Serum and crevicular fluid concentrations after a single oral dose of metronidazole.

Previous studies have shown that metronidazole is an effective chemotherapeutic agent in the treatment of certain types of periodontal disease. The purpose of this study was to assess, over 18 hours, the concentration of the drug in serum and gingival crevicular fluid after a single oral dose. Six female volunteers with gingivitis created by cessation of brushing for 2 weeks, took 250 mg of metronidazole orally. Micropipettes were used to collect 20 microliters of serum and 4 to 5 microliters of gingival fluid hourly for 8 hours, and at the 12th and 18th hours. Samples were assayed with a high pressure liquid chromatograph. Mean drug levels in serum closely matched those reported by Stephen et al. (Br Dent J 7: 313, 1966) with polography. Mean serum drug levels peaked at 6.09 micrograms/ml at the 2nd hour, and mean gingival crevicular fluid drug levels peaked at 3.62 micrograms/ml at the 2nd and 7th hours. The drug was detectable in both fluids for up to 18 hours. Mean serum concentrations remained greater than mean gingival fluid concentrations at all time intervals, though the differences were not significant (P less than 0.05) as determined by a Hoteling's T2 test. Using reported minimal inhibitory concentration values of metronidazole for various periodontopathogens, it was concluded that a single oral dose of metronidazole will deliver potentially inhibitory levels of the drug to the periodontium in serum and in gingival crevicular fluid.

Filtration of dialysate using an on-line dialysate filter.

UNLABELLED: Increased concerns about pyrogenic contamination of dialysate have led to the development of an on-line dialysate filtration system. Bacteriological testing of the system was performed (n = 6) by introducing bicarbonate concentrate contaminated with E. coli 026:B 6 (3 x 10(9) cfu/ml) into a dialysis machine equipped with a two-stage polysulfone filtration system. The bacterial concentration of the dialysate entering the filtration system was maintained above 10(6) cfu/ml and endotoxin levels ranged from 30-300 ng/ml during the 3-hour test period. Bacterial and endotoxin levels on the input side of the first-stage filter reached minimum concentrations of 5.4 x 10(9) cfu/ml and 30,000 ng/ml respectively. All output samples of filtered dialysate showed no bacterial growth and endotoxin levels were below the sensitivity (0.003 ng/ml) of the LAL assay. A dialysis machine (QD = 500), equipped with a single stage filtration system, was used for 18 months of clinical testing. In order to evaluate the system's reliability with regard to membrane failures and reduced dialysate flow, filter membrane integrity was verified weekly using a pressure holding test and dialysate flow was measured under routine clinical conditions. No membrane failures occurred, and dialysate flow was maintained at 511 +/- 17 ml/min (n = 70) during the test period. IN CONCLUSION: dialysate filtration is an effective and practical method for prevention of pyrogenic reactions due to high levels of bacteria and endotoxins.

Comparison of five commercial western blot kits for detection of human immunodeficiency virus 1.

Twenty-two human immunodeficiency virus 1 (HIV-1) enzyme immunoassay (EIA) reactive and two non-reactive patient specimens were analyzed using five commercially available HIV-1 Western blot kits. The percentage of HIV-1 bands detected by each kit was recorded. The differences between pairs of kits were not found to be statistically significant at the 0.05 level. All EIA reactive specimens were reconfirmed as reactive by each Western blot kit tested.

In vitro susceptibilities of 393 recent clinical isolates to WIN 49375, cefotaxime, tobramycin, and piperacillin.

The in vitro susceptibilities of 393 recent clinical isolates to WIN 49375, a new quinolone derivative, were determined and concurrently tested with cefotaxime, tobramycin, and piperacillin. In general, members of the family Enterobacteriaceae were not as susceptible to tobramycin and piperacillin as they were to WIN 49375. Methicillin-resistant and -susceptible Staphylococcus aureus were equally susceptible to WIN 49375.

Effect of quinolones and other antimicrobial agents on cell-associated Legionella pneumophila.

