B-type natriuretic peptide over N-terminal pro-brain natriuretic peptide to predict incident atrial fibrillation after cryptogenic stroke.

BACKGROUND AND PURPOSE: B-type natriuretic peptide (BNP) and N-terminal pro-brain natriuretic peptide (NT-proBNP) are well-known surrogates of atrial fibrillation (AF) detection but studies usually present data on either BNP or NT-proBNP. The aim was to determine and directly compare the validity of the two biomarkers as a tool to predict AF and guide prolonged cardiac monitoring in cryptogenic stroke patients. METHODS: Non-lacunar acute ischaemic stroke (<72 h) patients over 55 years of age with cryptogenic stroke after standard evaluation were included in the Crypto-AF study and blood was collected. BNP and NT-proBNP levels were determined by automated immunoassays. AF was assessed by 28 days' monitoring. Highest (optimizing specificity) and lowest (optimizing sensitivity) quartiles were used as biomarker cut-offs to build predictive models adjusted by sex and age. The integrated discrimination improvement index (IDI) and DeLong test were used to compare the performance of the two biomarkers. RESULTS: From 320 patients evaluated, 218 were included in the analysis. AF was detected in 50 patients (22.9%). NT-proBNP (P < 0.001) and BNP (P < 0.001) levels were higher in subjects with AF and their levels correlated (r = 0.495, P < 0.001). BNP showed an increased area under the curve (0.720 vs. 0.669; P = 0.0218) and a better predictive capacity (IDI = 3.63%, 95% confidence interval 1.36%-5.91%) compared to NT-proBNP. BNP performed better than NT-proBNP in a specific model (IDI = 3.7%, 95% confidence interval 0.87%-6.5%), whilst both biomarkers performed similarly in the case of a sensitive model. CONCLUSIONS: Both BNP and NT-proBNP were increased in cryptogenic stroke patients with AF detection. Interestingly, BNP outperforms NT-proBNP, especially in terms of specificity.

Large vessel occlusion is independently associated with atrial fibrillation detection.

BACKGROUND AND PURPOSE: Covert paroxysmal atrial fibrillation (pAF) is the most frequent cause of cardiac embolism. Our goal was to discover parameters associated with early pAF detection with intensive cardiac monitoring. METHOD: Crypto-AF was a multicentre prospective study (four Comprehensive Stroke Centres) to detect pAF in non-lacunar cryptogenic stroke continuously monitored within the first 28 days. Stroke severity, infarct pattern, large vessel occlusion (LVO) at baseline, electrocardiography analysis, supraventricular extrasystolia in the Holter examination, left atrial volume index and brain natriuretic peptide level were assessed. The percentage of pAF detection and pAF episodes lasting more than 5 h were registered. RESULTS: Out of 296 patients, 264 patients completed the monitoring period with 23.1% (61/264) of pAF detection. Patients with pAF were older [odds ratio (OR) 1.04, 95% confidence interval (CI) 1.01-1.08], they had more haemorrhagic infarction (OR 4.03, 95% CI 1.44-11.22), they were more likely to have LVO (OR 4.29, 95% CI 2.31-7.97) (P < 0.0001), they had a larger left atrial volume index (OR 1.03, 95% CI 1.01-1.1) (P = 0.0002) and they had a higher level of brain natriuretic peptide (OR 1.01, 95% CI 1.0-1.1). Age and LVO were independently associated with pAF detection (OR 1.06, 95% CI 1.00-1.16, and OR 4.58, 95% CI 2.27- 21.38, respectively). Patients with LVO had higher cumulative incidence of pAF (log rank P < 0.001) and more percentage of pAF > 5 h [29.6% (21/71) vs. 8.3% (12/144); OR 4.62, 95% CI 2.11-10.08; P < 0.001]. In a mean follow-up of 26.82 months (SD 10.15) the stroke recurrence rate was 4.6% (12/260). CONCLUSIONS: Large vessel occlusion in cryptogenic stroke emerged as an independent marker of pAF.

