Prevention of nosocomial legionellosis by best water management: comparison of three decontamination methods.

BACKGROUND: Since 2000, the National Health System has adopted international guidelines for assessing Legionella spp. in hospital water systems. The control of water contamination by Legionella spp. is still a matter of research concerning the most effective method in preventing nosocomial infections. AIM: To compare three different decontamination methods by monitoring colony-forming unit count and number of hospital-acquired legionellosis cases. A secondary objective was to evaluate the long-term effects of the preventive measures on the water pipes. METHODS: A protocol was developed for the selection of high-risk sampling sites and for the testing of three disinfection methods over the course of 19 years: hyperchlorination and thermal shock (period A, 2000-2005); copper-silver ionization (period B, 2006-2010); and integration of pre-filtering, filtering, pipe-protecting products, and remote control with chlorine dioxide (ClO2) (period C, 2011-2018). FINDINGS: The use of shock disinfection and hyperchlorination led to a decrease in contamination level immediately after the procedure, but then it rose again to the previous level in two months. Both copper-silver ionization and ClO2 disinfection showed a stable and durable decrease in contamination level. Throughout these three phases, six cases of Legionella spp. occurred during period A, six cases during period B, and three cases during period C. With regard to the damage of water pipes, effective copper-silver levels caused corrosion and calcification in water pipes. CONCLUSION: Both copper-silver ionization and ClO2 properly controlled Legionella spp. contamination. ClO2 significantly reduced the number of positive sites (P < 0.001) without damaging the pipelines.

Catheter-related bacteremia due to Lactobacillus rhamnosus in a single-lung transplant recipient.

There is still a major debate about the pathogenicity of Lactobacillus spp. and some reports emphasize that these microorganisms are never isolated from endovascular devices. In this report we present a case of catheter-related bacteremia due to L. rhamnosus in a patient who underwent a single-lung transplant.

Antibiotic-impregnated fibrin glue in ocular surgery: in vitro antibacterial activity.

A strategy to reduce postoperative ocular infections might consist in maintaining a high antibiotic concentration in the eye by using a topical slow-release drug formulation. Fibrin glue is widely used in ocular surgery. Vancomycin, teicoplanin, cephalothin and gentamicin were added to a 500 IU/ml thrombin solution, their concentrations in 1 g fibrin glue being 500 microg for vancomycin and 400 microg for the other drugs. The in vitro antibacterial activity of antibiotic-impregnated fibrin glue was evaluated against a recent clinical isolate of Staphylococcus epidermidis. Moreover the antibiotic elution from fibrin discs in saline was assayed for up to 96 h. Fibrin glue properties were maintained when thrombin was reconstituted with a CaCl2 solution additioned with the antibiotics tested. All antibiotic fibrin mixtures exhibited good antistaphylococcal activity immediately after the preparation. A prolonged inhibition (4 days) of S. epidermidis growth was observed with teicoplanin discs. Gentamicin and teicoplanin levels were higher than those of the other antibiotics. The results suggest that the fibrin glycopeptide and/or gentamicin mixtures can be used, both prophylactically and therapeutically, in ocular surgery.

Comparative in vitro activity of silver sulfadiazine, alone and in combination with cerium nitrate, against staphylococci and gram-negative bacteria.

Silver sulfadiazine (SSD), a topical antimicrobial agent, has been widely used for the prophylaxis and treatment of burn infections during the past 30 years. We determined the antimicrobial activity of SSD, alone and in combination with cerium nitrate (CN), gentamicin and amikacin against 130 recent clinical isolates, including multiresistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa. The overall activity of SSD was good against all the tested strains and it was particularly high against MRSA (MIC90 100 microg/ml). CN showed no inhibitory effect, even up to 800 microg/ml, on bacterial strains tested. The combination of SSD and CN was as active as SSD alone. In conclusion, SSD has a broad spectrum of activity at concentrations lower than those commonly used in clinical preparations. All strains were inhibited by less then one-fiftieth of the SSD "in use" concentration (10 mg/ml). Our data confirm the efficacy of this topical agent in the prevention and treatment of infections in burns or other surgical wounds and suggest its possible use in clearing staphylococcal carriage as an alternative to mupirocin.

