Although pediatric pneumococcal empyema is a rare complication of pneumonia, it has been increasingly reported in recent years (1
). The difficulty of culture-confirmed diagnosis remains a problem in pediatric empyema (1
). In our study, pleural fluid cultures were negative for all the patients, which may have been related to the use of antibiotics before admission to the study centers. Routine clinical practices, such as the administration of antibiotics prior to thoracentesis, can affect the sensitivity of bacterial cultures. Therefore, nonculture techniques may be necessary to detect the causative organism. Although bacterial culture is considered the standard method, pneumococcal antigen detection in empyema fluid is also a useful diagnostic tool (17
). This surveillance method made documentation of the serotype distribution of pneumococci in culture-negative patients possible. Twenty of the isolates could not be serotyped because the Bio-Plex antigen detection assay detected only a limited number of pneumococcal serotypes (14
). Although the serotyping method used has a limited ability to detect all pneumococcal serotypes, this non-culture-based rapid assay would assist in the identification of frequency and serotype distribution in the postvaccine era. Antigen detection methods are becoming more important for the serotyping of pneumococcal infections in countries with a high antibiotic usage rate and delayed admission to the hospital, such as Turkey. Information regarding S. pneumoniae
serotypes in patients with pneumonia is limited because sampling in children is difficult. Although the spectrum of etiologic bacteria differs from those in empyema and pneumonia, our data provide information about the pneumococcal serotypes that cause pneumonia in Turkey.
Although it is difficult to determine the actual proportion of S. pneumoniae
serotypes that cause parapneumonic empyema in children in the absence of knowledge of the other empyema-causing pathogens, S. pneumoniae
seems to be one of the leading causes, and serotype 1 is the most common. This finding agrees with the findings of studies by Fletcher et al. (17
), Eastham et al. (26
), Eltringham et al. (28
), and Byington et al. (1
). The reason for the high invasive potential of serotype 1 into the pleural space is unknown (17
Increases in the frequency of serotypes 3, 7F, and 19A in the post-PCV-7 era (24
) have been reported. Serotype 3 seemed more likely to be a cause of parapneumonic empyema in our study. One of the non-PCV-7 serotypes, 19A, has been identified in many studies as a cause of invasive pneumococcal disease following the licensure of PCV-7 (29
), and serotype 7F has been associated with children with severe or fatal pneumococcal infections (33
). We detected serotypes 19A and 7F in one patient each.
Some studies have shown a >75% efficacy of the PCV-7 vaccine against invasive disease (34
). Vaccination reduces radiologically confirmed pneumonia by 20.5 to 37%. In the United States, the effectiveness of PCV-7 against invasive pneumococcal disease (IPD) is controversial. The limited effectiveness of PCV-7 was reported in Utah as a result of the rapid emergence of IPD, particularly empyema, due to non-PCV-7 serotypes (10
). These findings encouraged the development of new pneumococcal conjugate vaccines with additional serotypes, namely, PCV-10 and PCV-13 (41
). However, clinical trials showing the efficacy of PCV-10 and PCV-13 against consolidated pneumonia and IPD have been limited. The compositions of PCV-10 and PCV-13 might have provided protection against empyema caused by non-PCV-7 serotypes in this study. However, the efficacies of pneumococcal vaccines may differ among different geographic regions due to variations in the serotype spectrum. Surveillance of local serotypes is critical for determining the PCV composition that also provides coverage of IPD-causing serotypes.
Routine vaccination with PCV-7 for children <1 year of age was agreed upon in Turkey at the end of 2008 and was included in the National Immunization Schedule in 2009. PCV-7 was used for 2 years in Turkey before being replaced by PCV-13 in November 2011. In 2010 and 2011, 96% and 97% of the target population, respectively, were vaccinated with PCV-7 (see http://www.sgk.gov.tr
). Despite this high coverage rate, the children in our study had not been vaccinated with either PCV-7 or PCV-13 because the majority of the children were older than the requisite age for routine vaccination, according to the Turkish Ministry of Health schedule. Additionally, the baseline data on the prevalence and serotype distribution of S. pneumoniae
isolates causing empyema in Turkey before the PCV era are limited. One of the aims of this study was to understand the impact of immunization on invasive pneumococcal infection in Turkey. We plan to monitor the incidence and etiologic agents of pediatric parapneumonic empyema in Turkey after the institution of the new vaccination practices.
After the PCV-7 era, vaccine authorities from various countries are in conflict regarding the selection of new 10- and 13-valent vaccines. The most common pneumococcal serotypes in our study were 1 and 5, which are covered by both the 10- and 13-valent vaccines. Serotype 3 was another important cause of empyema in the present study; this serotype is covered only by PCV-13. The potential serotype coverages of PCV-7, PCV-10, and PCV-13 in our study were 16.3%, 45.4%, and 60%, respectively. According to our data, PCV-13 seems to be the most protective against childhood pneumococcal empyema. Therefore, PCV-13 represents a promising vaccine against empyema.
Although limited, our data provide information regarding the serotype distribution of pneumococcal empyema in children in Turkey. We suggest that regional data are important for determining the most appropriate vaccine for the local S. pneumoniae epidemiological profile. As the incidence of this invasive disease is increasing, vaccines with coverage appropriate for each country are needed.