Tigecycline therapy significantly reduces the concentrations of inflammatory pulmonary cytokines and chemokines in a murine model of Mycoplasma pneumoniae pneumonia.

Mycoplasma pneumoniae is one of the causative agents of atypical community-acquired pneumonia. Tigecycline belongs to a new class of glycylcycline antimicrobials that have activity against a wide range of microorganisms, including in vitro activity against M. pneumoniae. We investigated the effect of tigecycline on microbiologic, histologic, and immunologic indices in a murine model of M. pneumoniae pneumonia. BALB/c mice were inoculated intranasally with M. pneumoniae and treated subcutaneously with tigecycline or placebo for 6 days. Outcome variables included quantitative bronchoalveolar lavage (BAL) M. pneumoniae culture, lung histopathologic score (HPS), BAL cytokine and chemokine concentrations (tumor necrosis factor alpha [TNF-alpha], gamma interferon [IFN-gamma], interleukin 1beta [IL-1beta], IL-2, IL-4, IL-5, IL-6, IL-10, IL-12 [p40/p70], granulocyte-macrophage colony-stimulating factor, MIP-1alpha, MIG, KC, MCP-1, and IP-10). BAL M. pneumoniae concentrations in mice treated with tigecycline (MpTige) tended to be reduced compared with mice treated with placebo (MpPl); however this did not reach statistical significance. The lung HPS was significantly lower, as well as the parenchymal-pneumonia subscore, in the MpTige mice than in the MpPl mice. MpTige mice had significantly lower BAL cytokine concentrations of IL-1beta, IL-12 (p40/p70), IFN-gamma, and TNF-alpha; of the chemokines, MIG, MIP-1alpha, and IP-10 were statistically lower in MpTige mice. While tigecycline treatment demonstrated a modest microbiologic effect, it significantly improved lung histologic inflammation and reduced pulmonary cytokines and chemokines.

Respiratory tract infection with Mycoplasma pneumoniae in interleukin-12 knockout mice results in improved bacterial clearance and reduced pulmonary inflammation.

Mycoplasma pneumoniae is a leading cause of pneumonia and is associated with asthma. Evidence links M. pneumoniae respiratory disease severity with interleukin-12 (IL-12) concentration in respiratory secretions. We evaluated the microbiologic, inflammatory, and pulmonary function indices of M. pneumoniae pneumonia in IL-12 (p35) knockout (KO) mice and wild-type (WT) mice to determine the role of IL-12 in M. pneumoniae respiratory disease. Eight-week-old wild-type BALB/c mice and 8-week-old IL-12 (p35) KO BALB/c mice were inoculated once intranasally with 10(7) CFU of M. pneumoniae. Mice were evaluated at days 2, 4, and 7 after inoculation. Outcome variables included quantitative bronchoalveolar lavage (BAL) M. pneumoniae culture, lung histopathologic scores (HPS), BAL cytokine concentrations determined by enzyme-linked immunosorbent assay (tumor necrosis factor alpha [TNF-alpha], gamma interferon [IFN-gamma], IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-10, and granulocyte-macrophage colony-stimulating factor) and plethysmography, before and after methacholine, to assess airway obstruction (AO) and airway hyperreactivity (AHR). IL-12 (p35) KO mice infected with M. pneumoniae were found to have significantly lower BAL M. pneumoniae concentrations compared with M. pneumoniae-infected WT mice. Lung HPS and the parenchymal pneumonia subscores (neutrophilic alveolar infiltrate), as well as AO, were significantly lower in infected KO mice. No difference was found for AHR. Infected KO mice had significantly lower BAL concentrations of IFN-gamma than WT mice; a trend toward lower BAL concentrations was observed for IL-10 (P = 0.065) and TNF-alpha (P = 0.078). No differences were found for IL-1beta, IL-2, IL-4, IL-5, or IL-6. The lack of IL-12 in experimental M. pneumoniae pneumonia was associated with less severe pulmonary disease and more rapid microbiologic and histologic resolution.

Factors influencing the anti-inflammatory effect of dexamethasone therapy in experimental pneumococcal meningitis.

