An in vitro comparison of antimicrobial toothbrushes.

The purpose of this study was to determine the efficacy of toothbrushes that advertise self-disinfecting, antimicrobial properties due to the inclusion of silver nanoparticles or chlorhexidine in the bristles. Three different types of toothbrushes-silver nanoparticle, chlorhexidine-coated, and a control-were submerged in suspensions of Streptococcus mutans and Candida albicans. At designated times postinoculation, organisms were removed from the toothbrush heads, then serially diluted, plated, and incubated. The colony-forming units (CFUs) were counted and a mean percent reduction was determined for each organism group. With the S. mutans groups, the chlorhexidine-coated toothbrushes had significantly greater percent reduction in CFUs at all 3 time points compared to the control or silver nanoparticle toothbrushes. With the C. albicans groups, neither the chlorhexidine-coated nor the silver nanoparticle toothbrushes had a significant reduction in CFUs compared to the control. Neither of the antimicrobial toothbrushes delivered the advertised claim of a 99.9% reduction in CFUs with either microorganism. However, the inclusion of chlorhexidine in toothbrush bristles appeared to be the most promising of the methods tested for toothbrush self-disinfection.

Performance of five FDA-approved rapid antigen tests in the detection of 2009 H1N1 influenza A virus.

Rapid antigen tests are commonly used by clinicians for rapid, simple, point-of-care testing. Five rapid antigen tests were shown to have low sensitivity (40.3-58.8%) when compared to real-time RT-PCR using nasal wash specimens from patients with influenza-like-illness (N = 167) that were collected previously and confirmed as 2009 pandemic influenza A (H1N1)-positive by PCR. Rapid antigen test sensitivity correlated with virus levels in nasal secretions when comparisons were made to cycle threshold (C(T)) values obtained from real-time RT-PCR. When C(T) values are <25 (equating to viral concentrations of >10(4) TCID(50)/ml) sensitivity for all five rapid antigen kits was high (range: 83-94% positive); however, when C(T) values are >30 (10(2) TCID(50)/ml), sensitivities of only 16-18% were observed for four of five rapid antigen kits. The Directigen EZ Flu A + B test detected more positive samples (35%) at lower viral concentrations with C(T) values >30 when compared with other commercial kits (P = 0.05). Rapid antigen test results must be interpreted with caution, and negative specimens may need confirmation by sensitive molecular assays.

Maintenance of antimicrobial susceptibility of Acinetobacter baumannii in modeled microgravity.

OBJECTIVE: The purpose of this study was to evaluate the effect of a modeled microgravity environment on the antimicrobial resistance of Acinetobacter baumannii. DESIGN: Clinical isolates of A. baumannii (n=10) in Mueller Hinton broth were grown in high aspect ratio vessels using a rotary cell culture system oriented to achieve either normal earth gravity (1 x G) or low sheer modeled microgravity (LSMMG) conditions. After culture MICs were determined by Etest. Antimicrobials included in the study were amikacin, ampicillin/sulbactam, azithromycin, ceftazidime, gatifloxacin, gentamicin, imipenem, meropenem, minocycline, ticarcillin/clavulanic acid, tigecycline, and trimethoprim/sulfamethoxazole. Results were compared for MIC value and category interpretation (S, I, R). RESULTS: Overall category agreement was 100% (360/360). 100% of MIC values compared were within one twofold dilution of each other. CONCLUSION: Under these test conditions LSMMG had no apparent effect on the resistance pattern of A. baumannii.

Acinetobacter baumannii and MRSA contamination on reusable phlebotomy tourniquets.

