SAN FRANCISCO — There are two important things to know about the recently identified threat of staphylococcal necrotizing pneumonia: It generally follows an influenza illness, and a physician seeing a patient in the clinic or office is not going to miss it.
That was the message of John G. Bartlett, M.D., who has been involved with four cases of necrotizing pneumonia seen in Baltimore recently. All of the cases occurred during a period of 2 months in the winter of 2003–2004, and all were community acquired, he said at the annual meeting of the American College of Physicians.
“These patients are not subtle. They are severely ill,” said Dr. Bartlett, chief of the division of infectious diseases at Johns Hopkins University, Baltimore.
Each of the four cases occurred in previously healthy individuals without risk factors for staphylococcal infection. This is what makes the cases worrisome and something physicians everywhere should be familiar with, even though the chances of seeing a case at present are extremely low and a physician encountering such a patient would likely recognize right away that he or she was not dealing with bronchitis or viral pneumonia, Dr. Bartlett said.
The course of these infections appears to progress very rapidly. Two of the patients had been vomiting, and each had severe dyspnea and/or hemoptysis and shock.
All of the patients appeared to have had influenza prior to their bacterial pneumonia, and it is well known that staphylococcal pneumonia is generally a superinfection following influenza, Dr. Bartlett said.
Two of the patients had serologic evidence of influenza A infection, and two of the patients were not tested but were determined to have an influenza-like prodrome.
One of the patients died, and two needed below-the-knee amputations.
In each of the cases, the only bacterial pathogen recovered from the patients was methicillin-resistant Staphylococcus aureus (MRSA), and the cases therefore provide further evidence that methicillin resistance is becoming more prevalent among community-acquired staphylococcus infections.
Cases of necrotizing pneumonia have been reported previously in Europe. A paper published in April in the New England Journal of Medicine reported 14 cases of MRSA necrotizing fasciitis, and another article in the same issue said that 8%–20% of MRSA isolates being collected by laboratories are not coming from the hospital.
An increase in the prevalence of MRSA has also been reported in California jails.
MRSA in the community is different from MRSA in the hospital, Dr. Bartlett said. Hospital-acquired MRSA generally has other resistance factors that make it resistant to trimethoprim/sulfamethoxazole, doxycycline, clindamycin, rifampin, and the quinolones.
Community-acquired MRSA tends to be susceptible to those agents, but it often has genes for encoding Panton-Valentine leukocidin, which is the presumed virulence factor for its necrotizing ability.
Leukocidin pulls in monocytes and macrophages and then lyses them, releasing cytokines.
“People have called this fatal attraction,” Dr. Bartlett said.
Because the four necrotizing pneumonia patients had such bad outcomes despite treatment with antibiotics to which the organisms should have been susceptible, “I almost have the feeling we are going to have to do something different in these cases, such as [intravenous immunoglobulin],” he said.
“I'd like to tell you how to treat these, but I really don't know,” Dr. Bartlett added.