Patients infected with atypical pathogens ( hazard ratio -LSB- HR -RSB- , @ ; @ % CI , @-@ @ ) or with Pneumonia Severity Index ( PSI ) category IV pneumonia ( HR , @ ; @ % CI , @-@ @ ) were less likely to reach clinical stability with monotherapy , whereas patients not infected with atypical pathogens ( HR , @ ; @ % CI , @-@ @ ) or with PSI category I to III pneumonia ( HR , @ ; @ % CI , @-@ @ ) had equivalent outcomes in the @ arms .