Outbreak of a Cluster with Epidemic Behavior due to Serratia marcescens after colistin administration in a hospital setting

Serratia marcescens causes health care-associated infections with important morbidity and mortality. Particularly, outbreaks produced by multidrug-resistant isolates of this species, which is already naturally resistant to several antibiotics, including colistin, are usually described with high rates of fatal outcomes throughout the world. Thus, it is important to survey factors associated with increasing frequency and/or emergence of multidrug-resistant S. marcescens nosocomial infections. We report the investigation and control of an outbreak with 40% mortality due to multidrug-resistant S. marcescens infections that happened from November 2007 to April 2008 after treatment with colistin for Acinetobacter baumannii meningitis was started at hospital H1 in 2005. Since that year, the epidemiological pattern of frequently recovered species has changed, with an increase of S. marcescens and Proteus mirabilis infections in 2006 in concordance with a significant decrease of the numbers of P. aeruginosa and A. baumannii isolates. A single pulsed-field gel electrophoresis (PFGE) cluster of S. marcescens isolates was identified during the outbreak. When this cluster was compared with S. marcescens strains (n = 21) from 10 other hospitals (1997 to 2010), it was also identified in both sporadic and outbreak isolates circulating in 4 hospitals in Argentina. In132::ISCR1::blaCTX-M-2 was associated with the multidrug-resistant cluster with epidemic behavior when isolated from outbreaks. Standard infection control interventions interrupted transmission of this cluster even when treatment with colistin continued in several wards of hospital H1 until now. Optimizing use of colistin should be achieved simultaneously with improved infection control to prevent the emergence of species naturally resistant to colistin, such as S. marcescens and P. mirabilis.Fil: Merkier, Andrea Karina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Rodríguez, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Togneri, Ana. Hospital Evita. Servicio de Infectología. Laboratorio de Bacteriología; ArgentinaFil: Brengio, Silvia Diana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Mendoza. Instituto Argentino de Investigaciones de Zonas Aridas; Argentina. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Osuna, Carolina. Hospital Evita. Servicio de Infectología. Laboratorio de Bacteriología; ArgentinaFil: Pichel, Mariana. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Cassini, Marcelo Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas. Grupo de Estudios en Ecología de Mamíferos; ArgentinaFil: Centron, Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Serratia marcescens Argentinean Collaborative Group. No especifíca

Isolation and characterization of <i>Salmonella enterica</i> from Antarctic wildlife

In recent years, the human presence in Antarctica has increased and as a consequence, the possibility of microorganisms’ introduction. The aims of this work were to determine the presence of Salmonella enterica in Antarctic seabirds and sea mammals, to characterize the isolates identified, and to determine the genetic relation of Antarctic S. enterica isolates among them and compare with isolates of human, animal, and food sources recovered in Argentina. During the summer 2000 and 2002 in Potter Peninsula, and during the summer 2001 and 2003 in Hope Bay, a total of 1,739 fecal samples from Antarctic animals were collected and analyzed. In summer 2000, S. Newport and S. Enteritidis were isolated from 8.9% of southern giant petrels (Macronectes giganteus). In summer 2003, S. Enteritidis was isolated from 1.5% of Adelie penguins (Pygoscelis adeliae), from 5.5% of skuas (Stercorarius sp.), from 5.4% of kelp gulls (Larus dominicanus), and from 5.6% of Weddell seals (Leptonychotes weddelli). All the isolates belonging to the same serovar showed indistinguishable genomic profiles by Pulse-Field Gel Electrophoresis (PFGE) with XbaI and BlnI restriction enzymes and by Random Amplified Polymorphic DNA (RAPD-PCR). In addition, these Antarctic strains were different from S. enterica isolates from different sources identified in Argentina during the same or close time periods.Facultad de Ciencias Veterinaria

Laboratory-Based Prospective Surveillance for Community Outbreaks of Shigella spp. in Argentina

