The use of extrapolation based on modeling and simulation to support high-dose regimens of ceftaroline fosamil in pediatric patients with complicated skin and soft-tissue infections

A model-informed drug development approach was used to select ceftaroline fosamil high-dose regimens for pediatric patients with complicated skin and soft-tissue infections caused by Staphylococcus aureus with a ceftaroline minimum inhibitory concentration (MIC) of 2 or 4 mg/L. Steady-state ceftaroline concentrations were simulated using a population pharmacokinetics (PK) model for ceftaroline fosamil and ceftaroline including data from 304 pediatric subjects and 944 adults. Probability of target attainment (PTA) for various simulated pediatric high-dose regimens and renal function categories were calculated based on patients achieving 35% fT>MIC (S. aureus PK/pharmacodynamic target for 2-log10 bacterial killing). For extrapolation of efficacy, simulated exposures and PTA were compared to adults with normal renal function receiving high-dose ceftaroline fosamil (600 mg 2-h infusions every 8 h). For safety, predicted ceftaroline exposures were compared with observed pediatric and adult data. Predicted ceftaroline exposures for the approved pediatric high-dose regimens (12, 10, or 8 mg/kg by 2-h infusions every 8 h for patients aged >2 to <18 years with normal/mild, moderate, or severe renal impairment, respectively; 10 mg/kg by 2-h infusions every 8 h for patients aged ≥2 months to <2 years with normal renal function/mild impairment) were well matched to adults with normal renal function. Median predicted maximum concentration at steady state (Cmax,ss ) and area under the plasma concentration-time curve over 24 h at steady state pediatric to adult ratios were 0.907-1.33 and 0.940-1.41, respectively. PTAs (>99% and ≥81% for MICs of 2 and 4 mg/L, respectively) matched or exceeded the adult predictions. Simulated Cmax,ss values were below the maximum observed data in other indications, including a high-dose pediatric pneumonia trial, which reported no adverse events related to high exposure.

Infections and diabetes: Risks and mitigation with reference to India

BACKGROUND AND AIMS

The link between diabetes and increased risk of infectious disease has long been recognized, but has re-entered sharp focus following the COVID-19 pandemic.

METHODS

A literature search was conducted in PubMed for articles in English on diabetes and infection.

RESULTS

Diabetes predisposes to infections through alterations in innate and acquired immune defenses. Outcomes of infection are worse in people with uncontrolled diabetes, and infection can worsen hyperglycemia in hitherto well controlled diabetes (bidirectional relationship). Diabetes does not increase the risk of infection with COVID-19 per se, but predisposes to severe disease and poor outcomes. COVID-19 has also been linked to deterioration of glycemic control as well as new-onset diabetes.

CONCLUSIONS

Clinicians caring for people with diabetes should be aware of the increased risk of infections in this population, as well as the possibility of worsening hyperglycemia. A holistic approach with frequent monitoring of blood glucose levels and appropriate titration of medications, along with close attention to nutritional status, is essential to ensure the best possible outcomes.

Characterization of Panton-Valentine leukocidin-positive Staphylococcus aureus from skin and soft tissue infections and wounds in Nigeria: a cross-sectional study

Background:Staphylococcus aureus is a significant pathogen implicated in numerous nosocomial and community-acquired infections. The Panton-Valentine leukocidin (PVL) can be associated with severe necrotizing diseases such as pneumonia, skin and soft tissue infection (SSTI).  Methods: In total, 96 S. aureus isolates were obtained from patients presenting with wounds (n=48) and soft tissue infections (SSTIs, n=48). These were characterized based on their antimicrobial susceptibility profile, the possession of virulence genes (e.g. capsular type, PVL), accessory gene regulator ( agr) type, and the staphylococcal protein A ( spa) type. The production of the PVL protein was assessed by western blotting. Results: All isolates were susceptible to methicillin. The resistance was highest to penicillin (97.9%), followed by trimethoprim/sulfamethoxazole (85.4%) and tetracycline (10.4%). The PVL gene was found in 83.3% of isolates from SSTIs and in 79.2% of isolates from wound. Of these, 53 (68%) produced PVL as assessed by western blotting. The most prevalent spa type was the t084 (78.1%, n=75) and, majority of the isolates carried  agr2 (82.3%, n=79). Conclusions: Prevalence of antibiotic resistant PVL-positive methicillin susceptible S. aureus strains has severe implications on PVL mediated infections.

