Carbapenem-resistant hypervirulent ST23 Klebsiella pneumoniae with a highly transmissible dual-carbapenemase plasmid in Chile.

BACKGROUND: The convergence of hypervirulence and carbapenem resistance in the bacterial pathogen Klebsiella pneumoniae represents a critical global health concern. Hypervirulent K. pneumoniae (hvKp) strains, frequently from sequence type 23 (ST23) and having a K1 capsule, have been associated with severe community-acquired invasive infections. Although hvKp were initially restricted to Southeast Asia and primarily antibiotic-sensitive, carbapenem-resistant hvKp infections are reported worldwide. Here, within the carbapenemase production Enterobacterales surveillance system headed by the Chilean Public Health Institute, we describe the isolation in Chile of a high-risk ST23 dual-carbapenemase-producing hvKp strain, which carbapenemase genes are encoded in a single conjugative plasmid. RESULTS: Phenotypic and molecular tests of this strain revealed an extensive resistance to at least 15 antibiotic classes and the production of KPC-2 and VIM-1 carbapenemases. Unexpectedly, this isolate lacked hypermucoviscosity, challenging this commonly used hvKp identification criteria. Complete genome sequencing and analysis confirmed the K1 capsular type, the KpVP-1 virulence plasmid, and the GIE492 and ICEKp10 genomic islands carrying virulence factors strongly associated with hvKp. Although this isolate belonged to the globally disseminated hvKp clonal group CG23-I, it is unique, as it formed a clade apart from a previously reported Chilean ST23 hvKp isolate and acquired an IncN KPC-2 plasmid highly disseminated in South America (absent in other hvKp genomes), but now including a class-I integron carrying blaVIM-1 and other resistance genes. Notably, this isolate was able to conjugate the double carbapenemase plasmid to an E. coli recipient, conferring resistance to 1st -5th generation cephalosporins (including combinations with beta-lactamase inhibitors), penicillins, monobactams, and carbapenems. CONCLUSIONS: We reported the isolation in Chile of high-risk carbapenem-resistant hvKp carrying a highly transmissible conjugative plasmid encoding KPC-2 and VIM-1 carbapenemases, conferring resistance to most beta-lactams. Furthermore, the lack of hypermucoviscosity argues against this trait as a reliable hvKp marker. These findings highlight the rapid evolution towards multi-drug resistance of hvKp in Chile and globally, as well as the importance of conjugative plasmids and other mobile genetic elements in this convergence. In this regard, genomic approaches provide valuable support to monitor and obtain essential information on these priority pathogens and mobile elements.

Increased Detection of Carbapenemase-Producing Enterobacterales Bacteria in Latin America and the Caribbean during the COVID-19 Pandemic.

During 2020-2021, countries in Latin America and the Caribbean reported clinical emergence of carbapenemase-producing Enterobacterales that had not been previously characterized locally, increased prevalence of carbapenemases that had previously been detected, and co-production of multiple carbapenemases in some isolates. These increases were likely fueled by changes related to the COVID-19 pandemic, including empirical antibiotic use for potential COVID-19-related bacterial infections and healthcare limitations resulting from the rapid rise in COVID-19 cases. Strengthening antimicrobial resistance surveillance, epidemiologic research, and infection prevention and control programs and antimicrobial stewardship in clinical settings can help prevent emergence and transmission of carbapenemase-producing Enterobacterales.

Multiple Introductions of Salmonella enterica Serovar Typhi H58 with Reduced Fluoroquinolone Susceptibility into Chile.

Salmonella enterica serovar Typhi H58, an antimicrobial-resistant lineage, is globally disseminated but has not been reported in Latin America. Genomic analysis revealed 3 independent introductions of Salmonella Typhi H58 with reduced fluoroquinolone susceptibility into Chile. Our findings highlight the utility of enhanced genomic surveillance for typhoid fever in this region.

Resistance to Ceftriaxone and Azithromycin in Neisseria gonorrhoeae Isolates From 7 Countries of South America and the Caribbean: 2010-2011.

Seven countries in Latin America and the Caribbean report on (2010 and 2011) the susceptibility of 2235 isolates of Neisseria gonorrhoeae to 6 antibiotics. Thirteen isolates had ceftriaxone minimum inhibitory concentrations (MICs) of 0.125 to ≥ 0.25 mg/L. The percentage of resistant isolates to the following antibiotics was: azithromycin, 1.0% to 1.7%; ciprofloxacin, 42.1% to 36.2%; penicillin, 31% to 35%; tetracycline, 21.8% to 22.6%.