Background: To implement effective control measures, timely outbreak detection is essential. Shigella is the most common cause of bacterial diarrhea in Argentina. Highly resistant clones of Shigella have emerged, and outbreaks have been recognized in closed settings and in whole communities. We hereby report our experience with an evolving, integrated, laboratory-based, near real-time surveillance system operating in six contiguous provinces of Argentina during April 2009 to March 2012. Methodology To detect localized shigellosis outbreaks timely, we used the prospective space-time permutation scan statistic algorithm of SaTScan, embedded in WHONET software. Twenty three laboratories sent updated Shigella data on a weekly basis to the National Reference Laboratory. Cluster detection analysis was performed at several taxonomic levels: for all Shigella spp., for serotypes within species and for antimicrobial resistance phenotypes within species. Shigella isolates associated with statistically significant signals (clusters in time/space with recurrence interval ≥365 days) were subtyped by pulsed field gel electrophoresis (PFGE) using PulseNet protocols. Principal Findings In three years of active surveillance, our system detected 32 statistically significant events, 26 of them identified before hospital staff was aware of any unexpected increase in the number of Shigella isolates. Twenty-six signals were investigated by PFGE, which confirmed a close relationship among the isolates for 22 events (84.6%). Seven events were investigated epidemiologically, which revealed links among the patients. Seventeen events were found at the resistance profile level. The system detected events of public health importance: infrequent resistance profiles, long-lasting and/or re-emergent clusters and events important for their duration or size, which were reported to local public health authorities. Conclusions/Significance: The WHONET-SaTScan system may serve as a model for surveillance and can be applied to other pathogens, implemented by other networks, and scaled up to national and international levels for early detection and control of outbreaks

Salmonella enterica Subclinical Infection: Bacteriological, Serological, Pulsed-Field Gel Electrophoresis, and Antimicrobial Resistance Profiles-Longitudinal Study in a Three-Site Farrow-to-Finish Farm

Fil: Vigo, German B. Universidad Nacional de La Plata. Laboratorio de Diagnóstico e Investigaciones Bacteriológicas; Argentina.Fil: Cappuccio, J. A. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.Fil: Pineyro, Pablo E. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.Fil: Salve, Angela. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología; Argentina.Fil: Machuca, Mariana A. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.Fil: Quiroga, Maria A. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.Fil: Moredo, Fabiana. Universidad Nacional de La Plata. Laboratorio de Diagnóstico e Investigaciones Bacteriológicas; Argentina.Fil: Giacoboni, Gabriel. Universidad Nacional de La Plata. Laboratorio de Diagnóstico e Investigaciones Bacteriológicas; Argentina.Fil: Cancer, Jose L. Private practitioner; Argentina.Fil: Caffer, María Ines. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología; Argentina.Fil: Binsztein, Norma. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología; Argentina.Fil: Pichel, Mariana. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología; Argentina.Fil: Perfumo, Carlos J. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.The aim of this surveillance was to study both Salmonella spp. shedding patterns and the time course of serological response in farrow-to-finish reared pigs from a subclinically infected farm. Antimicrobial resistance profile, molecular subtyping, and the relationship among the isolates were determined by pulsed-field gel electrophoresis (PFGE). A farrow-to-finish farm of 6000 sows, with a history of Salmonella Typhimurium septicemia, was selected. A longitudinal bacteriological and serological study was conducted in 25 sows before farrowing (M=S1) and in 50 offspring at 21 (M=S2), 35 (M=S3), 65 (M=S4), 86 (M=S5), 128 (M=S6), and 165 (M=S7) days of age. Serum antibodies were tested using Herdcheck Swine Salmonella antibody test kit (Idexx Laboratories, ME). Bacteria were isolated from pooled fecal samples. Suspected isolates were confirmed by conventional biochemical assays, and those identified as Salmonella spp. were serotyped. A variation between seropositive percentages and positive fecal samples was observed. Serologically positive pigs decreased from S1 to S4, and subsequently increased from S4 to S7. The percentages of fecal positive culture increased from M1 to M3, and then declined in M4, increased in M5, and were negative in M6 and M7. In the study three serovars, Salmonella 3,10:e,h:-, Salmonella Muenster, and Salmonella Bovismorbificans, were identified with low pathogenicity for swine. Three multidrug resistance strains (one belonged to Salmonella 3,10:e,h:- and two belonged to Salmonella Muenster) were found. PFGE results showed three different but closely related patterns among the 13 isolates of Salmonella Bovismorbificans, and two patterns for the three Salmonella Muenster and Salmonella 3,10:e,h:- isolates. This longitudinal study established critical points of Salmonella spp. infection in the farm and the production stages, where appropriate control measures must be taken. PFGE showed clonal relationships in each serovar. Antibiotic resistance profiles should be periodically included due to public health concerns

Salmonella enterica Subclinical Infection: Bacteriological, Serological, Pulsed-Field Gel Electrophoresis, and Antimicrobial Resistance Profiles-Longitudinal Study in a Three-Site Farrow-to-Finish Farm

