Proactive therapeutic monitoring of dalbavancin concentrations in the long-term management of chronic osteoarticular/periprosthetic joint infections.

Here, we describe the use of proactive therapeutic drug monitoring (TDM) to individualize the optimal timing of drug injections in 16 adult patients with chronic osteoarticular infections receiving a median of 7 injections of dalbavancin (up to 12 injections in 15 months). Dalbavancin injections were repeated at medians of 39-47 days, with infusion intervals ranging from 26 to 69 days. TDM can facilitates a precise, targeted use of dalbavancin for infections requiring prolonged treatments.

Early administration of nirmatrelvir/ritonavir leads to faster negative SARS-CoV-2 nasal swabs than monoclonal antibodies in COVID 19 patients at high-risk for severe disease.

PURPOSE: Besides the well-established efficacy in preventing severe COVID-19, the impact of early treatments, namely antivirals and monoclonal antibodies (mAbs), on the time length to negativization of SARS-CoV-2 nasal swabs is still unclear. The aim of this study was to compare the efficacy of different early treatments in reducing the SARS-CoV-2 viral shedding, identifying a single drug that might potentially lead to a more rapid negativization of SARS-CoV-2 nasal swab. METHODS: This was a single-centre, retrospective, observational study conducted at Ospedale Luigi Sacco in Milan. Data of high-risk COVID-19 patients who received early treatments between 23 December 2021 and March 2023 were extracted. The comparison across treatments was conducted using the Kruskall-Wallis test for continuous variables. Dunn's test with Bonferroni adjustment was performed for post-hoc comparisons of days to negativization. Secondly, a negative binomial regression adjusted for age, sex, number of comorbidities, immunosuppression, and SARS-CoV-2 vaccination status was implemented. RESULTS: Data from 428 patients receiving early treatments were collected. The majority were treated with Nirmatrelvir/Ritonavir and were affected by SARS-CoV-2 Omicron infection with BA.2 sublineage. The median length time to SARS-CoV-2 nasal swab negativization was 9 days [IQR 7-13 days]. We found that Nirmatrelvir/Ritonavir determined a significant decrease of the length time to SARS-CoV-2 nasal swab negativization compared to mAbs (p = 0.003), but not compared to Remdesivir (p = 0.147) and Molnupiravir (p = 0.156). CONCLUSION: Our findings highlight the importance of promptly treating high-risk COVID-19 patients with Nirmatrelvir/Ritonavir, as it also contributes to achieving a faster time to negative SARS-CoV-2 nasal swabs.

Microbiological hazard identification in river waters used for recreational activities.

Pathogenic bacteria, viruses, and parasites can cause waterborne disease outbreaks. The study of coastal water quality contributes to identifying potential risks to human health and to improving water management practices. The Río de la Plata River, a wide estuary in South America, is used for recreational activities, as a water source for consumption and as a site for sewage discharges. In the present study, as the first step of a quantitative microbial risk assessment of the coastal water quality of this river, a descriptive study was performed to identify the microbial pathogens prevalent in its waters and in the sewage discharged into the river. Two sites, representing two different potential risk scenarios, were chosen: a heavily polluted beach and an apparently safe beach. Conductivity and fecal contamination indicators including enterococci, Escherichia coli, F + RNA bacteriophages, and human polyomaviruses showed high levels. Regarding enterococci, differences between sites were significant (p-values <0.001). 93.3% and 56.5% of the apparently safe beach exceeded the recreational water limits for E. coli and enterococci. Regarding pathogens, diarrheagenic E. coli, Salmonella, and noroviruses were detected with different frequencies between sites. The parasites Cryptosporidium spp. and Giardia duodenalis were frequently detected in both sites. The results regarding viral, bacterial, and parasitic pathogens, even without correlation with conventional indicators, showed the importance of monitoring a variety of microorganisms to determine water quality more reliably and accurately, and to facilitate further studies of health risk assessment. The taxonomic description of microbial pathogens in river waters allow identifying the microorganisms that infect the population living on its shores but also pathogens not previously reported by the clinical surveillance system.

Ryanodine receptor 1 (RYR1) mutations in two patients with tubular aggregate myopathy.

