Detection of EPEC and STEC strains isolated from children with diarrhea in Argentina.

Rectal swabs (122) from pediatric patients were analyzed by polymerase chain reaction (PCR) for the detection of EPEC and STEC. STEC isolates were tested for the presence of stx1, stx2, eae, saa and ehxA. All eae-positive samples were tested for the presence of bfpA, and antigen O was determined using the agglutination test. Int1 and Int2 were detected to identify the presence of integrons class 1 and 2, respectively. Escherichia coli was detected in 68% of the samples, of which 18.8% were STEC (2.45%) and EPEC (16.3%). Serogroups STEC O145 and EPEC O130, O113 and O157 were observed, while three strains were non-typable. None of the EPEC strains carrying tbfpA and class 1 and 2 integrons was detected in any of the samples. The results obtained are important considering the virulence profiles found in the isolated EPEC and STEC strains and the serogroups associated with disease in humans.

Antinematodic effect of Enterococcus faecalis CECT7121 using Trichinella spiralis as a model of nematode infection in mice.

Nematode infections affect a significant percentage of the human population worldwide, especially in developing countries. There are a small number of drugs available to treat these infections, with variable outcomes. Therefore, the potential use of probiotics to help control parasitic infections has emerged as a suitable option. The main goal of this work was to assess the antinematodic effect of the probiotic Enterococcus faecalis CECT7121 (EFCECT7121) in vitro and in vivo, using Trichinella spiralis as a nematode model of infection. The in vitro assay showed a reduction in T. spiralis larvae viability of 31.6% when compared with the control group (6.3%) after 48 h incubation with EFCECT7121. Nevertheless, the isolated antimicrobial peptide AP7121 when inoculated at different concentrations did not reveal any larvicidal effect. Different EFCECT7121 treatment schemes in mice were evaluated, and the reduction of the enteral and parenteral burden of T. spiralis was determined. In addition, the protective effect of EFCECT7121 combined with the conventional anthelmintic albendazole (ABZ, 5 mg/kg) was also assessed. The oral administration of EFCECT7121 previous T. spiralis infection produced a reduction in the larvae per gram (LPG) of mice muscle tissue ranging from 32.8 to 47.9% on the 28th day post-infection. ABZ alone and the combination EFCECT7121 + ABZ produced a reduction of the LPG of muscle tissue of 62 and 60.7%, respectively. Results obtained in the current work support the hypothesis that probiotics such as EFCECT7121 have an antinematodic effect, and their combination with conventional anthelmintic drugs may result useful for improving clinical and parasitological outcomes.

In vitro activity of the antimicrobial peptide AP7121 against the human methicillin-resistant biofilm producers Staphylococcus aureus and Staphylococcus epidermidis.

In vitro activity against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis biofilm producers from blood cultures of patients with prosthetic hip infections was evaluated. The Minimum Inhibitory Concentration (MIC) for AP7121 was determined and the bactericidal activity of AP7121 (MICx1, MICx4) against planktonic cells was studied at 4, 8 and 24 h. The biofilms formed were incubated with AP7121 (MICx1, MICx4) for 1 and 24 h. The anti-adhesion effect of an AP7121-treated inert surface over the highest MIC isolate was studied with scanning electron microscopy (SEM). The bactericidal activity of AP7121 against all the planktonic staphylococcal cells was observed at 4 h at both peptide concentrations. Dose-dependent anti-biofilm activity was detected. AP7121 (MICx4) showed bactericidal activity at 24 h in all isolates. SEM confirmed prevention of biofilm formation. This research showed the in vitro anti-biofilm activity of AP7121 against MRSA and S. epidermidis and the prevention of biofilm formation by them on an abiotic surface.

Detection of ß-Lactamase-Producing Enterococcus faecalis and Vancomycin-Resistant Enterococcus faecium Isolates in Human Invasive Infections in the Public Hospital of Tandil, Argentina.

The study's aim was to analyze the population structure of enterococci causing human invasive infections in a medium-sized Argentinian Hospital coincidental with a 5 year-period of increased recovery of antibiotic resistant enterococci (2010-2014). Species identification (biochemical testing/MALDI-TOF-MS), antimicrobial susceptibility (disk-diffusion) and clonal relatedness (PFGE/MLST/BAPS) were determined according to standard guidelines. ß-lactamase production was determined by a nitrocefin test and confirmed by PCR/sequencing. The isolates were identified as Enterococcus faecalis and Enterococcus faecium at a 2:1 ratio. Most of the E. faecalis isolates, grouped in 25 PFGE-types (ST9/ST179/ST236/ST281/ST388/ST604/ST720), were resistant to high-levels (HLR) of gentamicin/streptomycin. A ST9 clone (bla+/HLR-gentamicin) was detected in patients of different wards during 2014. E. faecium isolates were grouped in 10 PFGE-types (ST25/ST18/ST19/ST52/ST792), with a low rate of ampicillin resistance. Five vancomycin-resistant E. faecium, three vanA (ST792/ST25) and two vanB (ST25) were detected. The ST25 clone carried either vanA or vanB. The recovery of a bla+-ST9-E. faecalis clone similar to that described in the late 1980s in Argentina suggests the possibility of a local hidden reservoir. These results reflect the relevance of local epidemiology in understanding the population structure of enterococci as well as the emergence and spread of antimicrobial resistance in predominant enterococcal clonal lineages.