Fil: Vigo, German B. Universidad Nacional de La Plata. Laboratorio de Diagnóstico e Investigaciones Bacteriológicas; Argentina.Fil: Cappuccio, J. A. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.Fil: Pineyro, Pablo E. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.Fil: Salve, Angela. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología; Argentina.Fil: Machuca, Mariana A. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.Fil: Quiroga, Maria A. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.Fil: Moredo, Fabiana. Universidad Nacional de La Plata. Laboratorio de Diagnóstico e Investigaciones Bacteriológicas; Argentina.Fil: Giacoboni, Gabriel. Universidad Nacional de La Plata. Laboratorio de Diagnóstico e Investigaciones Bacteriológicas; Argentina.Fil: Cancer, Jose L. Private practitioner; Argentina.Fil: Caffer, María Ines. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología; Argentina.Fil: Binsztein, Norma. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología; Argentina.Fil: Pichel, Mariana. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología; Argentina.Fil: Perfumo, Carlos J. Universidad Nacional de La Plata. Cátedra de Patología Especial; Argentina.The aim of this surveillance was to study both Salmonella spp. shedding patterns and the time course of serological response in farrow-to-finish reared pigs from a subclinically infected farm. Antimicrobial resistance profile, molecular subtyping, and the relationship among the isolates were determined by pulsed-field gel electrophoresis (PFGE). A farrow-to-finish farm of 6000 sows, with a history of Salmonella Typhimurium septicemia, was selected. A longitudinal bacteriological and serological study was conducted in 25 sows before farrowing (M=S1) and in 50 offspring at 21 (M=S2), 35 (M=S3), 65 (M=S4), 86 (M=S5), 128 (M=S6), and 165 (M=S7) days of age. Serum antibodies were tested using Herdcheck Swine Salmonella antibody test kit (Idexx Laboratories, ME). Bacteria were isolated from pooled fecal samples. Suspected isolates were confirmed by conventional biochemical assays, and those identified as Salmonella spp. were serotyped. A variation between seropositive percentages and positive fecal samples was observed. Serologically positive pigs decreased from S1 to S4, and subsequently increased from S4 to S7. The percentages of fecal positive culture increased from M1 to M3, and then declined in M4, increased in M5, and were negative in M6 and M7. In the study three serovars, Salmonella 3,10:e,h:-, Salmonella Muenster, and Salmonella Bovismorbificans, were identified with low pathogenicity for swine. Three multidrug resistance strains (one belonged to Salmonella 3,10:e,h:- and two belonged to Salmonella Muenster) were found. PFGE results showed three different but closely related patterns among the 13 isolates of Salmonella Bovismorbificans, and two patterns for the three Salmonella Muenster and Salmonella 3,10:e,h:- isolates. This longitudinal study established critical points of Salmonella spp. infection in the farm and the production stages, where appropriate control measures must be taken. PFGE showed clonal relationships in each serovar. Antibiotic resistance profiles should be periodically included due to public health concerns

Diagnóstico de un brote de Salmonella Typhimurium en chinchillas (Chinchilla lanigera) mediante la electroforesis en gel de campo pulsado

Adult chinchillas (Chinchilla lanigera) that had suddenly died in a commercial farm located in La Plata City, Buenos Aires Province, Argentina, in July 2012 were macroscopically, histopathologically, and microbiologically examined. Salmonella enterica serovar Typhimurium (S. Typhimurium) was isolated from the liver, spleen, heart, lungs, kidneys and intestines from each of the five animals evaluated. The five strains were susceptible to ampicillin, cephalotin, cefotaxime, nalidixic acid, gentamicin, streptomycin, chloramphenicol, fosfomycin, nitrofurantoin and trimethoprimsulfamethoxazole, and resistant to tetracycline. Each of the five S. Typhimurium isolates was analyzed by XbaI-pulsed-field gel electrophoresis (PFGE), showing an identical electrophoretic profile with 15 defined bands, which was found to be identical to pattern ARJPXX01.0220 of the PulseNet Argentine National database of Salmonella PFGE patterns. This is the first work describing the postmortem diagnosis of an outbreak of salmonellosis in chinchillas by using molecular methods such as PFGE.Empleando estudios anatomopatológicos y microbiológicos se examinó a un grupo de chinchillas (Chinchilla lanigera) adultas que murieron súbitamente en 2012 en una granja de la ciudad de La Plata (Buenos Aires, Argentina). Se aisló Salmonella enterica serovar Typhimurium (S. Typhimurium) del hígado, el bazo, el corazón, los pulmones, los riñones y los intestinos de los cinco animales evaluados. Los cinco aislamientos estudiados (uno por animal) fueron sensibles a ampicilina, cefalotina, cefotaxima, ácido nalidíxico, gentamicina, estreptomicina, cloranfenicol, fosfomicina, nitrofurantoína y trimetoprima-sulfametoxazol, y resistentes a tetraciclina. El análisis de dichos aislamientos por electroforesis en gel de campo pulsado [pulsed-fi eld gel electrophoresis (PFGE)] con XbaI mostró un perÀ l electroforético idéntico con 15 bandas, idéntico a su vez al patrón ARJPXX01.0220 del banco nacional argentino de datos de PulseNet, que cuenta con patrones de PFGE de Salmonella. El presente trabajo describe por primera vez el diagnóstico postmortem de un brote de salmonelosis en chinchillas usando un método molecular, como la electroforesis en gel en campo pulsado.Facultad de Ciencias Veterinaria