Pharmacokinetic and Pharmacodynamic Principles of Anti-infective Dosing

PURPOSE

An understanding of the pharmacokinetic (PK) and pharmacodynamic (PD) principles that determine response to antimicrobial therapy can provide the clinician with better-informed dosing regimens. Factors influential on antibiotic disposition and clinical outcome are presented, with a focus on the primary site of infection. Techniques to better understand antibiotic PK and optimize PD are acknowledged.

METHODS

PubMed (inception-April 2016) was reviewed for relevant publications assessing antimicrobial exposures within different anatomic locations and clinical outcomes for various infection sites.

FINDINGS

A limited literature base indicates variable penetration of antibiotics to different target sites of infection, with drug solubility and extent of protein binding providing significant PK influences in addition to the major clearing pathway of the agent. PD indices derived from in vitro studies and animal models determine the optimal magnitude and frequency of dosing regimens for patients. PK/PD modeling and simulation has been shown an efficient means of assessing these PD endpoints against a variety of PK determinants, clarifying the unique effects of infection site and patient characteristics to inform the adequacy of a given antibiotic regimen.

IMPLICATIONS

Appreciation of the PK properties of an antibiotic and its PD measure of efficacy can maximize the utility of these life-saving drugs. Unfortunately, clinical data remain limited for a number of infection site-antibiotic exposure relationships. Modeling and simulation can bridge preclinical and patient data for the prescription of optimal antibiotic dosing regimens, consistent with the tenets of personalized medicine.

The phosphoenolpyruvate phosphotransferase system in group A Streptococcus acts to reduce streptolysin S activity and lesion severity during soft tissue infection

Obtaining essential nutrients, such as carbohydrates, is an important process for bacterial pathogens to successfully colonize host tissues. The phosphoenolpyruvate phosphotransferase system (PTS) is the primary mechanism by which bacteria transport sugars and sense the carbon state of the cell. The group A streptococcus (GAS) is a fastidious microorganism that has adapted to a variety of niches in the human body to elicit a wide array of diseases. A ΔptsI mutant (enzyme I [EI] deficient) generated in three different strains of M1T1 GAS was unable to grow on multiple carbon sources (PTS and non-PTS). Complementation with ptsI expressed under its native promoter in single copy was able to rescue the growth defect of the mutant. In a mouse model of GAS soft tissue infection, all ΔptsI mutants exhibited a significantly larger and more severe ulcerative lesion than mice infected with the wild type. Increased transcript levels of sagA and streptolysin S (SLS) activity during exponential-phase growth was observed. We hypothesized that early onset of SLS activity would correlate with the severity of the lesions induced by the ΔptsI mutant. In fact, infection of mice with a ΔptsI sagB double mutant resulted in a lesion comparable to that of either the wild type or a sagB mutant alone. Therefore, a functional PTS is not required for subcutaneous skin infection in mice; however, it does play a role in coordinating virulence factor expression and disease progression.

Comparative efficacy of tigecycline VERSUS vancomycin in an experimental model of soft tissue infection by methicillin-resistant Staphylococcus aureus producing Panton-Valentine leukocidin

Methicillin-resistant Staphylococcus aureus (MRSA) producing Panton-Valentine leukocidin (PVL) is highly virulent. This study aimed to compare the efficacy of tigecycline versus vancomycin in experimental thigh abscess by a PVL-producing MRSA isolate. One hundred and ninety-six Wistar rats were divided into five groups: group A, controls; groups B and C, administered vancomycin starting 1 and 6 h after bacterial challenge respectively; groups D and E, administered tigecycline starting 1 and 6 h after bacterial challenge respectively. Treatment was continued every 12 hours for three consecutive days. Survival was recorded; separate animals were killed for quantitative cultures. Serum samples were collected for estimation of malondialdehyde (MDA). Survival of group D was prolonged compared to all other groups. The bacterial load of blood, liver, spleen and lung was significantly decreased within group D compared to group B at 36 hours. Treatment with tigecycline was accompanied by significant reduction of serum MDA at 24 hours. Tigecycline is comparable to vancomycin for the treatment of soft tissue infections by PVL-producing MRSA.

