ROME (CNS) -- More than 24 hours after he entered the hospital, Pope Francis' doctors reported a "marked improvement" in his condition, which they attributed to treatment with intravenous antibiotics.

The tests the pope underwent after entering Rome's Gemelli hospital with difficulty breathing revealed he had bronchitis, said a medical bulletin released by the Vatican press office March 30. "Based on his expected progress, the Holy Father could be discharged in the coming days."

Earlier in the day, the Vatican said the pope "rested well" his first night in the hospital and was "steadily improving" from what it described as a respiratory infection.

He spent the morning reading some newspapers, eating breakfast and had "resumed working," the Vatican had said. Before lunch, he went to the chapel near his hospital room to pray, and he received Communion.

The evening bulletin said, "Pope Francis spent the afternoon at Gemelli devoting himself to rest, prayer and some work duties."

The Vatican said that the pope had complained of "some respiratory difficulties" in recent days and was admitted to the hospital for medical tests, the results of which detected a "respiratory infection" but excluded COVID-19.

The 86-year-old pope is missing a piece of his lung that was removed in 1957 when he was 20 years old and training to become a priest in his native Argentina. He has insisted the operation has had no lasting impact on his health.

Photographers, television cameras and reporters waited outside the hospital March 30, but they formed the only crowd gathered there for the pope.

Before going to the hospital, Pope Francis held his weekly general audience in St. Peter's Square and showed no obvious signs of breathing problems.

The Vatican originally said the pope was taken to the hospital for "previously planned tests," and later stated that he would remain the hospital for a few days. Pope Francis' scheduled meetings for March 30 and 31 were cancelled "to make room in his agenda for the tests to continue," an official said.

"Pope Francis is touched by the many messages received and expresses his gratitude for the closeness and prayer," the Vatican said in its second statement March 29.

Italian media reported that the pope was taken to the hospital in an ambulance, but the Vatican press office refused to comment on those reports.

The Gemelli hospital, part of the Catholic University of the Sacred Heart, keeps a suite of rooms reserved for the popes on its 10th floor.

Pope Francis had spent 10 days there in July 2021 after undergoing a three-hour surgery that included a left hemicolectomy, which is the removal of the descending part of the colon, a surgery that can be recommended to treat diverticulitis.

In late January, the pope told the Associated Press that his diverticulitis had returned, but insisted he was in good health for his age.

In an interview with the Reuters news agency in July 2022, he dismissed as "court gossip" rumors that cancer was found during his colon operation.