Staphylococcus aureus is a bacterial pathogen that is believed to be the most common agent of human infectious disease, causing conditions ranging from common skin lesions to life-threatening illnesses. S. aureus has also shown a remarkable ability to develop resistance to antimicrobial treatment, making infections difficult to treat. In the post-genomic era, proteomic studies analyzing the protein complement of a genome in a particular organism at any given time, have gained real significance. This result is largely due to dynamic changes in protein expression profiles which can lead wide alterations in physiology and behavior. For proteomics, it is necessary to maximize protein concentration and to devise a method that can be easily employed and provide reproducible results. Most proteomic studies of S. aureus involve 2D gel electrophoresis (2-DE); however, 2-DE has many drawbacks. Proteins that are too large, hydrophobic, acidic, or basic are poorly resolved. Multi-dimensional protein identification (MudPIT) allows complex protein samples to be analyzed in solution. As yet, there has not been a study involving solely 2D liquid chromatography followed by mass spectrometric analysis in S. aureus ; therefore we sought to catalogue the intracellular proteome and secretome of a commonly used and well-studied lab strain, SH1000. This was conducted during post-exponential and stationary phases of growth so as to understand its adaptation over time by utilizing differential protein synthesis. We found cytoplasmic proteins involved in glycolysis to be highly expressed in post-exponential phase while proteins involved in tricarboxylic acid cycle to be prevalent in stationary phase. We also found production of agr-regulated secreted toxins and proteases to be upregulated in stationary phase. In addition to this we employed proteomic approaches to quantitatively profile the secretomes of leading clinical isolates of S. aureus, as such a study is currently lacking. These included the two most common hospital-associated S. aureus strains (USA100 and USA200), and the two most common community-associated S. aureus strains (USA300 and USA400). We found agr-regulated proteins are generally upregulated in CA-MRSA strains USA300 and USA400 and surface-associated proteins to be upregulated in HA-MRSA strains USA100 and USA200. This finding concurs with literature regarding transcriptomic studies showing a hyperactive agr in CA-MRSA strains compared to HA-MRSA strains.

Methicillin-resistant Staphylococcus aureus (MRSA) is a serious public health problem nationwide, threatening to develop into an epidemic. Many of these patients are presenting to their primary care clinics with skin and soft tissue infections (SSTIs). The CDC has reported that in 2005, MRSA was responsible for an estimated 94,000 life-threatening infections and 16,650 deaths. The purpose of this study is to estimate the incidence of CA-MRSA within a specific family practice in Florida and to identify epidemiologic factors, classify antibiotic susceptibility patterns, and evaluate patient education in regard to disease management and prevention. This study was a descriptive, epidemiologic, three-year retrospective medical record review of all wound cultured skin and soft tissue infections that presented to a family practice between January 2007 and December 2009. Sixty-two medical records met the inclusion and exclusion criteria for the study. Of these 62 SSTIs, 44 cultures grew one or more bacterial organisms. The incidence of CA-MRSA was 66% (n=29). The mean age of those with CA-MRSA was 40 years old, with a range from 7 to 90 years old. Sixty-two percent (n=18) were male and 38% (n=11) were female; additionally 69% (n=20) lived within a 10 mile radius from the family practice, while 31% (n=9) lived in a surrounding suburb. The most frequent race was Caucasian 83% (n=24), with African American at 10% (n=3) and Hispanics 7% (n=2). Risk factors associated with CA-MRSA was obesity 41% (n=10), diabetes mellitus 24% (n=7), and a previous history of MRSA infection 24% (n=7). Skin and soft tissue infections were diagnosed as either an abscess 62% (n=18), boil 24% (n=7), pustule 10% (n=3), or cellulitis 4% (n=1). CA-MRSA isolates were susceptible to trimethoprim-sulfamethoxazole 100% (n=29), doxycycline 93% (n=27), and rifampin 100% (n=14). Clindamycin susceptibility was 65% (n=15) with resistance at 30% (n=7) and 5% (n=1) intermediate. Both cephalexin and erythromycin were 100% resistant. Documentation in the medical record on wound care was found in 45% (n=13) of the records. The incidence of CA-MRSA SSTI was 66%, which identifies this suburban community at high risk for this bacterial infection. Risk factors associated with CA-MRSA included obesity (BMI > 30), history of previous MRSA infection, and diabetes mellitus. There were no clinical characteristics that helped distinguish MRSA infection from other bacterial SSTIs. Most SSTI were treated with incision and drainage and a susceptible antibiotic. Judicious use of antibiotics not only provides appropriate treatment, but is also critical in prevention of antibiotic resistance. Lastly, patient education in adequate hygiene is essential in preventing the spread of CA-MRSA