Neisseria meningitidis ST-11 clonal complex, Chile 2012.

Serogroup W Neisseria meningitidis was the main cause of invasive meningococcal disease in Chile during 2012. The case-fatality rate for this disease was higher than in previous years. Genotyping of meningococci isolated from case-patients identified the hypervirulent lineage W:P1.5,2:ST-11, which contained allele 22 of the fHbp gene.

[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): comunicación de los primeros cuatro casos pediátricos descritos en Hospital de Niños Roberto del Río.

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 strain was PV-L positive from the clone complex 30. This case series constitutes the first pediatric case report in Chile.

[Laboratory surveillance for invasive meningococcal disease in Chile, 2006-2012]. / Vigilancia de laboratorio de enfermedad meningocóccica invasora en Chile, 2006-2012.

BACKGROUND: Laboratory surveillance of Invasive Meningococcal Disease (IMD) is performed by the Institute of Public Health of Chile. It confirms identification, classifies in serogroups and analyzes the genetic profiles of Neisseria meningitidis isolates from laboratories throughout the country. AIM: To show the results of this surveillance from 2006 to 2012. METHODS: A descriptive data analysis of the confirmed cases of IMD and serological characterization, susceptibility and genetic profiles of the isolates. The analysis was disaggregated by serogroup, age and region. RESULTS: From 2006 to 2012, 486 isolates of N. meningitidis were confirmed. In 2011 a rise in IMD rates was observed due to an increase in W serogroup cases, mainly affecting children aged 5 years or less. Serogroup W became the most prevalent during 2012 (58.3%), replacing the historically prevalent serogroup B. Predominating strains belonged to ST-32 complex/ET-5 complex (40, 4% of strains) and ST-41/44 complex/ Lineage 3 (45, 9% of strains). CONCLUSIONS: Laboratory surveillance has allowed the early detection of increasing IMD caused by serogroup W, which is emergent in Chile. This information has reinforced the daily monitoring of new cases, in collaboration with all the clinical laboratories of the country.

[Laboratory surveillance of Streptococcus pneumoniae from invasive disease, Chile 2007-2012]. / Vigilancia de laboratorio de Streptococcus pneumoniae procedente de enfermedad invasora, Chile 2007-2012.

BACKGROUND: 10-valent pneumococcal vaccine (PCV-10) was introduced in 2011 to the National Immunization Program in Chile. It was administered in 4 doses, but in 2012 it was modified to a 3 dose program. This article shows the results of the Laboratory Surveillance System for Streptococcus pneumoniae isolated of invasive disease from 2007 to 2012 and compares the incidence of invasive pneumococcal disease (IPD) by age groups in the prevaccinal (2007-2010) and postvaccinal period (2012). METHODS: Descriptive study of S. pneumoniae surveillance in invasive diseases cases confirmed at the National Reference Laboratory of the Institute of Public Health of Chile from 2007 to 2012. RESULTS: Global incidence of laboratory confirmed IPD cases decreased 27.8% from 2007 to 2012 and showed a lower risk for IPD in 2012 compared with 2007. Incidence in children aged 1 year or less decreased from 56.1 to 16.3 per 100,000 and from 42.0 to 19.9 per 100,000 in children aged 12 to 23 months in the same period. Highest decreases were observed in IPD cases caused by serotypes 4 (100%), 19F (93.3%), 23F (90.9%), 14 (81.1%), 6B (70%), 18C (58.3%) and 1(81.8%) in children aged 2 years or less. CONCLUSION: Surveillance System detects S.pneumoniae isolated from invasive diseases, contributing with information about laboratory confirmed IPD trends, prevalent serotypes and replacement effects. These results can be used as evidence in healthcare decision making for pneumococcal vaccines.

Antimicrobial resistance, pathogenic potential, and genomic features of carbapenem-resistant Klebsiella pneumoniae isolated in Chile: high-risk ST25 clones and novel mobile elements.

