in streptococci still persist in northwest Italy (21.2% of S. pyogenes and 308% of S. pneumoniae) and that telithromycin is confirmed as being extremely active even against recent clinical Ery-R streptococcal isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study emphasizes that an active surveillance of the phenotype distribution and antibacterial resistance in streptococci is essential in guiding the effective use of empirical treatment option for streptococcal infections, also at regional level.

Antifungal activity of essential oils against filamentous fungi determined by broth microdilution and vapour contact methods.

AIMS: The in vitro activity of some essential oils (EO) (thyme red, fennel, clove, pine, sage, lemon balm and lavender) against clinical and environmental fungal strains was determined. METHODS AND RESULTS: The minimal inhibitory concentrations were determined by a microdilution method in RPMI 1640 and by a vapour contact assay. The composition of oils was analysed by gas chromatography (GC) and GC/mass spectrometry. The results indicated that the oils antifungal activity depended on the experimental assay used. The inhibiting effects of EO in vapour phase were generally higher than those in liquid state. According to both methods thyme red and clove were found to be the oils with the widest spectrum of activity against all fungi tested. CONCLUSIONS: Despite the differences between the two methods, our results demonstrate that some EO are very active on dermatophytes and dematiaceous fungi. However, more data will be necessary to confirm this good in vitro efficacy. SIGNIFICANCE AND IMPACT OF THE STUDY: This study could identify candidates of EO for developing alternative methods to control environmental and clinically undesirable filamentous fungi.

Improvement of clinical response in allergic rhinitis patients treated with an oral immunostimulating bacterial lysate: in vivo immunological effects.

Allergic rhinitis is known to be one of the most common chronic diseases in the industrialized world. According to the concept that allergic rhinitis patients generally suffer from an immune deficit, in order to stimulate specifically or aspecifically their immune system, immunomodulating agents from various sources, such as synthetic compounds, tissue extracts or a mixture of bacterial extracts, have been used. The aim of the present trial is to evaluate the efficacy of the treatment with an immunostimulating vaccine consisting of a polyvalent mechanical bacterial lysate (PMBL) in the prophylaxis of allergic rhinitis and subsequently to analyze its in vivo effects on immune responses. 41 allergic rhinitis patients were enrolled: 26 patients were randomly assigned to the group for PMBL sublingual treatment and 15 others to the group for placebo treatment. For all 26 patients blood samples were drawn just before (T0) and after 3 months of PMBL treatment (T3) to evaluate plasma IgE levels (total and allergen-specific) and the cytokine production involved in the allergic response (IL-4, IFN-gamma). The results of our study indicate that PMBL is effective in vivo in the reduction or in the elimination of the symptoms in rhinitis subjects during the treatment period in comparison to a non-immunostimulating treatment. A significant and clinically relevant improvement was found in 61.5%, a stationary clinical response was registered in 38.4% and no negative side effects associated with the medication or worsening were recorded. At the end of a 3-month follow up period the clinical picture remained the same as that observed at T3. PMBL treatment did not affect the serum IgE levels (either total or allergen-specific) and did not induce significant changes in IFN-gamma concentration. In contrast, PMBL therapy may be accompanied, in some patients, by a potential immunomodulating activity by decreasing IL-4 cytokine expression.

Clarithromycin mediated the expression of polymorphonuclear granulocyte response against streptococcus pneumoniae strains with different patterns of susceptibility and resistance to penicillin and clarithromycin.

There is an urgent need for antibiotics that can be used in the therapy of infections caused by penicillin-resistant Streptococcus pneumoniae, the incidence of which is often associated with considerable morbidity and mortality. Antibiotics that can interact positively with the immune response and that also possess microbicidal properties might significantly contribute to improving the outcome of S. pneumoniae infections. Therefore, in the present study we investigated the effect of clarithromycin, an extended spectrum macrolide currently used in the treatment of respiratory tract infections, on the in vitro interaction between human polymorphonuclear granulocytes (PMN) and three strains of S. pneumoniae with different susceptibility or resistance patterns to both penicillin and clarithromycin. At a concentration of one-half the minimal inhibitory concentration (MIC), clarithromycin significantly enhanced human PMN functions, particularly intracellular bactericidal activity, against all the S. pneumoniae strains, including resistant ones. This finding may help to explain clarithromycin activity in vivo despite apparent resistance in vitro. Preexposure of PMNs to one-half the MIC of clarithromycin had no effect on either phagocytosis or intracellular killing, ruling out a direct antibiotic action on PMNs. Preexposure of streptococci to clarithromycin increased the susceptibility of S. pneumoniae to the bactericidal mechanisms of human PMNs compared with untreated bacteria, indicating that this macrolide may partly reduce bacterial virulence via changes in S. pneumoniae.

