Carriage prevalence and genomic epidemiology of Staphylococcus aureus among Native American children and adults in the Southwestern USA.

Native American individuals in the Southwestern USA experience a higher burden of invasive Staphylococcus aureus disease than the general population. However, little is known about S. aureus carriage in these communities. A cross-sectional study was conducted to determine the carriage prevalence, risk factors and genomic epidemiology of S. aureus among Native American children (<5 years, n=121) and adults (≥18 years, n=167) in the Southwestern USA. Short- and long-read sequencing data were generated using Illumina and Oxford Nanopore Technology platforms to produce high-quality hybrid assemblies, and antibiotic-resistance, virulence and pangenome analyses were performed. S. aureus carriage prevalence was 20.7 % among children, 30.2 % among adults 18-64 years and 16.7 % among adults ≥65 years. Risk factors among adults included recent surgery, prior S. aureus infection among household members, and recent use of gyms or locker rooms by household members. No risk factors were identified among children. The bacterial population structure was dominated by clonal complex 1 (CC1) (21.1 %), CC5 (22.2 %) and CC8 (22.2 %). Isolates from children and adults were intermixed throughout the phylogeny. While the S. aureus population was diverse, the carriage prevalence was comparable to that in the general USA population. Genomic and risk-factor data suggest household, community and healthcare transmission are important components of the local epidemiology.

Epidemiology of Anterior Cruciate Ligament Reconstruction Surgery in Italy: A 15-Year Nationwide Registry Study.

There remains little information on the epidemiology of anterior cruciate ligament reconstruction (ACL-R), therefore, we performed an epidemiological evaluation on the ACL-R procedures performed in Italy from 2001 to 2015 to highlight potential disparities in access to healthcare. The National Hospital Discharge records (SDO) maintained at the Italian Ministry of Health were analyzed from 2001 to 2015; 248,234 ACL-Rs were performed in Italy over the 15-year study period in the adult population (starting from 15 years old), and the incidence rate per year in 100,000 persons ranged from 21.70 to 33.60 over the study period. The overall male/female ratio was 4.54. The length of hospitalization ranged from four days in 2001 to two days in 2015. Italy is historically divided into north, center, and south regions, and more than half of ACL-R surgery was performed in the north (67.2%); 95.2% of ACL-Rs were underwent in public institutions. The predicted model projected a slight growth in the number of ACL-Rs in the next 10 years (2016-2025). The number of ACL-R procedures increased in the adult population from 2001 to 2015. The ACL-R procedures were concentrated in the north of Italy, suggesting that efforts on regionalization of ACL-Rs should turn toward improving quality in hospitals in the south of Italy.

Trends of anterior cruciate ligament reconstruction in children and young adolescents in Italy show a constant increase in the last 15 years.

PURPOSE: The aim of this 15-year nationwide study was to investigate the trend in ACL reconstructive surgeries in patients younger than 15 years old in Italy, as well as their social and economic impact. MATERIALS AND METHODS: The National Hospital Discharge records (SDO) collected by the Italian Ministry of Health in the 15-year period between 2001 and 2015 were analyzed. This contains anonymous data including patients' age, gender, ICD-9-CM codes for diagnosis and intervention, census region, region of hospitalization, length of the hospitalization, and public or private reimbursement. RESULTS: 1,350 ACL reconstructions were performed in Italy in the population younger than 15 years old, with an incidence rate ranging from 0.16 to 2.04 procedures per 100,000 age-matched individuals. Similarly, the percentage of surgeries in 0-14 year old patients increased with respect to the total number of ACL reconstruction from 0.13% in 2001 to 0.95% in 2015. The age range 10-14 years is the most involved, accounting for 97.3% of surgeries recorded in the study period. The male:female ratio was 1.05 and most of these procedures were performed in the North of Italy (78.3%). CONCLUSION: ACL reconstructions in patients aged 10-14 years are increasing constantly since 2001, and thus, specific actions aimed to define the best management strategy as well as national educational programs to prepare the future surgeons to this new reality are mandatory in the interest of the public health. LEVEL OF EVIDENCE: Level III.

Correction to: Epidemiology of Achilles tendon surgery in Italy: a nationwide registry study, from 2001 through 2015.

An amendment to this paper has been published and can be accessed via the original article.

Epidemiology of Achilles tendon surgery in Italy: a nationwide registry study, from 2001 through 2015.

