Aerococcus urinae and trimethoprim-sulfamethoxazole

Aerococcus urinae has been described as resistant to trimethoprim-sulfamethoxazole (SXT), but the test medium may affect this observation. Twenty-seven clinical isolates of A. urinae tested susceptible to SXT in cation-adjusted Mueller-Hinton broth (CAMHB) plus lysed horse blood and resistant in CAMHB plus lysed sheep blood.     

Aerococcus urinae in urinary tract infections

Aerococcus urinae is a rarely reported pathogen, possibly due to difficulties in the identification of the organism. A. urinae is a gram-positive coccus that grows in pairs and clusters, produces alpha-hemolysis on blood agar, and is negative for catalase and pyrrolidonyl aminopeptidase. Some of these characteristics and its being absent from the databases of most commercial identification systems could allow A. urinae to be misidentified as a streptococcus, enterococcus, or staphylococcus. We report two cases of urinary tract infection (UTI) caused by A. urinae and characterize these isolates by morphology, biochemical testing, whole-cell fatty acid analysis, 16S rRNA gene sequencing, and antibiotic susceptibilities. Most patients infected with A. urinae are elderly males with predisposing conditions who present initially with UTI. Because A. urinae is resistant to sulfonamides, treatment could be inappropriate, with infections resulting in serious complications, including death. It is important for the clinician and the microbiologist to consider A. urinae a potential pathogen and proceed with thorough microbiological identification.     

In Vitro Antimicrobial Susceptibility of Aerococcus urinae

Aerococcus urinae may cause urinary tract infections, bacteremia, and endocarditis. No standardized susceptibility test methods or interpretive criteria have been proposed for this organism. This study reports the MIC results for 128 A. urinae isolates tested by broth microdilution. The isolates had low MICs to amoxicillin, cefotaxime, ceftriaxone, doxycycline, linezolid, meropenem, penicillin, rifampin, tetracycline, trimethoprim-sulfamethoxazole, and vancomycin. However, 55% of the isolates had MICs to clindamycin of >0.25 μg/ml, 44% had MICs to erythromycin of >0.25 μg/ml, and 16% had MICs to levofloxacin of >2 μg/ml.     

Identification of Aerococcus urinae in urine samples

To evaluate procedures for the identification of Aerococcus urinae , we examined 24 α-hemolytic non-enterococcal bacterial isolates from 4373 urine samples. Published procedures were compared with 16s rRNA sequencing and biochemical profiling (BBL-Crystal-GP). 16s rRNA sequencing and BBL-Crystal-GP identified the same 13 isolates as A. urinae . Published tests failed to distinguish the 13 A. urinae isolates from eight non- A. urinae isolates; several tests exhibited no discrimination. Ciprofloxacin and trimethoprim susceptibility and growth at 45 °C improved discrimination. For urinary isolates, standard procedures for identification of A. urinae are redundant and insufficiently discriminatory, and may need revision. BBL-Crystal-GP is an accurate alternative.     

Urosepsis with Actinobaculum schaalii and Aerococcus urinae

Actinobaculum was isolated from urine only after prolonged incubation in 5% CO(2) after discrepancy between urine Gram stain and initial culture results was observed. Additional patients were diagnosed using this method. The prevalence of Actinobaculum species in urinary tract infections is underestimated since it is not isolated by routine urine culture procedures.     

Aerococcus urinae: polyphasic characterization of the species

A polyphasic characterization of Aerococcus urinae is presented. In this study the intraspecies relationships between 26 strains of varying geographical origin were examined by phenotypic tests, ribotyping and multilocus enzyme electrophoresis. The results demonstrated two main phenotypic patterns that could be distinguished in tests for hydrolysis of aesculin, and acid production from amygdalin and salicin. Strains were either negative (n=19) or positive (n=6) in these tests. One strain had a deviating pattern. Heterogeneity within the 19 pattern I strains was demonstrated especially by phenotypic tests (acid production from ribose, mannitol, sorbitol, sucrose and D-arabitol) and by multilocus enzyme electrophoresis. However, DNA sequence analysis of the 16S rRNA (n=7) and gyrB genes (n=3) from strains representing the two main patterns showed no variation in sequences among strains. Comparison of A. urinae and representatives of related taxa by 16S rDNA sequence analysis showed that the taxon is related to, but distinct from, other Aerococcus spp.     