Introduction of the mec element (methicillin resistance) into Staphylococcus aureus alters in vitro functional activities of fibrinogen and fibronectin adhesins.

Some methicillin-resistant strains of Staphylococcus aureus are defective in the production of major surface components such as protein A, clumping factor, or other important adhesins to extracellular matrix components which may play a role in bacterial colonization and infection. To evaluate the impact of methicillin resistance (mec) determinants on bacterial adhesion mediated by fibrinogen or fibronectin adhesins, we compared the in vitro attachment of two genetically distinct susceptible strains (NCTC8325 and Newman) to protein-coated surfaces with that of isogenic methicillin-resistant derivatives. All strains containing an intact mec element in their chromosomes were found to be defective in adhesion to fibrinogen and fibronectin immobilized on polymethylmethacrylate coverslips, regardless of the presence or absence of additional mutations in the femA, femB, or femC gene, known to decrease expression of methicillin resistance in S. aureus. Western ligand affinity blotting or immunoblotting of cell wall-associated adhesins revealed similar contents of fibrinogen- or fibronectin-binding proteins in methicillin-resistant strains compared to those of their methicillin-susceptible counterparts. In contrast to methicillin-resistant strains carrying a mec element in their genomes, methicillin-resistant strains constructed in vitro, by introducing the mecA gene on a plasmid, retained their adhesion phenotypes. In conclusion, the chromosomal insertion of the mec element into genetically defined strains of S. aureus impairs the in vitro functional activities of fibrinogen or fibronectin adhesins without altering their production. This effect is unrelated to the activity of the mecA gene.

Ocular infections: antibiotics and bacterial adhesion on biomaterials used in ocular surgery.

The in vitro antibacterial activity of ofloxacin, sagamycin and other antibiotics was evaluated against 85 bacterial isolates [coagulase-negative staphylococci (CNS), n = 37, Staphylococcus aureus, n = 28, and Pseudomonas aeruginosa, n = 20] obtained from patients with ocular infections. The antistaphylococcal activity of ofloxacin was quite elevated with a 90% minimal inhibitory concentration (MIC90) of 1.56 mg/l against CNS and S. aureus. Rokitamycin and erythromycin showed a good activity against methicillin-sensitive staphylococci, but were less active than ofloxacin and sagamycin against methicillin-resistant strains (MIC90 > 100 mg/l). Sagamycin was highly effective against staphylococci (MIC90 0.78 mg/l) and appeared to be the most active compound against P. aeruginosa (MIC90 6.25 mg/l), followed by ofloxacin, tobramycin and gentamicin. In a successive part of the study, the adhesive properties of slime-producing staphylococci were tested on biomaterials used in ocular surgery. Intraocular lenses, Silastic sheetings, circling bands and grooved strips showed a high affinity for slime-producing strains, while round silicone sponges were not covered by bacterial biofilm. In the last part of our study, we demonstrated how subMIC levels of ofloxacin increased the adhesion of slime-producing staphylococci. Our data confirmed the excellent activity of ofloxacin and sagamycin against ocular pathogens and the key role of adhesion in promoting colonization and infections of biomaterials.

Activity of daptomycin against enterococci and coagulase-negative staphylococci (CNS): relationship between CNS susceptibility and slime production.

We compared the in vitro activity of daptomycin, a new lipopeptide antibiotic, with that of vancomycin and other selected agents against 95 coagulase negative staphylococci (CNS) isolates causing septicemia or foreign-body infections in immunocompromised patients. These strains were classified as follows: 51 methicillin-susceptible CNS (23 slime producers); 44 methicillin-resistant CNS (23 slime producers). We also investigated the activity of daptomycin against 50 Enterococcus faecalis isolates. Minimal inhibitory concentrations (MICs) were determined by the broth microdilution method. Daptomycin at a concentration of 2 mg/L was inhibitory for all the evaluated strains. Vancomycin and ciprofloxacin showed good activity: 90% of the strains were inhibited by these agents at 8 mg/L. The activity of netilmicin, rifampin and trimethoprim-sulfamethoxazole was instead limited. Resistance to the antimicrobial agents tested was seen with increased frequency among slime producing strains. Daptomycin and teicoplanin were the most active agents tested against E. faecalis (MIC90 0.25 mg/L and 0.12 mg/L).

