Synthetic Pathways to Non-Psychotropic Phytocannabinoids as Promising Molecules to Develop Novel Antibiotics: A Review

Due to the rapid emergence of multi drug resistant (MDR) pathogens against which current antibiotics are no longer functioning, severe infections are becoming practically untreatable. Consequently, the discovery of new classes of effective antimicrobial agents with novel mechanism of action is becoming increasingly urgent. The bioactivity of Cannabis sativa, an herbaceous plant used for millennia for medicinal and recreational purposes, is mainly due to its content in phytocannabinoids (PCs). Among the 180 PCs detected, cannabidiol (CBD), Δ⁸ and Δ⁹-tetrahydrocannabinols (Δ⁸-THC and Δ⁹-THC), cannabichromene (CBC), cannabigerol (CBG), cannabinol (CBN) and some of their acidic precursors have demonstrated from moderate to potent antibacterial effects against Gram-positive bacteria (MICs 0.5-8 µg/mL), including methicillin-resistant Staphylococcus aureus (MRSA), epidemic MRSA (EMRSA), as well as fluoroquinolone and tetracycline-resistant strains. Particularly, the non-psychotropic CBG was also capable to inhibit MRSA biofilm formation, to eradicate even mature biofilms, and to rapidly eliminate MRSA persiter cells. In this scenario, CBG, as well as other minor non-psychotropic PCs, such as CBD, and CBC could represent promising compounds for developing novel antibiotics with high therapeutic potential. Anyway, further studies are necessary, needing abundant quantities of such PCs, scarcely provided naturally by Cannabis plants. Here, after an extensive overture on cannabinoids including their reported antimicrobial effects, aiming at easing the synthetic production of the necessary amounts of CBG, CBC and CBD for further studies, we have, for the first time, systematically reviewed the synthetic pathways utilized for their synthesis, reporting both reaction schemes and experimental details.

Synthesis and Antibacterial Activity of Cationic Amino Acid-Conjugated Dendrimers Loaded with a Mixture of Two Triterpenoid Acids

To counteract the growing bacterial resistance, we previously reported the remarkable antimicrobial activity of amino acid-conjugated cationic dendrimers (CDs) against several Gram-negative species, establishing that the cationic lysine was essential for their potency. In this paper, CDs conjugated with lysine and arginine and encapsulating ursolic and oleanolic acids (UOACDs) were assumed to be excellent candidates for developing new antibacterial agents, possibly active against Gram-positive species. Indeed, both the guanidine group of arginine and the two triterpenoid acids are items known for directing antibacterial effects, particularly against Gram-positive bacteria. The cationic dendrimers were obtained by peripheral conjugation with the selected amino acids and by entrapping a physical mixture of the commercial triterpenoid acids. The cationic compounds were characterized and successfully tested against 15 Gram-positive isolates. Interesting minimum inhibitory concentration (MIC) values were obtained for all the dendrimer-drug agents, establishing that the antibacterial activity observed for the UOACDs strongly depended on the density and on the type of the cationic groups of the cationic amino acid-conjugated dendrimers and not on the presence and the release of UOA. Particularly, lysine was critical for potency, while arginine was critical for redirecting activity against Gram-positive species. Especially, a high cationic character, associated with a balanced content of lysine/arginine, produced a remarkable antimicrobial effect (MIC = 0.5-8.7 µM).

Antibacterial and ATP Synthesis Modulating Compounds from Salvia tingitana

A surface extract of the aerial parts of Salvia tingitana afforded a nor-sesterterpenoid (1) and eight new sesterterpenoids (2-̵9), along with five known sesterterpenoids, five labdane and one abietane diterpenoid, one sesquiterpenoid, and four flavonoids. The structures of the new compounds were established by 1D and 2D NMR spectroscopy, HRESIMS, and VCD data and Mosher's esters analysis. The antimicrobial activity of compounds was evaluated against 30 human pathogens including 27 clinical strains and three isolates of marine origin for their possible implications on human health. The methyl ester of salvileucolide (10), salvileucolide-6,23-lactone (11), sclareol (15), and manool (17) were the most active against Gram-positive bacteria. The compounds were also tested for the inhibition of ATP production in purified mammalian rod outer segments. Terpenoids 10, 11, 15, and 17 inhibited ATP production, while only 17 inhibited also ATP hydrolysis. Molecular modeling studies confirmed the capacity of 17 to interact with mammalian ATP synthase. A significant reduction of ATP production in the presence of 17 was observed in Enterococcus faecalis and E. faecium isolates.

A Therapeutic Approach in the Treatment of Infections of the Upper Airways: Thiamphenicol Glycinate Acetylcysteinate in Sequential Treatment (Systemic-Inhalatory Route)

Eight hundred and seventeen patients with upper respiratory tract infections were treated with thiamphenicol glycinate acetylcisteinate (TGA) or other standard antibiotics for 6–10 days in a randomised trial. In 419 out of 817 patients, the symptomatology was severe and they were treated with TGA in sequential therapy (TGA 500 mg- as thiamphenicol- b.i.d. intramuscularly on the first day and TGA 500 mg b.i.d by aerosol during the following days) (n=151), or with antibiotics of comparison (n=268) given intramuscularly. In this group the disappearance of the symptomatology with TGA ranged from 90% of the patients with otitis media to 94% in pharyngotonsillitis and rhinosinusitis; in this latter group TGA was significantly better than cefazolin. In 398 patients with mild symptomatology TGA (250 mg - as thiamphenicol- b.i.d.) was given by aerosol (n=149) and the antibiotics of comparison by oral route (n=249). In TGA patients, the disappearance of symptoms was achieved in 87% of those with rhinosinusitis, in 88% of those with pharyngotonsillitis and in 91% of those with otitis media. S. pyogenes, S. pneumoniae and H. influenzae were the most frequently isolated pathogens, and none of the isolated bacteria proved to be resistant to TGA. Microbiological eradication was obtained in TGA groups in a percentage of patients ranging from 90.2 to 96.0% in those with severe forms, and from 86.2 to 91.6% in those with a mild clinical picture. Investigators rated the TGA efficacy as “excellent” in 96–100% of the patients with severe forms and in 85.5%–100% of the patients with mild forms, whereas in the group of patients with rhinosinusitis the comparison of TGA versus other treatment was significantly in favour of TGA. The Investigator rating of treatment tolerability significantly favoured TGA in sequential treatments in comparison to the other antibiotics. No patient dropped out from the trial because of adverse events.

Predicting the Clinical Efficacy of Generic Formulations of Ceftriaxone

Time above MIC (T>MIC) is regarded as the best pharmacokinetic/pharmacodynamic (PK/PD) parameter for predicting the clinical efficacy of cephalosporins. The concentration of non-protein-bound proprietary ceftriaxone (Rocephin, Roche) in body fluids exceeds this PK/PD criterion for the treatment of Streptococcus pneumoniae respiratory infections. However, the pharmaceutical quality of several generic products may be inferior to Rocephin. We have calculated the variations in fluid concentrations of 34 generic formulations of ceftriaxone and, by mathematical modelling, the implications for attainment of recommended PK/PD criteria, specifically: Treatment of S. pneumoniae infections based on the time that non-protein-bound ceftriaxone concentration in pleural fluid exceeds the CLSI (NCCLS) breakpoint of 4 mg/L for identification of resistant isolates. Impact upon Monte Carlo simulations in plasma for the treatment of S. pneumoniae infections based on T>MIC for 50% dosing interval. Rocephin exceeded the required PK/PD parameters at the mean and two standard deviation levels in both investigations. In contrast, most generic products failed to achieve required PK/PD levels in both investigations. As a consequence, some generic formulations of ceftriaxone may increase risks of clinical failure and/or emergence of resistant isolates.