We evaluated the in vitro susceptibility of Legionella pneumophila ATCC 33152 (serogroup I) to 13 antibiotics alone and in combination with rifampin (0.1 mg/liter) by three methods. Extracellular susceptibility was determined by MIC determinations and time kill curves in buffered yeast extract broth, while intracellular susceptibility was determined by peripheral human monocytes in RPMI 1640 culture medium. Antibiotic concentrations equal to or greater than the broth dilution MIC inhibited or killed L. pneumophila by the time kill method, except this was not the case for trimethoprim-sulfamethoxazole. Antibiotic concentrations below the broth dilution MIC did not inhibit Legionella growth. The only antibiotic-rifampin combinations which produced improved killing of L. pneumophila by the time kill method were those in which the logarithmic growth of L. pneumophila occurred during the experiment (rosoxacin, amifloxacin, cinoxacin, trimethoprim-sulfamethoxazole, clindamycin, and doxycycline). Neither direct MICs nor time kill curve assays accurately predicted intracellular L. pneumophila susceptibility. Rifampin, erythromycin, ciprofloxacin, rosoxacin, enoxacin, amifloxacin, gentamicin, clindamycin, and doxycycline all inhibited intracellular L. pneumophila growth at readily achievable concentrations in serum. Cefoxitin and thienamycin showed no inhibition of growth, although they were present extracellularly at concentrations that were 20 to 1,000 times their broth dilution MICs. Clindamycin was the only antibiotic that was able to inhibit intracellular L. pneumophila growth at an extracellular concentration below its MIC. The gentamicin (5 mg/liter)-rifampin combination was the only antibiotic-rifampin combination which demonstrated decreased cell-associated Legionella survival in this model of in vitro susceptibility.

Comparison of ciprofloxacin and rifampicin in experimental Legionella pneumophila pneumonia.

We evaluated intraperitoneal ciprofloxacin and rifampicin alone and as combination therapy in experimentally induced Legionella pneumophila pneumonia in guinea pigs. Intraperitoneal treatment began 48 h after intratracheal inoculation of 3 X 10(6) L. pneumophila and consisted of sterile saline (0.3 ml bid), ciprofloxacin (30 mg/kg bid), rifampicin (10 mg/kg/bid), or ciprofloxacin plus rifampicin (same doses). Animals were treated for five days and survivors killed after 11 days. Quantitative lung cultures were done post mortem. Respective mean and median days of animal survival were increased by treatment with ciprofloxacin plus rifampicin (8.4 and 9.5 days), ciprofloxacin (8.2 and 7.5 days), or rifampicin (8.3 and 7.5 days), compared with controls (5.5 and 5.0 days). Compared with control animals (log rank test) survival was improved by treatment with ciprofloxacin plus rifampicin (P less than or equal to 0.047) ciprofloxacin (P less than or equal to 0.047) or rifampicin (P less than or equal to 0.047). Quantitative lung cultures (cfu/g) were also decreased by treatment with ciprofloxacin plus rifampicin (2.0 X 10(4)), ciprofloxacin (5.4 X 10(4)), or rifampicin (1.7 X 10(4)) compared with controls (3.2 X 10(8)). No differences in survival, quantitative lung cultures, or animal weights were noted between treatment groups. This study demonstrates that ciprofloxacin is as effective as rifampicin in the treatment of experimentally induced L. pneumophila pneumonia and that the combination of ciprofloxacin plus rifampicin has no advantages over single agent therapy in this model.

The effect of heat upon the interaction between aminoglycosides and semi-synthetic penicillins in human serum: a consideration for HIV infectious serum.

We conducted 2 experiments to study the effect of heat on the interaction between aminoglycosides and semi-synthetic penicillins in human serum. In one experiment, human serum spiked with either gentamicin or tobramycin at a concentration of 4.7 mg/l plus carbenicillin, ticarcillin, piperacillin, mezlocillin, or azlocillin at concentrations of either 50 mg/l or 150 mg/l was subjected to a 30-min, 56 degrees C waterbath incubation. In the second experiment, randomly selected sera from patients receiving either gentamicin or tobramycin were also heat-treated. Two methods, the Abbott TDx and the Syva Emit, were used for each aminoglycoside assay. The difference between pre- and post-heat treatment aminoglycoside concentration was less than 10% in approximately 92% of the patient sera and in 93% of the spiked sera containing an aminoglycoside plus a semi-synthetic penicillin at 50 mg/l. For sera spiked with an aminoglycoside plus a semi-synthetic penicillin at 150 mg/l, post-heat treatment concentrations were 5-19% lower than pre-heat treatment concentrations. In most instances, heat treatment of sera does not alter aminoglycoside concentrations to any clinically significant degree.