[Investigation of Trichomonas vaginalis through different methodologies during pregnancy]. / Investigación de Trichomonas vaginalis durante el embarazo mediante diferentes metodologías.

The aim of this study was to conduct a survey regarding the prevalence of trichomoniasis in pregnant patients and to evaluate the utility of different diagnostic methods. Two hundred and twenty three vaginal swab specimens from pregnant women were prospectively examined. Trichomonas vaginalis was investigated by various microscopic examinations, solid culture medium and liquid culture medium. The sensitivity and specificity of microscopy were evaluated by considering both culture media as the "gold standards". The prevalence of T. vaginalis obtained by both culture media (liquid plus solid media) was 4.5% (10/223). The prevalence of T. vaginalis obtained by direct smear, May-Grunwald Giemsa staining, sodium acetate-acetic acid-formalin (SAF)/Methylene blue staining-fixing technique, solid medium and liquid medium was 1.3%, 1.8%, 1.8% and 4.5%, respectively. The sensitivity of the direct smear was 30 %, but for the May-Grunwald Giemsa staining and the SAF/Methylene blue staining-fixing technique was 40%. Considering the three microscopic examinations altogether, the sensitivity rose to 50% and the specificity was 100% for all of them. The solid medium detected only 50% of the positive cases; the liquid medium detected 100%. Due to the low sensitivity obtained with microscopy in asymptomatic pregnant patients, we recommend the use of the liquid medium during pregnancy, in order to provide an early treatment.

[Prevalence of vaginal candidiasis in pregnant women. Identification of yeasts and susceptibility to antifungal agents]. / Prevalencia de candidiasis vaginal en embarazadas. identificación de levaduras y sensibilidad a los antifúngicos.

Pregnant women are more susceptible to both vaginal colonization and infection by yeast. Our objectives were to determine the prevalence in pregnant women of yeasts isolated from vaginal exudates and their susceptibility to current antifungal drugs. A total of 493 patients was studied between December 1998 and February 2000. The prevalence of Candida spp. was 28% (Candida albicans 90.4%; Candida glabrata 6.3%; Candida parapsilosis 1.1%, Candida kefyr 1.1 %; unidentified species 1.1 %). The diffusion test in Shadomy agar was employed to determine the susceptibility to fluconazole, ketoconazole, itraconazole and nistatine. All C. albicans, C. kefyr and C. parapsilosis isolates were susceptible in vitro to the antifungal agents tested, while 1 in 6 C. glabrata isolates showed resistance to azole drugs; all strains were susceptible to nistatine. In pregnant women, C. albicans was the yeast most frequently isolated from vaginal exudates; it continues to be highly susceptible to antifungal drugs. Azole resistance was detected only among C. glabrata isolates. Identification to the species level is recommended, specially in cases of treatment failure and recurrent or chronic infection.

[Deoxyribonuclease activity detection in Clostridium chauvoei strains]. / Detección de la actividad de desoxiribonucleasa (DNasa) en cepas de Clostridium chauvoei.

Beta toxin of C. chauvoei has desoxiribonuclease (DNase) activity which is regarded as one of its virulence factors. The production of DNase was detected in strains isolated from bovines, using as controls C. chauvoei ATCC 10092, and C. perfringens Type A and C. septicum, both laboratory isolates. The enzyme activity was made evident on a DNA substrate observing the macroscopic degradation. A simple methodology was developed using a commercial medium for DNase test, with the incorporation of sterile horse serum. Each strain was streaked on the surface of the medium, incubated in anaerobic atmosphere at 37 degrees C for 48 hours. The plates were revealed with HCI 1 N. The appearance of a clear and transparent zone around and under the microbial growing was considered a positive reaction. Enzyme activity was detected in 10 of 12 strains and also in the controls. The serum addition to the commercial basal medium allows the optimum development of the microorganism showing the enzymatic digestion zone.

Penicillin-binding proteins in Listeria monocytogenes.

