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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 at least 40 species. Of these, nine have two subspecies and one has three subspecies.^[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]

Taxonomy

The taxonomy is based on 16s rRNA sequences,^[4] and most of the staphylococcal species fall into 11 clusters:

S. aureus group – S. aureus, S. simiae
S. auricularis group – S. auricularis
S. carnosus group – S. carnosus, S. condimenti, S. massiliensis, S. piscifermentans, S. simulans
S. epidermidis group – S. capitis, S. caprae, S. epidermidis, S. saccharolyticus
S. haemolyticus group – S. devriesei, S. haemolyticus, S. hominis
S. hyicus-intermedius group – S. chromogenes, S. felis, S. delphini, S. hyicus, S. intermedius, S. lutrae, S. microti, S. muscae, S. pseudintermedius, S. rostri, S. schleiferi
S. lugdunensis group – S. lugdunensis
S. saprophyticus group – S. arlettae, S. cohnii, S. equorum, S. gallinarum, S. kloosii, S. leei, S. nepalensis, S. saprophyticus, S. succinus, S. xylosus
S. sciuri group – S. fleurettii, S. lentus, S. sciuri, S. stepanovicii, S. vitulinus
S. simulans group – S. simulans
S. warneri group – S. pasteuri, S. warneri

A twelfth group – that of S. caseolyticus – has now been moved to a new genus Macrococcus, the species of which are currently the closest known relatives of the Staphylococci.^[5]

Subspecies

S. aureus subsp. aureus
S. aureus subsp. anaerobius

S. capitis subsp. capitis
S. capitis subsp. urealyticus

S. carnosus subsp. carnosus
S. carnosus subsp. utilis

S. cohnii subsp. cohnii
S. cohnii subsp. urealyticus

S. equorum subsp. equorum
S. equorum subsp. linens

S. hominis subsp. hominis
S. hominis subsp. novobiosepticus

S. saprophyticus subsp. bovis
S. saprophyticus subsp. saprophyticus

S. schleiferi subsp. coagulans
S. schleiferi subsp. schleiferi

S. sciuri subsp. carnaticus
S. sciuri subsp. rodentium
S. sciuri subsp. sciuri

S. succinus subsp. casei
S. succinus subsp. succinus

Notes

As with all generic names in binomial nomenclature, Staphylococcus is capitalized when used alone or with a specific species. However, it is not capitalized or italicized when used in adjectival forms, as in a staphylococcal infection, or as the plural (staphylococci).^[6]

The S. saprophyticus and S. sciuri groups are generally novobiocin-resistant, as is S. hominis subsp. novobiosepticus.

Members of the S. sciuri group are oxidase-positive due to their possession of the enzyme cytochrome c oxidase. This group is the only clade within the Staphylococci to possess this gene.

The S. sciuri group appears to be the closest relations to the genus Macrococcus.

Staphylococcus pulvereri has been shown to be a junior synonym of Staphylococcus vitulinus.^[7]

Within these clades, the S. haemolyticus and S. simulans groups appear to be related, as do the S. aureus and S. epidermidis groups.^[8]

S. lugdunensis appears to be related to the S. haemolyticus group.

S. croceolyticus may be related to S. haemolyticus, but this needs to be confirmed.

The taxonomic position of S. croceolyticus, S. leei, S. lyticans and S. pseudolugdunensis has yet to be clarified. The published descriptions of these species do not appear to have been validly published to date (2010).

Biochemical identification

Assignment of a strain to the genus Staphylococcus requires it to be a Gram-positive coccus that forms clusters, produces catalase, has an appropriate cell wall structure (including peptidoglycan type and teichoic acid presence) and G + C content of DNA in a range of 30–40 mol%.

