Persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia due to a linezolid "tolerant" strain.

Persistent Staphylococcus aureus bacteremia is most frequently related to S. aureus acute bacterial endocarditis, myocardial abscess, extracardiac abscess, or a device-associated infection. Patients with continuous high-grade bacteremia who do not have acute bacterial endocarditis, an abscess, or a device-related infection should be considered to have antimicrobial "tolerance" as a possible cause. Antimicrobial "tolerance" is defined as a wide discrepancy between the minimal inhibitory concentration and the minimal bactericidal concentration of an isolate. Tolerance was first described in S. aureus and has since been described with streptococci and enterococci. Despite apparent in vitro susceptibility, infections caused by "tolerant" strains are not cured by appropriate antimicrobial therapy. The lack of bactericidal activity of the antibiotic becomes apparent when minimal bactericidal concentrations are determined for "tolerant" strains, and there is a great discrepancy between the minimal inhibitory concentration being used. Antibiotic tolerance to S. aureus has been described with a variety of antibiotics. To the best of our knowledge, this is the first case of continuous, high-grade methicillin-resistant S. aureus bacteremia due to a linezolid-tolerant strain.

E. faecalis vancomycin-sensitive enterococcal bacteremia unresponsive to a vancomycin tolerant strain successfully treated with high-dose daptomycin.

Enterococci are part of the normal flora of the gastrointestinal tract. Intra-abdominal and genitourinary enterococcal infections may be complicated by enterococcal bacteremia. Most strains of enterococci fecal flora in antibiotic-naive patients are E. faecalis. Because nearly all E. faecalis strains are sensitive to vancomycin, E. faecalis is synonymous with vancomycin-sensitive enterococci (VSE). E. faecium, which is nearly always vancomycin-resistant, is termed vancomycin-resistant enterococci (VRE). High-grade continuous enterococcal bacteremias may result in endocarditis. Persistent VSE and VRE bacteremias may be related to device-associated infections; intra-abdominal, pelvic, and/or renal abscesses; or enterococcal endocarditis. If these causes of persistent enterococcal bacteremia are eliminated, microbiologic and antimicrobial therapy-related causes for persistent bacteremia should be considered. We present a case of a male with a E. faecalis (VSE) bacteremia unresponsive to parenteral vancomycin therapy but sensitive to vancomycin in vitro (minimum inhibitory concentration [MIC] = 1 microg/mL). The patient was treated with high-dose daptomycin (12 mg/kg intravenously [IV] q 24 hours) empirically pending susceptibility testing. High-dose daptomycin therapy cleared the patient's E. faecalis bacteremia. Subsequently, it was determined that the strain of E. faecalis was "tolerant" of vancomycin (MIC = 1 microg/mL, MBC = >64 microg/mL). We believe this is the first case of enterococcal (VSE) bacteremia unresponsive to vancomycin tolerant strain of E. faecalis that responded to high-dose daptomycin (12 mg/kg IV q 24 hours) therapy.

Listeria monocytogenes encephalitis mimicking Herpes Simplex virus encephalitis: the differential diagnostic importance of cerebrospinal fluid lactic acid levels.

Listeria monocytogenes is a common cause of bacterial meningitis in elderly patients and in those with impaired cellular immunity. The most common central nervous system infection caused by L. monocytogenes is acute bacterial meningitis; meningoencephalitis is uncommon and encephalitis is rare. Early diagnosis of L. monocytogenes meningitis is difficult because only 50% of cerebrospinal fluid (CSF) Gram stains are negative. L. monocytogenes is one of the few central nervous system pathogens associated with red blood cells in the CSF. When L. monocytogenes presents as encephalitis with red blood cells in the CSF, the clinical presentation mimics most closely herpes simplex virus (HSV)-1 encephalitis. Because the therapies for L. monocytogenes and HSV-1 are different, early diagnostic differentiation is clinically important. The CSF lactic acid is the best way to rapidly differentiate between these two entities; the CSF lactic acid level is elevated in L. monocytogenes but is not elevated in HSV-1 encephalitis. The case presented is an elderly man with chronic lymphocytic leukemia who presented with encephalitis. Advanced age and chronic lymphocytic leukemia predispose him to a wide variety of pathogens, but the rapidity and severity of his clinical presentation made L. monocytogenes and HSV-1 encephalitis the most likely diagnostic possibilities. The CSF Gram stain was negative, but the elevated CSF lactic acid levels with encephalitis and red blood cells in the CSF indicated L. monocytogenes as the most likely pathogen. We present a case of L. monocytogenes encephalitis mimicking HSV-1 encephalitis. While receiving ampicillin therapy, the patient remained unresponsive for more than 1 week and then suddenly regained consciousness and recovered without neurologic sequelae.

Quadrivalvular marantic endocarditis (ME) mimicking acute bacterial endocarditis (ABE).

