Outbreaks of Multidrug-Resistant Shigella sonnei Gastroenteritis Associated with Day Care Centers --- Kansas, Kentucky, and Missouri, 2005

Infection with Shigella sonnei that is resistant to antibiotics commonly used in pediatric practice has become more common during the past decade (1). In 2005, Kansas, Kentucky, and Missouri reported increases in shigellosis cases associated with day care centers caused predominantly by multidrug-resistant (MDR) (i.e., resistant to ampicillin and trimethoprim-sulfamethoxazole [TMP/SMX]) strains of S. sonnei. Pulsed-field gel electrophoresis (PFGE) patterns for isolates from Kansas and Missouri were similar, suggesting a common outbreak in the Kansas City area, whereas isolates from Kentucky had a different pattern. This report describes the investigation of two outbreaks of MDR shigellosis associated with day care centers and reviews measures for prevention and control of S. sonnei infection in these settings. Given the current rates of resistance to antibiotics available to treat children with shigellosis safely, public health measures initiated during shigellosis outbreaks should focus on promoting appropriate handwashing and diapering practices in day care centers.

Shigellosis is a reportable disease in all three states. A confirmed case is defined as illness in a person with S. sonnei isolated from a clinical specimen, and a probable case is defined as clinically compatible symptoms in a person who was epidemiologically linked to a confirmed case.

Case Reports

Kansas City Metropolitan Area (Kansas). During May 1--December 31, 2005, a total of 201 confirmed S. sonnei infections were reported among residents of the Kansas City Metropolitan Area (Kansas) (Figure 1). Median age of patients was 7 years (range: 1--70 years). Among patients aged <10 years, 66 (51%) were female; among patients aged >18 years, 41 (80%) were female. Information about patient exposures to day care settings was not collected. The Kansas Department of Health and Environment Laboratory conducted antimicrobial susceptibility testing on 60 isolates; 53 (88%) isolates were resistant to both ampicillin and TMP/SMX, eight (13%) were resistant to ampicillin/sulbactam, and none were resistant to ceftriaxone, gentamicin, or ciprofloxacin.

Kansas City Metropolitan Area (Missouri). During May 1--December 31, 2005, a total of 645 confirmed and 85 probable shigellosis cases in the Kansas City Metropolitan Area (Missouri) were reported to the Missouri Department of Health and Senior Services (Figure 1). The median age of patients was 6 years (range: 0--67 years). Overall, 532 (74.0%) infections occurred among children aged <10 years; 255 (48%) were among females. Among 157 patients aged >18 years, 117 (74.5%) were female. A total of 42 licensed day care centers each had one or more cases of shigellosis among attendees. Routine surveillance data indicated that 36% of patients or one of their household members had attended a day care center; however, a random sample of 10 patients who were reinterviewed indicated that an estimated 82% of patients or one of their household members might have had exposure to a day care center. Antibiotic susceptibility testing of 28 isolates was performed by the National Antimicrobial Resistance Monitoring System (NARMS) Laboratory; 25 (89%) were resistant to ampicillin and TMP/SMX. No resistance to ceftriaxone, ciprofloxacin, or nalidixic acid was observed.

Kentucky. During May 1--August 31, 2005, a total of 148 confirmed cases of S. sonnei infection were reported in Fayette County (Figure 2), which represented a 42-fold increase above the previous 5-year baseline. The median age of patients was 4 years (range: 0--61 years); among children aged <10 years, 59 (50%) were female. Among adults aged >18 years, 18 (78%) were female. A total of 137 (93%) cases occurred among attendees, their family members, or staff at 16 day care centers in Fayette County. Twelve isolates underwent antimicrobial susceptibility testing at the University of Kentucky; all were resistant to ampicillin and TMP/SMX, and none were resistant to ceftriaxone or ciprofloxacin.

Control Measures

In all three states, local public health agencies conducted case investigations and met with day care center staff to promote handwashing and observe diapering and food preparation practices. In Kansas, local public health agencies used Glo-Germ^™ (DMA International; Moab, Utah) kits to educate students and staff about proper handwashing techniques. All three states require exclusion of children with shigellosis from day care centers until documentation indicates no S. sonnei in two consecutive stool cultures obtained >24 hours apart and >24 hours after completing antibiotic treatment. In Kentucky, four day care centers voluntarily stopped accepting new admissions for 1 week to protect new enrollees in day care centers that experienced ongoing transmission despite intensive measures to modify and monitor hygiene practices. From the earliest stages of the outbreaks, public health alerts describing the outbreak, providing information about shigellosis, and promoting handwashing were distributed to day care centers, schools, and the general public in affected counties in fliers (e.g., distributed through retailers), letters, and press releases. Health-care providers in all three states were informed of local S. sonnei antibiotic-resistance patterns and advised to test and treat patients with shigellosis with appropriate antibiotics during the outbreak. Despite the early implementation of these measures, the outbreaks persisted for several months, lasting through the summer in Kentucky and into early winter in Kansas and Missouri.

Reported by: N Obiesie, MPH, R Flahart, PhD, G Hansen, DVM, J Sexton, C Pursell, Kansas Dept of Health and Environment. TJ Sugg, Lexington-Fayette County Health Dept, Lexington; DA Thoroughman, PhD, KE Humbaugh, MD, Kentucky Dept for Public Health. BP Zhu, MD, CJ Hinkle, JA Rudroff, F Khan, MBBS, S Gladbach, Missouri Dept of Health and Senior Svcs. E Mintz, MD, A Bowen, MD, T Nguyen, MPH, K Joyce, M Omondi, D Jennings, National Center for Zoonotic, Vector-Borne, and Enteric Diseases (proposed); W Arvelo, MD, N Tarkhashvili, MD, T Weiser, MD, A Huang, MD, EIS officers, CDC.