Comparison of fluorescence polarization immunoassay and bioassay of vancomycin.

Human serum samples were analyzed for vancomycin concentrations by two different methods: the fluorescence polarization immunoassay and the disk plate bioassay. Each assay method offered acceptable precision. The correlation between both assay methods was excellent (correlation coefficient = 0.985). Excluding technical time, the bioassay was the least expensive method to perform but was more labor intensive than the fluorescence polarization immunoassay.

Comparison of enzyme-multiplied immunoassay technique with fluorescence polarization immunoassay for determination of gentamicin and tobramycin levels in serum.

We assayed serum gentamicin and tobramycin specimens by the enzyme multiplied immunoassay technique (Syva EMIT) and the fluorescence polarization immunoassay (Abbott TDx). When interassay and intraassay control samples were evaluated, both methods gave an overall coefficient of variation of less than +/- 10%. Using patient serum samples, we obtained excellent correlation with both methods in the assay of gentamicin (correlation coefficient, 0.985) and tobramycin (correlation coefficient, 0.982).

In-vitro susceptibility of staphylococci to fleroxacin in comparison with six other quinolones.

Susceptibilities of methicillin-resistant Staphylococcus aureus (MRSA, n = 32), methicillin-sensitive S. aureus (MSSA, n = 32), and S. epidermidis (SE, n = 24) were determined to fleroxacin, amifloxacin, ciprofloxacin, difloxacin, enoxacin, norfloxacin, and ofloxacin. All organisms were isolated from the blood of patients with infective endocarditis. MRSA and MSSA MIC90s were less than 1.0 mg/l of fleroxacin, ciprofloxacin, difloxacin, and ofloxacin while amifloxacin and norfloxacin produced MIC90s of less than 2.0 mg/l and enoxacin MIC90s of less than 4.0 mg/l. For S. epidermidis MIC90s were less than 1.0 mg/l of all quinolones except amifloxacin whose MIC90 was less than 2.0 mg/l. Two strains from each staphylococcal group were used in time-kill trials performed with all seven quinolones. Within 8 h, all quinolones colony counts were decreased by one log. At 24 h, most quinolones decreased MRSA, MSSA, and SE colony counts by two to four logs; however, exceptions were found with (1) difloxacin, enoxacin, and norfloxacin against MRSA, (2) ciprofloxacin and enoxacin against MSSA, and (3) ciprofloxacin against SE in which all colony counts increased one to three logs in 24 h. When quinolone time-kill trials did not show a decrease in colony counts at 24 h, the MIC's for the 24 h growth showed a four- to 250-fold increase when compared with pre-trial MICs. No selection or emergence of resistant organisms was found with fleroxacin, amifloxacin or ofloxacin.

Inhibition of Legionella pneumophila multiplication within human macrophages by fleroxacin.

The susceptibility of Legionella pneumophila to a new quinolone, fleroxacin, was studied in both an extra- and an intracellular system. The activity of fleroxacin was compared with that of erythromycin, cefoxitin, and rifampicin. In the extracellular system, erythromycin inhibited while cefoxitin killed the organism. Extracellularly, fleroxacin performed similarly to cefoxitin. Rifampicin was initially bactericidal for L. pneumophila but resistant bacteria emerged at 48 h. The Horwitz monocyte model was used for studies of intracellular antimicrobial activity. At ten times the MIC, cefoxitin did not inhibit intracellular L. pneumophila. Fleroxacin was as active as erythromycin and rifampicin in inhibiting intracellular L. pneumophila. No intracellular, rifampicin-resistant L. pneumophila emerged. Addition of rifampicin to cefoxotin, erythromycin or fleroxacin provided neither synergy nor antagonism.

Structures suggesting cell-wall-deficient forms detected in circulating erythrocytes by fluorochrome staining.

