Impact of the pneumococcal conjugate vaccine on serotype distribution and antimicrobial resistance of invasive Streptococcus pneumoniae isolates in Dallas, TX, children from 1999 through 2005

BACKGROUND

Because the heptavalent pneumococcal conjugate vaccine has reduced vaccine-type invasive pneumococcal disease (IPD) in children, a greater proportion of IPD is now caused by nonvaccine (NVT) serotypes. We analyzed the serotypes, antimicrobial resistance profiles and genetic relatedness of Streptococcus pneumoniae responsible for IPD at Children's Medical Center of Dallas.

METHODS

S. pneumoniae isolates were collected from January 1, 1999 through December 31, 2005. Incidence of IPD was calculated using inpatient and emergency center admissions to Children's Medical Center of Dallas as the denominator. Isolates were serotyped, and their penicillin and cefotaxime susceptibility determined. The 19A isolates were further characterized by pulsed-field gel electrophoresis, multilocus sequence typing and determination of penicillin-binding proteins and mef and erm genes.

RESULTS

The incidence of IPD decreased from 93.6 cases/100,000 patients in 1999 to a nadir of 41 cases/100,000 patients in 2003 (P < 0.001). The number of IPD cases caused by serotype 19A increased, accounting for 40% of the cases of IPD in 2005. Penicillin and cefotaxime susceptibility of IPD isolates did not change from 1999 through 2005 (P = 0.687). There was a decrease in penicillin (P < 0.001) and cefotaxime (P = 0.034) susceptibility in NVT serotypes from 1999 to 2005. Molecular characterization of 19A isolates revealed a predominance of ST-199 (62%). Several highly penicillin-resistant and intermediately cefotaxime-resistant strains emerged in 2004 and 2005.

CONCLUSIONS

In Dallas, heptavalent pneumococcal conjugate vaccine reduced the incidence of IPD from 1999 to 2005 by reducing the incidence of vaccine-type disease. NVT serotypes, particularly 19A, were prevalent and more resistant to antimicrobials in 2004 and 2005.

Variation in the presence of neuraminidase genes among Streptococcus pneumoniae isolates with identical sequence types

Streptococcus pneumoniae frequently colonizes the upper respiratory tract of young children and is an important cause of otitis media and invasive disease. Carriage is more common than disease, yet the genetic factors that predispose a given clone for disease are not known. The relationship between capsule type, genetic background, and virulence is complex, and important questions remain regarding how pneumococcal clones differ in their ability to cause disease. Pneumococcal neuraminidase cleaves sialic acid-containing substrates and is thought to be important for pneumococcal virulence. We describe the distribution of multilocus sequence types (ST), capsule type, and neuraminidase genes among 342 carriage, middle ear, blood, and cerebrospinal fluid (CSF) pneumococcal strains from young children. We found 149 STs among our S. pneumoniae isolates. nanA was present in all strains, while nanB and nanC were present in 96% and 51% of isolates, respectively. The distribution of nanC varied among the strain collections from different tissue sources (P = 0.03). The prevalence of nanC was 1.41 (95% confidence interval, 1.11, 1.79) times higher among CSF isolates than among carriage isolates. We identified isolates of the same ST that differed in the presence of nanB and nanC. These studies demonstrate that virulence determinants, other than capsule loci, vary among strains of identical ST. Our studies suggest that the presence of nanC may be important for tissue-specific virulence. Studies that both incorporate MLST and take into account additional virulence determinants will provide a greater understanding of the pneumococcal virulence potential.

Cefdinir pharmacokinetics and tolerability in children receiving 25 mg/kg once daily

BACKGROUND

Of several oral cephalosporins, cefdinir is recommended as an alternative therapy for children with acute otitis media who have type 1 hypersensitivity to beta-lactams. Because the current cefdinir dosage of 14 mg/kg/d is approved for treatment of acute otitis media caused by penicillin-susceptible Streptococcus pneumoniae, we hypothesized that a 25-mg/kg dose given daily would be more effective for nonsusceptible S. pneumoniae.