BACKGROUND: This study aims (1) to estimate the yearly number of Achilles tendon (AT) surgeries in Italy from 2001 to 2015 based on official hospitalization records; (2) to investigate the eventual presence of geographical variation in equity in access to AT surgery between three macroregions of Italy (North, Center and South); (3) to perform statistical projections of the number of AT procedure volumes and rates based on these data. METHODS: We analysed the National Hospital Discharge records (SDO) maintained at the Italian Ministry of Health for a 15-year period, from 2001 through 2015. These data are anonymous and include the patient's age (evaluated in the class of age), sex, census region, the region of hospitalization, length of the hospitalization, public or private reimbursement and diagnosis. RESULTS: During the 15-year study period, 118,652 AT repair were performed in Italy, whose peak of incidence was in 2010. More than half of AT repairs was performed in the North of Italy (52.1%), while 27.2% was performed in the South of Italy and 20.6% Center of Italy. The projection model predicted a slight growth of 2.65% in 2025 in comparison with 2015. CONCLUSION: The current study provides detailed information about the national population-weighted incidence of AT surgery, distribution and projection. The peak of average age was 35-45 year. The majority of AT procedures was performed in the North of Italy. The projection model predicts a slight growth of AT surgery by 2025. Furthermore, this 15-year nationwide registry study shows that the age of incidence of AT injuries shifted from 30 to 40 to 35-45 years compared to the available literature. The higher prevalence of AT surgery was found in men during the working age. Moreover, a low rate of procedures in pediatric and elder age classes was observed.

The transmission dynamic of Madariaga Virus by bayesian phylogenetic analysis: Molecular surveillance of an emergent pathogen.

Madariaga Virus (MADV) is an emergent Alphavirus of the eastern equine encephalitis virus (EEEV) strain complex causing epizootic epidemics. In this study the genetic diversity and the transmission dynamics of Madariaga virus has been investigated by Bayesian phylogenetics and phylodynamic analysis. A database of 32 sequences of MADV group structural polyprotein were downloaded from GenBank, aligned manually edited by Bioedit Software. ModelTest v. 3.7 was used to select the simplest evolutionary model that adequately fitted the sequence data. Neighbor-joining tree was generated using MEGA7. The phylogenetic signal of the dataset was tested by the likelihood mapping analysis. The Bayesian phylogenetic tree was built using BEAST. Selective pressure analysis revealed one positive selection site. The phylogenetic trees showed two main clusters. In particular, Lineage II showed an epizootic infection in monkeys and Lineage III, including 2 main clusters (IIIa and IIIB), revealing an epizootic infection in humans in Haiti and an epizootic infection in humans in Venezuela during the 2016, respectively. The Bayesian maximum clade credibility tree and the time of the most common recent ancestor estimates, showed that the root of the tree dated back to the year 346 with the probable origin in Brazil. Gene flow analysis revealed viral exchanges between different neighbor countries of South America. In conclusion, Bayesian phylogenetic and phylodynamic represent useful tools to follow the transmission dynamic of emergent pathogens to prevent new epidemics spreading worldwide.

Efficacy of radiofrequency ablation in autonomous functioning thyroid nodules. A systematic review and meta-analysis.

Whether thermal ablation is effective to treat toxic thyroid nodules (TTN) is still unknown. Aim of this review was to achieve more robust evidence on the efficacy of radiofrequency ablation (RFA) in treating TTN in terms of TSH normalization, thyroid scintiscan, and volume reduction rate (VRR). A comprehensive literature search of PubMed/Medline and Scopus was performed in November 2018 to retrieve published studies. Original papers reporting TTN treated by RFA and later followed-up were eligible. Excluded were: articles not within this field, articles with unclear data, overlapping series, case/series reports. Discordances were solved in a final collegial meeting. Information was collected concerning population features, treatment procedure, follow-up, cases with TSH normalization, cases with scintiscan normalization, VRR of nodules. Pooled prevalence of patients with TSH or scintiscan normalization, and pooled VRR over time were calculated. For statistical analysis, the random-effects model was used. Eight articles published between 2008 and 2018 were included. The overall number of AFTN treated by RFA was 205. Five studies used a single session of treatment. The time of follow-up ranged from six to 24 months. The pooled rate of patients with TSH normalization was 57%. The pooled rate of patients with scintigraphically proven optimal response was 60%. The pooled VRR at 1 year was 79%. Baseline nodules volume was associated with the rate of TSH normalization. In conclusion, a moderate efficacy of RFA in treating TTN was found, and this can represent a solid starting point in this field.