[Dynamics of local expression of connexin-43 and basic fibroblast growth factor receptors in patients with skin and soft-tissue infections against the background of diabetes mellitus type II]

Clinical results of wound healing dynamics were studied in 60 patients with soft-tissue infection against the background of diabetes mellitus type II. At the same time the study considered indices of intercellular contacts protein tissue expression such as connexin 43 (Cx43) and basic fibroblast growth factor receptors (bFGFR). The basic therapy of biopsy material of wound borders was applied. The reduction of bFGFR expression and the minor growth of Cx43 expression were observed. The pain syndrome proceeded for a long time and there were signs of perifocal inflammation, retard wound healing with granulation tissue. The application of combined method of ozone therapy which included autohemotherapy with ozone and an external management of wound by ozone-oxygen mixture facilitated to considerable shortening of inflammatory phase and regeneration. It was associated with increased Cx43 expression (in 1.9 times) in comparison with initial level and bFGFR was enlarged in 1.7 times to eighth day of postoperative period.

Population Pharmacokinetic Analysis of Dalbavancin, a Novel Lipoglycopeptide

Dalbavancin is a lipoglycopeptide antibiotic in clinical development as a once-weekly treatment for serious infections. A total of 532 patients, consisting of 502 patients with skin and soft tissue infections requiring parenteral therapy and 30 patients with catheter-related bloodstream infections, was available for population pharmacokinetic analysis. The majority of patients (78.4%) received dalbavancin intravenously as a 1000-mg dose on day 1 and a single 500-mg dose on day 8. A 2-compartment model with first-order elimination provided the best fit to the data. The clearance of dalbavancin was influenced by body surface area and creatinine clearance, but together they described less than 25% of the interpatient variability. Body surface area was determined to be a predictor of the central volume of distribution. There was no evidence that the presence of metabolic substrates, inhibitors, or inducers of cytochrome P450 or selected concomitant medications influenced the clearance of dalbavancin.

Oxygen free radical and antioxidant status in necrotizing soft tissue infection of the lower extremity; a report of two cases with opposite outcomes

Two cases of necrotizing soft tissue infection of the lower extremity were treated concurrently but independently. Multimodal therapy including hip joint disarticulation and hyperbaric oxygen therapy was administered, resulting in opposite outcomes: survival and death. Analysis of the relationships between patient outcome and time-course changes in serum diacron-reactive oxygen metabolites (d-ROMs; an index of oxidative stress), antioxidative potential, and cytokines revealed that serum d-ROMs levels decreased with time, but high serum levels of interleukin-10 (anti-inflammatory cytokine) persisted in the patient who died. These findings may reflect an immunosuppressive status unfavorable to infection prevention. Serum d-ROMs may be a prognostic predictor in necrotizing soft tissue infections.

The role of the Panton-Valentine leucocidin toxin in staphylococcal disease: a systematic review and meta-analysis

BACKGROUND

Invasive community-onset staphylococcal disease has emerged worldwide associated with Panton-Valentine leucocidin (PVL) toxin. Whether PVL is pathogenic or an epidemiological marker is unclear. We investigate the role of PVL in disease, colonisation, and clinical outcome.

METHODS

We searched Medline and Embase for original research reporting the prevalence of PVL genes among Staphylococcus aureus pneumonia, bacteraemia, musculoskeletal infection, skin and soft-tissue infection, or colonisation published before Oct 1, 2011. We calculated odds ratios (ORs) to compare patients with PVL-positive colonisation and each infection relative to the odds of PVL-positive skin and soft-tissue infection. We did meta-analyses to estimate odds of infection or colonisation with a PVL-positive strain with fixed-effects or random-effects models, depending on the results of tests for heterogeneity.

RESULTS

Of 509 articles identified by our search strategy, 76 studies from 31 countries met our inclusion criteria. PVL strains are strongly associated with skin and soft-tissue infections, but are comparatively rare in pneumonia (OR 0·37, 95% CI 0·22-0·63), musculoskeletal infections (0·44, 0·19-0·99), bacteraemias (0·10, 0·06-0·18), and colonising strains (0·07, 0·01-0·31). PVL-positive skin and soft-tissue infections are more likely to be treated surgically than are PVL-negative infections, and children with PVL-positive musculoskeletal disease might have increased morbidity. For other forms of disease we identified no evidence that PVL affects outcome.

INTERPRETATION

PVL genes are consistently associated with skin and soft-tissue infections and are comparatively rare in invasive disease. This finding challenges the view that PVL mainly causes invasive disease with poor prognosis. Population-based studies are needed to define the role of PVL in mild, moderate, and severe disease and to inform control strategies.

FUNDING

None.

Wound fluid lactate concentration: a helpful marker for diagnosing soft-tissue infection in diabetic foot ulcers? Preliminary findings

AIMS

To investigate the impact of wound fluid lactate concentration on diagnosing soft-tissue infection in diabetic foot ulcers.

