Aerococcus Urinae Aortic Valve Endocarditis with Kissing Aortic Wall Ulcer: A Case Report and Literature Review.

BACKGROUND Initially presumed as nonpathogenic, the bacterial genus aerococcus now includes 7 distinct virulent and avirulent species. Aerococcus urinae first isolated in 1992 is an uncommon cause of urinary tract infection (UTI) and is seen in only 0.15% to 0.8% of cases. A. urinae associated invasive bacteremia and systemic infection are extremely rare entities. Less than 50 cases of A. urinae associated with infective endocarditis (IE) have been reported in the literature, with the prevalence being 3 per 1 million. CASE REPORT A 59-year-old male presented to our hospital with exertional dyspnea and new-onset atrial flutter. Prior to his current admission patient was treated for A. urinae associated UTI with levofloxacin for 10 days. A transthoracic echocardiogram revealed severe aortic regurgitation with aortic valve endocarditis, which was subsequently confirmed on transesophageal echocardiogram. Blood cultures displayed gram-positive cocci in clusters, ultimately identified as A. urinae. The patient was treated with intravenous vancomycin and underwent surgical aortic valve replacement along with patch repair for underlying aortic wall ulcer. CONCLUSIONS To the best of our knowledge, this is the first-ever reported case of A. urinae associated IE complicated by an aortic wall ulcer. Male gender, age >65 years, and preexisting urinary tract pathology have all been implicated as risk factors for aerococcus infection. A. urinae is almost always sensitive to penicillin, carbapenem, and aminoglycosides.

Clinical Significance of Isolates Known to Be Blood Culture Contaminants in Pediatric Patients.

Background and objectives: The objective of this study was to investigate the clinical significance of isolates from blood stream infection known to be blood culture contaminants in pediatric patients. Materials and Methods: Microbiological reports and medical records of all blood culture tests issued from 2002 to 2012 (n = 76,331) were retrospectively reviewed. Evaluation for potential contaminants were done by reviewing medical records of patients with the following isolates: coagulase-negative Staphylococcus, viridans group Streptococcus, Bacillus, Corynebacterium, Micrococcus, Aerococcus, and Proprionibacterium species. Repeated cultures with same isolates were considered as a single case. Cases were evaluated for their status as a pathogen. Results: Coagulase-negative Staphylococcus had clinical significance in 23.8% of all cases. Its rate of being a true pathogen was particularly high in patients with malignancy (43.7%). Viridans group Streptococcus showed clinical significance in 46.2% of all cases. Its rate of being a true pathogen was similar regardless of the underlying morbidity of the patient. The rate of being a true pathogens for remaining isolates was 27.7% for Bacillus and 19.0% for Corynebacterium species. Conclusions: Coagulase-negative Staphylococcus and viridans group Streptococcus isolates showed high probability of being true pathogens in the pediatric population, especially in patients with underlying malignancy.

Identification of two abundant Aerococcus urinae cell wall-anchored proteins.

Aerococcus urinae is an emerging pathogen that causes urinary tract infections, bacteremia and infective endocarditis. The mechanisms through which A. urinae cause infection are largely unknown. The aims of this study were to describe the surface proteome of A. urinae and to analyse A. urinae genomes in search for genes encoding surface proteins. Two proteins, denoted Aerococcal surface protein (Asp) 1 and 2, were through the use of mass spectrometry based proteomics found to quantitatively dominate the aerococcal surface. The presence of these proteins on the surface was also shown using ELISA with serum from rabbits immunized with the recombinant Asp. These proteins had a signal sequence in the amino-terminal end and a cell wall-sorting region in the carboxy-terminal end, which contained an LPATG-motif, a hydrophobic domain and a positively charged tail. Twenty-three additional A. urinae genomes were sequenced using Illumina HiSeq technology. Six different variants of asp genes were found (denoted asp1-6). All isolates had either one or two of these asp-genes located in a conserved locus, designated Locus encoding Aerococcal Surface Proteins (LASP). The 25 genomes had in median 13 genes encoding LPXTG-proteins (range 6-24). For other Gram-positive bacteria, cell wall-anchored surface proteins with an LPXTG-motif play a key role for virulence. Thus, it will be of great interest to explore the function of the Asp proteins of A. urinae to establish a better understanding of the molecular mechanisms by which A. urinae cause disease.

Adherent/invasive capacities of bovine-associated Aerococcus viridans contribute to pathogenesis of acute mastitis in a murine model.

