Genomic Diversity of Listeria monocytogenes Isolated from Clinical and Non-Clinical Samples in Chile

Listeria monocytogenes is the causative agent of listeriosis, which is an uncommon but severe infection associated with high mortality rates in humans especially in high-risk groups. This bacterium survives a variety of stress conditions (e.g., high osmolality, low pH), which allows it to colonize different niches especially niches found in food processing environments. Additionally, a considerable heterogeneity in pathogenic potential has been observed in different strains. In this study, 38 isolates of L. monocytogenes collected in Chile from clinical samples (n = 22) and non-clinical samples (n = 16) were analyzed using whole genome sequencing (WGS) to determine their genomic diversity. A core genome Single Nucleotide Polymorphism (SNP) tree using 55 additional L. monocytogenes accessions classified the Chilean isolates in lineages I (n = 25) and II (n = 13). In silico, Multi-locus sequence typing (MLST) differentiated the isolates into 13 sequence types (ST) in which the most common were ST1 (15 isolates) and ST9 (6 isolates) and represented 55% of the isolates. Genomic elements associated with virulence (i.e., LIPI-1, LIPI-3, inlA, inlB, inlC, inlG, inlH, inlD, inlE, inlK, inlF, and inlJ) and stress survival (i.e., stress survival islet 1 and stress survival islet 2) were unevenly distributed among clinical and non-clinical isolates. In addition, one novel inlA premature stop codon (PMSC) was detected. Comparative analysis of L. monocytogenes circulating in Chile revealed the presence of globally distributed sequence types along with differences among the isolates analyzed at a genomic level specifically associated with virulence and stress survival

Community associated-methicillin-resistant staphylococcus aureus (SAMR-AC): Comunication of the first four pediatric cases in the roberto del rio children’s hospital Staphylococcus aureus resistente a meticilina asociado a la comunidad (SARM-AC): Comunica

© 2015, Rev Chilena Infectol. All right reserved.Staphylococcus aureus is a known pathogen in pediatric patients that produces skin infections, cutaneous abscess, cellulitis and osteoarticular infections. Most of these infections are produced by a meticilin susceptible strain. The community associated methicillin resistant Staphylococcus aureus was published for the first time in 1993, ever since then is has been recognized as a cosmopolite pathogen. The first report in Latin America was published in 2003, and in Chile in 2008 from adult patients that have reported traveling to other countries. The following series describes four pediatric cases, all school-aged children, diagnosed since 2012 with clinical followups and molecular studies. Two cases presented as osteomyelitis of the lower extremity; and one presented as arm cellulitis. These three cases had Panton Valentine leukocidine (PV-L) negative strains from the clone complex 8. The last case presented a renal abscess, the strai

Increase of <i>Neisseria meningitidis</i> W:cc11 invasive disease in Chile has no correlation with carriage in adolescents

<div><p><i>Neisseria meningitidis</i> is a human exclusive pathogen that can lead to invasive meningococcal disease or may be carried in the upper respiratory tract without symptoms. The relationship between carriage and disease remains poorly understood but it is widely accepted that decreasing carriage by immunization should lead to a reduction of invasive cases. Latin America has experienced an increased incidence of serogroup W invasive cases of <i>Neisseria meningitidis</i> in the last decade. Specifically in Chile, despite low total incidence of invasive cases, serogroup W has become predominant since 2011 and has been associated with elevated mortality. Expecting to gain insight into the epidemiology of this disease, this study has used molecular typing schemes to compare <i>Neisseria meningitidis</i> isolates causing invasive disease with those isolates collected from adolescent carriers during the same period in Chile. A lower carriage of the serogroup W clonal complex ST-11/ET37 than expected was found; whereas, the same clonal complex accounted for 66% of total invasive meningococcal disease cases in the country that year. A high diversity of PorA variable regions and fHbp peptides was also ascertained in the carrier isolates compared to the invasive ones. According to the results shown here, the elevated number of serogroup W invasive cases in our country cannot be explained by a rise of carriage of pathogenic isolates. Overall, this study supports the idea that some strains, as W:cc11 found in Chile, possess an enhanced virulence to invade the host. Notwithstanding hypervirulence, this strain has not caused an epidemic in Chile. Finally, as genetic transfer occurs often, close surveillance of <i>Neisseria meningitidis</i> strains causing disease, and particularly hypervirulent W:cc11, should be kept as a priority in our country, in order to prepare the best response to face genetic changes that could lead to enhanced fitness of this pathogen.</p></div

Distribution of PorA subtypes among NM isolates 2013.

<p>a) PorA profiles from carrier isolates presented as percentages b) PorA profiles from carrier isolates were differentiated by colors within clonal complexes resulting from minimum spanning tree analysis of MLST. c) PorA profiles percentages from IMD isolates. d) PorA profiles from invasive isolates indicated by colors within clonal complexes as in b). (*ND = non-determined). Compare the dominance of P1.5,2,36 subtype among invasive isolates and the diversity among carrier isolates.</p

Distribution of fHbp peptides among NM isolates 2013.

<p>FHbp peptides for all isolates were arranged by modular groups as previously described [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193572#pone.0193572.ref032" target="_blank">32</a>]. Percentages from total are displayed on respective bars. a) fHbp peptides from carrier isolates (N = 184) or b) fHbp peptides from IMD isolates (N = 119). Modular group VI and I predominated among carrier isolates, whereas modular group III did among invasive isolates.</p

Distribution of fHbp peptides within clonal complexes of NM isolates 2013.

<p>fHbp peptides were differentiated by colors within clonal complexes arranged as minimum spanning trees. a) fHbp peptides distribution within carrier isolates (N = 184) b) fHbp peptides distribution within invasive isolates (N = 119).</p

Distribution of NM isolates 2013 by serogroups and clonal complexes.

<p>a) Isolates arranged by serogroup percentages show diversity among carriers whereas serogroups W and B account for almost all IMD isolates <b>(</b>N.G. = non-groupable). b) Isolates arranged by clonal complexes percentages resulting from MLST analysis presented a separation of serogroup B, both carriers and IMD isolates, into cc41/44 and cc32. Most NG isolates belonged to cc198, whereas all serogroup W isolates belonged to cc11. (Total number of samples: Carriers = 184 (9–19 yrs); IMD = 119 (any age)).</p