Comparative Activity of Telithromycin Against Macrolide-Resistant Isolates ofStreptococcus pneumoniae:Results of Two Years of the PROTEKT Surveillance Study

The increase in resistance to macrolides has been linked with increasing use of these agents as empirical therapy for community-acquired respiratory tract infections (CARTIs). As part of the ongoing PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin) surveillance program, over 7600 Streptococcus pneumoniae isolates were collected worldwide from 1999-2001 and evaluated for macrolide resistance. Globally, macrolide resistance was 31-33%, with considerable inter-country variation (<10-88%) and particularly high prevalence in the Far East (>71%). In Europe, France had the most resistant isolates (>53%). The highest rates of macrolide resistance were seen in 0-2 year olds. Co-resistance to clindamycin (64%) and all beta-lactams (14-79%) was seen among macrolide-resistant isolates, but >99% of these isolates were susceptible to telithromycin, vancomycin and linezolid. There was considerable variation in the prevalence of erm(B) (56-64%) and mef(A) (30-35%): erm(B) was prevalent in Europe and mef(A) in North America. Globally, 5-7% isolates carried both mechanisms (erm(B)+mef(A)); of these, 47-65% were from South Korea. These double resistance isolates were >90% resistant to the beta-lactams, except amoxicillin-clavulanate. Clindamycin was active against >98% mef(A) but poorly active against erm(B) and erm(B)+mef(A) isolates. Telithromycin, vancomycin and linezolid were highly active (>99.5%) across all three genotypes.

CONCLUSIONS

In vitro, telithromycin, vancomycin and linezolid are highly active against antibiotic-resistant strains of S. pneumoniae. Telithromycin may be a useful therapeutic alternative to macrolides for the treatment of CARTIs.

Efficacy of N-Acetyl-Cysteine in Combination with Thiamphenicol in Sequential (Intramuscular/Aerosol) Therapy of Upper Respiratory Tract Infections Even When Sustained by Bacterial Biofilms

A total of 102 patients with recurrent upper respiratory tract infections underwent microbiological exploration with appropriate sampling and direct biopsies of the infected sites. Therapy was then started and on day 1 each patient received two intramuscular injections of thiamphenicol glycinate acetylcysteinate (TGA). From day 2 to 10 sequential therapy with the same drug was continued employing TGA administered by aerosol. All putative etiologic agents recovered were susceptible to thiamphenicol and only 24 demonstrated the ability to produce in vitro biofilms. The organisms comprised 10 Staphylococcus aureus, 6 Streptococcus pyogenes, 4 Streptococcus pneumoniae and 3 Haemophilus influenzae. Of the 24 subjects in whom biofilms were demonstrated to be present in vivo by Scanning Electron Microscopy, clinical and bacteriological cure was obtained in 21 cases (87.5%) following sequential therapy with TGA. Failures were considered to be persistent signs and symptoms at day 15 after initiation of treatment and lack of eradication of 3 S. aureus strains, despite their in vitro susceptibility to thiamphenicol. Very few adverse events attributable to TGA were reported in this cohort of patients. In no case was discontinuation of treatment deemed necessary by the attending physician.

Antimicrobial Susceptibility Patterns of Contemporary Pathogens from Uncomplicated Urinary Tract Infections Isolated in a Multicenter Italian Survey: Possible Impact on Guidelines

During 2004 four Italian Laboratories assessed the prevalence of antimicrobial resistance among uropathogens causing acute uncomplicated cystitis in female out-patients. A total of 600 urine samples from individuals aged 18-65 were studied. The overall prevalence of Escherichia coli was 85.3%. Klebsiella pneumoniae, Staphylococcus saprophyticus, Proteus mirabilis, Enterococcus faecalis and other rarer species were far less represented. Determination of the antibiotic susceptibility pattern of the entire collection of E. coli (512 organisms) revealed that among the drugs analyzed ampicillin was the least active molecule with only 62.5% of the strains being inhibited. Amoxicillin-clavulanate and cefuroxime displayed a higher potency (87.7% and 89.2% respectively). Cotrimoxazole inhibited only 70.1% of the uropathogens. The three fluoquinolones tested had comparable activity ranging from 83.0% for ciprofloxacin, to 83.6% for levofloxacin and 84.9% for prulifloxacin, indicating an identical spectrum of cross resistance. Nitrofurantoin (96.7%) and fosfomycin (98.6%) were the most potent drugs. Against the whole collection of uropathogens, only cefuroxime, nitrofurantoin and fosfomycin overcame the threshold of 90% activity, with the fluoroquinolones and amoxicillin-clavulanate suffering from about 15% resistance. The results of this survey strongly support the conclusions of recent Italian guidelines concerning the best empiric treatment of UTI in this country today.

Antimicrobial activity of prulifloxacin in comparison with other fluoroquinolones against community-acquired urinary and respiratory pathogens isolated in Greece

Prulifloxacin, the prodrug of ulifloxacin, is a broad-spectrum fluoroquinolone rather recently introduced in certain European countries. We compared the antimicrobial potency of ulifloxacin with that of other fluoroquinolones against common urinary and respiratory bacterial pathogens. The microbial isolates were prospectively collected between January 2007 and May 2008 from patients with community-acquired infections in Greece. Minimum inhibitory concentrations (MICs) were determined for ciprofloxacin, levofloxacin, moxifloxacin (for respiratory isolates only), and ulifloxacin using the E-test method. The binary logarithms of the MICs [log2(MICs)] were compared by using the Wilcoxon signed-ranks test. A total of 409 isolates were studied. Ulifloxacin had the lowest geometric mean MIC for the 161 Escherichia coli, 59 Proteus mirabilis, and 22 Staphylococcus saprophyticus urinary isolates, the second lowest geometric mean MIC for the 38 Streptococcus pyogenes respiratory isolates (after moxifloxacin), and the third lowest geometric mean MIC for the 114 Haemophilus influenzae and the 15 Moraxella catarrhalis respiratory isolates (after ciprofloxacin and moxifloxacin). Compared with levofloxacin, ulifloxacin had lower log2(MICs) against E. coli (p < 0.001), P. mirabilis (p < 0.001), S. saprophyticus (p < 0.001), and S. pyogenes (p < 0.001). Compared with ciprofloxacin, ulifloxacin had lower log2(MICs) against P. mirabilis (p < 0.001), S. saprophyticus (p = 0.008), and S. pyogenes (p < 0.001), but higher log2(MICs) against H. influenzae (p < 0.001) and M. catarrhalis (p = 0.001). In comparison with other clinically relevant fluoroquinolones, ulifloxacin had the most potent antimicrobial activity against the community-acquired urinary isolates studied and very good activity against the respiratory isolates.

DNA bacterial load in children with bacteremic pneumococcal community-acquired pneumonia

This study was conducted to evaluate the association between pneumococcal DNA load and parapneumonic pleural effusion (PPE) in children with community-acquired pneumonia. Bacterial load was quantified and related to the presence of PPE with or without empyema in 72 otherwise healthy children aged ≤5 years who were hospitalised because of radiographically confirmed CAP and showed a real-time polymerase chain reaction that was positive for Streptococcus pneumoniae. The proportion of children with a high bacterial load (i.e. ≥265 DNA copies/mL) was larger among the subjects with PPE than those without it. Multivariate analysis showed that a high bacterial load was significantly associated with PPE (OR 8.65; 95% CI 1.10-67.8 vs a bacterial load of <125 copies/mL). Children with infection due to pneumococcal serotype 19A were at highest risk of developing PPE (OR 7.44; 95% CI 1.10-50.4 vs all other typeable serotypes). The patients with CAP due to pneumococcal serotypes that are not included in the 13-valent conjugate vaccine (PCV13) were more frequently affected by PPE than those with infections associated with serotypes included in the vaccine, except for serotype 19A. Bacterial loads of ≥265 DNA copies/mL are significantly associated with PPE, and serotype 19A is significantly associated with a high bacterial load and the development of PPE. The mean bacterial load of the patients with empyema was higher than that of patients with simple PPE. Although further studies are required, it seems that serotypes not included in PCV13 can play a major role in causing a higher bacterial load and PPE.