Dexamethasone (DXM) interferes with the production of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) and can thereby diminish the secondary inflammatory response that follows initiation of antibacterial therapy. A beneficial effect on the outcome of Haemophilus meningitis in children has been proven, but until recently the effect of DXM therapy in pneumococcal meningitis was uncertain. The aim of the present study was to evaluate factors that might influence the modulatory effect of DXM on the antibiotic-induced inflammatory response in a rabbit model of pneumococcal meningitis. DXM (1 mg/kg) was given intravenously 30 min before or 1 h after administration of a pneumococcal cell wall extract, or the first dose of ampicillin. In meningitis induced by cell wall extract, DXM therapy prevented the increase in cerebrospinal fluid (CSF) leucocyte and lactate concentrations, but only if given 30 min before the cell wall extract. In meningitis caused by live organisms, initiation of ampicillin therapy resulted in an increase in CSF TNF-alpha and lactate concentrations only in animals with initial CSF bacterial concentrations > or =5.6 log10 cfu/mL. In those animals, DXM therapy prevented significant elevations in CSF TNF-alpha [median change -184 pg/mL, -114 pg/mL versus +683 pg/mL with DXM (30 min before or 1 h after ampicillin) versus controls (no DXM), respectively, P=0.02] and lactate concentrations [median change -10.6 mmol/L, -1.5 mmol/L versus +14.3 mmol/L with DXM (30 min before or 1 h after ampicillin) versus controls (no DXM), respectively, P=0.01]. These effects were independent of the timing of DXM administration. In this model of experimental pneumococcal meningitis, an antibiotic-induced secondary inflammatory response in the CSF was demonstrated only in animals with high initial CSF bacterial concentrations (> or =5.6 log10 cfu/mL). These effects were modulated by DXM therapy whether it was given 30 min before or 1 h after the first dose of ampicillin.

Pharmacodynamics and bactericidal activity of moxifloxacin in experimental Escherichia coli meningitis.

Moxifloxacin, an 8-methoxyquinolone with broad-spectrum activity in vitro, was studied in the rabbit model of Escherichia coli meningitis. The purposes of this study were to evaluate the bactericidal effectiveness and the pharmacodynamic profile of moxifloxacin in cerebrospinal fluid (CSF) and to compare the bactericidal activity with that of ceftriaxone and meropenem therapy. After induction of meningitis, animals were given single doses of 10, 20, and 40 mg/kg or divided-dose regimens of 5, 10, and 20 mg/kg twice, separated by 6 h. After single doses, the penetration of moxifloxacin into purulent CSF, measured as percentage of the area under the concentration-time curve (AUC) in CSF relative to the AUC in plasma, was approximately 50%. After single doses of 10, 20, and 40 mg/kg, the maximum CSF concentration (C(max)) values were 1.8, 4.2, and 4.9 microg/ml, respectively; the AUC values (total drug) were 13.4, 25.4, and 27.1 microg/ml x h, respectively, and the half-life values (t(1/2)) were 6.7, 6.6, and 4.7 h, respectively. The bacterial killing in CSF for moxifloxacin, calculated as the Deltalog(10) CFU per milliliter per hour, at 3, 6, and 12 h after single doses of 10, 20, and 40 mg/kg were -5.70, -6.62, and -7.02; -7.37, -7.37, and -6.87; and -6.62, -6.62, and -6.62, respectively, whereas those of ceftriaxone and meropenem were -4.18, -5.24, and -4.43, and -3.64, -3.59, and -4.12, respectively. The CSF pharmacodynamic indices of AUC/MBC and C(max)/MBC were interrelated (r = 0.81); there was less correlation with T > MBC (r = 0.74). In this model, therapy with moxifloxacin appears to be at least as effective as ceftriaxone and more effective than meropenem therapy in eradicating E. coli from CSF.

BMS-284756 in experimental cephalosporin-resistant pneumococcal meningitis.