Aerococcus viridans, a firmicutes bacteria widespread in the environment, is increasingly isolated from humans and animals, especially cows with mastitis. However, its pathogenicity in the bovine mammary gland is unclear. The objective was to explore pathogenic potential of putative virulent and avirulent A. viridans in murine systemic and intramammary infection and mechanistically in cultured bovine mammary epithelial cells (bMECs). Virulence of 9 strains of A. viridans, isolated from subclinical cases of mastitis, was tested for their ability to kill mice when systemically inoculated. Two A. viridans strains, causing highest and lowest survival rate in mice, were selected further as putative avirulent and virulent strains, respectively. Staphylococcus aureus N305 was used as a positive control. After intramammary inoculation, the virulent strain survived and replicated in the murine mammary gland for 9 d, whereas the avirulent strain was eliminated within 3 d. The virulent strain induced a robust inflammatory reaction in the mammary gland, characterized by acute histopathological changes, increased myeloperoxidase activity and higher expression of pro-inflammatory cytokines (TNF-α, IL-6, IL-1ß) compared to the avirulent strain. The virulent strain produced CAMP factor and exhibited strong cytotoxic effects (LDH release) and adhering and invasive abilities in contact with bMECs. Adhesion and invasion of virulent strain to bMECs was further confirmed by scanning and transmission electron microscopy; there was severe damage, including cytomembrane disruption, swollen mitochondria and loss of organelles. In conclusion, the putative virulent strain of A. viridans activated a strong neutrophil-based inflammatory response in the mammary gland, attributed to its ability to adhere to and invade mammary epithelium.

Genomic characterization, phylogenetic analysis, and identification of virulence factors in Aerococcus sanguinicola and Aerococcus urinae strains isolated from infection episodes.

Aerococcus sanguinicola and Aerococcus urinae are emerging pathogens in clinical settings mostly being causative agents of urinary tract infections (UTIs), urogenic sepsis and more seldomly complicated infective endocarditis (IE). Limited knowledge exists concerning the pathogenicity of these two species. Eight clinical A. sanguinicola (isolated from 2009 to 2015) and 40 clinical A. urinae (isolated from 1984 to 2015) strains from episodes of UTIs, bacteremia, and IE were whole-genome sequenced (WGS) to analyze genomic diversity and characterization of virulence genes involved in the bacterial pathogenicity. A. sanguinicola genome sizes were 2.06-2.12 Mb with 47.4-47.6% GC-contents, and 1783-1905 genes were predicted whereof 1170 were core-genes. In case of A. urinae strains, the genome sizes were 1.93-2.44 Mb with 41.6-42.6% GC-contents, and 1708-2256 genes of which 907 were core-genes. Marked differences were observed within A. urinae strains with respect to the average genome sizes, number and sequence identity of core-genes, proteome conservations, phylogenetic analysis, and putative capsular polysaccharide (CPS) loci sequences. Strains of A. sanguinicola showed high degree of homology. Phylogenetic analyses showed the 40 A. urinae strains formed two clusters according to two time periods: 1984-2004 strains and 2010-2015 strains. Genes that were homologs to virulence genes associated with bacterial adhesion and antiphagocytosis were identified by aligning A. sanguinicola and A. urinae pan- and core-genes against Virulence Factors of Bacterial Pathogens (VFDB). Bacterial adherence associated gene homologs were present in genomes of A. sanguinicola (htpB, fbpA, lmb, and ilpA) and A. urinae (htpB, lap, lmb, fbp54, and ilpA). Fifteen and 11-16 CPS gene homologs were identified in genomes of A. sanguinicola and A. urinae strains, respectively. Analysis of these genes identified one type of putative CPS locus within all A. sanguinicola strains. In A. urinae genomes, five different CPS loci types were identified with variations in CPS locus sizes, genetic content, and structural organization. In conclusion, this is the first study dealing with WGS and comparative genomics of clinical A. sanguinicola and A. urinae strains from episodes of UTIs, bacteremia, and IE. Gene homologs associated with antiphagocytosis and bacterial adherence were identified and genetic variability was observed within A. urinae genomes. These findings contribute with important knowledge and basis for future molecular and experimental pathogenicity study of UTIs, bacteremia, and IE causing A. sanguinicola and A. urinae strains.

Acute meningitis of piglets and mice caused by co-infected with Streptococcus suis and Aerococcus viridans.

The two opportunistic pathogens, Streptococcus suis (S. suis) and Aerococcus. viridans (A. viridans) were isolated from the brains of piglets suffered bacterial meningitis in a farm of China. The murine model has been established to evaluate the pathogenicity and symbiotic relationship of S. suis and A. viridans simultaneously infection. Our results demonstrated the ability of new serotype S. suis to cause the classical bacterial meningitis and death were greatly enhanced during co-infection with A. viridans in mice at a proportion. We also examined the distribution and titer of bacteria coinfection in organs, the titer of S. suis appeared a significant trend for an increase in the lung meanwhile the concentration titer of A. viridans maintain a low level. This is the first reported the A. viridans and S. suis coinfection cause the bacterial meningitis outbroke in the piglets and mice. Moreover, further investigation of the pathogenesis of A. viridans and S. suis is urgently needed in swine industry.

