Survey of selected pathogens in free-ranging pinnipeds in Uruguay

Marine mammals, regarded as sentinels of aquatic ecosystem health, are exposed to different pathogens and parasites under natural conditions. We surveyed live South American fur seals Arctocephalus australis and South American sea lions Otaria flavescens in Uruguay for Leptospira spp., canine distemper virus (CDV), Mycobacterium spp., Toxoplasma gondii, and Neospora caninum. Samples were collected from 2007 to 2013. The seroprevalence of Leptospira spp. was 37.6% positive, 50.9% negative, and 11.5% suspect for A. australis (n = 61) while for O. flavescens (n = 12) it was 67% positive, 25% negative, and 8% suspect. CDV RNA was not detected in any of the analyzed samples. Most animals tested seropositive to tuberculosis antigens by WiZo ELISA (A. australis: 29/30; O. flavescens: 20/20); reactivity varied with a novel ELISA test (antigens MPB70, MPB83, ESAT6 and MPB59). Seroprevalence against N. caninum and T. gondii was 6.7 and 13.3% positive for O. flavescens and 0 and 2.2% positive for A. australis respectively. To evaluate possible sources of infection for pinnipeds, wild rats Rattus rattus and semi-feral cats Felis catus were also tested for Leptospira spp. and T. gondii respectively. Water samples tested for Leptospira revealed saprofitic L. bioflexa. Pathogenic Leptospira were detected in the kidneys of 2 rats, and cats tested positive for T. gondii (100%). These results represent a substantial contribution to the study of the health status of wild pinnipeds in Uruguay.

Seroprevalence of anti-Leptospira antibodies in equines and associated workers-Isolation of Leptospira interrogans serogroup Canicola from equine urine

To investigate seroprevalence of anti-Leptospira antibodies in equines and associated workers in Uruguay, 891 equine and 150 human sera were drawn; 212 equine urine samples were also taken for culture. Environmental conditions and equine raising or managing practices were recorded in all 72 visited establishments; epidemiological information was obtained from each worker. Microscopic agglutination technique (MAT) was performed with 10 Leptospira strains for equines and 18 for human sera, that were also studied with IgM indirect immunofluorescence (IgM-IIF). Equine titres ≥100 were considered positive, and human sera titres ≥200 suggested probable recent or past infection. Urines were cultured in Ellinghausen-McCullough-Johnson-Harris (EMJH) media; local identification of one obtained isolate with lipL32 PCR, Multiple Locus Variable number tandem repeat Analysis and partial rrs gene sequencing, were completed at Institut Pasteur, Paris. Estimated reactivity was 61.3% for equines, which was higher than the studied bovine national levels (21%) and mainly observed with Icterohaemorrhagiae serogroup (40.3%), Sejroe, Canicola, Pomona or Ballum. Aged animals from slaughterhouses and cattle farms were the most frequently positive. Multiple regression analysis confirmed a significant association between seropositivity and equine age. Only one positive culture could be fully studied, and confirmed to be Leptospira interrogans serogroup Canicola; it was added to the MAT antigen panel and revealed fairly frequent reaction with equine and human sera. Three workers (2%) showed titres = 200 with Icterohaemorrhagiae or Canicola serogroups, without recent clinical manifestations. Their attended equines reacted with the same serogroups, suggesting common source infections or infection transmitted by equines. Three other humans yielded titres = 100, and none of the 150 showed an IgM-IIF-positive result. Equines seem not to be an important origin of regional human leptospirosis, except perhaps during acute animal infection. More culture work is required to study intensity and lapses of leptospiruria, as well as to further identify circulating strains.

Tracing Back the Evolutionary Route of Enteroinvasive Escherichia coli (EIEC) and Shigella Through the Example of the Highly Pathogenic O96:H19 EIEC Clone

Enteroinvasive Escherichia coli (EIEC) cause intestinal illness through the same pathogenic mechanism used by Shigella spp. The latter species can be typed through genomic and phenotypic methods used for E. coli and have been proposed for reclassification within E. coli species. Recently the first appearance of a highly pathogenic EIEC O96:H19 was described in Europe as the causative agent of two large outbreaks that occurred in Italy and in the United Kingdom. In contrast to Shigella spp and to the majority of EIEC strains, EIEC O96:H19 fermented lactose, lacked pathoadaptive mutations, and showed good fitness in extracellular environment, similarly to non-pathogenic E. coli, suggesting they have emerged following acquisition of the invasion plasmid by a non-pathogenic E. coli. Here we describe the whole genome comparison of two EIEC O96:H19 strains isolated from severe cases of diarrhea in Uruguay in 2014 with the sequences of EIEC O96:H19 available in the public domain. The phylogenetic comparison grouped all the O96:H19 strains in a single cluster, while reference EIEC strains branched into different clades with Shigella strains occupying apical positions. The comparison of the virulence plasmids showed the presence of a complete conjugation region in at least one O96:H19 EIEC. Reverse Transcriptase Real Time PCR experiments confirmed in this strain the expression of the pilin-encoding gene and conjugation experiments suggested its ability to mobilize an accessory plasmid in a recipient strain. Noteworthy, the tra region was comprised between two reversely oriented IS600 elements, which were also found as remnants in another EIEC O96:H19 plasmid lacking the tra locus. We hypothesize that an IS-mediated recombination mechanism may have caused the loss of the conjugation region commonly observed in EIEC and Shigella virulence plasmids. The results of this study support the hypothesis of EIEC originating from non-pathogenic E. coli through the acquisition of the virulence plasmid via conjugation. Remarkably, this study showed the ability of a circulating EIEC strain to mobilize plasmids through conjugation, suggesting a mechanism for the emergence of novel EIEC clones.