The Penicillin-Binding Proteins (PBP) of Listeria monocytogenes 29-CCM-A: 454 (ATCC 15313) are described by the use of 125I-Penicillin X as radiotracer. The membranes of this tolerant bacilli contained at least five proteins with different affinities for the radiotracer or Dicloxacillin. The molecular weights of these proteins were estimated as 76, 74, 67, 66 and 47 KDa. Dicloxacillin induced the formation of straight filaments when present at sub-inhibitory concentrations, while Penicillin G did not induce any visible alteration in the morphology of this microorganism.

Antiviral effects of Melia azedarach L. leaves extracts on Sindbis virus-infected cells.

Partially purified extracts from leaves of Melia azedarach L. (MA) exert a broad range of antiviral effects on DNA and RNA viruses. The effect of MA on different stages of Sindbis virus replicative cycle in BHK cells was investigated. Under one-step growth conditions MA afforded a greater than 90% inhibition in virus yield if added to the cell cultures 2 h before or after infection, and when added 4 h after infection MA still caused a greater than 80% inhibition. Analysis of early events following Sindbis virus infection showed that MA did not affect viral adsorption to or penetration in BHK cell. In contrast, viral RNA and protein synthesis was almost totally inhibited in cells pretreated with MA 2 h before infection, while cellular macromolecular synthesis was similar in MA-treated and untreated cell cultures.

Induction of a refractory state to viral infection in mammalian cells by a plant inhibitor isolated from leaves of Melia azedarach L.

A partially purified plant inhibitor (Meliacin) isolated from Melia azedarach L induced in cells a refractory state to virus infection. Meliacin was active in a large variety of continuous and/or primary cell cultures. A state of maximum virus resistance was achieved after 2 h of incubation and was maintained for at least 15 h; later on it declined but it was fully regained after a second pulse of Meliacin. Interferon was not detected in the supernatant of cells treated with Meliacin and a measurable increase in ds-RNA dependent protein kinase activity was not observed in extracts of Meliacin-treated cells. The antiviral state was not transferred by either extracellular fluid or direct cell-to-cell contact. An active cell metabolism was required for Meliacin action, which was partially reversed in the presence of actinomycin D. It appears that Meliacin is not an interferon-like substance, which induces an antiviral state based on a still unexplained mechanism.

Detection of the etx gene (epsilon-toxin inducer) in plasmids of high molecular weight in Clostridium perfringens type D.

The purpose of this work is to correlate the production of epsilon-toxin in a set of strains of Clostridium perfringens type D with the presence of the etx gene, either genomic or in plasmids. Total DNA obtained from strains with a different level of toxin production was explored by PCR and all the strains showed the amplification signal. Different methods were used to obtain plasmid profiles and all of the bands were assayed by PCR. The detection of the etx gene was only shown in several high molecular plasmids. These results were confirmed by a Southern blot. We suggest that the localization of the etx gene in different plasmids could be associated with the epsilon-toxin production level.

Antiviral activity of enterocin CRL35 against herpesviruses.

Enterocin CRL35 is an antibacterial polypeptide of 3.5 x 10(3) Da produced by Enterococcus faecium CRL35. A series of experiments are described that show the enterocin also had antiviral activity against thymidine-kinase positive (tk+) and deficient (tk-) strains of herpes simplex (HSV) type 1 and 2 in Vero and BHK-21 cells. This activity was observed at 100 microg/ml, 15-fold lower than the cytotoxic concentration. In both cell lines there was a 2 log inhibition of infectivity. The compound inhibited viral multiplication in a dose-dependent manner and had no virucidal effect. Enterocin CRL35 also inhibited the virion-associated host shutoff in infected Vero cells showing that intracellular viral multiplication was affected.

Flagellin, a major protein present in SDS-PAGE profiles of Sarkosyl-OMP-enriched fractions from Bordetella bronchiseptica Bvg- or modulated Bvg+ strains.

