Characterization of levofloxacin non-susceptible clinical Streptococcus pyogenes isolated in the central part of Italy.

We investigated the prevalence, genetics, and clonality of fluoroquinolone non-susceptible isolates of Streptococcus pyogenes in the central part of Italy. S. pyogenes strains (n = 197) were isolated during 2012 from patients with tonsillopharyngitis, skin, wound or invasive infections and screened for fluoroquinolone non-susceptibility (resistance to norfloxacin and levofloxacin minimum inhibitory concentration (MIC) = 2 mg/L) following EUCAST guidelines. First-step topoisomerase parC and gyrA substitutions were investigated using sequencing analysis. Clonality was determined by pulsed field gel electrophoresis (PFGE; SmaI digestion) and by emm typing. The fluoroquinolone non-susceptible phenotype was identified in 18 isolates (9.1 %) and correlated with mutations in parC, but not in gyrA, the most frequent leading to substitution of the serine at position 79 with an alanine. Most of the fluoroquinolone non-susceptible isolates belonged to the emm-type 6, even if other emm-types were also represented (emm75, emm89, and emm2). A significant level of association was measured between PFGE and both emm type and substitutions in parC. The prevalence of fluoroquinolone non-susceptible Streptococcus pyogenes isolates in Italy is of concern and, although the well-known emm type 6 is dominant, other types are appearing and spreading.

Occurrence of Candida species colonization in a population of denture-wearing immigrants.

Infection of the oral cavity and dentures by Candida species are frequent in denture wearers. C. albicans is the most common pathogen; however, other emerging Candida species are also responsible for this condition. Few data are available about the occurrence of Candida species in the oral cavities of denture-wearing immigrants to Italy. In this study, we compare the Candida species found in the oral mucosa and on dentures from a population of denture wearing immigrants to Italy to a matched Italian group. Oral swabs were collected from dentures and the underlying mucosa of patients enrolled in the study and were then cultured to test for the presence of Candida species in each sample. Out of 168 patients enrolled (73 Italians and 95 immigrants), 51 Italians (69.8 percent) and 75 immigrants (78.9 percent) tested positive for the presence of Candida. Candida albicans was the most frequently observed species overall; however, we found a higher occurrence of C. glabrata among immigrants than among Italians. In addition, immigrants displayed a higher incidence of Candida – associated stomatitis and a lower mean age than Candida-positive individuals from the Italian group. Immigrants are more prone to longer colonization of the oral mucosa and dentures by Candida. In these patients, dentures must be checked periodically to prevent the presence of Candida.

Antibacterial activity of various antibiotics against oral streptococci isolated in the oral cavity.

A total of 550 oral streptococci: 270 Streptococcus mitis, 110 Streptococcus sanguis, 90 Streptococcus anginosus, 50 Streptococcus mutans, 30 Streptococcus salivarius, were isolated from dental plaque and gengival crevices of patients and tested for their susceptibility to 12 ß-lactam antibiotics and to 5 non-ß-lactam antibiotics, using the microdiluition method. Overall, a reduced susceptibility to penicillin was recorded in 13.4% of cases. The percentage of strains resistant to penicillin appeared significantly higher in S. mitis (24%) than in S. sanguis (19%), in S. mutans (14%) and in S. salivarius (10%). No levels of penicillin resistance were shown by 90 strains of S. anginosus. In susceptibility test to antibiotics, imipenem was the most active molecule tested, confirming its general good activity against oral streptococci. Also third generation cephalosporins such as ceftriaxone and fourth generation cephalosporins such as cefepime, showed good activity. Chinolones, glycopeptides and rifampicin confirmed a good activity against oral streptococci.

Antibacterial activity and anti-biofilm effect of chitosan against strains of Streptococcus mutans isolated in dental plaque.

Streptococcus mutans is the major cause of dental plaque and is often associated with biofilm formation. The aim of this study is to evaluate the activity of a hydrosoluble derivative of chitosan against S. mutans biofilms in vitro and in vivo. Strains of S. mutans were isolated from the dental plaque of 84 patients enrolled in the study. The antibacterial activity of chitosan was determined by broth microdilutions. The effect of chitosan at different concentrations and exposure times on S. mutans biofilms at different phases of development was assessed by a clinical study using the classical "4-day plaque regrowth" experiment in adult volunteers. The MIC values of chitosan were between 0.5 and 2 g/L. Compared to distilled water, the chitosan solution significantly decreased the vitality of plaque microflora (p

Characterization of a Staphylococcus aureus strain showing high levels of biofilm formation isolated from a vascular graft: case report.