BMS-284756 is a novel des-fluoro(6) quinolone with a broad antimicrobial activity, including Streptococcus pneumoniae. The purpose of this study was to evaluate the pharmacodynamic profile and effectiveness of BMS-284756 for therapy of experimental meningitis caused by penicillin- and cephalosporin-resistant S. pneumoniae (CRSP). Meningitis was induced in rabbits by intracisternal inoculation of CRSP. BMS-284756 was given intravenously 16 h after intracisternal inoculation in single doses of 2.5 (n = 5 animals), 5 (n = 6), 10 (n = 6), 20 (n = 8), and 30 mg/kg (n = 6), in two doses of 10 mg/kg each separated by 5 h (n = 4), and as a 20-mg/kg dose followed 5 h later by 10 mg/kg (n = 5). The MICs and MBCs of BMS-284756, ceftriaxone, and vancomycin were 0.06 and 0.06, 4 and 4, and 0.25 and 0.25 microg/ml, respectively. After single doses of 10, 20, and 30 mg/kg, the maximum concentrations in cerebrospinal fluid (CSF) (mean +/- standard deviation) were 0.32 +/- 0.12, 0.81 +/- 0.38, and 1.08 +/- 0.43 microg/ml, respectively; the elimination half-life in CSF was 4.5 to 6.3 h. The CSF bacterial killing rates (BKR) at 5 h of the single-dose regimens of 10, 20 and 30 mg/kg were -0.84 +/- 0.48, -1.09 +/- 0.32, and -1.35 +/- 0.05 Deltalog(10) CFU/ml/h. The BKR(0-5) of the divided regimens (10 mg/kg twice and 20 mg/kg followed by 10 mg/kg) was -0.82 +/- 0.52 and -1.24 +/- 0.34 Deltalog(10) CFU/ml/h, respectively. The BKR(0-5) of the combined therapy with vancomycin and ceftriaxone was -1.09 +/- 0.39 Deltalog(10) CFU/ml/h. The penetration of BMS-284756 into purulent CSF relative to plasma was 14 to 25%. The bactericidal effect of BMS-284756 in CSF was concentration dependent. BMS-284756 at 30 mg/kg as a single or divided dose was as effective as standard therapy with vancomycin and ceftriaxone.

Clinical practice guidelines for the diagnosis and treatment of respiratory tract infections.

Clinical practice guidelines can be indispensable tools for managed care organizations (MCOs) in providing cost-effective treatment of common conditions. Guidelines for acute respiratory tract infections, such as acute otitis media (AOM) and acute sinusitis, can assist clinicians in accurately diagnosing these conditions, in providing treatment rationales, and in reducing the costs associated with inappropriate antibiotic prescriptions. Barriers to the implementation of practice guidelines include negative attitudes clinicians may have about guidelines promoted by MCOs; patient/parent expectations for antibiotic treatment; lack of financial resources, information system resources, and support for implementation; and lack of commitment to patient and provider education on the part of MCOs. MCOs can facilitate the adoption and implementation of guidelines with a systematic approach that involves establishing a guideline review process, gaining the support of providers, selecting outcomes measures, collecting and analyzing outcomes data, and providing feedback to clinicians about the impact of changes in their practices. This systematic approach should be used as part of the process for the National Committee for Quality Assurance accreditation. Evidence-based clinical practice guidelines for AOM and sinusitis have been developed recently by national consortia of infectious disease experts. Adoption of these guidelines can assist in preventing the spread of resistant pathogens.

Elevated cytokine and chemokine levels and prolonged pulmonary airflow resistance in a murine Mycoplasma pneumoniae pneumonia model: a microbiologic, histologic, immunologic, and respiratory plethysmographic profile.

Because Mycoplasma pneumoniae is hypothesized to play an important role in reactive airway disease/asthma, a comprehensive murine model of M. pneumoniae lower respiratory infection was established. BALB/c mice were intranasally inoculated once with M. pneumoniae and sacrificed at 0 to 42 days postinoculation. All mice became infected and developed histologic evidence of acute pulmonary inflammation, which cleared by 28 days postinoculation. By contrast, M. pneumoniae persisted in the respiratory tract for the entire 42 days studied. Tumor necrosis factor alpha, gamma interferon, interleukin-6 (IL-6), KC (functional IL-8), MIP-1alpha, and MCP-1/JE concentrations were significantly elevated in bronchoalveolar lavage samples, whereas IL-4 and IL-10 concentrations were not significantly elevated. Pulmonary airflow resistance, as measured by plethysmography, was detected 1 day postinoculation and persisted even after pulmonary inflammation had resolved at day 28. Serum anti-M. pneumoniae immunoglobulin G titers were positive in all mice by 35 days. This mouse model provides a means to investigate the immunopathogenesis of M. pneumoniae infection and its possible role in reactive airway disease/asthma.