Bactericidal Activity and Synergy Studies of Peptide AP-CECT7121 Against Multi-resistant Bacteria Isolated from Human and Animal Soft Tissue Infections.

AP-CECT7121 is an antimicrobial peptide, produced by Enterococcus faecalis CECT7121, with bactericidal activity against Gram-positive bacteria. The aim of this study was to evaluate the bactericidal activity of AP-CECT7121, alone and with gentamicin, against multi-resistant bacteria isolated from human and animals with soft tissue infections. During the period 2014-2015, bacterial strains producing human and animal soft tissue infections were studied. Samples from patients attended at a general hospital and cattle from four dairies in the Province of Buenos Aires (Argentina) were included. Twenty-two methicillin-resistant Staphylococcus aureus (11, human blood samples; 11, cow milk) and five vancomycin-resistant Ent. faecium strains isolated from four mastitic dairy cows were tested. AP-CECT7121 (12 mg/L) potency was assessed by time-kill curves alone or with sub-inhibitory concentrations of gentamicin. All staphylococcal strains were susceptible to gentamicin; enterococci did not show high-level gentamicin resistance. Colony counts were carried out at 0, 2, 4, 8, and 24 h of incubation. AP-CECT7121 showed bactericidal activity against all the enterococcal strains. In addition, AP-CECT7121 had a bactericidal effect on most staphylococci (16/22). Early AP-CECT7121/gentamicin synergy (4-8 h) for all staphylococci was detected. At 24 h, synergy (19/22) and indifference (3/22) were observed. Synergy with gentamicin was detected for staphylococci. AP-CECT7121 constitutes an attractive candidate for its use as a natural therapeutic tool for the treatment of infections produced by multi-resistant Staph. aureus and vancomycin-resistant Ent. faecium isolated from humans and animals.

Throat Carriage Rate and Antimicrobial Resistance of Streptococcus pyogenes In Rural Children in Argentina.

OBJECTIVES: The aim of this study was to determine the prevalence of asymptomatic carriers of group A ß-hemolytic streptococci (GAS) in children living in a rural community and to investigate the association between episodes of acute pharyngitis and carrier status. METHODS: Throat swabs were collected from September to November 2013 among children 5-13 years of age from a rural community (Maria Ignacia-Vela, Argentina). The phenotypic characterization of isolates was performed by conventional tests. Antimicrobial susceptibility was assayed for penicillin, tetracycline, chloramphenicol, erythromycin, and clindamycin (disk diffusion). The minimum inhibitory concentration was determined for penicillin, cefotaxime, tetracycline, and erythromycin. RESULTS: The carriage of ß-hemolytic streptococci was detected in 18.1% of participants, with Streptococcus pyogenes in 18 participants followed by S. dysgalactiae ssp. equisimilis in 5. The highest proportion of GAS was found in 8 to 10-year-old children. No significant association between the number of episodes of acute pharyngitis suffered in the last year and the carrier state was detected (p>0.05). Tetracycline resistance (55.5%) and macrolide-resistant phenotypes (11.1%) were observed. Resistance to penicillin, cefotaxime, or chloramphenicol was not expressed in any streptococcal isolate. CONCLUSIONS: The present study demonstrated significant throat carriage of GAS and the presence of group C streptococci (S. dysgalactiae ssp. equisimilis) in an Argentinian rural population. These results point out the need for continuous surveillance of GAS and non-GAS carriage as well as of antimicrobial resistance in highly susceptible populations, such as school-aged rural children. An extended surveillance program including school-aged children from different cities should be considered to estimate the prevalence of GAS carriage in Argentina.

Bacteriemia por Staphylococcus aureus con sensibilidad disminuida heterogénea a vancomicina: reporte de un caso / Staphylococcus aureus bacteremia with heterogeneous intermediate-level vancomycin resistance: a case report

Staphylococcus aureusmeticilina-resistente (SAMR)es una causa frecuente de bacteriemias intrahospitalarias. Para su tratamiento se utiliza vancomicina y han emergido cepas con sensibilidad disminuida heterogénea (h-VISA) que albergan subpoblaciones con sensibi-lidad reducida a vancomicina. Se comunica un caso de bacteriemia intra-tratamiento con vancomicina por SAMR h-VISA. El aislamiento muestra sensibilidad a vancomicina (CIMvan: 1 µg/mL), sin embargo E-test GRD sugiere h-VISA (CIMvan: 2 µg/mL y CIMtei: 8 µg/mL). El análisis del perfil poblacional - área bajo la curva (PAP-AUC) valida este hallazgo. Se rota a linezolid con resolución clínica.