Genetic diversity in the env V1-V2 region of proviral quasispecies from long-term controller MHC-typed cynomolgus macaques infected with SHIVSF162P4cy.

Intra-host evolution of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) has been shown by viral RNA analysis in subjects who naturally suppress plasma viremia to low levels, known as controllers. However, little is known about the variability of proviral DNA and the inter-relationships among contained systemic viremia, rate of reservoir reseeding and specific major histocompatibility complex (MHC) genotypes, in controllers. Here, we analysed the proviral DNA quasispecies of the env V1-V2 region, in PBMCs and in anatomical compartments of 13 long-term controller monkeys after 3.2 years of infection with simian/human immunodeficiency virus (SHIV)SF162P4cy. A considerable variation in the genetic diversity of proviral quasispecies was present among animals. Seven monkeys exhibited env V1-V2 proviral populations composed of both clusters of identical ancestral sequences and new variants, whereas the other six monkeys displayed relatively high env V1-V2 genetic diversity with a large proportion of diverse novel sequences. Our results demonstrate that in SHIVSF162P4cy-infected monkeys there exists a disparate pattern of intra-host viral diversity and that reseeding of the proviral reservoir occurs in some animals. Moreover, even though no particular association has been observed between MHC haplotypes and the long-term control of infection, a remarkably similar pattern of intra-host viral diversity and divergence was found within animals carrying the M3 haplotype. This suggests that in animals bearing the same MHC haplotype and infected with the same virus, viral diversity follows a similar pattern with similar outcomes and control of infection.

MALDI-TOF MS Identification and Clustering Applied to Enterobacter Species in Nosocomial Setting.

Enterobacter microorganisms cause important bacterial infections in humans. Recently, carbapenem resistant isolates carrying the blaKPC gene were described and their clonal transmission in different nosocomial outbreaks reported. In this study, the relative numbers of Enterobacter species, their antimicrobial susceptibility along 3 years of observation and the identification ability of the two most common MALDI-TOF platforms were evaluated. A clustering analysis was performed to identify changes in the microbial population within the nosocomial environment. Enterobacter were identified using two platforms (MALDI-TOF Biotyper and VITEK MS). Antimicrobial susceptibility was tested by Vitek2 Compact and MIC50 and MIC90 was evaluated using GraphPad software. Clustering analysis was performed by MALDI-TOF and a dendrogram was built with both platforms and compared. The most frequent species isolated were Enterobacter cloacae and Enterobacter aerogenes with a gradual increase of Enterobacter asburiae in 2017. MALDI-TOF platforms showed a very good sensitivity and specificity except for E. asburiae identification that was reliable only by MALDI-TOF MS Biotyper. An increase of resistance for Enterobacter, confirmed by the isolation of extended spectrum beta-lactamase (ESBL) strains and the emergence of E. cloacae multidrug-resistant (MDR) and carbapenem resistant strains, was observed. A clonal route of transmission involving general surgery and geriatric wards was evidenced as previously described for Klebsiella pneumoniae MDR strains in the same nosocomial setting. These data represent an important source of information about the spreading of Enterobacter in the nosocomial environment.

Multi-drug resistant Pseudomonas aeruginosa nosocomial strains: Molecular epidemiology and evolution.

Pseudomonas aeruginosa causes a wide variety of nosocomial infections. In the study, phylogenetic, selective pressure analysis and homology modelling were applied to oprD efflux pump gene with the aim to characterize multi-drug resistant strains circulating in the nosocomial setting, their transmission dynamics and ongoing evolution. One hundred ninety-three consecutive inpatients with Pseudomonas aeruginosa infection were enrolled at the University Campus Bio-Medico of Rome, between January 2015 and December 2016. oprD gene was sequenced in 20 nosocomial multi-drug resistant P. aeruginosa strains. Phylogeographic, selective pressure, residue conservation analysis and homology modelling were performed. Clinical epidemiological data were extracted from patient medical records. Multi-drug resistant strains accounted for the 36% of total strains and were responsible of 20 cases of nosocomial infections. P. aeruginosa infections occurred prevalently in the West area, especially at the location IIIW and in the Geriatric ward. The time of the most recent common ancestor indicated that strains could have been introduced in the hospital since the end of the year 2009 with the most probable location in general surgery ward. By selective pressure analysis, 29 positions under diversifying selection have been identified and mapped onto the OprD model. Most of the observed residue substitutions are predicted to be destabilizing and some of them occurred in the Loops 2 and 3 that are involved in solute selection and carbapenem susceptibility. The molecular and evolutionary analysis of Multi-drug resistant strains circulating in the nosocomial setting may provide useful insights into the epidemiology and the mechanisms leading to resistance, contributing to infection control improvement.

