Forces required to dynamize sliding screws in gamma nail and selfdynamizable internal fixator.

BACKGROUND: Single limb support phase of the gait-cycle in patients who are treated for a pertrochanteric fracture is characterized by transversal loads acting on the lag screw, tending to block its dynamization. If the simultaneous axial force overcomes transversal loads of the sliding screw, the dynamization can still occur. METHODS: Biomechanical investigation was performed for three types of dynamic implants: Gamma Nail, and two types of Selfdynamizable Internal Fixators (SIF) - SIF-7 (containing two 7 mm non-cannulated sliding screws), and SIF-10 (containing one 10 mm cannulated sliding screw). Contact surface between the stem and the sliding screws is larger in SIF implants than in Gamma Nail, as the stem of Gamma Nail is hollow. A special testing device was designed for this study to provide simultaneous application of a controlled sliding screws bending moment and a controlled transversal load on sliding screws (Qt) without using of weights. Using each of the implants, axial forces required to initiate sliding screws dynamization (Qa) were applied and measured using a tensile testing machine, for several values of sliding screws bending moment. Standard least-squares method was used to present the results through the linear regression model. RESULTS: Positive correlation between Qt and Qa was confirmed (p < 0.05). While performing higher bending moments in all the tested implants, Qa was higher than it could be provided by the body weight. It was the highest in Gamma Nail, and the lowest in SIF-10. CONCLUSIONS: A larger contact surface between a sliding screw and stem results in lower forces required to initiate dynamization of a sliding screw. Patients treated for a pertrochanteric fracture by a sliding screw internal fixation who have longer femoral neck or higher body weight could have different programme of early postoperative rehabilitation than lighter patients or patients with shorter femoral neck.

Does the Internet Provide Quality Information on Metoidioplasty? Using the Modified Ensuring Quality Information for Patients Tool to Evaluate Artificial Intelligence-Generated and Online Information on Metoidioplasty.

BACKGROUND: Public interest in gender affirmation surgery has surged over the last decade. This spike in interest, combined with extensive free online medical knowledge, has led many to the Internet for more information on this complicated procedure. This study aimed to evaluate the quality of online information on metoidioplasty. METHODS: Google Trends in searches on "metoidioplasty" from 2004 to present were assessed. "metoidioplasty" was searched on three popular search engines (Google, Yahoo, and Bing), and the first 100 websites from each search were extracted for inclusion (Fig. 1). Exclusion criteria included duplicates, websites requiring fees, photo libraries, and irrelevant websites. Websites were assigned a score (out of 36) using the modified Ensuring Quality Information for Patients (EQIP) instrument, which grades patient materials based on content (18), identification (6), and structure (12). ChatGPT was also queried for metoidioplasty-related information and responses were analyzed using EQIP. RESULTS: Google Trends analysis indicated relative search interest in "metoidioplasty" has more than quadrupled since 2013(Fig. 2). Of the 93 websites included, only 2 received an EQIP score greater than 27 (6%). Website scores ranged from 7 to 33, with a mean of 18.6 ± 4.8. Mean scores were highest for websites made by health departments (22.3) and lowest for those made by encyclopedias and academic institutions (16.0). Websites with the highest frequency were research articles, web portals, hospital websites, and private practice sites, which averaged scores of 18.2, 19.7, 19.0, and 17.8, respectively. Health department sites averaged the highest content points (11.25), and academic institutions averaged the lowest (5.5). The average content point across all websites was 7.9 of 18. ChatGPT scored a total score of 29: 17 content, 2 identification, and 10 structures. The artificial intelligence chatbot scored the second highest score among all included online resources. CONCLUSIONS: Despite the continued use of search engines, the quality of online information on metoidioplasty remains exceptionally poor across most website developers. This study demonstrates the need to improve these resources, especially as interest in gender-affirming surgery continues to grow. ChatGPT and other artificial intelligence chatbots may be efficient and reliable alternatives for those seeking to understand complex medical information.

Applying machine learning in the investigation of the link between the high-velocity streams of charged solar particles and precipitation-induced floods.