Acute mastoiditis in children: a seventeen-year experience in Dallas, Texas.

BACKGROUND: In the preantibiotic era acute mastoiditis was the most common complication of acute otitis media, often resulting in substantial morbidity and mortality. Since 1989 several investigators have documented an increased frequency of acute mastoiditis in children. METHODS: The medical records of all children with a discharge diagnosis of acute mastoiditis, managed at Children's Medical Center, Dallas, TX, from 1983 through 1999 were reviewed. RESULTS: There were 57 cases of acute mastoiditis during the 17-year period of 1983 through 1999 compared with 57 cases in a 25-year period of 1955 through 1979 reported previously at the same institution. The number of cases of acute mastoiditis per 10,000 hospital admissions increased significantly (regression analysis P = 0.003) during the more recent 17 years. From 1993 through 1999 there were 4.5 cases or more per 10,000 admissions each year, whereas from 1983 through 1992, the incidence never exceeded 4.3 cases per 10,000 admissions (P = 0.018). The median age of the patients was 48 months. Twenty-two patients (38.5%) were younger than 24 months; 17 of these were 12 months of age or younger. Twenty-two (38.5%) patients had no history of previous episodes of acute otitis media. Streptococcus pneumoniae was the pathogen most often isolated from the cultures. Complications of mastoiditis occurred in 20 children (35%). CONCLUSIONS: We conclude that acute mastoiditis continues to be a problem in the post antibiotic era. It occurs mainly in young children and can be the first evidence of ear disease.

Comparative study of cefepime versus ceftazidime in the empiric treatment of pediatric cancer patients with fever and neutropenia.

BACKGROUND: In view of the recent trend toward monotherapy in the treatment of bacterial infection, we evaluate the clinical efficacy and safety of cefepime vs. ceftazidime for the empiric treatment of febrile episodes in neutropenic pediatric cancer patients. METHODS: In a single site, open label study, 104 neutropenic pediatric cancer patients [96% with absolute neutrophil count (ANC) of <500 neutrophils/mm3] with a median age of 6 years were randomized (1:1) to receive either intravenous cefepime or ceftazidime (50 mg/kg/dose every 8 h; < or = 6 g/day) for empiric treatment of fever (temperature >38.0 degrees C occurring at least twice in 24 h, or single >38.5 degrees C). Febrile episodes were classified as either microbiologically or clinically documented infection or fever of unknown origin. Therapy continued until the ANC was > or = 1,000 neutrophils/mm3 or there was an increasing ANC in low risk patients (maximum duration of treatment, 8 weeks). The primary efficacy endpoints assessed were clinical and microbiologic response to assigned drug therapy. Secondary outcome measures were rate of early discontinuation of study drug and use of concomitant antibiotic therapy to modify initial study drug regimen. RESULTS: Of 68 patients who could be evaluated for efficacy, 74% (26 of 35) of cefepime-treated patients and 70% (23 of 33) of ceftazidime-treated patients responded to treatment. The small number of study patients precluded statistical analysis of results. In a modified intent-to-treat analysis, 59% of the patients treated with cefepime and 47% of ceftazidime-treated patients responded to therapy. Cefepime patients developed fewer new infections than ceftazidime patients (9% vs. 21%, respectively) and early discontinuation of study drug therapy occurred slightly more often in the ceftazidime group. Further, the use of concomitant systemic antimicrobial therapy (mostly vancomycin) occurred less often in the cefepime-treated patients, as compared with the ceftazidime group [35% [17 of 49] vs. 44% (24 of 55), respectively]. No deaths or serious adverse events were considered to be related to study therapy. The most frequent adverse event was rash that was moderate in severity, and it occurred equally in both groups. CONCLUSION: Cefepime appears to be safe and effective compared with ceftazidime for initial empiric therapy of febrile episodes in neutropenic pediatric cancer patients.

Effects of amoxicillin/clavulanate or azithromycin on nasopharyngeal carriage of Streptococcus pneumoniae and Haemophilus influenzae in children with acute otitis media.