Bacteremic pneumococcal community-acquired pneumonia in children less than 5 years of age in Italy

BACKGROUND

This study was designed to determine the proportion of bacteremic pneumococcal cases in a group of pediatric subjects with community-acquired pneumonia (CAP), the importance of the different serotypes and the impact of the currently available pneumococcal conjugate vaccines (PCVs).

METHODS

The study involved children who were ≤5 years with radiographically confirmed CAP admitted to hospital in Italy between September 2008 and March 2011. A diagnosis of laboratory-confirmed bacteremic pneumococcal CAP was made in the presence of a culture and/or real-time polymerase chain reaction (PCR) positive for Streptococcus pneumoniae.

RESULTS

A total of 510 children were included in the study. Pneumococcal CAP was diagnosed in 73 cases (14.3%): S. pneumoniae was identified by means of positive real-time PCR in 67 cases (91.8%), a positive blood culture in 1 (1.4%) and both in 5 (6.8%). Complicated pneumonia was observed significantly more often in the pneumococcal-positive cases (P=0.02) and empyema was the main complication (P=0.007). Serotype 19A was most frequently encountered (17 cases; 25.8%), followed by serotypes 14 (10 cases, 15.1%), 4 (5 cases, 7.6%) and 3 (4 cases, 6.1%). The theoretical coverage offered by the available PCVs was calculated to be 31% for PCV7, 37% for PCV10 and 71% for PCV13.

CONCLUSIONS

In Italy, bacteremic pneumococcal CAP accounts for a significant number of CAP cases in children who were ≤5 years, with serotypes 19A and 14 being the most frequent. This suggests that PCV13 is the best means of preventing pneumococcal CAP.

Detection of Streptococcus pneumoniae and identification of pneumococcal serotypes by real-time polymerase chain reaction using blood samples from Italian children ≤ 5 years of age with community-acquired pneumonia

Streptococcus pneumoniae is a leading cause of severe life-threatening infections. Laboratory identification and serotyping of this pathogens is desirable to monitor vaccine impact and coverage; however, especially in pediatric patients, the yield of traditional microbiological diagnostic procedures can be very low. The aim of this study was to develop real-time polymerase chain reaction (PCR)-based assays to be performed directly on blood samples to identify the most common capsular serotypes causing pneumonia in Italian children (≤ 5 years of ages) after the introduction of the 7-valent conjugate vaccine. Our real-time PCR-based assays showed high sensitivity (at least 35 fg of pneumococcal DNA), and they were validated with 49 well-characterized pneumococcal isolates, 8 nonpneumococcal isolates, 13 simulated blood clinical samples loaded with S. pneumoniae of known serotypes, and 46 blood clinical samples. All the strains tested and the simulated blood clinical samples were correctly typed by the technique. Real-time PCR allowed serotyping in 37/46 children ≤ 5 years of age (80.4%) in whom pneumonia was diagnosed in four Italian hospitals. Non-PCV7 serotypes accounted for at least 47.8% (22/46) of cases, serotype 19A being the most common (34.7%, 16/46). Although, it is not known at present whether the incidence of 19A serotype is attributable to the use of PCV7 only, expanding pneumococcal serotype coverage has clearly the potential to prevent a larger number of pneumonias in Italian children less than ≤ 5 years of age. Molecular methods are of increasing importance in the diagnosis of pneumococcal pneumonia and in monitoring serotype distribution and replacement.

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

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 (MIC(90)values of 0.03 and 0.06 mg/L respectively), showing only a slight decrease in potency on penicillin-intermediate and resistant pneumococci (MIC(90)value 0.5 mg/L, 1.0 mg/L respectively). All the other comparators displayed MIC(90 )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 (MIC(90)0.5 mg/mL). Cefditoren displayed a uniformly potent inhibitory activity (MIC(90)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 MIC(90)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.

Ideal microbiological and pharmacological characteristics of a quality antimicrobial agent: comparing original and generic molecules

This article critically evaluates the main in vitro and in vivo studies published which compare generic with the original molecules, both those administered orally and parenterally. The authors indicate that caution should be used in assuming bioequivalence of the generic drug with its clinical efficacy in clinical practice. In fact, mild differences in the content of the active ingredient, less relevant in healthy volunteers, may have an impact in the actual population, which is heterogeneous for age, sex, weight, concomitant risk factors and severity of the underlying disease, as in critically ill patients, with consequences for the patient and ecosystem. Nowadays the requirements for authorization to commercialize a generic antimicrobial agent are focused on demonstration of bioequivalence to the original molecule, with a range variability of +/-20%. However this kind of trial is not sufficient to predict the actual profile in clinical practice, particularly in critically ill patients. Thus while generics can represent an opportunity for physicians, patients and healthcare systems the regulatory procedures do not seem exhaustive, and it is probably necessary to define an ad hoc technical standard of quality before their commercialization and to perform adequate clinical trials regarding efficacy and safety of the "equivalent molecule", especially for drugs used in critically ill patients.

Activity of daptomycin on biofilms produced on a plastic support by Staphylococcus spp

The aim of this study was to assess whether the novel lipopeptide daptomycin might be capable of disrupting or inhibiting the synthesis of biofilms produced by staphylococci. Fourteen recently isolated slime-producing methicillin-susceptible (MET-S) and methicillin-resistant (MET-R) strains (three MET-S Staphylococcus aureus, three MET-R S. aureus, three MET-S Staphylococcus epidermidis, three MET-R S. epidermidis and two vancomycin-intermediate S. aureus (VISA)) were tested. Slime formation on polystyrene plates was quantified spectrophotometrically. Daptomycin (2-64 mg/L) inhibited slime synthesis by > or =80% in MET-S strains, by 60-80% in MET-R S. aureus and by 70-95% in MET-R S. epidermidis. At 64 mg/L, biofilm synthesis decreased by 80% in the VISA isolates. Daptomycin also disrupted pre-formed biofilm: >50% breakdown of initial biofilm (5h) was observed in all strains. Disruption of mature biofilms (48 h), in terms of percentage, was more variable depending on the strain, ranging from ca. 20% in a MET-R S. epidermidis strain to almost 70% in two MET-S strains (one S. aureus and one S. epidermidis). Daptomycin at concentrations achievable during therapy promoted a statistically significant inhibition of slime synthesis (preventing biofilm building) and induced slime disruption (disaggregating its structure) both in initial and mature biofilms on a plastic support in all staphylococcal strains studied.

Activity of moxifloxacin on biofilms produced in vitro by bacterial pathogens involved in acute exacerbations of chronic bronchitis

The aim of this study was to assess whether moxifloxacin is able to inhibit the synthesis of and to disrupt biofilms produced in vitro by bacterial pathogens involved in acute bacterial exacerbations of chronic bronchitis. Three strains each of Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Staphylococcus aureus and Escherichia coli recently isolated from clinical respiratory specimens and capable of slime production were used. Biofilm formation on polystyrene plates was quantified spectrophotometrically by established methodologies. Moxifloxacin (0.5 mg/L) inhibited slime synthesis by >70% in S. aureus, H. influenzae and S. pneumoniae, 45-70% in E. coli and 35-70% in M. catarrhalis. Disruption of pre-formed structures was also promoted by moxifloxacin both for initial (5h) and mature (48 h) biofilms. Drug concentrations reached during therapy (0.5-4 mg/L) resulted in a breakdown of initial biofilm of 60-80% in H. influenzae and S. pneumoniae, 48-86% in S. aureus, 37-69% in M. catarrhalis and 51-71% in E. coli. Mature biofilms were less susceptible to degradation. Moxifloxacin at concentrations that can be achieved in the bronchial mucosa during therapy therefore promotes a significant inhibition of biofilm synthesis and induces slime disruption, a feature that may be instrumental in reducing the exacerbations so frequently observed in this condition.

