Javier A. Adachi

Enteroaggregative Escherichia coli as a Major Etiologic Agent in Traveler's Diarrhea in 3 Regions of the World

Enteroaggregative Escherichia coli (EAEC) has been reported to cause travelers diarrhea and persistent diarrhea in children in developing countries and in immunocompromised patients. To clarify the prevalence of EAEC in travelers diarrhea, we studied 636 US, Canadian, or European travelers with diarrhea: 218 in Guadalajara, Mexico (June--August 1997 and 1998), 125 in Ocho Rios, Jamaica (September 1997--May 1998), and 293 in Goa, India (January 1997--April 1997 and October 1997--February 1998). Stool samples were tested for conventional enteropathogens. EAEC strains were identified by use of the HEp-2 assay. EAEC was isolated in 26% of cases of travelers diarrhea (ranging from 19% in Goa to 33% in Guadalajara) and was second only to enterotoxigenic E. coli as the most common enteropathogen in all areas. Identification of EAEC reduced the number of cases for which the pathogen was unknown from 327 (51%) to 237 (37%) and explained 28% of cases with unknown etiology. EAEC was a major cause of travelers diarrhea in 3 geographically distinct study areas.

Rifaximin versus Ciprofloxacin for the Treatment of Traveler's Diarrhea: A Randomized, Double-Blind Clinical Trial

Rifaximin is a poorly absorbed rifamycin derivative under investigation for treatment of infectious diarrhea. Adult students from the United States in Mexico and international tourists in Jamaica were randomized to receive either rifaximin (400 mg twice per day) or ciprofloxacin (500 mg twice per day) for 3 days, following a double-blinded model, from June 1997 to September 1998. A total of 187 subjects with diarrhea were studied. Time from initiation of therapy to passage of last unformed stool was comparable for those receiving rifaximin or ciprofloxacin (median, 25.7 hours versus 25.0 hours, respectively). There was no significant difference in the proportion of subjects in the 2 groups with respect to clinical improvement during the first 24 hours (P=.199), failure to respond to treatment (P=.411), or microbiological cure (P=.222). The incidence of adverse events was low and similar in each group. Rifaximin is a safe and effective alternative to ciprofloxacin in the treatment of travelers diarrhea.

In Vitro Antimicrobial Susceptibility Testing of Bacterial Enteropathogens Causing Traveler's Diarrhea in Four Geographic Regions

ABSTRACT The emergence of resistant enteropathogens has been reported worldwide. Few data are available on the contemporary in vitro activities of commonly used antimicrobial agents against enteropathogens causing travelers diarrhea (TD). The susceptibility patterns of antimicrobial agents currently available or under evaluation against pathogens causing TD in four different areas of the world were evaluated. Pathogens were identified in stool samples from U.S., Canadian, or European adults (18 years of age or older) with TD during 1997, visiting India, Mexico, Jamaica, or Kenya. MICs of 11different antimicrobials were determined against 284 bacterial enteropathogens by the agar dilution method. Ciprofloxacin, levofloxacin, ceftriaxone, and azithromycin were highly active in vitro against the enteropathogens, while traditional antimicrobials such as ampicillin, trimethoprim, and trimethoprim/sulfamethoxazole showed high levels and high frequencies of resistance. Rifaximin, a promising and poorly absorbable drug, had an MIC at which 90% of the strains tested were inhibited of 32 μg/ml, 250 times lower than the concentration of this drug in the stools. Amdinocillin, nalidixic acid, and doxycycline showed moderate activity. Fluoroquinolones are still the drugs of choice for TD in most regions of the world, although our study has a limitation due to the lack of Escherichia coli samples from Kenya and possible bias in selection of the patients for evaluation. Azithromycin and rifaximin should be considered as promising new agents. The widespread in vitro resistance of the traditional antimicrobial agents reported since the 1980s and the new finding of resistance to fluoroquinolones in Southeast Asia are the main reasons for monitoring carefully the antimicrobial susceptibility patterns worldwide and for developing and evaluating new antimicrobial agents for the treatment of TD.

