Interactions between oral commensal Candida and oral bacterial communities in immunocompromised and healthy children.

Candida species are usually found as commensal microorganisms in the oral cavity of healthy people. During chemotherapy, cytostatic drugs lead to depletion of the oral flora with the emergence of a dominant bacterial species. The transition from commensal to pathogenic state, further associated with yeast colonization and oral mucositis implies a replacement of the dominant microorganism by Candida albicans. This process goes plausibly through cooperation between C. albicans and bacteria. This study focused on the first step of cooperation between microorganisms isolated from the same oral flora either of leukemic or healthy children. C. albicans isolated from 8/20 children were cultured to display their noninvasive blastosporic yeast form and mixed with their dominant bacteria to study the capacity of planktonic aggregation and the early state of biofilm formation. None of the dominant bacteria opposed the presence of yeast, on the contrary, an interesting cooperation was observed. This behavior is apparently different from that observed when mixing the type strains. In fact, three mutated C. albicans strains display, by their spontaneous ability to form filament, enhanced risks of virulence for leukemic ill carriers. Despite such risks, neither oral nor systemic pathology were observed in ill patients probably because the study was conducted during the first course of chemotherapy and Candida colonization is related to the number of chemotherapeutic cycles. The presence of C. albicans during the initial cycle represents, by its ability to interact with oral bacteria, an actual threat for further cures.

In vitro study of the effect of titanium on porphyromonas gingivalis in the presence of metronidazole and spiramycin.

Septic peri-implantitis is the main clinical complication encountered following the insertion of titanium implants. It may be resistant to conventional antibiotic treatments. Reports in the literature about antibiotic behavior in the presence of titanium remain controversial. They vary from a bacteriostat to a decreased effect of antibiotic. This study examined, in vitro, the viability of Porphyromonas gingivalis, frequently associated with periodontal diseases, in the presence of titanium and antibiotics (spiramycin and metronidazole alone or in combination). Viability of P. gingivalis was determined, versus a standard curve using the Live/dead Baclight Bacteria Viability Kit on 96 well microplates. The results of 48 experiments (60 measurements each) were compiled in a database and compared to each other using the chi2p < 0.05 test. When used alone, titanium enhanced bacterial growth as the nickel-chrome control. However, when titanium was used in the presence of antibiotics, antibiotics kept their own effects. Even more, titanium was shown to potentialize the effect of metronidazole. The strengthening of effectiveness of metronidazole by titanium may be due to the oxidation potential of the metal. This chemical property could explain the conflicting data reported in the literature.

In vitro evaluation of the retention of three species of pathogenic microorganisms by three different types of toothbrush.

The retention and survival of microorganisms on toothbrushes pose a threat of recontamination for certain patients at risk. In order to measure the influence of brush design and optimize the choice of toothbrush model for complementary studies, the in vitro retention of three microbial species (Porphyromonas gingivalis ATCC 33277, Streptococcus mutans ATCC 25175 and Candida albicans ATCC 26555) was evaluated for three types of toothbrush. Two series of standardized experiments were carried out for each brush and microorganism. The first series tested the retention of the microorganisms on the head portion of the brush, while the second measured retention on the head of the brush and the part of the handle inserted in the mouth during brushing. For each series, the microorganisms were counted at T0 and T24 (after storage of the brushes at room temperature for 24 h). Depending on the microorganism studied, from 0.2% to 2% of the initial inoculum was retained on the brush. The number detected increased with the size of the exposed area. After 24 h, P. gingivalis and S. mutans were found on only one type of brush. C. albicans survived on all three. These results confirm that microorganisms can quickly colonize toothbrushes.

Oral complications during treatment of malignant diseases in childhood: effects of tooth brushing.

