Cobalamin cbiP mutant shows decreased tolerance to low temperature and copper stress in Listeria monocytogenes

Background

Listeria monocytogenes is a foodborne pathogen that causes listeriosis in humans. This pathogen activates multiple regulatory mechanisms in response to stress, and cobalamin biosynthesis might have a potential role in bacterial protection. Low temperature is a strategy used in the food industry to control bacteria proliferation; however, L. monocytogenes can grow in cold temperatures and overcome different stress conditions. In this study we selected L. monocytogenes List2-2, a strain with high tolerance to the combination of low temperature + copper, to understand whether the cobalamin biosynthesis pathway is part of the tolerance mechanism to this stress condition. For this, we characterized the transcription level of three cobalamin biosynthesis-related genes (cbiP, cbiB, and cysG) and the eutV gene, a transcriptional regulator encoding gene involved in ethanolamine metabolism, in L. monocytogenes strain List2-2 growing simultaneously under two environmental stressors: low temperature (8 °C) + copper (0.5 mM of CuSO₄ × 5H₂O). In addition, the gene cbiP, which encodes an essential cobyric acid synthase required in the cobalamin pathway, was deleted by homologous recombination to evaluate the impact of this gene in L. monocytogenes tolerance to a low temperature (8 °C) + different copper concentrations.

Results

By analyzing the KEGG pathway database, twenty-two genes were involved in the cobalamin biosynthesis pathway in L. monocytogenes List2-2. The expression of genes cbiP, cbiB, and cysG, and eutV increased 6 h after the exposure to low temperature + copper. The cobalamin cbiP mutant strain List2-2ΔcbiP showed less tolerance to low temperature + copper (3 mM) than the wild-type L. monocytogenes List2-2. The addition of cyanocobalamin (5 nM) to the medium reverted the phenotype observed in List2-2ΔcbiP.

Conclusion

These results indicate that cobalamin biosynthesis is necessary for L. monocytogenes growth under stress and that the cbiP gene may play a role in the survival and growth of L. monocytogenes List2-2 at low temperature + copper.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-022-00376-4.

Molecular analysis of microbiota along the digestive tract of juvenile Atlantic salmon (Salmo salar L.)

Dominant bacterial microbiota of the gut of juvenile farmed Atlantic salmon was investigated using a combination of molecular approaches. Bacterial community composition from the stomach, the pyloric caeca, and the intestine was assessed by extracting DNA directly from each gut compartment. Temporal temperature gradient gel electrophoresis (TTGE) analysis of 16S ribosomal DNA (rDNA) amplicons showed very similar bacterial compositions throughout the digestive tract. Band sequencing revealed a narrow diversity of species with a dominance of Pseudomonas in the three compartments. However, cloning revealed more diversity among the Pseudomonas sequences. To confirm these results, we analyzed the bacterial community by amplifying the variable 16S-23S rDNA intergenic spacer region (ITS). Similar ITS profiles were observed among gastrointestinal compartments of salmon, confirming the TTGE results. Moreover, the dominant ITS band at 650 bp, identified as Pseudomonas, was observed in the ITS profile from fish collected in two seasons (July 2003 and 2004). In contrast, aerobic culture analysis revealed Shewanella spp. as the most prevalent isolate. This discrepancy was resolved by evaluating 16S rDNA and ITS polymerase chain reaction amplification efficiency from both Shewanella and Pseudomonas isolates. Very similar efficiencies were observed in the two bacteria. Hence, this discrepancy may be explained by preferential cultivation of Shewanella spp. under the experimental conditions. Also, we included analyses of pelleted feed and the water influent to explore environmental influences on the bacterial composition of the gut microbiota. Overall, these results indicate a homogeneous composition of the bacterial community composition along the gastrointestinal tract of reared juvenile salmon. This community is mainly composed of Pseudomonas spp., which could be derived from water influent and may be selectively associated with salmon in this hatchery.

Reactivity of 1,4-dihydropyridines toward alkyl, alkylperoxyl radicals, and ABTS radical cation

A series of C4-substituted 1,4-dihydropyridines (DHP) with either secondary or tertiary nitrogen in the dihydropyridine ring were synthesized. All of these compounds together with some commercial DHP derivatives were tested for potential scavenger effects toward alkyl, alkylperoxyl radicals, and ABTS radical cation in aqueous media at pH 7.4. Kinetic rate constants were assessed either by UV/vis spectroscopy or GC/MS techniques. Tested compounds reacted faster toward alkylperoxyl radicals and ABTS radical cation than alkyl ones. N-Ethyl-substituted DHPs showed the lowest reactivity. Kinetic results were compared with either trolox or nisoldipine. Using deuterium kinetic isotope effect studies, we have proved that the hydrogen of the 1-position of the DHP ring is involved in the proposed mechanism. This fact is mostly noticeable in the case of alkyl radicals. In all cases, the respective pyridine derivative was detected as the main product of the reaction.