Dissemination of Methicillin-Resistant Staphylococcus aureus USA300 Sequence Type 8 Lineage in Latin America

BACKGROUND Methicillin-resistant Staphylococus aureus (MRSA) is an important nosocomial and community-associated (CA) pathogen. Recently, a variant of the MRSA USA300 clone emerged and disseminated in South America, causing important clinical problems. METHODS S. aureus isolates were prospectively collected (2006-2008) from 32 tertiary hospitals in Colombia, Ecuador, Peru, and Venezuela. MRSA isolates were subjected to antimicrobial susceptibility testing and pulsed-field gel electrophoresis and were categorized as health care-associated (HA)-like or CA-like clones on the basis of genotypic characteristics and detection of genes encoding Panton-Valentine leukocidin and staphylococcal cassette chromosome (SCC) mec IV. In addition, multilocus sequence typing of representative isolates of each major CA-MRSA pulsotype was performed, and the presence of USA300-associated toxins and the arcA gene was investigated for all isolates categorized as CA-MRSA. RESULTS A total of 1570 S. aureus were included; 651 were MRSA (41%)--with the highest rate of MRSA isolation in Peru (62%) and the lowest in Venezuela (26%)--and 71%, 27%, and 2% were classified as HA-like, CA-like, and non-CA/HA-like clones, respectively. Only 9 MRSA isolates were confirmed to have reduced susceptibility to glycopeptides (glycopeptide-intermediate S. aureus phenotype). The most common pulsotype (designated ComA) among the CA-like MRSA strains was found in 96% of isolates, with the majority (81%) having a < or =6-band difference with the USA300-0114 strain. Representative isolates of this clone were sequence type 8; however, unlike the USA300-0114 strain, they harbored a different SCCmec IV subtype and lacked arcA (an indicator of the arginine catabolic mobile element). CONCLUSION A variant CA-MRSA USA300 clone has become established in South America and, in some countries, is endemic in hospital settings.

Molecular epidemiological analysis of Escherichia coli sequence type ST131 (O25:H4) and bla CTX-M-15among extended-spectrum-β- lactamase-producing E. coli from the United States, 2000 to 2009

ABSTRACT Escherichia coli sequence type ST131 (from phylogenetic group B2), often carrying the extended-spectrum-β-lactamase (ESBL) gene blaCTX-M-15, is an emerging globally disseminated pathogen that has received comparatively little attention in the United States. Accordingly, a convenience sample of 351 ESBL-producing E. coli isolates from 15 U.S. centers (collected in 2000 to 2009) underwent PCR-based phylotyping and detection of ST131 and blaCTX-M-15. A total of 200 isolates, comprising 4 groups of 50 isolates each that were (i) blaCTX-M-15 negative non-ST131, (ii) blaCTX-M-15 positive non-ST131, (iii) blaCTX-M-15 negative ST131, or (iv) blaCTX-M-15 positive ST131, also underwent virulence genotyping, antimicrobial susceptibility testing, and pulsed-field gel electrophoresis (PFGE). Overall, 201 (57%) isolates exhibited blaCTX-M-15, whereas 165 (47%) were ST131. ST131 accounted for 56% of blaCTX-M-15-positive- versus 35% of blaCTX-M-15-negative isolates (P < 0.001). Whereas ST131 accounted for 94% of the 175 total group B2 isolates, non-ST131 isolates were phylogenetically distributed by blaCTX-M-15 status, with groups A (blaCTX-M-15-positive isolates) and D (blaCTX-M-15-negative isolates) predominating. Both blaCTX-M-15 and ST131 occurred at all participating centers, were recovered from children and adults, increased significantly in prevalence post-2003, and were associated with molecularly inferred virulence. Compared with non-ST131 isolates, ST131 isolates had higher virulence scores, distinctive virulence profiles, and more-homogeneous PFGE profiles. blaCTX-M-15 was associated with extensive antimicrobial resistance and ST131 with fluoroquinolone resistance. Thus, E. coli ST131 and blaCTX-M-15 are emergent, widely distributed, and predominant among ESBL-positive E. coli strains in the United States, among children and adults alike. Enhanced virulence and antimicrobial resistance have likely promoted the epidemiological success of these emerging public health threats.