Two likely causative mutations in the RYR1 gene were identified in two patients with myopathy with tubular aggregates, but no evidence of cores or core-like pathology on muscle biopsy. These patients were clinically evaluated and underwent routine laboratory investigations, electrophysiologic tests, muscle biopsy and muscle magnetic resonance imaging (MRI). They reported stiffness of the muscles following sustained activity or cold exposure and had serum creatine kinase elevation. The identified RYR1 mutations (p.Thr2206Met or p.Gly2434Arg, in patient 1 and patient 2, respectively) were previously identified in individuals with malignant hyperthermia susceptibility and are reported as causative according to the European Malignant Hyperthermia Group rules. To our knowledge, these data represent the first identification of causative mutations in the RYR1 gene in patients with tubular aggregate myopathy and extend the spectrum of histological alterations caused by mutation in the RYR1 gene.

Molecular subtyping of Salmonella spp. strains in provincial abattoirs with no hazard analysis critical control point from Buenos Aires, Argentina.

We subtyped 32 Salmonella enterica strains isolated from carcasses (n=10), the environment (n=14), head meat (n=1) and viscera washing and chilling water (n=7) in provincial abattoirs with no Hazard Analysis Critical Control Point (HACCP) system from Buenos Aires, Argentina, before and after implementing improvement actions. Pulsed-field gel electrophoresis (PFGE) was carried out using the XbaI restriction enzyme. Strains belonged to six serovars, from which 10 restriction patterns were obtained (five unique patterns and five clusters). We found different clones of S. enterica serovars in the same abattoir by XbaI-PFGE. In addition to promoting good hygiene practices, the implementation of an HACCP plan is necessary to meet the zero-tolerance criteria for Salmonella on beef.

The Variable Expression of a Novel MBD5 Gene Frameshift Mutation in an Italian Family.

Haploinsufficiency of the methyl-CpG-binding domain protein 5 (MBD5) gene is reported as a cause of an autosomal dominant type of cognitive disability (MRD1) and autism spectrum disorder through large deletions involving multiple genes or point mutations, ultimately leading to haploinsufficiency in both cases. However, relatively few reports have been published on the phenotypical spectrum resulting from point mutations.We report here on a novel heterozygous frameshift variant in the MBD5 gene [c.2579del; p.(Lys860Argfs*11)] in a family in which the typical signs associated with pathogenic variants were expressed with different degrees of severity in the clinical presentation of the carrier individuals.Our findings, adding a novel mutation to the mutational spectrum, further support the relevance of the MBD5 gene as one of the main molecular mechanisms involved in the pathogenesis of intellectual disability and contribute to the characterization of the genotype-phenotype correlations.

Visual Cortex Engagement in Retinitis Pigmentosa.

Retinitis pigmentosa (RP) is a family of inherited disorders caused by the progressive degeneration of retinal photoreceptors. There is no cure for RP, but recent research advances have provided promising results from many clinical trials. All these therapeutic strategies are focused on preserving existing photoreceptors or substituting light-responsive elements. Vision recovery, however, strongly relies on the anatomical and functional integrity of the visual system beyond photoreceptors. Although the retinal structure and optic pathway are substantially preserved at least in early stages of RP, studies describing the visual cortex status are missing. Using a well-established mouse model of RP, we analyzed the response of visual cortical circuits to the progressive degeneration of photoreceptors. We demonstrated that the visual cortex goes through a transient and previously undescribed alteration in the local excitation/inhibition balance, with a net shift towards increased intracortical inhibition leading to improved filtering and decoding of corrupted visual inputs. These results suggest a compensatory action of the visual cortex that increases the range of residual visual sensitivity in RP.

Development and In-House Validation of a Real-Time Polymerase Chain Reaction for the Detection of Listeria monocytogenes in Meat.

