6 Qahtani, 2006; Akpakaet al., 2006). Presumptive Staphylococcus

6 Classification of Staphylococci:

Staphylococcal species
have traditionally being differentiated using different phenotypic testssuch as
the coagulase and the DNase test (Martineau et
al., 2000; Mugaluet al., 2006;
Belloand Qahtani, 2006; Akpakaet al.,
2006). Presumptive Staphylococcus aureus
can beidentified based on DNase tests and growth on mannitol salt agar (MSA). Staphylococcus aureus gives a positive
coagulase and DNase test while most species of coagulase negative staphylococci
give a negative DNase test (Kateeteet al,
2010).

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1.1.7 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 species are facultative anaerobes
(capable of growth both aerobically and anaerobically). All species grow in the
presence of bile salts.All species were once thought to be coagulase-positive,
but this has since been disproven.( Ryan KJ, Ray CG, eds. 2004, PreTest,
Surgery, 12th ed, Matthews KR 1997).

Growth
can also occur in a 6.5% NaCl solution. On Baird Parker medium, Staphylococcus
species grow fermentatively, except for S. saprophyticus, which grows
oxidatively. Staphylococcus species are resistant to bacitracin (0.04 U disc:
resistance = < 10 mm zone of inhibition) and susceptible to furazolidone (100 ?g disc: resistance = < 15 mm zone of inhibition). Further biochemical testing is needed to identify to the species level. When these bacteria divide, they do so along two axes, so form clumps of bacteria. This is as opposed to streptococci, which divide along one axis, so form chains (strep meaning twisted or pliant). 1.1.8 Coagulase production Phenotypical features is one of the major characteristic used in the classification of staphylococci i.e. their ability to produce coagulase, an enzyme that causes formation of blood clot clotting. Six species are currently recognized 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 (Jin M, Rosario W, Watler E, Calhoun DH (2004). S. aureus is coagulase-positive, which means it produces coagulase. However, while the majority of S. aureus strains are coagulase-positive, some may be atypical because 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 can sometimes infect the skin of domestic cats and dogs. This organism, too, can carry the genetic material that imparts multiple bacterial resistances. 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 immunosuppressed 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 staphylococci are CoNS, CNS, or CNST.13 The American Society for Microbiology abbreviates coagulase-negative staphylococci as "CoNS" 1.1.9 Coagulase-Negative Staphylococci Coagulase-negative staphylococci are a heterogeneous group of staphylococci that give a negative result to the coagulase test and were historically regarded to be more or less nonpathogenic. However because of patient and procedure-related changes CoNS are now one of the major nosocomial pathogens with the most important species being Staphylococcus epidermidis and Staphylococcus haemolyticus. Many CoNS species are DNase negative, for example Staphylococcus epidermidis. They significantly account for infections in preterm infants and foreign body-related infections. S. lugdunensis in some aspects resembles S. aureus in causing infectious endocarditis whereas S. saprophyticus has been linked with acute urethritis (Becker et al., 2014). Different parts of the mucous membranes and skins of animals and humans are colonized by many CoNS species that are less commonly involved in clinically manifested infections compared to CoNS found as food-associated saprophytes (Grice and Segre, 2011; Becker et al., 2014). CoNS are typical opportunistic pathogens and have a significant impact on human health and life. They are specifically linked with the use of implanted or indwelling foreign bodies that are crucial in modern medicine. Endogeneous infections resulting from colonisation of different parts of the host are caused by CoNS, however they are transmitted. 1.2Staphylococcus aureus:   Is a Gram-positive, round-shaped bacterium that is a member of the Firmicutes, and it is a member of the normal flora of the body, frequently found in the nose, respiratory tract, and on the skin. It is often positive for catalase and nitrate reduction and is a facultative anaerobe that can grow withoutthe need for oxygen (Masalha M; et al. (2001). Although Staphylococcus aureus is not always pathogenic, it causes skin infection, respiratory infections abscesses, and food poisoning, the pathogenic strain promote infections by producing virulence factors. The emergence of antibiotic resistant staphylococci such as methicilline resistant staphylococcus aureus is a major problem to the world. Staphylococcus was first identified in 1880 in Aberdeen, Scotland, by surgeon Sir Alexander Ogston in pus from a surgical abscess in a knee joint. ( Ogston A (1984)).  This name was later amended to Staphylococcus aureus by Friedrich Julius Rosenbach, ("Whonamedit - dictionary of medical eponyms". www.whonamedit.com )  who was credited by the official system of nomenclature at the time. 1.2.1Methicillin-Resistant Staphylococcus aureus Methicillin-resistant Staphylococcus aureus (MRSA) is a strain that's resistant to the usual antibiotics used to treat staph infection, making MRSA infections more difficult to treat. MRSA usually infects the skin. This generally mild infection can be treated with a different set of antibiotics and attentive sk