Staphylococcus species can be differentiated from other aerobic and facultative anaerobic, Gram-positive cocci by several simple tests. Staphylococcus spp. are facultative anaerobes (capable of growth both aerobically and anaerobically). All species grow in the presence of bile salts and all are catalase-positive. Growth can also occur in a 6.5% NaCl solution. On Baird Parker medium, Staphylococcus spp. grow fermentatively, except for S. saprophyticus, which grows oxidatively. Staphylococcus spp. are resistant to bacitracin (0.04 U disc: resistance = <10mm zone of inhibition) and susceptible to furazolidone (100μg disc: resistance = <15mm zone of inhibition). Further biochemical testing is needed to identify to the species level.

Coagulase production

One of the most important phenotypical features used in the classification of staphylococci is their ability to produce coagulase, an enzyme that causes blood clot formation.

Six species are currently recognised as being coagulase-positive: S. aureus, S. delphini, S. hyicus, S. intermedius, S. lutrae,S. pseudintermedius and S. schleiferi subsp. coagulans. These species belong to two separate groups – the S. aureus (S. aureus alone) group and the S. hyicus-intermedius group (the remaining five).

A seventh species has also been described – Staphylococcus leei – from patients with gastritis.^[9]

S. aureus is coagulase-positive, meaning it produces coagulase. However, while the majority of S. aureus strains are coagulase-positive, some may be atypical in that they do not produce coagulase. S. aureus is 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.

S. epidermidis, a coagulase-negative 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.

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 it 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 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.^[10]

The widespread incidence of antibiotic resistance across various strains of S. aureus, or across different species of Staphylococcus has been attributed to horizontal gene transfer of genes encoding antibiotic/metal resistance and virulence. A recent study demonstrated the extent of horizontal gene transfer among Staphylococcus to be much greater than previously expected, and encompasses genes with functions beyond antibiotic resistance and virulence, and beyond genes residing within the mobile genetic elements.^[11]

Various strains of Staphylococcus are available from biological research centres, such as the National Collection of Type Cultures (NCTC).

Host range

Unknown variety of Staphylococcus, Gram-stained - numbered ticks on the scale are 11 microns apart.

Members of the genus Staphylococcus frequently colonize the skin and upper respiratory tracts of mammals and birds. Some species specificity has been observed in host range, such that the Staphylococcus species observed on some animals appear more rarely on more distantly related host species.^[12] Some of the observed host specificity includes:

S. arlattae – chickens, goats
S. auricularis – deer, dogs, humans
S. capitis – humans
S. caprae – goats, humans
S. cohnii – chickens, humans
S. delphini – dolphins
S. devriesei – cattle
S. epidermiditis – humans
S. equorum – horses
S. felis – cats
S. fleurettii – goats
S. gallinarum – chickens, goats, pheasants
S. haemolyticus – humans, Cercocebus, Erythrocebus, Lemur, Macca, Microcebus, Pan
S. hyicus – pigs
S. leei – humans
S. lentus – goats, rabbits, sheep
S. lugdunensis – humans, goats
S. lutrae – otters
S. microti – voles (Microtus arvalis)
S. nepalensis – goats
S. pasteuri – humans, goats
S. pettenkoferi – humans
S. pseudintermedius – dogs
S. rostri – pigs
S. schleiferi – humans
S. sciuri – humans, dogs, goats
S. simiae – South American squirrel monkeys (Saimiri sciureus)
S. simulans – humans
S. warneri – humans, Cercopithecoidea, Pongidae
S. xylosus – humans

Clinical

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 they can be produced by bacteria growing in improperly-stored food items.
The most common sialadenitis is caused by staphylococci, as bacterial infections.^[13]

See also

• MRSA
• Vancomycin-resistant S. aureus
• Staphylococcus aureus
• Staphylococcal enteritis

Notes and references

Staphylococcus hyicus is a Gram positive member of the bacterial genus Staphylococcus consisting of clustered cocci. Originally isolated from skin infections in pigs and named Micrococcus hyicus, the species was moved to its present genus on the basis of phenotypic similarities.^[1]

S. hyicus is a known animal pathogen. It causes skin disease in cattle,^[2] horses,^[3] and pigs.^[4]

References

This bacteria-related article is a stub. You can help Wikipedia by expanding it. v t e

Staphylococcus nepalensis is a Gram positive coccoid bacterium belonging to the genus Staphylococcus.