Rifaximin: A Novel Nonabsorbed Rifamycin for Gastrointestinal Disorders

Rifaximin, a virtually nonabsorbed (<0.4%) rifamycin drug, has in vitro activity against aerobic and anaerobic gram-positive and gram-negative microorganisms. Because rifaximin is nonabsorbed, systemic adverse effects are unusual, and after 3 days of therapy, the fecal level of the drug reaches 8000 microg/g. Moreover, the important selection of resistant mutants by the related drug, rifampin, has not yet been observed for rifaximin. Rifaximin has been demonstrated to reduce the duration of travelers diarrhea secondary to noninvasive bacterial pathogens and recently has been shown to reduce the occurrence of the disease when used for chemoprophylaxis. Preliminary studies have demonstrated its potential for the treatment of other gastrointestinal disorders, such as hepatic encephalopathy. Additional studies should be performed to further define the role of rifaximin in the treatment of gastrointestinal diseases in adults and children.

Enteric Pathogens in Mexican Sauces of Popular Restaurants in Guadalajara, Mexico, and Houston, Texas

Context Travelers diarrhea is a foodborne illness. Identification of potentially contaminated food types can help physicians counsel patients. Contribution These investigators tested Mexican-style condiment sauces from 36 restaurants in Guadalajara, Mexico, and from 12 restaurants in Houston, Texas. Escherichia coli was present in 47 of 71 sauces from Guadalajara and 10 of 25 sauces from Houston. Enterotoxigenic E. coli was present in 4 of 43 tested sauces from Guadalajara; enteroaggregative E. coli was present in 14 of 32 tested sauces from Guadalajara. None of the Houston sauces contained enteropathogenic E. coli. Implications Restaurant condiment sauces are a potential source of E. coli enteropathogens in Guadalajara. The Editors Travelers diarrhea is the main health problem in international tourism in terms of frequency and economic impact (1). We previously found that among cases of travelers diarrhea with known causes, approximately 80% were caused by bacterial enteropathogens (2, 3). Contaminated food was the major vehicle of transmission of these infections (4-6). We studied Mexican sauces in Guadalajara, Jalisco, Mexico, to determine levels of Escherichia coli contamination and the presence of enteropathogens. We also studied a comparison group of similar sauces from Mexican-food restaurants in Houston, Texas. Methods We studied the level of contamination of tabletop sauces because they are a typical food found in most restaurants in Mexico and are commonly consumed by international tourists. We collected samples of Mexican saucespopularly known in the United States as green sauces, guacamole, pico de gallo, and red saucesfrom restaurants in the summer of 1998. We tested 71 sauces from 36 independently owned Mexican-style restaurants in Guadalajara that are known to be popular among U.S. travelers. We also studied a comparison sample of 25 similar sauces from 12 popular Mexican-style nonchain restaurants in Houston, Texas. For the Houston sample, we arbitrarily decided to include approximately one third of the number of samples and restaurants studied in Guadalajara. A well-mixed tablespoon-size (approximately 15 mL) sample of each type of sauce was collected from each restaurant in sterile containers. The samples were efficiently transported to our laboratories in Guadalajara or in Houston and were processed by trained personnel who followed the same standard procedures. The temperature of the sauces was not recorded. If the sample was collected in the evening, it was refrigerated at 4 C overnight and processed the next morning. The samples were diluted in sterile distilled water at a ratio of 1 to 10 and were placed in sterile Whirl-Pak bags (American Scientific Products, Houston, Texas) for homogenization in a Stomacher 400 blender (Dynatech Laboratories, Alexandria, Virginia). The pH of the food samples was determined by using a laboratory pH meter (Dynatech Laboratories). Enteric pathogens were identified from the sauces according to published methods (7). Five E. colilike colonies were retrieved from MacConkey agar plates of each food sample, stored in peptone media, and transported to our laboratory in Houston, where they were tested for the presence of enterotoxigenic E. coli by DNA hybridization and for enteroaggregative E. coli by HEp-2 adherence assay. The level of E. coli contamination was determined by placing serial twofold dilutions of food suspensions in 4-methylum-belliferyl--D-glucoronide medium plates. This method has proven to be as efficacious as and faster than conventional microbiological techniques (8, 9). Escherichia coli was chosen as an indicator of fecal contamination because it is more specific than measurements of total fecal coliforms (8, 9). Significant differences between groups were assessed by using the Fisher exact test to compare prevalence and the Wilcoxon rank-sum test to compare medians of sauce contamination in the two locations. We defined statistical significance as a P value less than 0.05. Discretionary funds from the University of TexasHouston Medical School were used to support the collection and analysis of the data. Results All samples were collected from sauce containers noted to be sitting on the tables at room temperature when we arrived at the restaurants in Guadalajara. In Houston, all of the sauces were brought to the tables on our arrival, and we noted that they were cold to the touch. Of