Celso Luiz Cardoso

Effectiveness of hand-cleansing agents for removing Acinetobacter baumannii strain from contaminated hands

BACKGROUND The effectiveness of hand-cleansing agents (plain liquid soap, 70% ethyl alcohol, 10% povidone-iodine, and 4% chlorhexidine gluconate) for removing a hospital strain of Acinetobacter baumannii from artificially contaminated hands of 5 volunteers was studied. METHODS The experiments were performed by using a Latin square statistical design, with two 5 x 4 randomized blocks, and the results were estimated by ANOVA. In the first and second blocks, the fingertips of the volunteers were contaminated with approximately 10(3) colony-forming units (light contamination hand) and 10(6) colony-forming units (heavy contamination hand), respectively. RESULTS In the first block, all products tested were effective, almost completely removing the microbial population of A baumannii artificially applied to the hands. In the second block, the use of hand-cleansing agents resulted in 91.36% (4% chlorhexidine), 92.33% (liquid soap), 98.49% (10% povidone-iodine), and 98.93% (70% ethyl alcohol) reduction in counts of A baumannii cells applied to the fingertips. The ethyl alcohol and povidone-iodine had significantly higher removal rates than plain soap and chlorhexidine (P <.05). CONCLUSIONS These results suggest that 70% ethyl alcohol and 10% povidone-iodine may be the most effective hand-cleansing agents for removing A baumannii strain from heavily contaminated hands (10(6) colony-forming units/fingertip).

Effectiveness of hand-cleansing agents for removing methicillin-resistant Staphylococcus aureus from contaminated hands

OBJECTIVE The effectiveness of hand-cleansing agents in removing a hospital strain of methicillin-resistant Staphylococcus aureus from artificially contaminated hands of five volunteers was studied. DESIGN The products used were plain liquid soap, ethyl alcohol 70% (by weight), 10% povidone-iodine liquid soap (PVP-I), and chlorhexidine gluconate (4%) detergent. The experiments were performed using a Latin square statistical design, with two 5x4 randomized blocks. The removal rates of S aureus cells from contaminated fingertips were estimated by analysis of variance, the response variable being the log10 reduction factor (RF), ie, log10 of the initial counts minus log10 of the final counts. In the first and second blocks, the fingertips of the volunteers were contaminated in mean with 3.76 log10 colony-forming units ([CFU] light-contamination hand) and 6.82 log10 CFU (heavy-contamination hand), respectively. RESULTS In the first block, there were significant differences between treatments (P<.05). The 10% PVP-I (RF, 3.76) and 70% ethyl alcohol (RF, 3.51) had significantly higher removal rates than plain liquid soap (RF, 1.96) and 4% chlorhexidine (RF, 1.91). In the second block, 10% PVP-I (RF, 4.39) and 70% ethyl alcohol (RF, 3.27) also were significantly more effective than plain liquid soap (RF, 1.77) and 4% chlorhexidine (RF, 1.37; P<.05). Plain liquid soap was significantly more effective than chlorhexidine (4%) detergent. CONCLUSIONS The results suggest that 10% PVP-I and 70% ethyl alcohol may be the most effective hand-cleansing agents for removing methicillin-resistant S aureus strain from either lightly or heavily contaminated hands.

Nasal carriage of methicillin-resistant Staphylococcus aureus in university students.

In a study of university students, the percentage nasal carriage of Staphylococcus aureus was 40.8% (102/250). Of the isolates, MIC(50) of methicillin was 0.5 µg/mL and MIC(90) was 1 µg/mL. Six (5.8%) isolates were methicillin-resistant and carried the mecA gene. These results suggest that community-associated methicillin-resistant S. aureus may be spreading in Brazil.

Rapid decontamination of gutta-percha cones with sodium hypochlorite.

