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The immigration of Latin American women of childbearing age has spread the congenital transmission of Chagas disease to areas of nonendemicity, and the disease is now a worldwide problem. Some European health authorities have implemented screening programs to prevent vertical transmission, but the lack of a uniform protocol calls for the urgent establishment of a new strategy common to all laboratories. Our aims were to (i) analyze the trend of passive IgG antibodies in the newborn by means of five serological tests for the diagnosis and follow-up of congenital Trypanosoma cruzi infection, (ii) assess the utility of these techniques for diagnosing a congenital transmission, and (iii) propose a strategy for a prompt, efficient, and cost-effective diagnosis of T. cruzi infection. In noninfected newborns, a continuous decreasing trend of passive IgG antibodies was observed, but none of the serological assays seroreverted in any the infants before 12 months. From 12 months onwards, serological tests achieved negative results in all the samples analyzed, with the exception of the highly sensitive chemiluminescent microparticle immunoassay (CMIA). In contrast, in congenitally infected infants, the antibody decline was detected only after treatment initiation. In order to improve the diagnosis of congenital T. cruzi infection, we propose a new strategy involving fewer tests that allows significant cost savings. The protocol could start 1 month after birth with a parasitological test and/or a PCR. If negative, a serological test would be carried out at 9 months, which if positive, would be followed by another at around 12 months for confirmation.

This work evaluated a serial blood sampling procedure to enhance the sensitivity of duplex real-time quantitative PCR (qPCR) for baseline detection and quantification of parasitic loads and posttreatment identification of failure in the context of clinical trials for treatment of chronic Chagas disease, namely, DNDi-CH-E1224-001 (ClinicalTrials.gov registration no. NCT01489228) and the MSF-DNDi PCR Sampling Optimization Study (NCT01678599)., This work evaluated a serial blood sampling procedure to enhance the sensitivity of duplex real-time quantitative PCR (qPCR) for baseline detection and quantification of parasitic loads and posttreatment identification of failure in the context of clinical trials for treatment of chronic Chagas disease, namely, DNDi-CH-E1224-001 (ClinicalTrials.gov registration no. NCT01489228) and the MSF-DNDi PCR Sampling Optimization Study (NCT01678599). Patients from Cochabamba (n = 294), Tarija (n = 257), and Aiquile (n = 220) were enrolled. Three serial blood samples were collected at each time point, and qPCR triplicates were tested for each sample. The first two samples were collected during the same day and the third one 7 days later. A patient was considered PCR positive if at least one qPCR replicate was detectable. Cumulative results of multiple samples and qPCR replicates enhanced the proportion of pretreatment sample positivity from 54.8% to 76.2%, 59.5% to 77.8%, and 73.5% to 90.2% in Cochabamba, Tarija, and Aiquile cohorts, respectively. This strategy increased the detection of treatment failure from 72.9% to 91.7%, 77.8% to 88.9%, and 42.9% to 69.1% for E1224 low-, short-, and high-dosage regimens, respectively, and from 4.6% to 15.9% and 9.5% to 32.1% for the benznidazole arm in the DNDi-CH-E1224-001 and MSF-DNDi studies, respectively. The addition of the third blood sample and third qPCR replicate in patients with nondetectable PCR results in the first two samples gave a small, non-statistically significant improvement in qPCR positivity. No change in clinical sensitivity was seen with a blood volume increase from 5 to 10 ml. The monitoring of patients treated with placebo in the DNDi-CH-E1224-001 trial revealed fluctuations in parasitic loads and occasionally nondetectable results. In conclusion, a serial sampling strategy enhanced PCR sensitivity to detecting treatment failure during follow-up and has the potential for improving recruitment capacity in Chagas disease trials, which require an initial positive qPCR result for patient admission.

