M. Toscano

Microbiological Assessment of Some Powdered Infant Formulas: From Quality to Antibiotic Resistance Evaluation

Living bacteria are daily used for human consumption as food supplements, also in infant formulas.The amount of ingested viable cells seems to be able to influence the probiotic effectiveness; so it is essential that products available on the market are correctly labelled and that the viability and identity of each strain is ensured. For this purpose, an analysis was conducted on 8 commercial infant formulas to evaluate their stability until the recommended consumption date, the bacterial load and the antibiotic susceptibility of strains used in aforementioned products. Conventional cultural methods were used to isolate and enumerate microorganisms, while their identification was performed by mean of Pyrosequencing. Finally, Minimum Inhibitory Concentrations (MIC) for erythromycin, penicillin, ciprofloxacin and tetracycline were determined using E test. Most of the tested infant formulas were correctly labelled and the number of viable cells remained stable until the recommended consumption date; however, one product did not contain viable cells of one bacterial species reported in the label. Moreover, all products contained strains showing resistance to at least one antibiotic; resistance to tetracycline and ciprofloxacin was rather common among the tested strains. In conclusion, most of the products analysed in this study were correctly labelled and contained a sufficient amount of bacteria. Although, the antibiotic resistance found in all probiotic strains underlined the need for further investigations about the real safety of probiotic strains used as food supplements.

In vitro selection and transferability of antibiotic resistance in the probiotic strain Lactobacillus reuteri DSM 17938.

Antibiotic efficacy is threatened by the continual spread of resistance in pathogenic bacteria since exposure to antibiotics may lead to emergence of resistant mutants, as widely demonstrated both in vitro and in vivo 1-3.Since commensal bacteria have been shown to transfer determinants of resistance to pathogens 4, studies on development of resistance should include also commensal bacteria. In this context, the potential for antibiotic resistance transfer in the gastrointestinal tract between probiotics and pathogenic bacteria represents a major area of concern 5. Many studies demonstrated that lactic acid bacteria, including lactobacilli, may act as reservoirs for antibiotic-resistance genes. Genes encoding resistance to various antibiotics have been detected in lactobacilli and lactococci, isolated from food and probiotic products 6-15. Moreover, antibiotic resistance genes can be transferred from lactobacilli to enterococci, especially if such genes are carried on plasmids 6,8,9,16,17. Lactobacillus reuteri is a well known probiotic microorganism which has been extensively studied in humans and animals 18,19. The use of L. reuteri as a probiotic strain has been proven safe in many studies 9. Nevertheless, some L. reuteri strains have been shown to be resistant to commonly used antibiotics and to harbor resistance genes belonging to erm (erythromycin resistance), tet (tetracycline resistance), lnu (lincosamide resistance), cat (chloramphenicol resistance) families 8,10,11,13,20,21. The present study aimed to evaluate the capability of some antibiotics to select for resistant mutants of L. reuteri DSM 17938 and the transferability of resistance to other bacteria. L. reuteri DSM 17938 is a commercial strain which has been derived from ATCC 55730 by the removal of two plasmids harboring potentially transferable resistance genes; the daughter strain has lost resistance to 13-lactams, tetracycline and lincosamide associated with these genes 22. L. reuteri DSM 17938 was isolated from a commercial product (Reuterin, Noos, Rome, Italy). Amoxicillin/clavulanic acid, erythromycin and tetracycline, as representatives of different classes, were tested at twice and four times the minimum inhibitory concentration (MIC)and at serum peak concentration (Cmax). The choice of antibiotics and

In Vitro Selection of Antibiotic Resistance in the Probiotic Strain Lactobacillus rhamnosus GG ATCC 53103

Abstract Antibiotic resistance in probiotic strains is a matter of interest due to the increase in consumption of probiotic products. Many studies have evaluated the antibiotic susceptibility of lactobacilli or the presence of resistance determinants, while knowledge on selection of resistance during exposure to antibiotics is still limited. Our aim was to evaluate the behavior of Lactobacillus rhamnosus GGATCC 53103, a well-known probiotic microorganism, during exposure to erythromycin, tetracycline, amoxicillin/clavulanate and ciprofloxacin. Our study demonstrated that prolonged exposure to erythromycin and ciprofloxacin could select mutants with reduced susceptibility, even if these modifications in susceptibility could not be attributed to known antibiotic resistance genes or genetic mutations.

Computed tomographic localization of the central sulcus: a morphometric study in adult patients

AIM To accurately describe the relations between the anatomical landmarks of the cranial convexity and the main cortical structures. MATERIAL AND METHODS A retrospective cross-sectional, observational study was performed. Computed tomography scans of 71 adult patients with no pathological imaging were analyzed. The position of the bregma and the central sulcus was determined. The distances from bregma to the pre-central and post-central sulci were calculated. The relationships from the nasion and glabella to cortical structures were also assessed. RESULTS The mean distances between the bregma and the pre-central, central and post-central sulci were 26.8 ± 7.2; 47.8 ± 5.9 and 60.6 ± 5.7 mm, respectively, without gender discrepancy. The mean distance nasion-bregma and the nasion-related measures showed significant differences among sexes. CONCLUSION The central sulcus was located accurately, on average 47.8 mm behind the bregma, which should be used instead of nasion in order to avoid gender discrepancy. The data obtained provide useful and reliable information to guide neurosurgical procedures.