Gutta-percha cones are now widely used to fill root canals. Because they cannot be sterilized by conventional autoclaving or in a hot-air oven, gutta-percha cones require rapid chairside decontamination before use to maintain the aseptic chain, an essential factor in successful endodontic therapy. The purpose of this study was to compare the effectiveness of different concentrations of sodium hypochlorite (0.25% to 4%) in sterilizing gutta-percha cones artificially contaminated with Staphylococcus aureus and Escherichia coli strains, and Bacillus subtilis spores. After 1 min of treatment, the solutions tested showed bactericidal and sporicidal effects at concentrations of 0.25% and 1%, respectively. At a concentration of 0.25%, the solutions tested were effective in destroying spores after 5 min of exposure. Based on this study, treatment of the cones for 1 min with 1% sodium hypochlorite (Miltons solution) or for 5 min with Dakins liquid (0.5% sodium hypochlorite) is recommended.

Effectiveness of different chemical agents in rapid decontamination of gutta-percha cones

The effectiveness of seven disinfectant compounds used in dentistry for a rapid decontamination of 32 gutta-percha cones adhered with Staphylococcus aureus, Enterococcus faecalis, Escherichia coli strains or Bacillus subtilis spores was compared. Cones were treated with 2% glutaraldehyde, 1% sodium hypochlorite, 70% ethyl alcohol, 1% and 0.3% iodine alcohol, 2% chlorhexidine, 6% hydrogen peroxide, and 10% polyvinylpyrrolidone-iodine, for 1, 5, 10, and 15 minutes. After treatment, each cone was transferred to thioglycollate broth and incubated at 37oC for 7 days. The products were bactericidal after 1 to 5 minutes and, with exception of ethyl alcohol and iodine-alcohol, sporicidal after 1 to 15 minutes of exposure. Results suggest that chlorhexidine, sodium hypochlorite, polyvinylpyrrolidone-iodine, hydrogen peroxide, and glutaraldehyde were the most effective products in the decontamination of gutta-percha cones.

Preliminary evaluation of adherence on abiotic and cellular surfaces of Acinetobacter baumannii strains isolated from catheter tips

The cell surface hydrophobicity and adhesion to abiotic and cellular surfaces was tested in five clinical strains of Acinetobacter baumannii isolated from catheter tips. Biochemical and molecular characteristics of these strains were also studied. Hydrophobicity was characterized by a test for affinity to xylene. Adhesion to abiotic surfaces (polystyrene, formica, latex and glass) was evaluated in Petri plates using the stamp technique. Buccal epithelial cells were used for tests of adhesion to cellular surfaces. Adhesion to the catheter was evaluated by repeatedly rinsing the catheters and rolling them over nutrient agar. Molecular typing of the strains was done by the ERIC-PCR technique. The degree of hydrophobicity of the strains varied from hydrophobic to hydrophilic. All the strains adhered to the cell surfaces and to the catheters, and three of them strongly adhered to latex, polystyrene and formica. Catheter adhesion was reduced by meropenem. We found a direct relationship between the degree of bacterial hydrophobicity and adhesion to the abiotic surfaces, but not with adhesion to cellular surfaces, which suggests that different mechanisms are involved in adherence.

In vitro evaluation of the antimicrobial activity of meropenem in combination with polymyxin B and gatifloxacin against Pseudomonas aeruginosa and Acinetobacter baumannii.

Abstract The antimicrobial activity of meropenem combined with either polymyxin B or gatifloxacin was evaluated by the checkerboard method against Pseudomonas aeruginosa (10 strains) and Acinetobacter baumannii (10 strains). In addition, the triple combination of polymyxin B, gatifloxacin, and meropenem was also studied as well as the polymyxin B and gatifloxacin combination. A partial synergism interaction between meropenem and polymyxin B was observed for 80% of the A. baumannii strains. In contrast, this combination showed an indifferent effect for 80% of the P. aeruginosa strains tested. The combination of meropenem and gatifloxacin showed synergism only for two strains of A. baumannii, and partial synergism and additive effect for seven strains and indifference for four strains of both species. For the strains of P. aeruginosa, the double combination of polymyxin B and gatifloxacin and the triple combination of meropenem, polymyxin B and gatifloxacin were indifferent for the majority of the strains tested, that is, 90 and 80% respectively.

