Roberto Mattina

Activity of N-acetyl-L-cysteine against Biofilm of Staphylococcus Aureus and Pseudomonas Aeruginosa on Orthopedic Prosthetic Materials:

Purpose Staphylococcus aureus and Pseudomonas aeruginosa are frequently isolated from biofilm-associated orthopedic implant infections. This study assessed the activity of N-acetyl-L-cysteine at inhibitory and subinhibitory concentrations against biofilm formed by S. aureus and P. aeruginosa on prosthetic materials. Methods S. aureus and P. aeruginosa biofilm on smooth polyethylene and sand-blasted titanium discs was determined by means of a spectrophotometric assay before and at 3, 6, and 18 hours after addition of N-acetyl-L-cysteine. Results N-acetyl-L-cysteine was able to disaggregate biofilm produced by S. aureus and P. aeruginosa on polyethylene and titanium discs after 3 h of incubation. A different rate in eradication of biofilm produced by P. aeruginosa was seen between polyethylene and titanium (50% vs. 20% respectively vs. biofilm formed before treatment). Results were confirmed by confocal laser scanning microscopy. Conclusions The results suggest a possible role of N-acetyl-L-cysteine in the treatment of orthopedic prosthetic infections.

Prevention and treatment of postoperative infections after sinus elevation surgery: clinical consensus and recommendations.

Introduction. Maxillary sinus surgery is a reliable and predictable treatment option for the prosthetic rehabilitation of the atrophic maxilla. Nevertheless, these interventions are not riskless of postoperative complications with respect to implant positioning in pristine bone. Aim. The aim of this paper is to report the results of a clinical consensus of experts (periodontists, implantologists, maxillofacial surgeons, ENT, and microbiology specialists) on several clinical questions and to give clinical recommendations on how to prevent, diagnose, and treat postoperative infections. Materials and Methods. A panel of experts in different fields of dentistry and medicine, after having reviewed the available literature on the topic and taking into account their long-standing clinical experience, gave their response to a series of clinical questions and reached a consensus. Results and Conclusion. The incidence of postop infections is relatively low (2%–5.6%). A multidisciplinary approach is advisable. A list of clinical recommendation are given.

In vitro selection of resistance in Escherichia coli and Klebsiella spp. at in vivo fluoroquinolone concentrations

BackgroundFluoroquinolones are potent antimicrobial agents used for the treatment of a wide variety of community- and nosocomial- infections. However, resistance to fluoroquinolones in Enterobacteriaceae is increasingly reported. Studies assessing the ability of fluoroquinolones to select for resistance have often used antimicrobial concentrations quite different from those actually acquired at the site of infection. The present study compared the ability to select for resistance of levofloxacin, ciprofloxacin and prulifloxacin at concentrations observed in vivo in twenty strains of Escherichia coli and Klebsiella spp. isolated from patients with respiratory and urinary infections. The frequencies of spontaneous single-step mutations at plasma peak and trough antibiotic concentrations were calculated. Multi-step selection of resistance was evaluated by performing 10 serial cultures on agar plates containing a linear gradient from trough to peak antimicrobial concentrations, followed by 10 subcultures on antibiotic-free agar. E. coli resistant strains selected after multi-step selection were characterized for DNA mutations by sequencing gyrA, gyrB, parC and parE genes.ResultsFrequencies of mutations for levofloxacin and ciprofloxacin were less than 10-11 at peak concentration, while for prulifloxacin they ranged from <10-11 to 10-5. The lowest number of resistant mutants after multistep selection was selected by levofloxacin followed by ciprofloxacin and prulifloxacin. Both ciprofloxacin- and prulifloxacin-resistant mutants presented mutations in gyrA and parC, while levofloxacin resistance was found associated only to mutations in gyrA.ConclusionsAmong the tested fluoroquinolones, levofloxacin was the most capable of limiting the occurrence of resistance.

Biofilm formation by bacteria isolated from upper respiratory tract before and after adenotonsillectomy

Drago L, De Vecchi E, Torretta S, Mattina R, Marchisio P, Pignataro L. Biofilm formation by bacteria isolated from upper respiratory tract before and after adenotonsillectomy. APMIS 2012; 120: 410–6.