In vitro activity of prulifloxacin against Escherichia coli isolated from urinary tract infections and the biological cost of prulifloxacin resistance

Minimum inhibitory concentrations (MICs) and mutant prevention concentrations (MPCs) of prulifloxacin against 30 strains of Escherichia coli isolated from urinary tract infections as well as the 'biological cost' related to acquisition of resistance to the same drug in 10 uropathogenic E. coli were assessed. In terms of MIC(90), prulifloxacin was more potent than ciprofloxacin and levofloxacin. Prulifloxacin produced lower or equal MPC values than the other two fluoroquinolones (93.3% and 73.3% compared with levofloxacin and ciprofloxacin, respectively). Compared with susceptible strains, prulifloxacin-resistant mutants showed a reduced rate of growth (ranging from 20.0% to 98.0% in different culture media and incubation conditions) and a decreased fitness index (ranging from 0.959 to 0.999). They were also impaired in their ability to adhere to uroepithelial cells and urinary catheters (11.7-66.4% and 16.3-78.3% reduction, respectively) and showed a lower surface hydrophobicity (51.2-76.0%). They were more susceptible to ultraviolet irradiation (30.6-93.8% excess mortality), showed increased resistance to colicins and diminished transfer of plasmids (<1-8.5x10(-8) vs. 3.3x10(-7)-2.4x10(-4)). Synthesis of haemolysin and type I fimbriae and production of flagella were also adversely affected. This study demonstrates a strict relationship between acquisition of prulifloxacin resistance and loss of important virulence traits. In this transition, E. coli pays a severe biological cost that entails a general reduction of fitness, thus compromising competition with susceptible wild-type strains in the absence of the drug.

Recent findings from multinational resistance surveys: are we ‘PROTEKTed’ from resistance?

Continual monitoring of antimicrobial resistance rates is essential. Several large surveillance programmes have been established, including the international, longitudinal, multi-centre study PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin). Initiated in 1999, PROTEKT monitors the antibacterial susceptibility of common respiratory tract pathogens. This article reviews the findings from PROTEKT to date and anticipates future trends in antimicrobial resistance. Data from PROTEKT indicate that resistance patterns for Streptococcus pneumoniae and Haemophilus influenzae are changing, with an increasing prevalence of multi-drug resistant genotypes. Resistance to the ketolide telithromycin is very rare, with rates of S. pneumoniae susceptibility remaining >99%. The in vitro activity of telithromycin remains at a high level irrespective of pathogen genotype or phenotype.

Co-prescriptions with itraconazole and fluconazole as a signal for possible risk of drug–drug interactions: a four-year analysis from Italian general practice

PURPOSE

To determine the prevalence of concomitant use of drugs potentially responsible for interactions among itraconazole and fluconazole users in general practice.

METHODS

During the years 1999-2002, we obtained information from the 'Health Search Database', (HSD) an Italian general practice research database. Among a total sample of 457 672 eligible patients, we included those aged >16 years, and whose diagnoses could be classified as mycosis. Itraconazole and fluconazole users were then selected. A potentially drug-drug interaction (DDI) occurred when the use of concomitant drugs were recorded within +/-30 days from the date of the first azoles prescription. Interacting drugs were classified according to the summary of product characteristics (SPC) as provided by the Italian Pharmaceutical Repertory (REFI).

RESULTS

From 18 323 cases of mycosis, we selected 4843 itraconazole and 1446 fluconazole users. Potentially interacting drugs were prescribed in 8.7% of itraconazole and 6.1% of fluconazole users. For itraconazole, calcium channel blockers were the most common interacting drugs (3.3%), followed by statins (1.7%) and clarithromycin (1.3%), whereas gestoden + ethynylestradiol (2.5%) and benzodiazepines (1.8%) resulted as the most common interacting drugs among fluconazole users.

CONCLUSION

Data indicate a relevant prevalence of concomitant use of medications potentially leading to drug interactions among azoles users. Because of the wide use of these medications in general practice, they should be used with clinical monitoring in view of their known side effects as well as their potential risk for drug interaction.

Antibiotic prescribing for acute and recurrent cystitis in primary care: a 4 year descriptive study

OBJECTIVES

To explore the antibiotic prescribing pattern for cystitis and the patient-related variables associated with prescription during a 4 year period among Italian general practitioners (GPs).

METHODS

We obtained information from the 'Health Search Database' (HSD), an Italian general practice research database. From a total sample of 457 672 eligible patients aged >16 years registered up to December 2002, we included those whose diagnoses could be classified as acute (uncomplicated and complicated) and recurrent cystitis. Patients' features and prevalence of antibiotic users were assessed.

RESULTS

Of 35 129 cases diagnosed during the period 1999-2002, 96.0% of them were acute cystitis (39.2% recorded as uncomplicated). The prevalence of cases with acute complicated and uncomplicated cystitis slightly increased during the 4 year period, whereas it remained stable for recurrent cystitis. Most of the cystitis cases reported no diagnostic tests. More than 70% of patients were prescribed with at least one antibiotic, with a 4-fold increased risk of antibiotic use for acute cystitis throughout the study period. The prevalence of antibiotic users reached 86.2% for both acute uncomplicated and complicated cystitis in 2002, and 81.5% for recurrent cystitis. Fluoroquinolones represented the most common antibiotics being prescribed although they markedly decreased during these years. Fosfomycin trometamol use increased dramatically, becoming the first choice for any type of cystitis.

CONCLUSIONS

Data indicate an evident rise in antibiotic use mostly related to fosfomycin trometamol. They also indicate that such a prescriptive trend finds confirmation from the available evidence for acute uncomplicated cystitis, although the management of recurrent cystitis could be further improved.

The importance of the development of antibiotic resistance in Staphylococcus aureus

Hospital- and community-acquired Staphylococcus aureus infections pose a substantial burden in terms of morbidity, mortality and health care costs. The introduction of new antibiotics to counter this pathogen has frequently been closely followed by the emergence of resistant strains. Most significantly, S. aureus isolates resistant to beta-lactams have become common, and many of these are also resistant to beta-lactamase-resistant penicillins. The rapid spread of methicillin-resistant S. aureus (MRSA) clones across the world often results in hospital outbreaks, but implementation of appropriate control measures usually reduces prevalence to sporadic levels. However, the recent emergence of MRSA infections in the community, affecting patients with no established risk factors for MRSA acquisition, is likely to impact significantly on future strategies for control of nosocomial MRSA. In contrast to other antibiotic classes, S. aureus resistance to glycopeptides did not emerge until nearly 40 years after their clinical introduction, and as a result this drug class has remained the mainstay of treatment for MRSA infections. However, a number of vancomycin-intermediate S. aureus isolates have emerged worldwide and four fully resistant S. aureus isolates have been reported in the USA. This raises the concern that the current first-line treatment for MRSA infection may become ineffective in an increasing proportion of cases in the near future. New classes of antibiotic are urgently needed to treat infections with this growing population of multidrug-resistant S. aureus, and the recently introduced oxazolidinone linezolid and the cyclic lipopeptide daptomycin are welcome additions to the ever-narrowing range of therapies effective against this pathogen.