Antibacterial activity of combined cefotaxime and desacetyl-cefotaxime against aerobic and anaerobic gram-negative bacilli.

Synergy between cefotaxime and desacetyl-cefotaxime was evaluated against 12 strains (9 Enterobacteriaceae and 3 Bacteroides fragilis) by the chequerboard technique. A 1:1 combination of cefotaxime and desacetyl-cefotaxime was synergistic against two-thirds of the 12 strains tested. The in vitro activity of the combination was compared with that of four other beta-lactam antibiotics against 96 recent clinical isolates: 78 Enterobacteriaceae, 8 Haemophilus influenzae, 10 B. fragilis. The MICs of the combination for Gram-negative bacilli were similar to those of ceftazidime. Cefotaxime/desacetyl-cefotaxime was more active than cefotetan, cefonicid and piperacillin against Enterobacteriaceae and H. influenzae.

Antibacterial activity after a single-dose of norfloxacin, ofloxacin and pipemidic acid detected in urine of volunteers.

Six healthy volunteers received in a triple-crossover design a single oral dose of norfloxacin, ofloxacin or pipemidic acid. Urine samples were collected during the 24 h following the administration and were tested for inhibitory and bactericidal activity against selected strains of Enterobacteriaceae and Pseudomonas aeruginosa. Norfloxacin and ofloxacin inhibited the urinary growth of sensitive strains during the 24 h of sampling time at dilutions much higher than those generally considered satisfactory. Nalidixic acid was less effective and did not achieve bactericidal activity against Ps. aeruginosa over the interval of 12 to 24 h.

Antistaphylococcal activity of teicoplanin in association with other antibiotics.

The in vitro activity of antibiotic combination of teicoplanin and gentamicin (or netilmicin) and teicoplanin and cephalotin on Staphylococcus aureus was evaluated using the checkerboard method and time-kill curves. With few exceptions neither antagonism nor synergism was seen for the combination of teicoplanin and aminoglycosides using the checkerboard method. Using time-kill curves synergism was often found for the combination of teicoplanin and netilmicin (even at sub-minimal inhibitory concentrations of netilmicin) and for the combination of teicoplanin and cephalotin. No antagonistic interactions occurred.

Chemiluminescence, phagocytosis, chemotaxis and killing activity of human leukocytes exposed to Clindamycin.

We measured the chemiluminescence (CL) of human leukocytes (PMNs) exposed to different concentrations of Clindamycin (1; 5; 1 mcg/ml) using a standardized luminolamplified reagent-instrument methodology (Auto Picolite 6500 Luminometer and ZAP/Picolite Kits, Packard Instruments Co. Drowners Grove, IL. USA). Cells obtained from healthy donors were also tested for chemotaxis with Boyden chambers, for phagocytosis and for killing activity against Staphylococcus aureus by the agar-medium culture plate technique. Clindamycin does not induce significant variations of the CL response in whole blood, or changes in phagocytosis and killing activity. On the contrary, concentrations of drug corresponding to therapeutically obtainable levels significantly increase light emission by isolated cells. A concentration effect was seen on leukotaxis, that was increased, but not significantly, at 1 and 5 mcg/ml and decreased (P less than 0.01) at 10 mcg/ml. CL assay is a simple, sensitive, reproducible technique to assess the PMNs functions during antibiotic therapy.

[Bactericidal activity of beta-lactams and aminoglucosides: comparative evaluations]. / Attività battericida di beta-lattamine e aminoglucosidi: valutazioni comparative.

In this study we have evaluated the bactericidal activity kinetics of some cephalosporins, ureidopenicillins and aminoglycosides against 41 gram negative clinical isolates. Aminoglycosides, particularly gentamicin, showed the better bactericidal activity which appeared already at the second-third hour after the addition of the antibiotic. The bactericidal activity of cefotaxime, ceftazidime and cefotetan was remarkable but it appeared only at the sixth-eight hour. This difference was statistically significant. Carbenicillin and piperacillin showed a low bactericidal activity against Pseudomonas aeruginosa. We noted a wide variability of the antibiotic bactericidal activity against the isolates of the same bacterial species. Therefore we can argue that in serious infections the determination of the antibiotic and serum bactericidal activity is necessary.