The bvg or vir locus positively regulates the expression of many Bordetella virulence-associated determinants (encoded by vag genes), including cell envelope proteins, in response to environmental stimuli. On the other hand, several genes named vrg genes are negatively controlled by the bvg regulon (Knapp and Mekalanos, 1988). Flagellin is encoded by a vrg gene, which is expressed when the principal virulence factors are eliminated during antigenic modulation or in phase variants (Akerley et al., 1992). We have previously analyzed SDS-PAGE profiles of Sarkosyl-outer membrane protein (OMP)-enriched fractions from B. bronchiseptica Bvg- and modulated Bvg+ strains and reported a major band associated with the avirulent phenotype (Passerini de Rossi et al., 1995). In order to characterize this band we have purified flagellar filaments from Bvg- and modulated Bvg+ strains, and analyzed them by SDS-PAGE. These profiles revealed a single major band of 40 or 45 kDa depending on the strain. The N-terminal amino acid sequence of the putative flagellin expressed by BB7200a was identical over the first 21 residues analyzed to that of the flagellin from the modulated strain BB7865 reported by Akerley et al. (1992). Comparison of the SDS-PAGE profile of flagellar filaments with that of the OMP-enriched fraction of the corresponding strain showed that the flagellum-associated polypeptide had the same electrophoretic mobility as that of the characteristic band of the avirulent phenotype. Furthermore, this band was absent in the OMP-enriched fraction profile from a Bvg- strain subjected to a treatment that removes flagella. Our results indicate that the major protein observed in SDS-PAGE profiles of Sarkosyl-OMP-enriched fractions from B. bronchiseptica Bvg- and modulated Bvg+ strains corresponds to flagellin.

Incidence of Chlamydia trachomatis and other potential pathogens in neonatal conjunctivitis.

OBJECTIVE: Ocular infection in neonatology is a permanent and important health problem. To improve primary attention, prevention, and control, the study of the potential bacterial etiology of all consecutive cases of conjunctivitis was incorporated as a regular procedure in primary care from July 1995 to December 1998. MATERIALS AND METHODS: Prof. A. Posadas Hospital (Great Buenos Aires) has an average of 4294 births per year. This report analyzes the results obtained in 332 infants (age range, 0-30 d) with conjunctivitis. Clinical conjunctivitis was diagnosed in inpatients and outpatients by the same specialized staff. Isolation and characterization of bacteria were done by conventional microbiologic methods, including specific search for Neisseria gonorrhoeae and Chlamydia trachomatis. Chlamydia trachomatis was studied by antigen immunodetection and polymerase chain reaction, and genotyped by restriction fragment length polymorphism. RESULTS: Conjunctivitis had an incidence (cases per 1000 live births) of 39.6 in 1995, 25.3 in 1996, 15.4 in 1997, and 15.2 in 1998. Microbial growth was detected in 167 (50.3%) of 332 cases. Ocular C. trachomatis infection was detected in 26 cases (7.83%). Five of seven isolates in tissue cultures belonged to type E and two to type G. Bacteria from respiratory ecology were the main isolates: Haemophilus influenzae (16.9%), Streptococcus pneumoniae (12.3%), and Staphylococcus aureus (8.7%). Haemophilus influenzae isolates were not serotyped and 17.2% of them were b-lactamase producers. In 15 cases both H. influenzae and S. pneumoniae were isolated together. Of S. pneumoniae, 4.9% were oxacillin resistant. CONCLUSIONS: There has been a decline in the total number of cases of neonatal conjunctivitis, but the disease is still an important health problem. Chlamydia trachomatis also shows a decreasing profile with an incidence of (cases per 1000 live births) 4.39 in 1995, 1.85 in 1996, 1.01 in 1997, and 0.78 in 1998, and a tendency to show more incidence in spring-summer and significant accumulation of cases in babies between 7 and 9 days of age. Haemophilus influenzae alone (12.3%) or associated with S. pneumoniae (4.5%) appears as a prevalent potential bacterial pathogen. A significant accumulation of H. influenzae and S. pneumoniae cases occurs in winter. In 47.6% of cases, there was no bacterial growth. No significant seasonal differences in percentage of negative cultures or among the three-day age groups were detected. Neisseria gonorrhoeae was not found associated with ophthalmia neonatorum in this series.

