Multicenter survey of the changing in vitro antimicrobial susceptibilities of clinical isolates of Bacteroides fragilis group, Prevotella, Fusobacterium, Porphyromonas, and Peptostreptococcus species.

In vitro surveys of antimicrobial resistance among clinically important anaerobes are an important source of information that can be used for clinical decisions in the choice of empiric antimicrobial therapy. This study surveyed the susceptibilities of 556 clinical anaerobic isolates from four large medical centers using a broth microdilution method. Piperacillin-tazobactam was the only antimicrobial agent to which all the isolates were susceptible. Similarly, imipenem, meropenem, and metronidazole were highly active (resistance, <0.5%), whereas the lowest susceptibility rates were noted for penicillin G, ciprofloxacin, and clindamycin. For most antibiotics, blood isolates were less susceptible than isolates from intra-abdominal, obstetric-gynecologic, and other sources. All isolates of the Bacteroides fragilis group were susceptible to piperacillin-tazobactam and metronidazole, while resistance to imipenem and meropenem was low (<2%). For these same isolates, resistance rates (intermediate and resistant MICs) to ampicillin-sulbactam, cefoxitin, trovafloxacin, and clindamycin were 11, 8, 7, and 29%, respectively. Among the individual species of the B. fragilis group, the highest resistance rates were noted among the following organism-drug combinations: for clindamycin, Bacteroides distasonis and Bacteroides ovatus; for cefoxitin, Bacteroides thetaiotaomicron, B. distasonis, and Bacteroides uniformis; for ampicillin-sulbactam, B. distasonis, B. ovatus, and B. uniformis; and for trovafloxacin, Bacteroides vulgatus. For the carbapenens, imipenem resistance was noted among B. fragilis and meropenem resistance was seen among B. fragilis, B. vulgatus, and B. uniformis. With few exceptions all antimicrobial agents were highly active against isolates of Prevotella, Fusobacterium, Porphyromonas, and Peptostreptococcus. These data further establish and confirm that clinically important anaerobes can vary widely in their antimicrobial susceptibilities. Fortunately most antimicrobial agents were active against the test isolates. However, concern is warranted for what appears to be a significant increases in resistance to ampicillin-sulbactam and clindamycin.

A multicenter study of the prevalence and susceptibility patterns of isolates of Streptococcus pneumoniae with reduced susceptibility to penicillin G in Louisiana.

Because of increasing reports of multiple-antibiotic-resistant strains of Streptococcus pneumoniae and associated clinical failures, this study was performed to determine the prevalence of multiresistance among strains from nine Louisiana medical centers. Using a National Committee for Laboratory Standards broth microdilution method, 481 strains were tested. Of these, 70% were penicillin-susceptible (PS), 23% had intermediate minimum inhibitory concentration values to penicillin (I), and 7% were fully resistant to penicillin (PR). The isolation rates (15% to 40% for I strains and 0% to 33% for PR strains) at the various medical centers varied appreciably. The prevalence of penicillin resistance was highest among upper respiratory isolates, while cross-resistance to other antimicrobials varied. The least cross-resistance was noted among PS strains. However, strains with reduced penicillin susceptibility had high levels of cross-resistance. Among I strains, the prevalence of cross-resistance (%) was noted for amoxicillin/clavulanate (6%), cefuroxime (71%), cefaclor (91%), ceftriaxone (13%), cefotaxime (34%), erythromycin (67%), azithromycin (32%), and clarithromycin (32%). For PR strains, the prevalence of cross-resistance was 97% for amoxicillin/clavulanate, cefuroxime, and cefaclor; 67% for ceftriaxone and erythromycin; 89% for cefotaxime; and 69% for azithromycin and clarithromycin. These data emphasize the high prevalence of multiple-antimicrobial-resistance among strains of S pneumoniae with reduced penicillin susceptibility in this geographic area.

Comparison of the in vitro activities of Bay 12-8039, a new quinolone, and other antimicrobials against clinically important anaerobes.

Bay 12-8039, a new 8-methoxy quinolone, was compared with other agents for activity against clinically relevant anaerobes. Bay 12-8039 inhibited 91 and 96% of the 410 test isolates at 2 and 4 micrograms/ml, respectively. Bay 12-8039 had activity comparable to that metronidazole and overall was at least 16-fold more active than ciprofloxacin, ofloxacin, and cefoxitin, 32-fold more active than cefotetan, and at least 128-fold more active than penicillin G.

Fluoride release and shear bond strengths of three light-cured glass ionomer cements.

Little is known about the release of fluoride from light-cured glass ionomer cements when used as orthodontic bonding agents. Fluoride release from three "hybrid" light-cured glass ionomer cements was measured during a 42-day period after initial curing in an in vitro test that simulated their use as orthodontic bonding agents. On day 48, the bonded teeth were exposed for 30 seconds to a stannous fluoride gel and checked for fluoride release during the following week. One cement (BL) released the most fluoride after initial cure and after an exposure to a stannous fluoride gel on day 48. The other two hybrid cements exhibited both significantly less fluoride release than material (BL) and resembled for most of the 55-day duration the composite resin control. After the 55-day duration, shear bond strengths of the composite resin control were significantly higher than the three light-cured glass ionomer cements. The light-cured glass ionomer cements in this study released fluoride after initial curing and after exposure to a topical fluoride gel. This property may help reduce or possibly even prevent enamel decalcifications seen around bracket bases. At present, the shear bond strengths of the light-cured glass ionomer cements tested appear to be too low for routine orthodontic bonding agents.

Comparative in vitro activities of trovafloxacin (CP 99,219) and other antimicrobials against clinically significant anaerobes.

A total of 590 strains of clinically important anaerobes were tested to determine their susceptibility to trovafloxacin. Overall, trovafloxacin had a mode MIC of 0.25 micrograms/ml and a MIC at which 90% of the isolates were inhibited of 1 micrograms/ml and had activity comparable to that of metronidazole. Trovafloxacin was 8-, 8-, 16-, 32-, and 64-fold more active than ampicillin-sulbactam, clindamycin, ciprofloxacin, cefoxitin, and cefotetan, respectively. Of the Bacteroides fragilis group, 97% of the isolates were inhibited by trovafloxacin at 21 micrograms/ml, and trovafloxacin was more active than ciprofloxacin, cefoxitin, cefotetan, ampicillin-sulbactam, and clindamycin against Clostridium, Fusobacterium, Porphyromonas, and Prevotella strains.

Non-invasive determination of recirculation in the patient on dialysis.

Recirculation of blood flow occurs when the fistula flow rate is inadequate to support the desired dialyzer blood flow. The percentage recirculation is normally calculated using the blood urea nitrogen of blood samples from the two dialyzer blood lines and a peripheral blood sample. However, this method is time consuming, costly, and may not always give accurate measurements. A technique was developed to measure recirculation using the injection of saline into the venous dialysis line. For this technique, an optical detector is placed across the arterial dialysis tubing, and the light intensity, which is proportional to the hematocrit, is continually measured using a computerized data collection system. After a baseline data collection period, 10 ml of saline is injected into the venous dialysis line using the sampling port. The saline that appears in the arterial dialysis line as a result of recirculation will cause a dilution of the blood and an increase in light intensity. In vitro testing showed an excellent correlation between the area under the dilution curve and percentage recirculation. This technique will provide a quick, inexpensive, and reliable measurement of recirculation.