Antibiotic-dependent correlation between drug-induced killing and loss of luminescence in Streptococcus gordonii expressing luciferase

Measuring antibiotic-induced killing relies on time-consuming biological tests. The firefly luciferase gene (luc) was successfully used as a reporter gene to assess antibiotic efficacy rapidly in slow-growing Mycobacterium tuberculosis. We tested whether luc expression could also provide a rapid evaluation of bactericidal drugs in Streptococcus gordonii. The suicide vectors pFW5luc and a modified version of pJDC9 carrying a promoterless luc gene were used to construct transcriptional-fusion mutants. One mutant susceptible to penicillin-induced killing (LMI2) and three penicillin-tolerant derivatives (LMI103, LMI104, and LMI105) producing luciferase under independent streptococcal promoters were tested. The correlation between antibiotic-induced killing and luminescence was determined with mechanistically unrelated drugs. Chloramphenicol (20 times the MIC) inhibited bacterial growth. In parallel, luciferase stopped increasing and remained stable, as determined by luminescence and Western blots. Ciprofloxacin (200 times the MIC) rapidly killed 1.5 log10 CFU/ml in 2-4 hr. Luminescence decreased simultaneously by 10-fold. In contrast, penicillin (200 times the MIC) gave discordant results. Although killing was slow (< or = 0.5 log10 CFU/ml in 2 hr), luminescence dropped abruptly by 50-100-times in the same time. Inactivating penicillin with penicillinase restored luminescence, irrespective of viable counts. This was not due to altered luciferase expression or stability, suggesting some kind of post-translational modification. Luciferase shares homology with aminoacyl-tRNA synthetase and acyl-CoA ligase, which might be regulated by macromolecule synthesis and hence affected in penicillin-inhibited cells. Because of resemblance, luciferase might be down-regulated simultaneously. Luminescence cannot be universally used to predict antibiotic-induced killing. Thus, introducing reporter enzymes sharing mechanistic similarities with normal metabolic reactions might reveal other effects than those expected.

[Antibiotic prophylaxis for late blood-borne infections of joint prostheses]

By analogy with endocarditis prophylaxis, patients with joint prostheses are often given antibiotics before invasive procedures or dental treatment. However, this analogy is not justified: The pathogenesis and bacterial spectrum of infections of artificial joints differ from those of endocarditis. Since the efficacy of administering prophylactic antibiotics to patients with joint prostheses has never been scientifically proven, there is no general indication for such prophylaxis. On the other hand, infections in other parts of the body should be actively sought and treated promptly. Prophylactic antibiotic administration may be appropriate in individual cases during a procedure in patients who are at increased risk of a haematogenic prosthesis infection as a result of bacteraemia. For operations routinely performed under perioperative antibiotic cover, the same prophylaxis should also be used for patients with joint prostheses.

Treatment of joint prosthesis infection in accordance with current recommendations improves outcome

BACKGROUND: Recently recommended treatment modalities for prosthetic joint infection (PJI) were evaluated. METHODS: A retrospective cohort analysis of 68 patients with PJI of hip or knee who were treated from 1995 through 2004 was conducted at the University Hospital Bern (Bern, Switzerland). RESULTS: A 2-stage exchange was the most frequent (75.0%) surgical strategy, followed by retention and debridement (17.6%), 1-stage exchange (5.9%), and resection arthroplasty or suppressive antimicrobial treatment (1.5%). The chosen strategy was in 88% agreement with the recommendations. Adherence was only 17% for retention and debridement and was 0% for 1-stage exchange. Most PJIs (84%) were treated with an adequate or partially adequate antimicrobial regimen. Recurrence-free survival was observed in 51.5% of PJI episodes after 24 months of follow-up. The risk of treatment failure was significantly higher for PJI treated with a surgical strategy other than that recommended (hazard ratio, 2.34; 95% confidence interval, 1.10-4.70; P = .01) and for PJIs treated with antibiotics not corresponding to recommendations (hazard ratio, 3.45; confidence interval, 1.50-7.60; P = .002). Other risk factors associated with lack of healing were a high infection score at the time of diagnosis (hazard ratio, 1.29; 95% confidence interval, 1.10-1.40; P < .001) and presence of a sinus tract (hazard ratio, 2.35; 95% confidence interval, 1.10-5.0; P = .02). CONCLUSIONS: Our study demonstrates the value of current treatment recommendations. Inappropriate choice of conservative surgical strategies (such as debridement and retention) and inadequate antibiotic treatment are associated with failure.

