Effect of linezolid alone and in Combination with other antibiotics, on methicillin-resistant staphylococcus aureus

The prevalence of methicillin-resistant Staphyloccoccus aureus [MRSA] strains has presented a new challenge in antimicrobial medication. Linezolid is a new drug with potent activity on Grampositive pathogens such as MRSA. The aim of the study was to investigate the in vitro activity of linezolid alone and in combination with imipenem, vancomycin or rifampicin to determine the most active therapy against MRSA strains. Twenty clinical MRSA strains were isolated from patients admitted to inpatient departments and outpatient clinics of Theodor Bilharz Research Institute. Standard strain MRSA ATCC 43300 was included as a control. The MICs of MRSA strains to linezolid, vancomycin, imipenem and rifampicin were evaluated using E test. Time-kill curve were used to assess the in vitro activity of linezolid [at 8x MIC] alone and in combination with imipenem [at 32x MIC], vancomycin or rifampicin [at 8x MIC]. Scanning and transmission electron microscopy were performed to compare bacterial morphological alterations owing to the different combinations. Time-kill studies showed synergistic effect when linezolid combined with imipenem was tested against all the MRSA strains. Linezolid plus vancomycin or rifampicin combinations did not display any synergism or antagonism. Scanning and transmission electron microscopy observations confirmed the interactions observed in time kill experiments. Linezolid in combination with subinhibitory concentrations of imipenem can be bactericidal against MRSA strains and appears to be a promising combination for the treatment of MRSA infections. No synergistic activity was seen when the linezolid and vancomycin or rifampicin were combined. Linezolid could prevent the emergence of mutants resistant to rifampicin

Herpes simplex virus CNS infections in infants and children

Abstract: Meningitis and encephalitis are potentially life threatening infections especially in children. Virtually any infectious agent can cause CNS infection. Morbidity and mortality depend on the infectious agent, age of the child, general health, and prompt diagnosis and treatment. Viral meningitis and encephalitis occur as uncommon complications of systemic viral infection that occurs most frequently in infants and children. Herpes simplex virus [HSV] is the most common cause of sporadic focal CNS disease and because an effective therapy for treatment of HSV-CNS infection has become available, early diagnosis of this condition has a very important role in the clinical management and reduction of the morbidity and mortality rates

Aim of work: This work aims to determine the prevalence of HSV meningitis among cases of aseptic meningitis [AM] referred to Imbaba Fever Hospital and to evaluate the performance of ELISA tests which detect HSV antibodies, in comparison to PCR techniques, which detect viral DNA in CSF of patients

Patients and Methods: Sixty four CSF samples were obtained from patients aging from 1 day to 10 years, attending Imbaba Fever Hospital, with clinical and laboratory data suggestive of aseptic meningitis [AM]. Fifteen normal age and sex matched infants and children with normal CSF cells, protein and glucose, and with no clinical evidence of CNS infection, were chosen as control group [their definite diagnosis was non infectious CNS diseases]. All patients and control groups were subjected to microscopic examination and chemical analysis of CSF, serological assays for anti-HSV antibodies [IgG and IgM] and molecular assays for HSV-DNA in CSF

Results: The present work revealed that, 13 cases out of 64 [20%] were HSV-PCR positive, 25 cases [39%] were HSV-IgG positive, and 10 cases [16%] were HSV-IgM positive. Out of the 13 HSV-PCR positive cases, 4 cases [31%] were HSV-IgM positive only, 2 cases [15%] were both HSV-IgG and IgM positive, and 5 cases were negative by both types of HSV ELISA. Fifty one cases out of 64 [80%] were HSV PCR negative, defining a group of patients with aseptic meningitis for other causes

Conclusion: It was apparent that ELISA was not sufficient for conclusive diagnosis of acute HSV CNS infection, because IgM antibodies are not unique to the primary phase of infection. Furthermore, IgG seroconversion needs well-timed collection of patient sera which is often impractical. Thus, a definite diagnosis of recent HSV-CNS infection may be hard to establish. PCR was found to be the most reliable, rapid, sensitive method for early diagnosis and subsequently timely management of acute HSV-CNS infection in infants and young children