Aerococcus viridans var. homari: The presence of capsule and the relationship to virulence in American lobster (Homarus americanus).

The relationship between virulence and encapsulation of Aerococcus viridans var. homari was evaluated by growing virulent (Rabin's) and avirulent (ATCC 10400) strains under varying culture conditions, and during challenge trials. Changes in capsule thickness were monitored using a modified lysine-ruthenium red (LRR) fixation method and transmission electron microscopy. The virulent Rabin's strain possessed a prominent capsule of 0.252 µm±0.061 µm that was diminished by in vitro growth conditions to 0.206 µm±0.076 µm. The ATCC 10400 strain capsule thickness decreased from 0.157 µm±0.043 µm to 0.117 µm±0.043 µm after 10 in vitro passages. The virulent Rabin's strain capsule was significantly thicker than the avirulent ATCC 10400 strain under all growth conditions. Rabin's strain, regardless of pre-challenge growth conditions or dose (high dose 10(7) or low dose 10(2)), was able to kill lobsters in 7 days at 15°C. ATCC 10400 strain, regardless of pre-challenge growth conditions, killed lobster only at high doses (10(7)) with varying median time to death of ∼15 days, while at low doses (10(2)) all lobsters survived and no bacteria were present after 42 days. This work demonstrates the importance of the thickness of the A. viridans capsule to virulence in the American lobster.

Aerococcus: an increasingly acknowledged human pathogen.

Aerococci have often been misidentified as streptococci in microbiology laboratories, leading to an underestimation of these bacteria as causes of human infections. An increased awareness of aerococci and the introduction of matrix-assisted laser desorption ionization time-of-flight mass spectrometry, has led to an increased isolation of Aerococcus urinae and Aerococcus sanguinicola from human urine and blood. The two species are found in human urine and can cause urinary tract infections (UTI). Aerococcus urinae can, in older males with underlying urinary tract conditions, cause invasive infections such as urosepsis or infective endocarditis. The prognosis of invasive aerococcal infections appears to be relatively favourable despite the old age of patients and their many comorbidities. Though clinical breakpoints are still not in place, aerococci seem to be sensitive to penicillins, carbapenems and vancomycin. There is synergy between penicillin and aminoglycosides against some A. urinae isolates and this combination is often used in aerococcal infective endocarditis. The treatment of complicated aerococcal UTI is not obvious as many isolates are resistant to fluoroquinolones. In addition, A. urinae is resistant to sulphamethoxazole, and there are methodological problems in the determination of trimethoprim sensitivity. In complicated UTI, ampicillin is probably a safe treatment option, whereas nitrofurantoin is probably effective in uncomplicated UTI. Treatment studies in aerococcal infections are needed as is a better understanding of the natural niches for aerococci and the pathogenesis and clinical course of aerococcal infections.

Differential expression of American lobster (Homarus americanus) immune related genes during infection of Aerococcus viridans var. homari, the causative agent of Gaffkemia.

This is the first transcriptomic study focusing on immunity in the commercially valuable American lobster (Homarus americanus). We have conducted an in vivo infection trial using the Gram-positive bacterium Aerococcus viridans var. homari to determine how H. americanus responds to this naturally occurring lethal-pathogen. A novel H. americanus microarray was used to measure the transcriptomic changes occurring in over 14,000 genes in the lobster hepatopancreas. Hundreds of new immune genes and isoforms were identified and measured for the first time in this species, and our findings highlight 148 genes of interest involved in H. americanus pathogen response. We verified our microarray results using RT-qPCR on three anti-lipopolysaccharide (ALFHa-1, ALFHa-2, ALFHa-4), a thioredoxin, acute phase serum amyloid protein A, hexokinase and two trypsin genes. RT-qPCR and microarray findings show close agreement and highlight the significant increase in gene expression in many lobster immune genes during A. viridans infection. Differential expression of the ALFHa isoforms may indicate that the H. americanus immune response can be tailored to the class of pathogen causing disease.

Aerococcus viridans expression of Cpn60 is associated with virulence during infection of the American lobster, Homarus americanus Milne Edwards.