Listeriosis is a foodborne disease caused by Listeria monocytogenes. The aims of this work were to develop and validate an in-house real-time polymerase chain reaction (RT-PCR) for the detection of L. monocytogenes, and to determine its prevalence in raw ground beef samples from 53 butcheries that also sell ready-to-eat foods. One set of primers and one hydrolysis probe were designed for hly gene detection and then challenged with pure strains. The detection was successful for all L. monocytogenes strains analyzed and negative for all non-L. monocytogenes strains (detection limit, 10 colony forming unit [CFU]/mL). Inclusivity, exclusivity, and analytical accuracy were 100%. L. monocytogenes was detected in 41.5% of raw ground beef samples from the 53 butcheries analyzed. This RT-PCR may be a valuable method for rapid detection of L. monocytogenes in meat.

[Detection and characterization of Shiga toxin-producing Escherichia coli in children treated at an inter-zonal pediatric hospital in the city of La Plata]. / Detección y caracterización de Escherichia coli productor de toxina Shiga en niños atendidos en un hospital pediátrico interzonal de la ciudad de La Plata.

Shiga toxin-producing Escherichia coli (STEC) is a foodborne pathogen that can cause watery diarrhea, bloody diarrhea (BD), and hemolytic uremic syndrome (HUS). The objective of this study was to determine the phenotypic and genotypic profiles of STEC strains isolated from children with BD and HUS treated at a pediatric hospital in the city of La Plata in the period 2006-2012, and to establish the clonal relationship of O157:H7 isolates by pulsed field electrophoresis. The percentage of positive samples was 4.9% and 39.2% in patients with BD and HUS, respectively. Seventy-seven STEC strains from 10 different serotypes were isolated, with 100% colony recovery, O157:H7 being the most frequent (71.4%) serotype, followed by O145:NM (15.6%). An average of 98.2% of O157:H7 isolates belonged to biotype C and were sensitive to all the antibiotics tested. All of them (100%) carried genotype stx2, eae, fliCH7, ehxA, iha, efa, toxB, lpfA1-3 and lpfA2-2. When the clonal relationship of the O157:H7 strains was studied, a total of 42 patterns with at least 88% similarity were identified, and 6 clusters with identical profiles were established. The eae-negative isolates belonged to serotypes O59:H19, O102:H6, O174:NM and O174:H21. The strains O59:H19 and O174:H21 were positive for the aggR gene. This study shows that STEC of different serotypes and genotypes circulate in the city of La Plata and surroundings. Despite the genetic diversity observed between the O157:H7 isolates, some were indistinguishable by the subtyping techniques used.

Identification and characterization of three novel mutations in the CASQ1 gene in four patients with tubular aggregate myopathy.

Here, we report the identification of three novel missense mutations in the calsequestrin-1 (CASQ1) gene in four patients with tubular aggregate myopathy. These CASQ1 mutations affect conserved amino acids in position 44 (p.(Asp44Asn)), 103 (p.(Gly103Asp)), and 385 (p.(Ile385Thr)). Functional studies, based on turbidity and dynamic light scattering measurements at increasing Ca2+ concentrations, showed a reduced Ca2+ -dependent aggregation for the CASQ1 protein containing p.Asp44Asn and p.Gly103Asp mutations and a slight increase in Ca2+ -dependent aggregation for the p.Ile385Thr. Accordingly, limited trypsin proteolysis assay showed that p.Asp44Asn and p.Gly103Asp were more susceptible to trypsin cleavage in the presence of Ca2+ in comparison with WT and p.Ile385Thr. Analysis of single muscle fibers of a patient carrying the p.Gly103Asp mutation showed a significant reduction in response to caffeine stimulation, compared with normal control fibers. Expression of CASQ1 mutations in eukaryotic cells revealed a reduced ability of all these CASQ1 mutants to store Ca2+ and a reduced inhibitory effect of p.Ile385Thr and p.Asp44Asn on store operated Ca2+ entry. These results widen the spectrum of skeletal muscle diseases associated with CASQ1 and indicate that these mutations affect properties critical for correct Ca2+ handling in skeletal muscle fibers.

Characterization and Molecular Subtyping of Shiga Toxin-Producing Escherichia coli Strains in Butcher Shops.

