Large, childcare-associated Shigellosis outbreak clues researchers into best treatment, management strategies

Enforcing simple hygiene strategies in childcare centers can help limit Shigellosis transmission and may combat growing antimicrobial-resistance patterns among these organisms, according to CDC and Missouri State Department of Health and Senior Services officials who investigated a Shigella sonnei outbreak that affected 693 people and spanned 44 licensed daycare facilities in northwest Missouri from May to October 2005.

Surveillance data revealed that 300 of the 639 people who became ill reported childcare-center exposure, with 176 patients reporting either employment or attendance at a childcare center, and 112 reporting household contact with a childcare-center employee or attendee.

Childcare centers that lacked a hand-washing station in every room, and those that enrolled diapered children without providing a diapering station in every room were at greater risk for spreading the disease among attendees, according to a case-control comparison.

Current state regulations do not permit the use of alcohol-based hand sanitizers in Missouri childccare centers, according to the researchers, despite evidence that these products can decrease enteric illness and complement hand-washing policies.

Several additional Missouri health requirements also have officials concerned. School exclusion policies require two consecutive negative cultures for children to return to childcare, rather than a single negative culture or symptom resolution. The researchers believe this policy may “implicitly encourage antimicrobial treatment in children who attend daycare centers and may result in unnecessary adverse drug events in children and increase antimicrobial resistance among enteric and respiratory pathogens.”

Among the 31 outbreak isolates tested for antimicrobial susceptibility, 95% were resistant to ampicillin, 90% were resistant to trimethroprim-sulfamethoxazole (TMP/SMX) and 90% were resistant to both antibiotics — the two most commonly recommended for empiric treatment in children until recently.

During this outbreak azithromycin was used most often, administered to 44% (n=92) of the 210 children aged 18 or younger who were prescribed an antibiotic. Cephalosporin was the next most commonly prescribed (27%, n=57), followed by fluoroquinolones (5%, n=11), ampicillin (2%, n=3) and an unknown antimicrobial (7%, n=15).

“Given the current frequency of resistance to ampicillin and trimethroprim sulfamethoxazole among S. sonnei strains, the uncertain safety of administering fluoroquinolones to children, the difficulties in monitoring azithromycin resistance and the lack of an appropriate vaccine, public health measures should focus on prevention of shigellosis outbreaks through appropriate hygiene practices and, where possible and allowed by state regulations cohorting convalescing children in daycare centers,” the researchers wrote.

Arvelo W. Pediatr Infect Dis J. 2009;28:976-980.

Two enteric organisms you don’t want to see in a childcare center are Escherichia coli O157:H7 and shigella. This large outbreak investigation highlights several important aspects about shigella — the low inoculum size necessary for person to person transmission, ease of spread within and outside child care centers, need for appropriate infrastructure within childcare centers to support infection control measures, and knowledge of antimicrobial susceptibility patterns. The CDC’s National Antimicrobial Resistance Monitoring System supports the authors’ comment that ampicillin and TMP/SMX are no longer the drugs of choice for shigella infections. Short course azithromycin, ciprofloxacin and expanded spectrum cephalosporins are recommended when treatment is deemed necessary, but susceptibility patterns need to be monitored.

– Larry K. Pickering, MD

Centers for Disease Control and Prevention