A case of methicillin-resistant Staphylococcus aureus wound infection: phylogenetic analysis to establish if nosocomial or community acquired.

Methicillin-resistant Staphylococcus aureus (MRSA) infection is rapidly increasing in both hospital and community settings. A 71-year-old man admitted at the Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, with MRSA wound infection consequent to orthopedic surgery was studied and the MRSA transmission evaluated by phylogenetic analysis.

The role of procalcitonin in the diagnosis of bacterial infection after major abdominal surgery: Advantage from daily measurement.

Postsurgical infections represent an important cause of morbidity after abdominal surgery. The microbiological diagnosis is not achieved in at least 30% of culture with consequent worsening of patient outcome. In this study, procalcitonin measurement, during the first 3 days after abdominal surgery, has been evaluated for the early diagnosis of postsurgical infection.Ninety consecutive patients subjected to major abdominal surgery at the University Campus Bio-Medico of Rome, have been included. PCT concentrations were measured by time-resolved amplified cryptate emission (TRACE) assay at admission and at the first, second, and third day after surgery. PCT levels were compared using the Mann-Whitney test and by ANOVA test for variance analysis. Receiver operating characteristic (ROC) analysis was performed to define the diagnostic ability of PCT in case of postsurgical infections.PCT values resulted significantly different between patients developing or not developing postsurgical infections. PCT >1.0 ng/mL at first or second day after surgery and >0.5 ng/mL at third day resulted diagnostic for infectious complication, whereas a value <0.5 ng/mL at the fifth day after surgery was useful for early and safety discharge of patients.In conclusion, PCT daily measurement could represent a useful diagnostic tool improving health care in the postsurgical period following major abdominal surgery and should be recommended.

Procalcitonin and MR-Proadrenomedullin Combination with SOFA and qSOFA Scores for Sepsis Diagnosis and Prognosis: A Diagnostic Algorithm.

PURPOSE: The third Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) defined sepsis as an organ dysfunction consequent to infection. A Sequential Organ Failure Assessment (SOFA) score at least 2 identifies sepsis. In this study, procalcitonin (PCT) and midregional pro-adrenomedullin (MR-proADM) were evaluated along with SOFA and quick SOFA (qSOFA) scores in patients with sepsis or septic shock. METHODS: A total of 109 septic patients and 50 patients with noninfectious disease admitted at the Department of Internal Medicine and General Surgery of the University Hospital Campus Bio-Medico of Rome were enrolled. PCT and MR-proADM were measured with immunoluminometric assays (Brahms, Hennigsdorf, Germany). Data were analyzed with receiver-operating characteristic (ROC) curve analysis, likelihood ratios, and Mann-Whitney U test using MedCalc 11.6.1.0 package. RESULTS: At ROC curve analysis, PCT showed the highest area under the curve and positive likelihood ratio values of 27.42 in sepsis and 43.62 in septic shock. MR-proADM and SOFA score showed a comparable performance. In septic shock, lactate showed the most accurate diagnostic ability. In sepsis, the best combination was PCT with MR-proADM with a posttest probability of 0.988. Based upon these results, an algorithm for sepsis and septic shock diagnosis has been developed. MR-proADM, SOFA, and qSOFA scores significantly discriminated survivors from nonsurvivors. CONCLUSIONS: PCT and MR-proADM test combination represent a good tool in sepsis diagnosis and prognosis suggesting their inclusion in the diagnostic algorithm besides SOFA and qSOFA scores. Furthermore, MR-proADM as marker of organ dysfunction, with a turn around time of about 30 min, has the advantage to be more objective and rapid than SOFA score.

Cytomegalovirus Glycoprotein B Genotype Distribution in Italian Transplant Patients.

