R. Doug Hardy

Management and outcome of children with skin and soft tissue abscesses caused by community-acquired methicillin-resistant Staphylococcus aureus.

Background. Although the epidemiology of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has been explored in many investigations, management of this emerging infection has not been well-studied. For non-methicillin-resistant Staphylococcus aureus skin and soft tissue abscesses, incision and drainage is generally adequate therapy without the use of antibiotics, but this has not been established for CA-MRSA. Methods. Children presenting to Children’s Medical Center of Dallas for management of skin and soft tissue abscesses caused by culture-proved CA-MRSA were prospectively followed. We analyzed data from the initial evaluation and from two follow-up visits that focused on the management and outcome of CA-MRSA infection. Retrospective chart review was performed 2 to 6 months after the initial visit. Results. Sixty-nine children were identified with culture-proved CA-MRSA skin and soft tissue abscess. Treatment consisted of drainage in 96% of patients and wound packing in 65%. All children were treated with antibiotics. Five patients (7%) were prescribed an antibiotic to which their CA-MRSA isolate was susceptible before culture results were known. Four patients (6%) required hospital admission on the first follow-up; none of these patients had received an antibiotic effective against CA-MRSA. A significant predictor of hospitalization was having a lesion initially >5 cm (P = 0.004). Initial ineffective antibiotic therapy was not a significant predictor of hospitalization (P = 1.0). Of the 58 patients initially given an ineffective antibiotic and managed as outpatients, an antibiotic active against CA-MRSA was given to 21 (36%) patients after results of cultures were known. No significant differences in response were observed in those who never received an effective antibiotic than in those who did. Conclusions. Incision and drainage without adjunctive antibiotic therapy was effective management of CA-MRSA skin and soft tissue abscesses with a diameter of <5 cm in immunocompetent children.

Prospective Randomized Trial of Empiric Therapy with Trimethoprim-Sulfamethoxazole or Doxycycline for Outpatient Skin and Soft Tissue Infections in an Area of High Prevalence of Methicillin-Resistant Staphylococcus aureus

ABSTRACT To evaluate empirical therapy with trimethoprim-sulfamethoxazole or doxycycline for outpatient skin and soft tissue infections in an area of high prevalence of methicillin-resistant Staphylococcus aureus, a randomized, prospective, open-label investigation was performed. The overall clinical failure rate was 9%, with all failures occurring in the trimethoprim-sulfamethoxazole group. However, there was no significant difference between the clinical failure rate of empirical trimethoprim-sulfamethoxazole therapy and that of doxycycline therapy.

Pneumonia and Septicemia Caused by Burkholderia thailandensis in the United States

ABSTRACT Burkholderia thailandensis is closely related to Burkholderia pseudomallei, the causative agent of melioidosis. It is generally considered avirulent and previously has been reported to occur only in Southeast Asia. We report the first case of pneumonia and septicemia caused by B. thailandensis in the United States.

Analysis of Pulmonary Inflammation and Function in the Mouse and Baboon after Exposure to Mycoplasma pneumoniae CARDS Toxin

Mycoplasma pneumoniae produces an ADP-ribosylating and vacuolating toxin known as the CARDS (Community Acquired Respiratory Distress Syndrome) toxin that has been shown to be cytotoxic to mammalian cells in tissue and organ culture. In this study we tested the ability of recombinant CARDS (rCARDS) toxin to elicit changes within the pulmonary compartment in both mice and baboons. Animals responded to a respiratory exposure to rCARDS toxin in a dose and activity-dependent manner by increasing the expression of the pro-inflammatory cytokines IL-1α, 1β, 6, 12, 17, TNF-α and IFN-γ. There was also a dose-dependent increase in several growth factors and chemokines following toxin exposure including KC, IL-8, RANTES, and G-CSF. Increased expression of IFN-γ was observed only in the baboon; otherwise, mice and baboons responded to CARDS toxin in a very similar manner. Introduction of rCARDS toxin to the airways of mice or baboons resulted in a cellular inflammatory response characterized by a dose-dependent early vacuolization and cytotoxicity of the bronchiolar epithelium followed by a robust peribronchial and perivascular lymphocytic infiltration. In mice, rCARDS toxin caused airway hyper-reactivity two days after toxin exposure as well as prolonged airway obstruction. The changes in airway function, cytokine expression, and cellular inflammation correlate temporally and are consistent with what has been reported for M. pneumoniae infection. Altogether, these data suggest that the CARDS toxin interacts extensively with the pulmonary compartment and that the CARDS toxin is sufficient to cause prolonged inflammatory responses and airway dysfunction.

