Long-term sub-antimicrobial doxycycline (Periostat) as adjunctive management in adult periodontitis: effects on subgingival bacterial population dynamics

Previous trials had indicated that various schedules of sub-antimicrobial doxycycline significantly reduced gingival crevicular fluid (GCF) collagenase activity in adult patients with periodontitis with no evidence of emergent tetracycline-resistant (Tcr) marker oral flora. The purpose of this nine-month study was to expand these observations, emphasizing newer microbial diagnostic methods. Subgingival paper point samples were obtained at baseline (BL), 3, 6, and 9 months. Four subject treatment groups in a double-blind design were evaluated by mechanical scaling and root planing (SRP) and/or 20 mg doxycycline BID (Periostat). Thirty-eight patients entered the study at baseline (BL). Dark-field microscopy on 260 samples showed that morphotype distribution was independent of treatment schedule. Culture analysis of the 3 most prevalent isolates recovered showed that Streptococcus and Prevotella species accounted for approximately 85% of the 724 cultures. There did not appear to be any overgrowth or replacement by opportunistic oral flora. Of 658 susceptibility patterns evaluated by Etest, the MIC50/90 and mode MIC showed stable patterns, independent of treatment group. Our findings were different from those of previously published reports, but may be partly explained by the lack of universally standardized methods in oral microbiology and interpretive criteria for susceptibility testing.     

Is Treatment of Mine Dewatering Water Necessary Prior to Rapid Infiltration Basin Recharge? A Case Study

In Nevada, USA, the return of mine dewatering water (MDW) to the subsurface through rapid infiltration basins (RIBs) requires treatment if the quality exceeds the state’s Division of Environmental Protection (NDEP) Profile I reference values. However, a 2019 change to the Nevada Administrative Code allows discharge without treatment if the natural background groundwater solute concentrations are not exceeded. We developed a novel approach to demonstrate that groundwater will not be adversely affected by the untreated discharge of MDW. At the Cortez Gold Mine, dewatering will discharge water to the Grass Valley RIBs with 0.045 mg/L of As, exceeding the NV Profile I reference value (0.010 mg/L) and natural background (0.015 mg/L). A MODFLOW-SURFACT groundwater model incorporated empirical hydraulic conductivities to evaluate the extent to which changes in mound water depth and quality would occur. Modeling inputs were determined using column tests to assess SO₄ leaching from the alluvium and batch tests to quantify As partition coefficients (Kd_As?=?8.9 L/kg) to the alluvium. The results indicated that Profile I will be met at all compliance wells due to dispersion and attenuation. The Kd_As was also used to calculate the attenuation capacity of the alluvial mound water by adsorption (100-years), well beyond the 13-year operational span of the RIBs. Based on this analysis, and in conjunction with a similar analysis in the adjacent Crescent Valley, where 25 years infiltration of 0.045 mg/L As had not affected groundwater quality, the NDEP concurred that a dewatering water treatment plant was unnecessary. Overall, our analysis obviated construction of four treatment plants in the area and permitted direct discharge of mine dewatering water to the subsurface.

     

Minimizing respiratory complications of nasoenteric tube feedings: state of the science

This article summarizes research findings regarding ways to minimize the two most dreaded complications of tube feedings: (1) introduction of feedings through tubes positioned in the respiratory tract, and (2) pulmonary aspiration. Bedside methods that lack reliability in ruling out inadvertent respiratory placement of feeding tubes include the auscultatory method, the bubbling under water method, and observing for respiratory symptoms. Testing the pH of aspirates from feeding tubes can be of use in ruling out respiratory placement of newly inserted tubes when acidic values are properly obtained; further, this method can also be helpful in determining when a tube has migrated from the stomach to the intestine. Based on experience, the most frequently cited values for excessive gastric residuals are 100 to 150 ml. In a recent small study, researchers concluded that the residual volume that should raise concern in patients with nasogastric tubes is 200 ml and in patients with gastrostomy tubes the amount is 100 ml. Several recent studies indicate that although elevating the head of the bed 30 to 45 degrees does not prevent aspiration, it does reduce its frequency and severity. Because many studies described in this review have not been replicated, readiness of their findings for clinical application is variable. Many questions regarding methods to prevent respiratory complications in tube-fed patients remain unanswered, largely because it is difficult to design clinical studies with sufficient control of significant variables.