Managing a Hidden Reservoir: Aggressive Measures to Control the Resurgence of a Large Outbreak of Invasive Group A Streptococcus in a Skilled Nursing Facility

BACKGROUND:  In November 2011, the Georgia Department of Public Health (GDPH) partnered with the Centers for Disease Control and Prevention (CDC) and the local health department to investigate an outbreak of 11 cases of invasive group A Streptococcus (GAS) between June 2009 and October 2011 in a 240-bed skilled nursing facility (SNF).  This included additional case finding, an infection control review, case-control study, and GAS carriage study. Residents and staff with positive cultures received antibiotic treatment.  However, 4 new invasive GAS cases were detected by GDPH from March 24-May 19, 2012.

METHODS:  Additional case finding was performed through review of microbiology laboratory results at two referral hospitals.  To detect persistent carriage among SNF residents, we cultured any non-surgical wounds and the oropharynx of residents who were recent cases or who had positive cultures during the November carriage study.  Aggressive efforts were made to treat all staff and residents with either an intramuscular injection of penicillin + 4 days of oral rifampin, or a 10-day course of oral cephalexin to eradicate possible carriage.  Throat cultures were performed on those who declined or had contraindications to antibiotics.  Until culture results were negative, untreated residents were placed on contact precautions and untreated staff members were furloughed.  Follow-up throat and wound cultures were performed on residents who: 1) had a positive wound culture prior to antibiotic treatment; 2) did not receive antibiotics during the facility-wide treatment period, or 3) were newly admitted to the facility during the treatment period.  Emm sequence typing was performed on GAS isolates obtained from invasive cases and from throat and wound screening cultures.

RESULTS:  Case finding identified 2 non-invasive cases in addition to the 4 invasive cases. Four residents had GAS-positive wound cultures during pre-treatment testing. All GAS isolates tested were emm type 11, matching cases from the previous investigation.  During treatment, 80% of employees and 75% of residents received penicillin/rifampin, 18% of employees and 23% of residents received cephalexin, and only 2% of each received throat swabs instead of antibiotics.  Those who did not receive antibiotics had negative cultures.  All follow-up cultures at 5 weeks were negative.  No further cases of invasive GAS have occurred among facility residents since May 2012. 

CONCLUSIONS:  Facility-wide prophylactic antibiotic treatment was an aggressive but necessary measure to stop this prolonged and persistent outbreak of invasive GAS.  High treatment rates were achieved through partnership with clinical and administrative leadership of the SNF.