Antiadhesive and antibiofilm activity of hyaluronic acid against bacteria responsible for respiratory tract infections.

To address the problem of limited efficacy of existing antibiotics in the treatment of bacterial biofilm, it is necessary to find alternative remedies. One candidate could be hyaluronic acid; this study therefore aimed to evaluate the in vitro antiadhesive and antibiofilm activity of hyaluronic acid toward bacterial species commonly isolated from respiratory infections. Interference exerted on bacterial adhesion was evaluated by using Hep‐2 cells, while the antibiofilm activity was assessed by means of spectrophotometry after incubation of biofilm with hyaluronic acid and staining with crystal violet. Our data suggest that hyaluronic acid is able to interfere with bacterial adhesion to a cellular substrate in a concentration‐dependent manner, being notably active when assessed as pure substance. Moreover, we found that Staphylococcus aureus biofilm was more sensitive to the action of hyaluronic acid than biofilm produced by Haemophilus influenzae and Moraxella catarrhalis. In conclusion, hyaluronic acid is characterized by notable antiadhesive properties, while it shows a moderate activity against bacterial biofilm. As bacterial adhesion to oral cells is the first step for colonization, these results further sustain the role of hyaluronic acid in prevention of respiratory infections.

Aetiology and antibiotic resistance patterns of urinary tract infections in the elderly: a 6-month study.

Urinary tract infections (UTIs) are a common cause of bacteraemia in the elderly and are associated with a high probability of hospitalization. Despite the impact of UTIs on health status and quality of life, a limited number of studies have evaluated their aetiology in this population. This study aimed to evaluate the microbial aetiology and pattern of susceptibility of bacteria causing UTIs in the elderly. For this purpose, a retrospective cohort study of elderly residents (n = 472, aged >65 years) in 14 nursing homes in Milan (Italy) and its province was performed. Globally, 393 micro-organisms from 328 samples were isolated: Escherichia coli was the most prevalent (44.8 %), followed by Proteus mirabilis (20.4 %), Providencia spp. (8.9 %), Klebsiella spp. (6.4 %) and Pseudomonas aeruginosa (4.6 %). Enterococci were the most frequently isolated Gram-positive organisms (7.4 %). Almost all Enterobacteriaceae were susceptible to nitrofurantoin, carbapenems and amikacin. Extended-spectrum β-lactamases were detected in 42.1 % of isolates. The most active antibiotics against P. aeruginosa were colistin, amikacin and piperacillin/tazobactam. All Gram-positive organisms were susceptible to glycopeptides and linezolid, and 90 % were susceptible to nitrofurantoin. Fluoroquinolones showed a limited activity against all the tested micro-organisms. Escherichia coli remains the major micro-organism responsible for UTIs in older people, although to a lesser extent than in a younger population. The high rates of resistance observed in this study make careful use of antibiotics advisable to limit further development of resistance.

Comparative evaluation of synergy of combinations of β-lactams with fluoroquinolones or a macrolide in Streptococcus pneumoniae

OBJECTIVES Streptococcus pneumoniae has shown a great ability to develop efficacious mechanisms of resistance to the main drugs for the treatment of pneumonia, such as β-lactams, macrolides and fluoroquinolones. The present study aimed to compare the antipneumococcal activity of combinations of respiratory fluoroquinolones with cephalosporins (either parenteral or oral) or protected penicillin versus the standard combinations (i.e. a macrolide with a protected penicillin or cephalosporin) against 100 isolates with different susceptibilities to macrolides and/or penicillin. METHODS Chequerboard assays for all isolates and time-kill curves for nine isolates with different patterns of susceptibility were performed. Synergy between antibiotics at serum peak concentrations was also determined. RESULTS The combination of levofloxacin with ceftriaxone produced the highest rate of synergy (54/100), mainly against macrolide-resistant strains (22/30). Antagonism was not observed for any tested combination apart from clarithromycin with amoxicillin/clavulanic acid (22/100 isolates). Although the killing activities of all antibiotics improved when they were tested in combination, synergy was observed only for some combinations after 12 and/or 24 h. Serum concentrations were effective in inhibiting the growth of the tested strains. CONCLUSIONS Combinations of levofloxacin with parenteral cephalosporins were the most active among all the tested combinations, while antagonism occurred when clarithromycin and amoxicillin/clavulanic acid were tested.