[Antibiotic resistance: infections of the upper respiratory tract and bronchi. When are antibiotics necessary?]

Antimicrobial resistance among respiratory tract pathogens has become an increasing problem worldwide during the last 10-20 years. The wide use of antimicrobial agents in ambulatory practice has contributed to the emergence and spread of antibiotic-resistant bacteria in the community, namely Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. The pneumococcus has developed resistance to most antibiotics used for its treatment. Classes with important resistance problems include the beta-lactams, the macrolides, the lincosamides, trimethoprim-sulfamethoxazole, and the tetracyclines. Unfortunately, resistance to more than one class of antibiotics is common. In Haemophilus influenzae and Moraxella catarrhalis, resistance to beta-lactam antibiotics is the main concern currently. It is important to know the local resistance pattern of the most common respiratory tract pathogens in order to make reasonable recommendations for an empirical therapy for respiratory tract infection, when antibiotic therapy is indeed indicated.

Relationship between antibiotic concentration in bone and efficacy of treatment of staphylococcal osteomyelitis in rats: azithromycin compared with clindamycin and rifampin

We examined the effect of azithromycin (CP-62,993), a new oral macrolide-like antibiotic, alone and in combination with rifampin, as treatment for experimental staphylococcal osteomyelitis. Clindamycin was used as a comparison drug. Rats (n = 10 to 15 per group) were infected by direct instillation of Staphylococcus aureus into the tibial medullary cavity. After 10 days, 21-day treatments with azithromycin (50 mg/kg of body weight, once daily, by the oral route), rifampin (20 mg/kg, once daily, subcutaneously), or clindamycin (90 mg/kg, three times daily, by the oral route) were started. The drugs were used singly or in combination (azithromycin plus rifampin or clindamycin plus rifampin). Peak azithromycin concentrations in bone were > 30 times higher than levels in serum, but the drug had little effect on final bacterial titers (5.13 +/- 0.46 log10 CFU/g of bone; for controls, 6.54 +/- 0.28 log10 CFU/g). Clindamycin was more active than azithromycin (3.26 +/- 2.14 log10 CFU/g of bone; 20% of sterilized bones), but rifampin was the most active single drug (1.5 +/- 1.92 log10 CFU/g; 53% of sterilized bones). Therapy with rifampin or clindamycin alone was associated with the emergence of resistance. Rifampin plus azithromycin (0.51 +/- 1.08 log10 CFU/g of bone; 80% of sterilized bones) and rifampin plus clindamycin (0.87 +/- 1.34 log10 CFU/g of bone; 66% of sterilized bones) were the most active regimens. Thus, azithromycin is ineffective as a single drug for the treatment of experimental staphylococcal osteomyelitis, despite high levels in bone that markedly exceeded the MIC, but it may be an attractive partner drug for rifampin.

Influence of antibiotic dose, dosing interval, and duration of therapy on outcome in experimental pneumococcal meningitis in rabbits

We examined the influence of several pharmacokinetic parameters on cure rates in rabbits with experimental pneumococcal meningitis. When the duration of treatment was kept constant, cure rates improved as the individual dose of ampicillin was increased. On the other hand, when four doses of ampicillin at 60 mg/kg of body weight, producing peak concentrations in cerebrospinal fluid (CSF) of approximately 40 times the MBC, were administered at intervals of 24 instead of 4 h and the duration of therapy was thus prolonged from 12 to 72 h, cure rates also increased (85 versus 25%; P less than 0.01). These high cure rates were achieved even though bacterial titers in CSF 24 h after the first dose had reached levels similar to those present at the beginning of therapy. Cure in these animals was explained by the fact that the second ampicillin dose reduced bacterial titers in CSF significantly more than did the first dose (5.2 versus 2.5 log10 CFU/ml; P less than 0.02). The clinical relevance of these observations remains to be determined.