The effect of antibiotic therapy on nasopharyngeal colonization by Streptococcus pneumoniae and Haemophilus influenzae was evaluated in children diagnosed with acute otitis media. Children were randomly assigned to receive either amoxicillin/clavulanate or azithromycin therapy, and nasopharyngeal swabs were obtained for culture before and after starting therapy. Amoxicillin/clavulanate therapy eradicated or suppressed all strains of S. pneumoniae susceptible to penicillin, 75% of strains with intermediate resistance, and 40% of strains resistant to penicillin. Azithromycin therapy cleared two-thirds of azithromycin-susceptible strains of S. pneumoniae but none of azithromycin-nonsusceptible strains. Selection for antibiotic-resistant strains in individual children was not observed in children who received amoxicillin/clavulanate therapy but was observed in 2 children who received azithromycin therapy. Carriage of H. influenzae was also reduced by antimicrobial therapy but more so by amoxicillin/clavulanate. Antibiotic therapy does not directly increase the number of resistant strains in the population but, by eradicating susceptible strains, allows greater opportunity for carriage and spread of resistant strains.

Pharmacodynamics of gatifloxacin in experimental models of pneumococcal meningitis.

The alarming increase of bacterial resistance has had a serious impact on treatment practices for patients with meningitis and has prompted investigation of other possibly effective antibiotic regimens with agents, such as gatifloxacin and trovafloxacin, that have excellent activity against Streptococcus pneumoniae. The use of fluoroquinolones in children has been limited by studies that report chondrotoxicity in young animals. Gatifloxacin, a new fluoroquinolone, was recently tested in a rabbit model of cephalosporin-resistant pneumococcal meningitis. In these studies, animals were infected with a ceftriaxone-resistant (minimal inhibitory concentration [MIC], 4 microg/mL; minimal bactericidal concentration [MBC], 4 microg/mL) and gatifloxacin-susceptible (MIC, 0.125 microg/mL; MBC, 0.25 microg/mL) strain of S. pneumoniae and were treated with either a single- or divided-dose regimen of gatifloxacin. Results from these studies are reviewed and compared with data from other studies that used a similar rabbit model of pneumococcal meningitis. Overall, it was found that the bacteriologic efficacy of gatifloxacin against S. pneumoniae was as effective as that of conventional regimens. Bactericidal activity of gatifloxacin was correlated with the area under the time-concentration curve-to-MBC ratio; maximal activity was achieved when gatifloxacin concentrations exceeded the MBC for the entire dosing interval.

Diagnosis and management of pneumonia in children.

BACKGROUND: This paper describes challenges in etiologic diagnosis and treatment of childhood community-acquired pneumonia and the means of addressing some of them. MICROBIOLOGICAL DIAGNOSIS: From about one-third to two-thirds of cases of pneumonia can be attributed to a specific etiology depending on which culture, antigen detection and specialized serologic techniques, some of which are unavailable to clinicians, are used. Results of studies in which microbiologic causes have been sought confirm the importance of Streptococcus pneumoniae as the primary bacterial cause of pneumonia in infants and children. Viral etiologies become less prevalent and mycoplasmal and chlamydial infections become more prevalent with increasing age. EMPIRIC TREATMENT: Because definitive information about causative pathogens is seldom available, treatment of pneumonia is most often empiric. Antibiotic therapy can be withheld in mildly ill, ambulatory patients in whom viral infection is likely. Most guidelines suggest initial treatment with orally administered amoxicillin or amoxicillin/clavulanate or with intravenous cefuroxime when patients require hospitalization. In May, 2000, the Centers for Disease Control-convened Drug-Resistant S. pneumoniae Therapeutic Working Group identified oral beta-lactams including cefuroxime axetil, amoxicillin and amoxicillin/clavulanate as appropriate options for first line therapy of community-acquired pneumonia in ambulatory adults and children. CONCLUSIONS: New diagnostic techniques such as pneumococcal serologies and polymerase chain reaction testing have improved the ability to determine the microbiologic etiology of childhood pneumonia. Because these tests are not generally available, empiric treatment is necessary. Efforts to identify new intervention strategies, diagnostic tools, therapies and vaccines will be helpful in managing this disease.