Toxocara canis in experimentally infected pigs: migratory pattern and tissue lesions.

Fifteen Yorkshire female pigs were inoculated with 100,000 infective T. canis eggs. Three animals were used as uninfected controls. Groups of three infected pigs were euthanized by accepted methods on days 7, 14, 21, 28 and 126 p.i., respectively. Larvae were recovered from all animals included in each group slaughtered on days 7 and 14 p.i.; on day 21 p.i. from two pigs, on day 28 p.i. from one, and no larvae were found on day 126 p.i. Differences in the mean number of larvae per gram in lymph nodes, liver and lungs between slaughter days, were significant for livers on day 7 p.i. and for lungs on day 14 p.i. (P < 0.10). The decrease over time was significant in all the organs that previously had larvae. Larvae were not found in the other organs and tissues analysed. Macroscopical lesions were found in the liver, lungs and lymph nodes on days 7, 14, 21, and 28 p.i. The entire surface of the liver was covered with small white spots on day 7 p.i., on days 14 and 21 p.i. the spots were distinctly nodular and, in some places, individual lesions were confluent. Lesions had apparently started to heal on days 28 and 126 p.i. appearance was normal. Lymph nodes were enlarged and oedematous during the first 4 weeks and the lungs had small areas of consolidation visible all over the surface, but by day 126 p.i., no visible lesions could be seen. Microscopical lesions were observed in the liver on day 7 p.i., with a largely periportal hepatitis. Numerous eosinophils and lymphocytes were present. The typical granulomatous reaction was observed on days 14 and 21 p.i. with a central necrotic core and a narrow region of fibroblastic tissue. By day 28 p.i. lesions had almost disappeared and the number of eosinophils was fewer. There were fewer leukocytes and the fibrous tissue had disappeared from the liver on day 126 p.i. For the first 3 weeks, pictures of the lymph nodes and the lungs were characterised by the formation of a granuloma. In the center of the granuloma larvae were observed. The majority of the lesions had healed by day 126 p.i.

[Iatrogenic gastrointestinal hemorrhages. A review of 108 cases (author's transl)]. / Hemorragias digestivas yatrógenas. Consideraciones en torno a 108 casos.

Macroscopic gastrointestinal hemorrhages caused by the consumption of oral drugs are relatively scarce among patients receiving antirheumatic treatment. On the other hand, in a high percentage of all cases of digestive bleeding, antirheumatic drugs were administered shortly beforehand. A review of 216 cases with hematemesis and/or melena are presented. In 50 percent of the patients there was evidence of previous administration of potentially ulcerogenic drugs capable of causing hemorrhages in the digestive tract. Salicylates predominated among the compounds that were considered to be responsible for hemorrhages (salicylates, corticosteroids, reserpine, and other antirheumatic products). The mechanisms involved in producing iatrogenic hemorrhages were examined and the drugs were classified as precipitating and directly ulcerogenic compounds. Precipitating drugs were those which were able to reactivate a preexisting lesion (reserpine, glucocorticoids, phenylbutazone, etc.). The ulcerogenic drugs included those products that could provoke a lesion of previously unimpaired digestive mucosa (salicylates).

[Syphilis in adolescent mothers in the city of Posadas, Province of Misiones]. / Sifilis en madres adolescentes en la ciudad de Posadas, Provincia de Misiones.