the 96 samples of Mexican sauce that we studied, all tested negative for nonE. coli enteropathogens. Forty-seven (66%) of the 71 samples from Guadalajara grew E. coli, with a median count of 1000 E. coli colony-forming units (CFUs) per gram of sauce (range, 0 to 80 000 CFU/g). Of the 25 sauce samples from Houston, 10 (40%) grew E. coli, with a median of 0.0 CFU/g. We found a significant difference between sauces from the two cities when we compared the percentage of samples contaminated with E. coli (P = 0.03) and the median amount of E. coli colonies per sample (P = 0.008) (Table). The number of samples with E. coli contamination, as well as the median and total CFUs per gram of E. coli, were consistently higher in the samples from Guadalajara compared with Houston. Table. Presence of Escherichia coli in Tabletop Sauces from Public Mexican-Style Restaurants in Guadalajara, Mexico, and Houston, Texas Guacamole was the most frequently contaminated sauce tested in both cities; all three samples in Guadalajara and three of four samples in Houston tested positive for E. coli. The level of contamination of the guacamole sauces was higher in the Guadalajara samples than in the Houston samples (median, 4000 CFU/g vs. 10 CFU/g; P = 0.029). Moreover, among the sauces from Guadalajara restaurants, we found that the type of sauce containing the highest level of contamination was pico de gallo (median among all pico de gallo samples, 10 000 CFU/g), followed by guacamole (median, 4000 CFU/g) and green sauce (median, 1000 CFU/g). The samples of red sauce contained the lowest levels of contamination (median, 100 CFU/g). For each type of sauce studied, the Houston samples had lower median counts of E. coli, ranging from 0.0 CFU/g to 10 CFU/g. Of the 47 E. colicontaminated sauces from Guadalajara, 43 were available to be tested for enterotoxigenic E. coli and 32 were available for enteroaggregative testing. Enterotoxigenic E. coli was identified in 4 (9%) of the sauces, and enteroaggregative E. coli was found in 14 sauce samples (44%). All contaminated samples from Houston were tested for diarrheogenic E. coli strains, and neither enterotoxigenic E. coli (P = 0.128) nor enteroaggregative E. coli (P = 0.002) was identified. The average pH of all sauces from Guadalajara was 4.6 (range, 3.6 to 6.3), compared with 4.9 (range, 3.2 to 6.5) for the Houston sauces (P > 0.05). Discussion Travelers diarrhea is mainly a foodborne illness (4-6). We studied samples of sauces from popular restaurants in a tourist-oriented cityGuadalajara, Mexicowhere rates of travelers diarrhea are known to be high [2, 3]. Our study has several unique features: 1) We tested a specific and popular kind of food [Mexican sauces] from a group of nonchain restaurants that were open to the public, and 2) we compared the level of contamination of Mexican sauces from a city (Guadalajara) in a developing country with that of similar sauces from a city (Houston) in a developed country. We used this commonly consumed food item as a marker of fecal contamination. In our study, the Mexican sauces from Guadalajara more frequently contained fecal contaminants, and the median level of contamination (as measured by E. coli colonies per gram of sauce) was more than 1000 times greater than that of the sauces from Houston. We have previously shown frequent enteropathogen contamination of food samples in Guadalajara (6). We found enterotoxigenic and enteroaggregative E. coli, currently the major causes of diarrhea in travelers visiting Guadalajara (2, 3), in the sauces studied. Thus, these foods may play a role in the acquisition of illness. We previously reported a high prevalence of enterotoxigenic E. coli in cases of travelers diarrhea and the isolation of enterotoxigenic E. coli in food samples in Guadalajara (4-6). Although the presence of enterotoxigenic E. coli in food served in Mexico has been reported previously, this is one of the first descriptions of enteroaggregative E. coli contamination of such food. Enteroaggregative E. coli is a newly recognized pathogen in the group of diarrheogenic E. coli (3, 10). Its pathogenic role has been confirmed in outbreaks and in volunteer studies (11), and recent studies by our group have shown that enteroaggregative E. coli is nearly as important as enterotoxigenic E. coli in causing travelers diarrhea in Guadalajara (3). The prevalence of enteroaggregative E. coli in Mexican sauces may provide valuable information about the source of symptomatic and asymptomatic enteroaggregative E. coli infection in U.S. students visiting Guadalajara (12). It is a popular notion that low pH protects against bacterial food contamination. However, our results suggest that pH is an ineffective deterrent to microbial contamination because E. coli contamination was found in sauces with acidic pH levels. This finding could be explained by the recently described capacity of some E. coli strains to adapt to acidic conditions (13, 14). The higher level of E. coli contamination in the sauces in Guadalajara could be explained by the amount of time that sauces were kept at room temperature. We noted that the sauces in Guadalajara were prepared on the premises and were not refrigerated before or between meals, while the Houston sauces were refrigerated before they were served to customers. Moreover, we believe that the sauces were more likely to be handled by multiple workers and patrons (reuse of the same sauce) in Mexico than in Houston. Further studies of food hygiene practices are needed to clarify