Etiology and treatment of pneumonia.

BACKGROUND: Lower respiratory tract infections are a common cause of morbidity among children. Among these infections pneumonia is the most serious illness and can be difficult to diagnose. The etiology of pneumonia is still partly unknown, primarily because of difficulty in obtaining adequate samples and lack of reliable diagnostic methods. ETIOLOGY OF PNEUMONIA: Streptococcus pneumoniae is recognized as an important cause of pediatric pneumonia regardless of age in both the inpatient and outpatient setting. In developed countries S. pneumoniae probably accounts for 25 to 30% of cases of pediatric community-acquired pneumonia. Viruses (mostly respiratory syncytial virus) are responsible for approximately 20% of cases, and Chlamydia pneumoniae and Mycoplasma pneumoniae occur commonly in older children. FUTURE CHALLENGES: Despite the effectiveness of antimicrobial therapy, the emergence of resistant bacterial pathogens has resulted in increased interest in developing more effective vaccines. If conjugate pneumococcal vaccines prove effective at eradicating carriage of pneumococci in the nasopharynx, immunization may be an important tool against the spread of pneumococcal disease. Future challenges include implementation of effective intervention strategies, production of simple diagnostic tools and development of effective vaccines.

The UspA1 protein and a second type of UspA2 protein mediate adherence of Moraxella catarrhalis to human epithelial cells in vitro.

The UspA1 and UspA2 proteins of Moraxella catarrhalis are structurally related, are exposed on the bacterial cell surface, and migrate as very high-molecular-weight complexes in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Previous analysis of uspA1 and uspA2 mutants of M. catarrhalis strain 035E indicated that UspA1 was involved in adherence of this organism to Chang conjunctival epithelial cells in vitro and that expression of UspA2 was essential for resistance of this strain to killing by normal human serum (C. Aebi, E. R. Lafontaine, L. D. Cope, J. L. Latimer, S. R. Lumbley, G. H. McCracken, Jr., and E. J. Hansen, Infect. Immun. 66:3113-3119, 1998). In the present study, isogenic uspA1, uspA2, and uspA1 uspA2 mutations were constructed in three additional M. catarrhalis strains: 012E, TTA37, and 046E. The uspA1 mutant of strain 012E had a decreased ability to attach to Chang cells. However, inactivation of the uspA1 gene in both strain TTA37 and strain 046E did not cause a significant decrease in attachment ability. Inactivation of the uspA2 gene of strain TTA37 did result in a loss of attachment ability. Nucleotide sequence analysis revealed that the predicted protein encoded by the uspA2 genes of both strains TTA37 and 046E had a N-terminal half that resembled the N-terminal half of UspA1 proteins, whereas the C-terminal half of this protein was nearly identical to those of previously characterized UspA2 proteins. The gene encoding this "hybrid" protein was designated uspA2H. PCR-based analysis revealed that approximately 20% of M. catarrhalis strains apparently possess a uspA2H gene instead of a uspA2 gene. The M. catarrhalis uspA1, uspA2, and uspA2H genes were cloned and expressed in Haemophilus influenzae cells, which were used to prove that both the UspA1 and UspA2H proteins can function as adhesins in vitro.

Buffy coat PCR for diagnosis of experimental pneumococcal pneumonia.

An immunocompetent murine model of pneumococcal pneumonia and bacteremia was used to evaluate a PCR assay based on amplification of the pneumolysin gene. Mice were treated with trovafloxacin to determine the decline in sensitivity of PCR as lung bacterial concentrations decreased and blood cultures became sterile. Forty-three mice were studied for up to 120 h after start of antibiotic treatment. PCR of buffy coat specimens was more sensitive than PCR of plasma. Only 21% of animals had a positive blood culture, whereas 77% of PCR buffy coat assays were positive. After 48 h of therapy all blood culture specimens were sterile, whereas buffy coat PCR was positive in 57.8% of specimens. PCR of buffy coat specimens was negative in all mice colonized nasally with Streptococcus pneumoniae and in rabbits with Escherichia coli bacteremia. Our results demonstrate that our PCR technique using buffy coat specimens is highly specific for invasive pneumococcal disease and remains positive in the majority of animals for at least 48 h after start of antibiotic therapy.