Is Staphylococcus aureus coagulase negative?

Clinical isolates of the human pathogen Staphylococcus aureus secrete coagulase (Coa), a polypeptide that binds to and activates prothrombin, thereby converting fibrinogen to fibrin and promoting clotting of plasma or blood.

Coagulase test is used to differentiate Staphylococcus aureus (positive) which produce the enzyme coagulase, from S. epidermis and S. saprophyticus (negative) which do not produce coagulase.

Coagulase-negative staphylococci (CoNS) are a type of staph bacteria that commonly live on a person’s skin. Doctors typically consider CoNS bacteria harmless when it remains outside the body. However, the bacteria can cause infections when present in large amounts, or when present in the bloodstream.

If ‘positive’ (e.g., the suspect colony is S. aureus), the plasma will coagulate, resulting in a clot (sometimes the clot is so pronounced, the liquid will completely solidify). If ‘negative’, the plasma remains a liquid.

Staphylococcus aureus is a gram-positive, catalase-positive, coagulase-positive cocci in clusters. S. aureus can cause inflammatory diseases, including skin infections, pneumonia, endocarditis, septic arthritis, osteomyelitis, and abscesses.

After application and penetration of hydrochloric acid into the medium, DNase positive organisms such as Staphylococcus aureus or Serratia marcescens will be surrounded by clear zones of depolymerized DNA while the medium farer away from the inoculation band will be opaque and whitish due to polymerized DNA.

deoxyribonuclease plate test, found 36% of S. epidermidis strains to be deoxyribonuclease- positive.

Staphylococci are facultative anaerobes Gram-positive bacteria that grow by aerobic respiration or by fermentation that yields principally lactic acid. The bacteria are catalase-positive and oxidase-negative.

Coagulase-negative staphylococci as reservoirs of genes facilitating MRSA infection: Staphylococcal commensal species such as Staphylococcus epidermidis are being recognized as important sources of genes promoting MRSA colonization and virulence. Bioessays.

Streptococci are Gram-positive, nonmotile, nonsporeforming, catalase-negative cocci that occur in pairs or chains. Older cultures may lose their Gram-positive character.

If coag-negative staph is considered pathogenic, vancomycin is the preferred treatment. Second-line alternatives that are also active in the setting of methicillin resistance such as telavancin, linezolid, or daptomycin may be considered based on patient factors and the site of infection.

Staphylococcus saprophyticus is a Gram-positive, coagulase-negative, non-hemolytic coccus that is a common cause of uncomplicated urinary tract infections (UTIs), particularly in young sexually active females.

Coagulase positive staphylococci are known human pathogens. Transmission of these organisms occurs through direct contact with colonized or infected persons or through indirect contact with contaminated objects. S. aureus is the most common species in this group; additional species include S.

When the stain combines with bacteria in a sample, the bacteria will either stay purple or turn pink or red. If the bacteria stays purple, they are Gram-positive. If the bacteria turns pink or red, they are Gram-negative.

Commonly isolated Gram-negative organisms include Pseudomonas, Klebsiella, Proteus, Salmonella, Providencia, Escherichia, Morganella, Aeromonas, and Citrobacter. Occasionally, Gram-positive organisms (e.g., Streptococcus, Corynebacteria) are the primary organisms, or are found concurrently with Gram-negative bacteria.

Gram-negative bacteria are surrounded by a thin peptidoglycan cell wall, which itself is surrounded by an outer membrane containing lipopolysaccharide. Gram-positive bacteria lack an outer membrane but are surrounded by layers of peptidoglycan many times thicker than is found in the Gram-negatives.

Staphylococcus epidermidis is a coagulase-negative, gram-positive cocci bacteria that form clusters. It is also a catalase-positive and facultative anaerobe.

Microscopic morphology. S. aureus cells are Gram-positive and appear in spherical shape. They are often in clusters resembling bunch of grapes when observed under light microscope after Gram staining.

