Octavio V. Martinez

Incidence of clostridial contamination in donors’ musculoskeletal tissue

Reports of infection by Clostridium sordellii associated with allograft transplantation have generated considerable interest. We report our experience in recognising clostridial contamination in cadaver donors of musculoskeletal tissue. Tissues obtained from 795 consecutive donors were excised using standard surgical techniques. Samples of blood and bone marrow were also obtained. Donors with clostridia recovered from any site were matched with the preceding donor without clostridia as a procedural and environmental control. The histories of the donors were analysed to determine which variables had a relationship to contamination by running a contingency table and chi-squared test on the variables against the event of a donor being contaminated. Sixty-four donors (8.1%) had clostridia, most commonly C. sordellii. Clostridia were grown from the blood, marrow and tissue samples of 52, 37 and 30 donors, respectively. In eight cases, they were cultured from the tissue samples alone. There was no significant difference in age or gender between the contaminated donors and the control group. Open wounds were more common in control than in contaminated subjects, but only death by drowning in the contaminated group was statistically significant (p = 0.02). The time between death and the excision of tissue which was contaminated (16 hrs 10 mins) compared with control (11 hrs 10 mins) donors was also significant (p < 10(-6)). We conclude that there is clostridial contamination in a significant number of tissue donors, particularly with increasing time between death and tissue excision. Among the most commonly encountered species is C. sordellii. Multiple microbiological cultures, including blood, are necessary in order to identify clostridial contamination.

Tissue distribution of antibiotics in the intervertebral disc

Study Design This study analyzed the distribution of antibiotics within the intervertebral disc of rabbits. Specimens were tested with specific antibodies against antibiotics using an immunofluorescent technique. Objectives The results were correlated to provide a rationale for perioperative prophylaxis of infection. Summary of Background Data Several groups of investigators and the recent data from our laboratory showed quantitative changes in penetration of antibiotics into intervertebral disc. No previous study has assessed antibiotic distribution in anulus fibrosus and nucleus pulposus. Methods Discs were obtained from rabbits after intravenous injection of penicillin or gentamicin. Antibiotics were localized in tissue sections using specific antibodies with a immunofluorescent method. Result Penicillin (negatively charged) and gentamicin (positively charged) penetrated the neutrally charged anulus fibrosus, but penicillin had less ability than gentamicin to penetrate into the negatively charged nucleus pulposus. Conclusion Our data suggest that penetration and distribution of antibiotics into avascular intervertebral disc is significantly influenced by the charge of antibiotics.

Risk and detection of pulmonary artery catheter-related infection in septic surgical patients

Specimen cultures were evaluated in 49 catheterized patients who had a known focus of infection (primarily intra-abdominal peritonitis). Bacteria were recovered from 2% of flush solutions, 14% of transducer domes, 18% of diaphragms, and 24% of cardiac output fluids; however, these bacteria were not found in cultures of the pulmonary artery (PA) catheter segments. The rates of positive PA catheter-aspirate cultures were 30.6% on day 1, 20.4% on day 2, and 32.7% on day 3 (not statistically different). PA catheter-aspirate cultures had a sensitivity of 5.7% and a positive predictive value of 30% for catheter-related infection, and 15% sensitivity and 40% positive predictive value for peripheral bacteremia. While 95% (55 of 58) of the catheter- aspirate cultures were false-positives, only 0.5% (3 of 588) were true-positives. Peripheral blood cultures were positive in 10% of the patients, but the catheter segments were sterile or grew different organisms. Arterial line cultures had zero sensitivity and predictive value to detect catheter-related infection, and 15% sensitivity and 40% predictive value to detect peripheral bacteremia. Thus, PA catheter-aspirate cultures, routine peripheral blood cultures, and arterial cultures cannot be recommended to detect PA catheter-related infection. Catheter-related infection confirmed by catheter-segment cultures was 10.2% when the PA catheters were removed after 73 ± 6.5 (SD) h. Bacteria from catheter- segment cultures corresponded to those from the primary infection site.