Treatment for Chagas disease with currently available medications is recommended universally only for acute cases (all ages) and for children up to 14 years old. The World Health Organization, however, also recommends specific antiparasite treatment for all chronic-phase Trypanosoma cruzi-infected individuals, even though in current medical practice this remains controversial, and most physicians only prescribe palliative treatment for adult Chagas patients with dilated cardiomyopathy. The present opinion, prepared by members of the NHEPACHA network (Nuevas Herramientas para el Diagnóstico y la Evaluación del Paciente con Enfermedad de Chagas/New Tools for the Diagnosis and Evaluation of Chagas Disease Patients), reviews the paradigm shift based on clinical and immunological evidence and argues in favor of antiparasitic treatment for all chronic patients. We review the tools needed to monitor therapeutic efficacy and the potential criteria for evaluation of treatment efficacy beyond parasitological cure. Etiological treatment should now be mandatory for all adult chronic Chagas disease patients. Fil: Viotti, Rodolfo Jorge. Provincia de Buenos Aires. Ministerio de Salud. Hospital Interzonal de Agudos "Eva Peron"; Argentina Fil: Alarcón de Noya, B.. Universidad Central de Venezuela. Instituto de Medicina Tropical; Venezuela Fil: Araujo Jorge, T.. Ministerio de Salud de Brasil. Fundacion Oswaldo Cruz; Brasil Fil: Grijalva, M. J.. Pontificia Universidad Católica del Ecuador. Centro de Investigación de Enfermedades Infecciosas; Ecuador. Ohio University. Tropical Disease Institute; Estados Unidos Fil: Guhl, F.. Universidad de los Andes. Centro de Investigaciones en Microbiología y Parasitología Tropical; Colombia Fil: López, M. C.. Consejo Superior de Investigaciones Científicas. Instituto de Parasitología y Biomedicina "Lopez Neyra"; España Fil: Ramsey, J. M.. Instituto Nacional de Salud Pública. Centro Regional de Investigación en Salud Pública; México Fil: Ribeiro, I.. Drugs for Neglected Diseases Initiative; Suiza Fil: Schijman, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Argentina Fil: Sosa Estani, S.. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud. Instituto Nacional de Parasitología; Argentina Fil: Torrico, F.. Universidad Mayor de San Simón; Bolivia Fil: Gascon, J.. Centro de Investigación en Salud Internacional de Barcelona; España

For treating Chagas disease (CD), a current worldwide health problem, only benznidazole and nifurtimox have been approved to be used. In both cases, unwanted drug-related adverse events (ADRs) are frequent when these drugs are used in adults in the chronic stage. The main objective of this study was to establish benznidazole ADRs and their relationship to serum concentrations in patients with chronic Trypanosoma cruzi infection in order to perform more accurate dosages to minimize ADRs. A total of 54 patients were recruited over 12 months. Of these 54 patients, 53 (98%) experienced at least one ADR during follow-up, and the overall average ADR incidence was 2.4 episodes/patient/month. Benznidazole treatment was discontinued in 11 patients, 7 among them due to severe adverse effects. The mean duration of treatment before withdrawal was 11 days. Benznidazole serum concentrations were recorded on days 15, 30, 45, and 60 of follow-up and evaluated according to clinical and epidemiological variables and ADR severity. No relationship was found between the benznidazole serum concentration and the ADRs. The mean (standard deviation) trough serum benznidazole concentrations (all below 20 mcg/ml) on days 15, 30, 45, and 60 were 6.4 (1.9), 6.1 (1.8), 6.2 (2.2), and 5.7 (1.7) μg/ml, respectively. Benznidazole serum concentrations do not appear to be related to the appearance of serious ADRs. Further, well-controlled studies are necessary to establish the optimal regimen for benznidazole in adults with chronic CD.

