Amy Krueger

Antimicrobial resistance among invasive nontyphoidal Salmonella enterica isolates in the United States: National Antimicrobial Resistance Monitoring System, 1996 to 2007.

ABSTRACT Nontyphoidal salmonellae (NTS) are important causes of community-acquired bloodstream infection. We describe patterns of antimicrobial resistance among invasive NTS in the United States. We compared bloodstream NTS isolates with those from stool submitted to the National Antimicrobial Resistance Monitoring System (NARMS) from 1996 to 2007. We describe antimicrobial resistance among invasive strains by serogroup and serotype. Of the 19,302 NTS isolates, 17,804 (92.2%) were from stool or blood. Of these, 1,050 (5.9%) were bloodstream isolates. The median ages (ranges) of patients with and without bacteremia were 36 (<1 to 97) years and 20 (<1 to 105) years, respectively (P < 0.001). Males (odds ratio [OR], 1.21; 95% confidence interval [CI], 1.06 to 1.38) and those ≥65 years of age were at greater risk for invasive disease. Salmonella enterica serotypes Enteritidis, Typhimurium, and Heidelberg were the most common serotypes isolated from blood; S. enterica serotypes Dublin, Sandiego, and Schwarzengrund were associated with the greatest risk for bloodstream isolation. Of invasive isolates, 208 (19.8%) were resistant to ampicillin, 117 (11.1%) to chloramphenicol, and 26 (2.5%) to trimethoprim-sulfamethoxazole; 28 (2.7%) isolates were resistant to nalidixic acid and 26 (2.5%) to ceftriaxone. Antimicrobial resistance to traditional agents is common. However, the occurrence of nalidixic acid and ceftriaxone resistance among invasive NTS is cause for clinical and public health vigilance.

Antimicrobial Susceptibility Patterns of Shigella Isolates in Foodborne Diseases Active Surveillance Network (FoodNet) Sites, 2000–2010

BACKGROUND Treatment of shigellosis with appropriate antimicrobial agents shortens duration of illness and bacterial shedding, but resistance to commonly used agents is increasing. METHODS We describe resistance patterns among Shigella isolates in the United States with use of linked data from the Foodborne Diseases Active Surveillance Network (FoodNet) and National Antimicrobial Resistance Monitoring System (NARMS). FoodNet sites send every 20th Shigella isolate to the NARMS laboratory for susceptibility testing. RESULTS During 2000-2010, the NARMS laboratory tested 1376 Shigella isolates from FoodNet sites. Of 1118 isolates (81%) linked to FoodNet, 826 (74%) were resistant to ampicillin, 649 (58%) to streptomycin, 402 (36%) to trimethoprim-sulfamethoxazole (TMP-SMX), 355 (32%) to sulfamethoxazole-sulfisoxazole, 312 (28%) to tetracycline, 19 (2%) to nalidixic acid, and 6 (0.5%) to ciprofloxacin. The proportion of Shigella isolates with resistance to TMP-SMX was 40% among white persons, 58% among Hispanic persons, and 75% among persons with a history of international travel. Resistance to at least TMP-SMX and ampicillin was present in 25% of isolate, and 5% were resistant to ampicillin, TMP-SMX, and chloramphenicol. Overall, 5% of isolates showed multidrug resistance to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole-sulfisoxazole, and tetracycline, including 49 Shigella flexneri (33%) and 3 Shigella sonnei (0.3%) isolates. Male individuals were more likely than female individuals to be infected with a multidrug-resistant strain (7% versus 3%; P < .01). CONCLUSIONS Antimicrobial resistance differed by race, ethnicity, age, travel, and species. Resistance to commonly used antibiotics is high; therefore, it is important to look at the susceptibility pattern before starting treatment.

