Microbiological analysis of nontyphoidal Salmonella strains causing distinct syndromes of bacteremia or enteritis in HIV/AIDS patients in San Diego, California

Clinical Characteristics, Antimicrobial Resistance, Virulence Genes and Multi-Locus Sequence Typing of Non-Typhoidal Salmonella Serovar Typhimurium and Enteritidis Strains Isolated from Patients in Chiang Mai, Thailand

Non-typhoidal salmonellosis (NTS) caused by ingesting Salmonella enterica contaminated food or drink remains a major bacterial foodborne disease. Clinical outcomes of NTS range from self-limited gastroenteritis to life-threatening invasive NTS (iNTS). In this study, we isolated Salmonella spp. from the stool and blood of patients hospitalized at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand, between 2016-2021 (a total of 395 cases). Then, serovar Typhimurium and Enteritidis were identified and further characterized by multiplex PCR, and multi-locus sequence typing. Our data show that multidrug resistance (MDR) sequence type 34 (ST34) and ST11 are the predominant sequence types for serovars Typhimurium and Enteritidis, respectively. Most S. Typhimurium ST34 lacks spvB, and most S. Enteritidis ST11 harbor sseI, sodCI, rpoS and spvB genes. NTS can be found in a wide range of ages, and anemia could be a significant factor for S. Typhimurium infection (86.3%). Both S. Typhimurium (6.7%) and S. Enteritidis (25.0%) can cause iNTS in immunocompromised patients. S. Typhimurium conferred MDR phenotype higher than S. Enteritidis with multiple antibiotic resistance indexes of 0.22 and 0.04, respectively. Here, we characterized the important S. Typhimurium, S. Enteritidis, and human clinical factors of NTS within the region.

Refractory Salmonella Prosthetic Valve Endocarditis Complicated by Splenic Infarction and Aortic Pseudoaneurysm in a Patient with Double Prosthetic Valves: A Case Report

Endocarditis is an extremely rare complication of Salmonellosis with an incidence of 0.2–0.4%. It is a destructive and invasive infection that follows a highly complicated course and carries a high mortality rate that exceeds 45%. Multiple predisposing factors for Salmonella endocarditis have been described in the literature, including human immunodeficiency virus infection, congenital heart diseases, and the presence of a prosthetic valve. Herein, we report a case of Salmonella prosthetic valve endocarditis complicated by splenic infarction and aortic pseudoaneurysm presenting as a month-long history of fluctuating fever, chills, and rigors, accompanied by occasional cough and shortness of breath in a 55-year-old female with aortic and mitral valves replacement and multiple comorbidities. She was diagnosed by multiple radiographic studies and successfully treated with the Commando procedure and a long course of IV antibiotics.

Anti-inflammatory Effect of Probiotic Limosilactobacillus reuteri KUB-AC5 Against Salmonella Infection in a Mouse Colitis Model

Acute non-typhoidal salmonellosis (NTS) caused by Salmonella enterica Typhimurium (STM) is among the most prevalent of foodborne diseases. A global rising of antibiotic resistance strains of STM raises an urgent need for alternative methods to control this important pathogen. Major human food animals which harbor STM in their gut are cattle, swine, and poultry. Previous studies showed that the probiotic Limosilactobacillus (Lactobacillus) reuteri KUB-AC5 (AC5) exhibited anti-Salmonella activities in chicken by modulating gut microbiota and the immune response. However, the immunobiotic effect of AC5 in a mammalian host is still not known. Here, we investigated the anti-Salmonella and anti-inflammatory effects of AC5 on STM infection using a mouse colitis model. Three groups of C57BL/6 mice (prophylactic, therapeutic, and combined) were fed with 10⁹ colony-forming units (cfu) AC5 daily for 7, 4, and 11 days, respectively. Then, the mice were challenged with STM compared to the untreated group. By using a specific primer pair, we found that AC5 can transiently colonize mouse gut (colon, cecum, and ileum). Interestingly, AC5 reduced STM gut proliferation and invasion together with attenuated gut inflammation and systemic dissemination in mice. The decreased STM numbers in mouse gut lumen, gut tissues, and spleen possibly came from longer AC5 feeding duration and/or the combinatorial (direct and indirect inhibitory) effect of AC5 on STM. However, AC5 attenuated inflammation (both in the gut and in the spleen) with no difference between these three approaches. This study demonstrated that AC5 confers both direct and indirect inhibitory effects on STM in the inflamed gut.