Shiga toxin-producing Escherichia coli (STEC) are important emerging foodborne human pathogens. Ruminants are the main animal reservoir of STEC currently known, and meat can become contaminated at different stages of the production chain. The aim of this work was to subtype and establish the epidemiological relatedness of non-O157 STEC strains isolated from ground beef and the environment in butcher shops before (evaluation stage, 2010-2011 period) and after (verification stage, 2013) implementing improvement actions. Sixty-eight non-O157 STEC strains were tested for eae, saa, ehxA, iha, efa1, toxB, subAB, cdt-V, astA, aggR, and aaiC genes, and stx1 and stx2 variants were determined. Pulsed-field gel electrophoresis (PFGE) was carried out with XbaI and XmaJI. From the 68 strains, 92.6%, 75.0%, 58.8%, 53.5%, 10.3%, 7.3%, and 4.4% were positive for iha, ehxA, subAB, saa, cdt-V, astA, and eae, respectively. All strains were aggR/aaiC-negative. PFGE showed that 19 strains grouped in 9 clusters and 41 showed unique XbaI patterns. During the evaluation stage (2010-2011), we identified clonal strains in different samples, circulating clones in different butcher shops, and more than one different strain in the same butcher shop. The bovine origin of meat and its manufacturing process could not ensure the total absence of all non-O157 STEC serotypes in this foodstuff. Most strains isolated during the evaluation (2010-2011) and verification (2013) stages did not exhibit a genotypic profile associated with human disease. It is necessary to conduct periodic reviews of the new epidemiological information and verify that the analyses of non-O157 STEC in food are appropriate to identify strains affecting the population.

Isolation of Shiga Toxin-Producing Escherichia coli from Ground Beef Using Multiple Combinations of Enrichment Broths and Selective Agars.

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens, and beef cattle are recognized as the principal reservoir. The aims of this study were (1) to identify the most sensitive combination of selective enrichment broths and agars for STEC isolation in artificially inoculated ground beef samples, and (2) to evaluate the most efficient combination(s) of methods for naturally contaminated ground beef samples. A total of 192 ground beef samples were artificially inoculated with STEC and non-stx bacterial strains. A combination of four enrichment broths and three agars were evaluated for sensitivity, specificity, and positive predictive value for STEC isolation from experimentally inoculated samples. Enrichments with either modified tryptic soy broth (mTSB) containing 8 mg/L novobiocin (mTSB-8) or modified Escherichia coli (mEC) broth followed by isolation in MacConkey agar were the most sensitive combinations for STEC isolation of artificially inoculated samples. Independently, both enrichments media followed by isolation in MacConkey were used to evaluate ground beef samples from 43 retail stores, yielding 65.1% and 58.1% stx-positive samples by RT-PCR, respectively. No difference was observed in the isolate proportions between these two methods (8/25 [32%] and 8/28 [28.6%]). Identical serotypes and stx genotypes were observed in STEC strains isolated from the same samples by either method. In this study, no single enrichment protocol was sufficient to detect all STEC in artificially inoculated samples and had considerable variation in detection ability with naturally contaminated samples. Moreover, none of the single or combinations of multiple isolation agars used were capable of identifying all STEC serogroups in either artificially inoculated or naturally occurring STEC-contaminated ground beef. Therefore, it may be prudent to conclude that there is no single method or combination of isolation methods capable of identifying all STEC serogroups.

Enterotoxigenic Escherichia coli Subclinical Infection in Pigs: Bacteriological and Genotypic Characterization and Antimicrobial Resistance Profiles.