The evolution of antimicrobial resistance in Salmonella isolates causing traveler's diarrhea (TD) and their mechanisms of resistance to several antimicrobial agents were analyzed. From 1995 to 2002, a total of 62 Salmonella strains were isolated from stools of patients with TD. The antimicrobial susceptibility to 12 antibiotics was determined, and the molecular mechanisms of resistance to several of them were detected as well. The highest levels of resistance were found against tetracycline and ampicillin (21 and 19%, respectively), followed by resistance to nalidixic acid (16%), which was mainly detected from 2000 onward. Molecular mechanisms of resistance were analyzed in 16 isolates. In these isolates, which were resistant to ampicillin, two genes encoding β-lactamases were detected: oxa-1 (one isolate) and tem -like (seven isolates [in one strain concomitantly with a carb-2 ]). Resistance to tetracycline was mainly related to tetA (five cases) and to tetB and tetG (one case each). Resistance to chloramphenicol was related to the presence of the floR and cmlA genes and to chloramphenicol acetyltransferase activity in one case each. Different genes encoding dihydrofolate-reductases ( dfrA1 , dfrA12 , dfrA14 , and dfrA17 ) were detected in trimethoprim-resistant isolates. Resistance to nalidixic acid was related to the presence of mutations in the amino acid codons 83 or 87 of the gyrA gene. Further surveillance of the Salmonella spp. causing TD is needed to detect trends in their resistance to antimicrobial agents, as we have shown in our study with nalidixic acid. Moreover, such studies will lead to better treatment and strategies to prevent and limit their spread.

This study aims to characterize the presence of virulence factors of enterotoxigenic Escherichia coli (ETEC) causing traveler's diarrhea. Among 52 ETEC isolates, the most common toxin type was STh, and the most frequent colonization factors (CFs) were CS21, CS6, and CS3. On the other hand, the nonclassical virulence factors EAST1 and EatA were frequently present.

Chagas disease is a parasitic infection that leads to a significant public health problem in countries where the disease is endemic and where it is nonendemic. Benznidazole is the most commonly used drug for the etiological treatment of Chagas disease. Patients treated with benznidazole suffer frequent adverse drug reactions. Although arthralgia is common, arthritis has been reported as a very rare side effect. The objective of this study was to describe arthritis in a cohort of Trypanosoma cruzi -infected patients treated with benznidazole.

Eighty-six strains of Shigella spp. were isolated during the dry season from stool samples of children under 5 years of age in Ifakara, Tanzania. The epidemiological relationship as well as the antimicrobial susceptibility and mechanisms of resistance to ampicillin, chloramphenicol, and co-trimoxazole were investigated. Four different epidemiological tools, pulsed-field gel electrophoresis (PFGE), repetitive extragenic palindromic (REP)-PCR, plasmid analysis, and antibiogram, were compared for typing Shigella strains. Seventy-eight (90%) strains were Shigella flexneri and were distributed into four groups, by either PFGE or REP-PCR, with 51, 17, 7, and 3 strains. The four strains of Shigella dysenteriae belonged to the same group, and the four strains of Shigella sonnei were distributed in two groups with three and one strain each. Plasmid analysis showed a high level of heterogeneity among strains belonging to the same PFGE group, while the antibiogram was less discriminative. REP-PCR provided an alternative, rapid, powerful genotyping method for Shigella spp. Overall, antimicrobial susceptibility testing showed a high level of resistance to ampicillin (81.8%), chloramphenicol (72.7%), tetracycline (96.9%), and co-trimoxazole (87.9%). Ampicillin resistance was related to an integron-borne OXA-1-type β-lactamase in 85.1% of the cases and to a TEM-1-type β-lactamase in the remaining 14.8%. Resistance to co-trimoxazole was due to the presence of a dhfr Ia gene in all groups except one of S. flexneri , where a dhfr VII gene was found within an integron. Chloramphenicol resistance was associated in every case with positive chloramphenicol acetyltransferase activity. All strains were susceptible to nalidixic acid, ciprofloxacin, ceftazidime, cefotaxime, and cefoxitin. Therefore, these antimicrobial agents may be good alternatives for the treatment of diarrhea caused by Shigella in Tanzania.

A carbapenem-resistant Escherichia coli strain (DVR22) was recovered from a stool specimen from a patient with traveler's diarrhea who had traveled to India. Molecular screening led to the first identification of NDM-1 in Spain. The bla NDM-1 gene was located in a conjugative plasmid of ca. 300 kb that also contained the bla CTX-M-15 , bla TEM-1 , Δ bla DHA-1 , and armA genes. In addition, bla NDM-1 was preceded by an IS Aba125 insertion element only found in Acinetobacter spp.