Susceptibility of Streptococcus pneumoniae to penicillin, azithromycin and telithromycin (PROTEKT 1999–2003)

Isolates of Streptococcus pneumoniae collected over the first 4 years of the PROTEKT study were tested for susceptibility to penicillin, azithromycin and telithromycin. A total of 20,750 isolates were collected from 39 countries. Penicillin non-susceptibility rates were stable over the study period; overall, 21.8% of isolates were resistant. Azithromycin resistance increased from 31.0% in Year 1 to 36.3% in Year 4. Resistance rates for penicillin and azithromycin varied between countries and were highest in France, Spain, South Africa, USA and the Far East. Multidrug resistance in S. pneumoniae did not change significantly over the 4 years, with an overall rate of 38.6%. Telithromycin retained good activity against S. pneumoniae (0.1% of isolates resistant), including multidrug-resistant isolates.

Microbiological rationale for the utilisation of prulifloxacin, a new fluoroquinolone, in the eradication of serious infections caused by Pseudomonas aeruginosa

Minimal inhibitory concentrations (MICs) of prulifloxacin were evaluated in comparison with ciprofloxacin, levofloxacin and moxifloxacin against a large collection (N = 300) of Pseudomonas aeruginosa strains characterised according to the CLSI/NCCLS microdilution method. Additional in vitro tests (time-kill curves and mutant prevention concentration (MPC) determinations) were carried out. Assuming a susceptibility breakpoint for prulifloxacin identical to that of ciprofloxacin, the new fluoroquinolone emerged as the most potent antibiotic (72% of susceptible strains versus 65%, 61% and 23% for ciprofloxacin, levofloxacin and moxifloxacin, respectively). Time-kill tests at 4x MIC confirmed the pronounced bactericidal potency of the drug against P. aeruginosa. Amongst the members of the fluoroquinolone class assessed, prulifloxacin produced the lowest MPC values (< or = 4 mg/L). Our in vitro results indicate that prulifloxacin represents the most powerful antipseudomonal drug available today.

Antibiotic susceptibility and serotype distribution in Streptococcus pneumoniae circulating in Italy: results of the SEMPRE surveillance study (2000-2002)

During 2000-2002, 20 clinical microbiology centres collected 1623 Streptococcus pneumoniae isolates. Susceptibility to penicillin, amoxicillin, amoxicillin/clavulanic acid, cefaclor, cefuroxime, cefotaxime, clarithromycin, ciprofloxacin, levofloxacin, rifampicin and teicoplanin was determined locally by the Etest and/or by the microdilution method by three co-ordinating centres. Total resistance to penicillin increased from 15.2% to 16.1% and macrolide resistance increased from 37.9% to 43.7%. Overall, the most effective drugs (>99% susceptible strains) were amoxicillin, amoxicillin/clavulanic acid, levofloxacin and rifampicin. The most frequent serotypes were: 23F (15.8%), 3 (10.8%) 14 (9.1%), 19F (9.1%), 6B (7.2%), 19A (6.9%) and 6A (4.8%). In conclusion, penicillin and macrolide resistance is increasing in Italy, whilst fluoroquinolone currently remains active. The most common serotypes circulating are included in the heptavalent conjugate vaccine, with the exception of type 3.

The Sentinel Project: an update on the prevalence of antimicrobial resistance in community-acquired respiratory Streptococcus pneumoniae and Haemophilus spp. in Italy

A total of 460 Streptococcus pneumoniae and Haemophilus spp. collected from respiratory infections during 2000 was tested for their susceptibility to 15 selected antibiotics. Overall, penicillin resistance among pneumococci was 10.5%, while lack of susceptibility to macrolides, co-trimoxazole, tetracycline and chloramphenicol reached 35.2%, 26.2%, 22.6% and 6.0%, respectively. Amoxicillin/clavulanic acid and levofloxacin were the most potent compounds (100% and 99.9% susceptible strains, respectively). Among isolates of Haemophilus influenzae and Haemophilus parainfluenzae, beta-lactamase production (12.5% and 10%, respectively), and co-trimoxazole (19.9% and 40.0%) and clarithromycin (11.2% and 40.0%) resistance were the prevalent threats. This study confirms the trend observed in Italy since 1992: macrolide resistance among respiratory microorganisms is increasing, while several drugs including amoxicillin/clavulanic acid, third generation injectable cephalosporins and fluoroquinolones remain active on the great majority of these pathogens.

Antimicrobial susceptibility profiles of Pseudomonas aeruginosa and Staphylococcus aureus isolated in Italy from patients with hospital-acquired infections

Here we report the results of the Sentinel Project 2000 and give the susceptibility to selected antibiotics of 108 Pseudomonas aeruginosa and 108 Staphylococcus aureus strains isolated from patients with hospital-acquired lower respiratory tract infections. In P. aeruginosa, susceptibility to aztreonam and ciprofloxacin was lower than 50%. The resistance rate to beta-lactams was up to 25% and to amikacin 15.7%. Blood isolates showed 80-90% susceptibility to all antibiotics tested except for aztreonam and tobramycin. Overall, oxacillin resistance in S. aureus was 45%, reaching 64.3% among the bronchoalveolar lavage isolates, and 42.9% among the blood isolates. These worrying results confirm the need for continuous monitoring of bacterial resistance trends in the hospitals, mainly in ICUs.

In vitro fluconazole susceptibility of 1565 clinical isolates of candida species evaluated by the disk diffusion method performed using NCCLS M44-A guidelines

We determined the in vitro activity of fluconazole against 1565 clinical Candida spp. isolates collected from different specimens of non-AIDS outpatients and inpatients in 3 different regions of Italy. Susceptibility testing was performed by agar disk diffusion using the NCCLS document M44-A guidelines. Candida albicans was the most frequently isolated yeast (68%) followed by C. glabrata (15%), C. tropicalis (5%), C. parapsilosis (5%), and C. krusei (5%). Other yeasts represented 4% of all isolates. Of the 1565 isolates tested, 1449 (92.6%) were susceptible (S) to fluconazole, 43 (2.7%) were susceptible dose-dependent (S-DD) and 73 (4.7%) were resistant (R). Almost all (98.2%) of the C. albicans isolates were classified as S or S-DD. Despite its widespread use, fluconazole displayed good activity against the isolates we tested, and the disk diffusion method was confirmed as a reliable approach to the evaluation of in vitro susceptibility of yeasts to this antimycotic agent.

In vitro activity of ertapenem against selected respiratory pathogens

OBJECTIVES

The in vitro activity of ertapenem was evaluated in comparison to 21 selected agents against a large collection of recently isolated respiratory tract pathogens including: 180 Streptococcus pneumoniae, 100 Streptococcus pyogenes, 70 Haemophilus influenzae, 70 Moraxella catarrhalis, 100 methicillin-susceptible Staphylococcus aureus and 30 Klebsiella pneumoniae. Additional in vitro tests (time-kill curves with ertapenem alone and in combination with four other agents) for S. pneumoniae were carried out.

METHODS

MIC determinations and time-kill curves were carried out following the procedures suggested by the NCCLS.

RESULTS

According to NCCLS susceptibility breakpoints, ertapenem was comparable to the most potent compounds tested for all pathogens studied. Ertapenem was 100% active against penicillin-susceptible and -intermediate S. pneumoniae and against 60% of penicillin-resistant strains. Time-kill tests at 4x MIC confirmed a pronounced bactericidal potency of ertapenem against these organisms. Interactions of ertapenem with several other agents against pneumococci resulted in clear synergic interactions (98.4%). Indifference was extremely rare and antagonism was not observed. All S. pyogenes strains tested were inhibited by ertapenem, irrespective of their macrolide resistance phenotypes. Ertapenem was also fully active against H. influenzae (100% susceptible) and M. catarrhalis (MIC90 0.015-0.03 mg/L) even when capable of synthesizing beta-lactamases. Methicillin-susceptible S. aureus and K. pneumoniae, including extended-spectrum beta-lactamase-producing strains, were 100% susceptible to ertapenem.

