Association of virulence plasmid and antibiotic resistance determinants with chromosomal multilocus genotypes in Mexican Salmonella enterica serovar Typhimurium strains

<p>Abstract</p> <p>Background</p> <p>Bacterial genomes are mosaic structures composed of genes present in every strain of the same species (core genome), and genes present in some but not all strains of a species (accessory genome). The aim of this study was to compare the genetic diversity of core and accessory genes of a <it>Salmonella enterica </it>subspecies <it>enterica </it>serovar Typhimurium (Typhimurium) population isolated from food-animal and human sources in four regions of Mexico. Multilocus sequence typing (MLST) and macrorestriction fingerprints by pulsed-field gel electrophoresis (PFGE) were used to address the core genetic variation, and genes involved in pathogenesis and antibiotic resistance were selected to evaluate the accessory genome.</p> <p>Results</p> <p>We found a low genetic diversity for both housekeeping and accessory genes. Sequence type 19 (ST19) was supported as the founder genotype of STs 213, 302 and 429. We found a temporal pattern in which the derived ST213 is replacing the founder ST19 in the four geographic regions analyzed and a geographic trend in the number of resistance determinants. The distribution of the accessory genes was not random among chromosomal genotypes. We detected strong associations among the different accessory genes and the multilocus chromosomal genotypes (STs). First, the <it>Salmonella </it>virulence plasmid (pSTV) was found mostly in ST19 isolates. Second, the plasmid-borne betalactamase <it>cmy-2 </it>was found only in ST213 isolates. Third, the most abundant integron, IP-1 (<it>dfrA12</it>, <it>orfF </it>and <it>aadA2</it>), was found only in ST213 isolates. Fourth, the <it>Salmonella </it>genomic island (SGI1) was found mainly in a subgroup of ST19 isolates carrying pSTV. The mapping of accessory genes and multilocus genotypes on the dendrogram derived from macrorestiction fingerprints allowed the establishment of genetic subgroups within the population.</p> <p>Conclusion</p> <p>Despite the low levels of genetic diversity of core and accessory genes, the non-random distribution of the accessory genes across chromosomal backgrounds allowed us to discover genetic subgroups within the population. This study provides information about the importance of the accessory genome in generating genetic variability within a bacterial population.</p

Optic neuropathy and congenital glaucoma associated with probable Zika virus infection in Venezuelan patients

Introduction: Although the current Zika virus (ZIKV) epidemic is a major public health concern, most reports have focused on congenital ZIKV syndrome, its most devastating manifestation. Severe ocular complications associated with ZIKV infections and possible pathogenetic factors are rarely described. Here, we describe three Venezuelan patients who developed severe ocular manifestations following ZIKV infections. We also analyse their serological response to ZIKV and dengue virus (DENV). Case presentation: One adult with bilateral optic neuritis, a child of 4 years of age with retrobulbar neuritis [corrected]. and a newborn with bilateral congenital glaucoma had a recent history of an acute exanthematous infection consistent with ZIKV infection. The results of ELISA tests indicated that all patients were seropositive for ZIKV and four DENV serotypes. Conclusion: Patients with ZIKV infection can develop severe ocular complications. Anti-DENV antibodies from previous infections could play a role in the pathogenesis of these complications. Well-designed epidemiological studies are urgently needed to measure the risk of ZIKV ocular complications and confirm whether they are associated with the presence of anti-flaviviral antibodies

Non-congenital severe ocular complications of Zika virus infection

In 2016, during a major Zika virus (ZIKV) outbreak in Maracaibo, Venezuela, a 49-year-old woman and an unrelated 4-year-old boy developed bilateral optic neuritis 2–3 weeks after presenting an acute febrile illness characterized by low-grade fever, rash and myalgia [1]. Both patients presented sudden, painless bilateral loss of vision with no corneal or uveal abnormalities. Fundoscopic examination revealed oedema of the optic nerve and optic disc pallor. Optical coherence tomography confirmed bilateral optic nerve head swelling in the case of the adult, but it was not carried out in the child. Automated perimetry performed in the adult revealed bilateral diffuse visual field loss. Magnetic resonance imaging of the brain in both cases was unremarkable. Both patients were diagnosed with bilateral optic neuritis of possible infectious or parainfectious origin. Differential diagnoses that were considered and subsequently discarded included arteritic and non-arteritic ischaemic optic neuropathy, and brain disorders such as multiple sclerosis and brain tumours. Both patients were seropositive for anti-ZIKV IgG and seronegative for anti-ZIKV IgM. In addition, both patients were positive for anti-dengue virus (DENV) IgG for all four DENV serotypes. Management included intravenous methylprednisolone for 3 days, followed by oral prednisolone for 11 days. Although the patients presented a modest improvement in their vision, they continued to have visual impairment after several months of follow-up [1]

