Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Methicillin-resistant Staphylococcus aureus (MRSA) infection (pneumonia)
- Radiologic Findings
- Chest CT shows well demarcated, thin-walled cavities with marginal rim enhancement and nonenhancing low density materials in the whole lung fields. A few, thin-walled cysts in both apices may be nonspecific emphysema rather than pneumatoceles. Acute necrotizing pneumonia are mainly located in the both lower lobes. Right pneumothorax is resulted from outside thoracentesis in addition to probably ruptured parenchymal necrotic portion (bronchopleural fistula).
Underlying DM for 10 yr, insulin therapy, CRF ?HD for 2 yr, HPB.
Blood and urine culture: MRSA positive
No PCR or other DNA assay.
- Brief Review
- MRSA was first identified in the 1960s, reflecting the response of S aureus to widespread exposure to penicillins. Indeed, MRSA now accounts for 20%-40% of all hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP). Until recently, most of the MRSA strains causing health care-ssociated pneumonia (HCAP), HAP, and VAP were labeled hospital-acquired MRSA (HAMRSA) and contained the staphylococcal cassette chromosome (SCC) mec types I-III. Recently, however, a new variant of MRSA has emerged as a pulmonary pathogen. This new variant of S. aureus that causes pneumonia is community-acquired MRSA (CAMRSA), containing SCCmec type IV. CA-MRSA, although primarily a cause of skin and soft-tissue infection, has proved to be a formidable cause of pneumonia.
Overall, MRSA is an important cause of pneumonia. A survey of 59 US hospitals, involving 4543 patients with culture-positive pneumonia, between January 2002 and January 2004 identified MRSA as a potential pathogen in 8.9% of CAP cases, 26.5% of HCAP cases, 22.9% of HAP cases, and 14.6% of VAP cases.
Diagnosis is based on positive blood cultures accompany only 5%-15% of HAP cases and 24%-36% of VAP cases. Endotracheal microbiological sampling has shown only 40% agreement with lung biopsy, and only 15% of the samples met adequacy criteria for having originated from the lower respiratory tract.
The differentiation HRMRSA from CAMRSA is frequently difficult on clinical settings.
There're are a few reports about the MRSA imaging findings including acute necrotizing pneumonia with cystic changes, a lobar pneumonia, transition from the localized lobar pneumonia to a pattern of diffuse infiltrations consistent with the ARDS, multiple nodular cavities, and empyema. Empyema necessitatis is a rare complication of empyema.
- References
- 1. Ethan Rubinstein, Marin H. Kollef, Dilip Nathwani. Pneumonia Caused by Methicillin-Resistant Staphylococcus aureus. Clinical Infectious Diseases 2008;46:378-385
2. Kelly N. Mizell, Kimberley V. Patterson, and J. Elliot Carter. Empyema Necessitatis Due to Methicillin-Resistant Staphylococcus aureus: Case Report and Review of the Literature. Journal of clinical microbiology 2008;46(10):3534-3536
3. Scott T. Micek, PharmD; Michael Dunne, PhD; and Marin H. Kollef, MD, FCCP. Pleuropulmonary Complications of Panton-Valentine Leukocidin-Positive Community-Acquired Methicillin-Resistant Staphylococcus aureus Importance of Treatment With Antimicrobials Inhibiting Exotoxin Production. CHEST 2005; 128:2732-2738
4. Bartlett JG. Methicillin-Resistant Staphylococcus aureus infections. Top HIV Med.2008;16(5):151-155
5. Francis JS. Doherty MC. Lopatin U, et al. Severe Community-Onset Pneumonia in Healthy Adults Caused by Methicillin-Resistant Staphylococcus aureus Carrying the Panton-Valentine Leukocidin Genes. Clinical Infectious Diseases 2005;40:100-107
- Keywords
- Lung, Pleura, Infection, Bacterial infection,