Presence of genes encoding enterotoxins in Staphylococcus aureus isolates recovered from food, food establishment surfaces and cases of foodborne diseases

The aim of this study was to describe the microbiological characteristics and profile of genes encoding enterotoxins in 95 Staphylococcus aureus isolates obtained between April 2011 and December 2014 from foodstuffs, persons and surfaces of retail food stores. After microbiological identification and antimicrobial susceptibility testing, polymerase chain reactions (PCR) were performed, targeting sea, seb, sec, sed and see genes that code for classical enterotoxins (ET) A-E, and three additional genes: seg , seh and sei , coding for so-called "new enterotoxins" G, H and I. The isolates were characterized by Pulsed Field Gel Electrophoresis (PFGE), and five selected isolates were further analyzed through Multi Locus Sequence Typing (MLST). It is noteworthy that 54.7% of the examined isolates harbored one or more of the investigated ET gene types. Most positive isolates carried more than one ET gene up to five types; seg was the most frequent ET gene, followed by sei. Five enterotoxin-coding isolates also coded for some antimicrobial resistance genes. Two of them, and four additional non-enterotoxic isolates carried erm genes expressing inducible clindamycin resistance. PFGE-types were numerous and diverse, even among enterotoxin-coding strains, because most isolates did not belong to known foodborne outbreaks and the sampling period was long. MLST profiles were also varied, and a new ST 3840 was described within this species. ST 88 and ST 72 enterotoxin-coding isolates have been identified in other regions in association with foodborne outbreaks. This manuscript reports the first systematic investigation of enterotoxin genes in S. aureus isolates obtained from foodstuffs and infected people in Uruguay.

Seroprevalence of leptospirosis in human groups at risk due to environmental, labor or social conditions

Leptospirosis is important in Uruguay due to the economic loss caused by the diseases of production animals, mainly bovines, and also due to frequent human infection. We decided to study anti-Leptospira antibodies in the sera of dairy workers, rice laborers, veterinarians, suburban slum dwellers and garbage recyclers. Our aims were to estimate the seroprevalence of infection by Leptospira spp. in these people at risk, the relative importance of the known risk factors associated with infection, and the impact of human infections in each setting. Groups at risk were identified and 35 visits to their locations were made, conducting field surveys and exchange talks for information and education. Simple epidemiological questionnaires were administered and sera samples were taken from 308 persons. The microagglutination Technique (MAT) and the IgM Indirect Immunofluorescence (IIF) assay were employed to detect antibodies. Environmental water samples, canine and equine sera were also examined. More than 45% of human sera were reactive and the studied groups were confirmed to be widely exposed to infection. Female sera were frequently reactive, though most illnesses occur in men, and the most severe cases in elderly males; the emergence and evolution of the disease may strongly depend on the host condition and functions. Animal contact and unsafe water usage were the main identified risk factors to be considered in prevention. Fifty per cent of the studied horses showed a positive MAT reaction. The underdiagnosis of the illness and its long-term symptoms require further study, as well as greater health and social attention efforts.

Diarrheagenic Escherichia coli Associated with Acute Gastroenteritis in Children from Soriano, Uruguay

INTRODUCTION

Acute diarrheal disease still deserves worldwide attention due to its high morbidity and mortality, especially in developing countries. While etiologic determination is not mandatory for management of all individual cases, it is needed for generating useful epidemiologic knowledge. Diarrheagenic Escherichia coli (DEC) are relevant enteropathogens, and their investigation requires specific procedures to which resources and training should be dedicated in reference laboratories.

METHODOLOGY

Following the hypothesis that enteric pathogens affecting children in towns located in the interior of Uruguay may be different from those found in Montevideo, we conducted a diagnostic survey on acute diarrheal disease in 83 children under 5 years of age from populations in the south of the country.

RESULTS

DEC pathotypes were the only bacterial pathogens found in diarrheal feces (20.48%), followed by rotavirus (14.45%) and enteric adenovirus (4.81%). Atypical EPEC (aEPEC) was the most frequent DEC pathotype identified, and unexpectedly, it was associated with bloody diarrheal cases. These patients were of concern and provided with early consultation, as were children who presented with vomiting, which occurred most frequently in rotavirus infections. aEPEC serotypes were diverse and different from those previously reported in Montevideo children within the same age group and different from serotypes identified in regional and international studies. Enteroinvasive (EIEC) O96 : H19, associated with large outbreaks in Europe, was also isolated from two patients. Antibiotic susceptibility of pathogenic bacteria identified in this study was higher than that observed in previous national studies, which had been mainly carried out in children from Montevideo.