History

This species was first isolated from the respiratory tract of goats in 2003.^[1]

Description

The bacteria are non motile, oxidase negative, catalase positive, Gram positive cocci, 1·1–1·6 micrometres in diameter, that occur singly, in pairs and in irregular clusters.

The G+C content of the type strain is 33 mol%

Colonies after 2 days on P agar are circular, low-convex, smooth, glossy, opaque white and 2–6 millimeters in diameter. Growth occurs aerobically and anaerobically in the presence of 0–7·5% sodium chloride (NaCl). The type strain grows well in the presence of 10% NaCl but growth is variable for other strains. No growth is observed in the presence of 15% NaCl. Growth occurs between 20 and 40°C: best growth occurs at 30°C. No growth is observed at 15 or 45°C.

Produces urease, alkaline phosphatase, pyrrolidonyl arylamidase, beta-galactosidase and beta-glucuronidase. Hydrolyses aesculin and Tween 80. Reduces nitrate to nitrite.

It is negative for clumping factor, coagulase, hyaluronidase, arginine dihydrolase, ornithine decarboxylase, acetoin, arginine arylamidase, alpha- and beta-haemolysins, heat-stable and heat-labile nucleases, indole, hydrogen sulphide and lecithinase.

It produces acid aerobically from D-glucose, D-fructose, D-mannose, maltose, lactose, trehalose, mannitol, sucrose, L-arabinose, N-acetylglucosamine, galactose, glycerol, erythritol, D-xylose, arbutin and salicin.

Acid is not formed aerobically from D-raffinose, ribose, D-cellobiose, D-arabinose, L-xylose, adonitol, methyl-D-xyloside, rhamnose, L-sorbose, dulcitol, starch, inositol, methyl-D-mannoside, methyl-D-glucoside, amygdalin, melibiose, melezitose, gentiobiose, glycogen, inulin, D-tagatose, D-lyxose, cellobiose, D-fucose, L-fucose, L-arabitol, gluconate, 2-ketogluconate or 5-ketogluconate.

Acid production from D-arabitol, sorbitol, turanose and xylitol is variable; the type strain is positive.

It is resistant to novobiocin, bacitracin, vibriostatic agent O/129, lysozyme, metronidazole and optochin.

It is susceptible to lysostaphin, furazolidone, ampicillin, amoxicillin, amoxicillin/clavulanic acid, ceftiofur, cephalexin, cephalothin, chloramphenicol, clindamycin, colistin sulphate, enrofloxacin, erythromycin, florfenicol, fosfomycin, fusidic acid, gentamicin, kanamycin, lincomycin, neomycin, nitrofurantoin, oxacillin, penicillin G, polymyxin B, sulfamethoxazole/trimethoprim, tetracycline and vancomycin.

The quinone system consists of the major menaquinone MK-7 and minor amounts of MK-6 and MK-8. Predominant fatty acids are ai-C15 : 0, i-C15 : 0 and ai-C17 : 0, whilst i-C17 : 0, C18 : 0, C16 : 0, C20 : 0 and i-C19 : 0 are present in moderate amounts. Polar lipid profile consists of the major lipids diphosphatidylglycerol, phosphatidylglycerol and an unknown glycolipid.

Epidemiology

This species has been isolated from dry cured ham.^[2]

Clinical

This species has been isolated from human urine but its pathologcial significance is not yet clear.^[3]

References

Staphylococcus muscae is a Gram positive coccoid bacterium belonging to the genus Staphylococcus.

History

This species was first isolated from flies (Musca domestica and Stomoxys calcitrans) caught in a cow shed in 1992.^[1]

Description

This species consists of small Gram positive cocci that range from 0.4 to 1.1 pm in diameter and are arranged predominantly in irregular clumps, occasionally in pairs and singly. The spherical or slightly ovoid cells are nonmotile and nonsporeforming.

