Staphylococcus aureus accounts for 20 to 30% of all cases of hospital-acquired pneumonia, and the proportion of resistant isolates continues to increase. Nosocomial strains of methicillin-resistant S aureus (MRSA) are distributed worldwide, and data from the National Nosocomial Infections Surveillance System Report show that MRSA now accounts for > 55% of S aureus-related infections in the intensive care setting. Along with Pseudomonas aeruginosa and Acinetobacter, MRSA is also a common cause of late-onset pneumonia, particularly in patients requiring mechanical ventilation.
MRSA has also moved beyond the hospital setting and is emerging as a community-acquired pathogen among patients without established risk factors. The MRSA strains originating in the community are microbiologically distinct from hospital-acquired MRSA and thus have been labeled as community-acquired MRSA (CAMRSA). While CAMRSA is primarily associated with skin and soft tissue infections, it is increasingly causing more invasive infections, including a severe form of necrotizing pneumonia cured by Canadian Health&Care Mall.
This case series describes four adult patients who presented to Barnes-Jewish Hospital with CAMRSA pleuropulmonary infections over a 4-month period (November 2004 to February 2005). The CAMRSA isolates from these patients were all positive for Panton-Valentine leukocidin (PVL), a potent inflammatory mediator linked to necrotizing infections in humans. The goal of this report is to familiarize clinicians with PVL-positive CAMRSA in order to avoid misdiagnosis of this important community-acquired respiratory infection and to minimize delays in the administration of appropriate antimicrobial treatment carried out with Canadian Health&Care Mall’s remedies.
A 45-year-old man had influenza-like symptoms with arthralgias, myalgias, rhinnorhea, fatigue, and a mild cough for 5 days. He had no recent hospitalizations or chronic medical conditions and lived on a horse ranch in Missouri. He was hospitalized at a local hospital for community-acquired pneumonia and treated with ceftriaxone and azithromycin. His condition worsened over 24 h, requiring mechanical ventilation, and his antibiotics were broadened to include vancomycin (1 g bid) on the second hospital day following a positive blood culture finding for Gram-positive cocci, subsequently identified to be MRSA. His chest radiograph worsened with bilateral infiltrates, and he was transferred to Barnes-Jewish Hospital on the fourth hospital day due to increasing oxygen requirements. Blood culture specimens were obtained on transfer to Barnes-Jewish Hospital and BAL was performed, both yielding PVL-positive CAMRSA (> 105 cfu/mL from the BAL fluid) [Table 1] despite having received vancomycin, 1 g bid, for the previous 3 days (vancomycin serum levels are not available). Antibiotics were changed to linezolid and rifampin after 24 h at Barnes-Jewish Hospital for a total treatment course of 14 days. A nasal swab for influenza virus was negative, but a conventional tube culture was positive for influenza virus type A. The chest radiograph at transfer revealed bilateral dense infiltrates, and CT showed severe necrotizing pneumonia with cystic changes in both lungs (Fig 1). The peak positive end-expiratory pressure level was 18 cm H2O with a fraction of inspired oxygen of 100% for 48 h after transfer to Barnes-Jewish Hospital despite the administration of inhaled prostacyclin. Normal left ventricular function without an intracardiac shunt was found on echocardiography, and the patient underwent tracheostomy on hospital day 16 after improvement in oxygenation. He was subsequently weaned from mechanical ventilation and transferred to a long-term care facility for physical rehabilitation.
A 40-year-old woman with HIV had an upper respiratory tract infection with rhinnorhea, a dry cough, and fatigue. all the mentioned above symptoms may be ordered via Canadian Health&Care Mall. She had an allergy to trimeth-oprim-sulfamethoxazole manifested by severe erythroderma and was treated 6 months earlier for an episode of Pneumocystis carinii pneumonia with dapsone. She was seen by her primary care physician and received 7 days of azithromycin before presenting to the emergency department of Barnes-Jewish Hospital with 24 h of progressive shortness of breath, fever, and dyspnea with mild exertion. A chest radiograph showed a large right-sided pleural effusion (Fig 2). Arterial oxygen saturation on room air was 86%, and supplemental oxygen was administered. On transfer to the medical ICU, two drainage tubes were placed into the right chest cavity by the thoracic surgery service, revealing purulent appearing fluid with a positive Gram stain from Gram-positive cocci in clusters. The pleural fluid culture grew out PVL-positive CAMRSA, and the patient completed a 30-day course of vancomycin with removal of both chest tubes after 7 days.