CONCLUSION

The reduced number of detected species, the marked prevalence of aEPEC, the scarce resistance traits, and the diverse range of serotypes in the virulent DEC identified in this study confirm that differences exist between enteropathogens affecting children from interior towns of Uruguay and those circulating among children in Montevideo.

Isolation of pathogenic Leptospira strains from naturally infected cattle in Uruguay reveals high serovar diversity, and uncovers a relevant risk for human leptospirosis

Leptospirosis is a neglected zoonosis with worldwide distribution. The causative agents are spirochete bacteria of the Leptospira genus, displaying huge diversity of serovars, the identity of which is critical for effective diagnosis and vaccination purposes. Among many other mammalian species, Leptospira infects cattle, eliciting acute signs in calves, and chronic disease in adult animals often leading to abortions. In South America, and including in Uruguay, beef and dairy export are leading sources of national income. Despite the importance of bovine health, food safety, and bovine-related dissemination of leptospirosis to humans, extremely limited information is available as to the identity of Leptospira species and serovars infecting cattle in Uruguay and the South American subcontinent. Here we report a multicentric 3-year study resulting in the isolation and detailed characterization of 40 strains of Leptospira spp. obtained from infected cattle. Combined serologic and molecular typing identified these isolates as L. interrogans serogroup Pomona serovar Kennewicki (20 strains), L. interrogans serogroup Canicola serovar Canicola (1 strain), L. borgpetersenii serogroup Sejroe serovar Hardjo (10 strains) and L. noguchii (9 strains). The latter showed remarkable phenotypic and genetic variability, belonging to 6 distinct serogroups, including 3 that did not react with a large panel of reference serogrouping antisera. Approximately 20% of cattle sampled in the field were found to be shedding pathogenic Leptospira in their urine, uncovering a threat for public health that is being largely neglected. The two L. interrogans serovars that we isolated from cattle displayed identical genetic signatures to those of human isolates that had previously been obtained from leptospirosis patients. This report of local Leptospira strains shall improve diagnostic tools and the understanding of leptospirosis epidemiology in South America. These strains could also be used as new components within bacterin vaccines to protect against the pathogenic Leptospira strains that are actually circulating, a direct measure to reduce the risk of human leptospirosis.

Several species of the genus Leptospira cause leptospirosis, a disease that is transmitted from animals to humans (zoonosis). Leptospirosis is the most extended zoonosis worldwide, with over a million human cases each year. Leptospira spp. infect a broad range of wildlife and domestic animals, including cattle. In several South American countries beef and dairy exports rank among the most important national income sources, explaining why in Uruguay cattle outnumber human population by a factor of 4. Yet, we did not know which Leptospira species and serovariants (serovars) circulate among Uruguayan cattle. Current serologic diagnostic methods and whole killed-cell vaccination approaches, critically depend on using the proper serovars, which are hugely variable in Leptospira spp. from different regions of the world. Through a multidisciplinary consortium effort, we now report the isolation and typing of 40 strains of pathogenic Leptospira spp. An unexpectedly large variation in terms of species and serovars was found. These data are extremely important: 1- to improve diagnostics by updating the available reference antigen panels; 2- to evaluate the efficacy of novel vaccines; and, 3- to implement efficacious bovine vaccination as a means of reducing the incidence of bovine and human leptospirosis.

Characterization of Leptospira isolates from humans and the environment in Uruguay

Laboratory diagnosis of human leptospirosis usually relies on indirect methods exploring specific immune response. Isolation and identification of the involved strains are cumbersome, but can provide biological resources for pathogenic studies and relevant information for guiding prevention and control measures. The aim of the research we are hereby reporting was the characterization of Leptospira isolates obtained from humans and the environment in Uruguay. Blood cultures were performed from early samples of 302 Uruguayan patients, mainly rural workers, and from 36 water samples taken from their living or working environments. Eight human isolates and seven environmental isolates were obtained and analyzed by end point Polymerase Chain Reaction (PCR), Multilocus Variable Number of Tandem Repeat Analysis (MLVA) and other molecular methods. Human isolates corresponded to several serogroups and serovars of Leptospira interrogans and Leptospira kirschneri species, probably reflecting the infection with similar involved Leptospira species and serovars of an extended animal reservoir in rural settings of the country, mostly dedicated to meat and dairy production. Culture-positive patients were older than usually affected workers, and presented signs and symptoms of severe illness. A high organic and circulating bacterial burden may explain an easier positive result from these workers’ samples. Environmental isolates were mainly identified as Leptospira biflexa strains, with a single L. meyeri isolate of uncertain significance.