During three months (April to June 1997) 1,238 consecutive pregnant women were studied at the time of delivery at the Madariaga public Hospital. Syphilis was confirmed in 26 (2.1%) women, and 15 cases (57.7%) of congenital syphilis were demonstrated in newborns one of whom was a stillborn. Of the syphilitic women 61.5% were 20 years old (average), 65.4% were single, 19.2% had a stable partner and 15.4% were married; 70% of them had finished elementary school (seven years), but despite this discrete level of instruction and that they were benefited with free health attention, 73% of them had not started or completed the pregnancy control. None of these women acted as sexual workers or were drug users; 57.7% were unemployed and the remainder worked as domestic servants or were still going to school. Menarca started at 13 (average) and the age of the first sexual activity was 15 (average). The distribution of the cases of syphilis within the city area shows four clusters that coincide with the lower income population, but not with marginal groups. The failure to submit to medical control during pregnancy among syphilitic women is directly linked with an increased risk for congenital syphilis. The specific prevalence of syphilis in women (20 years old or less) pregnant or not, shows an alarming hidden epidemic situation. An interinstitutional and communitary program, with direct interventions within the detected population clusters, is now underway in order to control syphilis. Undesired pregnancy and syphilis seem to be associated with adolescent unsafe sex conducts. A coordinated program between Public Health Service and National Misiones University is operating, visiting home by home, in order to decrease or eliminate congenital syphilis and is considered a priority health problem. Unfortunately, if sexual conducts do not undergo changes in the near future, at least by the correct use of condoms, HIV will replace syphilis.

[Assays of cytotoxicity and antiviral activity of crude and semipurified extracts of green leaves of Melia azedarach L]. / Ensayos de citotoxicidad y actividad antiviral de extractos crudos y semipurificados de hojas verdes de Melia azedarach L.

Crude extracts from fresh green leaves of Melia azedarach L contain an antiviral factor (FAV) able to inhibit the replication of several animal viruses, e.g. Polio, VSV, HSV, FMDV, Sindbis, Junín, Pichinde and Tacaribe in Vero or BHK-21 cells. Crude preparations were subjected to different steps of purification like chromatography on Sephadex G-100 and DEAE-Sephadex. The antiviral activity of G-100 and DEAE fractions was fully conserved, whereas contaminating proteins were lost. Two types of cytotoxicity tests were performed with the different fractions. Two-fold serial dilutions of each of them were added to preformed monolayers of Vero or BHK-21 cells and cellular viability was tested. While crude extracts were toxic at low dilutions (less than or equal to 1:10), G-100 and DEAE fractions were not. The other cytotoxicity assay consisted in seeding the cells in the presence of different concentrations of each fraction. G-100 fraction affected cell growth at low dilutions (less than or equal to 1:5), while DEAE fraction did not. It should be remarked that the purification procedure rendered a partial purified DEAE fraction with an increased specific activity (antiviral activity/mg of protein). It is concluded that an antiviral factor devoid of toxicity exists in M. azedarach L extracts, which exhibited a broad spectrum of antiviral activity.

[Early stages in the replication of aphthous fever virus. Kinetics of partial degradation and sites for the establishment of penetrating residual virus]. / Etapas tempranas en la replicación del virus de la fiebre aftosa. (VFA). Cinética de la degradación parcial y sitios de estabilización del virus penetrante residual.

