Hemolysis (microbiology)

Breakdown of red blood cells

Hemolyses of Streptococcus spp.
(left) α-hemolysis (S. mitis);
(middle) β-hemolysis (S. pyogenes);
(right) γ-hemolysis (non-hemolytic, S. salivarius)

Hemolysis is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on blood agar is used to classify certain microorganisms. This is particularly useful in classifying streptococcal species. A substance that causes hemolysis is called a hemolysin.

## Types

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### Alpha-hemolysis

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When alpha-hemolysis (α-hemolysis) is present, the agar under the colony is light and greenish. Streptococcus pneumoniae 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 the bacteria's production of hydrogen peroxide, which oxidizes hemoglobin and produces the green oxidized derivative methemoglobin.

### Beta-hemolysis

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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.[1] 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; it interacts with cholesterol in the membrane of eukaryotic cells (mainly red and white blood cells, macrophages, and platelets), usually resulting 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, or Group A beta-hemolytic Strep (GAS), as well as Streptococcus agalactiae display beta-hemolysis.

The hemolysis of some weakly beta-hemolytic organisms is enhanced when streaked close to certain beta hemolytic strains of Staphylococcus aureus. This phenomenon is the mechanism behind the CAMP test,[2] a test that was historically used for the identification of Streptococcus agalactiae and Listeria monocytogenes.[3] A modified version of this test called the reverse CAMP test, utilizing S. agalactiae instead of S. aureus, can also be used to identify Clostridium perfringens.

### Gamma-hemolysis

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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 display gamma-hemolysis.

## Hemodigestion

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When some otherwise non-hemolytic bacteria, such as strains of the cholera-causing bacteria Vibrio cholerae, are plated on blood agar, no clearings are observed surrounding isolated colonies, but the blood surrounding larger areas of growth turns green. This process, called hemodigestion, is caused by the metabolic by-products of the bacteria in aerobic conditions.[4]

## Notes

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1. ^ Ryan, Kenneth J.; Ray, C. George. "Chapter 25: Streptococci and Enterococci". Sherris Medical Microbiology, 6th ed. Access Medicine. Retrieved 16 August 2016.
2. ^ 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.
3. ^ Hanson, Anne (Oct 2006). "CAMP Test Protocols" (PDF). American Society for Microbiology. Retrieved 14 April 2024.
4. ^ Laboratory Methods for the Diagnosis of Vibrio cholerae (PDF). Center for Disease Control and Prevention. pp. 52–54. Retrieved 16 December 2023.52-54&rft.pub=Center+for+Disease+Control+and+Prevention&rft_id=https://www.cdc.gov/cholera/pdf/laboratory-methods-for-the-diagnosis-of-vibrio-cholerae-chapter-6.pdf&rfr_id=info:sid/en.wikipedia.org:Hemolysis+(microbiology)" class="Z3988">

## References

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* Ray, C. George; Ryan, Kenneth J.; Kenneth, Ryan (July 2004). Sherris Medical Microbiology: An Introduction to Infectious Diseases (4th ed.). McGraw Hill. p. 237\. ISBN 978-0-8385-8529-0. LCCN 2003054180. OCLC 52358530.
* 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 0021-9738.

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Techniques in clinical microbiology

Isolation
and culture|

| Isolation techniques|

* Asepsis
* Streak plate
* Selective media

|

Cultures by body site|

* Blood culture
* Genital culture
* Sputum culture
* Throat culture
* Urine culture
* Wound culture

Cultures by organism|

* Bacterial culture
* Fungal culture
* Viral culture

Identification
and testing|

| Manual testing: basic techniques|

* Colonial morphology
* Hemolysis
* Staining
* Gram stain
* Acid-fast stain
* Giemsa stain
* India ink stain
* Ziehl–Neelsen stain
* Wet prep
* Rapid tests
* Oxidase
* Catalase
* Indole
* PYR

|

Manual testing:
biochemical and immunologic tests|

* ALA test
* Amino acid decarboxylase test
* Bile solubility test
* CAMP test
* Citrate test
* Coagulase test
* DNAse test
* IMViC
* KOH test
* Methyl red test
* Nitrite test
* ONPG test
* Oxidative/fermentation glucose test
* Phenylalanine deaminase test
* Reverse CAMP test
* Salt tolerance test
* Sulfide indole motility test
* Triple sugar iron test
* Urease test
* rapid
* Voges–Proskauer test
* X and V factor test
* Bacitracin susceptibility test
* Optochin susceptibility test
* Novobiocin susceptibility test
* Lancefield grouping
* RPR test

Automated and point-of-care testing|

* Analytical profile index
* MALDI-TOF
* Polymerase chain reaction
* VITEK
* Rapid strep test
* Monospot test

Antibiotic susceptibility testing|

* Beta-lactamase test
* Disk diffusion test
* Etest
* McFarland standards
* Minimum inhibitory concentration

Equipment|

* Agar plate
* Growth medium
* Anaerobic jar
* Gas-pak
* Durham tube
* Biosafety cabinet
* Incubator
* Inoculation loop
* Inoculation needle

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