Enterotoxigenic Escherichia coli isolates were identified as a cause of traveler’s diarrhea in 82 of 520 (16%) patients and tested for resistance to seven antimicrobial agents. Thirty patients (36%) needed antimicrobial therapy: 17 (56%) for persistence of symptoms and 13 (44%) for severity of symptoms. Ampicillin, tetracycline, and trimethoprim-sulfamethoxazole resistance was high. Chloramphenicol showed moderate activity, and amoxicillin plus clavulanic acid, nalidixic acid, and ciprofloxacin showed very good activity. Five nalidixic acid-resistant strains were isolated, four from patients visiting India. Enterotoxigenic Escherichia coli (ETEC) is the major cause of traveler’s diarrhea in people from industrialized countries visiting less-developed countries (6, 7) and is an important cause of dehydrating diarrhea in infants and children in lessdeveloped countries (13). Traveler’s diarrhea caused by ETEC strains is usually a mild, self-limited disease, but for severe traveler’s diarrhea, early treatment with loperamide and an antibiotic such as trimethoprim-sulfamethoxazole, doxycycline, or a fluoroquinolone has been recommended (4). Many previous studies of antimicrobial susceptibility of ETEC involved a small number of isolates from a single geographic location. We, therefore, performed antimicrobial susceptibility testing of ETEC isolates causing traveler’s diarrhea originating from diverse geographical locations. Investigation of the mechanisms of acquisition of quinolone resistance in the nalidixic acid-resistant ETEC strains was also performed. During the period from 1994 to 1997, stool specimens from 520 adult patients with traveler’s diarrhea were analyzed. The patients were recruited from the traveler’s clinic of the Tropical Medicine Department of the Hospital Clinic. All patients had diarrhea on arrival in Spain or within 2 days after their return. The stool specimens were cultured for E. coli and other bacterial enteropathogens by conventional methods (11). Single-colony subcultures of all different lactose-fermenting colonial morphotypes growing on MacConkey agar were identified by conventional criteria. The E. coli isolates were tested by PCR to detect the heat-stable (ST) and heat-labile (LT) toxin genes (15). ETEC strains were isolated from 82 patients (16%) with traveler’s diarrhea. The distribution of these strains according to the type of enterotoxin synthesized was as follows: 58 strains (71%) produced the ST, 11 strains (13%) produced LT, and 13 strains (16%) produced both toxins (LT/ST). ETEC strains were isolated from stool samples of patients traveling to different tropical and subtropical areas, except for Central and South Africa. The range of prevalence was from 7.5% to 31%, with West Africa and the Indian Subcontinent being the two geographic areas where ETEC strains were more prevalent, at 31 and 22%, respectively. Thirty patients (36%) needed antimicrobial therapy: 17 patients (56%) because of persistence of symptoms and 13 (44%) because of severity of symptoms. In 14 treated patients, the cause of diarrhea was ST-producing ETEC (ETEC-ST), representing 24% of the total number of strains of ETEC-ST, whereas in 7 (63%) and 9 (69%) patients, the cause was LT- and LT/ST-producing ETEC, respectively (P , 0.02). All patients were empirically treated with ciprofloxacin, and in all, the duration of diarrhea was shortened and the accompanying symptoms such as abdominal discomfort, flatulence, nausea, and vomiting were relieved. It is noteworthy that patients with ETEC-LT and ETEC-LT/ST strains required antimicrobial therapy more frequently than patients with ETEC-ST strains. However, this finding needs to be confirmed in future studies. The MICs for the clinical isolates studied were determined by E-test according to standard practice. E. coli ATCC 25922 was used as a reference strain for quality control. The breakpoints considered to define a resistant strain were those recommended in reference 12. The MICs of antimicrobial agents for ETEC-ST, ETEC-LT, and ETEC-ST/LT strains are shown in Table 1. Randomized, controlled studies have demonstrated that a 3- to 5-day course of an antibiotic can reduce the duration of an acute diarrheal episode in travelers. Most studies