METHODS

We performed pharmacokinetic analyses on 37 infants and children who were given cefdinir in dosages of 14 or 25 mg/kg once daily for 10 days, for the treatment of respiratory and skin or skin structure infections. Cefdinir plasma concentrations were determined with validated liquid chromatology, and pharmacokinetics and pharmacodynamics were determined in relation to the minimum inhibitory concentration values of S. pneumoniae.

RESULTS

The maximal plasma concentrations and area-under-the-curve values were significantly higher after the 25-mg/kg in relation to the minimum inhibitory concentration values for S. pneumoniae strains. The pharmacodynamics measure of bacteriologic effectiveness was <40% of the dosing interval (ie, 24 hours), indicating that many of the penicillin-nonsusceptible S. pneumoniae causing acute otitis media would not be effectively treated. Diarrhea occurred in 20% of the 39 subjects that received the larger dosage of cefdinir.

CONCLUSION

A cefdinir dosage of 25 mg/kg daily would be ineffective for treatment of acute otitis media caused by penicillin-nonsusceptible S. pneumoniae strain.

The safety of 7-valent pneumococcal conjugate vaccine

Streptococcus pneumoniae is one of the most important bacterial pathogens of young children. Currently, there are several conjugate vaccines against S. pneumoniae in various stages of laboratory development, clinical evaluation or currently licensed. Heptavalent pneumococcal conjugate vaccine (Wyeth Lederle; PCV-7) is the only currently approved pneumococcal conjugate vaccine indicated against invasive pneumococcal disease for children younger than two years of age. Safety studies have shown that the PCV-7 is acceptably safe when administered alone, simultaneously with other childhood vaccines or in combination with Haemophilus influenzae type b conjugate vaccines. In addition, PCV-7 vaccine was generally safe and immunogenic among infants infected with HIV and those with sickle cell disease. Surveillance studies to monitor the serotype distribution in invasive pneumococcal disease is important to determine that PCV-7 continues to be the optimal vaccination for prevention of pneumococcal invasive disease.

Mobilization of plasmacytoid and myeloid dendritic cells to mucosal sites in children with respiratory syncytial virus and other viral respiratory infections

BACKGROUND

Respiratory syncytial virus (RSV) is the principal etiologic agent of bronchiolitis and viral pneumonia in infants and young children. Yet, many aspects of its immunopathogenesis are not well understood.

METHODS

We analyzed the immune cells that are mobilized by RSV and other respiratory viruses, by studying nasal wash samples from children hospitalized with acute viral respiratory infections.

RESULTS

RSV mobilizes virtually all blood immune cells, including myeloid dendritic cells (DCs) and plasmacytoid DCs (pDCs), to the nasal mucosa. DCs were also mobilized to the nasal mucosa of children with other viral respiratory infections. The increased number of pDCs in the nasal compartment significantly correlates with RSV load (P=.022), and it is associated with a significant decrease in the number of pDCs in the blood (P=.007). The influx of DCs in the nasal mucosa is not transient, as even higher numbers of both DC subsets were found in respiratory secretions weeks after the acute symptoms of RSV infection had resolved. Immunochemistry analysis of respiratory samples has demonstrated the presence of the RSV fusion protein within HLA-DR-positive cells.

CONCLUSION

Infection with RSV and other respiratory viruses mobilizes DCs to the site of viral entry.

Effect of the 7-valent pneumococcal conjugate vaccine on nasopharyngeal colonization by Streptococcus pneumoniae in the first 2 years of life

BACKGROUND

Studies suggest that the 7-valent pneumococcal conjugate vaccine (PCV7) reduces carriage of vaccine-type (VT) Streptococcus pneumoniae (SP). We studied the effect of PCV7 on carriage of VT- and non-VT (NVT) SP, by studying the effect of PCV7 on nasopharyngeal (NP) colonization by VT and NVT SP during early childhood.

METHODS

At 2 months of age, 278 infants were enrolled in this study. To determine carriage of SP, NP samples were obtained before each PCV7 dose, at 9 months of age, and 2-3 months after the booster dose of vaccine.