Safety and effectiveness of RBD-specific polyclonal equine F(ab´)2 fragments for the treatment of hospitalized patients with severe Covid-19 disease: A retrospective cohort study

Background Passive immunotherapy has been evaluated as a therapeutic alternative for patients with COVID-19 disease. Equine polyclonal immunotherapy for COVID-19 (EPIC) showed adequate safety and potential efficacy in a clinical trial setting and obtained emergency use authorization in Argentina. We studied its utility in a real world setting with a larger population. Methods We conducted a retrospective cohort study at “Hospital de Campaña Escuela-Hogar" (HCEH) in Corrientes, Argentina, to assess safety and effectiveness of EPIC in hospitalized adults with severe COVID-19 pneumonia. Primary endpoints were 28-days all-cause mortality and safety. Mortality and improvement in modified WHO clinical scale at 14 and 21 days were secondary endpoints. Potential confounder adjustment was made by logistic regression weighted by the inverse of the probability of receiving the treatment (IPTW) and doubly robust approach. Findings Subsequent clinical records of 446 non-exposed (Controls) and 395 exposed (EPIC) patients admitted between November 2020 and April 2021 were analyzed. Median age was 58 years and 56.8% were males. Mortality at 28 days was 15.7% (EPIC) vs. 21.5% (Control). After IPTW adjustment the OR was 0.66 (95% CI: 0.46–0.96) P = 0.03. The effect was more evident in the subgroup who received two EPIC doses (complete treatment, n = 379), OR 0.58 (95% CI 0.39 to 0.85) P = 0.005. Overall and serious adverse events were not significantly different between groups. Conclusions In this retrospective cohort study, EPIC showed adequate safety and effectiveness in the treatment of hospitalized patients with severe SARS-CoV-2 disease.Fil: Farizano Salazar, Diego H.. Hospital de Campaña Escuela Hogar; ArgentinaFil: Achinelli, Fernando. Hospital de Campaña Escuela Hogar; ArgentinaFil: Colonna, Mariana. Inmunova; ArgentinaFil: Pérez, Lucía. Hospital Italiano; ArgentinaFil: Giménez, Analía A.. Hospital de Campaña Escuela Hogar; ArgentinaFil: Ojeda, Maria Alejandra. Hospital de Campaña Escuela Hogar; ArgentinaFil: Miranda Puente, Susana N.. Hospital de Campaña Escuela Hogar; ArgentinaFil: Sánchez Negrette, Lía. Hospital de Campaña Escuela Hogar; ArgentinaFil: Cañete, Florencia. Hospital de Campaña Escuela Hogar; ArgentinaFil: Martelotte Ibarra, Ornela I.. Hospital de Campaña Escuela Hogar; ArgentinaFil: Sanguineti, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Spatz, Linus. Inmunova; ArgentinaFil: Goldbaum, Fernando Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Massa, Carolina. Inmunova; ArgentinaFil: Rivas, Marta. Inmunova; ArgentinaFil: Pichel, Mariana. Inmunova; ArgentinaFil: Hiriart, Yanina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Estudios Inmunológicos y Fisiopatológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Estudios Inmunológicos y Fisiopatológicos; ArgentinaFil: Zylberman, Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gallego, Sandra Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; ArgentinaFil: Konigheim, Brenda Salome. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; ArgentinaFil: Fernández, Francisco. No especifíca;Fil: Deprati, Matías. No especifíca;Fil: Roubicek, Ian. Inmunova; ArgentinaFil: Giunta, Diego Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Hospital Italiano; ArgentinaFil: Nannini, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Inmunología Clinica y Experimental de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Instituto de Inmunología Clinica y Experimental de Rosario; ArgentinaFil: Lopardo, Gustavo. No especifíca;Fil: Belloso, Waldo Horacio. Hospital Italiano; Argentin