METHODS

Lactate concentration in wound fluid obtained from diabetic foot ulcers was determined using a lactate analyser and compared with clinical examination findings.

RESULTS

Overall median wound fluid lactate concentration was 21.03 mm (5.58-80.40 mm). Wound lactate levels were significantly higher in infected compared with non-infected diabetic foot ulcers (P=0.001). Non-infected diabetic foot ulcers that healed within 6 months of treatment showed a significantly lower wound fluid lactate concentration at baseline as opposed to those that did not heal (P=0.007).

CONCLUSIONS

Non-healing diabetic foot ulcers are characterized by high wound fluid lactate levels. Assessment of wound fluid lactate concentration might be helpful for confirming the suspicion of soft tissue infection, particularly when clinical signs are atypical.

Analysis of the transcriptome of group A Streptococcus in mouse soft tissue infection

Molecular mechanisms mediating group A Streptococcus (GAS)-host interactions remain poorly understood but are crucial for diagnostic, therapeutic, and vaccine development. An optimized high-density microarray was used to analyze the transcriptome of GAS during experimental mouse soft tissue infection. The transcriptome of a wild-type serotype M1 GAS strain and an isogenic transcriptional regulator knockout mutant (covR) also were compared. Array datasets were verified by quantitative real-time reverse transcriptase-polymerase chain reaction and in situ immunohistochemistry. The results unambiguously demonstrate that coordinated expression of proven and putative GAS virulence factors is directed toward overwhelming innate host defenses leading to severe cellular damage. We also identified adaptive metabolic responses triggered by nutrient signals and hypoxic/acidic conditions in the host, likely facilitating pathogen persistence and proliferation in soft tissues. Key discoveries included that oxidative stress genes, virulence genes, genes related to amino acid and maltodextrin utilization, and several two-component transcriptional regulators were highly expressed in vivo. This study is the first global analysis of the GAS transcriptome during invasive infection. Coupled with parallel analysis of the covR mutant strain, novel insights have been made into the regulation of GAS virulence in vivo, resulting in new avenues for targeted therapeutic and vaccine research.

Influence of diabetes mellitus on deep neck infection

Objective: To investigate the influence of hyperglycaemia on deep neck infection (DNI) and the differences between the diabetic and non-diabetic form of DNI.

Study design and setting: Retrospective review of 131 patients with DNI treated between 1993 and 2002 at Shin Kong Memorial Hospital, Taipei, Taiwan.

Results: Deep neck infection was significantly more prevalent in patients with diabetes mellitus (DM) over 60 years of age than in non-DM subjects of a similar age (p = 0.004). In the DM group, Klebsiella pneumoniae was the most common aerobic pathogen and tended to involve more than two anatomical spaces (p < 0.0001). Seventeen out of 18 patients (94.4 per cent) displayed an elevated (≥7 per cent) glycosylated haemoglobin level. The DM group had a significantly higher complication rate, longer hospital stay and tracheotomy rate than the non-DM group.

Conclusions: Diabetic DNI differs from non-diabetic DNI in several aspects and is associated with a higher morbidity. A greater than normal haemoglobin A1c level was commonly observed.

Penetration of piperacillin and tazobactam into inflamed soft tissue of patients with diabetic foot infection

We investigated the pharmacokinetics of piperacillin and tazobactam in the extracellular space fluid of inflamed soft tissues of six patients with diabetic foot infection using in vivo microdialysis and found similar penetration for piperacillin but not for tazobactam into inflamed and noninflamed soft tissue.

Influence of ceftriaxone treatment on FDG uptake--an in vivo [18F]-fluorodeoxyglucose imaging study in soft tissue infections in rats

Our aim was to determine the influence of antibiotic treatment using ceftriaxone on [18F]-fluorodeoxyglucose (FDG) uptake in experimental soft tissue infections. PET scans were performed in two groups (treated n=4; non-treated n=4) at days 3, 5, and 6 after inoculation of the infection. Additional autoradiography was performed in four animals at day 7 and in three animals at day 11. The difference of FDG uptake on day 5 (after three days of antibiotic treatment) between both groups proved to be significant (df=6; T=2.52; p=0.045). FDG uptake determined at the other days did not reveal significant difference between the two groups. It seems to be possible that the effect of antibiotic treatment on FDG uptake is less evident than reported for therapy monitoring of cancer treatment. The change of FDG uptake over time in treated and untreated infections is complex and further in vivo experiments have to be initiated to investigate the potential value of clinical FDG PET in therapy monitoring of infection.