Enterotoxigenic Escherichia coli (ETEC) is the major pathogen responsible for neonatal diarrhea, postweaning diarrhea, and edema disease in pigs. Although it can be harmless, ETEC is also present in the intestines of other animal species and humans, causing occasional diarrhea outbreaks. The evaluation of this pathogen's presence in food sources is becoming an increasingly important issue in human health. In order to determine the prevalence of ETEC in nondiarrheic pigs, 990 animals from 11 pig farms were sampled. Using end-time polymerase chain reaction (PCR), eltA, estI genes, or both, were detected in 150 (15.2%) animals. From the positive samples, 40 (26.6%) ETEC strains were isolated, showing 19 antibiotic-resistance patterns; 52.5% of these strains had multiple antibiotic resistances, and 17.5% carried the intI2 gene. The most prevalent genotypes were rfb(O157)/estII/aidA (32.5%) and estI/estII (25.0%). The estII gene was identified most frequently (97.5%), followed by estI (37.5%), astA (20.0%), and eltA (12.5%). The genes coding the fimbriae F5, F6, and F18 were detected in three single isolates. The aidA gene was detected in 20 ETEC strains associated with the estII gene. Among the isolated ETEC strains, stx(2e)/estI, stx(2e)/estI/estII, and stx(2e)/estI/estII/intI2 genotypes were identified. The ETEC belonged to 12 different serogroups; 37.5% of them belonged to serotype O157:H19. Isolates were grouped by enterobacterial repetitive intergenic consensus-PCR into 5 clusters with 100.0% similarity. In this study, we demonstrated that numerous ETEC genotypes cohabit and circulate in swine populations without clinical manifestation of neonatal diarrhea, postweaning diarrhea, or edema disease in different production stages. The information generated is important not only for diagnostic and epidemiological purposes, but also for understanding the dynamics and ecology of ETEC in pigs in different production stages that can be potentially transmitted to humans from food animals.

A mutation in the CASQ1 gene causes a vacuolar myopathy with accumulation of sarcoplasmic reticulum protein aggregates.

A missense mutation in the calsequestrin-1 gene (CASQ1) was found in a group of patients with a myopathy characterized by weakness, fatigue, and the presence of large vacuoles containing characteristic inclusions resulting from the aggregation of sarcoplasmic reticulum (SR) proteins. The mutation affects a conserved aspartic acid in position 244 (p.Asp244Gly) located in one of the high-affinity Ca(2+) -binding sites of CASQ1 and alters the kinetics of Ca(2+) release in muscle fibers. Expression of the mutated CASQ1 protein in COS-7 cells showed a markedly reduced ability in forming elongated polymers, whereas both in cultured myotubes and in in vivo mouse fibers induced the formation of electron-dense SR vacuoles containing aggregates of the mutant CASQ1 protein that resemble those observed in muscle biopsies of patients. Altogether, these results support the view that a single missense mutation in the CASQ1 gene causes the formation of abnormal SR vacuoles containing aggregates of CASQ1, and other SR proteins, results in altered Ca(2+) release in skeletal muscle fibers, and, hence, is responsible for the clinical phenotype observed in these patients.

Prevalence of Escherichia coli O157:H7 in surface water near cattle feedlots.

Between April 2009 and July 2011, 311 surface water samples in 48 cattle feedlots distributed in an area of about 67,000 km(2) were analyzed to examine the environmental dissemination of Escherichia coli O157:H7. Samples were taken inside and outside the pens, exposed and not exposed to runoff from corrals, near the feedlots. Two types of samples were defined: (1) exposed surface waters (ESW; n=251), downstream from cattle pens; and (2) nonexposed surface waters (NESW; n=60), upstream from cattle pens. By multiplex PCR, 177 (70.5%) ESW samples were rfb(O157)-positive, and 62 (24.7%) E. coli O157, and 32 (12.7%) Shiga toxin-producing E. coli (STEC) O157:H7 strains were isolated. In the NESW samples, 36 (60.0%) were rfb(O157)- positive, and 9 (15.0%) E. coli O157, and 6 (10.0%) STEC O157:H7 strains were isolated. These results showed that the environmental surface waters exposed to liquid discharges from intensive livestock operations tended to be contaminated with more STEC O157:H7 than NESW. However, no significant difference was found. This fact emphasizes the relevance of other horizontal routes of transmission, as the persistence of E. coli in the environment resulting from extensive livestock farming. By XbaI-PFGE, some patterns identified are included in the Argentine Database of E. coli O157, corresponding to strains isolated from hemolytic uremic syndrome and diarrhea cases, food, and animals, such as AREXHX01.0022, second prevalent pattern in Argentina, representing 5.5% of the total database. In the study area, characterized by the abundance of waterways, pathogens contained in feedlot runoff could reach recreational waters and also contaminate produce through irrigation, increasing the potential dissemination of STEC O157:H7 and the risk of human infections. The control of runoff systems from intensive livestock is necessary, but other alternatives should be explored to solve the problem of the presence of E. coli O157 in the aquatic rural environment.

