Staphylococcus Aureus Pneumonia: Emergence of MRSA in the Community

Suzanne F. Bradley, MD

Disclosures

Semin Respir Crit Care Med. 2005;26(6):643-649. 

In This Article

Lessons from Staphylococcal Pneumonia: What was Old is New Again

The demography and clinical presentation of staphylococcal pneumonia have continuously changed since its initial description in the late 19th and early 20th centuries. In young, healthy military personnel during World War I, vivid descriptions of postinfluenza staphylococcal pneumonia included "dirty salmon-pink anchovy sauce" purulent sputum, lack of signs of consolidation, and inflammation followed by "cherry-red indigo-blue cyanosis" and a progression to death so rapid that the patients were frequently unaware of its approach.[19] Others described remitting fever, tachypnea out of proportion with clinical findings, pleuritic chest pain, and normal chest roentgenographic findings in the first 24 to 48 hours.[20] In those patients, autopsy findings frequently revealed hemorrhage and microabscess formation. If the patient survived 4 to 5 days, clinical findings of bronchopneumonia ensued, microabscesses coalesced into cavitary lesions, and pneumatoceles, empyemas, bronchopleural fistulae, pyopneumothoraces, and pulmonary gangrene were found.[20,21] In the preantibiotic era, mortality rates approached 80 to 90%.[13,19,20]

In the 1950s, sporadic cases of staphylococcal pneumonia were increasingly described in very young infants < 6 months and among adults without prior influenza infection. These adults typically had predisposing cardiopulmonary disease, alcoholism, or diabetes and acquired their infection primarily in hospital. The clinical presentation was often more insidious and less explosive than previously described.[13,20,22,23,24] In that postantibiotic era, mortality rates ranged from 12 to 15% in children, 20% in young adults, 30 to 50% postinfluenza, and 84% in patients with bacteremic primary pneumonia.[13,14,23,25]

It was also noted that not all patients with staphylococcal pneumonia had primary infection following inhalation or aspiration. Some patients developed secondary staphylococcal infection of the respiratory tract following hematogenous dissemination from another site such as SSTI or as a consequence of right-sided endocarditis.[20,26,27,28] These secondary staphylococcal pneumonia cases were also less severe than primary pneumonia cases associated with influenza.

Has the emergence of HA-MRSA altered the epidemiology and clinical presentation of staphylococcal pneumonia? Studies that have compared the clinical presentation and outcome of HA-MRSA pneumonia versus MSSA cases have been infrequent.[29,30,31,32] In one series of ventilator-associated pneumonia (VAP), patients with MRSA were more likely to have bacteremia and had greater mortality than patients with MSSA pneumonia.[32] However, a more recent study of bacteremic primary pneumonia found no differences in clinical presentation, radiological findings, or complications between the two organisms, even though MSSA patients were younger and had fewer predisposing illnesses.[31] So the increasing prevalence of HA-MRSA strains alone has not had a convincing impact on the changing demography and increased virulence seen in staphylococcal pneumonia.

Reports of severe necrotizing pneumonia due to CA-MRSA have been described in the United States and France.[10,33,34,35,36,37] Further characterization of some isolates confirmed the presence of SSCmecIV and the USA300 PFGE type.[10,11,33,34] Some of these respiratory infections have been associated with toxic shock, hemoptysis, respiratory failure, purpura fulminans, and recent influenza infection.[10,33,34,36,38,39,40] Despite the availability of antibiotics, the clinical presentation of these infections in young healthy patients is reminiscent of the infections seen in the early part of the 20th century. What has changed?

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