RESULTS

The carriage of SP increased slightly, from 12% (95% confidence interval [CI], 8%-16%) of subjects at 2 months of age to 18% (95% CI, 13%-23%) at 4 months of age (P<.05). Carriage of SP remained in 24%-30% of subjects during subsequent months. Between the 12- and 18-month visits, the carriage rate of VT SP decreased significantly, from 18% (95% CI, 13%-23%) to 9% (95% CI, 5%-13%) of subjects (P=.001). The trend of a decrease in carriage of penicillin-nonsusceptible SP, from 16% of subjects (95% CI, 11%-21%) at the 12-15-month visit to 9% (95% CI, 5%-13%) at the 15-18-month visit, was found after the booster dose of vaccine.

CONCLUSION

The reduction of VT-SP colonization and replacement by NVT SP after the booster dose of vaccine suggests the possibility that widespread vaccination will result in replacement of pneumococci mainly by antibiotic-susceptible NVT SP.

Effects of large dosages of amoxicillin/clavulanate or azithromycin on nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, nonpneumococcal alpha-hemolytic streptococci, and Staphylococcus aureus in children with acute otitis media

Prior use of antibiotics is associated with carriage of resistant bacteria. Colonization by Streptococcus pneumoniae, Haemophilus influenzae, nonpneumococcal alpha-hemolytic streptococci (NPAHS), and Staphylococcus aureus was evaluated in children receiving antibiotic therapy for acute otitis media and in untreated, healthy control subjects. Children were randomly assigned to receive either amoxicillin/clavulanate (90 mg/kg per day) or azithromycin. Swabs were obtained before initiating therapy and again 2 weeks and 2 months after initiating therapy. We also obtained swabs from control subjects at the time of enrollment and 2 weeks and 2 months after enrollment. The decrease in the rate of carriage of S. pneumoniae and H. influenzae at 2 weeks was significant only in the amoxicillin/clavulanate group (P<.001 and P=.005, respectively). The rate of nasopharyngeal colonization with NPAHS among treated patients increased from 23% to 39% at 2 months (P=.01). This increase was similar for both treatment groups. These results suggest that the competitive balance between organisms is altered by antibiotic therapy.

Diagnosis of Streptococcus pneumoniae lower respiratory infection in hospitalized children by culture, polymerase chain reaction, serological testing, and urinary antigen detection

A prospective study of 154 consecutive high-risk hospitalized children with lower respiratory infections was conducted to determine the clinical utility of a pneumolysin-based polymerase chain reaction (PCR) assay compared with blood and pleural fluid cultures and serological and urinary antigen tests to determine the incidence of Streptococcus pneumoniae. Whole blood, buffy coat, or plasma samples from 67 children (44%) tested positive by PCR. Sensitivity was 100% among 11 promptly tested culture-confirmed children and specificity was 95% among control subjects. Age, prior oral antibiotic therapy, and pneumococcal nasopharyngeal colonization did not influence PCR results, whereas several surrogates of disease severity were associated with positive tests. Although serological and urinary antigen tests had comparable sensitivity, specificity varied among infected children, and statistical agreement among all assays was limited. These findings support the use of PCR tests to evaluate the protective efficacy of pneumococcal conjugate vaccines and to identify promptly children with pretreated or nonbacteremic pneumococcal lower respiratory infections.

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.

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.

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.

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.

Increased carriage of resistant non-pneumococcal alpha-hemolytic streptococci after antibiotic therapy

OBJECTIVE

We compared colonization and resistance rates of non-pneumococcal alpha-hemolytic streptococci (AHS) and Streptococcus pneumoniae in children receiving antibiotic therapy for acute otitis media.

STUDY DESIGN

Between December 1997 and September 1998, children 6 months to 6 years of age, diagnosed with acute otitis media were randomly assigned to receive amoxicillin/clavulanate (Augmentin) 45 mg/kg/d in 2 divided doses for 10 days or azithromycin (Zithromax), 10 mg/kg, once on the first day, followed by 5 mg/kg daily for 4 days. Nasopharyngeal swabs for culture were obtained before and at 2 weeks and 2 months after the start of therapy. Streptococci were identified by species, and antibiotic susceptibility was determined by the epsilometric test.