Antimicrobial peptide 99mTc-ubiquicidin 29-41 as human infection-imaging agent: clinical trial

Ubiquicidin (UBI) 29-41 is a cationic, synthetic antimicrobial peptide fragment that binds preferentially with the anionic microbial cell membrane at the site of infection. The current study was conducted to evaluate its potential as an infection-imaging agent in humans.

METHODS

Eighteen patients, 9 female and 9 male (mean age, 31.7 y; range, 5-75 y), with suspected bone, soft-tissue, or prosthesis infections were included in the study. (99m)Tc-UBI 29-41 in a dose of 400 microg/370-400 MBq was injected intravenously in adults. A dynamic study was followed by spot views of the suspected region of infection (target) and a corresponding normal area (nontarget) at 30, 60, 120, and 240 min. The target-to-nontarget ratios were used to find the optimum time for imaging. Whole-body anterior and posterior images were also acquired at 30, 120, and 240 min to study biodistribution. Activity in each organ was expressed as percentage retained dose. Visual score (0-3) was used to categorize studies as positive or negative, with scores of 0 (minimal or no uptake; equivalent to soft tissue) and 1 (mild; less uptake than in liver) being considered negative and scores of 2 (moderate; uptake greater than or equal to that in liver) and 3 (intense; uptake greater than or equal to that in kidneys) being considered positive. Scans were interpreted as true- or false-positive and true- or false-negative on the basis of bacterial culture as the major criterion and the results of clinical tests, radiography, and 3-phase bone scanning as minor criteria.

RESULTS

The biodistribution study showed a gradual decline in renal activity as percentage of administered dose from 6.53% +/- 0.58% at 30 min to 4.54% +/- 0.57% at 120 min and 3.38% +/- 0.55% at 240 min. The liver showed a similar trend, with values of 5.43% +/- 0.76%, 3.17% +/- 0.25%, and 2.02% +/- 0.30% at 30, 120, and 240 min, respectively. Radioactivity accumulated gradually in the urinary bladder, with values of 4.60% +/- 0.92% at 30 min, 23.00% +/- 2.32% at 120 min, and 38.85% +/- 4.01% at 240 min. Of 18 studies performed with 99mTc-UBI 29-41, 14 showed positive findings and 4 showed negative findings. Negative findings were subsequently confirmed to be true negative. The positive findings for 1 scan were interpreted as false positive, as no growth was obtained on bacterial culture and no evidence of infection was found on minor criteria. In 10 cases, the major criterion was used, whereas in 4 cases minor criteria had to be used for interpretation. Quantitative analysis revealed a maximum mean target-to-nontarget ratio of 2.75 +/- 1.69 at 30 min, which decreased to 2.04 +/- 1.01 at 120 min. The overall sensitivity, specificity, and accuracy were 100%, 80%, and 94.4%, respectively. No adverse reactions were observed during image acquisition and within 5 d after the study.

CONCLUSION

99mTc-UBI 29-41 showed promise in localizing foci of infection, with optimal visualization at 30 min.

Role of tissue oxygen saturation monitoring in diagnosing necrotizing fasciitis of the lower limbs

STUDY OBJECTIVE

We determine the utility of tissue oxygen saturation monitoring in diagnosing necrotizing fasciitis of the lower extremities.

METHODS

We prospectively studied patients who met the criteria of soft tissue infection throughout the lower extremities by tissue oxygen saturation monitoring (with near-infrared spectroscopy) over the middle third of possible involved areas. Cases with evidence of chronic venous stasis, peripheral vascular disease, shock, and systemic hypoxia were excluded. Biceps and contralateral unaffected leg areas were measured as references. The tissue oxygen saturation reading for each area was compared with those finally diagnosed as necrotizing fasciitis and those with only simple soft tissue infection. The tissue oxygen saturation reading was presented as mean+/-SD. Receiver operating characteristic (ROC) curves were used to determine a cutoff value of tissue oxygen saturation reading for early diagnosis of necrotizing fasciitis.