Multidrug- and carbapenem-resistant Klebsiella pneumoniae (CR-Kp) are critical threats to global health and key traffickers of resistance genes to other pathogens. Despite the sustained increase in CR-Kp infections in Chile, few strains have been described at the genomic level, lacking details of their resistance and virulence determinants and the mobile elements mediating their dissemination. In this work, we studied the antimicrobial susceptibility and performed a comparative genomic analysis of 10 CR-Kp isolates from the Chilean surveillance of carbapenem-resistant Enterobacteriaceae. High resistance was observed among the isolates (five ST25, three ST11, one ST45, and one ST505), which harbored 44 plasmids, most carrying genes for conjugation and resistance to several antibiotics and biocides. Ten plasmids encoding carbapenemases were characterized, including novel plasmids or variants with additional resistance genes, a novel genetic environment for blaKPC-2, and plasmids widely disseminated in South America. ST25 K2 isolates belonging to CG10224, a clone traced back to 2012 in Chile, which recently acquired blaNDM-1, blaNDM-7, or blaKPC-2 plasmids stood out as high-risk clones. Moreover, this corresponds to the first report of ST25 and ST45 Kp producing NDM-7 in South America and ST505 CR-Kp producing both NDM-7 and KPC-2 worldwide. Also, we characterized a variety of genomic islands carrying virulence and fitness factors. These results provide baseline knowledge for a detailed understanding of molecular and genetic determinants behind antibiotic resistance and virulence of CR-Kp in Chile and South America. IMPORTANCE In the ongoing antimicrobial resistance crisis, carbapenem-resistant strains of Klebsiella pneumoniae are critical threats to public health. Besides globally disseminated clones, the burden of local problem clones remains substantial. Although genomic analysis is a powerful tool for improving pathogen and antimicrobial resistance surveillance, it is still restricted in low- to middle-income countries, including Chile, causing them to be underrepresented in genomic databases and epidemiology surveys. This study provided the first 10 complete genomes of the Chilean surveillance for carbapenem-resistant K. pneumoniae in healthcare settings, unveiling their resistance and virulence determinants and the mobile genetic elements mediating their dissemination, placed in the South American and global K. pneumoniae epidemiological context. We found ST25 with K2 capsule as an emerging high-risk clone, along with other lineages producing two carbapenemases and several other resistance and virulence genes encoded in novel plasmids and genomic islands.

Standardization and international multicenter validation of a PulseNet pulsed-field gel electrophoresis protocol for subtyping Shigella flexneri isolates.

Shigella flexneri is one of the agents most frequently linked to diarrheal illness in developing countries and often causes outbreaks in settings with poor hygiene or sanitary conditions. Travel is one of the means by which S. flexneri can be imported into developed countries, where this pathogen is not commonly seen. A robust and discriminatory subtyping method is needed for the surveillance of S. flexneri locally and regionally, and to aid in the detection and investigation of outbreaks. The PulseNet International network utilizes standardized pulsed-field gel electrophoresis (PFGE) protocols to carry out laboratory-based surveillance of foodborne pathogens in combination with epidemiologic data. A multicenter validation was carried out in nine PulseNet laboratories located in North and South America, Europe, and Asia, and it demonstrated that a new protocol is highly robust and reproducible for subtyping of S. flexneri. This protocol, already approved for PulseNet laboratories, applies NotI and XbaI as primary and secondary restriction enzymes, respectively, under electrophoresis conditions of initial switch time of 5 s to final switch time of 35 s, at 6 volts/cm.

Whole genome sequence analysis of Salmonella Typhi provides evidence of phylogenetic linkage between cases of typhoid fever in Santiago, Chile in the 1980s and 2010-2016.

Typhoid fever epidemiology was investigated rigorously in Santiago, Chile during the 1980s, when Salmonella enterica serovar Typhi (S. Typhi) caused seasonal, hyperendemic disease. Targeted interventions reduced the annual typhoid incidence rates from 128-220 cases/105 population occurring between 1977-1984 to <8 cases/105 from 1992 onwards. As such, Santiago represents a contemporary example of the epidemiologic transition of an industrialized city from amplified hyperendemic typhoid fever to a period when typhoid is no longer endemic. We used whole genome sequencing (WGS) and phylogenetic analysis to compare the genotypes of S. Typhi cultured from acute cases of typhoid fever occurring in Santiago during the hyperendemic period of the 1980s (n = 74) versus the nonendemic 2010s (n = 80) when typhoid fever was rare. The genotype distribution between "historical" (1980s) isolates and "modern" (2011-2016) isolates was similar, with genotypes 3.5 and 2 comprising the majority of isolations, and 73/80 (91.3%) of modern isolates matching a genotype detected in the 1980s. Additionally, phylogenomically 'ancient' genotypes 1.1 and 1.2.1, uncommon in the global collections, were also detected in both eras, with a notable rise amongst the modern isolates. Thus, genotypes of S. Typhi causing acute illness in the modern nonendemic era match the genotypes circulating during the hyperendemic 1980s. The persistence of historical genotypes may be explained by chronic typhoid carriers originally infected during or before the 1980s.