Editorial Note:

In the United States, Shigella species cause an estimated 450,000 cases of gastroenteritis each year (2), mostly among children aged <5 years. S. sonnei is the most common species of laboratory-confirmed Shigella infection in the United States and usually causes an acute, self-limited, diarrheal illness (3). During the past two decades, numerous outbreaks of S. sonnei infection have been associated with day care centers (4). Because few bacteria are required to transmit shigellosis from person to person through the fecal-oral route, shigellosis can propagate in settings with insufficient hygiene practices. Certain states, including the three states in this report, require that children with shigellosis be excluded from day care centers until documentation indicates that they have submitted two consecutive stool specimens that do not yield S. sonnei; however, whether excluding children until stool cultures do not yield Shigella bacteria reduces transmission is unclear. As a result, the control of shigellosis outbreaks associated with day care centers often requires considerable time, effort, and expense from health departments, day care centers, and affected families.

Although antibiotics are not required for this generally mild disease, they are often prescribed to shorten the duration of illness and reduce the infectious period, particularly in day care center attendees and food handlers (5). Surveillance data for antimicrobial resistance among all S. sonnei isolates received by NARMS during 1999--2003 indicated that 80% of the isolates were resistant to ampicillin and 47% to TMP/SMX; 38% were resistant to both drugs (6). In the two outbreaks described in this report, resistance to both ampicillin and TMP/SMX was 89%, complicating shigellosis treatment in these communities.

Although ampicillin and TMP/SMX have been the drugs of choice for treatment of shigellosis, current resistance patterns limit the use of these antibiotics. Fluoroquinolones are an effective alternative for adults but are not approved by the Food and Drug Administration for shigellosis treatment in children aged <18 years. Macrolides, particularly azithromycin, also are recommended by the American Academy of Pediatrics for treatment of shigellosis, although data about clinical effectiveness are limited, and no standardized guidelines for monitoring azithromycin resistance among shigellae are currently available (7). In addition, azithromycin is excreted in stool over an extended period. Follow-up stool cultures will not yield accurate results until azithromycin is no longer being excreted; therefore, the time required for follow-up testing might be prolonged (8).

The emergence of MDR shigellosis highlights the importance of prevention and rapid control of outbreaks. Appropriate handwashing and diapering practices are critical in minimizing the transmission of shigellosis in day care centers (9). Scheduling handwashing sessions on arrival at the day care center, before meals, or after playing outdoors; supervising handwashing among young children; and eliminating water play areas have been used to reduce the spread of shigellosis within day care centers and to the community (10). Forming cohorts of convalescing children (e.g., asymptomatic children who are culture-positive), by allowing them to attend the day care center but excluding them from interacting with other well children, also has been used to control outbreaks associated with day care centers; however, state regulations in these three states do not allow such measures. Given the current rates of resistance to ampicillin and TMP/SMX, the uncertain safety of administering fluoroquinolones to children, the difficulties in monitoring azithromycin resistance, the absence of an appropriate vaccine, and the unclear benefits of exclusion policies in day care centers, public health measures should focus on prevention of shigellosis outbreaks through appropriate hygiene practices and, where possible and allowed by state regulations, forming cohorts of convalescing children in day care centers.

References

1. S Sivapalasingam, J Nelson, K Joyce, M Hoekstra, F Angulo, E Mintz. High prevalence of antimicrobial resistance among Shigella isolates in the United States tested by the national antimicrobial resistance monitoring system from 1999 to 2002. Antimicrob Agents Chemother 2006; 50:49--54.
2. P Mead, L Slutsker, V Dietz, et al. Food-related illness and death in the United States. Emerg Infect Dis 1999;5:607--25.
3. CDC. Laboratory-confirmed Shigella surveillance annual summaries. Available at http://www.cdc.gov/ncidod/dbmd/phlisdata/shigtab/2004/shigellaannualsummary2004.pdf.
4. CDC. Current trends community outbreaks of shigellosis---United States. MMWR 1990;39:509--13, 519.
5. Mahoney FJ, Farley TA, Burbank DF, Leslie NH, McFarland LM. Evaluation of an intervention program for the control of an outbreak of shigellosis among institutionalized persons. J Infect Dis 1993; 168:1177--80.
6. National Antimicrobial Resistance Monitoring System (NARMS). Human isolates final report, 2003. Available at http://www.cdc.gov/narms/annual/2003/NARMS2003annualreport.pdf.
7. Jain SK, G Amita, G Brian, D James, S George. Antimicrobial-resistant Shigella sonnei: limited antimicrobial treatment options for children and challenges of interpreting in vitro azithromycin susceptibility. Pediatr Infect Dis J 2005;24:494--7.
8. L Murray, N Chesanow, H Fleming, eds. Physician's Desk Reference 2005. Montvale, New Jersey: Thompson PDR; 2006:2665--77.
9. E Gangarosa. A community-focused strategy for the control of day-care center shigellosis. Am J Public Health 1995;85:763--4.
10. Hoffman RE, Shillam PJ. The use of hygiene, cohorting, and antimicrobial therapy to control an outbreak of shigellosis. Am J Dis Child 1990;144:219--21.

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Date last reviewed: 10/4/2006