The Gram-positive bacterium Aerococcus viridans var. homari is a well-documented causative agent of the lethal systemic disease gaffkemia in both the American lobster, Homarus americanus, and the European lobster, Homarus gammarus. Previous phenotypic characterization has been unsuccessful at differentiating avirulent from virulent strains without performing lethal animal infection trials. Recent genetic characterization of A. viridans strains through 16S rRNA sequencing and random amplification of polymorphic DNA fingerprinting has revealed the presence of two subtypes. However, subtype 1 contains both virulent and avirulent strains which are genetically identical. The purpose of this study was to determine the proteomic mediators of virulence in A. viridans. Quantitative proteomic mapping of these two strains has revealed 29 differentially expressed protein spots, seven of which are only expressed in the virulent strain and could act as virulence factors. One protein, chaperonin 60 (Cpn60), is uniquely expressed in the virulent strain and has been shown to act as a virulence factor in many other bacteria. The proteomic mapping strategy employed in this study is the first to show phenotypic differences between virulent and avirulent strains. Cpn60 expression represents a potentially useful tool for identifying the virulent strains of A. viridans in epidemiological studies.

Diseases of American lobsters (Homarus americanus): a review.

The American lobster fishery is a significant economic driver in coastal communities of North America. Increasingly, the impacts of infectious disease are recognized as important components and factors in the population ecology and subsequent management of the lobster fishery. Both environmental and anthropogenic factors impact marine diseases. The review herein highlights aspects of several important bacterial, fungal and protistan diseases, including gaffkemia, shell disease, vibriosis, disease caused by species of Lagenidium, Haliphthoros and Fusarium, paramoebiasis and Bumper Car disease. As the global environment continues to change, these diseases could more severely affect both wild caught and impounded lobsters.

Platelet activation and biofilm formation by Aerococcus urinae, an endocarditis-causing pathogen.

The Gram-positive bacterium Aerococcus urinae can cause infectious endocarditis (IE) in older persons. Biofilm formation and platelet aggregation are believed to contribute to bacterial virulence in IE. Five A. urinae isolates from human blood were shown to form biofilms in vitro, and biofilm formation was enhanced by the presence of human plasma. Four of the A. urinae isolates caused platelet aggregation in platelet-rich plasma from healthy donors. The Au3 isolate, which induced platelet aggregation in all donors, also activated platelets, as determined by flow cytometry. Platelet aggregation was dependent on bacterial protein structures and on platelet activation since it was sensitive to both trypsin and prostaglandin E(1). Plasma proteins at the bacterial surface were needed for platelet aggregation; and roles of the complement system, fibrinogen, and immunoglobulin G were demonstrated. Complement-depleted serum was unable to support platelet aggregation by Au3 and complement blockade using compstatin-inhibited platelet activation. Platelet activation by Au3 was inhibited by blocking of the platelet fibrinogen receptor, and this isolate was also shown to bind to radiolabeled fibrinogen. Removal of IgG from platelet-rich plasma by a specific protease inhibited the platelet aggregation induced by A. urinae, and blockade of the platelet FcRγIIa hindered platelet activation induced by Au3. Convalescent-phase serum from a patient with A. urinae IE transferred the ability of the bacterium to aggregate platelets in an otherwise nonresponsive donor. Our results show that A. urinae exhibits virulence strategies of importance for IE.

Expression of antimicrobial peptides from Hyas araneus haemocytes following bacterial challenge in vitro.

Circulating haemocytes play major roles in the host defense reactions of decapods, including the synthesis and release of antimicrobial peptides (AMPs). Unlike the AMPs from insects, those in decapods are constitutively expressed. This study aims to establish primary cell cultures of the three main haemocyte types in Hyas araneus haemocytes, and to measure the in vitro expression of AMP genes in the cells following microbial challenge. The haemocyte populations were separated on Percoll gradients and cultured in modified L-15 medium. Expression analysis by real-time RT-PCR showed that the granular cells are the main producers of crustin, hyastatin and arasin 1 AMPs, but the hyaline cells and semigranular cells also show some expression of these genes. Incubating the cell populations with Aerococcus viridans var. homari (a Gram-positive bacterium) or Listonella anguillarum (a Gram-negative pathogen) provoked no dramatic changes in the gene expression of any of the AMP, and although there was a small (single doubling) significant increase in expression of the crustin gene in granular cells 24h after exposure to L. anguillarum, it is unclear if this is biologically relevant under in vitro conditions. The results presented in this study are in accordance with several in vivo studies.

Aerococcus viridans urinary tract infection in a pediatric patient with secondary pseudohypoaldosteronism.

Aerococcus viridans is a catalase-negative gram-positive bacterium rarely found as human pathogen. Some cases of urinary tract infection (UTI) have been described in immunocompromised adults. In this article we describe a UTI case caused by this agent in a child with severe obstructive uropathy, clinically presented with secondary pseudohypoaldosteronism (SPHA). Although A. viridans is rarely associated with child infection, it can be responsible for life threatening conditions/ situations. To our knowledge, A. viridans UTI has never been reported in pediatric patients.