The G+C content of the genome is 40-41%.

Colonies on P agar (after 5 days at 37°C) are only slightly convex with gently raised centers, circular, entire, smooth, faintly glistening, butyrous, opaque, grayish white, and 5-6 mm in diameter.

The species grow well in the presence of sodium chloride (NaCl) at concentrations up to 10%; no growth occurs at an NaCl concentration of 15%. They grow moderately at 25°C; no growth occurs at 10 and 45°C.

They are facultative anaerobes. Better growth occurs under aerobic conditions. Anaerobic growth in semisolid thioglycolate medium is evident after 24 to 48 hours.

This species produces catalase, phosphatase and heat-labile nuclease. It is positive in the benzidine test and weakly positive in methyl red test. It exhibit clear hemolysis on ovine blood agar medium. It produces lecithinase, splits Tween 20, Tween 40 and Tween 80 and reduces nitrate. On crystal violet agar it may produce white (positive, E type) colonies or blue (negative, D type) colonies.

It does not produce oxidase, coagulase, clumping factor, fibrinolysin, thermostable nuclease, tellurite reductase, gelatinase, protease, urease, arginine dihydrolase, alpha- or beta-haemeolysins, ornithine decarboxylase, acetyl-methylcarbinol or beta-galactosidase. It does not hydrolyze starch or esculin.

The species produces acid aerobically from glucose (without gas), fructose, sucrose, trehalose, turanose, xylose, and glycerol. No acid is produced from adonitol, arabinose, arbutin, cellobiose, dulcitol, fucose, galactose, inositol, inulin, lactose, maltose, mannitol, mannose, melezitose, melibiose, raffinose, rhamnose, ribose, salicin, sorbose, or tagatose. It normally weakly produces acid anaerobically from glucose.

It is resistant to lysozyme (minimum inhibitory concentration (MIC) >1,000 kg/ml) and susceptible to novobiocin (MIC, 0.06 to 0.1 pg/ml), penicillin (MIC, 0.01 to 0.06 pg/ml), oxacillin (MIC,0.2 pg/ml), ampicillin (MIC, 0.06 to 1.0 pg/ml), cephaloridine(MIC, 0.1 to 0.2 pg/ml), erythromycin (MIC, 0.06 pg/ml), lincomycin (MIC, 0.2 to 0.5 pg/ml), clindamycin (MIC, 0.1 pg/ml), chloramphenicol (MIC, 2.0 pg/ml), tetracycline (MIC, 0.1 to 0.2 pg/ml), gentamicin (MIC, 0.2 pg/ml) and vancomycin (MIC, 1.0 pg/ml). It is resistant to bacitracin (10 U per disc) and susceptible to furadantin (100 pg per disc).

The cell walls contain a glycine-rich peptidoglycan.

Epidemiology

This species has been isolated from Musca domestica and Stomoxys calcitrans. It is probably a commensal of cattle.

Clinical

This species is not known to be associated with disease.

References

Staphylococcus capitis is a coagulase negative species (CoNS) of Staphylococcus. It is part of the normal flora of the skin of the human scalp, face, neck, and ears and has been associated with prosthetic valve endocarditis but is rarely associated with native valve infection.

Clinical importance

CoNS produce a slimy biofilm enabling them to adhere to medical devices such as prosthetic valves and catheters and makes them difficult to remove by patient immune response to antibiotic therapy. As native flora of the skin and mucous membranes, they may be introduced anytime these are punctured, i.e. at the time of device placement, venipuncture or through breaks in the mucous membrane or skin. CoNS species, such as Staph. epidermidis and staphylococcus capitis, are recorded as the most common cause of prosthetic valve endocarditis. ^[1][2][3]

References

This bacteria-related article is a stub. You can help Wikipedia by expanding it.v · d · e

http://www.rch.org.au/washup/prof.cfm?doc_id=5004