Clinical and microbiological features of bacteraemia with Aerococcus urinae

Aerococcus urinae is a Gram-positive bacterium that can cause invasive infection, including infectious endocarditis (IE), mainly in older men. A. urinae is often misclassified in routine diagnostic laboratories. Through searches in the laboratory databases we identify 16 isolates of A. urinae causing bacteraemia during a 6-year period in southern Sweden, indicating that bacteraemia with A. urinae occurs in at least three cases per million inhabitants per year. The identity of isolates was confirmed by sequencing of the 16S rRNA genes and antibiotic susceptibility testing identified two ciprofloxacin-resistant isolates. A. urinae was the only significant pathogen isolated in all cases. Fifteen of the 16 patients were male, 15/16 were more than 70 years old, and 12/16 had underlying urological conditions. Though a urinary tract focus was suspected in the majority of cases, the bacterium was rarely found in urinary samples. Nine patients fulfilled the criteria for severe sepsis and an additional four fulfilled the criteria for sepsis. Only one fatality was recorded. Patients were treated mainly with beta-lactam antibiotics but fluoroquinolones and clindamycin were also used. Three cases of IE were diagnosed and these were complicated by spondylodiscitis in one case and by septic embolization to the brain in one case. An increased awareness of A. urinae is crucial to establishing its role as an important pathogen in older men with urinary tract disease.     

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 E₁. 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.Aerococcus urinae is a Gram-positive coccus with the capacity to cause urinary tract infections (7), infectious endocarditis (IE) (6), and spondylodiscitis (3). A. urinae was recognized as a distinct species in 1992 (1) and can be misreported as an alpha-hemolytic streptococcus due to its growth characteristics and hemolysis pattern. Correct classification is based on sequencing of the 16S rRNA gene. The bacterium is generally susceptible to penicillin, vancomycin, and cephalosporins, whereas it is resistant to sulfonamide (8, 28). Patients who present with severe infection are typically elderly men with underlying urinary tract abnormalities. Twenty cases of A. urinae IE have been described in the literature, and the case fatality rate is about 50% (10, 15). Despite reports of invasive disease caused by A. urinae, including IE, nothing is known about the potential virulence strategies of the bacterium.Biofilm formation is believed to contribute to the ability of a bacterium to colonize foreign materials, such as urinary tract catheters. In the biofilm, the bacteria are protected against host defenses and against antibiotics. The first step in the pathogenesis of IE is believed to be bacterial adherence to damaged heart valves. This is followed by bacterial accumulation and probably also formation of a bacterial biofilm (9). In addition, fibrin, neutrophils, and platelets are deposited on the infected heart valve, leading to the formation of a typical IE vegetation.The majority of Gram-positive pathogens that cause IE interact with and activate human platelets, and this has been proposed to contribute to virulence. The molecular mechanisms leading to platelet activation have been described in detail for many pathogens (recently reviewed in references 11 and 16). Many pathogens activate platelets through bacterial bound fibrinogen in combination with specific immunoglobulin G (IgG) bound to the bacterial surface. This mechanism has been described for Staphylococcus aureus ClfA (19) and fibronectin-binding proteins (12), Streptococcus pyogenes (27), and Streptococcus agalactiae (23). Direct interactions between bacteria and platelets can also lead to platelet activation (5, 17, 21). In addition, Streptococcus sanguis, S. aureus, and Enterococcus faecalis can activate platelets in the absence of bacterial bound fibrinogen through an IgG- and sometimes complement-dependent mechanism with a longer lag time (13, 19, 20, 24). Upon activation, platelets release antibacterial peptides, and resistance to such substances has been linked to the capacity of S. aureus to cause IE (4, 32). Thus, platelet activation may, on the one hand, contribute to host defense against invading bacteria and, on the other hand, contribute to the pathogenesis of IE (31).Given the potential importance of biofilm formation and platelet activation in the pathogenesis of IE and the ability of A. urinae to cause this condition, we investigated the capacity of the bacteria to form biofilms and to activate human platelets.     