Prevalence and serotype distribution of Listeria monocytogenes isolated from foods in Montevideo-Uruguay

The aim of this work was to study the prevalence of Listeria monocytogenes in foods obtained in retail shops and food industries located in Montevideo-Uruguay, and to identify the serogroups of the obtained isolates. Three-thousand one-hundred and seventy-five food samples (frozen, deli meats, ready-to-eat and cheese) were analyzed. The obtained isolates were serogrouped by multiplex PCR and serotyped by conventional procedure. Genetic comparisons were performed using pulsed-field gel electrophoresis on a sub-set of isolates belonging to the same serotype successively recovered from the same establishment. L. monocytogenes was isolated from 11.2% of samples. The highest prevalence was observed in frozen foods (38%), followed by cheese (10%). 1/2b and 4b were the most frequently identified serotypes. In six of 236 analyzed establishments we successively recovered L. monocytogenes isolates belonging to the same serotype. Most of them corresponded to serotype 1/2b. Pulsed-field gel electrophoresis profiles suggest that at least 33% of L. monocytogenes 1/2b isolates are genetically related and that may remain viable for prolonged periods. The observed prevalence of L. monocytogenes was lower than reported in neighboring countries. Our findings highlight the role that frozen foods may play in the spread of this pathogen, and the relevance of serotypes 1/2b and 4b.

Síndrome urémico hemolítico en Uruguay. Aspectos microbiológicos y clínicos, aportes para su conocimiento regional

Introducción: El síndrome urémico hemolítico (SUH) es una enfermedad de severidad variable que afecta sobre todo a niños menores de 5 años. Está definido por la tríada anemia hemolítica microangiopática, trombocitopenia e insuficiencia renal aguda. La mayoría de los casos aparecen luego de un episodio de diarrea aguda, causado por cepas de Escherichia coli productoras de toxina Shiga (STEC). Objetivo: Establecer las características de las cepas STEC recuperadas de niños con SUH, e informar sobre algunos aspectos clínicos y características epidemiológicas de estos casos. Materiales y métodos: Se realizó un estudio descriptivo que incluyó niños con SUH. La detección de las cepas STEC se realizó por PCR a partir de cultivos de materias fecales. En cada cepa se estableció el genotipo, serotipo y perfil de susceptibilidad a los antibióticos. Resultados: Se estudiaron 43 niños con SUH. Los casos ocurrieron predominantemente en los meses cálidos, afectando niños provenientes de hogares ubicados fuera de la capital y con cobertura privada de salud. La mayoría presentaban el antecedente de diarrea con sangre y 70% habían recibido antibióticos antes de obtener las muestras. En 7 niños se recuperaron 8 cepas STEC; 7 correspondieron a serogrupos no-O157. Todas portaban los genes eae y ehxA. Conclusiones: La mayoría de los casos ocurren en meses cálidos, en niños que cursaron diarrea con sangre, provenientes de hogares ubicados fuera de la ciudad capital. Los cultivos STEC no-O157 fueron los más prevalentes.

Hemolytic uremic syndrome with mild renal involvement due to Shiga toxin-producing Escherichia coli (STEC) O145 strain

Hemolytic uremic syndrome (HUS) is a disorder characterized by the presence of the classic triad: microangiopathic hemolytic anemia, thrombocytopenia and acute renal injury. HUS without acute renal failure can be confused with other hematologic diseases. An infantile HUS caused by a Shiga-toxin-producing Escherichia coli (STEC) O145 strain carrying genotype stx2, ehxA, eae subtype β1 is herein reported. The infant did not require dialysis during the acute stage of HUS, evolved favorably, maintained normal blood pressure and normal renal function and had no recurrence until the last control. This could be due to several factors, such as the characteristics of infecting STEC strain and a reduction in host susceptibility to renal injury. This report highlights the regional participation of non-O157 STEC in childhood diseases and the importance of performing active surveillance for all forms of HUS.

Usefulness of real-time PCR assay targeting lipL32 gene for diagnosis of human leptospirosis in Uruguay

INTRODUCTION

Assays based on DNA amplification can provide information that contributes to the initial management of patients with leptospirosis. However, these have not been adopted in Uruguay. Our aim was to evaluate the performance of the lipL32 real-time PCR (qPCR) for diagnosis of leptospirosis.

METHODOLOGY

We analyzed by microscopic agglutination test (MAT) and lipL32 qPCR serum samples from 183 patients with suspected leptospirosis. To establish the analytical sensitivity of the qPCR, experimentally spiked samples with known amounts of Leptospira interrogans were analyzed.

RESULTS

The analytical sensitivity of the qPCR was 102 leptospires/mL. In 98 patients MAT results were negative meanwhile 85 showed positive reactions, revealing acute infections. Twenty six acute-phase sera of these 85 patients showed a positive signal by qPCR (diagnostic sensitivity 30%). In these patients the average time between onset of symptoms and collection of the first sample was 8 days. In patients with negative results for qPCR and positive MAT results (n=59) the average interval between onset of symptoms and collection of the first sample was 13 days. The qPCR did not yield false positive results.

CONCLUSIONS

The qPCR had a lower diagnostic sensitivity than MAT and a higher cost. However, it allowed to make an early diagnosis in 26 patients. In patients with confirmed acute infections and negative results by qPCR, more than 8 days had elapsed between the onset of the illness and extraction of the first serum sample. Our data support that the qPCR from sera have clinical utility within the first week of illness.

