Lab Med Online.  2016 Oct;6(4):250-254. 10.3343/lmo.2016.6.4.250.

A Case of Pneumonia Caused by Pneumocystis jirovecii Resistant to Trimethoprim/Sulfamethoxazole in the Absence of Previous Drug Exposure

• Ahn A
• Chang J
• Sung H
• Kim MN

• KMID: 2353428
• DOI: http://doi.org/10.3343/lmo.2016.6.4.250

Abstract

Pneumocystis jirovecii pneumonia is a common opportunistic infection seen in patients with human immunodeficiency virus (HIV) infection. Dihydropteroate synthase (DHPS) is a target of sulfa drugs, and mutations in DHPS gene are associated with failure in treatment and prophylaxis of P. jirovecii infections in HIV-infected patients. Here, we report a case of a patient with P. jirovecii infection, harboring DHPS gene mutations, who had not been previously treated with trimethoprim/sulfamethoxazole (TMP/SMX). A 50-yr-old man was admitted to the hospital with symptoms such as fever, cough, sputum, and sore throat. Chest computed tomography scanning revealed diffuse ground glass opacity in both the lungs, and the patient was diagnosed as having HIV infection with a CD4+ T cell count of 22/µL. Immunohistochemical test results were positive for P. jirovecii. He was treated with TMP/SMX; however, his symptoms and laboratory findings did not improve. The treatment was changed to clindamycin and primaquine, and his symptoms improved after 3 days. Molecular testing of the sample for the detection of DHPS gene mutations and the typing of mitochondrial large subunit rRNA (mtlsurRNA) revealed DHPS gene mutations at codon 55 and 57, respectively, and the case had type 3 mtlsurRNA. This case study illustrates that DHPS mutation test results can be positive even in patients without previous exposure to TMP/SMX.

Keyword

Pneumocystis jirovecii; Dihydropteroate synthase; HIV

MeSH Terms

Cell Count
Clindamycin
Codon
Cough
Dihydropteroate Synthase
Fever
Glass
HIV
HIV Infections
Humans
Lung
Opportunistic Infections
Pharyngitis
Pneumocystis jirovecii*
Pneumocystis*
Pneumonia*
Primaquine
Sputum
Thorax
Clindamycin
Codon
Dihydropteroate Synthase
Primaquine

Figure

• 

  Fig. 1 Initial chest computed tomography reveals diffuse ill-defined ground glass opacities in both lungs, which indicates atypical pneumonia caused by cytomegalovirus or Pneumocystis.

• 

  Fig. 2 Immunohistochemical stain of organism clusters from bronchoalveolar lavage using Pneumocystis jirovecii Clone 3F6 (DAKO Corp., Carpinteria, Calif., USA) (×400).

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  Fig. 3 DHPS mutation study of the patient shows synonymous mutation of Thr55Ala and Pro57Ser. The electropherogram indicates there are alanine and serine in 55th and 57th codon, respectively, instead of threonine and proline in wild type.

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