Immunoglobulin G antibody response to infection with coccoid forms of Helicobacter pylori

An increasing number of studies support a potential role for coccoid forms in Helicobacter pylori infection. Evidence for this was obtained through scanning microscopy, genetic analysis for virulence traits, examination of the presence and activity of key enzymes, and other methods. We studied the serum immunoglobulin G responses to coccoid H. pylori forms by enzyme-linked immunosorbent assay (ELISA) and immunoblotting and compared them with those of bacillary cells. Sera from a total of 295 infected individuals were studied; these included sera from 100 patients with duodenal ulcers, 98 patients with nonulcer dyspepsia, 11 patients with gastroduodenal cancer, and 86 asymptomatic individuals. Initially, we characterized and selected coccoid and bacillary antigenic preparations by one-dimensional (1-D) and 2-D gel electrophoresis and immunoblotting. Data showed that coccoid and bacillary preparations with comparable protein contents have similar patterns in 1-D and 2-D electrophoresis gels and antigenic recognition at blotting. These results revealed that coccoid and spiral antigens in ELISA can equally recognize specific antibodies to H. pylori in sera from infected individuals. The analysis of the spiral and coccoid preparations by Western blotting showed no major differences in antigen recognition. No specific bands or profiles associated with a single gastric condition were identified.

[Fetal drug addiction as a consequence of maternal cocaine free base abuse during pregnancy]

BACKGROUND

Fetal drug addiction is a serious public health problem. In the United States 10 to 15% of children have been exposed "in utero" to cocaine. In a Chilean public health service, more than 200 offspring of cocaine free base abuser have been detected.

AIM

To analyze the clinical and social features of 100 children exposed to cocaine free base during fetal development.

PATIENTS AND METHODS

Clinical features of children born from cocaine free base consume mothers were described at birth. During subsequent follow up, growth and development, disease episodes, developmental alterations and social situation were recorded. Data was compared with other newborns from the same health service.

RESULTS

Compared to their normal counterparts, exposed children has a lower birth weight, the frequency of premature babies was thrice higher, and small-for-gestational age children were four times more common. There was also a higher prevalence of cardiac malformations, seizures and apnea. Hospital admissions were more frequent, prolonged and required more complex facilities. During follow up, undernutrition and stunting were more prevalent. Psychomotor retardation was present in 67% of children and behavioral disturbances in 93%. Most of these children are governmental protection.

CONCLUSIONS

Strategies to prevent drug abuse during pregnancy and its devastating medical and social consequences should be urgently developed (Rev Méd Chile 2000; 128: 1093-1100).

[Evaluation of Nugent and Amsel criteria for the diagnosis of bacterial vaginosis]

BACKGROUND

Bacterial vaginosis (BV) is a common disease in reproductive-age women and is associated to important gynecologic and obstetric complications.

AIM

To study the occurrence of BV in apparently healthy women attending family planning clinics, using Amsel and Nugent diagnostic criteria.

MATERIAL AND METHODS

Two hundred thirty nine women consulting for symptoms associated to cervicovaginitis, were studied. A sample from the lateral walls of the vagina was obtained with a sterile swab for microscopic analysis, Gram stain and amine test.

RESULTS

According to Amsel and Nugent criteria a 31.1% and 31.8% BV prevalence was observed. The sensitivity and specificity of Nugent criteria, compared with Amsel criteria were 83.3% and 92.1%, respectively.

CONCLUSIONS

The high prevalence of BV found in this study suggests that this vaginal infection should be diagnosed with standardized methods. Nugent criteria are economic easy to perform and sensitive and we propose that they should be used in local health centers.

[Risk factors for home deaths due to pneumonia among low socioeconomic level Chilean children, Santiago de Chile (1994)]

BACKGROUND

Pneumonia is the main cause of late infant mortality in Chile. Over 60% of these deaths occur at home. The lack of hospital beds and the inadequate outpatient management are contributing factors.

AIM

To assess risk factors for home deaths due to pneumonia in Chilean children.