This study explores a possible link between solar activity and floods caused by precipitation. For this purpose, discrete blocks of data for 89 separate flood events in Europe in the period 2009-2018 were used. Solar activity parameters with a time lag of 0-11 days were used as input data of the model, while precipitation data in the 12 days preceding the flood were used as output data. The level of randomness of the input and output time series was determined by correlation analysis, while the potential causal relationship was established by applying machine learning classification predictive modeling. A total of 25 distinct machine-learning algorithms and four model ensembles were applied. It was shown that in 81% of cases, the designed model could explain the occurrence or absence of precipitation-induced floods 9 days in advance. Differential proton flux in the 0.068-0.115 MeV and integral proton flux > 2.5 MeV were found to be the most important factors for forecasting precipitation-induced floods. The study confirmed that machine learning is a valuable technique for establishing nonlinear relationships between solar activity parameters and the onset of floods induced by precipitation.

Investigation of the OAM EM wave tissue irradiation at millimeter-wave frequencies.

Recently, there has been an increase of interest in the use of electromagnetic (EM) waves with helical wavefronts, known as the orbital angular momentum (OAM) waves. Applications in the field of biomedicine have been foreseen, such as medical imaging and diagnosis, deep-tissue imaging, biosensing, and communication with medical implants. Other possible applications include various localized tissue treatments or tissue ablation. The available references mainly study the interaction of OAM light with biological structures, offering some insights into the biophotonics effects, but without the investigation of how to plan tissue exposures or how to estimate the EM field parameters in a particular case of application. We use the previously developed short dipole modeling of OAM EM fields to study the above problems by altering the OAM beam parameters and the distance from the target tissue. The results could guide the design of components and devices based on OAM EM waves.

The Human Soluble NKG2D Ligand Differentially Impacts Tumorigenicity and Progression in Temporal and Model-Dependent Modes.

NKG2D is an activating receptor expressed by all human NK cells and CD8 T cells. Harnessing the NKG2D/NKG2D ligand axis has emerged as a viable avenue for cancer immunotherapy. However, there is a long-standing controversy over whether soluble NKG2D ligands are immunosuppressive or immunostimulatory, originating from conflicting data generated from different scopes of pre-clinical investigations. Using multiple pre-clinical tumor models, we demonstrated that the impact of the most characterized human solid tumor-associated soluble NKG2D ligand, the soluble MHC I chain-related molecule (sMIC), on tumorigenesis depended on the tumor model being studied and whether the tumor cells possessed stemness-like properties. We demonstrated that the potential of tumor formation or establishment depended upon tumor cell stem-like properties irrespective of tumor cells secreting the soluble NKG2D ligand sMIC. Specifically, tumor formation was delayed or failed if sMIC-expressing tumor cells expressed low stem-cell markers; tumor formation was rapid if sMIC-expressing tumor cells expressed high stem-like cell markers. However, once tumors were formed, overexpression of sMIC unequivocally suppressed tumoral NK and CD8 T cell immunity and facilitated tumor growth. Our study distinguished the differential impacts of soluble NKG2D ligands in tumor formation and tumor progression, cleared the outstanding controversy over soluble NKG2D ligands in modulating tumor immunity, and re-enforced the viability of targeting soluble NKG2D ligands for cancer immunotherapy for established tumors.

A ligand discovery toolbox for the WWE domain family of human E3 ligases.

The WWE domain is a relatively under-researched domain found in twelve human proteins and characterized by a conserved tryptophan-tryptophan-glutamate (WWE) sequence motif. Six of these WWE domain-containing proteins also contain domains with E3 ubiquitin ligase activity. The general recognition of poly-ADP-ribosylated substrates by WWE domains suggests a potential avenue for development of Proteolysis-Targeting Chimeras (PROTACs). Here, we present novel crystal structures of the HUWE1, TRIP12, and DTX1 WWE domains in complex with PAR building blocks and their analogs, thus enabling a comprehensive analysis of the PAR binding site structural diversity. Furthermore, we introduce a versatile toolbox of biophysical and biochemical assays for the discovery and characterization of novel WWE domain binders, including fluorescence polarization-based PAR binding and displacement assays, 15N-NMR-based binding affinity assays and 19F-NMR-based competition assays. Through these assays, we have characterized the binding of monomeric iso-ADP-ribose (iso-ADPr) and its nucleotide analogs with the aforementioned WWE proteins. Finally, we have utilized the assay toolbox to screen a small molecule fragment library leading to the successful discovery of novel ligands targeting the HUWE1 WWE domain.