Effect of clarithromycin on cytokines and chemokines in children with an acute exacerbation of recurrent wheezing: a double-blind, randomized, placebo-controlled trial

BACKGROUND Clarithromycin is postulated to possess immunomodulatory properties in addition to its antimicrobial activity. OBJECTIVE To evaluate the effect of clarithromycin on serum and nasopharyngeal cytokine and chemokine concentrations in children with an acute exacerbation of recurrent wheezing. METHODS Children with a history of recurrent wheezing or asthma and who presented with an acute exacerbation of wheezing were enrolled in a double-blind, randomized trial of clarithromycin vs placebo. Concentrations of tumor necrosis factor alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta), IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, granulocyte-macrophage colony-stimulating factor, RANTES, eotaxin, macrophage inflammatory protein 1alpha, macrophage inflammatory protein 1beta, and monocyte chemoattractant protein 1 were measured in serum and/or nasopharyngeal aspirates before, during, and after therapy. Mycoplasma pneumoniae and Chlamydophila pneumoniae infection were evaluated for by polymerase chain reaction and serologic testing. RESULTS Nasopharyngeal concentrations of TNF-alpha, IL-1beta, and IL-10 were significantly and persistently lower in children treated with clarithromycin compared with placebo. There tended to be a greater effect of clarithromycin on nasopharyngeal cytokine concentrations in patients with evidence of M. pneumoniae or C. pneumoniae infection. No significant differences were detected in serum cytokines for children treated with clarithromycin compared with placebo. CONCLUSION Clarithromycin therapy reduces mucosal TNF-alpha, IL-1beta, and IL-10 concentrations in children with an acute exacerbation of recurrent wheezing.

Diagnostic Utility and Clinical Significance of Naso- and Oropharyngeal Samples Used in a PCR Assay To Diagnose Mycoplasma pneumoniae Infection in Children with Community-Acquired Pneumonia

ABSTRACT PCR assays of naso- and oropharyngeal samples among hospitalized children appear equally effective for the diagnosis of serologically confirmed community-acquired mycoplasmal pneumonia. However, the combination of results from both sites yields optimal sensitivity (57%), specificity (98%), and positive (92%) and negative (82%) predictive values when compared with Mycoplasma pneumoniae enzyme-linked immunosorbent assay.

It is safe to stop antiretroviral therapy in patients with preantiretroviral CD4 cell counts >250 cells/μL

Objective:To study clinical, immunologic, and virologic outcomes in patients who stop antiretroviral therapy (ART) with relatively preserved CD4 cell counts. Design and Methods:Patients with a documented CD4 cell count >250 cells/μL who stopped ART for any reason for at least 5 weeks were studied. Relevant clinical and laboratory data were collected using a standardized data collection form. Main Outcome Measures:Patients were monitored for outcomes including Centers for Disease Control (CDC) category B or C events, time to restarting ART, and time to reaching a CD4 cell count of ≤250 cells/μL. Results:A total of 107 patients were included. The median time on ART was 45 months and median number of antiretroviral medications was 4. The median pre-ART CD4 cell count and HIV viral load were 463 cells/μL and 4.35 log copies/mL, respectively. The median CD4 cell at time of ART stop was 739 cell/μL. The slope of the CD4 decrease was 65 cells/mo in the first 2 months, which was greater than the subsequent decline of 8 cells/mo thereafter (P < 0.01). Similarly the median viral load increase was 2.54 log copies/mL in the first 2 months after stopping and was unchanged after that point. Two patients experienced the retroviral rebound syndrome after ART cessation but no CDC category B or C events were observed during 10 months of follow-up. The median time from stopping ART to reaching the combined endpoint of CD4 <250 or restarting ART was 8.9 months. In multivariate analysis, pre-ART CD4 cell count >250 was protective of reaching the combined endpoint (odds ratio = 0.156, P = 0.03). Other predictors of reaching the combined endpoint in multivariate analysis were older age and number of prior ART agents. Patients who restarted ART had a favorable virologic and immunologic response. Conclusions:Patients with relatively high CD4 cell counts prior to starting ART did well after stopping ART. Pre-ART CD4 cell count can be used to predict outcomes after ART cessation.

Variation in colonization, ADP-ribosylating and vacuolating cytotoxin, and pulmonary disease severity among mycoplasma pneumoniae strains.

