In vitro evaluation of antibiotics' combinations for empirical therapy of suspected methicillin resistant Staphylococcus aureus severe respiratory infections

<p>Abstract</p> <p>Background</p> <p>Methicillin resistant <it>Staphylococcus aureus </it>(MRSA) is an increasingly common cause of nosocomial infections, causing severe morbidity and mortality worldwide, and accounting in some hospitals for more than 50% of all <it>S. aureus </it>diseases. Treatment of infections caused by resistant bacterial pathogens mainly relies on two therapeutic modalities: development of new antimicrobials and use of combinations of available antibiotics.</p> <p>Combinations of antibiotics used in the empiric treatment of infections with suspected methicillin resistant <it>Staphylococcus aureus </it>etiology were investigated.</p> <p>Methods</p> <p>Double (vancomycin or teicoplanin with either levofloxacin or cefotaxime) and triple (vancomycin or teicoplanin + levofloxacin + one among amikacin, ceftazidime, cefepime, imipenem, piperacillin/tazobactam) combinations were evaluated by means of checkerboard assay and time kill curves. Mutational rates of single and combined drugs at antimicrobial concentrations equal to the resistance breakpoints were also calculated.</p> <p>Results</p> <p>Vancomycin or teicoplanin + levofloxacin showed synergy in 16/50 and in 9/50 strains respectively, while vancomycin or teicoplanin + cefotaxime resulted synergic for 43/50 and 23/50 strains, respectively. Triple combinations, involving teicoplanin, levofloxacin and ceftazidime or piperacillin/tazobactam gave synergy in 20/25 strains. Teicoplanin + levofloxacin gave synergy in triple combinations more frequently than vancomycin + levofloxacin.</p> <p>For single antibiotics, mutational frequencies ranged between 10^-5and <10^-9for levofloxacin, cefotaxime, amikacin and imipenem, and <10^-9for vancomycin and teicoplanin. When tested in combinations, mutational frequencies fell below 10^-9for all the combinations.</p> <p>Conclusion</p> <p><it>In vitro </it>evidence of synergy between glycopeptides, fluoroquinolones (levofloxacin) and β-lactams and of reduction of mutational frequencies by combinations are suggestive for a potential role in empirical therapy of severe pneumonia with suspected MRSA etiology.</p

March 2016 pulmonary case of the month

No abstract available. Article truncated after first page. History of Present Illness: A 74-year-old man was referred for a recently identified right pleural effusion and dyspnea on exertion. Past Medical History, Family History and Social History: He has a history of anemia, hypertension, and prostate cancer with a prostatectomy in 2015. He is a life-long nonsmoker and has no occupational exposures. Family history is noncontributory. Physical Examination: He had diminished breath sounds at the right lung base and a palpable spleen. Otherwise the physical examination was unremarkable. Laboratory: CBC: hemoglobin 8.5 g/dL, white blood count 7.7 X 109 cells/L, platelets 357 X 109 cells/L. Radiography: A chest X-ray showed a right pleural effusion. Representative images from the CT scan are shown in Figure 1. Which of the following is the most likely diagnosis? 1. Empyema; 2. Lung cancer; 3. Tuberculosis; 4. Usual interstitial pneumonia; 5. Valley fever (coccidioidomycosis). ..