RESULTS

Two hundred thirty-four consecutive patients were enrolled. Nineteen patients (group N) were confirmed to have necrotizing fasciitis, whereas the remaining 215 patients (group C) had only cellulitis. The tissue oxygen saturation reading measured over the biceps muscle was 86%+/-11% in group N and 85%+/-12% in group C. In group N, the leg with necrotizing fasciitis had a tissue oxygen saturation reading of 52%+/-18% throughout the involved site, whereas the tissue oxygen saturation reading measured in the comparative values found in group C was 84%+/-7% (difference 95% confidence interval [CI] 22% to 29%). After fasciotomy, the tissue oxygen saturation reading of the leg with necrotizing fasciitis returned to 82%+/-17% (95% CI 23% to 28% compared with prefasciotomy value) in group N. At the cutoff value of a tissue oxygen saturation reading less than 70% (area under the curve 0.883; 95% CI 0.817 to 0.949) defined by ROC curve, the test revealed a sensitivity of 100% (95% CI 82% to 100%), a specificity of 97% (95% CI 94% to 99%), and an accuracy of 97% (95% CI 95% to 99%).

CONCLUSION

The low tissue oxygen saturation reading values measured by near-infrared spectroscopy throughout the involved areas of the lower extremities are of value in identifying necrotizing fasciitis. This method may offer a reliable noninvasive method of assessing lower extremities at risk for necrotizing fasciitis, at least for a selected patient population.

Tissue pharmacokinetics of levofloxacin in human soft tissue infections

AIMS

The present study addressed the ability of levofloxacin to penetrate into subcutaneous adipose tissues in patients with soft tissue infection.

METHODS

Tissue concentrations of levofloxacin in inflamed and healthy subcutaneous adipose tissue were measured in six patients by microdialysis after administration of a single intravenous dose of 500 mg. Levofloxacin was assayed by high-performance liquid chromatography.

RESULTS

The mean concentration vs time profile of free levofloxacin in plasma was identical to that in inflamed and healthy tissues. The ratios of the mean area under the free levofloxacin concentration vs time curve from 0 to 10 h (AUC(0,10 h)) in tissue to that in plasma were 1.2 +/- 1.0 for inflamed and 1.1 +/- 0.6 for healthy subcutaneous adipose tissue (mean +/- SD). The mean difference in the ratio of the AUC(tissue) : AUC(plasma) for inflamed and healthy tissue was 0.09 (95% confidence interval -0.58, 0.759, P > 0.05). Interindividual variability in tissue penetration was high, as indicated by a coefficient of variation of approximately 82% for AUC(tissue) : AUC(plasma) ratios.

CONCLUSIONS

The penetration of levofloxacin into tissue appears to be unaffected by local inflammation. Our plasma and tissue data suggest that an intravenous dose of 500 mg levofloxacin provides effective antibacterial concentrations at the target site. However, in treatment resistant patients, tissue concentrations may be sub-therapeutic.

The effect of hyperbaric oxygen therapy on the bout of treatment for soft tissue infections

OBJECTIVES

Hyperbaric oxygen (HBO) therapy is often combined with antibiotic therapy for infections such as gas gangrene and osteomyelitis. Although numerous investigations have been undertaken to assess the effect of adjunctive HBO therapy on the treatment of infections, the bout of treatment has not been referred in the previous investigations. The purpose of this retrospective study was to evaluate the efficacy of HBO therapy on the bout of treatment for soft tissue infections.

PATIENTS AND METHODS

In the period between 1994 and 2001, we treated 23 patients with soft tissue infections. Nine patients were treated with antibiotic chemotherapy alone, and 14 patients were treated with a combination of antibiotic chemotherapy and HBO therapy. The mean bout of treatment was compared between these two groups.

RESULTS

The mean bout treated with a combination of antibiotic and HBO was significantly shorter than that with antibiotic alone.

CONCLUSION

Our result indicates that HBO therapy combined with antibiotic therapy is able to shorten the bout of treatment for soft tissue infections. Therefore, we recommend HBO therapy combined with antibiotic therapy for soft tissue infections.

Pharmacodynamics of piperacillin in severely ill patients evaluated by using a PK/PD model

Penetration of antiinfective drugs into soft tissues is essential for antimicrobial killing at the target site, but is substantially lower in severely ill patients compared with healthy subjects. The present study was conducted to assess the antimicrobial effect of piperacillin in severely ill patients. Strains of Staphylococcus aureus and Pseudomonas aeruginosa were exposed in vitro to concentrations of piperacillin, simulating the pharmacokinetic profiles measured in soft tissue of patients and healthy subjects. The simulation for patients resulted in effective killing, whereas bacterial regrowth was detected for healthy subjects. Our in vitro simulation showed that bacterial killing may be effective in severely ill patients despite relatively low concentrations of piperacillin at the target site. This finding is due to impaired renal function and subsequently prolonged tissue and plasma half-lives of piperacillin in intensive care patients.