Nowadays, around 40 to 60% of Spanish travelers to developing countries develop diarrhea (4). Different enteropathogens have been associated with the development of traveler's diarrhea. The levels of prevalence of these enteropathogens as a cause of traveler's diarrhea are 42% for diarrheagenic Escherichia coli, 19.4% for Shigella spp., 3% for Salmonella spp., 2% for Campylobacter spp., 2% for Yersinia spp., 2% for Aeromonas spp., and 128 μg/ml. Cotrimoxazole and ampicillin have been widely used to treat traveler's diarrhea (3, 11, 12), and the long use and sometimes the misuse of these antibiotics have been associated with the increase of resistance levels (1, 10, 12). MIC50s and MIC90s of rifaximin and rifampin were very similar. MICs of rifaximin ranged from 4 to 8 and from 4 to 16 μg/ml, and MICs of rifampin ranged from 4 to 16 and from 8 to 16 μg/ml, for all tested bacteria except Yersinia enterocolitica and C. jejuni. In particular, the MIC50 and MIC90 of rifamixin of 64 and 128 μg/ml, respectively, were observed for Y. enterocolitica and a value of >128 μg/ml for both the MIC50 and MIC90 was achieved for C. jejuni. In this case and only for rifaximin, doses greater than 128 μg/ml were tested to determine the precise MIC50s and MIC90s, which were found to be 256 and 512 μg/ml, respectively. The in vitro activities of rifaximin against strains from stock culture collections of four university-associated teaching hospitals had been previously reported by Hoover et al. (6). In that study, the activities of rifaximin against enteropathogens were found to be as follows: a MIC50 of 4 to 8 μg/ml and a MIC90 of >8 μg/ml. These results are in accordance with ours, even though our strains were isolated from patients who traveled to different geographical areas. In another study, Ripa et al. (9) tested rifaximin against Campylobacter and Yersinia strains collected from patients with diarrhea. The main difference between these studies and ours is the MICs of rifaximin for Y. enterocolitica and C. jejuni, two microorganisms which were isolated from not more than 2% of patients with traveler's diarrhea in our laboratory (3). In conclusion, rifaximin is a nonabsorbable antimicrobial agent, reaching high concentrations in the intestinal tract. The concentrations of rifaximin achieved in the intestinal tract are more than 10-fold higher than the MICs of this antimicrobial agent for the different enteropathogens used in our study. In particular, we observed a definitely good in vitro activity of rifaximin against several enteropathogens, such as E. coli, Shigella spp., and Salmonella spp., which is in accordance with clinical and microbiological outcomes of two recent studies of traveler's diarrhea (2; H. L. DuPont, Z. D. Jiang, C. D. Ericsson, J. J. Mathewson, J. Aldachi, E. Palazini, L. S. Riopel, D. Ashley, and F. Martinez-Sandoval, Abstr. 39th Intersci. Conf. Antimicrob. Agents Chemother., abstr. 2227, p. 698, 1999).

A matched case-control study was conducted in the Maternal and Child Health Clinic (MCH) in Ifakara, Tanzania, during the rainy season in order to elucidate the risk factors for and etiology of diarrheal diseases in children under 5 years of age. Cases (103) and controls (206) were matched for sex and age group. Precoded questionnaires with demographic details, clinical history, and physical signs were completed. Stools samples were collected for bacterial, parasitological, and viral studies. A high number of siblings (odds ratio [OR], 0.86; P = 0.027), the number of siblings surviving (OR, 0.82; P = 0.007), the birth order (OR, 0.85; P = 0.018) and the distance from the house to the water source (OR, 0.33; P = 0.011) were associated with the risk of diarrhea. There were high rates of enteropathogen isolates in stool samples from children without diarrhea (52.23%). Shigella species were the only enteropathogen statistically related with diarrhea (OR, 2.90; P < 0.029). Enterotoxigenic, enteropathogenic, and enteroaggregative strains of Escherichia coli were not related with diarrhea, and neither were Giardia lamblia or Salmonella species.