Cell-wall-deficient (CWD) forms of bacteria are associated with certain cases of idiopathic septicemia. In this preliminary study of blood examined immediately after venipuncture, structures with a morphology characteristic of CWD forms were seen parasitizing the erythrocytes. These inclusions were usually circumferential, but in some cases they protruded from the red cells. The CWD forms were detected by staining with Gould's rhodamine-labeled muramidase, which reacted similarly to acridine orange but with greater specificity. A blocking test, employing unlabeled muramidase, indicated the specificity of the reaction between muramidase and the microbial substrate. Reaction of the forms with muramidase indicates their bacterial, rather than mycoplasmal, nature. Thus in vivo CWD forms have a detectable component of muramic acid, at least in certain cases. Sixty-eight individuals with a diagnosis of fever of unknown origin were tested, with 51 nondebilitated individuals serving as controls. More intraerythrocytic forms reacting with muramidase were found in the patients than in the controls. Nearly 40% of the cases had a relatively high incidence of erythrocyte parasitism. In some instances when freshly drawn blood was examined, the structures, which appear to be microbial, extended in rhizoid filaments from the erythrocytes.

Community-acquired methicillin-resistant Staphylococcus aureus infections: a new source for nosocomial outbreaks.

Over a 19-month period, 165 patients with 183 infections caused by community-acquired, methicillin-resistant Staphylococcus aureus were seen at Henry Ford Hospital in Detroit, Michigan. The proportion of community-acquired staphylococcal infections resistant to methicillin rose from 3 % in March 1980 to 38% in September 1981. Drug abuse, serious underlying illness, previous antimicrobial therapy, and previous hospitalization were all associated with the development of this infection. Concurrent with the community epidemic was a nosocomial epidemic of methicillin-resistant S. aureus infection, which accounted for 30.6% of all nosocomial staphylococcal infections in January 1981. Control measures that included isolation, discharge precautions for carriers, and eradication of employee carriage were effective in preventing nosocomial transmission. The prevalence of methicillin-resistant S. aureus carriage among employees was 0.7%. Methicillin-resistant S. aureus may originate in the community as well as in the hospital, and presents a threat to patients in both settings.

Antimicrobial susceptibility of Legionella pneumophila Serogroups I--IV.

Strains of Legionella pneumophila from 10 geographic areas were evaluated for their in vitro susceptibility to 14 antimicrobial agents. Included in this study were clinical and environmental isolates as well as strains from all 4 known serogroups. The minimal inhibitory concentration was established by agar dilution with a Steers replicator. The inhibitory index was then calculated considering the mean peak serum level for the associated antibiotic. Rifampicin, cefoxitin, chloramphenicol, ticarcillin, and parenteral erythromycin had the highest inhibitory indices. The only difference among serogroups was the increased susceptibility among serogroup II isolates to the penicillins and the increased susceptibility of serogroups III and IV to sulfamethoxazole-trimethoprim. Though there have been recent reports of the inadequacy of oral erythromycin in clinical cases of Legionnaires' disease, there was no erythromycin resistance noted among the 14 isolates tested.

In vitro susceptibility of gram-positive cocci to paldimycin.

Paldimycin (U-70138F) is a new antimicrobial agent with activity against gram-positive cocci. Clinical isolates of staphylococci and streptococci were tested. MICs were higher in Mueller-Hinton broth than in nutrient broth. Change in pH had minimal effect on the MICs in either broth. When inoculum size was varied, an inoculum effect was observed. The gram-positive cocci tested were generally more susceptible to paldimycin than to vancomycin.

In-vitro susceptibility of gram-positive cocci to LY146032 teicoplanin, sodium fusidate, vancomycin, and rifampicin.

LY146032, a new antimicrobial agent with activity against Gram-positive cocci, was tested against methicillin-susceptible and methicillin-resistant Staphylococcus aureus, methicillin-susceptible and methicillin-resistant Staph. epidermidis, Staph. saprophyticus, and Streptococcus faecalis. MIC90s in cation-supplemented Mueller Hinton broth by the microdilution broth method were less than 1.0 mg/l for all organisms tested. Increasing or decreasing the inoculum size did not appreciably effect the MIC50 or MIC90 for any organism group nor did decreasing the incubation temperature. The addition of sodium chloride to the test system did not appreciably effect the susceptibility of methicillin-resistant Staph. aureus to LY146032. All organisms were 4 to 32 times more susceptible to LY146032 than to vancomycin. The Staph. aureus had LY146032 susceptibility patterns which were similar to those of teicoplanin and sodium fusidate. LY146032 was 4-16 times more active than teicoplanin against Staph. saprophyticus and Staph. epidermidis while teicoplanin was 8-16 times more active than LY146032 against Str. faecalis.

