PHILADELPHIA — Positive pneumococcal cultures collected from symptomatic cancer patients declined from 1992 to 2012, but there was no difference in the number of identified invasive pneumococcal disease cases, according to data presented at IDWeek 2014.
Researchers from the Memorial Sloan Kettering Cancer Center examined patient records at the 469-bed facility from 1991 to 2012. Patients with cultures positive for Streptococcus pneumoniae (n=1,051) were included for analysis.
Cases of invasive pneumococcal disease (IPD) were defined as a positive culture from a sterile site or a positive respiratory culture with radiographic signs of pneumonia, with cases not meeting this criteria classified as colonization. Comparisons were made between 1991 to 2001 and 2002 to 2012 to reflect the introduction of the 7-valent pneumococcal vaccine given to children.
Fifty-four percent of patients with a positive culture had IPD. The incidence of positive cultures per 1,000 inpatient days declined from 0.44 in the early period to 0.28 in the late period (95% CI, 0.44-0.84), as did colonization rate (incidence rate ratio = 0.35; 95% CI, 0.15-0.56). However, there was no change in the IPD rate from time period to time period (incidence rate ratio = 1.00; 95% CI, 0.62-1.38).
“The decrease in overall incidence of positive cultures came from the decrease in, presumably, colonization because we were not able to find a difference in IPD,” Anna Kaltsas, MD, MS, of the infectious disease division of the Memorial Sloan Kettering Cancer Center, New York, told Infectious Disease News. “But the reasons for why we were unable to find a difference in IPD are up for further exploration.”
Age younger than 21 years or older than 65 years was associated with higher IPD incidence rates, while penicillin resistance, receipt of chemotherapy and underlying malignancy were not.
Serotype 6 was the most frequent pneumococcal serotype. However, serotyping data were only available for samples preceding 2001.
“We know that there’s a direct correlation between the development of IPD and colonization, so in order to get sick from these strains you need to be colonized with them first,” Kaltsas said. “We think there’s a continued benefit even though the jury is still out as to how immunogenic these vaccines are in this patient population … so we still advocate for vaccinating immunocompromised patients.”— by Dave Muoio
For more information:
Lee YJ. Abstract 440. Presented at: IDWeek 2014; Oct. 8-12, 2014; Philadelphia.
Disclosure: Two researchers reported research grant and investigator affiliations with Pfizer.