Comunicación interpersonal e incidencia del burnout en la interacción entre sanitarios y pacientes / No disponible

Se analiza la calidad de la atención y comunicación al paciente, teniendo en cuenta las características personales intrínsecas de los profesionales sanitarios (en este caso el burnout) que puedan incidir y afectar esta relación. La muestra está compuesta por 760 sanitarios divididos en tres perfiles: médicos, enfermeros y auxiliares técnicos. La propuesta metodológica de este trabajo se desarrolla en el contexto del Servicio Extremeño de Salud. Los resultados manifiestan que los sanitarios no perciben dificultades en la calidad de la atención y la comunicación con el paciente, destacando que su principal habilidad radica en la empatía que muestran hacia el usuario (se perciben cercanos, comprensivos, amistosos…). Lo mismo que en la adecuada calidad de la atención y comunicación con el paciente. En cuanto al burnout, los profesionales consideran que no manifiestan cansancio emocional y despersonalización en su puesto de trabajo; además, se sienten muy realizados en su labor profesional

The research analyzes the quality of care and communication with patients, taking into account the inherent personal characteristics of health professionals (in this case the burnout) that may influence and affect this relationship. The sample consists of 760 health divided into three sections: doctors, nurses and technical assistants. The proposed methodology of this work takes place in the context of the Extremadura Health Service. The results show that health problems do not receive the quality of care and patient communication, emphasizing that his main skill lies in showing empathy towards the user (perceived close, supportive, friendly ...). As in the right quality of care and patient communication. As for the burnout, practitioners believe that no manifest emotional exhaustion and depersonalization in the workplace; also they feel very fulfilled in their work

Botulismo del lactante. / Infant botulism

El botulismo del lactante es una toxiinfeccion producida por la germinacion y toxinogenesis de Clostridium botulinum en el intestino. La presente exposicion es una revisor de la literatura general publicada desde que se reconocio esta entidad a partir de 1976, incluyendo ademas el aporte de una investigacion realizada por los autores. Se decriben formas clinicas, epidemiologia y finalmente se hace referencia a diagnostico y tratamiento

Botulismo del lactante. / Infant botulism

El botulismo del lactante es una toxiinfeccion producida por la germinacion y toxinogenesis de Clostridium botulinum en el intestino. La presente exposicion es una revisor de la literatura general publicada desde que se reconocio esta entidad a partir de 1976, incluyendo ademas el aporte de una investigacion realizada por los autores. Se decriben formas clinicas, epidemiologia y finalmente se hace referencia a diagnostico y tratamiento

Staphylococcus aureus productores de toxina del síndrome del shock tóxico-1 en el tracto genital inferior femenino. / [[Staphylococcus aureus producing toxic shock syndrome toxin 1 in the lower genital tract of the female]

Staphylococcus sp was investigated in the female lower genital tract of 102 healthy women aged between 18 and 48 years in San Luis, Argentina. Three hundred and six samples were obtained from labia, introitus and vagina (posterior fornix). Samples were plated on sheep blood, mannitol salt and Baird-Parker media. Strains were identified by tube coagulase test; thermonuclease, fibrinolysin, pigment and hemolysin production; glucose and mannitol utilization and novobiocin sensitivity. Antibiotic susceptibility was assayed. Strains were examined for their ability to produce staphylococcal enterotoxins (SE) and toxic shock syndrome toxin-1 (TSST-1). Fourteen women (13.7

) had S. aureus in one or more samples: 10.7

labia, 3.9

introitus and 3.9

vaginal. All strains were sensitive to cephalotin, clindamycin, erythromycin, gentamycin and chloramphenicol; 21.0

were intermediate to methicillin; 15.7

were resistant to methicillin, 94.7

to penicillin and 21.0

to tetracycline. Three strains (15.7

) produced SEB, three (15.7

) SED, one (5.7

) SEC and three (15.7

) TSST-1. Only one strain (5.7

) produced both SEB and TSST-1. All strains produced hemolysins. Coagulase negative staphylococci were found in 40.1

of vaginal samples: S. epidermidis (32.2

) and S. saprophyticus (9.8

) were identified.