During anticancer treatment, oral lesions considerably aggravate the child's clinical condition and increase the risk of infection. This prospective study evaluated the incidence, nature and chronology of oral complications arising during the first 6 weeks of chemotherapy. 131 children were included in this study, and their oral and dental health evaluated on enrolment. Each child was observed once a week, for 6 weeks. Fifty-two per cent (68/131) of the children presented with at least one oral lesion. Two oral healthcare regimens (with or without tooth brushing) were evaluated. Tooth brushing significantly reduced the number of children affected. Standardised multicentre studies should permit the definition of oral care regimens which would eliminate pain and reduce the risk of infection in children hospitalised for cancer.

Evaluation of root canal bacteria and their antimicrobial susceptibility in teeth with necrotic pulp.

This study aimed to evaluate the microbiota of necrotic pulp in teeth without carious lesions where the crown and root were intact and to test the sensitivity of this microbiota to antibiotics in order to improve treatment. The necrotic pulp was sampled from 26 single-rooted teeth in intact pulp chambers. A total of 84 strains were isolated. The number of species isolated per tooth varied from 2 to 8, with a strong component (81%) of anaerobic bacteria. The most commonly represented species were Bacteroides gracilis, Propionibacterium acnes, Fusobacterium nucleatum, Prevotella buccae and Eubacterium lentum. The sensitivity of these organisms to amoxicillin, amoxicillin combined with clavulanate and tetracycline was evaluated by Etest on 38 isolates. For all strains tested, the minimum inhibitory concentration values obtained were low and substantially below effective serum concentrations for these antibiotics. These data enable us to devise suitable treatments for acute development of apical lesions and to prevent dissemination of this source of infection to the rest of the host.

Oral pathoses caused by Candida albicans during chemotherapy: update on development mechanisms.

Oral candidiasis occurs at a high frequency among immunocompromised hosts. The development mechanisms of oral pathoses associated with Candida are complex and certainly multifactorial. In immunocompromised patients, they include the evolution of the buccal flora associated with the influence of antineoplastic treatments and immunosuppression. They also include adherence of Candida to epithelial cells of the oral cavity as a function of host cell-related and yeast-related factors. Interaction and cooperation between Candida and bacteria could be a third influence in the development of oral candidiasis. It seems important to determine these mechanisms more precisely so as to improve preventive and therapeutic measures.

Calibration of an in vitro assay system using a non-adherent cell line to evaluate the effect of a drug on Toxoplasma gondii.

A TG 180 non-adherent cell culture with Toxoplasma gondii and spiramycin was performed in order to calibrate TG 180 cells used in a therapeutic assay system. TG 180 cells were infected with the RH strain of T. gondii, and spiramycin was added at final concentrations of 1, 2, 4, 8, 12, 16, 20 and 25 micrograms/ml. A least-squares linear regression with confidence interval was calculated from the experimental curve and allowed the determination of the 50% inhibitory concentration of spiramycin. The IC50 of 13.7 micrograms/ml obtained is comparable with the results of the literature. The system including TG 180 cells (recently cultured in vitro) provides a rapid, accurate and economical determination of the effects of a drug on Toxoplasma gondii.

Osseous concentrations of gentamicin after implantation of acrylic bone cement in sheep femora.

17 sheep received femoral implantation of 'Cérafix Genta', containing gentamicin 0.6 or 1.2 g per dose either unilaterally (first 3 sheep) or bilaterally (remaining 14 sheep). Highest concentrations in bone were measured after 24 and 48 post-operative hours (respectively 36 and 72 mg/kg for Cérafix 0.6 g and 1.2 g). Gentamicin concentrations in bone marrow and femoral heads were in the same range. Blood and urine concentrations of gentamicin measured in sheep were comparable to those obtained in man. An extrapolation of the gentamicin behaviour from sheep to humans, might be possible: the sheep weight and femoral dimensions were comparable to those of humans and the method of implantation was similar in man and animal. For up to 18 months after operation, gentamicin levels in bone were always higher than critical concentration (4 mg/kg). For the early post-operative period, blood and urine levels always remained below gentamicin toxic concentrations.

Comparative study of gentamicin release from normal and low viscosity acrylic bone cement.

