This study used an expanded diagnostic armamentarium to define the broad spectrum of pathogens that cause pneumonia in hospitalized children. The data confirm the importance of S pneumoniae and the frequent occurrence of bacterial and viral coinfections in children with pneumonia. These findings will facilitate age-appropriate antibiotic selection and future evaluation of the clinical effectiveness of the pneumococcal conjugate vaccine as well as other candidate vaccines.

The results of this study, in which dexamethasone administration began before the initiation of cefotaxime therapy, provide additional evidence of a beneficial effect of dexamethasone therapy in infants and children with bacterial meningitis.

SummaryAlthough previous studies using human cytokines in rabbits and rats have provided evidence ofthe participation oftumor necrosis factor a (TNF-(x) and interleukin lß (IL1ß) in the meningeal inflammatory cascade, the results obtained by several groups ofinvestigators have been discordant or, at times, contradictory. In the present study, homologous cytokines were applied to the rabbit meningitis model. Intracisternal administration of 102-10 1 IU of purified rabbit TNF-a (RaTNF-a) produced significant cerebrospinal fluid (CSF) inflammation. A similar response was observed after intracisternal inoculation of 5-200 ng of rabbit recombinant ILlß (rrIL1ß) . Preincubation of these two mediators with their specific antibodies resulted in an almost complete suppression of the CSF inflammatory response. In animals with Haemophilus influenzae type b lipooligosaccharide-induced meningitis, intracisternal administration of anti-rrlIrlß, anti-RaTNF-a, or both resulted in a significant modulation of meningeal inflammation. Simultaneous administration of 103 IU of RaTNF-a and 5 ng of rrILlß resulted in a synergistic inflammatory response manifested by a more rapid and significantly increased influx of white blood cells into the CSF compared with results after each cytokine given alone. These data provide evidence for a seminal role of TNF-a and IL1ß in the initial events of meningeal inflammation.

The most appropriate therapy for meningitis caused by Streptococcus pneumoniae strains resistant to the extended-spectrum cephalosporins is unknown. We evaluated ceftriaxone, vancomycin, and rifampin alone and in different combinations and meropenem, cefpirome, and clinafloxacin alone in the rabbit meningitis model. Meningitis was induced in rabbits by intracisternal inoculation of one of two pneumococcal strains isolated from infants with meningitis (ceftriaxone MICs, 4 and 1 ,g/ml, respectively). Two doses, 5 h apart, of each antibiotic were given intravenously (except that ceftriaxone was given as one dose). Cerebrospinal fluid bacterial concentrations were measured at 0, 5, 10, and 24 h after therapy was started. Clinafloxacin was the most active single agent against both strains. Against the more resistant strain, ceftriaxone or meropenem alone was ineffective. The combination of vancomycin and ceftriaxone was synergistic, suggesting that this combination might be effective for initial empiric therapy of pneumococcal meningitis until results of susceptibility studies are available.