A methicillin-susceptible Staphylococcus aureus strain, SA-DZ1, was isolated from an infected bypass crossover graft. Its general microbiological features were reminiscent of those previously described for the wound Wiley strain. Removal of the prosthetic device was necessary to resolve the infection. SA-DZ1 grown under different conditions showed a very strong and distinctive biofilm-producing phenotype, which was also visualized by confocal laser scanning microscopy. The biofilm extracellular matrix was essentially polysaccharidic, as determined by differential growth and physicochemical tests. By Multi Locus Sequence Typing (MLST), SA-DZ1 was classified as st94, a single locus variant of st8. Several other genetic traits assayed by PCR, such as agr-type and the presence of gene encoding proteins involved in adhesion and virulence (e.g. ica operon), confirmed the identifying features of this clinical isolate.

Distribution of mef(A)-containing genetic elements in erythromycin-resistant isolates of Streptococcus pyogenes from Italy.

In total, 124 Streptococcus pyogenes isolates were obtained from throat cultures of different symptomatic patients. All isolates showed M-phenotype macrolide resistance and contained the macrolide efflux gene mef(A). The isolates were screened for the presence and insertion site of mef(A)-containing genetic elements. In 25.8% of the isolates, mef(A) was found to be carried by elements belonging to the Tn1207.3/Phi10394.4 family inserted in the comEC gene, while 74.2% contained chimeric elements with a different genetic structure and chromosomal location, probably associated with the recently described 60-kb tet(O)-mef(A) element.

In vitro selection of resistance to clarithromycin in Streptococcus pneumoniae clinical isolates.

In this study the effects of exposure to serum, lung and breakpoint concentrations on Streptococcus pneumoniae susceptibility to clarithromycin, azithromycin, amoxicillin/clavulanate, levofloxacin and moxifloxacin were evaluated. Development of resistance was determined by multi-step and single-step methodologies. In the first experimental set, minimum inhibitory concentrations (MICs) were determined after 10 passages on antibiotic-gradient plates and 10 passages on antibiotic-free plates. Acquisition of resistance was defined as an increase of > or = 4-fold from the starting MIC. In single-step studies, the rate of spontaneous mutations was calculated after a passage on antibiotic-containing agar plates. Azithromycin and levofloxacin gave the highest number of strains with MIC increased of at least 4 times the starting value, followed by moxifloxacin and by clarithromycin which only at the lowest concentration tested selected for resistance in 5 strains. Amoxicillin/clavulanate never displayed > or = 4-fold MIC increase. Frequencies of mutation were lower for clarithromycin and moxifloxacin than for the comparators. At lung concentrations clarithromycin had limited potential to select for resistance.

SmaI macrorestriction analysis of Italian isolates of erythromycin-resistant Streptococcus pyogenes and correlations with macrolide-resistance phenotypes.

High rates of erythromycin resistance among Streptococcus pyogenes strains have been reported in Italy in the last few years. In this study, 370 erythromycin-resistant (MIC, > or = 1 microg/mL) Italian isolates of this species obtained in 1997-1998 from throat swabs from symptomatic patients were typed by analyzing SmaI macrorestriction fragment patterns by pulsed-field gel electrophoresis (PFGE). Among the typable isolates (n = 341; the genomic DNA of the remaining 29 isolates was not restricted by SmaI), 48 distinct PFGE types were recognized, of which 31 were recorded in only one isolate (one-strain types). Fifty-two percent of typable isolates fell into three type clusters and 75% into six, suggesting that erythromycin-resistant group A streptococci circulating in Italy are polyclonal, but the majority of them probably derives from the spread of a limited number of clones. In parallel experiments, the 370 test strains were characterized for the macrolide resistance phenotype: 80 were assigned to phenotype cMLS, 89 to phenotype iMLS-A, 33 to phenotype iMLS-B, 11 to phenotype iMLS-C, and 157 to phenotype M. There was a close correlation between these phenotypic data and the genotypic results of PFGE analysis, the vast majority of the isolates assigned to individual PFGE classes belonging usually to a single phenotype of macrolide resistance. All of the 29 untypable isolates belonged to the M phenotype. Further correlations were observed with tetracycline resistance.

In vitro antibacterial activity of rifaximin against Clostridium difficile, Campylobacter jejunii and Yersinia spp.

Fifty-four isolates of Campylobacter jejunii, 91 isolates of Yersinia spp. and 56 isolates of Clostridium difficile, recovered from stools of patients with diarrhoea or other intestinal disturbances and from stools of asymptomatic patients receiving antibiotic therapy, were tested in vitro for susceptibility to rifaximin, rifampicin and neomycin. The in vitro antibacterial activities were found to be comparable against the aerobic bacterium; on the contrary, against microaerophilic and anaerobic bacteria rifaximin and rifampicin were much more effective than neomycin.