OBJECTIVE: A study was undertaken to determine the incidence of Acinetobacter baumannii and methicillin resistant Staphylococcus aureus (MRSA) contamination on reusable phlebotomy tourniquets at Wilford Hall Medical Center, Lackland AFB, TX. DESIGN: Reusable tourniquets (n=200) were collected after being used for one day in the outpatient blood collection center (n=100) or during morning blood collection rounds on inpatient wards (n=100). Tourniquets were cultured and growth was screened for A. baumannii and S. aureus. A. baumannii isolates were identified using colonial morphology, oxidase, and GNI+ card on Vitek Legacy. S. aureus isolates were identified and screened for MRSA using colonial morphology, catalase, Staphaurex, and Oxacillin screening agar. RESULTS: Each outpatient tourniquet was used on an average of 33 patients and each inpatient tourniquet was used on an average of 11 patients. The overall contamination rate was 9% (18/200). A. baumannii was isolated from 11% (11/100) of the outpatient tourniquets and 3% (3/100) of the inpatient tourniquets. Methicillin-susceptible S. aureus was isolated from 2% (2/100) of the outpatient tourniquets and 3% (3/100) of the inpatient tourniquets. No MRSA was isolated. One ou'tpatient tourniquet had both A. baumannii and methicillin-susceptible S. aureus. CONCLUSIONS: Reusable tourniquets could serve as a potential reservoir for bacterial pathogens.

Comparison of in-office dental unit waterline test kits.

The authors conducted a study to determine the validity of two commercially available in-office dental unit waterline test kits compared to the gold standard, R2A agar. Samples were collected from the air/water syringes of dental units and cultured on HPC Samplers, Petrifilm AC Plates, and R2A agar plates. HPC Samplers and R2A agar plates were incubated for 7 days and counted manually using magnification. Petrifilm AC Plates were counted after incubation time of 5 and 7 days using an electronic-plate reader. Validity measurements were calculated using a cutoff value < or = 500 colony-forming units per milliliter. The accuracy for the HPC Sampler compared to R2A agar was 71%. The accuracy for the Petrifilm AC Plates at 5 and 7 days was 79% and 87% compared to R2A agar. The Petrifilm AC Plate (7-day incubation) demonstrated higher sensitivity, specificity, predictive values, and accuracy than the HPC Sampler kit.

An evaluation of the advandx Staphylococcus aureus/CNS PNA FISH assay.

PURPOSE: A study was conducted to compare the S. aureus/CNS PNA FISH Culture Identification Kit (AdvanDx, Woburn MA) to standard microbiology identification methods for presumptive identification of S. aureus and coagulase-negative staphylococcus (CNS) in positive blood cultures. MATERIALS AND METHODS: Blood cultures (n=301) that signaled positive on the BacT/Alert 3D (bioMerieux, Durham NC) automated blood culture system and had gram-positive cocci in clusters on Gram stain were processed using standard microbiology methods and were analyzed with the S. aureus/CNS PNA FISH assay. The S. aureus/CNS PNA FISH assay was performed in accordance with the manufacturer's instructions. RESULTS: Overall agreement was 96.7%. Sensitivity for S. aureus was 96.5% (83/86). Specificity for S. aureus was 100% (215/215). Sensitivity for CNS was 96.6% (201/208). Specificity for CNS was 96.8% (90/93). Three cultures reported as S. aureus were identified as CNS by S. aureus/CNS PNA FISH. Three cultures that reported only S. aureus were positive for both S. aureus and CNS by S. aureus/CNS PNA FISH. One S. viridans was identified as CNS by S. aureus/CNS PNA FISH. Seven cultures that reported CNS were negative by S. aureus/CNS PNA FISH. CONCLUSION: When used in conjunction with Gram stain and culture the S. aureus/CNS PNA FISH assay may be beneficial in terms of reducing time to correct therapy, thereby decreasing mortality and costs associated with S. aureus bacteremia.

Predicting irreparable renal ischemic injury using a real-time marker in the porcine model.