Improved Laboratory Safety by Decontamination of Unstained Sputum Smears for Acid-Fast Microscopy

ABSTRACT Tubercle bacilli may survive in unstained heat-fixed sputum smears and may be an infection risk to laboratory staff. We compared the effectiveness of 1% and 5% sodium hypochlorite, 5% phenol, 2% glutaraldehyde, and 3.7% formalin in killing Mycobacterium tuberculosis present in smears prepared from 51 sputum samples. The smears were decontaminated by the tube and slide techniques. Phenol at 5%, glutaraldehyde at 2%, and buffered formalin at 3.7% for 1 min (tube technique) or for 10 min (slide technique) were effective in decontaminating sputum smears and preserved cell morphology and quantitative acid-fast microscopy results.

In vitro activity of polymyxins in combination with β-lactams against clinical strains of Pseudomonas aeruginosa

The emergence of multidrug-resistant (MDR) strains has made it difficult to treat infections caused by Pseudomonas aeruginosa. In order to develop new alternative therapies for the treatment of MDR P. aeruginosa infections, the antimicrobial activities of different antibiotic combinations have been studied in vitro and in vivo. In this study, the in vitro antimicrobial activities of six different combinations of polymyxins and β-lactams against 34 clinical isolates of P. aeruginosa were evaluated. For the combinations tested by the checkerboard method, an indifferent effect was observed for all strains. However, 27 strains (19 MDR) showed reductions in their minimal inhibitory concentration (MIC) for at least one of the antibiotics in the combinations evaluated. Combination with polymyxins resulted in reductions of the β-lactam MICs, with a change in the resistance category to susceptible in eight MDR strains. These results from the in vitro evaluation suggest that combinations of polymyxins and β-lactams may significantly reduce the MICs of the antibiotics tested. These combinations require further evaluation for use in medical practice.

High prevalence of children colonized with penicillin-resistant Streptococcus pneumoniae in public day-care centers

OBJECTIVES To investigate the prevalence of Streptococcus pneumoniae (pneumococci) in the nasopharynx of healthy children enrolled in public day-care centers of the municipality of Umuarama, state of Paraná, Brazil. The susceptibility of the pneumococcal strains to antimicrobial agents was also studied. METHODS Nasopharyngeal specimens from 212 children were collected from April to October 2008. After the specimens were seeded in blood agar and incubated at 37 degrees C for 24-48 hours, the colonies suspected of belonging to S. pneumoniae were identified using alpha-hemolysis, optochin sensitivity, and bile solubility test. Penicillin susceptibility was investigated using the disk diffusion and dilution tests. Susceptibility to the other antimicrobial agents indicated for the treatment of pneumococcal infections was investigated using the disk diffusion test. RESULTS The prevalence of nasopharyngeal pneumococci was 43.4% (92/212), with higher rates in children between 2 and 5 years old (p = 0.0005). There was no significant difference between sexes. Intermediate and full resistance to penicillin were found in 34.8 (32/92) and 22.8% (21/92) isolates, respectively. Sixty-seven strains (72.8%) were resistant to sulfamethoxazole-trimethoprim, eight (8.7%) were resistant to erythromycin, and six (6.5%) to tetracycline. One strain was resistant to clindamycin (1.1%) and another was resistant to chloramphenicol (1.1%). All strains were sensitive to levofloxacin, ofloxacin, rifampicin, telithromycin, linezolid, and vancomycin. Nine strains were considered multiresistant because they were resistant to three or more classes of antimicrobial agents. CONCLUSIONS The present study detected a high prevalence of healthy children colonized with penicillin-resistant S. pneumoniae strains who may be important reservoirs of this pathogen in the community.