Antibiotic therapy, endotoxin concentration in cerebrospinal fluid, and brain edema in experimental Escherichia coli meningitis in rabbits

We investigated the effect of cefotaxime and chloramphenicol on endotoxin concentrations in cerebrospinal fluid (CSF) and on the development of brain edema in rabbits with Escherichia coli meningitis. Both antibiotics were similarly effective in reducing bacterial titers. Cefotaxime, but not chloramphenicol, induced a marked increase of endotoxin in CSF, from log10 1.5 +/- 0.8 to log10 2.8 +/- 0.7 ng/ml (P less than .01). This result was associated with an increase in brain water content (405 +/- 12 g of water/100 g of dry weight compared with 389 +/- 8 g in untreated controls; P less than .01), whereas in animals treated with chloramphenicol, brain water content was identical to controls. The cefotaxime-induced increase in endotoxin concentration and brain edema were both neutralized by polymyxin B, which binds to the lipid A moiety of endotoxin, or by a monoclonal antibody to lipid A. These results indicate that treating gram-negative bacillary meningitis with selected antibiotics induces increased endotoxin concentrations in CSF that are associated with brain edema.

The timing of surgical antimicrobial prophylaxis

OBJECTIVE: To obtain precise information on the optimal time window for surgical antimicrobial prophylaxis. SUMMARY BACKGROUND DATA: Although perioperative antimicrobial prophylaxis is a well-established strategy for reducing the risk of surgical site infections (SSI), the optimal timing for this procedure has yet to be precisely determined. Under today's recommendations, antibiotics may be administered within the final 2 hours before skin incision, ideally as close to incision time as possible. METHODS: In this prospective observational cohort study at Basel University Hospital we analyzed the incidence of SSI by the timing of antimicrobial prophylaxis in a consecutive series of 3836 surgical procedures. Surgical wounds and resulting infections were assessed to Centers for Disease Control and Prevention standards. Antimicrobial prophylaxis consisted in single-shot administration of 1.5 g of cefuroxime (plus 500 mg of metronidazole in colorectal surgery). RESULTS: The overall SSI rate was 4.7% (180 of 3836). In 49% of all procedures antimicrobial prophylaxis was administered within the final half hour. Multivariable logistic regression analyses showed a significant increase in the odds of SSI when antimicrobial prophylaxis was administered less than 30 minutes (crude odds ratio = 2.01; adjusted odds ratio = 1.95; 95% confidence interval, 1.4-2.8; P < 0.001) and 120 to 60 minutes (crude odds ratio = 1.75; adjusted odds ratio = 1.74; 95% confidence interval, 1.0-2.9; P = 0.035) as compared with the reference interval of 59 to 30 minutes before incision. CONCLUSIONS: When cefuroxime is used as a prophylactic antibiotic, administration 59 to 30 minutes before incision is more effective than administration during the last half hour.

Faulted Structures in Li Ion Exchanged NaMO2 (M=Ni(0.25)Mn(0.75))

A family of LiMO2 materials (M=Ni0.25Mn0.75) was prepared from Na1.2-xLixMO∂ precursors (0≤x≤0.6) via ion exchange. The resulting IE products were examined via XRD and compared to simulated XRD patterns produced using DIFFax to determine the defect structures resulting from the IE process. For the 0.1≤x≤0.6 materials, it is observed that there are 3 LiMO2 sub-phases with different Li contents present. As the amount of Li in the precursor increases, the amount of each phase changes resulting in a net shift to higher 2-theta; corresponding to an overall decrease in lattice parameter, approaching the theoretical values for LiMO2. Additionally, as x increases, the probability of O3-type shifting increases, most likely due to an increase in the amount O3-Li2MO3 minority phase which acts to weaken bonds in the TM layer, allowing the O3 shift to occur more easily. For the x=0 IE product, it was seen that the product had an ~O2-type structure, but with lattice parameters closer to those expected for a NaMO2 material.