BACKGROUND: The cytomegalovirus (CMV) UL55 gene encodes for a glycoprotein implicated in virus pathogenesis. Based on UL55 polymorphism, CMV has been divided into 4 genotypes. Previous studies investigated the possible role of genotypes in the clinical outcome of infection in different categories of patients; however, few data are available, particularly in the transplant setting and Italian case records. METHODS: Phylogenetic analysis through a maximum likelihood tree was used to evaluate the prevalence and distribution of CMV genotypes in whole blood specimens from 47 transplant patients and investigate the relation with demographic and clinical features. RESULTS: Overall, 40.4% of patients were classified as single genotype (12.8% gB1, 23.4% gB2, 4.2% gB3); mixed genotypes were detected in 59.6%. Genotype 4 was detected only in mixed cases. In comparison to single genotypes, mixed genotypes were more frequently associated with a higher duration of DNA viremia and higher peak viral load. CONCLUSIONS: Mixed infections seem to be prevalent in Italian transplant patients; it is likely that mixed infections are more difficult to control by immunological response in comparison to single genotype infections. In this context, the genetic profile of infecting viruses and relation to clinical outcome should be investigated, also taking into account the CMV-specific cellular immune response.

Klebsiella pneumoniae blaKPC-3 nosocomial epidemic: Bayesian and evolutionary analysis.

K. pneumoniae isolates carrying blaKPC-3 gene were collected to perform Bayesian phylogenetic and selective pressure analysis and to apply homology modeling to the KPC-3 protein. A dataset of 44 blakpc-3 gene sequences from clinical isolates of K. pneumoniae was used for Bayesian phylogenetic, selective pressure analysis and homology modeling. The mean evolutionary rate for blakpc-3 gene was 2.67×10-3 substitution/site/year (95% HPD: 3.4×10-4-5.59×10-3). The root of the Bayesian tree dated back to the year 2011 (95% HPD: 2007-2012). Two main clades (I and II) were identified. The population dynamics analysis showed an exponential growth from 2011 to 2013 and the reaching of a plateau. The phylogeographic reconstruction showed that the root of the tree had a probable common ancestor in the general surgery ward. Selective pressure analysis revealed twelve positively selected sites. Structural analysis of KPC-3 protein predicted that the amino acid mutations are destabilizing for the protein and could alter the substrate specificity. Phylogenetic analysis and homology modeling of blaKPC-3 gene could represent a useful tool to follow KPC spread in nosocomial setting and to evidence amino acid substitutions altering the substrate specificity.

Phylogenesys and homology modeling in Zika virus epidemic: food for thought.

Zika virus (ZIKV) is an emerging Flavivirus that have recently caused an outbreak in Brazil and rapid spread in several countries. In this study, the consequences of ZIKV evolution on protein recognition by the host immune system have been analyzed. Evolutionary analysis was combined with homology modeling and T-B cells epitope predictions. Two separate clades, the African one with the Uganda sequence, as the most probable ancestor, and the second one containing all the most recent sequences from the equatorial belt were identified. Brazilian strains clustered all together and closely related to the French Polynesia isolates. A strong presence of a negatively selected site in the envelope gene (Env) protein was evidenced, suggesting a probable purging of deleterious polymorphisms in functionally important genes. Our results show relative conservancy of ZIKV sequences when envelope and other non-structural proteins (NS3 and NS5) are analyzed by homology modeling. However, some regions within the consensus sequence of NS5 protein and to a lesser extent in the envelope protein, show localized high mutation frequency corresponding to a considerable alteration in protein stability. In terms of viral immune escape, envelope protein is under a higher selective pressure than NS5 and NS3 proteins for HLA class I and II molecules. Moreover, envelope mutations that are not strictly related to T-cell immune responses are mostly located on the surface of the protein in putative B-cell epitopes, suggesting an important contribution of B cells in the immune response as well.

Molecular epidemiology, evolution and phylogeny of Chikungunya virus: An updating review.

