Streptococcus pneumoniae

1. Introduction
The incidence of invasive pneumococcal disease (IPD) decreased
substantially in both children and adults after heptavalent pneumococcal
conjugate vaccine (PCV7) was introduced into the US
childhood immunization schedule in 2000 [1,2]. According to
national surveillance data, IPD has decreased in all age groups
with the greatest declines noted in those younger than five yearsand those older than 65 years [1]. However, the epidemiology of
IPD in Utah children has differed from that of Center for Disease
Control Active Bacterial Core (ABCs) surveillance sites. The distribution
of serotypes in Utah among children with IPD before the
introduction of PCV7 included a greater proportion of non-vaccine
serotypes [3]. Subsequent investigations demonstrated modestdeclines in IPD and more rapid emergence of non-vaccine serotypes
in Utah children compared to children from ABCs [3]. Further, the
clinical syndromes associated with these serotypes included primarily
severe pulmonary disease with necrotizing pneumonia and
empyema (PE), particularly due to emerging serotypes 3, 7F, and
19A [4,5]. The effects of PCV7 uptake in Utah children on IPD in Utah
adultsare unknown. The objectives of this study were to (1) document
the clinical IPD syndromes in adults, (2) define the serotype
distribution of IPD in adults in Northern Utah, and (3) compare the
adult serotype distribution to the pediatric serotype distribution in
Utah at the end of the PCV7 era. Data regarding the impact of PCV7
on adults will help predict the effects of newly licensed13-valent
pneumococcal conjugate vaccine (PCV13).
2. Methods
This study was approved by the institutional review boards of
Intermountain Healthcare (Intermountain) and the University of
Utah. We collected pneumococcal isolates from sterile site cultures
obtained from adults 18 years and older cared for within the
Intermountain Healthcare system from November 2009 to October
2010. All isolateswere identified and stored at the Intermountain
Medical Center (IMC) microbiology laboratory. Streptococcus
pneumoniae was identified by Gram stain, colony morphology,
and optochin sensitivity. Identification was confirmed by the BD
Phoenix Automated Microbiology System (BD Diagnostics, Franklin
Lakes, NJ, USA). The IMC laboratory performs microbial identification
for 14 of 20 Intermountaininpatient facilities, as well as several
outpatient clinics. Intermountain has an overall market share of
56% of the adult population in the state of Utah.
.
IPD was defined as isolation of S. pneumoniae from blood, cerebrospinal
fluid, ascites, pleural fluid, pericardial fluid, joint fluid, or
internal body site. We obtained demographic, clinical, and microbiologic
data from the IntermountainElectronic Data Warehouse
(EDW), an electronic storage site for data from patients receiving
care at all Intermountain facilities. We reviewed respiratory virus
testing that occurred 30 days before to seven days after the diagnosis
of IPD. Viral testing was performed at the discretion of the
treating physician by polymerase chain reaction, direct fluorescence
antigen testing, and/or viralculture. We extracted empyema
and comorbidity data manually from physician notes. We considered
comorbidities to be chronic diseases which require ongoing
medical care and were present at the time of IPD. We obtained
data regarding pneumococcal polysaccharide vaccination (PPV23)
from inpatient physician notes and pharmacy records. Outpatient
vaccine records were not available.
We recoveredall pneumococcal isolates stored in the IMC
laboratory. Not all adult IPD isolates were archived systematically
during the study period. To examine whether this introduced bias
or patients with available isolates were likely to be a representative
sample of all adults with IPD, we compared clinical and
demographic features of patients with archived isolates to those
without (Table 1). We...