Prevalencia de Staphylococcus aureus aislados de mastitis subclínica bovina en tambos de la cuenca lechera de la ciudad de San Luis. / [Prevalence of Staphylococcus aureus isolated from subclinical bovine mastitis in dairies of the city of San Luis]

In order to detect subclinical mastitis by means of California Mastitis Test and recounting of somatic cells, 163 cows from the dairies of San Luis city, Argentina, were examined. Seventy six individuals (46.6

) exhibited an inflammatory response ranging > or = 2+ grade and a cellular recounting value of > or = 5 x 10(5), data compatible with those of subclinical mastitis. Staphylococcus aureus was isolated from 39 (51.3

) cultures as estimated by the sum of the two last values listed in Table 1. Organisms were isolated by plating on brain heart infusion agar with 5

of sheep blood and on Baird-Parker media. One hundred and three S. aureus isolates recovered from 51 of 63 cows were characterized by coagulase activity by the tube method using human and bovine plasma; clumping factor; glucose and mannitol fermentation; thermonuclease (TNase), pigment, gelatinase, fibrinolysin, acetoin, hemolysin production; egg yolk, tellurite and catalase reaction and crystal violet types. All isolates were susceptible to cephalothin, clindamycin, methicillin, gentamycin and vancomycin; 94.1

were susceptible to chloramphenicol and 53.8

to G penicillin. Sixty three isolates (61.1

) were classified according to Hájek and Marsálek scheme as biotype C (bovine and ovine ecovar), 33 isolates (32.0

) were classified as biotype B (swine and poultry ecovar); 1 isolated (0.9

) as intermediate between B and D; 5 isolates (4.8

) as biotype A (human ecovar) and 1 isolated (0.9

) as biotype D (ecovar silvestres spp) (Table 2). Production of enterotoxins A to E and toxic shock syndrome toxin-1 (TSST-1) was determined by the optimal susceptibility plate method on 27 isolates (26.2

) which were coagulase 3+ to 4+ and TNase highly positive. None of them produced enterotoxins including TSST-1. The subclinical mastitis data and the prevalence of S. aureus coincide with those of other authors, both from Argentina and from other countries.

Cinética de la acción bacteriostática de chalconas naturales y de síntesis sobre una cepa de Staphylococcus aureus / Kinetics of the bacteriostatic action of synthetic and natural chalcones on a Staphylococcus aureus strain

Se estudió la acción bacteriostática ejercida por chalconas naturales (2,4-dihidroxichalcona y 2-hidroxi-4-metoxichalcona) y de síntesis (chalcona, 2-hidroxicalcona, 24-dihidroxichalcona y 2-hidroxi-4-metoxichalcona) sobre Staphylococcus aureus (cepa ATCC 25 923). Se determinó la influencia de la concentración de la natureza y posición de los sustituyentes de las drogas empleadas sobre la tasa de crecimiento específica del germen. Los ensayos cualitativos se hicieron en placas de agar nutritivo y mostraron la acción inhibitoria de chalcona y sus derivados dihidroxilados. Los resultados obtenidos distiguen el potente efecto bacteriostático de 2,4-dihidroxichalcona y 2,4-dihidrochalcona que en bajas concentraciones provocaron inhibición total en el crecimiento del microorganismo, de las otras chalconas estudiadas que solamente disminuyeron la tasa de crecimiento específica del germe hasta un valor límite. Se observa que la presencia de un grupo oxihidrilo en el anillo A o B de la 2-hidroxichalcona potencia su actividad bacteriostática siendo este efecto más pronunciado en la posición 4(anillo A) respecto de la posición 4 (anillo B). La introducción de un grupo metoxilo en la estructura de la 2-hidroxichalcona produce un decrecimiento de su potencia inhibitoria (AU)

Prevalencia de Staphylococcus aureus aislados de mastitis subclínica bovina en tambos de la cuenca lechera de la ciudad de San Luis. / [Prevalence of Staphylococcus aureus isolated from subclinical bovine mastitis in dairies of the city of San Luis]

In order to detect subclinical mastitis by means of California Mastitis Test and recounting of somatic cells, 163 cows from the dairies of San Luis city, Argentina, were examined. Seventy six individuals (46.6

) exhibited an inflammatory response ranging > or = 2+ grade and a cellular recounting value of > or = 5 x 10(5), data compatible with those of subclinical mastitis. Staphylococcus aureus was isolated from 39 (51.3