[Detection of genes associated with drug resistance in Mycobacterium tuberculosis strains isolated in Chile]. / Detección de mutaciones asociadas a cepas multidrogo resistente de Mycobacterium tuberculosis en Chile.

BACKGROUND: The incidence of acquired resistance to antituberculous drugs of Mycobacterium tuberculosis in Chile is approximately 23%. AIM: To analyze the mutations associated with drug resistance in drug resistant strains of Mycobacterium tuberculosis. MATERIAL AND METHODS: In 28 drug resistant Mycobacterium tuberculosis strains isolated in Chile, genes leading to drug resistance were studied. DNA was amplified by polymerase chain reaction (PCR) and sequencing was carried out using the ABI PRISM big dye terminator cycle sequencing ready reaction kit. RESULTS: In rifampicin-resistant strains, the mutations in rpoß gene were in the codons S531W/L (56%), D516Y (16%) and D516V (16%). The predominant mutation in katG gene was in the codon S315L (73%) in isoniazid-resistant strains. The mutation S95T was found in the 71% of ciprofloxacin resistant strains. Only one ethambutol resistant strain had the M306I mutation. Three unreported mutations in katG were identified. CONCLUSIONS: Drug resistance associated mutations of Mycobacterium tuberculosis isolated in Chile were similar to those reported abroad.

[Genetic characterization of the virus causing H1N1 influenza pandemic in Chile: analysis of the first detected cases]. / Inicio del brote de Influenza A (H1N1) pandémica en Chile: caracterización genética de los primeros casos detectados.

BACKGROUND: Following the announcement of the Influenza A(H1N1) pandemic by the World Health Organization in April 2009, a surveillance program was carried out in Chile to detect the introduction of the virus in the country and to monitor its propagation and impact. AIM: To describe the onset of the outbreak and the genetic characterization of the pandemic H1N1 influenza virus in the first detected cases in Chile. MATERIAL AND METHODS: Analysis of18 clinical samples coming from suspicious patients, received in a National Reference Laboratory. RNA reverse transcription and real time influenza gene DNA amplification was carried out in a 7500 Fast and Step One Real Time PCR Systems of Applied Biosystems and MxPro-Mx3000P thermocycler from Stratagene. Super Script III Platinum One-Step Quantitative RT-PCR was used. RESULTS: The virus was first detected in three persons returning from the Dominican Republic via Panamá and a child from the east zone of Santiago. Genetic characterization of the virus showed that the child was infected by a different variant of the pandemic virus than the three persons returning from the Caribbean. CONCLUSIONS: The onset of the Influenza outbreak in Chile apparently carne from two different epidemiological groups. The spread of the virus detected in the voyagers was limited immediately However the virus of the fourth case was found in different regions of Chile.

National Seroprevalence of Coxiella burnetii in Chile, 2016-2017.

Coxiella burnetii is an intracellular bacterium and the cause of the zoonotic infection, Q fever. National surveillance data on C. burnetii seroprevalence is currently not available for any South American country, making efforts of public health to implement strategies to mitigate infections in different at-risk groups within the population extremely challenging. In the current study, we used two commercial anti-C. burnetii immunoassays to screen sera collected from a sample of the Chilean population as part of a 2016-2017 national health survey (n = 5166), nationwide and age-standardized. The seroprevalence for C. burnetii for persons ≥ 15 years was estimated to be 3.0% (95% CI 2.2-4.0), a level similar to national surveys from The Netherlands (2.4%) and USA (3.1%), but lower than Australia (5.6%). A linear increase of C. burnetii seropositivity was associated with an individual's age, with the peak seroprevalence 5.6% (95% CI 3.6-8.6) observed in the ≥65 years' group. C. burnetii seropositivity was significantly higher in the southern macro-zone 6.0% (95% CI 3.3-10.6) compared to metropolitan region 1.8% (95% CI 0.9-3.3), the former region being home to significant livestock industries, particularly dairy farming. These data will be useful to inform targeted strategies for the prevention of Q fever in at-risk populations in Chile.