Marantic endocarditis (ME) is defined by noninfectious valvular vegetations. The most common disorders associated with ME are malignancy with or without hypercoagulable state, intercardiac instrumentation, residual vegetations from previously treated infective endocarditis (IE), renal insufficiency, and burns. Another important cause of ME is systemic lupus erythematosus when accompanied by vegetations, that is, Libman-Sacks endocarditis. ME should be differentiated from IE because they may present with similar clinical features. Both ME and IE may present with fever and a heart murmur with or without embolic phenomenon. Leukocytosis and elevated erythrocyte sedimentation rate suggest the diagnosis of IE. The hallmark of IE is a cardiac vegetation and continuous high-grade bacteremia. After exclusion of the causes of culture negative endocarditis, the absence of bacteremia clearly differentiates ME from IE. We present a case of ME mimicking acute bacterial endocarditis (ABE). The differential diagnostic features of ME versus IE are discussed. To the best of our knowledge, this is the first reported case of quadrivalvular ME with massive vegetations on all cardiac valves, as well as the aorta, atria, and pulmonary artery.

Herpes simplex virus (HSV) pneumonia in a heart transplant: diagnosis and therapy.

Organ transplants are frequently complicated by viral infections. The period of maximum immunosuppression, 1 to 6 months posttransplantation, predisposes one to intracellular pathogens. The most common intracellular viral pathogens in transplant recipients include cytomegalovirus (CMV), herpes simplex virus (HSV), and respiratory syncytial virus (RSV). Cytomegalovirus and HSV are common viral pathogens in the early transplant period (0-1 month posttransplant). Although respiratory syncytial virus commonly presents in the late posttransplant period (> or =6 months posttransplant), HSV pneumonia may be acquired in organ transplants by endogenous reactivation caused by immunosuppression or may be introduced from colonized oropharyngeal secretions into the lower respiratory tract during intubation in patients on ventilators. In ventilated patients without severe preexisting lung disease, HSV pneumonia presents with otherwise unexplained profound/prolonged hypoxemia or "failure to wean." As other viral pneumonias, HSV pneumonia is characterized by profound hypoxemia requiring a high FIo(2), and a highly increased A-a gradient (> or =30). These findings are indicative of an oxygen diffusion defect typical of noninfectious (eg, sarcoidosis) or infectious disorders (eg, HSV, cytomegalovirus, respiratory syncytial virus, Pneumocystis (carinii) jiroveci pneumonia) primarily affecting the interstitium of the lung. We present a case of HSV pneumonia in a heart transplant recipient and include a review of the clinical presentation, diagnostic findings, and therapy of HSV pneumonia.

Fever of unknown origin due to preleukemia/myelodysplastic syndrome: the diagnostic importance of monocytosis with elevated serum ferritin levels.

Fever of unknown origin (FUO) is a common clinical diagnostic dilemma. In the elderly, causes of FUO most commonly include malignancy or infection, and less commonly include collagen vascular diseases. Among the collagen vascular diseases causing FUO in the elderly, polymyalgia rheumatica/temporal arteritis, and adult Still's disease (adult juvenile rheumatoid arthritis) are difficult diagnoses to prove. Among the infectious causes of FUO in the elderly are subacute bacterial endocarditis, intra-abdominal abscesses, and extrapulmonary tuberculosis. In the elderly, neoplastic causes of FUO include lymphomas, hepatomas, renal cell carcinomas, and hepatic or central nervous system metastases. Acute leukemias, particularly during "blast" transformation, may present as acute fevers in the absence of infection, but are rare causes of FUO. Preleukemia/myelodysplastic syndromes are exceedingly rare causes of FUO. We present a case of an elderly man who presented with findings that initially suggested adult Still's disease. Prolonged and profound monocytosis provided the key clue to his subsequent diagnosis of preleukemia/myelodysplastic syndrome. In this patient, a positive Naprosyn test result also suggested a neoplastic cause for his FUO. After months of prolonged fevers, myelocytes/metamyelocytes were eventually demonstrated in his peripheral smear during hospital evaluation. These findings, in concert with the persistent monocytosis, highly elevated ferritin levels, polyclonal gammopathy on serum protein electrophoresis, and eventual presence of myelocytes/metamyelocytes on peripheral smear, prompted a bone marrow test that demonstrated blast cells confirming the diagnosis of preleukemia myelodysplastic syndrome as the cause of this patient's FUO.

Pacemaker-induced Staphylococcus aureus mitral valve acute bacterial endocarditis complicated by persistent bacteremia from a coronary stent: Cure with prolonged/high-dose daptomycin without toxicity.

Continuous high-grade Staphylococcus aureus bacteremia suggests acute bacterial endocarditis (ABE), a protected focus, ie, an abscess, or a device-related infection. Daptomycin was curative of S. aureus ABE and coronary stent-related bacteremia. Prolonged high-dose daptomycin therapy (12 mg/kg per day for 41 days) is not associated with any toxicity. Persistent S. aureus bacteremia in ABE should suggest myocardial or perivalvular abscess. If intracardiac abscess can be ruled out and there is no extracardiac source of the S. aureus bacteremia, then a device-related infection should be considered.