PATIENTS AND METHODS

The clinical and environmental histories of 53 (39 male) children that died due to pneumonia in their homes were analyzed. The cause of death was confirmed by necropsy with histopathological studies in all cases. These cases were compared with 88 control children of similar age, gender, socioeconomic status and living in the same geographical area of Metropolitan Santiago.

RESULTS

Fifty four percent of deceased children were of less than 3 months of age and only 3 cases and their controls were above 1 year old. Identified risk factors for death were malnutrition with an odds ratio of 30.6 (CI 3.9-64.8, p < 0.001), low birth weight with an odds ratio of 5 (CI 1.8-14.1, p < 0.001), previous admissions to hospitals with an odds ratio of 5.79 (CI 2-17.1, p < 0.001), congenital malformations (mainly cardiac) with an odds ratio of 8.4 (CI 2-39.9, p = 0.001) and a history of bronchial obstruction with an odds ratio of 5.68 (p < 0.001). Identified maternal risk factors were smoking with an odds ratio of 4.13 (CI 1.6-10.7 p < 0.001) and being a teenager with an odds ratio of 4.3 (CI 1.7-11, p < 0.001). Malnutrition, low birth weight, history of previous hospital admissions and having a teenager or smoker mother were considered as independent risk factors using a stepwise analysis.

CONCLUSIONS

Chilean low income children have identifiable risk factors for death at their homes due to pneumonia, that can be preventively managed.

The impact of the Aznalcóllar mine tailing spill on groundwater

As a consequence of a mine tailing dam collapse on the 25th April 1998, more than 4000 ha of the Guadiamar riverflat and farmlands were flooded by 4 hm3 of sulphide slurry. A number of open wells (12 of the 47 analyzed) were also flooded and the water was contaminated. Before the spill, the groundwater in the aquifers was of calcium-carbonate and calcium-sulphate type, with moderate mineralisation and near neutral pH. With the exception of some of the wells close to the mine, this groundwater had a low concentration of the metals associated with the Aznalcóllar mine. After the flood the following metals had anomalous concentrations in well water: Zn, Mn, Pb, Co, Cd and Tl. Of these, Zn seems to be the best tracer of the contamination, owing to its high concentrations. During the 5 months following the spill, water from the unflooded wells did not show an increase in metal concentration. Apart from some exceptions in August, the metal concentration in the affected wells showed a progressive decrease reaching levels closer to those in the wells free from contamination. Nevertheless, in the following dry seasons the draw-down of the water level may lead to exposure and weathering of sulphides in the wells, which could cause an increase in pollution. Therefore, thorough cleaning of all highly contaminated wells is strongly recommended.

[Alcohol drinking in parents and its relation with intellectual score of their children]

Among children living in orphanages of the Metropolitan Region, the paternal alcohol ingestion patterns were investigated. According to abnormal parental alcohol ingestion, a sample of 291 children was studied, of whom 32% were living in simple protection homes for infants with normal intellectual coefficient and 52% in homes for mentally retarded boys. There was a higher frequency and intensity of abnormal alcohol ingestion among parents of infants living in homes for the mentally retarded. Among these, 29% of mothers were illiterate and 11% had incomplete primary school education compared to mothers of simple protection homes in whom the frequency of illiteracy was 10% and of incomplete primary education, 50%. Twenty percent of fathers of children living in homes for the mentally retarded were unemployed, 16% had occasional jobs and 11% had a stable work; these numbers were 11, 30 and 15% respectively for fathers of simple protection homes. Among infants living in homes for the mentally retarded, undernutrition was found in 44%, growth retardation in 51% and microcephaly in 34% compared to 33, 30 and 11% in children living in simple protection homes. Sixteen percent of the sample had fetal alcohol syndrome, 24% among those living in homes for the mentally retarded and 12% in simple protection homes. There was an inverse relationship between offspring intellectual coefficient and the number of drinking parents.

[Course and prognostic value of nutritional parameters in chronic bronchitis]

We studied the nutritional parameters in 82 patients with chronic airways obstruction (type chronic bronchitis). Midarm muscle circumference was the earliest parameter affected. Patients were admitted to the hospital when his serum albumin had a value under normal. On the other hand, the outpatients had a serum albumin within the normal limits. When the protein deficiency involved serum prealbumin and serum retinol binding protein the patients were admitted to intensive care unit (ICU). The body weight and triceps skinfold were within the normal limits even in icu's patients, so that, both parameters neither reflect the nutrition status nor the severity of the undernutrition.