CONCLUSIONS

Our results indicate that ertapenem has a suitable spectrum of activity against organisms encountered in community-acquired bacterial respiratory tract infections.

Effect of fosfomycin alone and in combination with N-acetylcysteine on E. coli biofilms

Four slime-producing uropathogenic Escherichia coli strains were used to investigate the activity of fosfomycin and N-acetylcysteine (NAC) against biofilms developed on 96-well polystyrene tissue culture plates. Biofilms aged, respectively, 5 (initial) and 48 h (mature) and two fosfomycin concentrations (128 and 2000 mg/l) were used. The effect of various levels (0.007-8 mg/ml) of NAC alone and in combination with fosfomycin on the formation or disruption of biofilms was assessed. Following exposure to the drugs, the percentage of residual slime relative to the control, ranged from 62.5-100 to 26.2-64.1% in the presence of 0.007 and 8 mg/ml of NAC. After treatment of pre-formed biofilms with NAC at the highest concentrations used, the remaining exopolysaccharide matrix was reduced to 25-68% of the amount found with the untreated control. Exposure to fosfomycin at 2000 mg/l reduced biofilms 40-57 and 41-49% for the initial and mature forms, respectively. Fosfomycin was more active at 2000 mg/l combined with NAC 2 mg/ml. Under these conditions initial and mature biofilms were reduced 66-80 and 60-73%, respectively. NAC, when used in combination, enhanced fosfomycin bactericidal activity producing a 99-99.9% reduction in viable cells. Fosfomycin and NAC at concentrations achievable in urine displayed a synergistic effect promoting both the formation of biofilms and reduction of sessile cell viability.

Why fosfomycin trometamol as first line therapy for uncomplicated UTI?

Uncomplicated urinary tract infection (UTI) is one of the most common conditions requiring diagnostic and therapeutic intervention. The aetiology and the treatment of these infectious diseases have changed little during last years of the 'antibiotic era'. Escherichia coli is the most prevalent uropathogen (85->90%) and treatment is aimed at eradicating the infection using shorter regimes that typically may employ a 3-day course with once-a-day dosing of a selected drug or a single dose of a particular efficacious antibiotic. Antibiotic resistance to commonly used agents, such as trimethoprim and ampicillin, often now exceeds 30-50%, while fosfomycin trometamol, despite many years of usage, continues to be characterized by an extremely low incidence of E. coli resistant strains (about 1%) worldwide. Many factors may have contributed to preserve fosfomycin trometamol antibacterial activity including single dose usage limited to urinary infections, very high and sustained urinary concentrations that rapidly kill bacteria reducing the opportunity for mutant selection. In addition there is no animal feed that contains the drug, resistance is most commonly acquired by chromosomal mutations that do not spread easily and the biological cost of these genetic modifications is high. To these parameters fosfomycin trometamol adds excellent tolerability and safety. Although nowadays, microbial resistance limits available resources and some drugs can no longer be recommended as reliable agents, fosfomycin trometamol, because of its properties, remains a drug of choice for the eradication of uncomplicated UTI.

In vitro activity of fosfomycin against Gram-negative urinary pathogens and the biological cost of fosfomycin resistance

The aim of this study was to reassess the activity of fosfomycin against recently isolated uropathogens circulating in Italy and to evaluate the effect of fosfomycin resistance on the expression of several virulence traits using the rare mutant strains. In vitro activity of fosfomycin was evaluated using 441 Gram-negative organisms isolated from patients with uncomplicated urinary tract infections (UTIs). Fosfomycin was the most active antibiotic against Escherichia coli (99% susceptibility). The activity against Proteus mirabilis was more potent than that of co-trimoxazole and nitrofurantoin (87.5, 67 and 0% susceptibility, respectively). The other microorganisms, accounting for about 7% of all pathogens tested, showed variable susceptibilities to fosfomycin. Compared with susceptible strains, fosfomycin-resistant mutants showed a reduced rate of growth and were impaired in their ability to adhere to uroepithelial cells and to urinary catheters. They were also more resistant to UV irradiation and to phage T7 and showed diminished rates of colicin synthesis and transfer of plasmids.

Antibacterial resistance in Streptococcus pneumoniae and Haemophilus influenzae from Italy and Spain: data from the PROTEKT surveillance study, 1999-2000

Antibacterial resistance was evaluated among Streptococcus pneumoniae (n=252) and Haemophilus influenzae (n=202) from two centres in Spain (Barcelona and Madrid) and two centres in Italy (Genoa and Catania) collected during 1999-2000 as part of the ongoing PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin) international surveillance program. Pneumococcal nonsusceptibility to penicillin G was found to be considerably higher in Spain (53.4%) than in Italy (15.1%), whereas erythromycin A resistance was higher in Italy (42.9%) than in Spain (28.6%). Among macrolide-resistant isolates investigated for resistance genes, the prevalence of mefA was higher among isolates from Italy (20/51, 39.2%) than among Spanish isolates (2/38, 5.3%). All other macrolide-resistant isolates possessed ermB. Telithromycin possessed good anti-pneumococcal activity against isolates from both countries (MIC90 0.03 mg/L [Spain]; 0.25 mg/L [Italy]), irrespective of resistance to other antibacterials. Beta-lactamase production among H. influenzae was low: Spain, 10.9%; Italy, 1.8%. With the exception of ampicillin and co-trimoxazole, all H. influenzae isolates were highly susceptible to the antibacterials tested, and all were inhibited by telithromycin at a concentration of < or = 2 mg/L. The findings of PROTEKT 1999-2000 highlight the importance of local resistance patterns in guiding the choice of empirical antibacterials for community-acquired respiratory tract infections.

Is antimicrobial resistance also subject to globalization?

In recent years one of the more alarming aspects of clinical microbiology has been the dramatic increase in the incidence of resistance to antibacterial agents among pathogens causing nosocomial as well as community-acquired infections. There are profound geographic differences in the incidence of resistance among pathogens of the respiratory tract, only some of which can be explained by the local use of antibiotics. A high percentage of Moraxella catarrhalis strains produce beta-lactamase and are thus resistant to many beta-lactam antibiotics. In contrast, beta-lactamase production among strains of Haemophilus influenzae rarely reaches more than 30% around the world. Methicillin-resistance in Staphylococcus aureus is a common and increasing problem in hospitals but its extent varies both locally and nationally. Resistance is usually associated with the local spread of resistant strains. High standards of hygiene in hospitals can prevent the spread of such strains but once established they can be difficult to eradicate. Although Streptococcus pyogenes remains highly susceptible to penicillins, even after many decades of their use, resistance to macrolides has occurred. This resistance can rise and fall. Although the increase of macrolide resistance in S. pyogenes can often be associated with an increase in the use of these drugs, this is not always so. In some cases it has been shown to be caused by the spread of one or more resistant clones. Eradication of these clones can reduce the level of resistance markedly. Resistance to both macrolides and penicillins among strains of Streptococcus pneumoniae is seen world-wide but is highly variable from country to country. Local habits of drug usage may play a part. In Italy, for example, there is preference for the use of parenteral third-generation cephalosporins for some severe infections and there is a corresponding low level of penicillin-resistance among pneumococci.