Antibiotic susceptibility of respiratory pathogens recently isolated in Italy: focus on cefditoren.

The aim of this study was to evaluate the in vitro antibiotic susceptibility of respiratory pathogens recently isolated in Italy to commonly used antibiotics including cefditoren. Six clinical microbiological laboratories collected, between January and September 2009, a total of 2,510 respiratory pathogens from subjects with community-acquired respiratory tract infections (CARTI). Ceftditoren, out of all the beta-lactams studied, had the lowest MIC(90 )against 965 strains of Streptococcus pneumoniae examined, followed by cefotaxime and ceftriaxone (2% resistance in penicillin-resistant S. pneumoniae (PRSP)). Against 470 Haemophilus influenzae , independently of their production of beta-lactamases or ampicillin resistance, cefditoren was the oral cephalosporin with the best in vitro activity, comparable to that of the injectable cephalosporins and levofloxacin. Higher MIC(90)s were found for the macrolides (4 - 16 mg/l) and cefaclor (4 - 32 mg/l). As was foreseeable, Streptococcus pyogenes (225 strains) was uniformly sensitive to all the beta-lactam antibiotics, but the elevated MIC(90 )values reduced (<75%) susceptibility of this pathogen to macrolides. Beta-lactamase-negative Moraxella catarrhalis (100 strains) had reduced susceptibility only to the macrolides, while the 250 beta-lactamase-producing strains also had reduced susceptibility to cefuroxime. Levofloxacin showed the lowest MIC(50)/MIC(90 )values in the producing strains, whereas cefditoren, cefotaxime and ceftriaxone in the non-producers. As regards the enterobacteriaceae, cefditoren and levofloxacin had the lowest MIC(90)s against Klebsiella pneumoniae. Cefditoren and the third-generation injectable cephalosporins had the lowest MIC(90)s against Escherichia coli (100% susceptibility) while levofloxacin was less active (86% susceptibility).In conclusion, cefditoren's wide spectrum and high intrinsic activity, as well as its capacity to overcome most of the resistance that has become consolidated in some classes of antibiotics widely used as empiric therapy for CARTI, allows us to suggest that cefditoren might be included in the european guidelines as one of the first-choice antibiotics in the treatment of CARTI.

Analysis of different genetic traits and their association with biofilm formation in Staphylococcus epidermidis isolates from central venous catheter infections.

The aim of the present study was to characterize clinical isolates of Staphylococcus epidermidis, one of the bacterial species most often implicated in foreign-body-associated infections, for their ability to form biofilms and for the presence of mecA and IS256 element. Sixty-seven Staphylococcus epidermidis clinical isolates, obtained from implantable medical devices, were investigated. Overall, 70% of the strains were positive for ica operon genes, 85% possessed atlE, and 46% contained aap. In 89% of the population, the Congo red agar test confirmed the correlation between the presence of ica genes and slime expression. Almost all of the strains could be classified as biofilm producers by both the crystal violet assay and microscopy. The bacterial population studied showed a very high frequency of strains positive for mecA as well as for the IS256 element. Although well-structured biofilms have been previously observed only in those strains possessing genes belonging to the ica operon, this study demonstrates that strains lacking specific biofilm-formation determinants can be isolated from catheters and can form a biofilm in vitro. Hence, different and yet-to-be identified factors may work together in the formation and organization of complex staphylococcal microbial communities and sustain infections associated with implanted medical devices.

Serum levels and urinary excretion in humans of BL-S 578 (cefadroxil), a new semisynthetic cephalosporin.

Single doses of 250 and 500 mg of BL-S 578 (cefadroxil), a new semisynthetic cephalosporin, were orally administered to 13 normal, healthy volunteers and serum levels determined at timed intervals for 7 h. Peak concentration was obtained at 1 1/2 h after administration of 250 mg (8.981 micrograms/ml) or 500 mg (17.861 micrograms/ml). Urniary excretion levels within 24 h after ingestion of single doses of 250 and 500 mg of cefadroxil were 89.92 and 86.34%, respectively.

Laboratory studies with BL-S 578 (Cefadroxil) a new broad-spectrum orally active cephalosporin.

BL-S 578 (Cefadroxil) is a new orally active semisynthetic cephalosporin antibiotic with broad-spectrum antibacterial activity. The new compound was evaluated in vitro in comparison with cephalexin. Some properties studies such as, antibacterial activity, binding with serum proteins and stability in acid and neutral solution at 37 degrees C for both cephalosporins were similar. In experimental infections of mice, the protective action of BL-S 578 was more effective than cephalexin against Staphylococcus aureus and Streptococcus pneumoniae. BL-S 578 was more resistant than cephalexin to the beta-lactamases produced by Klebsiella pneumoniae and Escherichia coli.

