[A case of severe pneumonia in an elderly man, caused by Citrobacter freundii suspected to have a low susceptibility to imipenem/cilastatin sodium].

An 80-year-old blind man with lepromatous leprosy suffered from right femoral neck and humeral neck fractures on July 9, 1993. Because of fever (38.6 degrees C), difficult expectoration and diffuse bilateral perihilar infiltrates with consolidation in the left lower lung field on his chest radiograph, severe pneumonia was diagnosed. With intravenous hyperalimentation, imipenem/cilastatin (IPM/CS), ceftazidime, minocycline, gentamicin (GM), and human immunoglobulin were administrated. On July 29, hip screw-plate fixation was done. Citrobacter freundii was isolated from the sputum and its susceptibility was IPM/CS+, GM3+. Multi-drug therapy with GM and other antibiotics improved the patients' condition, but Citrobacter freundii were still detected and 43 days of medication were needed. According to a report by the Ministry of Health and Welfare in 1992, the resistance rate of IPM/CS against Citrobacter freundii is only 0.7%, and IPM/CS is more effective than beta-Lactams. This is a very rare case of severe pneumonia in an elderly patient caused by Citrobacter freundii that was suspected to have low susceptibility to IPM/CS.