PURPOSE: We determined the maximal renal tolerance of warm ischemia using renal cortical interstitial metabolic changes to identify a potential real-time marker of irreparable renal function. MATERIALS AND METHODS: Using a single kidney model 3 groups of 5 pigs each underwent 120, 150 and 180 minutes of warm ischemia, respectively. Microdialysis samples were collected before, during and after ischemia. Renal function assessments consisting of serum creatinine and GFR measurements were performed before ischemia and on post-ischemia days 1, 5, 9, 14 and 28. Kidneys exposed and not exposed to ischemia were collected for histological study. RESULTS: Interstitial glucose and pyruvate concentrations decreased, while lactate concentrations increased to stable levels during ischemia. Glutamate spiked at 30 minutes of ischemia and subsequently tapered, while glycerol increased throughout warm ischemia time. At post-ischemia day 28 renal function returned to pre-ischemia baseline levels in the group with 120 minutes of ischemia but did not recover to baseline in the 150 and 180-minute ischemic groups. Functional data correlated with histological findings. The 120-minute maximal renal tolerance of warm ischemia correlated with a mean +/- SD glycerol concentration of 167 +/- 24 micromol/l. CONCLUSIONS: Interstitial glycerol is a real-time, renal unit specific, minimally invasive marker of renal function deterioration. Exposure of porcine kidneys to ischemic insults resulting in renal cortical interstitial glycerol concentrations higher than 167 micromol/l is associated with irreparable functional damage in this model.

Evaluation of disinfectants on military NATO and DECON litters.

OBJECTIVE: This study evaluated the effectiveness of five disinfectants: A33, 10% bleach, 1% bleach, SPOROX, and 3% H2O2, on military NATO and DECON litters. DESIGN: Suspensions of Acinetobacter baumannii, Staphylococcus aureus, and spore-enhanced Bacillus subtilis, with five percent albumin, were inoculated onto litters and dried overnight. The litters were saturated with disinfectant solutions and sampled after 10 minutes. The Log10 reduction in the number of bacteria recovered was calculated. SETTING: 59th Medical Wing, 59th Clinical Research Division, Lackland AFB TX. MAIN OUTCOME MEASURES: A reduction of > or =3 Log10 in the number of bacteria recovered from the test squares compared to the control squares was considered effective disinfection. RESULTS: On the NATO litter 10% bleach and SPOROX were effective against vegetative cells. On the DECON litter A33, 10% bleach, and SPOROX were effective against vegetative cells. After the 10 minute exposure none of the disinfectants evaluated were effective against spore-enhanced B. subtilis. CONCLUSION: When contaminated with vegetative cells military NATO and DECON litters can be effectively disinfected with a 10 minute exposure to some disinfectants. Further research is needed to find an effective disinfectant for spore contamination.

Fluoride release from newly marketed fluoride varnishes.

OBJECTIVE: New fluoride varnishes have been marketed that reportedly release more fluoride (Enamel Pro) or release fluoride more slowly (Vanish XT). The purpose of this study was to compare the amount and rate of fluoride release of new fluoride varnishes with other traditional fluoride varnishes. METHOD AND MATERIALS: Extracted molars were cut into block sections. The enamel surfaces of the sections were painted with Enamel Pro, Duraphat, Vanish, or Vanish XT fluoride varnishes. One group was not treated and served as a negative control. The tooth sections were immersed in artificial saliva. The concentration of fluoride in parts per million was measured after the first 30 minutes, daily for the first week, and weekly until the level was below the limit of detection. Fluoride release was plotted over time. Cumulative fluoride release and rate of release (slope) were analyzed using one-way ANOVA/Tukey (α = .05). RESULTS: Enamel Pro had the greatest cumulative fluoride release. There was no significant difference between Duraphat and Vanish. Vanish XT had the lowest cumulative fluoride release. The rate of fluoride release from 1 week to limit of detection was Enamel Pro > Vanish > Duraphat > Vanish XT. CONCLUSION: The two newly marketed fluoride varnishes (Enamel Pro and Vanish XT) had significantly different fluoride release from the two conventional fluoride varnishes (Duraphat and Vanish).