Methicillin-resistenta Staphylococcus aureus (MRSA) som bär på genen mecA, har förekommit och spridit sig över hela världen, främst i sjukhusmiljö, och orsakat utbrott av vårdrelaterade (så kallade nosokomiala) infektioner. Dessa infektioner kan inte behandlas med stafylokock-penicilliner och MRSA-bakterierna är ofta resistenta även mot flera andra grupper av antibiotika vilket medför att infektionerna ofta är påtagligt svårbehandlade. Under senare år har emellertid allt fler fall beskrivits av samhällsförvärvad MRSA infektion, det vill säga uppträdande av MRSA hos personer som tidigare ej har haft kontakt med sjukhusvård eller behandlats med antibiotika. Det har länge varit oklart om de samhällsförvärvade MRSA [community-acquired (CA-MRSA)] representerar spridning av bakterier från sjukhusmiljön ut till samhället eller om dessa MRSA är spontant uppträdande. Många av dessa stammar har dessutom visat sig bära på sjukdomsrelaterade gener som vanligen inte återfinns hos S. aureus, t.ex. Panton Valentine leukocidin (PVL) som associeras med hudinfektioner och allvarlig lunginflammation med hög dödlighet hos unga och annars friska individer. Denna avhandling beskriver den molekylära epidemiologin hos MRSA med fokus på samhällsförvärvade MRSA som utgjorde mer än hälften av samtliga fall av MRSA i Örebro län och som dessutom ofta producerade PVL toxinet, vars funktion vidare analyserades i detalj. Undersökning av ursprung och släktskap hos samtliga MRSA som isolerats i Örebro län, samt karaktärisering av det genetiskt element som kallas staphylococcal cassette chromosome mec (SCCmec) vilket innehåller genen mecA och ibland även andra resistensgener, visade att CA-MRSA inte är relaterade till de nosokomiala MRSA, och att dessa har uppstått oberoende av varandra. Flertalet MRSA visade sig dessutom bära på SCCmec, och resistensmekanismer, som tidigare inte beskrivits. Troligen har dessa MRSA uppstått genom ett genetiskt utbyte av SCCmec mellan methicillin-resistenta koagulas-negativa stafylokocker (MR-KNS), som utgör huvudparten av normalfloran på huden, och methicillin-känsliga S. aureus som därvid erhåller genen mecA och resistensmekanismer mot samtliga stafylokockantibiotika. I den här avhandlingen framläggs bevis för att ett sådant genetiskt utbyte har skett på Barnkliniken på Universitetssjukhuset i Örebro i slutet på 1990-talet, vilket resulterade i uppkomsten av en ny klon av MRSA som därefter orsakade ett allvarligt utbrott. Kartläggning av DNA-sekvensen hos flertalet unika SCCmec från svenska MRSA gav dessutom en bättre förståelse för hur resistens uppkommer och sprider sig, samt mekanismerna bakom detta. Dessa nya kunskaper kan bidra till en förbättrad diagnostik av MRSA. Detta är framför allt av stor betydelse eftersom nya effektiva kloner av MRSA verkar kunna uppstå ute i samhället med potential att orsaka svårbehandlade infektioner men även att sprida sig bland den friska befolkningen. / Material and methods - During a period of 14 years, around 2000 patients with head injuries were admitted to the emergency ward at Lindesberg County Hospital and Örebro Medical Centre Hospital. Six hundred subjects suffered from skull fracture and/or brain contusion and diagnosis was established using a computed tomography scan (CT). The degree of initial brain injury was estimated using the Swedish Reaction Level Scale (RLS). Sixty-six subjects were investigated with pure tone audiometry in close proximity to the trauma, and this gave an opportunity to study the issue of progress. The investigation took place two to 14 years after trauma, and the results were compared to matched control groups. A battery of different audiological methods was used to investigate peripheral and central auditory function, and a specially designed acoustic environmental room was also utilized. Cognition was investigated using a computer-based test-battery, text information process system (TIPS). Self-assessed hearing, cognition and quality of life were explored using different questionnaires. Results - A high percentage of peripheral and central auditory impairments and also cognitive shortcomings were demonstrated. Progress of SNHL was a common finding, and fracture, high age at trauma and large initial hearing loss predicted progress. Antibody-mediated autoimmunity as a mechanism behind posttraumatic progress of SNHL or clear evidence for sympathetic cochleolabyrinthitis could not be demonstrated. Binaural auditory deficits could be demonstrated when tested in a realistic acoustic environment. Tinnitus, vertigo and memory shortcomings proved to be common sequelae, even in a long-term perspectiveCognitive shortcomings were found in several of these well-rehabilitated subjects.On a group level, there was a good correlation between self-assessments and audiometric results, even if some individuals had a tendency to over- or underestimate their abilities. Conclusion - Auditory and cognitive long-term sequelae of CHI are a common finding even in well-rehabilitated and socially well-functioning subjects, as are vertigo and tinnitus. Vertigo and tinnitus are also common sequelae after CHI, therefore a basic audiovestibular investigation after CHI is recommended, at least in selected cases.Early awareness of the risk for hearing and cognitive sequelae after CHI could lead to measurements taken to prevent tension-related symptoms.Early detection of HI offers an opportunity to try immunosuppressive treatment in cases with a large initial SNHL.