Two cases of urinary tract infection caused by Shiga toxin-producing Escherichia coli O157:H7 strains

STEC strains can infect extra-intestinal sites such as the human urinary tract and sometimes cause severe complications. We report two cases of urinary tract infection caused by STEC in two elderly women with comorbidities. Although both strains belonged to the O157:H7 serotype and carried genes associated with severe illness, none of the patients developed hemolytic uremic syndrome (HUS). These findings provide additional evidence for the presence of these agents in our country and in the region, and highlight the need to maintain an active surveillance system of HUS cases, placing special emphasis on the study of other sites of infection in patients with non-diarrheal HUS.

A ten-year follow-up of human leptospirosis in Uruguay: an unresolved health problem

Leptospira spp. are delicate bacteria that cannot be studied by usual microbiological methods. They cause leptospirosis, a zoonotic disease transmitted to humans through infected urine of wild or domestic animals. We studied the incidence of this disease in the Uruguayan population, its epidemiologic and clinical features, and compared diagnostic techniques. After examining 6,778 suspect cases, we estimated that about 15 infections/100,000 inhabitants occurred yearly, affecting mainly young male rural workers. Awareness about leptospirosis has grown among health professionals, and its lethality has consequently decreased. Bovine infections were probably the principal source of human disease. Rainfall volumes and floods were major factors of varying incidence. Most patients had fever, asthenia, myalgias or cephalalgia, with at least one additional abnormal clinical feature. 30-40% of confirmed cases presented abdominal signs and symptoms, conjunctival suffusion and altered renal or urinary function. Jaundice was more frequent in patients aged > 40 years. Clinical infections followed an acute pattern and their usual outcome was complete recovery. Laboratory diagnosis was based on indirect micro-agglutination standard technique (MAT). Second serum samples were difficult to obtain, often impairing completion of diagnosis. Immunofluorescence was useful as a screening test and for early detection of probable infections.

Genomic Comparison of the Closely Related Salmonella enterica Serovars Enteritidis and Dublin

The Enteritidis and Dublin serovars of Salmonella enterica are closely related, yet they differ significantly in pathogenicity and epidemiology. S. Enteritidis is a broad host range serovar that commonly causes gastroenteritis and infrequently causes invasive disease in humans. S. Dublin mainly colonizes cattle but upon infecting humans often results in invasive disease.To gain a broader view of the extent of these differences we conducted microarray-based comparative genomics between several field isolates from each serovar. Genome degradation has been correlated with host adaptation in Salmonella, thus we also compared at whole genome scale the available genomic sequences of them to evaluate pseudogene composition within each serovar.Microarray analysis revealed 3771 CDS shared by both serovars while 33 were only present in Enteritidis and 87 were exclusive to Dublin. Pseudogene evaluation showed 177 inactive CDS in S. Dublin which correspond to active genes in S. Enteritidis, nine of which are also inactive in the host adapted S. Gallinarum and S. Choleraesuis serovars. Sequencing of these 9 CDS in several S. Dublin clinical isolates revealed that they are pseudogenes in all of them, indicating that this feature is not peculiar to the sequenced strain. Among these CDS, shdA (Peyer´s patch colonization factor) and mglA (galactoside transport ATP binding protein), appear also to be inactive in the human adapted S. Typhi and S. Paratyphi A, suggesting that functionality of these genes may be relevant for the capacity of certain Salmonella serovars to infect a broad range of hosts.

Bacterial pathogens associated with bloody diarrhea in Uruguayan children

Diarrheal disease continues to be a serious health problem, especially in developing countries. Bloody diarrhea represents approximately 20-30% of all cases and has higher morbidity and mortality. Treatment with antibiotics is beneficial in cases of Shigella, Campylobacter, Yersinia and Salmonella infection, principally in those children with a higher risk of invasive disease. The aims of this study were to detect the bacterial agents associated with bloody diarrhea in children and to determine their antimicrobial susceptibility patterns. Between June 2001 and January 2008, 249 children with bloody diarrhea were studied. Shigella and Shiga toxin-producing Escherichia coli (STEC) were recovered from 48 (19.3%) and 3 (1.2%) of the total of cases, respectively. In 49 out of 249 children, in whom other enteropathogens were investigated, we recovered Campylobacter jejuni from 7 children (14.3%), Salmonella spp. from 2 (4.1%) and Aeromonas spp. from 1 (2%) in addition to Shigella from 7 children (14.3%). Thirty-four (70%) Shigella isolates showed resistance to ampicillin and 13 (27%) to trimethoprim-sulfamethoxazole. All Shigella isolates were susceptible to nalidixic acid, ciprofloxacin and ceftriaxone. Salmonella and STEC isolates were susceptible to all antibiotics assayed. Thus, the use of trimethoprim-sulfamethoxazole or ampicillin would not be appropriate for the empirical treatment of Shigella - associated diarrhea.