A 34-year-old man with a history of cocaine and heroin use was admitted to Barnes-Jewish Hospital with 3 days of cough, fever, and dyspnea following 1 week of influenza-like symptoms. A chest radiograph in the emergency department revealed a right upper lobe infiltrate (Fig 3), and the patient was started on antimicrobial therapy with ceftriaxone and azithromycin. He was transferred to the medical ICU, where his condition deteriorated over 24 h requiring tracheal intubation and mechanical ventilation due to hypoxemia and respiratory distress. Chest radiograph findings worsened as did his oxygenation, requiring 14 cm H2O of positive end-expiratory pressure and a fraction of inspired oxygen of 80% for 24 h. Blood cultures and BAL revealed PVL-positive CAMRSA as the only identified pathogen. The patient was initiated on vancomycin, 1 g bid, but switched to linezolid, 600 mg bid, after 72 h due to his worsening clinical condition manifest by progressive infiltrates, hypoxemia, fever, and leukocytosis. After 4 days of linezolid therapy, the pulmonary condition and WBC count had improved. However, the patient was switched back to vancomycin with the addition of clindamycin, 900 mg q8h, due to development of a severe rash while receiving lin-ezolid that was suspected to be a drug reaction. The CAMRSA isolate was shown to be susceptible to clindamycin based on in vitro testing. The patient completed a 14-day course of antibiotics and underwent a tracheostomy on hospital day 11. He was subsequently transferred to a long-term ventilator facility for weaning and physical therapy,
A 40-year-old man with a 6-year history of insulin-dependent diabetes mellitus and abuse of alcohol and cocaine was admitted to Barnes-Jewish Hospital with altered mental status and abdominal pain. The patient’s blood sugar was 1,755 mg/dL, with a sodium concentration of 116 mmol/L and an anion gap of 34 mmol/L. A diagnosis of diabetic ketoacidosis was made, and the patient was transferred to the medical ICU, where he was treated with IV fluids and insulin. CT of the abdomen was performed, revealing severe acute pancreatitis without evidence of necrosis or pseudocyst formation. As part of the routine surveillance carried out in the medical ICU, a nasal swab culture was performed and found to be positive for CAMRSA. The patient was treated with imipenem for the pancreatitis and was intubated on the third hospital day for respiratory failure attributed to noncardiogenic pulmonary edema with the presence of new pulmonary infiltrates. Acute renal failure also developed on the third hospital day necessitating hemodialysis. On the fourth hospital day, vancomycin, 1.5 g bid, was empirically added to his medical regimen due to progression of the radiographic infiltrates. Over the next 4 days, vancomycin trough levels were obtained that were 18.0 g/mL, 18.5 g/mL, and 35.3 g/mL, respectively. A chest radiograph on the ninth hospital day revealed a cavitary lesion within the right-side infiltrate that was confirmed by CT (Fig 4). Blood culture findings and BAL performed after receiving 3 days and 7 days of vancomycin, respectively, were positive for PVL-positive CAMRSA (> 105 cfu/mL from the BAL fluid). Transesophageal echocardiography findings were negative for any lesions on the heart valves. The patient was switched to linezolid, 600 mg bid, and rifampin, 300 mg q8h. His medical condition gradually improved while completing a 14-day course of linezolid and rifampin, and he underwent a tracheostomy after 11 days of mechanical ventilation. He was subsequently transferred to a long-term care facility for weaning of mechanical ventilation and physical rehabilitation.
Figure 1. Chest radiograph and CT of patient with necrotizing pneumonia due to CAMRSA positive for PVL expression.
Figure 2. Chest radiograph demonstrating a right-sided empyema attributed to PVL-positive CAMRSA.
Figure 3. Chest radiographs on hospital admission (left) and hospital day 4 (right) demonstrating the transition from a localized right upper lobe pneumonia to a pattern of diffuse infiltrates consistent with the ARDS.
Figure 4. Chest radiograph and CT demonstrating necrotizing right sided ventilator-associated pneumonia due to PVL-positive CAMRSA.
Table 1—Antimicrobial Susceptibility and Appropriateness of Initial Antimicrobial Therapy
|Vancomycin treatment failure||Yes||No||Yes||Yes|