Serratia Marcescens

Morphology and culture

The genus Serratia belongs to the family Enterobacteriaceae. The most important for human medicine species Serratia marcescens, Serratia liquefaciens and Serratia rubidea. Serratia species occur in the soil, on plants and in water. In the healthy population, they can be other than Enterobacter and Klebsiella, only occasionally detected in the gastrointestinal tract or upper respiratory tract. The microorganisms are flagellated peritrisch. The cultivation in the laboratory is straightforward. The only Enterobacteriaceae kind they are to form the three enzymes DNAse, gelatinase and lipase capable. Citrate can be utilized as the sole carbon source. Hydrogen sulfide is not formed. Serratia rubidea and some strains of Serratia marcescens form without air a red dye (Prodigiosin).

Pathogenesis and clinical pictures

Serratia marcescens and Serratia liquefaciens are mainly cause of hospital-acquired infections. In immunocompromised patients, they can cause wound infections, infections of the kidney and urinary tract, respiratory tract infections and sepsis, endocarditis, meningitis, and prosthetic infections. Other Serratia species are much less common. As sources of infection, especially contaminated catheters and infusion solutions are also considered.

Serratia Marcescens diagnosis

The detection of microorganisms in the laboratory is straightforward. The differentiation from other Enterobacteriaceae species using the "Colorful row".

Serratia are naturally resistant to numerous penicillins and cephalosporins. In addition, there is a natural resistance to polymyxins. According to the Paul-Ehrlich Society for Chemotherapy about 10% of Serratia marcescens strains are resistant to cefotaxime (Claforan etc.), ceftriaxone (Rocephin, etc.) and piperacillin in combination with tazobactam (Tazobac) or sulbactam (PIPERACILLIN plus COMBACTAM ). The prevalence of resistance among aminoglycosides (0-3%), carbapenems (<1-3%), fluoroquinolones (3-6%) and cotrimoxazole (7%) is also low.

Serratia Marcescens therapy

The oral treatment of mild to moderate infections can be done with trimethoprim / sulfonamide [cotrimoxazole (div. Trade name)] or a fluoroquinolone. For the treatment of serious infections are primarily offer the fluoroquinolones [Ciprofloxacin (Cipro, etc.), levofloxacin (Tavanic etc.)] and carbapenems [ertapenem (ertapenem sodium), imipenem (ZIENAM u.a.), meropenem (MERONEM)] on.

The aminoglycosides used only as a combination partners into consideration. Monotherapy with a cephalosporin group 3 [cefotaxime, ceftriaxone, ceftazidime (FORTUM etc.)] or piperacillin / beta-lactamase inhibitor may also by demonstrating in vitro sensitivity lead to treatment failure because of the therapy-resistant mutants can be selected, constitutively produce large amounts of lactamase.