staphylococcus n : spherical gram-positive parasitic bacteria that tend to form irregular colonies; some cause boils or septicemia or infections [syn: staphylococci, staph] [also: staphylococci (pl)]

English

Noun

staphylococcus

1. A spherical gram-positive parasitic bacterium of the genus Staphylococcus, causing blisters, septicemia, and other infections

Staphylococcus (in Greek staphyle means bunch of grapes and coccos means granule) is a genus of Gram-positive bacteria. Under the microscope they appear round (cocci), and form in grape-like clusters.

The Staphylococcus genus includes thirty-one species. 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.

Role in disease

Staphylococcus can cause a wide variety of diseases in humans and other animals through either toxin production or invasion. Staphylococcal toxins are a common cause of food poisoning, as it can grow in improperly-stored food. One pathogenic species is Staphylococcus aureus, which can infect wounds. These bacteria can survive on dry surfaces, increasing the chance of transmission. S. aureus is also implicated in toxic shock syndrome; during the 1980s some tampons allowed the rapid growth of S. aureus, which released toxins that were absorbed into the bloodstream. Any S. aureus infection can cause the staphylococcal scalded skin syndrome, a cutaneous reaction to exotoxin absorbed into the bloodstream. It can also cause a type of septicaemia called pyaemia. The infection can be life-threatening. Problematically, Methicillin-resistant Staphylococcus aureus (MRSA) has become a major cause of hospital-acquired infections, and is being recognized with increasing frequency in community-acquired infections.

• The coagulase-positive Staphylococcus that inhabits and sometimes infects the skin of domestic dogs and cats is Staphylococcus pseudintermedius. This organism, too, can carry the genetic material that imparts multiple bacterial resistance. It is rarely implicated in infections in humans, as a zoonosis.

• 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.

• S. aureus is also one of the most common causes of closed-space infections of the fingertips, known as paronychia.

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 are 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 where 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.

See also

• Staphylus
• Staphylococcus aureus

References

adenovirus, aerobe, aerobic bacteria, amoeba, anaerobe, anaerobic bacteria, bacillus, bacteria, bacterium, bug, coccus, disease-producing microorganism, echovirus, enterovirus, filterable virus, fungus, germ, gram-negative bacteria, gram-positive bacteria, microbe, microorganism, mold, nonfilterable virus, pathogen, picornavirus, protozoa, protozoon, reovirus, rhinovirus, rickettsia, spirillum, spirochete, spore, streptococcus, trypanosome, vibrio, virus