Traveler's diarrhea (TD) is a frequent health problem among travelers abroad. Diarrheagenic Escherichia coli, Shigella spp., Salmonella spp., and Campylobacter spp. are among the most common causes of TD (3, 5). The antimicrobial resistance in Salmonella strains is an increasing problem (15). Genetic elements, such as plasmids, transposons, and integrons, carrying resistant genes have previously been reported for this microorganism (13, 14, 15). We previously studied the evolution of antimicrobial resistance and the mechanisms of resistance to several antimicrobial agents in Salmonella isolates causing TD and found different genes encoding resistant determinants (3). The aim of the present study was to determine the presence of class 1 integrons and identify the resistance genes located therein in different serotypes of TD-causing, resistant Salmonella strains obtained in the previous study. Sixteen Salmonella strains that were isolated from the stool samples of patients with TD were analyzed (1) using the Kirby-Bauer method and chosen for their resistance to at least one of the following tested antimicrobial agents: ampicillin, amoxicillin-clavulanic acid, nalidixic acid, tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, gentamicin, ciprofloxacin, amikacin, imipenem, norfloxacin, and ceftazidime. The results were interpreted according to the Clinical and Laboratory Standards Institute (formerly NCCLS) guidelines (9). The strains belonged to the following Salmonella enterica serotypes: Enteritidis (seven strains), Typhimurium (two strains), Virchow (one strain), Haifa (one strain), Goldcoast (one strain), Risseu (one strain), Paratyphi A (one strain), Kiambu (one strain), and Hadar (one strain). The presence of class 1 integrons was determined by PCR amplification (7, 16). The sequences obtained were compared to those in GenBank to identify the genes. Class 1 integrons were present in 4/16 (25%) of the resistant strains analyzed (Table ​(Table1;1; Fig. ​Fig.1).1). Three of the four strains presented one integron, whereas the fourth showed two integrons, with the integron sizes ranging from 1,050 to 1,700 bp. All integrons were sequenced to detect the gene cassettes located inside. The resistance genes located in the integrons encoded enzymes that were associated with resistance to aminoglycosides, β-lactams, trimethoprim, and chloramphenicol (Table ​(Table1).1). The prevalence of integrons among the Salmonella strains causing TD described herein is similar to that described in other reports analyzing Salmonella strains not causing TD. Class 1 integrons were found in 20, 20, and 17% of the Salmonella strains that were isolated in Spain, the United Kingdom, and China (6, 12, 17), respectively. In these studies, serotype Virchow carried an integron containing the aadA1a and dfrA1 genes and serotype Haifa carried an integron with the tetA gene (6, 12), which were different from those found in our study. We have not found any report in the scientific literature concerning the presence of integrons in Salmonella serotype Goldcoast. Moreover, the type of resistance genes that were found in the class 1 integrons agrees with previous studies that were undertaken with resistant Shigella strains causing TD (11). Serotype Kiambu had two integrons containing the aadA2 and carb-2 genes, respectively, which have also been described in different serotypes of Salmonella, such as Typhimurium, Agona, Paratyphi B, and Albany. These two integrons have been located in a genomic resistance island (SGI1) (2, 4, 8), suggesting that our strain also carries this genomic island. The range in the geographic origins of our strains containing integrons demonstrates the wide dissemination of these genetic elements. Nowadays, widespread international travel has facilitated the dissemination of multiresistant pathogenic strains throughout the world, and this has become a great public health problem (10). In addition, if resistance is associated with genes that are located in genetic elements such as plasmids, transposons, or integrons, they can be transferred and disseminated to the local bacterial population. FIG. 1. Class 1 integrons of Salmonella-resistant strains. The designation numbers of the strains are reported above each lane. Lane M, the molecular weight marker. TABLE 1. Characteristics of Salmonella strains with class 1 integrons

