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Hospital Infantil Virgen del Rocío, Seville, Spain
Correspondence to: Ignacio Obando, MD, Hospital Infantil Virgen del Rocío, Avda Manuel Siurot s/n, Seville 41013, Spain; e-mail: IOSANTAELLA{at}telefonica.net
To the Editor:
Valles et al1 reported significantly reduced rates of pneumococci nonsusceptible to ß-lactams among adults patients with community-acquired pneumonia admitted to a single center in Barcelona, Spain, between 1999 and 2002 compared with a previous study. Although the authors1 suggested that the decrease in drug resistance could be partially related to the introduction of heptavalent pneumococcal conjugate vaccine, it seems unlikely that any significant vaccine impact occurred in Barcelona area during the study period due to very low vaccine uptake in that time period (4.8% estimated vaccine coverage in 2002).2 Nevertheless, vaccine coverage increased gradually since then, reaching an estimated 40 to 50% for the target population in Spain in 2005, and therefore conjugate vaccine may have had a significant role in further declines seen in pneumococcal resistance rates since 2002 (A. Fenoll, PhD; personal communication; May 2006).
Changes in pneumococcal resistance rates during the study period can be fully explained by reduction in antibiotic consumption and clonal dynamics of serotype 1. Nonsusceptible pneumococci declined gradually in Spain from 53% in 1997 to 43.9% in the first half of 2001 (just prior to vaccine licensure), along with a significant decrease in overall antibiotic use from 21.66 defined daily doses per 1,000 inhabitants per day in 1998 to 19.71 defined daily doses per 1,000 inhabitants per day in 2002 (p < 0.001).34 Serotype 1 was overrepresented in the study population (8.2%). Increased circulation of this penicillin susceptible serotype in Spain may have also contributed to reduction in drug resistance. This highly pathogenic serotype has been associated with dramatic temporal changes in epidemiology of invasive pneumococcal disease, and to this regard we have seen a significant increase in pneumococcal type 1 pediatric empyema in Southern Spain in recent years.5 It would be interesting to know whether the adults patients with pneumococcal pneumonia due to serotype 1 in the study showed the typical epidemiologic profile described for such patients (relative young age, lack of underlying disease, and low mortality).
Footnotes
The authors have no conflicts of interest to disclose.
The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
References
Institut Clínic de Pneumologia i Cirurgia Toràcica, Barcelona, Spain
Correspondence to: Xavier Vallès, PhD, FCCP, Institut Clínic de Pneumologia i Cirurgia Toràcica, Villarroel 170 Barcelona 08036, Spain; e-mail: xavier_valles04{at}hotmail.com
To the Editor:
Obando et al argued in their letter that the decrease observed in pneumococci not susceptible to ß-lactam therapy in adult patients with community-acquired pneumonia (CAP) in our article1 could not be explained by the introduction of the heptavalent pneumococcal conjugated vaccine (HPCV) given to infants in Spain, since the coverage of this vaccine was very low during the study period (4.8%).2 We pointed out the possible impact of the HPCV based on the coverage of serotypes that are found mostly in children with carrier status who are more prone to be associated with the nonsusceptibility to antibiotics,3 as has been previously observed.4 Nonetheless, this was a hypothesis based on the introduction of the HPCV throughout the private sector in Spain. In fact, a dramatic increase was observed in the coverage of children, achieving a rate of 34% during the period from 2002 to 2004,2 as Obando et al indicated.
At the time of the submission of our article, vaccine coverage in children was not available, and the article2 referred to was published at the same time as ours. We agree that the impact, if any, of pediatric vaccination during our study period was negligible with respect to the incidence of nonsusceptible pneumococcal CAP among adults. Nevertheless, our hypothesis could be relevant on the grounds of the decrease in the number of strains that are not susceptible to macrolide and ß-lactam therapy that have been described among children5; thus, an indirect impact may be expected in the adult population in the near future. On the other hand, Obando et al pointed out that our findings could be fully explained by the decrease in antibiotic consumption in Spain (as we already stated) and the dynamics of clonal serotype 1. We observed a relatively high overrepresentation of serotype 1 compared with previous series, but the absolute number was still low (10 of 122 strains isolated). Surveillance in future years should confirm this trend.
As suggested by Obando et al, we examined the epidemiologic profile of the patients with serotype 1 CAP but did not find any differences compared with the population (mean age, 67.8 years; comorbidity, 40%; and no deaths). Furthermore, the low numbers analyzed were not conclusive.
References
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