Genomic and phenotypic variation in epidemic-spanning Salmonella enterica serovar Enteritidis isolates

BACKGROUND

Salmonella enterica serovar Enteritidis (S. Enteritidis) has caused major epidemics of gastrointestinal infection in many different countries. In this study we investigate genome divergence and pathogenic potential in S. Enteritidis isolated before, during and after an epidemic in Uruguay.

RESULTS

266 S. Enteritidis isolates were genotyped using RAPD-PCR and a selection were subjected to PFGE analysis. From these, 29 isolates spanning different periods, genetic profiles and sources of isolation were assayed for their ability to infect human epithelial cells and subjected to comparative genomic hybridization using a Salmonella pan-array and the sequenced strain S. Enteritidis PT4 P125109 as reference. Six other isolates from distant countries were included as external comparators.Two hundred and thirty three chromosomal genes as well as the virulence plasmid were found as variable among S. Enteritidis isolates. Ten out of the 16 chromosomal regions that varied between different isolates correspond to phage-like regions. The 2 oldest pre-epidemic isolates lack phage SE20 and harbour other phage encoded genes that are absent in the sequenced strain. Besides variation in prophage, we found variation in genes involved in metabolism and bacterial fitness. Five epidemic strains lack the complete Salmonella virulence plasmid. Significantly, strains with indistinguishable genetic patterns still showed major differences in their ability to infect epithelial cells, indicating that the approach used was insufficient to detect the genetic basis of this differential behaviour.

CONCLUSION

The recent epidemic of S. Enteritidis infection in Uruguay has been driven by the introduction of closely related strains of phage type 4 lineage. Our results confirm previous reports demonstrating a high degree of genetic homogeneity among S. Enteritidis isolates. However, 10 of the regions of variability described here are for the first time reported as being variable in S. Enteritidis. In particular, the oldest pre-epidemic isolates carry phage-associated genetic regions not previously reported in S. Enteritidis. Overall, our results support the view that phages play a crucial role in the generation of genetic diversity in S. Enteritidis and that phage SE20 may be a key marker for the emergence of particular isolates capable of causing epidemics.

Prevalence and dissemination of the Ser315Thr substitution within the KatG enzyme in isoniazid-resistant strains of Mycobacterium tuberculosis isolated in Uruguay

The aim of this study was to determine the prevalence of Ser315Thr substitution in isoniazid (INH)-resistant strains of Mycobacterium tuberculosis in Uruguay. The katG gene of 62 INH-resistant strains was analysed by an RFLP-PCR assay. PCR products were digested with MspI to detect Ser315Thr and Arg463Leu substitutions. A total of 16 of the 62 (26 %) INH-resistant strains analysed had a Ser315Thr substitution. Only one INH-resistant strain had an Arg463Leu substitution and two strains had a deletion in katG. Of the 16 strains with Ser315Thr, 15 showed different profiles using a double-repetitive-element PCR assay, demonstrating that there was no local dissemination of any particular strain. These findings are in agreement with published data from regions where the prevalence of tuberculosis (TB) is intermediate and may be due in part to the success of the local TB control programme.

Surveillance of antibiotic resistance evolution and detection of class 1 and 2 integrons in human isolates of multi-resistant Salmonella Typhimurium obtained in Uruguay between 1976 and 2000

OBJECTIVES

To study the evolution of antibiotic resistance in isolates of Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella Typhimurium) obtained in Uruguay between the years 1976 and 2000, and to determine the incidence of class 1 and 2 integrons in the multi-resistant isolates.

METHODS

We studied 258 strains of Salmonella Typhimurium from various sources, isolated between 1976 and 2000. We determined the evolution of antibiotic resistance and the distribution of class 1 and 2 integrons in all isolates by means of disk diffusion assays and PCR.

RESULTS

During the period 1989-2000 resistance to streptomycin was 56.8%, tetracycline 13.6%, sulfonamides 11.2%, and ampicillin 7.2%. Resistance to gentamicin, kanamycin, chloramphenicol, and nalidixic acid were lower than 5%; no resistance was detected to fluoroquinolones, oxyiminocephalosporins, and amikacin. These results show a dramatic decrease with respect to values found in the period 1976-1988. In this period, resistance to streptomycin was 63.2%, tetracycline 36.8%, sulfonamides 32.3%, and ampicillin 27.8%. Throughout the two periods, 29 multi-resistant Salmonella Typhimurium strains were isolated harboring some class of integron: 15 strains had only intI2, 11 strains presented both intI1 and intI2, and three isolates only intI1.

CONCLUSIONS

Our results show a marked decrease in resistance throughout these years, along with a correlation between resistance to different antibiotics and the presence of integrons.