In vitro activity of a new quinolone, rufloxacin, against nosocomial isolates

The in vitro activity of rufloxacin (MF 934), a new broad-spectrum fluoroquinolone, was tested against 1,032 gram-positive and gram-negative clinical isolates and compared to that of five other compounds of this class. All quinolones except for ciprofloxacin had limited activity against group A and B streptococci and pneumococci (MIC 90% of 4-64 mg/l) and no activity against enterococci. Most species of the enterobacteriaceae and staphylococci were found to be sensitive to rufloxacin (MIC 90% of 0.5-8 and 2-8 mg/l). Like the other quinolones except for ciprofloxacin, rufloxacin was not active against Pseudomonas aeruginosa. The antibacterial activity of rufloxacin was affected only minimally by an increase in the bacterial inoculum or by alterations in the pH of the medium. In spite of the relatively higher MICs of rufloxacin compared to those of the other quinolones, its favorable pharmacokinetic properties may account for its good clinical efficacy.

Pharmacokinetics of rufloxacin in healthy volunteers after repeated oral doses

Rufloxacin is a new broad-spectrum fluoroquinolone antibacterial agent. The pharmacokinetics and safety of rufloxacin were evaluated after repeated oral administration to healthy volunteers. The drug was administered once a day for 6 consecutive days following two different dose schedules. The first group of 11 subjects was given a loading dose of 300 mg on the first day and 150 mg on the subsequent 5 days. The second group of 12 subjects was given a loading dose of 400 mg and 200 mg for 5 days. Serum levels and urine concentrations of rufloxacin were determined by microbiological assay. A simultaneous fit of all data points for each subject was done according to a one-compartment open model. The drug was rapidly absorbed (absorption half-life 17 +/- 6 min in the 300 + 150 mg and 11 +/- 5 min in the 400 + 200 mg dose regimen group) and reached maximal serum concentrations (2.77 +/- 0.24 and 3.62 +/- 0.35 micrograms/ml) 4.2 +/- 0.4 and 4.0 +/- 0.9 h after the first administration. Steady-state serum concentrations (3.19 +/- 0.31 and 4.06 +/- 0.33 micrograms/ml) were reached in 3.7 +/- 0.7 and 4.5 +/- 0.4 days. Elimination half-lives were 29.5 +/- 2.4 and 36.0 +/- 2.8 h. Apparent volumes of distribution were 111 +/- 8 and 136 +/- 16 liters and apparent plasma clearances were 46 +/- 5 and 44 +/- 4 ml/min. Renal clearances were 18 +/- 3 and 17 +/- 2 ml/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibacterial activity of cefditoren against major community-acquired respiratory pathogens recently isolated in Italy.

Abstract In this study we evaluated the in vitro activities of cefditoren - a broad-spectrum oral cephalosporin - and other comparator agents against 2,396 fresh isolates from community-acquired respiratory tract infections, collected from 6 clinical Italian microbiology laboratories. On penicillin-susceptible pneumococci and Streptococcus pyogenes, cefditoren demonstrated to be the most active antibiotic (MIC90 values of 0.03 and 0.06 mg/L respectively), showing only a slight decrease in potency on penicillin-intermediate and re-sistant pneumococci (MIC90 value 0.5 mg/L, 1.0 mg/L respectively). All the other comparators displayed MIC90 values of 4 - 8 mg/L for penicillins and of 4 to >64 mg/L for the oral cephalosporins. Cefditoren and levofloxacin were the most active against MSSA (MIC90 0.5 mg/mL). Cefditoren displayed a uniformly potent inhibitory activity (MIC90 of 0.03 mg/L) against all strains of Haemophilus influenzae, regardless of their ampicillin resistance (mediated or not by beta-lactamase production), while against Moraxella catarrhalis MIC90 values were higher against beta-lactamase-positive (0.25 mg/L). Cefditoren was active also against Klebsiella pneumoniae and Escherichia coli: in this case its activity was comparable with that of levofloxacin. In conclusion, cefditoren, due to its potent activity, is a new effective therapeutic option for the treatment of respiratory tract infections.