Bacteriuria in the catheterized surgical intensive care patient

A prospective microbiologic evaluation of the urine was conducted on 100 catheterized ICU patients. Eight subjects had positive initial bladder urine cultures and were eliminated from further study. The remaining 92 patients were catheterized for up to 22 days, mean 4.8 ± 4.3 (SD). During the first 5 days, 57 (62%) patients completed the surveillance protocol; seven (12.3%) of these had bladder bacteriuria. Of 20 patients with positive urine cultures, six had microorganisms in the collection bag urine alone. The remaining 14 had organisms both in the bladder and in the bag urine. The urine collection bag was the apparent source of microorganisms in the bladder urine in only three cases. The daily incidence of new cases and the cumulative rate of bladder bacteriuria remained below 7% and 22%, respectively, during the first week of catheterization. These rates are similar to those previously reported for various other patient groups outside the ICU setting. Frequent microbiologic monitoring of the urine seems to be unnecessary for most ICU patients because of the short duration of catheterization.

Penetration of glycopeptide antibiotics in nucleus pulposus

The penetration of the glycopeptide antibiotics vancomycin and teicoplanin into the nucleus pulposus of rabbits was studied. Blood samples were obtained at 0.5, 1, 4, 8, and 24 hours after intravenous administration of 30 mg/kg vancomycin or 16 mg/kg teicoplanin. Concentrations of antibiotics were determined in tissue specimens and serum samples by fluorescence polarization immunoassays. Antimicrobial activity in the nucleus pulposus was determined with an agar diffusion method using a strain of Micrococcus luteus as the indicator organism. A peak concentration of vancomycin in the nucleus pulposus was attained 8 hours after drug administration. Teicoplanin reached its maximum level and plateaued 1 and 2 hours, respectively, after injection, and it remained unchanged for the rest of the study. This microbiologic analysis showed that the nucleus pulposus contained an antimicrobial level of glycopeptide antibiotics after administration. Because rabbit nucleus pulposus is similar anatomically to that of humans, these results may have implications regarding the timing and choice of antibiotic administration.

Biliary excretion of aztreonam in patients with biliary tract disease.

The biliary excretion of aztreonam was studied in 10 post-cholecystectomy patients with T-tube biliary drainage (group A) and four other subjects with obstructive biliary tract disease who had recent placement of external biliary drainage (group B). Maximum biliary levels ranged from 9.7 to 88.2 micrograms/ml (mean, 42.9 +/- 7.9 micrograms/ml) and occurred 2.4 h after injection of a single 1-g dose intravenously. Peak biliary levels observed in group B patients were approximately one-third those in group A. Cumulative 12-h biliary excretion (group B) accounted for 0.18 +/- 0.06% of the total dose. In the same period, urinary excretion accounted for 65 to 72% of the total dose. The lower biliary levels of aztreonam observed in group B patients relative to those in group A suggest that in patients with total biliary tract obstruction the liver may not recover full secretory capacity, at least within 3 to 7 days after biliary decompression.

Detection of Group B Streptococci in Lim Broth by Use of Group B Streptococcus Peptide Nucleic Acid Fluorescent In Situ Hybridization and Selective and Nonselective Agars

ABSTRACT The sensitivity, specificity, and positive and negative predictive values for the detection of group B streptococci from Lim enrichment broth with sheep blood agar (SBA), with selective Streptococcus agar (SSA), and by a peptide nucleic acid fluorescent in situ hybridization (PNA FISH) assay were as follows: for culture on SBA, 68.4%, 100%, 100%, and 87.9%, respectively; for culture on SSA, 85.5%, 100%, 100%, and 94.1%, respectively; and for the PNA FISH assay, 97.4%, 98.3%, 96.1%, and 98.9%, respectively.

Effects of treatment with pentoxifylline on the cardiovascular manifestations of group B streptococcal sepsis in the piglet