Mortality of Patients With Candidemia and COVID-19: A Systematic Review With Meta-analysis.

Mortality of candidemia in coronavirus disease 2019 (COVID-19) patients has not been deeply studied despite evidence suggesting an increased occurrence. We performed a systematic review and meta-analysis to summarize the available evidence about these patients' mortality and length of stay. Data about the in-hospital, all-cause and 30-day mortality, and length of stay were pooled. Subgroup analyses were performed to assess sources of heterogeneity. Twenty-six articles out of the 1915 records retrieved during the search were included in this review. The pooled in-hospital mortality was 62.62% (95% CI, 54.77% to 69.86%), while the mortality in intensive care unit (ICU) was 66.77% (95% CI, 57.70% to 74.75%). The pooled median in-hospital length of stay was 30.41 (95% CI, 12.28 to 48.55) days, while the pooled median length of stay in the ICU was 28.28 (95% CI, 20.84 to 35.73) days. The subgroup analyses did not identify the sources of heterogeneity in any of the analyses. Our results showed high mortality in patients with candidemia and COVID-19, suggesting the need to consider screening measures to prevent this life-threatening condition.

Prioritization of vegetable-borne biological hazards in Argentina using a multicriteria decision analysis tool.

Vegetables, especially those eaten raw, have been implicated in several foodborne disease outbreaks. Since multiple vegetable matrices and hazards are involved, risk managers have to prioritize those with the greatest impact on public health to design control strategies. In this study, a scientific-based risk ranking of foodborne pathogens transmitted by leafy green vegetables in Argentina was performed. The prioritization process included hazard identification, evaluation criteria identification and definition, criteria weighting, expert survey design and selection and call for experts, hazard score calculation, hazard ranking and variation coefficient, and result analysis. Regression tree analysis determined four risk clusters: high (Cryptosporidum spp., Toxoplasma gondii, Norovirus), moderate (Giardia spp., Listeria spp., Shigella sonnei), low (Shiga toxin-producing Escherichia coli, Ascaris spp., Entamoeba histolytica, Salmonella spp., Rotavirus, Enterovirus) and very low (Campylobacter jejuni, hepatitis A virus and Yersinia pseudotuberculosis). Diseases caused by Norovirus, Cryptosporidium spp. and T. gondii do not require mandatory notification. Neither viruses nor parasites are included as microbiological criteria for foodstuff. The lack of outbreak studies did not allow to accurately identify vegetables as a source of Norovirus disease. Information on listeriosis cases or outbreaks due to vegetable consumption was not available. Shigella spp. was the main responsible for bacterial diarrhea, but it has not been epidemiologically associated with vegetable consumption. The quality of the available information for all hazards studied was very low and low. The implementation of good practice guidelines throughout the entire vegetable production chain could prevent the presence of the identified hazards. The current study allowed the identification of vacancy areas and could help reinforce the need for performing epidemiological studies on foodborne diseases potentially associated with vegetable consumption in Argentina.

Phylogenetically related Argentinean and Australian Escherichia coli O157 isolates are distinguished by virulence clades and alternative Shiga toxin 1 and 2 prophages.

Shiga toxigenic Escherichia coli O157 is the leading cause of hemolytic uremic syndrome (HUS) worldwide. The frequencies of stx genotypes and the incidences of O157-related illness and HUS vary significantly between Argentina and Australia. Locus-specific polymorphism analysis revealed that lineage I/II (LI/II) E. coli O157 isolates were most prevalent in Argentina (90%) and Australia (88%). Argentinean LI/II isolates were shown to belong to clades 4 (28%) and 8 (72%), while Australian LI/II isolates were identified as clades 6 (15%), 7 (83%), and 8 (2%). Clade 8 was significantly associated with Shiga toxin bacteriophage insertion (SBI) type stx(2) (locus of insertion, argW) in Argentinean isolates (P < 0.0001). In Argentinean LI/II strains, stx(2) is carried by a prophage inserted at argW, whereas in Australian LI/II strains the argW locus is occupied by the novel stx(1) prophage. In both Argentinean and Australian LI/II strains, stx(2c) is almost exclusively carried by a prophage inserted at sbcB. However, alternative q(933)- or q(21)-related alleles were identified in the Australian stx(2c) prophage. Argentinean LI/II isolates were also distinguished from Australian isolates by the presence of the putative virulence determinant ECSP_3286 and the predominance of motile O157:H7 strains. Characteristics common to both Argentinean and Australian LI/II O157 strains included the presence of putative virulence determinants (ECSP_3620, ECSP_0242, ECSP_2687, ECSP_2870, and ECSP_2872) and the predominance of the tir255T allele. These data support further understanding of O157 phylogeny and may foster greater insight into the differential virulence of O157 lineages.