Treatment of pneumococcal meningitis has become problematic because of the emergence of penicillin-and cephalosporin-resistant strains and because of the concern that dexamethasone therapy might reduce penetration of antibiotics into the cerebrospinal fluid (CSF). We addressed these issues with our rabbit meningitis model by studying two pneumococcal isolates that were resistant to penicillin and ceftriaxone and susceptible to vancomycin and rifampin. Ceftriaxone, vancomycin, and rifampin were given alone or in combination, with or without coadministration of dexamethasone. Treatment was started 12 to 14 h after intracisternal inoculation of i104 CFU of one of the organisms. Rifampin concentrations in serum and CSF were similar, regardless of whether dexamethasone was given, whereas those of ceftriaxone were somewhat lower at each time point in animals given dexamethasone. The penetration of vancomycin into CSF was consistently and substantially reduced with dexamethasone treatment, which resulted in a delay in CSF sterilization not observed in non-dexamethasone-treated animals. When rifampin was used with ceftriaxone for treatment of meningitis caused by the more resistant strain, bacteriologic cure occurred promptly, with or without dexamethasone therapy. In areas with high rates of occurrence of resistant pneumococcal strains, we believe initial empiric therapy of bacterial meningitis should include two antibiotics: ceftriaxone and either rifampin or vancomycin. When dexamethasone is used, the combination of ceftriaxone and rifampin is preferred for therapy.Dexamethasone has been shown to improve the long-term outcome in infants and children with bacterial meningitis, especially meningitis caused by Haemophilus influenzae type b (19,20,27,28). Its role in the management of Streptococcus pneumoniae meningitis is uncertain, although a retrospective study of 97 infants and children (18) and a prospective trial in 106 older patients (15) with pneumococcal meningitis suggested a satisfactory effect. With routine use of conjugate Haemophilus vaccines in many countries, meningitis caused by this organism has virtually disappeared (1,4,6,23,26,29), leaving the pneumococcus and meningococcus as the principal causes of meningitis in these areas.Attention has recently focused on management of pneumococcal meningitis because of the emergence of penicillin-and cephalosporin-resistant strains (7,8,10,11 (214) 648-2961. showed synergistic killing of resistant pneumococci in the rabbit meningitis model (12), and this regimen has been suggested for routine initial therapy of bacterial meningitis until results of culture and susceptibility studies are available.Because of concerns about the highly variable concentrations of vancomycin in cerebrospinal fluid (CSF) after parenteral administration (22,34) and about possible reduced penetration of vancomycin into CSF when dexamethasone is concomitantly given, the present study was undertaken. The impact of dexamethasone therapy on the decrease of clearance of resistant pneum...

Because chronic Mycoplasma pneumoniae respiratory infection is hypothesized to play a role in asthma, the potential of M. pneumoniae to establish chronic respiratory infection with associated pulmonary disease was investigated in a murine model. BALB/c mice were intranasally inoculated once with M. pneumoniae and examined at 109, 150, 245, 368, and 530 days postinoculation. M. pneumoniae was detected in bronchoalveolar lavage fluid by culture or PCR in 70 and 22% of mice at 109 and 530 days postinoculation, respectively. Lung histopathology was normal up to 368 days postinoculation. At 530 days, however, 78% of the mice inoculated with M. pneumoniae demonstrated abnormal histopathology characterized by peribronchial and perivascular mononuclear infiltrates. A mean histopathologic score (HPS) at 530 days of 5.1 was significantly greater (P < 0.01) than that for controls (HPS score of 0). Serum anti-M. pneumoniae immunoglobulin G was detectable in all of the mice inoculated with M. pneumoniae and was inversely correlated with HPS (r ‫؍‬ ؊0.95, P ‫؍‬ 0.01) at 530 days postinoculation. Unrestrained whole-body plethysmography measurement of enhanced pause revealed significantly elevated airway methacholine reactivity in M. pneumoniae-inoculated mice compared with that in controls at 245 days (P ‫؍‬ 0.03) and increased airway obstruction at 530 days (P ‫؍‬ 0.01). Murine M. pneumoniae respiratory infection can lead to chronic pulmonary disease characterized by airway hyperreactivity, airway obstruction, and histologic inflammation.While Mycoplasma pneumoniae is known to be a significant cause of acute respiratory illness in children and adults, the significance of chronic infection is undetermined. In humans, M. pneumoniae is reported to commonly be detectable by culture of the respiratory tract for up to several months after clinical recovery from acute pneumonia (5). Even after therapy with effective antibiotics, such as erythromycin or tetracycline, M. pneumoniae can still be cultured from respiratory secretions (6, 18). After receiving macrolides for 14 days, children have been found to have pulmonary structural abnormalities, by high-resolution computed tomography, suggestive of small airway obstruction 1 to 2 years after M. pneumoniae pneumonia with significantly increased frequency compared with that of controls. In these children, a greater antimycoplasma antibody titer was a significant risk factor for the development of abnormal pulmonary sequelae, suggesting that the host immune response may play a pathogenic role in this condition (10). The duration of M. pneumoniae infection in the human lower respiratory tract after acute pneumonia as determined by a method more sensitive than culture, such as PCR, has not been investigated in a controlled fashion.Of potentially greater relevance, chronic M. pneumoniae respiratory infection has been hypothesized to play a role in asthma. By PCR, M. pneumoniae has been detected in the lower airways of chronic, stable asthmatics with significantly greater frequency than in ...

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-1␣, 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.

No abstract