RESULTS

One hundred six children completed the 2-week follow-up and 2-month follow-up, respectively. The nasopharyngeal carriage rate of non-pneumococcal AHS increased from 14% before treatment to 32% at the 2-week follow-up (P =.02) and was similar in both treatment groups. In contrast, the carriage of S pneumoniae decreased from 51% before therapy to 27% at the 2-week follow-up (P =.002). The carriage of penicillin-resistant AHS strains (minimum inhibitory concentration > 1 microg/mL) increased from 9% before treatment to 26% at 2 weeks and 36% at 2 months.

CONCLUSIONS

Amoxicillin/clavulanate and azithromycin therapy resulted in increased isolation of nasopharyngeal non-pneumococcal AHS, many of which were multidrug-resistant, in contrast to a decrease in pneumococcal carriage. This suggests that the competitive balance between these 2 groups of organisms was disturbed as a result of differential antibiotic susceptibility. The importance of drug-resistant AHS as a reservoir for resistance genes for S pneumoniae warrants further investigation.

Efficacy of gatifloxacin in experimental Escherichia coli meningitis

The effectiveness of gatifloxacin therapy (15 mg/kg every 5 h [q5h]) was compared with that of meropenem (75 mg/kg q5h) and cefotaxime (75 mg/kg q5h) therapy in experimental meningitis caused by a beta-lactamase-producing strain of Escherichia coli. Gatifloxacin therapy was more rapidly bactericidal than cefotaxime but similar to meropenem therapy (bacterial killing rates at 5 h, 0.83 +/- 0.26, 0. 46 +/- 0.3, and 0.73 +/- 0.17 CFU/ml/h, respectively; P = 0.03 for gatifloxacin versus cefotaxime). At 10 h, seven of eight animals treated with gatifloxacin had <10 CFU/ml in their cerebrospinal fluid, compared with one of seven treated with cefotaxime therapy (P = 0.01). Gatifloxacin was at least as effective as currently available antibiotics in this model of E. coli meningitis.

Pharmacodynamics of trovafloxacin in a mouse model of cephalosporin-resistant Streptococcus pneumoniae pneumonia

Trovafloxacin is a potentially useful agent for treatment of infections caused by cephalosporin-resistant Streptococcus pneumoniae. We studied the effectiveness of trovafloxacin therapy and examined the correlation between pharmacodynamic indices in serum and lung, and bacterial killing. Immunocompetent Balb/c mice were infected by intranasal inoculation of a cephalosporin-resistant S. pneumoniae isolate (MIC of ceftriaxone and trovafloxacin 2 and 0.06 mg/L, respectively). Trovafloxacin 10-30 mg/kg/day in one or three divided doses was started 15 h after infection. Serum and lung drug concentrations were measured at multiple time points for 24 h. Serum concentrations peaked at 30-60 min and lung concentrations approximately 30 min later. The serum T1/2 was approximately 9 h and lung T1/2 varied from 5 to 9 h. Lung AUC and Cmax values were 2-3 times greater than those in serum. At the start of therapy lung bacterial concentrations were 8.4 +/- 0.3 log10 cfu/mL and 24 h later had decreased by 3.5 +/- 0.2, 4.0 +/- 0.2, 0.8 +/- 0.3 and 1.0 +/- 1.2 log10 cfu/mL with 30 mg/kg x 1, 10 mg/kg x 3, 10 mg/kg x 1 and 3.3 mg/kg x 3 regimens, respectively. Although the larger dosages were more effective (P < 0.001) the differences between divided and single dosage regimens were not significant. Trovafloxacin serum AUC/MIC ratio correlated best with bacterial killing in the lungs over 24 h. Trovafloxacin is likely to be useful in the treatment of cephalosporin-resistant S. pneumoniae pneumonia.