The pharmacokinetics of gentamicin were studied after total hip joint arthroplasties in 2 groups of 10 patients. The prosthesis was performed in the first group with 'Palacos R plus gentamicin' (normal viscosity), manufactured by Schering, and in the second group with 'Cerafix genta R' (low viscosity) manufactured by Ceraver-Osteal. Both cements included similar concentrations of gentamicin. Urine was collected at 12-hour intervals for 15 days after operation, and drainage fluids for 48, 72 or 108 hours. Blood samples were taken 3 and/or 5 hours after prosthesis implantation. In both cases, high concentrations of gentamicin were found in drainage fluids and urine during the early postoperative period. Mean gentamicin excretion curves were calculated by a computer-aided design program (SIAM) for the 2 cements. The release of gentamicin was biphasic in both cases, although the slow elimination phase appeared to be longer for 'Cerafix'. In the first postoperative period, the drug had a better bioavailability during the rapid elimination phase in the case of 'Palacos'. The calculated peak blood concentration was in the same range for both compounds. The conclusion is drawn that, in patients undergoing total hip joint arthroplasties, gentamicin concentrations reach local levels higher than the minimum inhibitory concentrations of most of the likely sensitive pathogens. However, in both cases, as blood concentrations appear to be low, patients will not be protected against systemic infections. Both cements have similar antibacterial properties but the mechanical properties of 'Cerafix' are the better of the two.

Release of gentamicin from acrylic bone cement.

The pharmacokinetics of gentamicin were studied after total hip joint arthroplasties performed with "Palacos R plus gentamicin' in 10 patients. Urine was collected at 12-hour intervals for 15 days after operation, and drainage fluids for 48, 72 or 108 hours. Blood samples were taken 3 and/or 5 hours after prosthesis implantation. High concentrations of gentamicin were found in drainage fluids. Excretion curves in drainage fluids or urine were fitted by a computer-aided design program (SIAM) and the mean curves established. Elimination of gentamicin was biphasic in both cases. The rapid phases had a half-life of 2.97 hours in drainage fluids and 7.16 hours in urine. Half-lives of the slow phases were 13.5 and 47.12 hours, respectively. The mean percentage of total gentamicin released by the two routes was 5.78% of the quantity implanted. The calculated peak blood concentration was 0.12 mg/L. It is concluded that gentamicin concentrations locally reach levels higher than minimum inhibitory concentrations of most of the likely pathogens in patients undergoing total hip joint arthroplasties with "Palacos R plus gentamicin' bone cement. However, as blood concentrations appear to be low, patients may not be protected against systemic infections.

[Antibiotic-loaded orthopedic cements. Pharmacokinetics and bone level]. / Ciments orthopédiques aux antibiotiques. Pharmacocinétique et taux osseux.

A mechanical study in the laboratory of 10 types of cement has shown that the characteristics of low viscosity antibiotic-loaded cements are comparable with those of standard cement without antibiotic and of standard viscosity. A study of the release of Gentamycin in 26 patients treated by total hip replacement showed that the concentration of antibiotic in the drainage fluid was much greater than the minimum inhibitory concentration whereas the low blood concentration gave no risk of ototoxicity or nephrotoxicity. This method of administration achieved antibiotic concentrations in the tissues in contact with the prosthesis 10 times greater than those obtained by injection. In sheep, the intra-osseous concentration was studied in 32 femora after insertion of low viscosity Gentamycin-loaded cement. The levels remained raised to 4 times the minimum inhibitory concentration for up to one year after operation, even with cements with a low concentration of antibiotic of 0.6 g/dose. The concentrations obtained in the drainage fluid, in the peri-prosthetic tissues and especially in bone, confirm the effectiveness and the prolonged action of antibiotic therapy by cement and its value in the revision of infected prostheses and in prophylaxis in primary surgery. This justifies the further study of combinations of cement with new antibiotics with a broader spectrum than Gentamycin since there is no concern with the cements currently in use that the mechanical quality is less than that of standard cement.