Risk Factors for Fecal Quinolone-Resistant Escherichia coli in Mexican Children

We determined the prevalence of, and risk factors for, fecal quinolone-resistant Escherichia coli (QREC) in 324 children from Yucatan, Mexico. QREC was higher in children with recent Salmonella infection (100%) than in children with diarrhea (61%) or healthy children (54%) (P = 0.007). Multivariate analysis identified recent hospitalization of a family member (P = 0.011, odds ratio [OR] = 5.1) and carriage of Salmonella (P = 0.004, OR = 3.7) as independent risk factors for QREC

Salmonella Typhimurium ST213 is associated with two types of IncA/C plasmids carrying multiple resistance determinants

BACKGROUND: Salmonella Typhimurium ST213 was first detected in the Mexican Typhimurium population in 2001. It is associated with a multi-drug resistance phenotype and a plasmid-borne bla(CMY-2 )gene conferring resistance to extended-spectrum cephalosporins. The objective of the current study was to examine the association between the ST213 genotype and bla(CMY-2 )plasmids. RESULTS: The bla(CMY-2 )gene was carried by an IncA/C plasmid. ST213 strains lacking the bla(CMY-2 )gene carried a different IncA/C plasmid. PCR analysis of seven DNA regions distributed throughout the plasmids showed that these IncA/C plasmids were related, but the presence and absence of DNA stretches produced two divergent types I and II. A class 1 integron (dfrA12, orfF and aadA2) was detected in most of the type I plasmids. Type I contained all the plasmids carrying the bla(CMY-2 )gene and a subset of plasmids lacking bla(CMY-2). Type II included all of the remaining bla(CMY-2)-negative plasmids. A sequence comparison of the seven DNA regions showed that both types were closely related to IncA/C plasmids found in Escherichia, Salmonella, Yersinia, Photobacterium, Vibrio and Aeromonas. Analysis of our Typhimurium strains showed that the region containing the bla(CMY-2 )gene is inserted between traA and traC as a single copy, like in the E. coli plasmid pAR060302. The floR allele was identical to that of Newport pSN254, suggesting a mosaic pattern of ancestry with plasmids from other Salmonella serovars and E. coli. Only one of the tested strains was able to conjugate the IncA/C plasmid at very low frequencies (10(-7 )to 10(-9)). The lack of conjugation ability of our IncA/C plasmids agrees with the clonal dissemination trend suggested by the chromosomal backgrounds and plasmid pattern associations. CONCLUSIONS: The ecological success of the newly emerging Typhimurium ST213 genotype in Mexico may be related to the carriage of IncA/C plasmids. We conclude that types I and II of IncA/C plasmids originated from a common ancestor and that the insertion and deletion of DNA stretches have shaped their evolutionary histories

Integrated Food Chain Surveillance System for Salmonella spp. in Mexico

Few developing countries have foodborne pathogen surveillance systems, and none of these integrates data from humans, food, and animals. We describe the implementation of a 4-state, integrated food chain surveillance system (IFCS) for Salmonella spp. in Mexico. Significant findings were 1) high rates of meat contamination (21.3%–36.4%), 2) high rates of ceftriaxone-resistant S. Typhimurium in chicken, ill humans, and swine (77.3%, 66.3%, and 40.4% of S. Typhimurium T isolates, respectively), and 3) the emergence of ciprofloxacin resistance in S. Heidelberg (10.4%) and S. Typhimurium (1.7%) from swine. A strong association between Salmonella spp. contamination in beef and asymptomatic Salmonella spp. infection was only observed in the state with the lowest poverty level (Pearson r = 0.91, p<0.001). Pulsed-field gel electrophoresis analysis of 311 S. Typhimurium isolates showed 14 clusters with 102 human, retail meat, and food-animal isolates with indistinguishable patterns. An IFCS is technically and economically feasible in developing countries and can effectively identify major public health priorities