Failure of therapy in pseudomonas endocarditis: selection of resistant mutants.

Despite optimal use of available antibacterial agents, endocarditis due to Pseudomonas aeruginosa is commonly associated with poor response to medical treatment. Two patients are described in whom emergence of resistance to beta-lactam antibiotics was associated with clinical failure. A subpopulation of resistant mutants (10(-7)) was found within the initial, apparently sensitive population of bacteria. These resistant mutants were similar to posttherapy isolates in their increased production of beta-lactamase and in their identical pattern of resistance to beta-lactam antibiotics. Moreover, the only beta-lactamase produced was type Id, and this enhanced production proved to be constitutive. A relatively large inoculum (10(6) colony-forming units/g of tissue) of bacteria was found postoperatively in the heart valves of both patients. The failure to respond is postulated to be due to the selection of these producers of high levels of beta-lactamase in a large bacterial inoculum.

An outbreak of gentamicin-resistant Klebsiella pneumoniae: analysis of control measures.

In April 1978, a strain of gentamicin-resistant Klebsiella pneumoniae (GRK) was introduced into the neonatal intensive care unit of Henry Ford Hospital. An additional ten cases of GRK occurred over the subsequent 16 months and intestinal colonization occurred in up to 91% of admissions per month. All GRK were susceptible to amikacin and were capsular serotype 19. Though hand contamination of hospital personnel with GRK was documented, increased handwashing practices did not reduce colonization rates of neonates with the epidemic strain. Intestinal carriage persisted for up to ten months and could not be eradicated by administering oral colistin sulfate. Discontinuation of gentamicin and utilization of amikacin were associated with a significant reduction in colonization with GRK (p less than 0.05). However, the only control measure that prevented both new cases and colonization with the epidemic strain was the utilization of a strict cohort system.

Evaluation of the sterility and stability of insulin from multidose vials used for prolonged periods.

Diabetic patients frequently use their insulin vials for prolonged periods, even though antibacterial preservatives used in multidose insulin vials are not required to be effective beyond 28 days. For this reason, we evaluated the antibacterial activity present in multidose insulin vials for up to 50 days. Multidose lente insulin vials were inoculated with S. aureus and P. aeruginosa. Vials incubated at room temperature (21 degrees C) were sterile by 48 hours, whereas when they were incubated at refrigerator temperatures (4 degrees C), S. aureus contamination persisted up to the 17th day and P. aeruginosa were killed after 10 days. The same vials were serially contaminated on days 17, 30, and 50, and a similar antibacterial effect was maintained. Sixty-nine multidose insulin vials used for an average of 53 days were cultured. Eight vials demonstrated bacterial contamination with 1 cfu/ml of S. epidermidis or Propionibacterium acnes. No endotoxin was detected in the multidose vials used for more than 28 days. Insulin assays on 40 multidose insulin vials used for more than 28 days showed an average insulin content of 101.6 +/- 1.9 units/ml. This study did not demonstrate significant bacterial contamination, endotoxin activity, or insulin degradation of multidose insulin in vials used for periods longer than 28 days. In addition, antibacterial preservatives were more effective at room temperature than at refrigerator temperature; thus, the practice of patients not refrigerating insulin vials is sensible.

Methicillin-resistant Staphylococcus aureus. Epidemiologic observations during a community-acquired outbreak.

Infection with strains of methicillin-resistant Staphylococcus aureus occurred in 40 patients at time of admission to a large urban hospital from March to December 1980. Community-acquired methicillin-resistant S. aureus infections occurred in 24 drug abusers and 16 nonabusers. Patients with infections had a longer mean hospitalization and previously had received antimicrobial therapy more frequently than control subjects. Drug abusers with infections had been treated with cephalosporins more often than control subjects (P less than 0.05). Phage typing of 32 isolates showed that 21 were linked by a common phage type (29/52/80/95). Transmission of methicillin-resistant S. aureus from community-acquired cases occurred in the hospital. By January 1981, methicillin-resistant S. aureus accounted for 30.6% of nosocomial S. aureus infections at Henry Ford Hospital. Methicillin-resistant S. aureus infection may arise in the community as well as in the hospital and has the potential to disseminate in both settings.