A human placental polydeoxyribonucleotide (PDRN) may promote the growth of human corneal fibroblasts and iris pigment epithelial cells in primary culture

The optimal concentration of a human placental polydeoxyribonucleotide (PDRN) preparation (100 microg/ml) enhances the growth of human corneal fibroblasts in primary culture depending upon the donor age. In particular, this effect is very consistently reproducible with donors over 60 years of age (p = 0.0028), suggesting a selective benefit of PDRN in the tissue culture of senescent cells. Moreover, this drug may promote the development of human iris pigment epithelium (IPE) cells with much lower concentrations of fetal bovine serum than those suitable for the culture of IPE. Lastly, the use of a 'gauze disk' on the pieces of the corneal explants improves the efficiency of growth of the control fibroblast primary cultures.

Postantibiotic effect and delay of regrowth in strains carrying mutations that save proteins or RNA

The postantibiotic effect (PAE) values found for proteinase-defective (Lon(-)) Escherichia coli and RNase-defective E. coli exposed to antibiotics were reduced (31 to 60% and 35 to 50%, respectively) in comparison with the control (AB1157), and in the recA13 mutant these values were about 0.4 h with all drugs. Nalidixic acid, under anaerobic conditions, induced no PAE (0 to 0.1 h) in AB1157. A delay in regrowth (0.2 to 0.26 h) was noted with dnaA46(Ts), gyrA43(Ts), and gyrB41(Ts) mutants cultured for 2 h at 43 degrees C. These findings suggest that when proteins and RNA are saved, the cell rapidly resumes the original growth rate.

Antibacterial activity of oral antibiotics against community-acquired respiratory pathogens from three European countries

Antimicrobial resistance is universally recognized as a major problem. A European resistance survey was established to monitor the activity of widely used oral antibiotics against common respiratory tract pathogens. Studies were conducted in Italy, Spain and Austria to monitor resistance patterns among respiratory Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pyogenes, Staphylococcus aureus and Klebsiella pneumoniae to amoxicillin, co-amoxiclav, penicillin, cefaclor, cefadroxil, cefalexin, cefprozil, cefuroxime, cefixime, ceftibuten, cefpodoxime, clarithromycin and azithromycin (the antibiotics tested varying slightly from country to country). Minimum inhibitory concentrations were determined using the NCCLS-recommended broth microdilution method. Among the antibiotics tested, cefpodoxime, an oral cephalosporin, was remarkably active against the major respiratory pathogens in all three countries. Cefpodoxime was more potent than cefaclor, cefixime and ceftibuten against pneumococci, especially against strains with decreased sensitivity to penicillin, and more active than cefaclor and cefuroxime against Gram-negative respiratory pathogens. Pneumococci and staphylococci displayed a very high level of in vitro macrolide resistance. These data indicate that cefpodoxime represents an appropriate choice in the treatment of community-acquired respiratory tract infection in the three countries surveyed.

Prevalence of antimicrobial resistance in Streptococcus pneumoniae circulating in Italy: results of the Italian Epidemiological Observatory Survey (1997-1999)

The Italian Epidemiological Observatory (IEO), a surveillance program supported by the SmithKline Foundation, analyzed the susceptibility of 2,664 community-acquired respiratory Streptococcus pneumoniae derived from over 50 clinical microbiology laboratories during 1997-1999, against 21 antibiotics adopting a quantitative methodology. Throughout these years, total penicillin resistance varied from 14.3% to 10.2%. High-level resistance has remained stable, ranging from 3.8% to 4.1%, while a decrease in low-level resistance (from 10.3% to 6.1%) has been recorded. Lack of susceptibility to macrolides ranged from 29.1% in 1997 to 25.5% in 1999. Similar figures have also been observed with tetracycline and co-trimoxazole (rates of resistance around 30%). As expected, large geographical variations in resistance rates were found for all drugs. Amoxicillin and amoxicillin-clavulanate were 100% active on penicillin-intermediate isolates. Injectable third-generation cephalosporins and carbapenems were also capable of inhibiting a large proportion of these microorganisms. Rifampin was the most potent non-beta-lactam compound tested. In contrast to the situation prevailing elsewhere, in Italian children (aged 0-5 years) presenting with respiratory conditions, the total rate of penicillin resistance (3%) was lower than that shown by the adult population (10.9%). However, lack of susceptibility to macrolides, tetracycline, and cotrimoxazole (35%, 41%, 44%) was more incident in pediatric than in adult patients (25%, 26%, 28% respectively). Strains recovered from blood in 1999 (67) were much more susceptible to penicillin (98.5%) than respiratory pneumococci (89.8%), whereas macrolides, tetracycline, and cotrimoxazole were consistently less active (75%, 67%, 64%).

Nasopharyngeal carriage of Streptococcus pneumoniae in healthy children: implications for the use of heptavalent pneumococcal conjugate vaccine

We assessed the prevalence of Streptococcus pneumoniae serotypes in the nasopharynx of healthy children, antimicrobial susceptibility patterns, risk factors for carriage, and the coverage of heptavalent pneumococcal conjugate vaccine. In 2,799 healthy infants and children, the S. pneumoniae carrier rate was 8.6% (serotypes 3, 19F, 23F, 19A, 6B, and 14 were most common). Most pneumococci (69.4%) were resistant to one or more antimicrobial classes. The rate of penicillin resistance was low (9.1%); macrolide resistance was high (52.1%). Overall, 63.2% of the isolates belonged to strains covered by the heptavalent pneumococcal vaccine. This percentage was higher in children <2 years old (73.1%) and in those ages 2-5 years (68.9%). Sinusitis in the previous 3 months was the only risk factor for carrier status; acute otitis media was the only risk factor for the carriage of penicillin-resistant S. pneumoniae. Most isolated strains are covered by the heptavalent conjugate vaccine, especially in the first years of life, suggesting that its use could reduce the incidence of pneumococcal disease.

The oxazolidinones as a new family of antimicrobial agent

The oxazolidinones are a new chemical class of synthetic antmicrobials characterized by a unique mechanism of protein synthesis inhibition. Linezolid is the first compound of this class and has recently received approval for the treatment of community- and hospital-acquired pneumonia and skin and skin structure infections. In vitro tests demonstrate that linezolid possesses a significant activity against Gram-positive pathogens including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), vancomycin-intermediate strains (VISA) and penicillin-resistant pneumococci (PRPN). Combined with other drugs linezolid interacts favourably against many important pathogens and it is able to affect some bacterial virulence factors as well as produce a postantibiotic effect. Results from experimental models of infection reveal linezolid to be highly active in vivo against infections due to Gram-positive pathogens. Linezolid may be administered either intravenously or orally with oral bioavailability of approximately 100% and limited adverse effects. The clinical efficacy of linezolid has been investigated in several phase II and III trials. Linezolid has been proved to be useful in severe infections sustained by multiresistant Gram-positive micro-organisms. Synthesis of the second-generation oxazolidinones with improved potency against Gram-positive and negative bacteria is currently under way.

