More than 90% of staphylococcal isolates now produce penicillinase

The overall mortality rate was 15%, with no significant difference between groups.

Streptococcus Penicillinplusclindamycin 2–4 million units every 4–6 h IV (adult)600–900 mg every 8 h IV 60 000–100 000 units/kg/dose every 6 h IV10–13 mg/kg/dose every 8 h IV Vancomycin, linezolid, quinupristin/dalfopristin, daptomycin Staphylococcus aureus Nafcillin 1–2 g every 4 h IV 50 mg/kg/dose every 6 h IV Vancomycin, linezolid, quinupristin/dalfopristin, daptomycin Oxacillin 1–2 g every 4 h IV 50 mg/kg/dose every 6 h IV Cefazolin 1 g every 8 h IV 33 mg/kg/dose every 8 h IV Vancomycin (for resistant strains) 30 mg/kg/d in 2 divided doses IV 15 mg/kg/dose every 6 h IV  

The efficacy of vancomycin for the treatment of patients with infections due to Staphylococcus aureus is impaired by its poor tissue penetration and by its relatively weak antibacterial activity

Our effort to identify known virulence genes revealed a surprising deficiency of toxin genes other than pvl, lukD, and lukE.

Wound cultures were monomicrobial for MRSA in 12 patients (86 percent).

Eleven patients (79 percent) required débridement that was described as either “wide” or “radical,” often with incisions greater than 15 cm, and three required subsequent skin grafting.

Ten of the 14 patients were men (71 percent), and the median age was 46 years (

This finding suggests that necrotizing fasciitis caused by community-associated MRSA has the potential to cause rapidly progressive disease that is clinically indistinguishable from necrotizing fasciitis caused by pathogens such as group A streptococcus. Furthermore, although none of the patients died, serious complications were common, including prolonged stays in the intensive care unit, the need for mechanical ventilation and reconstructive surgery, septic shock, nosocomial infections, and endophthalmitis.

The absence of deaths in our series suggests that necrotizing fasciitis caused by community-associated MRSA may be less virulent than similar infections caused by other organisms. Indeed, the onset of disease in our series was often subacute, with symptoms present an average of 6 days before admission (range, 3 to 21).

To date, MRSA has been reported to be associated with necrotizing fasciitis in only one case of subacute, polymicrobial infection25 and as a monomicrobial cause of an iatrogenic, surgery-associated “necrotizing fasciitis–like” infection and bacteremia.

S. aureus has not been described as a monomicrobial cause of necrotizing fasciitis in major clinical reviews of the topic or in published microbiologic studies of the disease.1

NOVOBIOCIN (

Beta hemolytic

COAGULASE test which is positive for Staphylococcus aureus (generally accepted criterion for the identification) and negative for all other Staphylococci. Coagulase is an enzyme used by S.aureus to induce coagulation and convert soluble fibrinogen into fibrin which will protect bacteria from the immune system. It is also a clumping factor for bacteria’s coalescence. All other staphylococcus species can be collectively referred to as coagulase-negative staphylococci.

The main criterion for differentiation between Staphylococcus and Streptococcus genera is the catalase test. Staphylococci are catalase positive whereas Streptococci are Catalase negative.

Novobiocin is an aminocoumarin. Aminocoumarins are very potent inhibitors of bacterial DNA gyrase and work by inhibiting the GyrB subunit of the enzyme involved in energy tranduction. Novobiocin as well as the other aminocoumarin antibiotics act as competitive inhibitors of the ATPase reaction catalysed by GyrB.

Isotopic experiments showed that, in addition to inhibiting cell-wall synthesis, novobiocin also inhibited both protein and nucleic acid synthesis

Staphylococci are spherical gram-positive bacteria, which are immobile and form grape-like clusters. They form bunches because they divide in two planes as opposed to their close relatives streptococci which form chains because they divide only in one plane.

Growth and survival characteristics

S. aureus is a facultative anaerobe so can grow under both aerobic and anaerobic conditions. However, growth occurs at a much slower rate under anaerobic conditions

The temperature range for growth of S. aureus is 7–48°C, with an optimum of 37°C.S. aureus is resistant to freezing and survives well in food stored below -20°C; however, viability is reduced at temperatures of -10 to 0°C. S. aureus is readily killed during pasteurisation or cooking. Growth of S. aureus occurs over the pH range of 4.0–10.0, with an optimum of 6–7

Staphylococcus aureus

These events cause the symptoms of septic shock that occur during severe infections caused by S aureus.

S aureus cells express on their surface proteins that promote attachment to host proteins such as laminin and fibronectin that form part of the extracellular matrix

The catalase test is important in distinguishing streptococci (catalase-negative) staphylococci which are catalase positive.

ests for clumping factor, coagulase, hemolysins and thermostable deoxyribonuclease are routinely used to identify S aureus. Commercial latex agglutination tests are available. Identification of S epidermidis is confirmed by commercial biotyping kits.

