Staphylococcus
| Staphylococcus | |
|---|---|
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| SEM micrograph of S. aureus colonies; note the grape-like clustering common to Staphylococcus species. | |
| Scientific classification | |
| Kingdom: | Bacteria |
| Phylum: | Firmicutes |
| Class: | Bacilli |
| Order: | Bacillales |
| Family: | Staphylococcaceae |
| Genus: | Staphylococcus Rosenbach 1884 |
| Species | |
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S. afermentans |
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Staphylococcus (from the Greek: σταφυλή, staphylē, "bunch of grapes" and κόκκος, kókkos, "granule") is a genus of Gram-positive bacteria. Under the microscope they appear round (cocci), and form in grape-like clusters.[1]
The Staphylococcus genus includes thirty-two species and eight sub-species.[2] Most are harmless and reside normally on the skin and mucous membranes of humans and other organisms. Found worldwide, they are a small component of soil microbial flora.[3]
Contents |
Role in disease
Staphylococcus can cause a wide variety of diseases in humans and other animals through either toxin production or penetration. Staphylococcal toxins are a common cause of food poisoning, as it can grow in improperly-stored food.
Classification
The main classification of staphylococci is based on their ability to produce coagulase, an enzyme that causes blood clot formation.
Coagulase-positive
- S. aureus is coagulase-positive, meaning that they can produce coagulase. However, while the majority of S. aureus are coagulase-positive, some may be atypical in that they do not produce coagulase. S aureus is also catalase-positive (meaning that it can produce the enzyme catalase) and able to convert hydrogen peroxide (H2O2) to water and oxygen, which makes the catalase test useful to distinguish Staphylococci from Enterococci and Streptococci.
- S. pseudintermedius inhabits and sometimes infects the skin of domestic dogs and cats. This organism, too, can carry the genetic material that imparts multiple bacterial resistance. It is rarely implicated in infections in humans, as a zoonosis.
Coagulase-negative
- S. epidermidis, a coagulase-negative staphylococcus species, is a commensal of the skin, but can cause severe infections in immune-suppressed patients and those with central venous catheters.
- S. saprophyticus, another coagulase-negative species that is part of the normal vaginal flora, is predominantly implicated in genitourinary tract infections in sexually-active young women.
- In recent years, several other Staphylococcus species have been implicated in human infections, notably S. lugdunensis, S. schleiferi, and S. caprae.
Common abbreviations for coagulase-negative staphylococcus species are CoNS and CNS.
Biochemical identification
Staphylococcus species can be differentiated from other aerobic and facultative anaerobic gram positive cocci by several simple tests. Staphylococcus spp. are facultative anaerobes. Facultative anaerobes are capable of growth both aerobically and anaerobically. All species grow in the presence of bile salts and one (S. aureus) is catalase positive. Growth also occurs in a 6.5% NaCl solution. On Baird Parker Medium Staphylococcus spp. show as fermentative, except for S. saprophyticus, which is oxidative. Staphylococcus spp. are resistant to Bacitracin (0.04 U resistance = <10mm zone of inhibition) and susceptible to Furazolidone (100μg resistance = <15mm zone of inhibition).
Further biochemical testing is needed to identify down to the species level.
Genomics and molecular biology
The first S. aureus genomes to be sequenced were those of N315 and Mu50 in 2001. Many more complete S. aureus genomes have been submitted to the public databases, making S. aureus one of the most extensively sequenced bacteria. The use of genomic data is now widespread and provides a valuable resource for researchers working with S. aureus. Whole genome technologies such as sequencing projects and microarrays have shown there is an enormous variety of S. aureus strains. Each contains different combinations of surface proteins and different toxins. Relating this information to pathogenic behaviour is one of the major areas of staphylococcal research. The development of molecular typing methods has enabled the tracking of different strains of S. aureus. This may lead to better control of outbreak strains. A greater understanding of how the staphylococci evolve, especially due to the acquisition of mobile genetic elements encoding resistance and virulence genes is helping to identify new outbreak strains and may even prevent their emergence.[4]
External links
- Staphylococcus genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
- Staphylococcus Infection Pictures - Pictures of Staph Infections, MRSA, and the associated skin diseases caused by these infections.
See also
- MRSA
- Staphylococcus aureus
- Staphylus
Notes and references
- ↑ Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0838585299.
- ↑ Harris L.G, Foster S.J (editor) (2002). AN INTRODUCTION TO STAPHYLOCOCCUS AUREUS, AND TECHNIQUES FOR IDENTIFYING AND QUANTIFYING S. AUREUS ADHESINS IN RELATION TO ADHESION TO BIOMATERIALS: REVIEW (LE.uGr.o Hpaearrni sC eetl lasl a n d M a t e r i a l s V o l . 4 . 2 0 0 2 ( p a g e s 3 9 - 6 0 ) ed.).
- ↑ Madigan M, Martinko J (editors). (2005). Brock Biology of Microorganisms (11th ed.). Prentice Hall. ISBN 0131443291.
- ↑ Lindsay J (editor). (2008). Staphylococcus: Molecular Genetics. Caister Academic Press. ISBN 978-1-904455-29-5 . ISBN 1904455298. http://www.horizonpress.com/staph.