Media for Staphylococcus Aureus Detection
Staphylococcus aureus is frequently a part of our skin flora but is also a cause of a broad range of illnesses. Current studies report a remarkable increase of Methicillin Resistant Staphylococcus aureus (MRSA) over recent years.
Staphylococci may be airborne and can occur in both animals and humans, in sewage, water, milk or food, and on environmental surfaces or food equipment. It is still one of the five most common causes of nosocomial infections, often causing postsurgical wound infections. Consequently, it poses a major concern in hospitals, especially in regard to MRSA, methicillin-resistant Staphylococcus aureus.
Staphylococcus aureus is an invasive pathogen that can cause disease in almost any tissue or organ in the human body, primarily in compromised individuals. Staphylococcal infections were treated using penicillin, but over the years this pathogen developed resistance to penicillin by building penicillinase. Methicillin was the next drug of choice as it is not cleaved by the penicillinase. While methicillin is very eff ective in treating most Staphylococcus infections, some strains have developed resistance to methicillin by production of penicillin-binding protein, and can no longer be killed by this antibiotic. These resistant bacteria are called Methicillin Resistant Staphylococcus aureus (MRSA)1. Patients with breaks in their skin due to wounds, indwelling catheters or burns are at high risk of developing MRSA infection 2. Spread of MRSA infections can be controlled to a great extent by maintaining personal hygiene after interaction with an MRSA-infected person1.
Today there are many innovative solutions to detect MRSA. We strongly support the microbiologist with a selective chromogenic HiCrome MeReSa Agar for detection of MRSA from clinical isolates and other samples. The proprietary chromogenic mixture incorporated in the medium is specifi cally cleaved by S. aureus to give bluish-green colonies on this medium and can be clearly diff erentiated from other species. The medium is made selective for MRSA by the addition of methicillin.
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Foods that are frequently associated with staphylococcal food poisoning include meat and egg products, milk and dairy products, and various other products that may contain these food ingredients. Processes in the food industry that are kept at slightly elevated temperatures must guard against staphylococcal food poisoning, one of the leading causes of gastroenteritis. The food poisoning is due to the presence of staphylococcal enterotoxins produced by Staphylococcus aureus in the food.
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. S. aureus produce diverse enzymes such as staphylokinase (coagulase), proteases, phopshatase, a lipase, a deoxyribonuclease (DNase) and a fatty acid modifying enzyme (FAME). The majority of clinical isolates of S. aureus express special surface polysaccharide and protein A. Diff erentiation and identifi cation of S. aureus can be made based on these biochemical characteristics. More details may be found in the ID flow chart (Figure 2), the table of kits and tests (Table 1), and the table listing media for the differentiation of Staphylococcus aureus (Table 2).
Figure 2.ID flow chart for Staphylococus aureus
Table 1 and Table 2 specify characteristics which kits and tests utilise for the identification of S. aureus.
| Kit or Test | Cat. No. | Testing features |
|---|---|---|
| Catalase Test (Hydrogen peroxide 3%) | 88597 | Testing of catalase production |
| Coagulase Test (Slide) | 75832 | Detection of coagulase |
| Coagulase Test (Tubes) | 74226 | “ |
| Oxidase Reagent acc. Gaby-Hadley A + Oxidase Reagent acc. Gaby-Hadley B | 07345 07817 | Checking presence of Oxidase |
| Oxidase Reagent acc. Gordon-McLeod | 18502 | “ |
| Oxidase Strips | 40560 | “ |
| Oxidase Test | 70439 | “ |
| Staphylo Monotec test kit Plus | 50448 | Coagulase and protein A can be detected in one step (increased sensitivity and specificity compared to the previous Staphylo Monotec test kit, resulting in increased detection of MRSA) |
| Identification Media | Cat. No. | Testing features |
|---|---|---|
| Baird Parker Agar Supplements: Egg-Yolk Tellurite Emulsion (75208) or RPF Supplement (05939) | 11705 | Detection of lipolytic and proteolytic activity, ability to reduce tellurite to metallic tellurium (EN-ISO 6888-1: 1999); with RPF Supplement the coagulase activity and the ability to reduce tellurite is detected (EN-ISO 6888-2:2000) |
| Blood Agar Supplement: defibrinated blood | 70133 | Detection of β-hemolysis |
| Blood Agar No. 2 Supplement: defibrinated blood | B1676 | " |
| Bromo Thymol Blue (B.T.B.) Lactose Agar | B3676 | Differentiated by their ability to grow at a high pH and in the presence of bromo thymol blue (golden yellow colonies) |
| CLED Agar | 55420 | Detection of lactose fermentation |
| Deoxyribonuclease Test Agar | 30787 70136 | Detection of deoxyribonuclease activity |
| DNase Test Agar with Toluidine Blue | D2560 | " |
| Giolitti Cantoni Broth | 48905 | Ability to reduce tellurite to tellurium and selective conditions |
| HiCrome™ Aureus Agar Base Supplement: Egg-Yolk Tellurite Emulsion (75208) | 05662 | Testing for ability to reduce tellurite to metallic tellurium and detection of lipase and protease by chromogenic substrate; brown-black colonies |
| HiCrome™ MeReSa Agar Base Supplement: MRSA Selective Supplement (51387) | 90923 | Detection by chromogenic substrate mixture specifically cleaved by S. aureus; selective to MRSA; MRSA give bluish-green colonies |
| China Blue Lactose Agar | 22520 | Detection of lactose fermentation |
| Mannitol Salt Agar | 63567 09166 (plates) | Detection of mannitol fermentation in high sodium chloride concentration |
| Nutrient Gelatin | 70151 | Detection of gelatin-liquefying (proteolytic enzymes) |
| Phenolphthalein Phosphate Agar | 68879 | Phosphatase detection; pink-red colonies |
| Spirit Blue Agar Supplement: Lipase Substrate (see data sheet) | S4306 | Detection and enumeration of lipolytic activity |
| Staphylococcus Agar | 70193 | Detection of salt tolerance, pigmentation, D-mannitol utilisation and gelatin liquefaction |
| Tributyrin Agar Supplement: Neutral Tributyrin (91010) | 91015 | Detection and enumeration of lipolytic activity |
| Vogel-Johnson Agar Supplements: Potassium Tellurite 1% (17774) | 70195 | Checking for ability to reduce tellurite to tellurium and ability to ferment mannitol |
References
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