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Agent

Streptococcus pyogenes Group A (β-hemolytic) streptococci (GAS), is an aerobic, gram-positive extracellular bacterium. It is made up of non-motile, non-sporing cocci that are less than 2 µm in length and that form chains and large colonies greater than 0.5 mm in size. It has a β-hemolytic growth pattern on blood agar and there are over 60 different strains of the bacterium.

Disease/Infection

pyogenes is responsible for a wide array of infections, including streptococcal sore throat, strep throat, pharyngitis, scarlet fever, impetigo, erysipelas, puerperal fever, necrotizing fasciitis, toxic shock syndrome, septicemia, acute rheumatic fever, acute post-streptococcal glomerulonephritis, and gas gangrene.

Pathogenicity

There are at least 517,000 deaths globally each year due to severe S. pyogenes infections and rheumatic fever disease alone causes 233,000 deaths. 1,800 invasive S. pyogenes disease-related deaths are reported in the USA yearly, necrotizing fasciitis kills about 30% of patients and streptococcal toxic shock syndrome has a mortality rate of 30-70%. Different clinical manifestations of this bacterium are more common in different parts of the world.

  • Special Populations at Risk
    Outside of the laboratory, crowding and poor hygiene increase the chance of an outbreak of GAS infections.

Biosafety Information

Risk Group/BSL
Risk Group 2
Biosafety Lab 2 Practices

Modes of Transmission

Transmission
Skin Exposure (Needlestick, bite, or scratch):Yes, hand contact with nasal discharge and skin contact with impetigo lesions
Mucous Membrane Splash to Eye(s), Nose or Mouth:Yes, direct contact with mucosal tissue
Inhalation:Yes, exposure to infected aerosols
Ingestion:Yes, through contaminated food sources but rare

The pathogen can be found in its carrier state in the anus, vagina, skin and pharynx and contact with these surfaces can spread the infection

Host Range/Reservoir
pyogenesis an exclusively human pathogen.

Symptoms
Symptoms vary depending on the type of infection and can affect a variety of organ systems. For streptococcal sore throat, symptoms are characterized by fever, enlarged tonsils, tonsillar exudate, sensitive cervical lymph nodes and malaise. Scarlet fever manifestations include fever and a pink-red rash. Impetigo will result in infection of the superficial layers of skin. Acute rheumatic fever will result in joint inflammation, carditis, and nervous system complications. Post—streptococcal glomerulonephritis causes hematuria, fever, edema, and hypertension. More serious complications may include severe skin infections and subsequent tissue destruction.

Incubation Period
The incubation period is usually 1-3 days.

Viability
This bacteria is susceptible to 1% sodium hypochlorite, 4% formaldehyde, 2% glutaraldehyde, 70% ethanol, 70% propanol, 2% peracetic acid, 3-6% hydrogen peroxide and 0,16% iodine. Bacteria are susceptible to moist heat (121 ºC for at least 15 minutes) and dry heat (170 ºC for at least 1 hour).

Survival Outside Host
The bacterium can survive on a dry surface for 3 days to 6.5 months. In contaminated food: found to survive in ice cream (18 days), raw and pasteurized milk at 15-37 ºC (96 hrs.), room temperature butter (48 hrs.), and neutralized butter (12-17 days). GAS has been found to last several days in cold salads at room temperature.

Information for Lab Workers

Laboratory PPE

Personal protective equipment includes but is not limited to laboratory coats or gowns, disposable gloves, and safety glasses.

Containment

Research should be conducted using Biosafety Level 2 practices, equipment, and facility design.

In Case of Exposure/Disease

  • For injuries in the lab which are major medical emergencies (heart attacks, seizures, etc…):
    • Medical Campus: call or have a coworker call the Control Center at 617-414–4144.
    • Charles River Campus: call or have a coworker call campus security at 617-353-2121.
      You will be referred to or transported to the appropriate health care location by the emergency response team.
  • For lab exposures (needle sticks, bite, cut, scratch, splash, etc…) involving animals or infectious agents, or for unexplained symptoms or illness call the ROHP 24/7 hour number (1-617-358-ROHP (7647); or, 8-ROHP (7647) if calling from an on-campus location) to be connected with the BU Research Occupational Health Program (ROHP) medical officer. ROHP will refer you to the appropriate health care location.
  • Under any of these scenarios, always inform the physician of your work in the laboratory and the agent(s) that you work with.
  • Provide the wallet-size agent ID card to the physician.

Vaccination

None

Information for First Responders/Medical Personnel

Public Health Issues

Person to person transmission is common. The bacterium can remain in the body in its carrier state without causing illness in the host for weeks or months and is transmissible in this state. In patients with strep pharyngitis, patients are infective in acute phase of the illness, usually 7-10 days, and for one week afterwards. With antibiotics, infective period is decreased to 24 hours. Standard precautions should be used. If cluster of cases is suspected, transmission based precautions are utilized.

Diagnosis/Surveillance

Monitor for symptoms. Confirm infection by bacteriological and serological testing, latex bead agglutination, fluorescent antibody staining or ELISA.

First Aid/Post Exposure Prophylaxis

Post exposure prophylaxis with antibiotics should be considered.

Perform one of the following actions:

Skin Exposure (Needlestick or scratch):Immediately go to the sink and thoroughly wash the wound with soap and water for 15 minutes. Decontaminate any exposed skin surfaces with an antiseptic scrub solution.
Mucous Membrane Splash to Eye(s), Nose or Mouth:Exposure should be irrigated vigorously.
Splash Affecting Garments:Remove garments that may have become soiled or contaminated and place them in a double red plastic bag.

Percutaneous inoculation of GAS carries a significant risk for developing invasive infections, with the extreme instances of necrotizing fasciitis and/or streptococcal toxic shock syndrome. Mucous membrane inoculation would be most concerning to the eyes. These injuries may appear benign early, but without proper management may evolve into serious infections even with a small inoculum.

Treatment

If any signs or symptoms of infection, admission should be considered, with Infectious Disease consult. Complete total of 2 doses of IV antibiotic (ceftriaxone 1g IV q24H or daptomycin 4 mg/kg IV q24h) before transitioning to oral antibiotics to complete a total of 7-10 days of treatment.

After IV course, preferred oral antibiotics would be cephalexin 500mg PO q12h (if given ceftriaxone IV); clindamycin 450mg PO q8h or levofloxacin 750mg PO q24h (if intolerant of penicillins and/or cephalosporins).

References

Public Health Agency of Canada; http://www.phac-aspc.gc.ca/lab-bio/res/psds-ftss/strep-pyogenes-eng.php

CDC BMBL: http://www.cdc.gov/biosafety/publications/bmbl5/BMBL.pdf

Revised: 8/10/2012