The direct effect of pneumococcal conjugate vaccines on invasive pneumococcal disease in children in the Latin American and Caribbean region (SIREVA 2006-17): a multicentre, retrospective observational study.

BACKGROUND: Streptococcus pneumoniae isolated from patients with invasive pneumococcal disease has been subjected to laboratory-based surveillance in Latin American and Caribbean countries since 1993. Invasive pneumococcal diseases remain a major cause of death and disability worldwide, particularly in children. We therefore aimed to assess the direct effect of pneumococcal conjugate vaccines (PCVs) on the distribution of pneumococcal serotypes causing invasive pneumococcal disease in children younger than 5 years before and after PCV introduction. METHODS: We did a multicentre, retrospective observational study in eight countries that had introduced PCV (ie, PCV countries) in the Latin American and Caribbean region: Argentina, Brazil, Chile, Colombia, Dominican Republic, Mexico, Paraguay, and Uruguay. Cuba and Venezuela were also included as non-PCV countries. Isolate data for Streptococcus pneumoniae were obtained between 2006 and 2017 from children younger than 5 years with an invasive pneumococcal disease from local laboratories or hospitals. Species' confirmation and capsular serotyping were done by the respective national reference laboratories. Databases from the Sistema Regional de Vacunas (SIREVA) participating countries were managed and cleaned in a unified database using Microsoft Excel 2016 and the program R (version 3.6.1). Analysis involved percentage change in vaccine serotypes between pre-PCV and post-PCV periods and the annual reporting rate of invasive pneumococcal diseases per 100 000 children younger than 5 years, which was used as a population reference to calculate percentage vaccine type reduction. FINDINGS: Between 2006 and 2017, 12 269 isolates of invasive pneumococcal disease were collected from children younger than 5 years in the ten Latin American and Caribbean countries. The ten serotypes included in ten-valent pneumococcal conjugate vaccine (PCV10) decreased significantly (p<0·0001) after any PCV introduction, except for the Dominican Republic. The percentage change for the ten vaccine serotypes in PCV10 countries was -91·6% in Brazil (530 [72·9%] of 727 before, 27 [6·1%] of 441 after); -85·0% in Chile (613 [72·6%] of 844 before, 44 [10·9%] of 404] after); -84·7% in Colombia (231 [63·1%] of 366 before, 34 [9·7%] of 352 after); and -73·8% in Paraguay (127 [77·0%] of 165 before, 22 [20·2%] of 109 after). In the 13-valent pneumococcal conjugate vaccine (PCV13) countries, the percentage change for the 13 vaccine serotypes was -59·6% in Argentina (853 [85·0%] of 1003 before, 149 [34·3%] of 434 after); -16·5% in the Dominican Republic (95 [80·5%] of 118 before, 39 [67·2%] of 58 after); -43·7% in Mexico (202 [73·2%] of 276 before, 63 [41·2%] of 153 after); and -45·9% in Uruguay (138 [80·7%] of 171 before, 38 [43·7%] of 87 after). Annual reporting rates showed a reduction from -82·5% (6·21 before vs 1·09 after per 100 000, 95% CI -61·6 to -92·0) to -94·7% (1·15 vs 0·06 per 100 000, -89·7 to -97·3) for PCV10 countries, and -58·8% (2·98 vs 1·23 per 100 000, -21·4 to -78·4) to -82·9% (7·80 vs 1·33 per 100 000, -76·9 to -87·4) for PCV13 countries. An increase in the amount of non-vaccine types was observed in the eight countries after PCV introduction together with an increase in their percentage in relation to total invasive strains in the post-PCV period. INTERPRETATION: SIREVA laboratory surveillance was able to confirm the effect of PCV vaccine on serotypes causing invasive pneumococcal disease in the eight PCV countries. Improved monitoring of the effect and trends in vaccine type as well as in non-vaccine type isolates is needed, as this information will be relevant for future decisions associated with new PCVs. FUNDING: None. TRANSLATIONS: For the Portuguese and Spanish translations of the abstract see Supplementary Materials section.

[Report of four clinical cases of Hafnia alvei bacteremia in a pediatric cardiac surgery unit]. / Reporte de cuatro casos clínicos de bacteriemia por Hafnia alvei en una unidad cardio-quirúrgica pediátrica.