CTX-M–producing Non-Typhi Salmonella spp. Isolated from Humans, United States

CTX-M–type β-lactamases are increasing among US Enterobacteriaceae isolates. Of 2,165 non-Typhi Salmonella isolates submitted in 2007 to the National Antimicrobial Resistance Monitoring System, 100 (4.6%) displayed elevated MICs (>2 mg/L) of ceftriaxone or ceftiofur. Three isolates (serotypes Typhimurium, Concord, and I 4,5,12:i:–) contained blaCTX-M-5, blaCTX-M-15, and blaCTX-M-55/57, respectively.

Antimicrobial resistance trends of Shigella serotypes in New York City, 2006-2009.

Shigellosis is the third most common enteric bacterial infection in the United States. Although infection is typically self-limiting, empiric treatment is often prescribed. Because of increasing antimicrobial resistance to Shigella, empiric treatment options are decreasing. Identifying resistance patterns can inform empiric treatment recommendations. The goals of our study were to examine risk factors associated with antimicrobial resistance of Shigella and examine issues related to empiric treatment and antimicrobial resistance of Shigella. During June 2006-February 2009, we attempted to interview all New York City patients reported to have shigellosis. Their Shigella isolates were tested for antimicrobial susceptibility to examine the level of resistance and identify risk factors for resistance. Analysis was conducted on two groups distinguished by a large outbreak that was documented during the data collection period. Of the 477 nonoutbreak patients, 333 (70%) patients reported taking an antibiotic for shigellosis and 36 (11%) were treated with an antibiotic to which their Shigella infection was resistant. Among this group, high levels of antimicrobial resistance were detected to amoxicillin-clavulanate (66%), ampicillin (68%), and trimethoprim-sulfamethoxazole (66%). Non-travel-associated ciprofloxacin-resistant Shigella (five patients) and ciprofloxacin-resistant Shigella sonnei (four patients) were reported for the first time to our knowledge. Antimicrobial resistance is significantly higher in New York City residents compared with national data. Some patients were treated with therapies that were not effective and to which the patients Shigella infection was resistant. Shigella infections should not be treated with antibiotics unless the patient presents with severe or underlying illness and is at risk for systemic illness. When treatment is indicated, local monitoring of Shigella for antimicrobial resistance will provide local clinicians with the best guidance for effective empiric treatments.

Plasmid-mediated quinolone resistance among non-Typhi Salmonella enterica isolates, USA.

We determined the prevalence of plasmid-mediated quinolone resistance mechanisms among non-Typhi Salmonella spp. isolated from humans, food animals, and retail meat in the United States in 2007. Six isolates collected from humans harbored aac(6′)Ib-cr or a qnr gene. Most prevalent was qnrS1. No animal or retail meat isolates harbored a plasmid-mediated mechanism.

Increase in resistance to ceftriaxone and nonsusceptibility to ciprofloxacin and decrease in multidrug resistance among Salmonella strains, United States, 1996-2009.

BACKGROUND Salmonella is a major bacterial pathogen transmitted commonly through food. Increasing resistance to antimicrobial agents (e.g., ceftriaxone, ciprofloxacin) used to treat serious Salmonella infections threatens the utility of these agents. Infection with antimicrobial-resistant Salmonella has been associated with increased risk of severe infection, hospitalization, and death. We describe changes in antimicrobial resistance among nontyphoidal Salmonella in the United States from 1996 through 2009. METHODS The Centers for Disease Control and Preventions National Antimicrobial Resistance Monitoring System conducts surveillance of resistance among Salmonella isolated from humans. From 1996 through 2009, public health laboratories submitted isolates for antimicrobial susceptibility testing. We used interpretive criteria from the Clinical and Laboratory Standards Institute and defined isolates with ciprofloxacin resistance or intermediate susceptibility as nonsusceptible to ciprofloxacin. Using logistic regression, we modeled annual data to assess changes in antimicrobial resistance. RESULTS From 1996 through 2009, the percentage of nontyphoidal Salmonella isolates resistant to ceftriaxone increased from 0.2% to 3.4% (odds ratio [OR]=20, 95% confidence interval [CI] 6.3-64), and the percentage with nonsusceptibility to ciprofloxacin increased from 0.4% to 2.4% (OR=8.3, 95% CI 3.3-21). The percentage of isolates that were multidrug resistant (resistant to ≥3 antimicrobial classes) decreased from 17% to 9.6% (OR=0.6, 95% CI 0.5-0.7), which was driven mainly by a decline among serotype Typhimurium. However, multidrug resistance increased from 5.9% in 1996 to a peak of 31% in 2001 among serotype Newport and increased from 12% in 1996 to 26% in 2009 (OR=2.6, 95% CI 1.1-6.2) among serotype Heidelberg. CONCLUSIONS We describe an increase in resistance to ceftriaxone and nonsusceptibility to ciprofloxacin and an overall decline in multidrug resistance. Trends varied by serotype. Because of evidence that antimicrobial resistance among Salmonella is predominantly a consequence of antimicrobial use in food animals, efforts are needed to reduce unnecessary use, especially of critically important agents.