[Detection and characterization of Shiga toxin-producing Escherichia coli from clinical cases and food in Uruguay]

We have assessed the frequency of Shiga toxin-producing Escherichia coil (STEC) in clinical and food samples as well as studied the genotypic and phenotypic characteristics of the recovered strains. One hundred ninety eight fecal samples from children with bloody diarrhea (BD), 14 from children with hemolytic uremic syndrome (HUS), 220 ground beef samples and 4 STEC isolates from other beef-derived products were analyzed. The STEC strains were isolated from 3 (1.5%) children with bloody diarrhea, 1 (7%) from a child with HUS and 4 (1.8%) from ground beef samples. All strains were eae and ehxA positive. The serotypes found were: O157:H7 (9 strains), O26:H11 (2), O111: NM (1) and O145:HNT (1). All O157:H7 STEC strains harbored the eae subtype gamma1, O26:H11 and O145:HNT strains, subtype beta1 and O111:NM strain, subtype gamma2/theta. The STEC strains of the same serogroup showed high genetic diversity. In Uruguay, STEC is not frequently isolated from cases of bloody diarrhea in children. However, all the recovered STEC strains carried the genes associated with severe disease and 2 out of 3 children infected with STEC developed HUS. Ground beef and other food products might be important vehicles for O157:H7 strains.

Shiga toxin 2-producing Acinetobacter haemolyticus associated with a case of bloody diarrhea

We report the first Shiga toxin 2-producing Acinetobacter haemolyticus strain that was isolated from the feces of a 3-month-old infant with bloody diarrhea. Usual enteropathogenic bacteria were not detected. This finding suggests that any Shiga toxin-producing microorganism capable of colonizing the human gut may have the potential to cause illness.

Association of broad-spectrum antibiotic use with faecal carriage of oxyiminocephalosporin-resistant enterobacteriaceae in an intensive care unit

The link between administration of antibiotics and detection of third-generation-cephalosporin-resistant (TGCR) enterobacteriaceae in faeces was studied in patients in a burns intensive care unit (ICU). The presence of extended-spectrum beta-lactamase producers was also determined in these isolates. At least two rectal swab samples were taken from 43 of 72 patients admitted to the ICU from January 1998 to June 1999. Antibiotic resistance tests were performed for all isolated enterobacteriaceae using the methods of the National Committee for Clinical Laboratory Standards. Only 10 out of 30 antibiotic-treated patients showed TGCR enterobacteriaceae in faeces. Fisher's exact test showed a relationship between the administration of oxyiminocephalosporins (third-generation cephalosporins) (P=0.002) or carbapenems (P=0.003) and the isolation of TGCR enterobacteriaceae from faeces. The administration of oxyiminocephalosporins led to the selection of resistant strains in the faecal flora.

[Genetic environment of CTX-M-2 in Klebsiella pneumoniae isolates from hospitalized patients in Uruguay]

We studied two CTX-M-2-producing Klebsiella pneumoniae clinical strains, K96005 and K13, isolated from hospitalized patients in Uruguay, during 1996 and 2003, respectively. The genomic surroundings of bla(CTX-M-2) were characterized by PCR-mapping and DNA sequencing. Our results show that blaCTX-M-2 is included in a complex class-1 integron (InK13), associated with an orf513 in both isolates. The genetic array of the integron, aac(6')-lb, bla(OxA,2), orfD (gene cassette region), associated with an orf513-bla(CTX-M-2), seems to be widely disseminated over the Rio de la Plata region.

New TEM-derived extended-spectrum beta-lactamase and its genomic context in plasmids from Salmonella enterica serovar derby isolates from Uruguay

A small (8.2-kb) ColE1 plasmid encoding TEM-144 (a new beta-lactamase with a ceftazidimase profile) was sequenced by a gene-walking strategy. The bla(TEM) allele was carried on a Tn2 element, disrupting a Rom protein gene. TEM-144 differs from TEM-1 by two mutations (R164C and E240K) and from the ceftazidime-hydrolyzing TEM-91 by one mutation (T182M).

Enteropathogenic Escherichia coli strains carrying genes encoding the PER-2 and TEM-116 extended-spectrum beta-lactamases isolated from children with diarrhea in Uruguay

We studied 13 extended-spectrum beta-lactamase (ESBL)-producing enteropathogenic Escherichia coli isolates from children suffering acute diarrhea in Uruguay. ESBL characterization in crude extracts showed a single band at pI 5.4. PCR amplification and sequencing data allowed identification of blaPER-2 and blaTEM-116. Retrospective analysis suggests that these strains were disseminated in the community, even if unnoticed, prior to their access to the hospital environment more than a decade ago.

An attenuated Salmonella Enteritidis strain derivative of the main genotype circulating in Uruguay is an effective vaccine for chickens

We have recently reported that Salmonella enterica serovar Enteritidis (S. Enteritidis) strains circulating in Uruguay, are unevenly distributed among different genetic subtypes, with a predominant genotype that is a common contaminant of poultry-derived food and that accounts for the vast majority of human cases of food-borne disease. Herein, we describe the construction of a genetically-defined aroC derivative (LVR02) of a local strain of S. Enteritidis belonging to the major genetic type. We demonstrated the attenuation and the immunogenicity of that strain in a mouse model, and evaluated it as a vaccine for commercial layer chickens. LVR02 proved to be stable, attenuated, innocuous, immunogenic and to induce protective immunity against a S. Enteritidis challenge when used for oral vaccination. A single oral dose of LVR02 administered to newly hatched chickens induced protection against oral challenge with the parental virulent strain, preventing systemic and persistent intestinal infection and significantly reducing the shedding of the challenge strain in birds' feces. A second vaccine dose at 15 days post-hatching boosted the immunogenicity of the vaccine, and strengthened the protection achieved with a single dose. This strain may represent the basis of a live vaccine to be included in national control programs to reduce circulation of this pathogen in the country.