Pharmacodynamics of gatifloxacin in cerebrospinal fluid in experimental cephalosporin-resistant pneumococcal meningitis

The purpose of this study was to evaluate the cerebrospinal fluid (CSF) pharmacodynamics of a new fluoroquinolone, gatifloxacin (AM-1155), in experimental pneumococcal meningitis. The penetration of gatifloxacin into CSF, calculated as the percentage of the area under the concentration-time curve (AUC) in CSF over the AUC in blood, was 46 to 56%. Gatifloxacin showed linear pharmacokinetics in CSF, and 1 h after intravenous dosages of 7.5, 15, or 30 mg/kg of body weight, peak CSF concentrations were 0.46 +/- 0.08 (mean +/- standard deviation), 0.94 +/- 0.16, and 1.84 +/- 0.5 microg/ml, respectively. The elimination half-life of gatifloxacin in CSF was 3. 8 to 5.6 h (compared with 2.7 to 3.2 h in blood). There was a significant interrelationship among the highest measured values of gatifloxacin in blood and CSF/minimal bactericidal concentration (Cpeak/MBC), the time antibiotic concentrations exceeded the MBC (T > MBC), and AUC/MBC (r = 0.94); in single-dose experiments, each correlated significantly with the bacterial killing rate. Divided-dose regimens, resulting in greater T > MBC values but lower Cpeak/MBC ratios, were more effective in terms of bacterial clearance compared with corresponding single-dose regimens. Gatifloxacin therapy was as effective as currently recommended regimens (e.g., a combination of ceftriaxone and vancomycin) against this highly cephalosporin-resistant pneumococcal strain. The bactericidal activity of gatifloxacin in CSF was closely related to the AUC/MBC ratio, but maximal activity was achieved only when drug concentrations exceeded the MBC for the entire dosing interval.

Serum interleukin-6 in bacterial and nonbacterial acute otitis media

BACKGROUND

Increasing prevalence of antibiotic-resistant bacteria is a serious clinical problem that calls for reduction of unnecessary use of antibiotics. Acute otitis media (AOM) is the most common reason for antibiotic therapy in the United States. Approximately 30% of AOM cases do not have a bacterial etiology. Rapid identification of these cases could help withhold unnecessary antibiotic treatment.

OBJECTIVE

To determine the usefulness of serum levels of interleukin-6 (IL-6), an acute phase cytokine shown to be a reliable marker of neonatal bacterial infection, in differentiation between bacterial and nonbacterial AOM in children.

STUDY DESIGN

IL-6 was measured in stored serum samples from 184 children (mean age, 22 months) with AOM who were enrolled in antibiotic efficacy trials at our department. The samples were obtained at enrollment and at 9 to 12 days after initiation of antibiotic therapy. Sera from 21 uninfected children (mean age, 23 months) were used as controls. The etiology of AOM was determined by bacterial and viral cultures as well as respiratory syncytial virus antigen detection in the middle ear fluids obtained by tympanocentesis.

RESULTS

Bacterial etiology of AOM was confirmed in 125 children (68%), whereas in 59 children (32%) no bacterial pathogen could be detected in the middle ear fluid. Children with bacterial AOM had significantly higher IL-6 levels than those with nonbacterial AOM (median, 11.5 vs 3.7 pg/mL). However, this difference was almost entirely attributable to pneumococcal AOM specifically. IL-6 levels in children with AOM caused by Streptococcus pneumoniae were significantly higher (median, 40.1 pg/mL) than in AOM caused by Haemophilus influenzae (7.3 pg/mL) or Moraxella catarrhalis (6.8 pg/mL). At the cutoff value of 30 pg/mL, the specificity of IL-6 for detection of pneumococcal AOM was 91% with a sensitivity of 61%, but its sensitivity for detection of bacterial AOM in general was only 27%.

CONCLUSIONS

Low levels of IL-6 do not rule out bacterial etiology of AOM in general; therefore, IL-6 is not sensitive enough as a marker of bacterial AOM. Surprisingly, serum IL-6 levels in pneumococcal AOM were significantly higher than the levels associated with other bacterial AOM, and serum IL-6 levels of >30 pg/mL were highly specific for pneumococcal AOM. These findings suggest a distinctive role for S pneumoniae in the pathogenesis of AOM.