Penetration of moxifloxacin into healthy and inflamed subcutaneous adipose tissues in humans

The present study addressed the ability of moxifloxacin to penetrate into healthy and inflamed subcutaneous adipose tissues in 12 patients with soft tissue infections (STIs). Penetration of moxifloxacin into the interstitial space fluid of healthy and inflamed subcutaneous adipose tissues was measured by use of in vivo microdialysis following administration of a single intravenous dosage of 400 mg in six diabetic and six nondiabetic patients with STIs. For the entire study population, the mean time-concentration profile of free moxifloxacin in plasma was identical to the time-concentration profile of free moxifloxacin in tissue (P was not significant). For healthy and inflamed adipose tissues for the diabetic subgroup, the mean moxifloxacin areas under the concentration-time curves (AUCs) from 0 to 8 h (AUC(0-8)s) were 8.1 +/- 7.1 and 3.7 +/- 1.9 mg.h/liter, respectively (P was not significant). The ratios of the mean AUC(0-8) for inflamed tissue/AUC(0-8) for free moxifloxacin in plasma were 0.5 +/- 0.4 for diabetic patients and 1.2 +/- 0.8 for nondiabetic patients (P was not significant). The ratios of the AUCs from 0 to 24 h for free moxifloxacin in plasma/MIC at which 90% of isolates are inhibited were >58 and 121 h for Streptococcus species and methicillin-sensitive Staphylococcus aureus, respectively. Concentrations of moxifloxacin effective against clinically relevant bacterial strains are reached in plasma and in inflamed and healthy adipose tissues. Thus, the pharmacokinetics of moxifloxacin in tissue and plasma support its use for the treatment of STIs in diabetic and nondiabetic patients.

Effect of a bacterial pheromone peptide on host chemokine degradation in group A streptococcal necrotising soft-tissue infections

BACKGROUND

Necrotising soft-tissue infections due to group A streptococcus (GAS) are rare (about 0.2 cases per 100000 people). The disease progresses rapidly, causing severe necrosis and hydrolysis of soft tissues. Histopathological analysis of necrotic tissue debrided from two patients (one with necrotising fasciitis and one with myonecrosis) showed large quantities of bacteria but no infiltrating neutrophils. We aimed to investigate whether the poor neutrophil chemotaxis was linked with the ability of group A streptococcus (GAS) to degrade host chemokines.

METHODS

We did RT-PCR, ELISA, and dot-blot assays to establish whether GAS induces synthesis of interleukin 8 mRNA, but subsequently degrades the released chemokine protein. Class-specific protease inhibitors were used to characterise the protease that degraded the chemokine. We used a mouse model of human soft-tissue infections to investigate the pathogenic relevance of GAS chemokine degradation, and to test the therapeutic effect of a GAS pheromone peptide (SilCR) that downregulates activity of chemokine protease.

FINDINGS

The only isolates from the necrotic tissue were two beta-haemolytic GAS strains of an M14 serotype. A trypsin-like protease released by these strains degraded human interleukin 8 and its mouse homologue MIP2. When innoculated subcutaneously in mice, these strains produced a fatal necrotic soft-tissue infection that had reduced neutrophil recruitment to the site of injection. The M14 GAS strains have a missense mutation in the start codon of silCR, which encodes a predicted 17 aminoacid pheromone peptide, SilCR. Growth of the M14 strain in the presence of SilCR abrogated chemokine proteolysis. When SilCR was injected together with the bacteria, abundant neutrophils were recruited to the site of infection, bacteria were cleared without systemic spread, and the mice survived. The therapeutic effect of SilCR was also obtained in mice challenged with M1 and M3 GAS strains, a leading cause of invasive infections.

INTERPRETATION

The unusual reduction in neutrophils in necrotic tissue of people with GAS soft-tissue infections is partly caused by a GAS protease that degrades interleukin 8. In mice, degradation can be controlled by administration of SilCR, which downregulates GAS chemokine protease activity. This downregulation increases neutrophil migration to the site of infection, preventing bacterial spread and development of a fulminant lethal systemic infection.

