Rome. Pope Francis has developed pneumonia in both lungs, the Vatican said Tuesday, after new tests showed a further complication in the condition of the 88-year-old pontiff.

The Vatican said Francis’ respiratory infection also involves asthmatic bronchitis, which requires the use of cortisone antibiotic treatment. “Laboratory tests, chest X-ray, and the Holy Father’s clinical condition continue to present a complex picture,” the Vatican said.

Nevertheless the pope, who had the upper lobe of his right lung removed as a young man, is in good spirits and is grateful for the prayers for his recovery, Vatican spokesman Matteo Bruni said in a late update.

Francis was admitted to Rome’s Gemelli hospital in a “fair” condition on Friday after a weeklong bout of bronchitis worsened. On Monday, medical personnel determined that he was suffering from a polymicrobial respiratory tract infection, meaning a mix of viruses, bacteria and possibly other organisms had colonized his respiratory tract.

“The follow-up chest CT scan which the Holy Father underwent this afternoon ... demonstrated the onset of bilateral pneumonia, which required additional drug therapy,” Bruni said.

Bronchitis can lead to pneumonia, which is a deeper and far more serious infection of the lungs’ air sacs. Treatment varies by severity but can include providing oxygen through a nasal tube or mask, intravenous fluids -- and treatment of the underlying cause of the infection. To date, Francis is not known to be using supplemental oxygen, and he has eaten breakfast every day, read the newspapers, and done some work from his hospital room.

The Vatican has given no indication of how long the pope might remain hospitalized, only saying that the treatment of such a “complex clinical picture,” which has already required two changes in his drug regimen, would require an “adequate” stay.