) cultures as estimated by the sum of the two last values listed in Table 1. Organisms were isolated by plating on brain heart infusion agar with 5

of sheep blood and on Baird-Parker media. One hundred and three S. aureus isolates recovered from 51 of 63 cows were characterized by coagulase activity by the tube method using human and bovine plasma; clumping factor; glucose and mannitol fermentation; thermonuclease (TNase), pigment, gelatinase, fibrinolysin, acetoin, hemolysin production; egg yolk, tellurite and catalase reaction and crystal violet types. All isolates were susceptible to cephalothin, clindamycin, methicillin, gentamycin and vancomycin; 94.1

were susceptible to chloramphenicol and 53.8

to G penicillin. Sixty three isolates (61.1

) were classified according to Hájek and Marsálek scheme as biotype C (bovine and ovine ecovar), 33 isolates (32.0

) were classified as biotype B (swine and poultry ecovar); 1 isolated (0.9

) as intermediate between B and D; 5 isolates (4.8

) as biotype A (human ecovar) and 1 isolated (0.9

) as biotype D (ecovar silvestres spp) (Table 2). Production of enterotoxins A to E and toxic shock syndrome toxin-1 (TSST-1) was determined by the optimal susceptibility plate method on 27 isolates (26.2

) which were coagulase 3+ to 4+ and TNase highly positive. None of them produced enterotoxins including TSST-1. The subclinical mastitis data and the prevalence of S. aureus coincide with those of other authors, both from Argentina and from other countries.

Cinética de la acción bacteriostática de chalconas naturales y de síntesis sobre una cepa de Staphylococcus aureus / Kinetics of the bacteriostatic action of synthetic and natural chalcones on a Staphylococcus aureus strain

Se estudió la acción bacteriostática ejercida por chalconas naturales (2',4'-dihidroxichalcona y 2'-hidroxi-4'-metoxichalcona) y de síntesis (chalcona, 2'-hidroxicalcona, 2'4-dihidroxichalcona y 2'-hidroxi-4-metoxichalcona) sobre Staphylococcus aureus (cepa ATCC 25 923). Se determinó la influencia de la concentración de la natureza y posición de los sustituyentes de las drogas empleadas sobre la tasa de crecimiento específica del germen. Los ensayos cualitativos se hicieron en placas de agar nutritivo y mostraron la acción inhibitoria de chalcona y sus derivados dihidroxilados. Los resultados obtenidos distiguen el potente efecto bacteriostático de 2',4'-dihidroxichalcona y 2',4'-dihidrochalcona que en bajas concentraciones provocaron inhibición total en el crecimiento del microorganismo, de las otras chalconas estudiadas que solamente disminuyeron la tasa de crecimiento específica del germe hasta un valor límite. Se observa que la presencia de un grupo oxihidrilo en el anillo A o B de la 2'-hidroxichalcona potencia su actividad bacteriostática siendo este efecto más pronunciado en la posición 4'(anillo A) respecto de la posición 4 (anillo B). La introducción de un grupo metoxilo en la estructura de la 2'-hidroxichalcona produce un decrecimiento de su potencia inhibitoria

Prevalencia de Staphylococcus aureus aislados de mastitis subclínica bovina en tambos de la cuenca lechera de la ciudad de San Luis / [Prevalence of Staphylococcus aureus isolated from subclinical bovine mastitis in dairies of the city of San Luis]

In order to detect subclinical mastitis by means of California Mastitis Test and recounting of somatic cells, 163 cows from the dairies of San Luis city, Argentina, were examined. Seventy six individuals (46.6

) exhibited an inflammatory response ranging > or = 2+ grade and a cellular recounting value of > or = 5 x 10(5), data compatible with those of subclinical mastitis. Staphylococcus aureus was isolated from 39 (51.3

) cultures as estimated by the sum of the two last values listed in Table 1. Organisms were isolated by plating on brain heart infusion agar with 5

of sheep blood and on Baird-Parker media. One hundred and three S. aureus isolates recovered from 51 of 63 cows were characterized by coagulase activity by the tube method using human and bovine plasma; clumping factor; glucose and mannitol fermentation; thermonuclease (TNase), pigment, gelatinase, fibrinolysin, acetoin, hemolysin production; egg yolk, tellurite and catalase reaction and crystal violet types. All isolates were susceptible to cephalothin, clindamycin, methicillin, gentamycin and vancomycin; 94.1

were susceptible to chloramphenicol and 53.8

) were classified according to Hájek and Marsálek scheme as biotype C (bovine and ovine ecovar), 33 isolates (32.0