Pathogenicity of clinical Salmonella enterica serovar Typhimurium isolates from Thailand in a mouse colitis model

Salmonella enterica serovar Typhimurium (S. Typhimurium [STM]) is a leading cause of nontyphoidal salmonellosis (NTS) worldwide. The pathogenesis of NTS has been studied extensively using a streptomycin-pretreated mouse colitis model with the limited numbers of laboratory STM strains. However, the pathogenicity of the clinically isolated STM (STMC) strains endemic in Thailand in mice has not been explored. The aim of this study was to compare the pathogenicity of STMC strains collected from Northern Thailand with the laboratory STM (IR715) in mice. Five STMC isolates were obtained from the stool cultures of patients with acute NTS admitted to Maharaj Nakorn Chiang Mai Hospital in 2016 and 2017. Detection of virulence genes and sequence type (ST) of the strains was performed. Female C57BL/6 mice were pretreated with streptomycin sulfate 1 day prior to oral infection with STM. On Day 4 postinfection, mice were euthanized, and tissues were collected to analyze the bacterial numbers, tissue inflammation, and cecal histopathological score. We found that all five STMC strains are ST34 and conferred the same or reduced pathogenicity compared with that of IR715 in mice. A strain-specific effect of ST34 on mouse gut colonization was also observed. Thailand STM ST34 exhibited a significant attenuated systemic infection in mice possibly due to the lack of spvABC-containing virulence plasmid.

Systems Biology Approaches to Understanding the Human Immune System

Systems biology is an approach to interrogate complex biological systems through large-scale quantification of numerous biomolecules. The immune system involves >1,500 genes/proteins in many interconnected pathways and processes, and a systems-level approach is critical in broadening our understanding of the immune response to vaccination. Changes in molecular pathways can be detected using high-throughput omics datasets (e.g., transcriptomics, proteomics, and metabolomics) by using methods such as pathway enrichment, network analysis, machine learning, etc. Importantly, integration of multiple omic datasets is becoming key to revealing novel biological insights. In this perspective article, we highlight the use of protein-protein interaction (PPI) networks as a multi-omics integration approach to unravel information flow and mechanisms during complex biological events, with a focus on the immune system. This involves a combination of tools, including: InnateDB, a database of curated interactions between genes and protein products involved in the innate immunity; NetworkAnalyst, a visualization and analysis platform for InnateDB interactions; and MetaBridge, a tool to integrate metabolite data into PPI networks. The application of these systems techniques is demonstrated for a variety of biological questions, including: the developmental trajectory of neonates during the first week of life, mechanisms in host-pathogen interaction, disease prognosis, biomarker discovery, and drug discovery and repurposing. Overall, systems biology analyses of omics data have been applied to a variety of immunology-related questions, and here we demonstrate the numerous ways in which PPI network analysis can be a powerful tool in contributing to our understanding of the immune system and the study of vaccines.

Health Considerations for HIV-Infected International Travelers

PURPOSE OF THE REVIEW

International travel continues to steadily increase, including leisure travel, travel to one's country of origin to visit friends and relatives, travel for service work, and business travel. Travelers with HIV may have an increased risk for travel-associated infections. The pre-travel medical consultation is an important means of assessing one's risk for travel-related health issues. The aim of this review is to provide an update on key health considerations for the HIV-infected traveler.

RECENT FINDINGS

Like all travelers, the HIV-infected traveler should adhere to behavioral precautions, including safety measures with food and water consumption, safe sexual practices, and arthropod bite avoidance. HIV is a risk factor for venous thromboembolism and patients should be educated regarding this risk. Most pre-travel vaccines are safe and immunogenic in HIV-infected individuals, though live vaccines should be avoided in patients with low CD4 counts. Malaria chemoprophylaxis is strongly recommended in patients with HIV traveling to endemic areas and no significant interactions exist between the commonly used prophylactic anti-malarial agents and anti-retroviral therapy (ART). Travelers with HIV, particularly those who are not on ART or who have low CD4 cell counts, may have increased risk for tuberculosis, malaria, enteric infections, visceral leishmaniasis, American trypanosomiasis, and endemic mycoses such as histoplasmosis, talaromycosis, and coccidioidomycosis. The immune status of the HIV-infected traveler should be assessed prior to travel along with the duration, itinerary, and activities planned during travel in order to carefully consider individual risk for travel-related health issues.

Current strategy for local- to global-level molecular epidemiological characterisation of global antimicrobial resistance surveillance system pathogens

The prime goal of molecular epidemiology is to identify the origin and evolution of pathogens, which can potentially influence the public health worldwide. Traditional methods provide limited information which is not sufficient for outbreak investigation and studying transmission dynamics. The recent advancement of next-generation sequencing had a major impact on molecular epidemiological studies. Currently, whole-genome sequencing (WGS) has become the gold standard typing method, especially for clinically significant pathogens. Here, we aimed to describe the application of appropriate molecular typing methods for global antimicrobial resistance surveillance system pathogens based on the level of discrimination and epidemiological settings. This shows that sequence-based methods such as multi-locus sequence typing (MLST) are widely used due to cost-effectiveness and database accessibility. However, WGS is the only method of choice for studying Escherichia coli and Shigella spp. WGS is shown to have higher discrimination than other methods in typing Klebsiella pneumoniae, Acinetobacter baumannii and Salmonella spp. due to its changing accessory genome content. For Gram positives such as Streptococcus pneumoniae, WGS would be preferable to understand the evolution of the strains. Similarly, for Staphylococcus aureus, combination of MLST, staphylococcal protein A or SCCmec typing along with WGS could be the choice for epidemiological typing of hospital- and community-acquired strains. This review highlights that combinations of different typing methods should be used to get complete information since no one standalone method is sufficient to study the varying genome diversity.

