Jennifer M. Nelson

Fluoroquinolone-Resistant Campylobacter Species and the Withdrawal of Fluoroquinolones from Use in Poultry: A Public Health Success Story

Campylobacter species cause 1.4 million infections each year in the United States. Fluoroquinolones (e.g., ciprofloxacin) are commonly used in adults with Campylobacter infection and other infections. Fluoroquinolones (e.g., enrofloxacin) are also used in veterinary medicine. Human infections with fluoroquinolone-resistant Campylobacter species have become increasingly common and are associated with consumption of poultry. These findings, along with other data, prompted the US Food and Drug Administration to propose the withdrawal of fluoroquinolone use in poultry in 2000. A lengthy legal hearing concluded with an order to withdraw enrofloxacin from use in poultry (effective in September 2005). Clinicians are likely to continue to encounter patients with fluoroquinolone-resistant Campylobacter infection and other enteric infection because of the continued circulation of fluoroquinolone-resistant Campylobacter species in poultry flocks and in persons returning from foreign travel who have acquired a fluoroquinolone-resistant enteric infection while abroad. Judicious use of fluoroquinolones and other antimicrobial agents in human and veterinary medicine is essential to preserve the efficacy of these important chemotherapeutic agents.

Antimicrobial resistance among Campylobacter strains, United States, 1997-2001.

We summarize antimicrobial resistance surveillance data in human and chicken isolates of Campylobacter. Isolates were from a sentinel county study from 1989 through 1990 and from nine state health departments participating in National Antimicrobial Resistance Monitoring System for enteric bacteria (NARMS) from 1997 through 2001. None of the 297 C. jejuni or C. coli isolates tested from 1989 through 1990 was ciprofloxacin-resistant. From 1997 through 2001, a total of 1,553 human Campylobacter isolates were characterized: 1,471 (95%) were C. jejuni, 63 (4%) were C. coli, and 19 (1%) were other Campylobacter species. The prevalence of ciprofloxacin-resistant Campylobacter was 13% (28 of 217) in 1997 and 19% (75 of 384) in 2001; erythromycin resistance was 2% (4 of 217) in 1997 and 2% (8 of 384) in 2001. Ciprofloxacin-resistant Campylobacter was isolated from 10% of 180 chicken products purchased from grocery stores in three states in 1999. Ciprofloxacin resistance has emerged among Campylobacter since 1990 and has increased in prevalence since 1997.

Public Health Consequences of Use of Antimicrobial Agents in Food Animals in the United States

The use of antimicrobial agents in food animals has caused concern regarding the impact these uses have on human health. Use of antimicrobial agents in animals and humans results in the emergence and dissemination of resistant bacteria. Resistant bacteria from food animals may be passed through the food chain to humans resulting in resistant infections. Increasing resistance to antimicrobial agents that are important in the treatment of human diseases, such as fluoroquinolones and third-generation cephalosporins for the treatment of Salmonella and Campylobacter infections, has significant public health implications. Efforts to mitigate the effects of increasing resistance require collaboration by several partners, including the farming, veterinary, medical, and public health communities.

Prolonged Diarrhea Due to Ciprofloxacin-Resistant Campylobacter Infection

BACKGROUND Campylobacter causes >1 million infections annually in the United States. Fluoroquinolones (e.g., ciprofloxacin) are used to treat Campylobacter infections in adults. Although human infections with ciprofloxacin-resistant Campylobacter have become increasingly common, the human health consequences of such infections are not well described. METHODS A case-control study of persons with sporadic Campylobacter infection was conducted within 7 FoodNet sites during 1998-1999. The E-test system (AB Biodisk) was used to test for antimicrobial susceptibility to ciprofloxacin; ciprofloxacin resistance was defined as a ciprofloxacin minimum inhibitory concentration of > or =4 microg/mL. We conducted a case-comparison study of interviewed persons who had an isolate tested. RESULTS Of 858 isolates tested, 94 (11%) were ciprofloxacin resistant. Among 290 persons with Campylobacter infection who did not take antidiarrheal medications, persons with ciprofloxacin-resistant infection had a longer mean duration of diarrhea than did persons with ciprofloxacin-susceptible infection (9 vs. 7 days [P=.04]). This difference was even more pronounced among the 63 persons who did not take antidiarrheal medications or antimicrobial agents (12 vs. 6 days [P=.04]). In a multivariable analysis-of-variance model, the persons with ciprofloxacin-resistant infection had a longer mean duration of diarrhea than did the persons with ciprofloxacin-susceptible infection (P=.01); this effect was independent of foreign travel. The association between ciprofloxacin resistance and prolonged diarrhea is consistent across a variety of analytical approaches. CONCLUSIONS Persons with ciprofloxacin-resistant Campylobacter infection have a longer duration of diarrhea than do persons with ciprofloxacin-susceptible Campylobacter infection. Additional efforts are needed to preserve the efficacy of fluoroquinolones.