All Staphylococcus species produce catalase except for S. aureus subsp. anaerobius and S. saccharolyticus (9).

aureus isolates, 17 (85%) were found as positive for coagulase, catalase, methylene red, Voges-proskauer and hemolysis tests and negative for oxidase and indole tests. They also produce acid from glucose, lactose and sucrose.

Streptococci are Gram-positive cocci that grow in pairs or chains. They are readily distinguished from staphylococci by their Gram-stain appearance and by a negative catalase test. More than 30 species have been identified.

This test differentiates pathogenic Staphylococcus aureus which is gelatinase-positive from non-pathogenic epidermidis which is gelatinase negative. This test can be used to differentiate Serratia and Proteus species which are gelatin positive from other members of Enterobacteriaceae family.

CharacteristicsE. coliBile Solubility–Fermentation ofArabinosePositive (+ve)DNaseNegative (-ve)

Expected Results Positive: Medium is colorless around the test organism. Negative: If no degradation of DNA occurs, the medium remains green.

Escherichia coli and Shigella dysenteriae are citrate negative. This agar is used to identify organisms that are capable of producing the enzyme lipase.

Staphylococcus epidermidis which is known as a coagulase-negative and Gram-positive Staphylococcus, is one of the five significant microorganisms that are located on human skin and mucosal surfaces with the ability of causing nosocomial infections due to the wide usage of medical implants and devices, hence until 1980 …

Basic CharacteristicsProperties (Serratia marcescens)ArabinoseNegative (-ve)ArabitolVariableCellobioseNegative (-ve)DNasePositive (+ve)

DNase agar is a differential medium that tests the ability of an organism to produce an exoenzyme, called deoxyribonuclease or DNase, that hydrolyzes DNA. DNase agar contains nutrients for the bacteria, DNA, and methyl green as an indicator. Methyl green is a cation which binds to the negatively-charged DNA.

Two forms of motility have recently been described for Staphylococcus aureus, an organism previously considered to be non-motile. One form is called spreading, which is a type of sliding motility and the second form involves comet formation, which has many observable characteristics associated with gliding motility.

S. aureus is nonmotile, non-spore forming, catalase and coagulase positive.

Two different coagulase tests are commonly used to identify S. aureus. One is a tube test for free coagulase and the other is a slide test for bound coagulase. The tube coagulase test is thought to be the more definitive of the two, however, it can take several hours to overnight to produce a result.

Staphylococcus is the group of bacteria responsible for staph infections, with Staphylococcus aureus being the most common form. The main difference is that non-MRSA generally responds well to a variety of antibiotics, while MRSA may only respond to a few, making it harder to treat.

The most common species detected were Staphylococcus epidermidis, Staphylococcus hominis, and Staphylococcus haemolyticus. These three species accounted for nearly 98% of the clinically significant isolates and 89% of the contaminants. The isolation of other species almost always represented contamination.

Staphylococcus aureus is a Gram positive, coagulase positive coccus in the family Staphylococcaceae. Methicillin-resistant S. aureus strains have acquired resistance to methicillin and other beta lactam antibiotics (e.g., penicillins and cephalosporins) via the mecA or mecC genes.

Group B SStep are Gram positive cocci in pairs and short chains on Gram stain. The most accurate way to identify group B Streptococcus (GBS) is to demonstrate that the bacteria in question has the Lancefield group B antigen on the surface of the bacteria.

Non–group A streptococcus (NGAS) is detected in close to 12% of throat cultures performed for pharyngitis in school-age children. The detected bacteria likely reflect colonization rather than infection.

Gram-positive bacteria are bacteria with thick cell walls. In a Gram stain test, these organisms yield a positive result. The test, which involves a chemical dye, stains the bacterium’s cell wall purple. Gram-negative bacteria, on the other hand, don’t hold the dye.

Although novobiocin is no longer used to treat bacterial infections in people, the drug is still produced for veterinary medicine and remains in drug libraries for research.

Staphylococcus haemolyticus, also found among the normal skin flora, is commonly isolated from the axillae, perineum, and inguinal areas of humans (23).