Selected Topics in Aerobic Bacteriology

Aerobic Gram-positive and Gram-negative bacteria can be important pathogens in the immunocompromised host. These bacteria can be found in many environments, as part of the normal microbiota of the human host and animals, in soil and water, on plants, on fomites in the hospital, and on hospital equipment. This review provides information from relevant studies about what are the most common aerobic bacteria associated with patients who have cancer and/or are being treated for it, or who have other diseases which lead to immunodeficiencies, such as HIV, multiple myeloma, aplastic anemia, chronic diseases, and aging. A discussion of the appropriate laboratory tests needed for diagnosis of aerobic infections and information about antibiotics and susceptibility testing are also included.

Microbiome of HIV-infected people

Consistent interactions between the gut microbiome and adaptive immunity recently led several research groups to evaluate modifications of human gut microbiota composition during HIV infection. Herein we propose to review the shifts reported in infected individuals, as their correlation to disease progression. Though the gut microbiota is consistently altered in HIV individuals, the literature reveals several discrepancies, such as changes in microbial diversity associated with HIV status, taxa modified in infected subjects or influence of ART on gut flora restoration. Similarly, mechanisms involved in interactions between gut bacteria and immunity are to date poorly elucidated, emphasizing the importance of understanding how microbes can promote HIV replication. Further research is needed to propose adjuvant therapeutics dedicated to controlling disease progression through gut microbiome restoration.

Management of severe non-TB bacterial infection in HIV-infected adults

Despite widespread antiretroviral therapy use, severe bacterial infections (SBI) in HIV-infected adults continue to cause significant morbidity and mortality globally. Four main pathogens account for the majority of documented SBI: Streptococcus pneumoniae, non-typhoidal strains of Salmonella enterica, Escherichia coli and Staphylococcus aureus. The epidemiology of SBI is dynamic, both in developing countries where, despite dramatic successes in antiretroviral therapy, coverage is far from complete, and in settings in both resource-poor and resource-rich countries where antiretroviral therapy failure is becoming increasingly common. Throughout the world, this complexity is further compounded by rapidly emerging antimicrobial resistance, making management of SBI very challenging in these vulnerable patients. We review the causes and treatment of SBI in HIV-infected people and discuss future developments in this field.

Epidemiology, Clinical Presentation, Laboratory Diagnosis, Antimicrobial Resistance, and Antimicrobial Management of Invasive Salmonella Infections

Salmonella enterica infections are common causes of bloodstream infection in low-resource areas, where they may be difficult to distinguish from other febrile illnesses and may be associated with a high case fatality ratio. Microbiologic culture of blood or bone marrow remains the mainstay of laboratory diagnosis. Antimicrobial resistance has emerged in Salmonella enterica, initially to the traditional first-line drugs chloramphenicol, ampicillin, and trimethoprim-sulfamethoxazole. Decreased fluoroquinolone susceptibility and then fluoroquinolone resistance have developed in association with chromosomal mutations in the quinolone resistance-determining region of genes encoding DNA gyrase and topoisomerase IV and also by plasmid-mediated resistance mechanisms. Resistance to extended-spectrum cephalosporins has occurred more often in nontyphoidal than in typhoidal Salmonella strains. Azithromycin is effective for the management of uncomplicated typhoid fever and may serve as an alternative oral drug in areas where fluoroquinolone resistance is common. In 2013, CLSI lowered the ciprofloxacin susceptibility breakpoints to account for accumulating clinical, microbiologic, and pharmacokinetic-pharmacodynamic data suggesting that revision was needed for contemporary invasive Salmonella infections. Newly established CLSI guidelines for azithromycin and Salmonella enterica serovar Typhi were published in CLSI document M100 in 2015.

Cardiac sequelae of human immunodeficiency virus disease

Presently, patients with human immunodeficiency virus infection are living longer and are frequently encountered in medical practice. HIV infection is a systemic disease, which affects a wide spectrum of organs. Cardiac involvement is frequent, and the consequent clinical manifestations are a common reason to seek medical advice. In this review, we discuss the different cardiac sequelae of HIV infection.

Molecular characterization showed limited genetic diversity among Salmonella Enteritidis isolated from humans and animals in Malaysia

Salmonella enterica serovar Enteritidis (S. Enteritidis) is the most common causative agent of non-typhoidal salmonellosis in Malaysia. We aimed to characterize S. Enteritidis isolated from humans and animals by analyzing their antimicrobial resistance profiles and genotypes. A total of 111 strains were characterized using multiple-locus variable-number tandem repeat analysis, pulsed-field gel electrophoresis, and antimicrobial susceptibility testing. Both typing methods revealed that genetically similar S. Enteritidis strains had persisted among human and animal populations within the period of study (2003-2008). Only 39% of the strains were multi-drug resistant (i.e., resistant to 3 or more classes of antimicrobial agents), with a majority (73%) of these in low-risk phase (multiple antibiotic resistant index <0.20). Limited genetic diversity among clinical and zoonotic S. Enteritidis suggested that animals are possible sources of human salmonellosis. The degree of multi-drug resistance among the strains was generally low during the study period.