Staphylococcus aureus (S. aureus)

Characteristics
Morphology	Gram-positive, catalase positive cocci belonging to the Staphylococcaceae family. Approximately 0.5-1.5 µm in diameter, nonmotile, non-spore-forming, facultative anaerobes (with the exception of S. aureus anaerobius) that usually form in clusters (grape-like). Many strains produce staphylococcal enterotoxins, the superantigen toxic shock syndrome toxin (TSST-1), and exfoliative toxins. Increased antibiotic resistance has led to methicillin-resistant Staphylococcus aureus (MRSA) becoming a, increased risk
Growth Conditions	Tryptic Soy Broth or LB Broth, at a temperature range between 15° to 45°C and at NaCl concentrations up to 15%. Part of human flora, and are primarily found in the nose and skin.

Characteristics

Morphology

Gram-positive, catalase positive cocci belonging to the Staphylococcaceae family. Approximately 0.5-1.5 µm in diameter, nonmotile, non-spore-forming, facultative anaerobes (with the exception of S. aureus anaerobius) that usually form in clusters (grape-like). Many strains produce staphylococcal enterotoxins, the superantigen toxic shock syndrome toxin (TSST-1), and exfoliative toxins. Increased antibiotic resistance has led to methicillin-resistant Staphylococcus aureus (MRSA) becoming a, increased risk

Growth
Conditions

Tryptic Soy Broth or LB Broth, at a temperature range between 15° to 45°C and at NaCl concentrations up to 15%. Part of human flora, and are primarily found in the nose and skin.

Health Hazards
Host Range	Humans, wild and domestic animals, including cows
Modes of Transmission	Ingestion of food containing enterotoxins, person-to-person transmission occurs through contact with a purulent lesion or with a carrier, case reports of Laboratory-associated infections include nasal colonization (can lead to auto-infection) and minor skin infections.
Signs and Symptoms	Accidental ingestion: violent onset of severe nausea, cramps, vomiting, and diarrhea if preformed enterotoxin is present Surface infections: impetigo, folliculitis, abscesses, boils, infected lacerations Systemic infections: onset of fever, headache, myalgia, can progress to endocarditis, meningitis, septic arthritis, pneumonia, osteomyelitis, sepsis
Infectious Dose	Unknown, but will vary depending on the strain
Incubation Period	30 minutes-8 hours when consuming contaminated food with enterotoxin. Otherwise, typically 4-10 days; disease may not occur until several months after colonization of mucosal surfaces.

Medical Precautions/Treatment
Prophylaxis	Hand-hygiene; Elimination of nasal carriage by using topical mupirocin. Mupirocin also eliminates transient hand carriage by eliminating the mucosal reservoir
Vaccines	None publically available
Treatment	Incision and drainage for localized skin infections; antibiotic therapy for severe infections; Many strains resistant to antibiotics; Sensitivity must be determined for each strain
Surveillance	Monitor for signs of food poisoning when ingestion occurs. Monitor for skin inflammation; isolation of organism from wound, blood, CSF, or urine. Can be diagnosed using ELISA, reverse passive latex agglutination, or PCR.
GWU Requirements	Report all incidents to the Office of Risk Management as well as the Office of Research Safety (ORS) IMMEDIATELY FOLLOWING THE OCCURRENCE.

Containment
BSL-2	Risk Group 2 classification is applied to C. difficile. BSL-2 practices, containment equipment, and facilities are recommended for all activities utilizing known or potentially infected clinical materials or cultures. All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC).
ABSL-2	ABSL-2 facilities are recommended for studies utilizing infected laboratory animals.
BSL-3	For activities with high potential for aerosol or droplet production and activities using large quantities of S. aureus
ABSL-3	For all procedures with high potential for aerosol or droplet production through animal exposure

