![]() aureus is the source of iron required for growth of the organism. Hemolysis of red cells by hemolysins produced by S. aureus usually ferments mannitol and hemolyzes red blood cells, whereas S. Two other characteristics further distinguish these species, namely, S. epidermidis is significantly less than that of S. epidermidis does not synthesize this pigment and produces white colonies. This pigment enhances the pathogenicity of the organism by inactivating the microbicidal effect of superoxides and other reactive oxygen species within neutrophils. aureus produces a carotenoid pigment called staphyloxanthin, which imparts a golden color to its colonies. ![]() ( Used with permission from Professor Shirley Lowe, University of California, San Francisco School of Medicine.) Arrow points to clotted plasma formed by coagulase produced by S. It is the most common cause of bacterial conjunctivitis.įIGURE 15–6 Coagulase test-Upper tube inoculated with Staphylococcus aureus lower tube inoculated with Staphylococcus epidermidis. It is an important cause of skin infections, such as folliculitis ( Figure 15–3), cellulitis, and impetigo ( Figure 15–4). It is one of the most common causes of hospital-acquired pneumonia, septicemia, and surgical-wound infections. Staphylococcus aureus causes abscesses ( Figure 15–1), various pyogenic infections (e.g., endocarditis, septic arthritis, and osteomyelitis), food poisoning, scalded skin syndrome ( Figure 15–2), and toxic shock syndrome. (2) Biochemically, staphylococci produce catalase (i.e., they degrade hydrogen peroxide), whereas streptococci do not. (1) Microscopically, staphylococci appear in grapelike clusters, whereas streptococci are in chains. Staphylococci and streptococci are nonmotile and do not form spores.īoth staphylococci and streptococci are gram-positive cocci, but they are distinguished by two main criteria: Two of the most important human pathogens, Staphylococcus aureus and Streptococcus pyogenes, are described in this chapter. As a result of high rates of resistance in currently recommended therapy and prophylaxis, the choice of optimal antibiotic therapy is vital in the individual patient.There are two medically important genera of gram-positive cocci: Staphylococcus and Streptococcus. GPC were the most frequent bacteria in culture-positive SBP and a variety of drug-resistant microorganisms have emerged. Third-generation cephalosporin resistance was observed in 49% and quinolone resistance in 47%. More infections with GNB than GPC were healthcare-associated (81% vs 42%, P = 0.007). MDR bacteria were more frequently isolated in healthcare-associated than in community-acquired infections (100% vs 50%, P = 0.006), in patients receiving long-term quinolone prophylaxis (67% vs 24%, P = 0.013) and in those with advanced liver disease as suggested by higher MELD score (28 vs 19, P = 0.012). coli ( n = 3) and Pseudomonas aeruginosa ( n = 2). pneumonia ( n = 4), followed by extended-spectrum beta-lactamase-producing E. Nine of the isolated bacteria (19%) were MDR, including carbapenemase-producing K. The most prevalent organisms in a descending order were Streptococcus spp ( n = 10), Enterococcus spp ( n = 9), Escherichia coli ( n = 8), Klebsiella pneumonia ( n = 5), methicillin-sensitive Staphylococcus aureus ( n = 4) and coagulase-negative Staphylococcus spp ( n = 3). GPC were found to be the most frequent cause (55%). Twenty-eight (60%) patients had healthcare-associated infections while 15 (32%) received prophylactic quinolone treatment. We retrospectively recorded 47 cases (66% males) during a 4-year-period (2008–2011). To assess possible recent changes of the bacteria causing SBP in cirrhotic patients. Recently, an increasing rate of infections with Gram-positive cocci (GPC) and multidrug-resistant (MDR) microorganisms was demonstrated. Spontaneous bacterial peritonitis (SBP) is historically caused by Gram-negative bacteria (GNB) almost exclusively Enterobacteriaceae.
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