Comparative molecular study of Mycobacterium tuberculosis strains, in times of antimicrobial drug resistance

Strains of Mycobacterium tuberculosis were compared using two DNA fingerprinting techniques: Restriction Fragment Length Polymorphism (RFLP) and Double-Repetitive-Element-PCR (DRE-PCR). Two of these strains: IH1 (susceptible to isoniazid) and IH2 (resistant to isoniazid) were recovered from cases of pulmonary tuberculosis which occurred in two brothers who lived together. The first one was recognized on July 1999, and the second was diagnosed one year later. IH1 and IH2 showed the same pattern of bands with both molecular tests. These results suggest that single drug chemoprophylaxis may occasionally select resistant strains for that drug, which can eventually cause disease and be recognized through these tests. Strains IH3, IH4 and IH5 were obtained from sputum samples of 3 different patients, and intra-laboratory cross-contamination was suspected when it was realized that the 3 positive materials had been consecutively processed the same day by the same worker in the same biological safety cabinet. Again, the 3 strains revealed identical band patterns with RFLP and DRE-PCR, confirming the posed suspicion. The results with DRE-PCR were obtained after only 8 hours of work, without the need for subcultures. This procedure allows quick correction of treatment conducts, avoiding unnecessary exposure of people and bacteria to antimicrobial drugs.

Random amplified polymorphic DNA and phenotyping analysis of Salmonella enterica serovar enteritidis isolates collected from humans and poultry in Uruguay from 1995 to 2002

Molecular and phenotyping techniques were applied to study Salmonella enterica serovar Enteritidis strains both from human cases of infection and of avian origin isolated in Uruguay from 1995 to 2002. A group of 62 isolates was subjected to random amplified polymorphic DNA (RAPD) assay and analysis of antibiotic resistance patterns. Twenty-one of these strains were further characterized by phage typing and analysis of their protein expression profiles. RAPD fingerprinting with five different primers discriminated 10 different genetic profiles. Of the 62 strains tested, 48 had a single major genetic profile, whereas the other nine profiles were evenly distributed among the other strains. The genetic diversity was greater among strains of animal origin than among isolates of human origin. Comparative examination of the results obtained by RAPD analysis and phenotypic analysis and by strain source provided evidence of the reliable discriminatory power of RAPD analysis in our study. Six avian isolates with antibiotic resistance were detected: two were nalidixic acid resistant and four had a particular beta-lactam resistance pattern. The last four isolates all had the same unusual phage type (phage type 4b); however, RAPD analysis differentiated them into two groups. Two isolates with unique RAPD profiles were recovered from distinct human cases, suggesting that the technique differentiates unrelated strains. Overall, the results show the existence of a predominant genetic type that is present in poultry and that is transmitted to humans. There are also several other genotypes, but only a few of them could be recovered from human sources, suggesting the existence of different pathogenic traits among strains circulating in the country.

Etiology of children's diarrhea in Montevideo, Uruguay: associated pathogens and unusual isolates

We studied microorganisms associated with infant diarrhea in a group of 256 children admitted to a public pediatric hospital in Montevideo, Uruguay. Diagnostic procedures were updated to optimize detection of potential pathogens, which were found in 63.8% of cases, and to be able to define their characteristics down to molecular or antigenic type. Coinfection with two or more agents was detected in more than one-third of positive studies. Escherichia coli enteric virotypes, especially enteropathogenic E. coli (EPEC), were shown to be prevalent. Rotavirus, Cryptosporidium, Campylobacter (mainly Campylobacter jejuni), and Shigella flexneri were also often identified. Enterotoxigenic E. coli, Salmonella, and Giardia lamblia were sporadically recognized. Unusual findings included two enteroinvasive E. coli strains, one Shigella dysenteriae 2 isolate, and a non-O:1 Vibrio cholerae culture. EPEC bacteria and S. flexneri (but not Salmonella) showed unusually frequent antimicrobial resistance, especially towards beta-lactam antibiotics, which is the subject of ongoing work.

Analysis of the O-antigen chain length distribution during extracellular and intracellular growth of Shigella flexneri

This study has established that there were no changes in the general structure of LPS of Shigella flexneri M90T either when the bacteria grew free in the cytoplasm of the eucaryotic host cell or during extracellular growth in liquid LB medium at 37 degrees C. In both cases there was a similar bi-modal O-antigen chain length distribution with the mean modal values between 1 and 2, and between 11 and 14 subunits. This suggests that the intracellular localization is not a significant stimulus perceived by Shigella to regulate the length of its O-side chains. However, when the bacteria grew under extracellular conditions (liquid medium) at 30 degrees C, even though there were no changes in the modal values, the pattern of the O-antigen chain length distribution of LPS was different, with an increase in the amount of the long chains relative to the short chains.