Basic Characteristics Properties (Staphylococcus aureus) Capsule Non-Capsulated Catalase Positive (+ve) Citrate Positive (+ve) Coagulase Positive (+ve) Gas Negative (-ve) Gelatin Hydrolysis Positive (+ve) Gram Staining Positive (+ve) H2S Negative (-ve) Hemolysis Positive (+ve)- Beta Indole Negative (-ve) Motility Negative (-ve) MR (Methyl Red) Positive (+ve) Nitrate Reduction Positive (+ve) OF (Oxidative-Fermentative) Fermentative Oxidase Negative (-ve) Pigment Mostly Positive (+ve) PYR Negative (-ve) Shape Cocci Spore Non-Sporing Urease Positive (+ve) VP (Voges Proskauer) Positive (+ve) Fermentation of Arabinose Negative (-ve) Cellobiose Negative (-ve) DNase Positive (+ve) Fructose Positive (+ve) Galactose Positive (+ve) Glucose Positive (+ve) Lactose Positive (+ve) Maltose Positive (+ve) Mannitol Positive (+ve) Mannose Positive (+ve) Raffinose Negative (-ve) Ribose Positive (+ve) Salicin Negative (-ve) Sucrose Positive (+ve) Trehalose Positive (+ve) Xylose Negative (-ve) Enzymatic Reactions Acetoin Production Positive (+ve) Alkaline Phosphatase Positive (+ve) Arginine Dehydrolase Positive (+ve) Hyalurodinase Positive (+ve) Lipase Positive (+ve) Ornithine Decarboxylase Negative (-ve)

Staphylococcus aureus is found in humans in the nose, groin, axillae, perineal area (males), mucous membranes, the mouth, mammary glands, hair, and the intestinal, genitourinary and upper respiratory tracts Footnote 2, Footnote 4, Footnote 18. Many animals act as reservoirs, particularly cows with infected udders

Basic shape of colony: circular Elevation: convex Margin: entire Pigmet production: staphyloxanthin (yellow)

grape-like clusters when viewed through a microscope, and has round, usually golden-yellow colonies

bacteria are then exposed to different antibiotics, including methicillin. S. aureus bacteria that grow well when methicillin is in the culture are termed MRSA

MRSA infections can cause complications such as infection of heart valves (endocarditis), gangrene or death of the soft tissues (necrotizing fasciitis), and bone or joint infections (osteomyelitis or septic arthritis)

Cellulitis, an infection of the skin or the fat and tissues under the skin, usually starting as small red bumps in the skin. It includes redness, swelling of the tissues, warmth, and tenderness.Boils (pus-filled infections of hair follicles)Abscesses (collections of pus in or under the skin)Sty (an infection of an oil gland of the eyelid)Carbuncles (infections larger than an abscess, usually with several openings to the skin)Impetigo (a skin infection with pus-filled blisters)Rash or skin redness (skin appears to be reddish or have red-colored areas)

If the infection is severe or may be spreading into the blood (bacteremia), fevers and shaking chills may occur.

MRSA infection may begin as redness or a rash with a pus-filled pimple or boil. It may progress to an open, inflamed area of skin that may weep pus or drain fluid

A deadly complication of MRSA is a deep infection, necrotizing fasciitis, which causes rapid spread and destruction of human tissues. Some but not all strains of MRSA are more likely to behave like "flesh-eating bacteria." It is impossible to predict which MRSA infection will be "flesh-eating."

Catalase mediates the breakdown of hydrogen peroxide H2O2 into oxygen and water. 

Living in crowded or unsanitary conditions. Outbreaks of MRSA have occurred in military training camps, child care centers and jails.

Warm to the touch Full of pus or other drainage Accompanied by a fever

The staphylococcus aureus bacteria that cause MRSA infections can survive for days to weeks on surfaces. MRSA bacteria can live on surfaces for longer than some other bacteria and viruses because they survive better without moisture. Generally, MRSA bacteria survive for longer on hard surfaces than on soft surfaces.

Pocket of infection that forms at the site of injury. Usually filled with pus. Area surrounding the abscess is usually red, painful and swollen and the skin surrounding the abscess can feel warm to the touch.

Usually results from a scrape or cut in the skin which allows bacteria to enter, although no injury may be apparent. Cellulitis can occur anywhere in the body, but most often occurs on the legs or arms. Symptoms include redness, swelling, and pain at the site of infection.

Lower limbs and upper limbs are the most commonly involved sites

Of 105 necrotizing fasciitis cases during the study period, 18 were caused by monomicrobial S. aureus infection (17%). The median age was 62 years (range, 12-81 years).