RATIONALE Mycoplasma pneumoniae was recently discovered to produce an ADP-ribosylating and vacuolating cytotoxin, designated CARDS toxin, which is hypothesized to be a primary pathogenic mechanism responsible for M. pneumoniae-induced pulmonary inflammation. It is unknown if cytotoxin production varies with M. pneumoniae strain or if variation in cytotoxin production affects pulmonary disease severity. OBJECTIVES To examine the production of CARDS toxin by various strains of M. pneumoniae and compare the disease manifestations elicited by these strains in an experimental model of M. pneumoniae respiratory infection. METHODS BALB/c mice were inoculated once intranasally with SP4 broth (negative control) or three different M. pneumoniae strains: M129-B7, M129-B9, or S1. Mice were assessed at 1, 2, 4, 7, 10, and 14 days after inoculation. Outcome variables included comparisons among M. pneumoniae strains relative to bronchoalveolar lavage (BAL) M. pneumoniae quantitative culture, CARDS toxin-based PCR, and CARDS toxin protein determinations, as well as cytokine and chemokine concentrations. Graded lung histopathologic score (HPS) was also assessed. MEASUREMENTS AND MAIN RESULTS CARDS toxin concentrations were significantly increased in mice inoculated with strain S1 compared with mice inoculated with M129-B7 or M129-B9 strains. Quantitative M. pneumoniae culture and polymerase chain reaction were also significantly greater in mice infected with S1 strain compared with the other two strains, as were lung HPS and concentrations of IFN-γ, IL-12, IL-1α, macrophage inflammatory protein-1α, and keratinocyte-derived chemokine. In addition, a significant positive correlation was found between CARDS toxin concentration and lung HPS. CONCLUSIONS CARDS toxin concentrations in BAL are directly linked to the ability of specific M. pneumoniae strains to colonize, replicate, and persist, and elicit lung histopathology. This variation among strains may predict the range in severity of pulmonary disease observed among patients.

Synthesis and Distribution of CARDS Toxin During Mycoplasma pneumoniae Infection in a Murine Model

Mice were infected with Mycoplasma pneumoniae and monitored for the synthesis and distribution of the unique adenosine diphosphate-ribosylating and vacuolating Community Acquired Respiratory Distress Syndrome (CARDS) toxin in bronchiolar lavage fluid (BALF) and lung. We noted direct relationships between the concentration of CARDS toxin and numbers of mycoplasma genomes in BALF and the degree of histologic pulmonary inflammation. Immunostaining of lungs revealed extensive colonization by mycoplasmas, including the detection of CARDS toxin in the corresponding inflamed airways. Lung lesion scores were higher during the early stages of infection, decreased gradually by day 14 postinfection, and reached substantially lower values at day 35. Infected mouse immunoglobulin (Ig) M and IgG titers were positive for CARDS toxin as well as for the major adhesin P1 of M. pneumoniae. These data reinforce the proposed pathogenic role of CARDS toxin in M. pneumoniae-mediated pathologies.

Evaluation of LBM415 (NVP PDF-713), a Novel Peptide Deformylase Inhibitor, for Treatment of Experimental Mycoplasma pneumoniae Pneumonia

ABSTRACT Mycoplasma pneumoniae is a major cause of community-acquired pneumonia. We evaluated the efficacy of LBM415, a novel peptide deformylase inhibitor antimicrobial agent, for the treatment of M. pneumoniae pneumonia in a mouse model. Eight-week-old BALB/c mice were intranasally inoculated once with 107 CFU of M. pneumoniae. Groups of mice were treated with LBM415 (50 mg/kg of body weight) or placebo subcutaneously daily for 13 days, starting 24 h after inoculation. Groups of mice were evaluated at the baseline; at days of treatment 1, 3, 6, and 13; and at 7 days after treatment. The MIC of LBM415 against M. pneumoniae was <0.005 μg/ml. LBM415-treated mice had significantly lower bronchoalveolar lavage fluid M. pneumoniae concentrations than placebo-treated mice on days 6 and 13 of treatment. Compared with placebo treatment, therapy with LBM415 significantly decreased lung histopathology scores at days 3, 6, and 13 of treatment and at 7 days after treatment. Airway obstruction was significantly lower in LBM415-treated mice than in placebo-treated mice on days 1, 3, and 6 of treatment and after 7 days of therapy, while airway hyperresponsiveness was significantly lower only on day 3 of therapy. The bronchoalveolar lavage fluid concentrations of tumor necrosis factor alpha, gamma interferon (IFN-γ), interleukin-6 (IL-6), IL-12, KC (functional IL-8), monocyte chemotactic protein 1, macrophage inflammatory protein 1α, monokine induced by IFN-γ, and IFN-inducible protein 10 were significantly reduced in LBM415-treated mice compared with the levels in placebo-treated mice. There were no differences in the bronchoalveolar lavage fluid concentrations of granulocyte-macrophage colony-stimulating factor, IL-1β, IL-2, IL-4, IL-5, and IL-10 between the two groups of mice. LBM415 therapy had beneficial microbiologic, histologic, respiratory, and immunologic effects on acute murine M. pneumoniae pneumonia.