Copper Collar: Montana's 75 Years as a Corporate Colony – Dr. Harry Fritz & Dr. Robert Swartout “In the Crucible of Change”

Abstract to be posted.

Outcome of transmetatarsal amputations in diabetics using antibiotic beads

BACKGROUND: Diabetic patients with transmetatarsal amputation (TMA) for chronic forefoot ulceration or necrosis are at high risk for postoperative skin breakdown and subsequent amputation. Locally applied antibiotics may reduce the revision rate and improve the outcome. MATERIAL AND METHODS: In a retrospective comparative study, 60 diabetic patients (65 feet) with forefoot ulceration or necrosis were treated with TMA by three surgeons in three hospitals. In the "beads group'' (46 patients, 49 feet) TMA was combined with local application of bioabsorbable, tobramycin impregnated calcium sulphate beads (OsteoSet-T beads, Wright Medical, Memphis, TN) as a single-stage procedure. The remaining 16 patients had transmetatarsal amputation without beads at the surgeon's discretion and acted as a control group. For all patients, time to healing, length of hospital stay, number of revisions for wound breakdown and conversions to a higher-level amputation were retrospectively reviewed. Of the 60 patients 17 had died and three were lost to followup, leaving 40 patients available for latest followup at 29 months. The Foot ; Ankle Outcome Score, Foot Function index, SF-36, and Comorbidity score were recorded. RESULTS: The revision rate for wound breakdown after TMA was 8.2% (4/49) in the beads group, and 25% (4/16) in the control group (p<0.05). At latest followup, 27% (13/49) in the beads group, and 25% (4/16) in the control group had to be converted to transtibial amputation. Patients in the beads group scored worse for activities of daily living in the FAOS and SF-36 (p < 0.05), and demonstrated more health problems in the Comorbidity scores (not significant), indicating sicker individuals in the beads group. CONCLUSION: Bioabsorbable calcium sulphate antibiotic beads may be a useful addition for TMA for patients with non-healing diabetic ulcerations of the forefoot. The single-stage procedure could have a significant impact on the management of diabetic forefoot ulcerations by preventing additional hospital stays, improving the patient's quality of life and minimizing cost.

Early serum procalcitonin, interleukin-6, and 24-hour lactate clearance: useful indicators of septic infections in severely traumatized patients

BACKGROUND: Elevated lactate and interleukin-6 (IL-6) levels were shown to correlate with mortality and multiple organ dysfunction in severely traumatized patients. The purpose of this study was to test whether an association exists between 24-hour lactate clearance, IL-6 and procalcitonin (PCT) levels, and the development of infectious complications in trauma patients. METHODS: A total of 1757 consecutive trauma patients with an Injury Severity Score (ISS) > 16 admitted over a 10-year period were retrospectively analyzed over a 21-day period. Exclusion criteria included death within 72 h of admission (24.5%), late admission > 12 h after injury (16%), and age < 16 years (0.5%). Data are stated as the median (range). RESULTS: Altogether, 1032 trauma patients (76.2% male) with an average age of 38 years, a median ISS of 29 (16-75), and an Acute Physiology, Age, and Chronic Health Evaluation (APACHE) II score of 14 (0-40) were evaluated. The in-hospital mortality (>3 days) was 10%. Patients with insufficient 24-hour lactate clearance had a high rate of overall mortality and infections. Elevated early serum procalcitonin on days 1 to 5 after trauma was strongly associated with the subsequent development of sepsis (p < 0.01) but not with nonseptic infections. The kinetics of IL-6 were similar to those of PCT but did differentiate between infected and noninfected patients after day 5. CONCLUSIONS: This study demonstrates that elevated early procalcitonin and IL-6 levels and inadequate 24-hour lactate clearance help identify trauma patients who develop septic and nonseptic infectious complications. Definition of specific cutoff values and early monitoring of these parameters may help direct early surgical and antibiotic therapy and reduce infectious mortality.