Standardization and international multicenter validation of a PulseNet pulsed-field gel electrophoresis protocol for subtyping Shigella flexneri isolates

Fil: Pichel, Mariana. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Brengi, Silvina P. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Cooper, Kara L. F. Centers for Disease Control and Prevention; Estados Unidos.Fil: Ribot, Efrain M. Centers for Disease Control and Prevention; Georgia.Fil: Al-Busaidy, Suleiman. Central Public Health Laboratory; Omán.Fil: Araya, Pamela. Instituto de Salud Pública de Chile; Chile.Fil: Fernández, Jorge. Instituto de Salud Pública de Chile; Chile.Fil: Vaz, Tania Ibelli. Instituto Adolfo Lutz; Brazil.Fil: Kam, Kai Man. Public Health Laboratory Centre; Japón.Fil: Morcos, Myriam. Regional Center at the U.S. Naval Medical Research Unit #3 (NAMRU-3). Global Disease Detection (GDD); Egipto.Fil: Nielsen, Eva M. Statens Serum Institut; Dinamarca.Fil: Nadon, Celine. National Microbiology Laboratory; Canadá.Fil: Pimentel, Guillermo. Regional Center at the U.S. Naval Medical Research Unit #3 (NAMRU-3). Global Disease Detection (GDD); Egipto.Fil: Pérez-Gutiérrez, Enrique. PAHO/WHO. Health Surveillance; Panamá.Fil: Gerner-Smidt, Peter. Centers for Disease Control and Prevention; Georgia.Fil: Binsztein, Norma. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Shigella flexneri is one of the agents most frequently linked to diarrheal illness in developing countries and often causes outbreaks in settings with poor hygiene or sanitary conditions. Travel is one of the means by which S. flexneri can be imported into developed countries, where this pathogen is not commonly seen. A robust and discriminatory subtyping method is needed for the surveillance of S. flexneri locally and regionally, and to aid in the detection and investigation of outbreaks. The PulseNet International network utilizes standardized pulsedfield gel electrophoresis (PFGE) protocols to carry out laboratory-based surveillance of foodborne pathogens in combination with epidemiologic data. A multicenter validation was carried out in nine PulseNet laboratories located in North and South America, Europe, and Asia, and it demonstrated that a new protocol is highly robust and reproducible for subtyping of S. flexneri. This protocol, already approved for PulseNet laboratories, applies NotI and XbaI as primary and secondary restriction enzymes, respectively, under electrophoresis conditions of initial switch time of 5 s to final switch time of 35 s, at 6 volts/cm

CS22, a Novel Human Enterotoxigenic Escherichia coli Adhesin, Is Related to CS15

Enterotoxigenic Escherichia coli (ETEC) expresses a broad spectrum of O:H antigens. Serogroup O20 is one of the most prevalent among the ETEC strains lacking any of the defined colonization factors (CFs), in Argentina. An O20:H− strain, ARG-3, adhered to Caco-2 cells and exhibited a thermoregulated 15.7-kDa protein band upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). An antiserum against this protein inhibited ARG-3 adhesion to Caco-2 cells and bound to very thin fibrilla-like structures on the bacterial surface. A 15.7-kDa protein-defective mutant failed to adhere to Caco-2 cells and lacked immunogold-labeled surface structures. The N-terminal amino acid sequence of the structural subunit showed 95% homology to that of CS15 of ETEC (former antigen 8786) and 65% homology with fimbria SEF14 of Salmonella enterica serovar Enteritidis. Nevertheless, the molecular size of ARG-3 adhesin was different from that of CS15, as revealed by SDS-PAGE and mass spectrometry. Both proteins are immunologically related, yet not identical, since an antiserum against the 15.7-kDa protein reacted solely with ARG-3 after absorption with bacteria bearing CS15. Moreover, only under low stringency conditions could DNA from strain ARG-3 be amplified by PCR using primers derived from the nfaA sequence of CS15. Thus, from the DNA sequence obtained from the ARG-3 PCR product, it could be deduced that the subunit protein differed in 30 residues from that of CS15. ARG-3 adhesin was found in 60% of the O20:H- CF-negative ETEC strains from Argentina; however, it appeared restricted to this serotype. We propose the designation CS22 for the herein identified nonfimbrial adhesin of human ETEC