INTRODUCTION: The gram-negative bacillus Hafnia alvei is the only species of the genus Hafnia, family Enterobacteriaceae. It occasionally behaves as an opportunistic pathogen in humans, causing intestinal and respiratory infection and sepsis. It rarely causes bacteremia, usually of unknown focus. OBJECTIVE: To describe a nosocomial outbreak of four pediatric patients with bacteremia by Hafnia alvei. METHODS: Descriptive study using clinical records of pediatric patients diagnosed with Hafnia alvei bacteremia in a pediatric cardio surgical unit, in October 2008. RESULTS: The attack rate was 4/8 (50%), lethality rate 2/4 (50%) and mortality 2/8 (25%). The microbiological study and pulsed-field gel electrophoresis confirmed the same clonal bacterial strain. DISCUSSION: The source of bacteremia was identified only in two patients and was associated with central venous catheters. The other two cases had no known infectious source. Epidemiological surveillance of emerging agents must be maintained.

Identification of Coxiella burnetii in Tank Raw Cow Milk: First Findings from Chile.

Coxiella burnetii causes Q fever, an important zoonotic disease, and exposure is mainly associated with inhalation of contaminated aerosols. In South America, no systematic studies have been carried out. In Chile, the only official record of Q fever has been an outbreak of occupational context occurring in 1998 with eight confirmed human cases, all workers in the Agriculture and Livestock Service. Recently, in 2017 a Q fever outbreak was reported from dairy farm workers in two regions in southern Chile. This study determined the presence of C. burnetii in bulk tank milk samples from dairy farms obtained during this outbreak. A duplex real time quantitative PCR assay with primers and probes targeting two different gene sequences, IS1111 and com1, was used for diagnosis. C. burnetii was detected in 2 of 105 samples analyzed (2.1%). These results pose a potential public health risk as the milk from these farms was sold to the local human population. This is the first report on detecting C. burnetii in raw tank milk samples in Chile.

Evidence of Q Fever and Rickettsial Disease in Chile.

Q fever and rickettsial diseases occur throughout the world and appear to be emergent zoonoses in Chile. The diagnosis of these diseases is currently uncommon in Chile, as their clinical presentations are non-specific and appropriate diagnostic laboratory assays are of limited availability. During a recent outbreak of undiagnosed human atypical pneumonia, we serologically investigated a series of 357 cases from three regions of southern Chile. The aim was to identify those caused by Coxiella burnetii and/or Rickettsia spp. Serological analysis was performed by ELISA and an immunofluorescence assay (IFA) for acute and convalescence sera of patients. Our results, including data from two international reference laboratories, demonstrate that 71 (20%) of the cases were Q fever, and 44 (15%) were a likely rickettsial infection, although the rickettsial species could not be confirmed by serology. This study is the first report of endemic Q fever and rickettsial disease affecting humans in Chile.

[Genetic characterization of Listeria monocytogenes strains isolated during 2007-2014 in Chile]. / Caracterización genética de cepas de Listeria monocytogenes aisladas durante los años 2007-2014 en Chile.

BACKGROUND: Listeria monocytogenes is a foodborne pathogen that causes listeriosis, a disease that can present as febrile gastroenteritis or as an invasive form that has high mortality rates. So far, the genetic diversity of strains of L. monocytogenes isolated from patients, foods and environmental sources in Chile has been poorly studied. AIM: To characterize genetically L. monocytogenes strains received by the Institute of Public Health of Chile (ISP) between 2007 and 2014. METHODS: We selected 94 strains of L. monocytogenes corresponding to 94 different pulsotypes identified by pulsed field gel electrophoresis (PFGE), DNA was extracted and serotyping was performed by polymerase chain reaction (PCR) and multilocus sequence typing (MLST). RESULTS: The most common serotype was 4b (55.3%), followed by serotypes 1/2a (25.5%), 1/2b (17%) and 1/2c (2.2%). 32 sequence-type (ST) were identified, of which 4 were new, and the predominant ones were ST1 (28.7%) and ST2 (13.8%). All the strains of L. monocytogenes were grouped in Lineages I and II. CONCLUSIONS: A great genetic variability was observed in the strains of L. monocytogenes analyzed, being predominant the ST1 and ST2, both belonging to Lineage I. Our results contribute to know the population structure of this pathogen in Chile and its presence in clinical samples, food and the environment.

Increase of Neisseria meningitidis W:cc11 invasive disease in Chile has no correlation with carriage in adolescents.

Neisseria meningitidis 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 Neisseria meningitidis 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 Neisseria meningitidis 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 Neisseria meningitidis 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.