Spill Procedures
Small Spills (<1 liter)	If the spill occurred inside a biological safety cabinet, close the sash and allow the cabinet to operate for 15 minutes before continuing with the spill cleanup. S. aureus can become aerosolized and contaminate surrounding surfaces, caution should be taken during a spill outside of a BSC. Leave the room immediately and allow the aerosols to dissipate for 15 minutes. Notify others working in the lab. Don appropriate PPE. Cover area of the spill with paper towels or any absorbent material and apply an EPA registered disinfectant effective against Gram-positive bacteria (ethanol, bleach, glutaraldehyde), working from the perimeter towards the center. Allow 30 minutes of contact time before disposal and cleanup of spill materials.
Large Spills	Alert lab personnel in the laboratory to the spill and keep people out of the area to prevent spread of the contamination. Check if you have been contaminated or if any of your PPE has been breached. If so follow exposure procedures. Remove any contaminated clothing and place it the biohazard waste. Wash your hands and post a sign on the door. Notify your supervisor of the incident and call ORS (4-8258) for assistance. If the situation involves an imminently life-threatening injury or has catastrophic potential, call 911.

Spill Procedures

Small Spills (<1 liter)

If the spill occurred inside a biological safety cabinet, close the sash and allow the cabinet to operate for 15 minutes before continuing with the spill cleanup.

S. aureus can become aerosolized and contaminate surrounding surfaces, caution should be taken during a spill outside of a BSC. Leave the room immediately and allow the aerosols to dissipate for 15 minutes. Notify others working in the lab. Don appropriate PPE. Cover area of the spill with paper towels or any absorbent material and apply an EPA registered disinfectant effective against Gram-positive bacteria (ethanol, bleach, glutaraldehyde), working from the perimeter towards the center. Allow 30 minutes of contact time before disposal and cleanup of spill materials.

Large Spills

Alert lab personnel in the laboratory to the spill and keep people out of the area to prevent spread of the contamination. Check if you have been contaminated or if any of your PPE has been breached. If so follow exposure procedures. Remove any contaminated clothing and place it the biohazard waste. Wash your hands and post a sign on the door. Notify your supervisor of the incident and call ORS (4-8258) for assistance. If the situation involves an imminently life-threatening injury or has catastrophic potential, call 911.

Exposure Procedures
Mucus Membrane	Flush eyes, mouth or nose for 15 minutes at eyewash station.
Other Exposure	For an area not protected by skin, wash with soap and water for 15 minutes (open wounds, sores, etc.), and a minimum of 20 seconds of soap and water for areas with intact skin.
Reporting	Report ALL injuries to the PI immediately and reported to the Office of Risk Management at [email protected] IMMEDIATELY FOLLOWING THE OCCURRENCE. Exposures that involve a bloodborne-pathogen or recombinant DNA also need to be reported to the Office of Research Safety at [email protected]. If the injury requires immediate medical attention, call GWPD at 202-994-6111 or call 911.
Medical Monitoring	Seek immediate medical evaluation, treatment, and post exposure follow-up at the Employee Health Office at GWU Hospital (900 23rd St., NW, Suite G-1090, Phone: 202-715-4275). Students should go to the Students Health Office at Marvin Center. After hours treatment can be received at the GWU hospital emergency room.

Stability
Disinfection	Susceptible to 10% bleach, 70% ethanol, 2% glutaraldehyde.
Inactivation	Sensitive to dry heat treatment of 160-170oC for at least an hour, but not to moist heat treatment
Survival Outside Host	Carcass and organs – 42 days; Skin – 30 minutes to 38 days; meat products – 60 days; floor – less than 7 days; glassware – 46 hours; sunlight – 17 hours; UV light – 7 hours

Personal Protective Equipment (PPE)
Minimum PPE Requirements	At minimum, personnel are required to don gloves, closed toed shoes, lab coat, and appropriate face and eye protection prior to working with S. aureus. Additional PPE may be required depending on lab specific SOPs.
Additional Precautions	Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Wash hands with soap and water after removing gloves.

References
CDC (https://www.cdc.gov/hai/organisms/staph.html) BMBL 6th Edition (https://www.cdc.gov/labs/BMBL.html) Growth and Laboratory Maintenance of Staphylococcus aureus (https://currentprotocols.onlinelibrary.wiley.com/doi/10.1002/9780471729…) Canadian PHAC (https://www.canada.ca/en/public-health/services/laboratory-biosafety-bi…) EPA (https://www.epa.gov/system/files/documents/2021-12/2021.12.02.listh_.pdf)

References