Multicentre evaluation of the VITEK 2 Advanced Expert System for interpretive reading of antimicrobial resistance tests

Interpretive reading analyses the complete resistance profiles of bacteria to multiple antibiotics and infers the resistance mechanisms present; it aids therapeutic choice and enhances surveillance data. We evaluated the Advanced Expert System (AES), which interprets MICs generated by the VITEK 2. Ten European laboratories tested 42 reference strains and 76-106 of their own strains, representing important resistance genotypes. Interpretive reading by the VITEK 2 AES achieved full agreement with genotype data for 88-89% of strains, with the correct mechanism identified as one of two possibilities for a further 5-6%. Mechanisms inferred with 90% agreement with reference data included methicillin resistance in staphylococci, glycopeptide resistance in enterococci, quinolone resistance in staphylococci and Enterobacteriaceae, AAC(6')-APH(2")-mediated aminoglycoside resistance in Gram-positive cocci, erm-mediated macrolide resistance in pneumococci, extended-spectrum beta-lactamases (ESBLs) in Enterobacteriaceae and Pseudomonas aeruginosa, and acquired penicillinases in Enterobacteriaceae. VanA, VanB and VanC phenotypes of enterococci were distinguished reliably, and ESBL production was accurately inferred in AmpC-inducible species as well as Escherichia coli and Klebsiella spp. Mechanisms identified, but only as possibilities among several, included IRT-type beta-lactamases and individual aminoglycoside-modifying enzymes in Enterobacteriaceae. Most disagreements with reference data concerned pneumococci found to have high-level penicillin resistance by the VITEK 2 AES but previously determined, phenotypically, to have intermediate resistance. When ESBL production was inferred in E. coli and klebsiellae, the VITEK 2 AES edited susceptible results for cephalosporins (except cefoxitin) to resistant; when an acquired penicillinase was inferred in Enterobacteriaceae, piperacillin results were edited to resistant; and when staphylococci were found methicillin resistant, resistance was reported for all beta-lactams. Further editing may be desirable (e.g. of cephalosporin results for salmonellas inferred to have ESBLs).

Seasonal variations in nasopharyngeal carriage of respiratory pathogens in healthy Italian children attending day-care centres or schools

The aim of this study was to investigate seasonal variations in the prevalence of the nasopharyngeal carriage of respiratory pathogens and identify factors affecting colonisation patterns in healthy children. The nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis during two seasons (autumn and spring) was evaluated in 1580 healthy children aged 1-7 years by means of a cohort study conducted in day-care centres and schools in eight Italian cities. A questionnaire was used to obtain the epidemiological data. In all, 309 children (19.5%) carried one or more respiratory pathogens in the autumn, and 375 children (23.7%) in the spring. This variation was due to H. influenzae alone or in combination (autumn: S. pneumoniae 60, 3.8%; H. influenzae 206, 13.0%, M. catarrhalis 71, 4.5%; spring: S. pneumoniae 75, 4.7%; H. influenzae 288, 18.2%, M. catarrhalis 82, 5.2%). Colonisation with two or more pathogens increased from 9.1% in the spring to 17.3% in the autumn. Seasonal variations occur in the prevalence of the nasopharyngeal carriage of respiratory pathogens in healthy children attending day-care centres or schools in Italy. However, although statistically significant, the difference was slight and had limited clinical relevance. Therefore, seasonal influence on the nasopharyngeal carriage of respiratory pathogens in healthy children was negligible.

Epidemiology of major respiratory pathogens

A vast literature attests to the fact that Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis represent the prevailing bacterial pathogens of community-acquired lower respiratory tract infections. Their specific incidence as causative agents of the more common syndromes is known to vary even profoundly, depending on geographic area, and the same holds true for their rates of resistance to antimicrobial drugs. Europe does not escape the threat posed by the present pandemic spread of penicillin resistance in S. pneumoniae although, as expected, some countries like Spain and France are highly affected and others including Germany, Italy, The Netherlands and the Scandinavian region, are relatively spared. In several sites multiple resistance has been described in S. pneumoniae with the most affected drugs being penicillin, the macrolides, co-trimoxazole and tetracycline. In H. influenzae synthesis of beta-lactamases is the main resistance trait expressed. Lack of susceptibility to beta-lactams dictated by a different mechanism remains extremely rare. Large variations in the incidence of this character are apparent when considering European countries. France and Spain are again widely affected while Germany, The Netherlands and Italy display rates of beta-lactamase-positive H. influenzae of about 16%. M. catarrhalis must be considered generally resistant to non-protected aminopenicillins since over 90% of these organisms produce beta-lactamases.

Microbial epidemiology patterns of surgical infection pathogens

Resistance, as assessed in vitro, has a number of serious consequences in clinical situations. Treatment failures are common when an inappropriate drug has been prescribed and this, in turn, may lead to hospitalization of patients who normally would have been treated on an outpatient basis, as well as to longer hospital stay for inpatients and to the use of alternative drugs, which may be more expensive and more toxic. These factors all contribute to increased health care costs, morbidity and mortality. Microbiological procedures may identify the causative pathogen and provide the appropriate susceptibility pattern to the physician, thus reducing the chances of therapeutic failures. However, for a number of reasons including cost--even in hospitals--not to mention general practice, infections are seldom diagnosed on an etiological basis. From what has been stated, the knowledge of bacterial epidemiology and resistance represents basic support for correct therapeutic decision-making.

Evaluation of spontaneous contamination of ocular medications

BACKGROUND

In order to evaluate whether single-dose ophthalmic preparations in 0.5-ml containers can safely be used within 24 h after the first opening, eigth different sterile ocular medications containing timolol, jaluronic acid, diclofenac, ketotifen, pilocarpine, formocortal, formocortal-gentamycin, and tetryzoline-feniramine (Farmigea, Italy) were opened and tested for spontaneous bacterial contamination after exposure to air.

METHODS

Samples (10 microl) were collected from exposed ophthalmic preparations after 0, 2, 4, 8 and 24 h.

RESULTS

No viable microorganisms were detected during and at the end of the evaluation period. In order to assess whether the resident or pathogenic ocular bacterial population due to repeated handling might contaminate the medications, about 10(5) cells of different species (Staphylococcus aureus, coagulase-negative staphylococci, Streptococcus pneumoniae, Streptococcus spp., Corynebacterium spp., Pseudomonas aeruginosa, Neisseria spp., Acinetobacter spp., Haemophilus influenzae, Escherichia coli and Candida albicans) were added to the containers and incubated at 37 degrees C or at room temperature. Samples were collected and the number of viable bacteria was estimated. The antibacterial effect of the ophthalmic compounds varied depending on the species considered. Tetryzoline-feniramine, pilocarpine, ketotifen and formocortal-gentamycin exhibited a frank bactericidal activity (<100 survivors after 18-24 h of exposure) against the great majority of the species tested.

CONCLUSION

These results indicate that the risk of spontaneous contamination of ophthalmic preparations after their first opening is low, and that all preparations tested exhibit an aspecific antibacterial activity. As a consequence, the safe usage of these ocular medications could be extended from the recommended 3 h to at least 24 h after the first usage.

[Epidemiology of methicillin-resistance among Staphylococci strains isolated in risk units and effects of the vancomycin on the expression of methicillin-resistance]

Four hundred Staphylococci strains, isolated from different in intensive care unit hospitalized patients, were analyzed. 53% of all strains were resistant to methicillin. Against methicillin-resistant S. aureus (MRSA), teicoplanin and vancomycin (100% of susceptibility), rifampin (76.3%) and co-trimoxazole (73%) emerged as the most potent drugs tested; the 15% of the strains were susceptible to ciprofloxacin, erythromycin, clindamycin and gentamicin. Only one MRSA strain (0.8%) resulted hetero-resistant to vancomycin. Among 100 strains exposed to serial concentration of vancomycin (0.25-32 mg/L for 30 days), 57 were selected with intermediate-level of resistance to the glycopeptides; the MRSA strains have shown to acquire resistance in vitro more easily than methicillin-susceptible. These results indicate that in the clones of Staphylococci circulating in our region, the evolution of glycopeptides-resistance is not a rapid process and the loss of effectiveness of these antibiotics cannot be predicted to short term. In particular, the restriction profile analysis of chromosomal DNA from MRSA strains, selected in vitro with intermediate -level of vancomycin resistance, demonstrated that at the moment in the hospital departments studied, the diffusion of a clone able to acquire resistance more easily than others is not present.