Methicillin-resistant Staphylococcus aureus (SAMR) is a common cause of nosocomial bacteremia. Vancomycin, a glycopeptide, is widely employed for the therapy of SAMR infections. In recent years, heterogeneous vancomycin-intermediate strains (h-VISA) have emerged. We report a case of intra-treatment bacteremia caused by SAMR h-VISA. The isolate shows susceptibility to vancomycin (MICvan: 1 µg/mL). But the GRD E-test suggests h-VISA (MICvan: 2 µg/mL and MICtei: 8 µg/mL). The population analysis profile - area under the curve (PAP-AUC) validates SAMR h-VISA. Rotation of antibiotic therapy with linezolid is done, with good clinical outcome.

Caracterización fenotípica de variantes pequeñas de Staphylococcus aureus: un nuevo desafío / Phenotypic characterization of small colony variants of Staphylococcus aureus: a new challenge / Caracterizaçao fenotípica de pequenas variantes de Staphylococcus aureus: um novo desafio

En infecciones crónicas y recurrentes por Staphylococcus aureus se han descripto subpoblaciones de colonias pequeñas (VCPSa). El objetivo de este trabajo fue reconocer las características fenotípicas de VCPSa para optimizar su detección y caracterización a partir de materiales clínicos provenientes de infecciones crónicas. Se analizaron n=3 VCPSa de pacientes adultos con infecciones crónicas de tejidos blandos. Las muestras se inocularon en agar nutritivo, agar sangre, agar chocolate y agar Schaedler suplementado. Se realizaron tinción de Gram, catalasa, coagulasa libre, pruebas de dependencia para hemina, menadiona y timidina y, desarrollo/ataque del manitol en agar manitol salado. La sensibilidad antibiótica se efectuó en agar Mueller Hinton suplementado, según las pruebas de dependencia. Se investigó la presencia de proteína ligadora de penicilina anómala (PBP2´) por aglutinación con látex. Las VCPSa se detectaron en los medios de cultivo enriquecidos. Estas bacterias dieron positivas las pruebas de catalasa y coagulasa, y eran dependientes de menadiona y hemina. En los tres aislamientos se observó resistencia a cefoxitina y se detectó la PBP2´.

In chronic and recurrent infections, small colonies of Staphylococcus aureus subpopulations (SCVSa) have been observed. The objective of the present study was to recognize the phenotypic characteristics of SCVSa isolated from patients with chronic infections to optimize their detection. SCVSa of adult patients n=3 with chronic soft tissue infections were analyzed. Samples were inoculated on nutritive agar, blood-agar, chocolate agar and supplemented Schaedler agar. Subsequently, Gram stain, catalase, free coagulase, dependence tests for hemin, menadione and thymidine, and growth/fermentation of mannitol on salt mannitol agar were performed. Antibiotic susceptibility tests were performed by the agar diffusion method on supplemented Mueller Hinton agar, according to dependence assays results. Anomalous penicillin binding protein (PBP2') was investigated by latex agglutination. SCVSa were detected in all enriched culture media. They showed catalase and coagulase activities, and menadione and hemin dependence. By the agar diffusion test, cefoxitin resistance was found in all isolates; PBP2' was detected as well.

Nas infecções crônicas e recorrentes por Staphylococcus aureus, subpopulações de pequenas colônias (VCPSa) foram descritas. O objetivo desse trabalho foi reconhecer as características fenotípicas de VCPSa para otimizar sua detecção e caracterização a partir de materiais clínicos provenientes de infecções crônicas. Foram analisados n=3 VCPSa de pacientes adultos com infecções crônicas de tecidos moles. As amostras foram inoculadas em agar nutritivo, agar sangue; agar chocolate e agar Schaedler enriquecido. Foram realizados testes de coloração de Gram, catalase, coagulase livre, testes de dependência para hemina, menadiona e timidina, e desenvolvimento/fermentação do manitol em agar manitol salgado. A sensibilidade antibiótica foi realizada em agar Mueller Hinton suplementado, de acordo com os testes de dependência. Foi investigada a presença de proteína ligante de penicilina anômala (PBP2´) por aglutinação com látex. Os VCPSa foram detectados em meios de cultura enriquecidos. Estas bactérias deram positivas nos testes de catalase e coagulase positivos e eram dependentes de menadiona e hemina. A resistência à cefoxitina foi detectada nos três isolados e detectou-se a PBP2'.