Identification and Characterization of CTX-M-Producing Shigella Isolates in the United States

Shigellosis is a major source of gastroenteritis throughout the world (14). Extended-spectrum β-lactamases (ESBLs), including cefotaximases (CTX-M), confer resistance to extended-spectrum cephalosporins and significantly compromise the treatment options for shigellosis. Numerous ESBLs have been described among Enterobacteriaceae (2, 8, 13); however, only a single CTX-M-producing Shigella isolate has been reported in the United States (10). From 1999 to 2007, 3,880 Shigella isolates were screened for antimicrobial susceptibility to 14 to 17 antimicrobials by broth microdilution (Sensititre; Trek Diagnostics, Westlake, OH). Six isolates displayed decreased susceptibility (MIC ≥ 2 mg/liter) to ceftriaxone (Table ​(Table1).1). The six case-patients included three males and two females (gender information was unavailable for one patient), and the median age was 3 years (range, 1 to 8 years). Additional details were available for five patients. Three of the five (60%) were hospitalized, and one was admitted twice. One patient had an adopted sibling from Russia but had not traveled herself. The second patient traveled to a neighboring state prior to illness onset, and the third reported no travel. Of the nonhospitalized patients, one was an asymptomatic adoptee from China and the second reported no travel. Two patients received antimicrobial therapy: ceftriaxone, cefotaxime, and trimethoprim-sulfamethoxazole for one patient, azithromycin for the other patient. TABLE 1. Characterization of CTX-M-positive Shigella isolates, transformants, and CTX-M-encoding plasmidsa PCR analysis was used to screen the six isolates for 13 different classes or groups of bla genes, and PCR results were confirmed by DNA sequencing (1, 5, 11, 12, 16, 18-21). Four isolates were positive for the blaCTX-M-15 gene, while two were positive for the blaCTX-M-14 gene (Table ​(Table1).1). All four blaCTX-M-15 isolates were PCR positive for non-ESBL blaTEM-1 genes. Both blaCTX-M-14 isolates were PCR positive for non-ESBL blaOXA-1 genes, and a single isolate was positive for both blaTEM-1 and blaOXA-1. By pulsed-field gel electrophoresis (PFGE) analysis, all three S. sonnei and all three S. flexneri isolates demonstrated distinct patterns (data not shown) (15). All six blaCTX-M genes were determined to be plasmid encoded (6). The non-ESBL β-lactamases (OXA-1, TEM-1) did not transfer and were not encoded on the same CTX-M plasmids. All three S. sonnei plasmids and two of the S. flexneri plasmids harbored only the CTX-M-associated resistance. The remaining S. flexneri plasmid contained additional determinants conferring resistance to trimethoprim-sulfamethoxazole and gentamicin. All three S. sonnei plasmids were incompatibility type IncI1 and approximately 90 kb in size (plasmid pulsed-field gel electrophoresis) (Table ​(Table1)1) (4). Plasmid multilocus sequence typing (pMLST) identified them as novel sequence types designated as ST31 complex. The plasmid from AM22451 contained several point mutations in one allele, necessitating the ST32 designation within the ST31 clonal complex (http://pubmlst.org/plasmid) (7). Of the three S. flexneri plasmids, the blaCTX-M-15-positive plasmid was a 165-kb IncA/C plasmid, while the two blaCTX-M-14-positive plasmids were identical 75-kb IncFII plasmids. CTX-M-14 and CTX-M-15 are the most common types of cefotaximases identified among Shigella isolates (9, 17, 22), and IncI1 plasmids carrying CTX-M-15 have been already described in Escherichia coli and Salmonella isolates from Australia, France, and the United Kingdom (3). The emergence of CTX-M-producing Shigella isolates in the United States is concerning and necessitates continued resistance surveillance.