Non-O157:H7 Shiga toxin-producing Escherichia coli in bovine rectums and surface water streams on a beef cattle farm in Argentina.

The purposes of this study were to detect non-O157 Shiga toxin-producing Escherichia coli (STEC) in bovine rectums and water in a beef cattle farm in Argentina, and to determine the pathogenic potential of the circulating strains. During the study, 292 rectal swabs from healthy animals and 79 environmental water samples were collected. The rectal swabs and one loop of the Moore swabs, enriched in Escherichia coli broth for 24 h at 37°C, were streaked on MacConkey agar plates and incubated overnight at 37°C. The isolates were characterized by biochemical tests and serotyped. Nonmotile STEC strains were typed for their H-specific (fliC) antigens by polymerase chain reaction (PCR). Isolates were characterized by detection of stx1, stx2, and their variants, eae, ehxA, and saa genes. Macrorestriction fragment analysis by pulsed-field gel electrophoresis (PFGE) was performed using the PulseNet standardized protocol. From 371 samples analyzed, 36.6% of rectal swabs and 34.2% of water samples were non-O157 STEC-positive by PCR, and 110 strains from rectal swabs, but only three from water, were isolated. The strains were grouped into 24 different serotypes, from which, O103:[H2] (n = 12), O136:H12 (n = 8), O178:H19 (n = 8), and O103:NM (n = 5) were most prevalent, representing 29.2% of the isolates. Predominant genotypes were stx1/eae/ehxA (16.8%) and stx2/saa/ehxA (15.9%). PFGE analysis revealed 56 different patterns, with 65 strains grouped in 19 clusters of 100% similarity. Two STEC O124:H19 strains isolated from rectal swabs and water with a 5-month interval harbored the stx1/stx2/saa/ehxA genotype, and showed an indistinguishable PFGE profile. By comparison, some XbaI-PFGE patterns identified in the present study were identical to the profiles of strains isolated from human, food, and animal sources included in the Argentine PulseNet database. By PCR, similar non-O157 detection rates were found in rectal swabs and water. However, the methodology for water samples needs to be improved, since only three strains from the total number of positive samples were recovered.

Reduction of Shiga toxin-producing Escherichia coli in a beef abattoir.

The aim of this work was to reinforce actions tending to reduce Shiga toxin-producing Escherichia coli (STEC) in beef products from an Argentinean commercial abattoir implementing Hazard Analysis and Critical Control Point (HACCP) practices. An environmental stx map was built with 421 environmental samples from the slaughter, quartering, cool chamber and deboning sectors (February-May 2013). For stx determination, 125 carcass and 572 anatomical cut samples were used. Based on the environmental stx mapping results, improvement actions were designed and implemented (June and July 2013). After implementing improvement actions, 160 carcass and 477 anatomical cut samples were collected to identify stx and verify the impact of improvement actions (August-December 2013). Our results showed stx-positivity in pre-operational (10.1%) and operational (15.5%) environmental samples and in carcass and beef cut samples before (4.8 and 10.1%; p = 0.144) and after (1.2 and 4.8%; p = 0.0448) implementing improvement actions, respectively. Although improvement actions reduced stx in beef cuts, it is difficult to implement and sustain a system based on stx zero-tolerance only by reinforcing Good Manufacturing Practices, Sanitation Standard Operating Procedures and HACCP practices. The application of combined intervention strategies to reduce STEC in carcasses and beef cuts should be therefore considered.