High prevalence of multiple serotypes of pneumococci in patients with pneumonia and their associated risk factors

Bhim Gopal Dhoubhadel; Motoi Suzuki; Tomoko Ishifuji; Makito Yaegashi; Norichika Asoh; Masayuki Ishida; Sugihiro Hamaguchi; Masahiro Aoshima; Michio Yasunami; Koya Ariyoshi; Konosuke Morimoto; Adult Pneumonia Study Group-Japan (APSG-J)

doi:10.1136/thoraxjnl-2021-217979

High prevalence of multiple serotypes of pneumococci in patients with pneumonia and their associated risk factors

Thorax. 2022 Apr 26;77(11):1121-1130. doi: 10.1136/thoraxjnl-2021-217979. Online ahead of print.

Authors

Collaborators

Adult Pneumonia Study Group-Japan (APSG-J):
Masahiko Abe, Masayuki Chikamori, Akitsugu Furumoto, Naohisa Hamashige, Naoto Hosokawa, Hiroyuki Ito, Satoshi Kakiuchi, Norihiro Kaneko, Shungo Katoh, Naoko Katsurada, Emi Kitashoji, Kei Matsuki, Hiroshi Nakaoka, Kei Nakashima, Yoshihito Otsuka, Eiichiro Sando, Kaori Shibui, Takaharu Shimazaki, Daisuke Suzuki, Masahiro Takaki, Kenzo Tanaka, Kentaro Tochitani, Yoshiko Tsuchihashi, Takao Wakabayashi, Kiwao Watanabe, Lay-Myint Yoshida

Affiliations

¹ Department of Respiratory Infections, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
² Department of Global Health, School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan.
³ Infectious Disease Surveillance Center, National Institute of Infectious Diseases, Tokyo, Japan.
⁴ Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
⁵ Department of General Internal Medicine, Kameda Medical Center, Chiba, Japan.
⁶ Department of Internal Medicine, Juzenkai Hospital, Nagasaki, Japan.
⁷ Department of Internal Medicine, Chikamori Hospital, Kochi, Japan.
⁸ Department of General Internal Medicine, Fukushima Medical University, Fukushima, Japan.
⁹ Department of Pulmonology, Kameda Medical Center, Chiba, Japan.
¹⁰ Life Science Institute, Saga-Ken Medical Centre Koseikan, Saga, Japan.
¹¹ Department of Respiratory Infections, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan komorimo@nagasaki-u.ac.jp.

Abstract

Background: Multiple serotypes of pneumococci have epidemiological and clinical implications, such as the emergence of non-vaccine serotypes and the acquisition of antimicrobial resistance. Prevalence of multiple serotypes of pneumococci in adults and their risk factors are not known.

Methods: We enrolled adult patients from age ≥15 years with radiologically confirmed pneumonia in four hospitals across Japan. Pneumococcal pneumonia was defined with a pneumococcal bacterial density of ≥10⁴/mL in sputum by lytA quantitative PCR, and serotypes were determined. Pneumonias with a single serotype were categorised as single-serotype pneumococcal pneumonia and with two or more serotypes as multiple-serotype pneumococcal pneumonia. Multivariable logistic regression was used to assess the risk factors.

Results: 3470 patients (median age 77 years, IQR 65-85) were enrolled. Pneumococcal pneumonia was identified in 476 (18.3%, n=2605) patients. Multiple serotypes were detected in 42% of them. Risk of having multiple serotypes was low among patients who had received 23-valent pneumococcal polysaccharide vaccine (PPSV23) vaccines (adjusted OR 0.51 (95% CI 0.27 to 0.94)). Proportion of non-PCV7 PPSV23 serotypes in overall distribution of multiple serotypes was 67.4% (n=324/481) compared with 46.4% (n=128/276) in that of single serotypes (p=0.001). Serotypes 5, 9N/9L, 10A, 12/22/46, 17F and 35F were associated with multiple-serotype pneumonia, and serotypes 6A/6B, 23F, 11 and 6C/6D were associated with single-serotype pneumonia. Proportion of more invasive serotypes (serotypes 1, 5, 7F, 8) was significantly higher in multiple-serotype pneumonia (p=0.001).

Conclusions: Multiple serotypes of pneumococci are common in sputum of adult patients with pneumonia. The risk of multiple-serotype pneumococcal pneumonia is lower than that of single-serotype pneumococcal pneumonia among PPSV23-vaccinated patients.

Trial registration number: UMIN000006909.

Keywords: bacterial infection; clinical epidemiology; pneumonia; respiratory infection.