Corrigendum: Transduction as a Potential Dissemination Mechanism of a Clonal qnrB19-Carrying Plasmid Isolated From Salmonella of Multiple Serotypes and Isolation Sources

[This corrects the article DOI: 10.3389/fmicb.2019.02503.].

Transduction as a Potential Dissemination Mechanism of a Clonal qnrB19-Carrying Plasmid Isolated From Salmonella of Multiple Serotypes and Isolation Sources

Antimicrobial resistance is an increasing problem worldwide, and Salmonella spp. resistance to quinolone was classified by WHO in the high priority list. Recent studies in Europe and in the US reported the presence of small plasmids carrying quinolone resistance in Enterobacteriaceae isolated from poultry and poultry products. The aims of this study were to identify and characterize plasmid-mediated quinolone resistance in Salmonella spp. and to investigate transduction as a possible mechanism associated to its dissemination. First, we assessed resistance to nalidixic acid and/or ciprofloxacin in 64 Salmonella spp. and detected resistance in eight of them. Genomic analyses determined that six isolates of different serotypes and sources carried an identical 2.7-kb plasmid containing the gene qnrB19 which confers quinolone resistance. The plasmid detected also has high identity with plasmids reported in the US, Europe, and South America. The presence of similar plasmids was later surveyed by PCR in a local Salmonella collection (n = 113) obtained from diverse sources: food (eggs), wild and domestic animals (pigs, horse, chicken), and human clinical cases. qnrB19-carrying plasmids were found in 8/113 Salmonella tested strains. A bioinformatics analysis including Chilean and previously described plasmids revealed over 95.0% of nucleotide identity among all the sequences obtained in this study. Furthermore, we found that a qnrB19-carrying plasmid can be transferred between Salmonella of different serotypes through a P22-mediated transduction. Altogether our results demonstrate that plasmid-mediated quinolone resistance (PMQR) is widespread in Salmonella enterica of different serotypes isolated from human clinical samples, wild and domestic animals, and food in Chile and suggest that transduction could be a plausible mechanism for its dissemination. The occurrence of these antimicrobial resistance elements in Salmonella in a widespread area is of public health and food safety concern, and it indicates the need for increased surveillance for the presence of these plasmids in Salmonella strains and to assess their actual impact in the rise and spread of quinolone resistance.

Association between aminolevulinate dehydrase genotypes and blood lead levels in children from a lead-contaminated area in Antofagasta, Chile

Childhood environmental lead exposure in the city of Antofagasta, Chile, was generated by the accumulation of recently removed lead stores derived from mining activities for a long period of time. Susceptibility to harmful lead effects may be associated with polymorphisms of delta-aminolevulinic acid dehydratase (ALAD) because of the differential binding of lead to the codified proteins. We assessed the associations and possible interactions among the following variables: blood lead levels, ALAD genotypes, and distance to the source of lead contamination in Chilean children exposed to lead contamination in Antofagasta, Chile. Ninety-three children were recruited from schools located near a lead- contaminated area. Lead blood levels were measured by atomic absorption spectrophotometry. ALAD genotypes were determined by polymerase chain reaction and restriction fragment-length polymorphism analysis. The frequency of the ALAD-2 allele was estimated at 0.054. Children with the ALAD-2 genotype had higher blood lead levels than noncarriers (p = 0.06). As expected, blood lead levels were inversely correlated with the distance from lead stores. Interestingly, ALAD-2 carriers were more frequent within the area defined by a distance of 200 m from lead deposits (27%) than in areas >200 m (5%) away. Children living within a maximum distance of 200 m from the lead stores showed higher blood lead levels in ALAD-2 carriers (geometric mean = 16.4 microg/dl, range 6 to 27) than in noncarriers (geometric mean = 12.1 microg/dl, range 0 to 26) without achieving statistical significance (p = 0.13). A trend for higher blood lead levels in ALAD-2 carriers compared with ALAD-1 homozygous children has been observed. Because ALAD-2 frequency was higher in subjects living within 200 m from the lead deposits, we hypothesized that a long-term selective pressure against the presence of the ALAD-1 allele is the cause of the overrepresentation of the ALAD-2 allele in children living in proximity to the recently removed lead stores.

[Severe exposure to environmental lead in a child population in Antofagasta, Chile]

BACKGROUND

In Antofagasta, Chile, lead is gathered in bulk in urban zones, contaminating surrounding schools and houses.

AIM

To verify if the environmental lead exposure results in high blood lead levels in children living near lead storage sites.

MATERIAL AND METHODS

Four hundred eighty-six children under 7 years old, living near lead storage sites and 75 children living far away form these sites, were studied. An inquiry was applied and venous blood was drawn. Air, soil and water lead concentrations were also measured.

RESULTS

Lead geometric mean concentrations in exposed children were 8.7 micrograms/dL and 4.22 micrograms/dL in unexposed children. Forty seven percent of exposed children and no unexposed children had lead levels over 10 micrograms/dL. The distance of dwellings from lead storage sites, their geographic location and their antiquity were significantly associated with high blood lead levels. Multivariate models disclosed that people living in contaminated sites have an odds ratio of 24.9 for high blood lead levels.

CONCLUSIONS

Environmental lead contamination is significantly associated with high blood lead levels.

Protein kinase C-mediated phosphorylation of the human multidrug resistance P-glycoprotein regulates cell volume-activated chloride channels

The multidrug resistance P-glycoprotein (P-gp), which transports hydrophobic drugs out of cells, is also associated with volume-activated chloride currents. It is not yet clear whether P-gp is a channel itself, or whether it is a channel regulator. Activation of chloride currents by hypotonicity in cells expressing P-gp was shown to be regulated by protein kinase C (PKC). HeLa cells exhibited volume-activated chloride currents indistinguishable from those obtained in P-gp-expressing cells except that they were insensitive to PKC. HeLa cells did not express detectable P-gp but, following transient transfection with cDNA encoding P-gp, the volume-activated channels acquired PKC regulation. PKC regulation was abolished when serine/threonine residues in the consensus phosphorylation sites of the linker region of P-gp were replaced with alanine. Replacement of these residues with glutamate, in order to mimic the charge of the phosphorylated protein, also mimicked the effects of PKC on channel activation. These data demonstrate that PKC-mediated phosphorylation of P-gp regulates the activity of an endogenous chloride channel and thus indicate that P-gp is a channel regulator.