) were classified as biotype B (swine and poultry ecovar); 1 isolated (0.9

) as intermediate between B and D; 5 isolates (4.8

) as biotype A (human ecovar) and 1 isolated (0.9

) as biotype D (ecovar silvestres spp) (Table 2). Production of enterotoxins A to E and toxic shock syndrome toxin-1 (TSST-1) was determined by the optimal susceptibility plate method on 27 isolates (26.2

) which were coagulase 3+ to 4+ and TNase highly positive. None of them produced enterotoxins including TSST-1. The subclinical mastitis data and the prevalence of S. aureus coincide with those of other authors, both from Argentina and from other countries.

Prevalencia de Staphylococcus aureus aislados de mastitis subclínica bovina en tambos de la cuenca lechera de la ciudad de San Luis / [Prevalence of Staphylococcus aureus isolated from subclinical bovine mastitis in dairies of the city of San Luis]

In order to detect subclinical mastitis by means of California Mastitis Test and recounting of somatic cells, 163 cows from the dairies of San Luis city, Argentina, were examined. Seventy six individuals (46.6

) exhibited an inflammatory response ranging > or = 2+ grade and a cellular recounting value of > or = 5 x 10(5), data compatible with those of subclinical mastitis. Staphylococcus aureus was isolated from 39 (51.3

) cultures as estimated by the sum of the two last values listed in Table 1. Organisms were isolated by plating on brain heart infusion agar with 5

of sheep blood and on Baird-Parker media. One hundred and three S. aureus isolates recovered from 51 of 63 cows were characterized by coagulase activity by the tube method using human and bovine plasma; clumping factor; glucose and mannitol fermentation; thermonuclease (TNase), pigment, gelatinase, fibrinolysin, acetoin, hemolysin production; egg yolk, tellurite and catalase reaction and crystal violet types. All isolates were susceptible to cephalothin, clindamycin, methicillin, gentamycin and vancomycin; 94.1

were susceptible to chloramphenicol and 53.8

) were classified according to Hájek and Marsálek scheme as biotype C (bovine and ovine ecovar), 33 isolates (32.0

) were classified as biotype B (swine and poultry ecovar); 1 isolated (0.9

) as intermediate between B and D; 5 isolates (4.8

) as biotype A (human ecovar) and 1 isolated (0.9

) as biotype D (ecovar silvestres spp) (Table 2). Production of enterotoxins A to E and toxic shock syndrome toxin-1 (TSST-1) was determined by the optimal susceptibility plate method on 27 isolates (26.2

) which were coagulase 3+ to 4+ and TNase highly positive. None of them produced enterotoxins including TSST-1. The subclinical mastitis data and the prevalence of S. aureus coincide with those of other authors, both from Argentina and from other countries.

Determinación de la calidad higiénica e investigación de Salmonella spp y Yersinia enterocolítica en helados. / [Determination of the sanitary quality and detection of Salmonella spp and Yersinia enterocolitica in ice cream]

In order to determine the sanitary quality of ice-creams and the presence of pathogenic or potentially pathogenic species of Salmonella and Yersinia enterocolitica, 50 samples from 5 different industrial and semi-industrial producers in San Luis (Argentine) were examined. The enumeration of coliforms was positive for all the samples with values less than or equal to 20/g. Fourteen per cent of the samples were positive for the investigation of Staphylococcus aureus in 1 g. For the plates enumeration 12.0

of the samples gave less than 10 u.f.c./g, 4.0

between 101 and 1000 and 4.0

between 1001 and 10,000. Fifteen strains were isolated, 26.6

biotype A (human ecovar) and the others biotype C (bovine ecovar). All of them were susceptible to chloramphenicol, cephalosporin and erythromycin; 46.6

to penicillin G and ampicillin; 93.3

to kanamycin (6.6

intermediate ones = I); 73.3

to methicillin (26.6

I); 86.6

to tetracycline (13.3

I). Six per cent of the samples over came the acceptability limit for S. aureus. Salmonella spp was not isolated. In 4.0

of the samples Y. enterocolitica were isolated, one of them typified as B1; 0:3, 50, 51, Lis Xz. The latter, isolated in samples with values of coliforms inferior to the limit fixed by some legislations, suggests a post elaboration contamination.