Health Department HIV Prevention Programs That Support the National HIV/AIDS Strategy: The Enhanced Comprehensive HIV Prevention Planning Project, 2010-2013.

Objective. The Enhanced Comprehensive HIV Prevention Planning project was the first initiative of the Centers for Disease Control and Prevention (CDC) to address the goals of the National HIV/AIDS Strategy (NHAS). Health departments in 12 U.S. cities with a high prevalence of AIDS conducted comprehensive program planning and implemented cost-effective, scalable HIV prevention interventions that targeted high-risk populations. We examined trends in health department HIV prevention programs in these cities during the project. Methods. We analyzed the number of people who received partner services, condoms distributed, and people tested for HIV, as well as funding allocations for selected HIV prevention programs by year and by site from October 2010 through September 2013. We assessed trends in the proportional change in services and allocations during the project period using generalized estimating equations. We also conducted thematic coding of program activities that targeted people living with HIV infection (PLWH). Results. We found significant increases in funding allocations for HIV testing and condom distribution. All HIV partner services indicators, condom distribution, and HIV testing of African American and Hispanic/Latino populations significantly increased. HIV tests associated with a new diagnosis increased significantly among those self-identifying as Hispanic/Latino but significantly decreased among African Americans. For programs targeting PLWH, health department activities included implementing new program models, improving local data use, and building local capacity to enhance linkage to HIV medical care, retention in care, and treatment adherence. Conclusions. Overall, these findings indicate that health departments in areas with a high burden of AIDS successfully shifted their HIV prevention resources to scale up important HIV programs and make progress toward NHAS goals.

Commensal Escherichia coli Isolate Resistant to Eight Classes of Antimicrobial Agents in the United States

To increase understanding of community-acquired resistance, stool samples from 477 nonhospitalized persons in Maryland and Michigan, from 2004 to 2008, were screened for ceftriaxone resistance. Seven (1.5%) yielded ceftriaxone-resistant Escherichia coli; one isolate was resistant to all eight antimicrobial classes routinely tested: aminoglycosides, β-lactam/β-lactamase inhibitor combinations, cephems, penicillins, folate pathway inhibitors, phenicols, quinolones, and tetracyclines. The extensively resistant isolate was from a 50-year-old woman who denied antimicrobial use, hospitalization, or international travel within 6 months. Meat (beef, chicken, and pork) and eggs were consumed within 1 month before stool collection. Further studies are warranted to understand potential sources, including the food supply, of resistant E. coli.

County-Level Correlates of CDC-Funded HIV Testing Events, United States, 2012

HIV prevalence and socio-demographic data were analyzed to assess the alignment of CDC-funded HIV testing activity in 2012 with its high-impact prevention approach. CDC-funded HIV-testing was conducted in counties with high HIV prevalence and in places potentially more affected by HIV as measured by urbanicity, percent black, percent poverty, and percent uninsured. The percent Hispanic/Latino was associated with a lower probability of HIV testing activity. Higher percentages of black and Hispanic/Latino in the population was positively associated with new HIV diagnoses. Analyzing county-level data confirmed the appropriateness of CDC-funded HIV testing activities under a high-impact prevention approach but also suggested areas for possible improvement.