Is Serratia marcescens alpha or beta hemolytic?

Serratia marcescens is a gram-negative bacterium and often causes nosocomial infections. There have been few studies of the virulence factors of this bacterium. The only S. marcescens hemolytic and cytotoxic factor reported, thus far, is the hemolysin ShlA.

What type of hemolysis is S. marcescens?

S. marcescens produces two types of hemolysins: contact-dependent hemolysin and extracellular hemolysin [16]. The ShlA hemolysin has cytolytic and contact-dependent hemolytic activity, but little is known about the S. marcescens secreted hemolysin.

Does Serratia marcescens grow on blood agar?

Serratia marcescens. Medium-sized colonies that appear buff in colour on Blood Agar. The bacteria produce a red pigment which is easily seen when grown on blood-free media such as nutrient agar or Kings agar B. This culture has been incubated at 30°C.

What causes hemolysis on blood agar?

Hemolysis is the break down of the membrane of red blood cells by a bacterial protein known as hemolysin, which causes the release of hemoglobin from the red blood cell. Many types of bacterial posses hemolytic proteins. Alpha hemolysis is a greenish discoloration that surrounds a bacterial colony growing on the agar.

Does Serratia marcescens grow on EMB?

S. marcescens, which produces a red pigment, was grown on nutrient agar, a general purpose medium that supports the growth of a variety of bacteria. Eosin methylene blue agar (EMB) is a differential and selective media that supports the growth of gram-negative bacteria, including Escherichia coli and S. marcescens.

Can E coli grow on blood agar?

E coli is a gram-negative bacillus that grows well on commonly used media. It is lactose-fermenting and beta-hemolytic on blood agar.

Can S marcescens ferment lactose?

Serratia Species. Of the many species in the genus Serratia, Serratia marcescens is the one most commonly isolated from human infections and Serratia liquefaciens is occasionally grown. Serratia strains are motile, rarely ferment lactose, and produce an extracellular DNase.

How do Hemolysins destroy red blood cells?

Hemolysins or haemolysins are lipids and proteins that cause lysis of red blood cells by disrupting the cell membrane.

What are the symptoms of Serratia marcescens?

Symptoms may include fever, frequent urination, dysuria, pyuria, or pain upon urination. In 90% of cases, patients have a history of recent surgery or instrumentation of the urinary tract.

How is Serratia marcescens transmitted?

Transmission is by direct contact. Droplets of S. marcescens have been found growing on catheters, and in supposedly sterile solutions. Contaminated intravenous pain control fluids were the course of an outbreak of S.

How does the S.marcescens gene contribute to hemolysis?

We have shown that the S. marcescens phlA gene produces hemolysis on human blood agar plates. PhlA induces destabilization of target cell membranes in the presence of phospholipids. Our results indicated that the lysophospholipids produced by PhlA affected cell membranes resulting in hemolysis and cell death.

Where is the hemolytic activity of Serratia marcescens?

The hemolytic activity resided in the membrane fraction and could be inactivated by … A cell-bound hemolytic activity was found in several strains of Serratia marcescens. One Serratia cell per ten erythrocytes was sufficient to cause complete lysis of human erythrocytes within 2 h in the liquid assay.

Are there any cytolytic mutants of S.marcescens?

The only S. marcescens hemolytic and cytotoxic factor reported, thus far, is the hemolysin ShlA. An S. marcescens shlAB deletion mutant was constructed and shown to have no contact hemolytic activity.

Can a catheterized patient be infected with S.marcescens?

The risk of a catheterized patient becoming infected with S. marcescens has been directly related to the proximity of other catheterized patients colonized or infected with the organism ( 68 ).