[Antibacterial activity of a carbenicillin-cephaloridin combination]. / Attivitá antibatterica dell'associazione carbenicillina-cefaloridina

The effectiveness of the combination of carbenicilline and cephaloridine in the ratio of 4:1 was studied. The antibacterial activity of the association whether in vitro or in vivo is sinergic, that is, superior to the simply addition by the individual components. The hematic levels of the combination remain high up to 5 hours after the administration and are greater than those obtained with carbenicilline alone. Levels in the urine are high, therefore the species judged to be resistent in vitro may become sensitive.

[Experimental studies on the antibacterial activity of the association cephaloridine-dicloxacilline (author's transl)]. / Studi sperimentali sull'attivita' antibatterica dell'associazione cefaloridina-dicloxacillina

A study on the efficiency of the association cephaloridine-dicloxacilline in the ratio 2:1 has been carried out. Both in vitro and in vivo the antibacterial activity shown by the association is higher than that merely additive of the single components and is due to positive interaction.

Pharmacokinetics of cefotetan in elderly subjects after intramuscular administration.

The pharmacokinetics of cefotetan were studied in 10 healthy male subjects 65-75 years of age with normal liver function and a creatinine clearance of greater than 80 ml/min after single 2 g intramuscular doses. The mean plasma level at 0.5 h was 52.50 +/- 9.16 micrograms/ml. Peak concentrations were 91.78 +/- 12.02 micrograms/ml at 3 h, declining to 10.33 +/- 2.18 micrograms/ml at 18 h, 4.0 +/- 1.12 micrograms/ml at 24 h after the start injection. The percentage of the dose recovered in urine (0 to 24 h) was 60.3%. Cefotetan plasma clearance showed a statistically significant correlation (r = 0.956, p less than 0.001) with measured creatinine clearance and the positive intercept ordinate confirmed a nonrenal clearance of the drug (biliary excretion). The normal age-related changes in cefotetan kinetics were relatively small and dosage adjustment was not necessary for normal elderly subjects requiring cefotetan.

A linear model for the pharmacokinetics of azithromycin in healthy volunteers.

The pharmacokinetic profile of azithromycin, after oral ingestion of 500 mg, was determined in 10 healthy volunteers. Statistical and biochemical reason seemed to indicate a zero-order absorption of the drug. The disposition of azithromycin was described by a two-compartment model (plasma compartment and extravascular compartment) with elimination from the plasma compartment. The absorption process ends abruptly after a time T = 2.3 +/- 0.49 h, from the administration. The transfer rate constant from the plasma compartment to the extravascular compartment (k12 = 0.12 +/- 0.04 h-1) and the mean residence time of the drug in the extravascular compartment (MRT2 = 43.53 +/- 13.80 h) indicate a rapid and extensive distribution of azithromycin from the serum into the extravascular fluids. The results confirmed the efficacy of a single daily dose of 500 mg per os for clinical use.

Pharmacokinetics of sulbactam/ampicillin in humans after intravenous and intramuscular injection.

We investigated the pharmacokinetic properties of sulbactam/ampicillin (S/A), after intravenous (0.5/1.0 and 1.0/2.0 g) and intramuscular (0.5/1.0 g) coadministration in 10 male subjects. After 1.0/2.0 g intravenous doses of S/A the half-lives (t1/2 beta) were 1.14 +/- 0.14/1.09 +/- 0.16 h. The values for plasma clearance (CLp) were 198.83 +/- 26.27/250.33 +/- 39.28 ml/min and the renal clearance (Clr) 173.50 +/- 19.66/208.80 +/- 26.43 ml/min. The post distributive volumes (V beta) were 19.67 +/- 3.24/23.56 +/- 5.76 liters. Similar values were obtained after 0.5/1.0 g of S/A intravenous coinjection. After 0.5/1.0 g intramuscular coadministration the t1/2 beta values were 1.26 +/- 0.18/1.20 +/- 0.15 h. The values for Clp were 208.00 +/- 28.73/243.17 +/- 33.24 ml/min, for Clr 179.50 +/- 20.26/202.67 +/- 27.61 ml/min and for V beta 22.27 +/- 4.12/25.30 +/- 4.87 liters. The renal clearance of sulbactam is comparable to that of ampicillin and both clearances are greater than the glomerular filtration rate, suggesting active renal tubular secretion of the two drugs. The large volumes of distribution, and the ratio K12/K21 = 0.5 show the extensive distribution of the two drugs into extracellular fluids. The very similar values of the pharmacokinetic parameters of sulbactam and ampicillin confirm that the kinetics of the two drugs closely resemble one another.