At input multiplicities between 5-10 UFP/cell FMDV O1 Caseros adsorb in BHK21 Clon 13 cells at a rate of 5-20% depending whether cells are in suspension or in monolayers. At least four washings with medium are required to eliminate non specifically adsorbed virions. The remaining attached virus appears to be in contact with "specific" receptors of the cytoplasmic membrane. After penetration, 80% of virus became degraded to slow molecular weight material which is detected at first in the subcellular fraction and is gradually excreted out of the cells. The degradation process occurs from 0 to 15 minutes and it is demonstrated by a parallel decrease in infectivity and stability of purified labelled FMDV O1 Caseros. The 20% remaining virus is found firmly attached to a subcellular fraction precipitable at 15,000 xg. Parental residual infectivity remains remarkably stable for 90 min at which time newly synthetized RNA appears. Fraction of 15,000 xg from infected cultures was obtained at 60 min PI and incubated in vitro at 37 C. The infectivity remains unaltered for a period of 120 min even if the preparation is treated with 0.2% of triton x 100. Fraction of 15,000 xg from infected and control cultures obtained at different time PI were seeded on a linear sucrose gradient. A sharp peak of acid phosphatase associated with the lower mobility bands indicates the presence of intact lysosome structures. A shoulder of the enzyme activity is detected between the two main protein bands. Associated with the region rich in unbroken lysosomes, a very sharp peak of infectivity and/or 3H uridine or 32P labelled incoming virus can be detected. A different pattern of the residual incoming infectivity is found associated with the more rapid sedimentation protein band. 3H uridine incorporation at the beginning of viral RNA synthesis initiation shows that an important amount of newly synthesized viral RNA is found in the lower mobility band of the 15,000 xg fraction. Some incorporation is also detected in the faster band. The results presented here suggest that some functional activity is associated with the residual virus present at the beginning of infection in the 15,000 xg fraction. It can also be accepted that this virus penetrates by pinocytosis of specific receptors at the cytoplasmic membrane.

[Bacillus subtilis BSA 170 trp- ura-: a new nutritional mutant with absolute requirements for exogenous tryptophan and uracil for its growth]. / Bacillus subtilis BSA 170 trp- ura-: un nuevo mutante nutricional con requerimientos absolutos de triptofano y uracilo exógenos para su crecimiento.

A new Bacillus subtilis mutant was prepared, with a double nutritional requirement for uracil and tryptophan. The mutant, designed Bacillus subtilis BSA 170 trp- ura-, was constructed by transformation method, acting B. subtilis strain PB 168 trp- as recipient and B. subtilis strain PB 3308 ura- as transforming DNA donor cells. The BSA 170 trp- ura- strain was selected by replication of transformed population on nutritionally selective media. Competence development induction and genetic markers transformability were tested. The new mutant was competent by Young and Spizizen's methodology. Furthermore, both markers, uracil and tryptophan, may be transformed when B. subtilis BSA 170 trp- ura- competent cells are treated with transforming DNA isolated from B. subtilis PB 19, prototroph. Transformation frequency rate for each marker alone was far larger than that reached for both taken together.

[Obtaining dicloxacillin-resistant mutants in Listeria monocytogenes]. / Obtención de mutantes dicloxacilina resistentes en Listeria monocytogenes.

We obtained ten Dicloxacillin resistant mutants from Listeria monocytogenes ATCC: 15313 (29-CCM-A: 454). None of the mutants could be differentiated from the parental strain (except for their increased resistance) neither using conventional biochemical assays nor by analysis of the electrophoretic pattern of their detergent-soluble proteins (Figure 1). The wild type strain and some of these mutants were tolerant for Dicloxacillin and/or Penicillin G, but no rigorous correlation with each decrease in their susceptibility was observed (Table 1). Morphological studies showed that some of the resistant strains (growing at subinhibitory concentrations of Dicloxacillin) presented differences, including the formation of helical structures (Figures 2-5).

[Viability of Bacillus subtilis auxotrophs in the absence of their essential metabolites]. / Viabilidad de Bacillus subtilis auxotrofos en ausencia de sus metabolitos esenciales.

The effect of tryptophan and uracil starvation on the viability of the transformant B. subtilis BSA 170 trp- ura- and its parent strains Bacillus subtilis PB 168 trp -C and Bacillus subtilis PB 3308 ura- was examined. These studies were performed at the conditions for competence development, during 16 hours. Our results showed that B. subtilis BSA 170 was resistant to tryptophan-less death during all the assay and was also resistant to uracil-less death during three hours. After this time, viability measurements revealed less colony forming units per milliliter, and decrease of the culture absorbances. The uracil-less death required the presence of tryptophan suggesting that protein synthesis is needed. The parental strains exhibit similar behavior. Bacillus subtilis PB 168 was resistant to tryptophan-less death and B. subtilis PB 3308 showed decrease of the viability after uracil starvation comparable to that of the transformant strain.