Pentoxifylline (PTXF) is a methylxanthine derivative which modifies leukocyte function and inhibits tumor necrosis factor (TNF)-α release. As TNF-α is considered a proximal mediator in the cascade leading to septic shock, we evaluated the ability of PTXF to attenuate the cardiovascular manifestations of sepsis secondary to an infusion of group B β-hemolytic streptococci (GBS). Fifteen anesthetized, mechanically ventilated piglets(weight, 2815 ± 552 g) were randomly assigned to a treatment group which received a continuous infusion of PTXF (5 mg/kg/h) beginning 30 min after GBS (7.5 × 108 colony-forming units/kg/min) administration was started or to a control group which received GBS plus saline as placebo. Comparison of the hemodynamic measurements and arterial blood gases over the first 120 min of bacterial infusion for treatment and control groups revealed the following statistically significant differences (120-min values presented): cardiac output was significantly higher in the PTXF group (0.159± 0.035 versus 0.09 ± 0.026 L/kg/min; p < 0.05) as was stroke volume (0.54 ± 0.11 versus 0.27 ± 0.126 mL/kg/beat; p < 0.01). Pulmonary and systemic vascular resistances remained lower in the PTXF-treated animals (167 ± 45versus 233 ± 69 mm Hg/L/kg/min; p < 0.03) and(427 ± 162 versus 828 ± 426 mm Hg/L/kg/min;p < 0.03, respectively). Median survival time was significantly longer in the PTXF group (180 versus 120 min; p < 0.05). In an additional group of animals, PTXF administration before GBS infusion revealed no attenuation in the rise of TNF-α, accompanying sepsis. These data demonstrate that treatment with PTXF may ameliorate some of the deleterious hemodynamic manifestations of GBS sepsis and result in improved survival in a young animal model without significantly modifying plasma TNF-α levels.

Hemodynamic effects of conventional and high frequency oscillatory ventilation in normal and septic piglets

The cardiovascular effects of high frequency oscillation (HFO) and conventional ventilation (CMV) were evaluated in 10 piglets prior to and during an infusion of group B streptococci (GBS). Animals were randomized to begin ventilation with either HFO or CMV. Arterial blood gases, cardiac output (CO), and pulmonary artery (Ppa), pulmonary wedge (Ppw) and arterial blood pressures were measured. These values were recorded at a mean airway pressure (MAP) of 2 cm H2O for both modes of ventilation after which a continuous infusion of GBS (4 X 10(7) CFU/kg/min) was begun. MAP was increased in both ventilators in the following sequence: 4, 8 and 12 cm H2O. Prior to GBS infusion, HFO was associated with small but significant changes in hemodynamic parameters when compared to CMV for the following: Ppa (15 +/- 4 vs. 13 +/- 4.0 mm Hg; p less than 0.03), Ppw (3 +/- 1 vs. 2 +/- 1 mm Hg; p less than 0.02), and CO (0.24 +/- 0.08 vs. 0.25 +/- 0.09 l/min/kg; p less than 0.05). Similar statistically significant increases in Ppa (p less than 0.005) and Ppw (p less than 0.0001), and decrease in CO (p less than 0.007) were present during GBS infusion when animals were ventilated with HFO, irrespective of the MAP used. Our results suggest that the use of HFO in both normal piglets and those receiving an infusion of GBS results in mild but consistent impairment in cardiovascular function compared to CMV. In summary, these data demonstrate that HFO has no beneficial effect compared to CMV at similar MAP in the management of the septic piglet model and may in fact further compromise the animals hemodynamic status.

Efficacy of linezolid versus vancomycin in the treatment of methicillin-resistant Staphylococcus aureus discitis: a controlled animal model.

Study Design. A rabbit model was used to assess the efficacy of linezolid and vancomycin for the treatment of discitis due to methicillin-resistant Staphylococcus aureus (MRSA). Nontreated controls were used for comparison. Objective. The purpose of this study was to determine if there was a therapeutic difference between using linezolid and vancomycin in the treatment of MRSA discitis. Summary of Background Data. Vancomycin is currently the gold standard treatment for medical management of MRSA discitis. Linezolid is a relatively new drug that has been approved for treatment of MRSA infections, but currently there is no research demonstrating its efficacy at treating infections of the disc space. Methods. Twenty-four rabbits were inoculated with MRSA at two adjacent lumbar disc spaces via an anterior retroperitoneal approach. Six rabbits were to receive only pain medication and to serve as controls. Ten rabbits were assigned to a 5-day course of intravenous vancomycin, and 8 were assigned to a 5-day course of intravenous linezolid. Disc spaces were sent for quantitative culture after the 5-day treatment course. Results. The mean culture growth for the disc spaces was not statistically different between the linezolid treated group and the nontreated controls. While vancomycin treatment did lead to lower bacterial loads when compared with controls, the reduction was not statistically significant. When bacterial counts for the vancomycin group and linezolid group were compared, vancomycin treatment resulted in less bacterial growth. This difference was statistically significant. Conclusions. Linezolid is a clinically attractive alternative to vancomycin due to its mild side effect profile and oral bioavailability. However, in this MRSA discitis model with a short treatment course, vancomycin was superior to linezolid.