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Two important factors indicate the need for caution when interpreting the results of comparative analyses of MRSA bacteremia and MSSA bacteremia.
The first problem concerns demographic differences. Patients with MRSA bacteremia are often older than those with MSSA bacteremia and are likely to have a longer hospital stay. They are also likely to have had a longer hospital stay and greater use of antibiotics before the development of bacteremia. The second problem is that, in all these analyses, the severity of the illness was not classified. When one compares mortality rates, accurate adjustment for severity of illness is desirable, if not necessary.
We investigated the outcome in critically ill patients with S. aureus bacteremia.4 In a retrospective study, we compared 35 cases of MSSA bacteremia with 40 cases of MRSA bacteremia. Adjustment for severity of illness was made on the basis of the Acute Physiology and Chronic Health Evaluation (APACHE II) score.5 Our results confirm those of the authors cited above. The in-hospital mortality rate in the group of patients with MRSA bacteremia was 65 percent, as compared with 25.7 percent in the MSSA group (P<0.001). Even after the patients had been matched for the APACHE II score (n=44), the mortality rate was twice as high among those with MRSA bacteremia (P<0.001). Logistic-regression analysis showed that methicillin resistance and an unfavorable APACHE II score were independent risk factors for death (P<0.001).
Stijn Blot, R.N., M.A.
Koenraad Vandewoude, M.D.
Francis Colardyn, M.D.
Universitair Ziekenhuis Gent
B-9000 Ghent, Belgium
References
Teicoplanin has some advantages over vancomycin.1 The toxicity profile of teicoplanin is more favorable, especially when it is used with other potentially toxic drugs, since nephrotoxicity and ototoxicity are relatively uncommon. Teicoplanin also has an advantage in terms of ease of administration. It can be given once daily, either intravenously or intramuscularly, and by rapid intravenous injection.1 With teicoplanin, there is no need for routine blood-level monitoring, making it easier to use outside the hospital.2 Moreover, teicoplanin and vancomycin have similar activity against S. aureus 3 and similar clinical efficacy.4 The combination of these factors makes teicoplanin an effective, safe alternative to vancomycin in the treatment of S. aureus infections.1,4
Alicia Conde, M.D., Ph.D.
Hospital El Sabinal
35017 Las Palmas, Spain
References
We conducted a retrospective case–control study in the department of infectious diseases of a 1700-bed university hospital in Rome. For the period from 1986 through 1997, we identified 350 episodes of bacterial pneumonia (as defined elsewhere2) and 28 episodes of S. aureus pneumonia. The attack rate for S. aureus pneumonia was 8.31 cases per 1000 HIV-related hospital admissions. S. aureus pneumonia was a community-acquired infection in two thirds of the HIV-positive patients, a finding at variance with the frequently reported finding that in immunocompetent patients, a nosocomial origin of S. aureus pneumonia is more common.
In conclusion, we emphasize the importance of S. aureus as an etiologic agent of life-threatening pulmonary infections in HIV-positive persons. Although other microorganisms can cause pneumonia, HIV-positive patients who have an acute onset with lobar involvement and pleural effusion on chest radiography should be carefully evaluated for the possibility of S. aureus pneumonia.
Evelina Tacconelli, M.D.
Mario Tumbarello, M.D.
Roberto Cauda, M.D.
Università Cattolica Sacro Cuore
00168 Rome, Italy
References
To the Editor: Blot et al. cite several studies suggesting that the outcome of infections caused by MRSA is worse than that of infections caused by MSSA. Other reports argue against the greater virulence of MRSA strains.1,2 As Blot et al. note, these studies must be interpreted cautiously, because of the frequent association of MRSA infections with a greater severity of illness, an underlying disease of a different nature, prolonged hospitalization, and increased antibiotic use. These variables make comparative analyses difficult, especially for retrospective studies. The virulence of staphylococcal infection may be more closely tied to particular strains than to the presence or absence of methicillin resistance.
As Dr. Conde suggests, teicoplanin was not mentioned because it is not available in the United States. Although it has some pharmacologic advantages, teicoplanin has been reported to have less antistaphylococcal activity than vancomycin, or at best, similar activity.3
Tacconelli et al. describe an important presentation of staphylococcal disease in HIV-positive patients. The incidence of staphylococcal disease in general appears to be increased in this population. There have also been reports of an increased incidence of bloodstream, skin, and soft-tissue infections, as well as respiratory tract infections.4,5 The basis of these infections is uncertain, but it may be related to the immunocompromised status of the patients, an increased colonization rate, and the use of more frequent invasive procedures that breach skin or mucosal barriers.
There is an error on page 520 of my article (first column, last paragraph, second line). The size of the chromosome should be 2.8 megabase pairs, not 2800 base pairs.
Franklin D. Lowy, M.D.
Montefiore Medical Center
Bronx, NY 10467
References
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