Hemolysis (from Greek αιμόλυση, meaning 'blood breakdown') is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on

blood agar An agar plate is a Petri dish that contains a growth medium solidified with agar, used to culture microorganisms. Sometimes selective compounds are added to influence growth, such as antibiotics. Individual microorganisms placed on the plate w ...

is used to classify certain

microorganisms A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

. This is particularly useful in classifying streptococcal species. A substance that causes hemolysis is a ''

hemolysin Hemolysins or haemolysins are lipids and proteins that cause lysis of red blood cells by disrupting the cell membrane. Although the lytic activity of some microbe-derived hemolysins on red blood cells may be of great importance for nutrient acqu ...

''.

Types

Alpha-hemolysis

When alpha-hemolysis (α-hemolysis) is present, the agar under the colony is light and greenish. ''

Streptococcus pneumoniae ''Streptococcus pneumoniae'', or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic (under aerobic conditions) or beta-hemolytic (under anaerobic conditions), aerotolerant anaerobic member of the genus Streptococcus. They a ...

'' and a group of oral streptococci ( ''Streptococcus'' viridans or viridans streptococci) display alpha hemolysis. This is sometimes called ''green hemolysis'' because of the color change in the agar. Other synonymous terms are ''incomplete hemolysis'' and ''partial hemolysis''. Alpha hemolysis is caused by hydrogen peroxide produced by the bacterium, oxidizing

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...

producing the green oxidized derivative

methemoglobin Methemoglobin (British: methaemoglobin) (pronounced "met-hemoglobin") is a hemoglobin ''in the form of metalloprotein'', in which the iron in the heme group is in the Fe3+ (ferric) state, not the Fe2+ (ferrous) of normal hemoglobin. Sometimes, it ...

Beta-hemolysis

Beta-hemolysis (β-hemolysis), sometimes called ''complete hemolysis'', is a complete lysis of red cells in the media around and under the colonies: the area appears lightened (yellow) and transparent. Streptolysin, an exotoxin, is the enzyme produced by the bacteria which causes the complete lysis of red blood cells. There are two types of streptolysin: Streptolysin O (SLO) and streptolysin S (SLS). Streptolysin O is an oxygen-sensitive cytotoxin, secreted by most Group A streptococcus (GAS) and ''

Streptococcus dysgalactiae ''Streptococcus dysgalactiae'' is a gram positive, beta-haemolytic, coccal bacterium belonging to the family '' Streptococcaceae''. It is capable of infecting both humans and animals, but is most frequently encountered as a commensal of the ali ...

'', and interacts with cholesterol in the membrane of eukaryotic cells (mainly red and white blood cells, macrophages, and platelets), and usually results in β-hemolysis under the surface of blood agar. Streptolysin S is an oxygen-stable cytotoxin also produced by most GAS strains which results in clearing on the surface of blood agar. SLS affects immune cells, including polymorphonuclear leukocytes and lymphocytes, and is thought to prevent the host immune system from clearing infection. ''

Streptococcus pyogenes ''Streptococcus pyogenes'' is a species of Gram-positive, aerotolerant bacteria in the genus '' Streptococcus''. These bacteria are extracellular, and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They ...

'', or Group A beta-hemolytic Strep (GAS), displays beta hemolysis. Some weakly beta-hemolytic species cause intense beta hemolysis when grown together with a strain of ''

Staphylococcus ''Staphylococcus'' is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillales. Under the microscope, they appear spherical ( cocci), and form in grape-like clusters. ''Staphylococcus'' species are faculta ...

''. This is called the '' CAMP test''.The CAMP test is so called from the initials of those who initially described it, R. Christie, N. E. Atkins, and E. Munch-Peterson. It distinguishes ''Streptococcus agalactiae'' from the others. ''

Streptococcus agalactiae ''Streptococcus agalactiae'' (also known as group B streptococcus or GBS) is a gram-positive coccus (round bacterium) with a tendency to form chains (as reflected by the genus name '' Streptococcus''). It is a beta- hemolytic, catalase-negat ...

'' displays this property. ''

Clostridium perfringens ''Clostridium perfringens'' (formerly known as ''C. welchii'', or ''Bacillus welchii'') is a Gram-positive, rod-shaped, anaerobic, spore-forming pathogenic bacterium of the genus ''Clostridium''. ''C. perfringens'' is ever-present in nature a ...

'' can be identified presumptively with this test. ''

Listeria monocytogenes ''Listeria monocytogenes'' is the species of pathogenic bacteria that causes the infection listeriosis. It is a facultative anaerobic bacterium, capable of surviving in the presence or absence of oxygen. It can grow and reproduce inside the hos ...

'' is also positive on sheep's blood agar.

Gamma-hemolysis

If an organism does not induce hemolysis, the agar under and around the colony is unchanged, and the organism is called ''non-hemolytic'' or said to display gamma-hemolysis (γ-hemolysis). '' Enterococcus faecalis'' (formerly called "Group D Strep"), '' Staphylococcus saprophyticus'', and ''

Staphylococcus epidermidis ''Staphylococcus epidermidis'' is a Gram-positive bacterium, and one of over 40 species belonging to the genus ''Staphylococcus''. It is part of the normal human microbiota, typically the skin microbiota, and less commonly the mucosal microbiot ...

'' display gamma hemolysis.

Hemedigestion

This is the nonspecific killing of blood cells by metabolic by-products of bacteria. This can be seen on a blood agar plate, when the blood surrounding the confluent part of your streak turns green, but there is no change around single colonies. Hemedigestion is seen with the cholera-causing bacteria, ''

Vibrio cholerae ''Vibrio cholerae'' is a species of Gram-negative, facultative anaerobe and comma-shaped bacteria. The bacteria naturally live in brackish or saltwater where they attach themselves easily to the chitin-containing shells of crabs, shrimps, and o ...

''.

Notes

References

* *Kato, Gregory J.; Steinberg, Martin H.; Gladwin, Mark T. (2017-03-01). "Intravascular hemolysis and the pathophysiology of sickle cell disease". ''Journal of Clinical Investigation''. 127 (3): 750–760. doi:10.1172/JCI89741.

ISSN An International Standard Serial Number (ISSN) is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSNs a ...

0021-9738. {{Clinical microbiology techniques Blood Microbiology terms