Natural history of enteroaggregative and enterotoxigenic Escherichia coli infection among US travelers to Guadalajara, Mexico

The natural history of enteroaggregative Escherichia coli (EAEC) and enterotoxigenic E. coli (ETEC) infection was studied among 40 US travelers who provided weekly stool samples for 4 weeks after arrival in Mexico. At enrollment, 5 subjects were colonized by EAEC and 3 by ETEC. During the first 2 weeks after enrollment, 12 developed EAEC diarrhea, 7 developed ETEC diarrhea (5 with mixed EAEC/ETEC diarrhea), 13 had EAEC colonization, and 7 had ETEC colonization. During the third and fourth weeks, 4 experienced EAEC diarrhea, 2 experienced ETEC diarrhea (1 with mixed EAEC/ETEC diarrhea), 31 had EAEC colonization, and none had ETEC colonization. Plasmid DNA analysis showed a high degree of heterogeneity among EAEC isolates. Symptomatic EAEC infection occurred early after arrival in Guadalajara, Mexico, and was as common as ETEC infection. Asymptomatic EAEC infection was recurrent.

Empirical antimicrobial therapy for traveler's diarrhea.

Over 7 million cases of travelers diarrhea, defined as the passage of > or = 3 unformed stools in a 24-h period, occur each year among visitors to developing countries. Bacterial enteric pathogens are the most common etiologic agents isolated. Preliminary clinical results for patients with diarrhea predominantly caused by Campylobacter species have shown that azithromycin may be an effective alternative to fluoroquinolones for the treatment of travelers diarrhea.

Enteroaggregative Escherichia coli as a Cause of Traveler's Diarrhea: Clinical Response to Ciprofloxacin

The purpose of this study was to determine the role of enteroaggregative Escherichia coli (EAEC) in the development of travelers diarrhea and the clinical response of patients with EAEC diarrhea following treatment with ciprofloxacin. Sixty-four travelers with diarrhea and no other recognized enteropathogen were enrolled in treatment studies in Jamaica and Mexico from July 1997 to July 1998. EAEC was isolated from 29 travelers (45.3%). There was a significant reduction in the duration of posttreatment diarrhea in the 16 patients treated with ciprofloxacin, as compared with that in the 13 patients who received placebo (mean of 35.3 versus 55.5 hours; P = .049). There was a nonsignificant reduction in the mean number of unformed stools passed during the 72 hours after enrollment in the ciprofloxacin-treated group (5.6), as compared with that in the placebo group (7.5) (P = .128). This study provides additional evidence that EAEC should be considered as a cause of antibiotic-responsive travelers diarrhea.