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus belonging to the Togaviridae family, causing a febrile illness associated with severe arthralgia and rash. In this review, we summarized a series of articles published from 2013 to 2016 concerning CHIKV epidemiology, phylogeny, vaccine and therapies, to give an update of our most recent article written in 2014 (Lo Presti et al.,2014). CHIKV infection was first reported in 1952 from Makonde plateaus and since this time caused many outbreaks worldwide, involving the Indian Ocean region, African countries, American continent and Italy. CHIKV infection is still underestimated and it is normally associated with clinical symptoms overlapping with dengue virus, recurring epidemics and mutations within the viral genome. These characteristics promote the geographical spread and the inability to control vector-mediated transmission of the virus. For these reasons, the majority of studies were aimed to describe outbreaks and to enhance knowledge on CHIKV biology, pathogenesis, infection treatment, and prevention. In this review, 16 studies on CHIKV phylogenetic and phylodinamics were considered, during the years 2013-2016. Phylogenetic and phylodinamic analysis are useful tools to investigate how the genealogy of a pathogen population is influenced by pathogen's demographic history, host immunological milieu and environmental/ecological factors. Phylogenetic tools were revealed important to reconstruct the geographic spread of CHIKV during the epidemics wave and to have information on the circulating strains of the virus, that are important for the prediction and control of the epidemics, as well as for vaccines and antiviral drugs development. In conclusion, this updating review can give a critical appraisal of the epidemiology, therapeutic and phylogenesis of CHIKV, reinforcing the need to monitor the geographic spread of virus and vectors.

Impact of spatial dispersion, evolution, and selection on Ebola Zaire Virus epidemic waves.

Ebola virus Zaire (EBOV) has reemerged in Africa, emphasizing the global importance of this pathogen. Amidst the response to the current epidemic, several gaps in our knowledge of EBOV evolution are evident. Specifically, uncertainty has been raised regarding the potential emergence of more virulent viral variants through amino acid substitutions. Glycoprotein (GP), an essential component of the EBOV genome, is highly variable and a potential site for the occurrence of advantageous mutations. For this study, we reconstructed the evolutionary history of EBOV by analyzing 65 GP sequences from humans and great apes over diverse locations across epidemic waves between 1976 and 2014. We show that, although patterns of spatial dispersion throughout Africa varied, the evolution of the virus has largely been characterized by neutral genetic drift. Therefore, the radical emergence of more transmissible variants is unlikely, a positive finding, which is increasingly important on the verge of vaccine deployment.

Amino acid mutations in Ebola virus glycoprotein of the 2014 epidemic.

Zaire Ebola virus (EBOV) is an enveloped non-segmented negative strand RNA virus of 19 kb in length belonging to the family Filoviridae. The virus was isolated and identified in 1976 during the epidemic of hemorrhagic fever in Zaire. The most recent outbreak of EBOV among humans, was that occurred in the forested areas of south eastern Guinea, that began in February 2014 and is still ongoing. The recent Ebola outbreak, is affecting other countries in West Africa, in addiction to Guinea: Liberia, Nigeria, and Sierra Leone. In this article, a selective pressure analysis and homology modeling based on the G Glycoprotein (GP) sequences retrieved from public databases were used to investigate the genetic diversity and modification of antibody response in the recent outbreak of Ebola Virus. Structural and the evolutionary analysis underline the 2014 epidemic virus being under negative selective pressure does not change with respect to the old epidemic in terms of genome adaptation.

Analysis of the ORFK1 hypervariable regions reveal distinct HHV-8 clustering in Kaposi's sarcoma and non-Kaposi's cases.

BACKGROUND: Classical Kaposi's Sarcoma (cKS) is a rare vascular tumor, which develops in subjects infected with Human Herpesvirus-8 (HHV-8). Beside the host predisposing factors, viral genetic variants might possibly be related to disease development. The aim of this study was to identify HHV-8 variants in patients with cKS or in HHV-8 infected subjects either asymptomatic or with cKS-unrelated cutaneous lymphoproliferative disorders. METHODS: The VR1 and VR2 regions of the ORF K1 sequence were analyzed in samples (peripheral blood and/or lesional tissue) collected between 2000 and 2010 from 27 subjects with HHV-8 infection, established by the presence of anti-HHV-8 antibodies. On the basis of viral genotyping, a phylogenetic analysis and a time-scaled evaluation were performed. RESULTS: Two main clades of HHV-8, corresponding to A and C subtypes, were identified. Moreover, for each subtype, two main clusters were found distinctively associated to cKS or non-cKS subjects. Selective pressure analysis showed twelve sites of the K1 coding gene (VR1 and VR2 regions) under positive selective pressure and one site under negative pressure. CONCLUSION: Thus, present data suggest that HHV-8 genetic variants may influence the susceptibility to cKS in individuals with HHV-8 infection.