Twenty-five year epidemiology of invasive methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered at a burn center.

Over the past two decades, an epidemiologic emergence of methicillin-resistant Staphylococcus aureus (MRSA) infections has occurred from that of primarily hospital-associated to community-associated. This emergence change has involved MRSA of different pulsed-field types (PFT), with different virulence genes and antimicrobial resistance patterns. In this study we, evaluate the changes in PFT and antimicrobial resistance epidemiology of invasive MRSA isolates over 25 years at a single burn unit. Isolates were tested by pulsed-field gel electrophoresis (PFGE), broth microdilution antimicrobial susceptibility testing, and PCR for the virulence factors Panton-Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME), and the resistance marker staphylococcal chromosomal cassette mec (SCCmec). Forty isolates were screened, revealing stable vancomycin susceptibility MIC without changes over time but decreasing susceptibility to clindamycin and ciprofloxacin. The majority of PFGE types were MRSA USA800 carrying the SCCmec I element and USA100 carrying the SCCmec II element. No strains typically associated with community-associated MRSA, USA300 or USA400, were found. USA800 isolates were predominately found in the 1980s, USA600 isolates were primarily found in the 1990s, and USA100 isolates were found in the 2000s. The PVL gene was present in only one isolate, the sole USA500 isolate, from 1987. The virulence marker ACME was not detected in any of the isolates. Overall, a transition was found in hospital-associated MRSA isolates over the 25 years, but no introduction of community-associated MRSA isolates into this burn unit. Continued active surveillance and aggressive infection control strategies are recommended to prevent the spread of community-acquired MRSA to this burn unit.

Diminished vancomycin and daptomycin susceptibility during prolonged bacteremia with methicillin-resistant Staphylococcus aureus.

An elderly patient with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia was treated sequentially with vancomycin plus rifampin then daptomycin plus gentamicin. The MRSA strain developed diminished susceptibility to vancomycin (MIC increase and tolerance), daptomycin, and gentamicin, and resistance to rifampin during therapy.

Inhibitory activities of 11 antimicrobial agents and bactericidal activities of vancomycin and daptomycin against invasive methicillin-resistant Staphylococcus aureus isolates obtained from 1999 through 2006.

We assessed MICs and minimal bactericidal concentrations of vancomycin, daptomycin, and nine other antimicrobials against methicillin-resistant Staphylococcus aureus isolates obtained from 1999 through 2006. No vancomycin, daptomycin, or linezolid resistance was observed. Clindamycin, gentamicin, and ciprofloxacin resistance decreased significantly. No tolerance to vancomycin or daptomycin was observed, nor was MIC creep seen.

Evaluation of the patient with chronic cough.

Patients with chronic cough should avoid exposure to irritants that can trigger cough, and those who smoke should stop smoking. Patients who develop chronic cough in association with angiotensin-converting enzyme inhibitor therapy should be switched to an agent from another drug class. If cough persists, a chest radiograph should be ordered to rule out malignancy and other serious conditions. Postnasal drip syndrome, asthma, and gastroesophageal reflux disease are the most likely causes of chronic cough in adults. If postnasal drip syndrome is suspected, a trial of a decongestant and a first-generation antihistamine is warranted. Pulmonary function testing with a methacholine challenge is the preferred test for confirming the diagnosis of asthma. Gastroesophageal reflux disease usually is diagnosed based on the symptoms and after a trial of therapy. If the cause of chronic cough remains unclear, high-resolution computed tomographic scanning of the chest, bronchoscopy, and referral to a pulmonary specialist may be indicated. The approach to diagnosing chronic cough in immunocompromised patients and children is similar to the approach in immunocompetent adults. However, a CD4+ cell count can help determine the potential for opportunistic infections in immunocompromised patients. Respiratory tract infections, asthma, and gastroesophageal reflux disease are the most common causes of chronic cough in children. Foreign body aspiration should be considered in young children. Congenital conditions, cystic fibrosis, and immune disorders are possible diagnoses in children with chronic cough and recurrent infection.