Impact of co-amoxiclav on polymorphonuclear granulocytes from chronic hemodialysis patients.

Phagocyte-dependent host defenses are frequently impaired in maintenance hemodialysis patients who show an increased susceptibility to infections. In these individuals, the course of infections can be more aggressive than in normal hosts, and the antibiotic of choice should have a high antimicrobial effect without impairing host defenses. Hence, in uremic patients, the antibiotic enhancement of phagocyte functions may be of potential clinical importance in the outcome of bacterial infections. Because we demonstrated previously that co-amoxiclav had beneficial properties that result in enhancement of the microbicidal functions of human polymorphonuclear cells (PMNs) from healthy subjects, we investigated the influence of this combination on the activities of PMNs from chronic hemodialysis patients against Klebsiella pneumoniae, a human pathogen that can pose severe problems in patients whose immunity is impaired. PMNs from chronic dialysis patients showed a diminished in vitro phagocytic efficiency with a reduced phagocytosis and bactericidal activity towards intracellular K. pneumoniae compared with that seen in PMNs from healthy subjects. When co-amoxiclav was added to PMNs from chronic hemodialysis patients, it was able to restore the depressed primary functions of PMNs, resulting in a significant high increase in both phagocytosis or killing activity. A similar pattern was detected with PMNs collected from hemodialysis patients treated with co-amoxiclav. The results of the present study provide evidence that co-amoxiclav is able to induce stimulation of depressed phagocytic response of PMNs from patients on chronic hemodialysis, restoring their primary functions both in vitro and in vivo.

Improved phagocyte response by co-amoxiclav in renal transplant recipients.

BACKGROUND: Infectious diseases are a major source of morbidity and mortality for immunosuppressed transplant recipients and the antimicrobial chemotherapy can be often less effective in these individuals, because the contribution of underlying host defenses is absent. METHODS: The influence of co-amoxiclav on the functions of polymorphonuclear granulocytes (PMNs) from renal transplant recipients were investigated. RESULTS: PMNs from renal transplant recipients showed a diminished phagocytic activity with reduced phagocytosis and bactericidal activity against intracellular Klebsiella pneumoniae, compared to that seen with PMNs from healthy subjects. Co-amoxiclav significantly elicited the functions of PMNs from uremic patients, resulting in an increased percentage of ingested klebsiellae and in a higher bactericidal effect (98-99%), compared with the drug-free control system. When PMNs were collected from renal transplant recipients treated with co-amoxiclav a significant high increase in both phagocytosis and killing activity were detected, showing the co-amoxiclav capability of "restoring" even in vivo the depressed primary functions of PMNs. CONCLUSIONS: The interesting beneficial properties of co-amoxiclav, which result in restoring the phagocyte-dependent response in renal transplant patients both in vitro and in vivo, may make this drug more suitable for the treatment of infections in patients with defects of phagocyte functions.

Influence of a new fluoroquinolone, AF3013 (the active metabolite of prulifloxacin), on macrophage functions against Klebsiella pneumoniae: an in vitro comparison with pefloxacin.

The efficacy of an antibiotic in the treatment of bacterial infections depends upon the interaction of bacterium, drug and phagocytes. In this study we have investigated the influence of AF3013, a new fluoroquinolone, on the activities of mouse peritoneal macrophages against Klebsiella pneumoniae, in comparison with the influence of pefloxacin. Bacterial susceptibility to phagocytosis and intracellular killing were determined after klebsiellae and macrophages had been incubated simultaneously with inhibitory concentrations of both AF3013 and pefloxacin and following pre-exposure of the microorganisms and the macrophages individually to the same concentrations of each drug. Under the experimental conditions used, both AF3013 and pefloxacin potentiated the phagocytic and microbicidal activities of the macrophages, although different mechanisms may be involved.