High Prevalence of Antimicrobial Resistance among Shigella Isolates in the United States Tested by the National Antimicrobial Resistance Monitoring System from 1999 to 2002

ABSTRACT Shigella spp. infect approximately 450,000 persons annually in the United States, resulting in over 6,000 hospitalizations. Since 1999, the National Antimicrobial Resistance Monitoring System (NARMS) for Enteric Bacteria has tested every 10th Shigella isolate from 16 state or local public health laboratories for susceptibility to 15 antimicrobial agents. From 1999 to 2002, NARMS tested 1,604 isolates. Among 1,598 isolates identified to species level, 1,278 (80%) were Shigella sonnei, 295 (18%) were Shigella flexneri, 18 (1%) were Shigella boydii, and 7 (0.4%) were Shigella dysenteriae. Overall, 1,251 (78%) were resistant to ampicillin and 744 (46%) were resistant to trimethoprim-sulfamethoxazole (TMP-SMX). Prevalence of TMP-SMX- or ampicillin- and TMP-SMX-resistant Shigella sonnei isolates varied by geographic region, with lower rates in the South and Midwest regions (TMP-SMX resistance, 27% and 30%, respectively; ampicillin and TMP-SMX resistance, 25% and 22%, respectively) and higher rates in the East and West regions (TMP-SMX resistance, 66% and 80%, respectively; ampicillin and TMP-SMX resistance, 54% and 65%, respectively). Nineteen isolates (1%) were resistant to nalidixic acid (1% of S. sonnei and 2% of S. flexneri isolates); 12 (63%) of these isolates had decreased susceptibility to ciprofloxacin. One S. flexneri isolate was resistant to ciprofloxacin. All isolates were susceptible to ceftriaxone. Since 1986, resistance to ampicillin and TMP-SMX has dramatically increased. Shigella isolates in the United States remain susceptible to ciprofloxacin and ceftriaxone.

A Large, Multiple-Restaurant Outbreak of Infection with Shigella flexneri Serotype 2a Traced to Tomatoes

BACKGROUND Foodborne outbreaks of Shigella infection are uncommon and tomatoes are an unusual vehicle. We describe a large, multiple-restaurant outbreak of Shigella flexneri serotype 2a infection that was associated with tomatoes. METHODS We conducted nationwide surveillance and a case-control study, collected fecal specimens for culture, and measured the survival of the outbreak strain of S. flexneri in tomatoes. RESULTS We interviewed 306 of 886 ill restaurant patrons and 167 control subjects. Matched univariate analysis showed that several food items were associated with illness, but only tomatoes remained significant in multivariate models. Illness peaked at each restaurant within 24 h after the arrival of hand-sorted bruised and overripe tomatoes from a new distributor; all patient isolates that were tested were indistinguishable by PFGE. Sliced tomatoes from the distributor were inoculated with the outbreak strain, and viable S. flexneri were recovered for 72 h. CONCLUSION To prevent such outbreaks, persons with shigellosis should be excluded from handling food at all points along the distribution chain.

β-Lactam Resistance and Enterobacteriaceae, United States

Extended-spectrum cephalosporins (ESC) are an important drug class for treating severe Salmonella infections. We screened the human collection from the National Antimicrobial Resistance Monitoring System 2000 for ESC resistance mechanisms. Of non-Typhi Salmonella tested, 3.2% (44/1,378) contained blaCMY genes. Novel findings included blaCMY-positive Escherichia coli O157:H7 and a blaSHV-positive Salmonella isolate. CMY-positive isolates showed a ceftriaxone MIC >2 µg/mL.

Trends of US Hospitals Distributing Infant Formula Packs to Breastfeeding Mothers, 2007 to 2013

OBJECTIVE: To examine trends in the prevalence of hospitals and birth centers (hereafter, hospitals) distributing infant formula discharge packs to breastfeeding mothers in the United States from 2007 to 2013. METHODS: The Maternity Practices in Infant Nutrition and Care survey is administered every 2 years to all hospitals with registered maternity beds in the United States. A Web- or paper-based questionnaire was distributed and completed by the people most knowledgeable about breastfeeding-related hospital practices. We examined the distribution of infant formula discharge packs to breastfeeding mothers from 2007 to 2013 by state and hospital characteristics. RESULTS: The percentage of hospitals distributing infant formula discharge packs to breastfeeding mothers was 72.6% in 2007 and 31.6% in 2013, a decrease of 41 percentage points. In 2007, there was only 1 state (Rhode Island) in which <25% of hospitals distributed infant formula discharge packs to breastfeeding mothers, whereas in 2013 there were 24 such states and territories. Distribution declined across all hospital characteristics examined, including facility type, teaching versus nonteaching, and size (annual number of births). CONCLUSIONS: The distribution of infant formula discharge packs to breastfeeding mothers declined markedly from 2007 to 2013. Discontinuing the practice of distributing infant formula discharge packs is a part of optimal, evidence-based maternity care to support mothers who want to breastfeed.

Public Opinions About Infant Feeding in the United States.

BACKGROUND Exclusive breastfeeding is recommended for the first 6 months of life. However, many barriers to breastfeeding exist. We examine public opinions about the benefits of breastfeeding and the infant health risks associated with formula feeding. METHODS A national public opinion survey was conducted in 2013. Participants indicated their level of agreement with four breastfeeding-related statements. Except for the last one, all statements were positively worded with agreement representing positive opinions toward breastfeeding. To focus on the prevalence of positive opinions, we estimated percentage agreement with the first three statements, but disagreement with the fourth. Multiple logistic regression was used to examine how odds of these positive opinions varied by socio-demographic factors. RESULTS Seventy-eight percent of participants agreed that breastmilk is nutritionally designed for infants, but few believed breastfeeding protects against overweight (12%). Approximately one-quarter agreed that formula feeding increases the chance of illness, whereas 45 percent disagreed that infant formula is equivalent to breastmilk. Older, less-educated, unmarried, and non-Hispanic black participants were less likely to agree that formula feeding increases the risk of infant illness. Races other than non-Hispanic white, participants aged 30-44 years and 45-59 years, unmarried, and less-educated participants were less likely to disagree with the equivalence of infant formula to breastmilk. DISCUSSION The nutritional value of breastmilk is well known. Fewer adults believe that breastfeeding protects against childhood overweight or that formula feeding increases the chance of infant illness. Communication efforts may increase public awareness of the health benefits of breastfeeding.