18F-choline in experimental soft tissue infection assessed with autoradiography and high-resolution PET

For each oncological tracer it is important to know the uptake in non-tumorous lesions. The purpose of this study was to measure the accumulation of fluorine-18 choline (FCH), a promising agent for the evaluation of certain tumour types, in infectious tissue. Unilateral thigh muscle abscesses were induced in five rats by intramuscular injection of 0.1 ml of a bacterial suspension ( Staphylococcus aureus, 1.2 x 10(9) CFU/ml). In all animals, FCH accumulation was measured with high-resolution positron emission tomography (PET) on day 6. Autoradiography of the abscess and ipsilateral healthy muscle was performed on day 7 (three animals) and day 11 (two animals) and correlated with histology. In addition, (18)F-fluorodeoxyglucose (FDG) PET was performed on day 5. Increased FCH uptake was noted in specific layers of the abscess wall which contained an infiltrate of mainly granulocytes on day 7 and mainly macrophages on day 11. The autoradiographic standardised uptake values in the most active part of the abscess wall were 2.99 on day 7 ( n=3) and 4.05 on day 11 ( n=2). In healthy muscle the corresponding values were 0.99 and 0.64. The abscesses were clearly visualised on the FCH and FDG PET images. In conclusion, this study demonstrated avid FCH accumulation in inflammatory tissue, which limits the specificity of FCH for tumour detection. Future studies are now needed to determine the degree of this limitation in human cancer patients.

Depletion of neurohypophyseal content of vasopressin in septic shock

OBJECTIVES

To assess the mechanisms underlying the inappropriately low plasma vasopressin levels reported in septic shock.

DESIGN

Prospective case series.

SETTING

A 26-bed general medical intensive care unit at a university hospital.

PATIENTS

Septic shock patients.

MEASUREMENTS AND MAIN RESULTS

In three consecutive patients with septic shock, plasma vasopressin levels, circulating vasopressinase activity, baroreflex sensitivity, and neurohypophyseal vasopressin content were assessed. Plasma vasopressin concentration was unexpectedly within normal range in two patients (1.6 pg/mL and 1.8 pg/mL) and increased in one (16 pg/mL). In all cases, vasopressinase activity was undetectable, baroreflex sensitivity was decreased, and the high signal intensity of the posterior lobe of the pituitary gland on T1-weighted magnetic resonance images was absent. Magnetic resonance imaging and plasma vasopressin levels normalized after recovery from shock in the patient who survived.

CONCLUSION

These data suggest that in septic shock, inappropriately low plasma levels of vasopressin are at least partly related to a depletion of vasopressin stores in the neurohypophysis.

Inflammation: imaging with methoxy poly(ethylene glycol)-poly-L-lysine-DTPA, a long-circulating graft copolymer

PURPOSE

To test whether a nontargeted, long-circulating, synthetic polymer accumulates in areas of inflammation, with high capillary permeability and increased regional blood flow.

MATERIALS AND METHODS

Methoxy poly(ethylene glycol)-poly-L-lysine (PL)-diethylenetriaminepentaacetic acid (MPEG-PL-DTPA) was labeled with technetium-99m for scintigraphy and with gadolinium for magnetic resonance (MR) imaging. Eleven Escherichia coli-infected rats were injected with 1.0 mCi (37 MBq) of Tc-99m-labeled MPEG-PL-DTPA for scintigraphy. Twelve rats underwent 1.5-T MR imaging after intravenous injection of gadolinium-labeled MPEG-PL-DTPA (35 mumol/kg).

RESULTS

Tc-99m-labeled MPEG-PL-DTPA demonstrated nearly eight-fold higher accumulation in infected muscle when compared with normal muscle. Scintigrams and MR images showed areas of inflammation with peak accumulation at 24 hours after injection of Tc-99m- or gadolinium-labeled MPEG-PL-DTPA.

CONCLUSION

Nontargeted, long-circulating, copolymers can efficiently accumulate in sites of inflammation and thus represent an alternative to inflammation-specific agents.

Pharmacokinetics and tissue penetration of piperacillin/tazobactam with particular reference to its potential in abdominal and soft tissue infections

Piperacillin/tazobactam is a new drug consisting of a highly active penicillin and a beta-lactamase inhibitor. Pharmacokinetic variables of both components after they have been given together have been studied in healthy volunteers and in patients. Drug analysis in all studies was done by specific high pressure liquid chromatography (HPLC). In this review we summarise the pharmacokinetic properties of piperacillin/tazobactam. Most importantly, data on the piperacillin show that its behaviour is not changed when it is given with tazobactam. The pharmacokinetics of tazobactam are typical of beta-lactams, including the tissue penetration. It is distributed mainly into the extra-cellular space. Tissue concentrations of piperacillin/tazobactam and the concentrations of the two agents and their time course in plasma and tissue indicate that this combination is well formulated and truly synergistic pharmacokinetically. Clinical trials will show how these characteristics influence treatment outcomes.