In the last several years, developing countries have become popular tourist destinations. The large number of travelers to these areas has brought an increase in the so-called travelers' diseases (5). These diseases are due both to the sanitary conditions encountered in some of these places and to the irresponsible attitudes of the travelers themselves. In fact, travelers' diseases may be seen as a mirror of the reality of the sanitary conditions of the tourist destinations influenced by the conduct of the travelers. Thus, analysis of the prevalence and characteristics of travelers' diseases may be considered an indirect source of sanitary information for the visited areas. Among the aforementioned diseases, traveler's diarrhea is one of the most common pathologies found among those returning from developing countries (5). Diarrhea associated with Shigella infections results in around 1,100,000 deaths each year, especially among children in developing countries (3). To study in depth the virulence determinants of this microorganism is a public health priority. Sequences homologous to Sat, a urovirulence factor of Escherichia coli, have been described for Shigella spp. (2). However, no extensive studies on the prevalence of this virulence factor among Shigella spp. have been performed. The prevalence of the sat gene in 36 Shigella sonnei and 43 Shigella flexneri isolates causing traveler's diarrhea collected during the period of 1995 to 2000 has been established in this study. The presence of the sat gene was determined by PCR amplification of 387 bp using the primers 5′-ACTGGCGGACTCATGCTGT-3′ and 5′-AACCCTGTAAGAAGACTGAGC-3′ under previously reported conditions (4). Some of the PCR products were sequenced, and all presented 100% homology to those described previously for E. coli. Overall, 44 isolates (55.69% of the total) were positive; 11 were S. sonnei (25.58% of the total number of S. sonnei isolates analyzed), while 23 were S. flexneri (63.89% of the S. flexneri isolates analyzed). Independent of its exact geographical origin, the prevalence of the sat gene has always been found to be 30 to 40% higher in S. flexneri than in S. sonnei. In both species, the higher prevalence of sat (35.71 and 71.43% in S. sonnei and S. flexneri, respectively) was found in isolates obtained from travelers returning from Latin America (Tables ​(Tables11 and ​and2).2). Using a chi-square test, such a proportion was found to be significant (P < 0.001). The results of the Mantel and Haensel stratified analysis by continent were still significant (P = 0.002). TABLE 1. Geographical distribution of the Shigella isolates TABLE 2. Geographical prevalence of the sat gene Nineteen (48.72%) out of the 39 S. flexneri strains belonged to serotype 2a. This high prevalence of S. flexneri serotype 2a might be explained by the particularly enhanced virulence of this serotype (1). Furthermore, 15 (78.95%) out of these 19 S. flexneri 2a strains were positive for the sat gene. In contrast, among the remaining 20 S. flexneri strains belonging to other serotypes, only 4 (20%) contained it. In summary, our results show a high incidence of the sat gene among clinical isolates of Shigella spp. of different intercontinental origins. Further studies are necessary to establish, with greater accuracy, the geographical distribution of this toxin, as well as its relevance as a diarrheagenic factor of Shigella spp.

The aim of the present study was to build a population pharmacokinetic (popPK) model to characterize benznidazole (BNZ) pharmacokinetics in adults with chronic Chagas disease. This study was a prospective, open-label, single-center clinical trial approved by the local ethics committee. Patients received BNZ at 2.5 mg/kg of body weight/12 h (Abarax, Elea Laboratory, Argentina) for 60 days. Plasma BNZ samples were taken several times during the study and analyzed by high-performance liquid chromatography with UV-visible detection (HPLC-UV). The popPK analysis was done with NONMEMv.7.3. Demographic and biological data were tested as covariates. Intraindividual, interoccasion, and residual variabilities were modeled. Internal and external validations were completed to assess the robustness of the model. Later on, simulations were performed to generate BNZ concentration-time course profiles for different dosage regimens. A total of 358 plasma BNZ concentrations from 39 patients were included in the analysis. A one-compartment PK model characterized by clearance (CL/ F ) and the apparent volume of distribution ( V / F ), with first-order absorption ( K a ) and elimination, adequately described the data (CL/ F , 1.73 liters/h; V / F , 89.6 liters; and K a , 1.15 h −1 ). No covariates were found to be significant for CL/ F and V / F . Internal and external validations of the final model showed adequate results. Data from simulations revealed that a dose of 2.5 mg/kg/12 h might lead to overexposure in most patients. A lower dose (2.5 mg/kg/24 h) was able to achieve trough BNZ plasma concentrations within the accepted therapeutic range of 3 to 6 mg/liter. In summary, we developed a population PK model for BNZ in adults with chronic Chagas disease. Dosing simulations showed that a BNZ dose of 2.5 mg/kg/24 h will adequately keep BNZ trough plasma concentrations within the recommended target range for the majority of patients. (This study has been registered at EudraCT under number 2011-002900-34 and at ClinicalTrials.gov under number NCT01755403.)