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.     

Aerococcus urinae: Severe and Fatal Bloodstream Infections and Endocarditis

Aerococcus urinae is a pathogen that rarely causes severe or fatal infections. We describe four cases of severe A. urinae bloodstream infections. All patients had underlying urologic conditions. Urine cultures, however, were negative.     

Two Cases of Urinary Tract Infection Caused by Propionimicrobium lymphophilum

The first case reports involving Propionimicrobium lymphophilum, a rarely encountered anaerobic Gram-positive non-spore-forming rod, are presented here as urinary tract infections. Initial detection of these bacteria required urine Gram stains. Comparison of the type strain to the two isolates by various methods is depicted and includes antimicrobial susceptibility data.     

Nosocomial Outbreak of Serious Canine Infectious Tracheobronchitis (Kennel Cough) Caused by Canine Herpesvirus Infection

Canine herpesvirus (CHV; Canid herpesvirus 1) is principally a perinatal pathogen of pregnant bitches and newborn pups and secondarily a respiratory tract pathogen of older pups and dogs. Infectious disease of the canine respiratory tract frequently occurs among dogs in groups, in which it is called “ infectious tracheobronchitis” (ITB). Mortality from ITB is generally negligible, and the clinical importance of CHV as an ITB pathogen is considered to be low. The present report describes a novel ITB outbreak accompanied by death among aged dogs in an animal medical center. Most inpatient dogs had received medications that could induce immunosuppression. CHV was the only pathogen identified, and several CHV isolates were recovered in cell culture. No other viral pathogens or significant bacterial pathogens were found. Molecular and serological analyses revealed that the causative CHV isolates were from a single source but that none was a peculiar strain when the strains were compared with previous CHV strains. The virus had presumably spread among the dogs predisposed to infection in the center. The present results serve as a warning to canine clinics that, under the specific set of circumstances described, such serious CHV outbreaks may be expected wherever canine ITB occurs.Canine herpesvirus (CHV; Canid herpesvirus 1) is classified in the Varicellovirus genus of the Alphaherpesvirinae subfamily of the Herpesviridae. CHV was first described in 1965 as a pathogen responsible for a fatal generalized hemorrhagic disease of newborn pups (5). The host range of CHV is generally restricted to domestic and wild Canidae (11), and the worldwide distribution of CHV infection in domestic dog populations has been shown by virus isolation (2, 7, 10, 12, 24, 27) and seroepidemiological studies (6, 25, 28, 30, 31, 34). It is now well recognized that the pathogenic potential of CHV is mostly influenced by the age of the host (11). Pups infected in the postnatal period show the typical fatal hemorrhagic syndrome. Older pups manifest less severe clinical syndromes upon infection, and the respiratory disease called “infectious tracheobronchitis” (ITB) or “kennel cough” may be the most frequent clinical disorder in the field. Ocular disorders such as conjunctivitis and keratitis, either with or without ulceration, were also observed in young pups (17). Although the pathogenic potential of CHV for older dogs is apparently low and adult dogs often do not show any clinical signs following CHV infection, CHV may become an important perinatal pathogen for pregnant bitches, causing papulovesicular genital lesions and reproductive disorders such as embryonic resorption, abortion, and stillbirth (11).CHV is spread mainly by the oronasal and venereal transmission of viruses in the respiratory and genital secretions of acutely infected dogs, and fetuses are infected in utero (13, 14). Following the initial productive infection, in most cases CHV is not fully cleared by acquired immunity so that latency becomes established in several tissues, including the sensory ganglia (4, 19), and may persist for life. Latent viruses are sometimes reactivated by factors that alter immunity, such as stress, immunosuppressive therapy, or pregnancy, with the virus subsequently being excreted.The significance of CHV in the etiology of canine ITB has been considered to be rather low compared with that of other agents, such as canine parainfluenza virus (CPIV), canine adenovirus type 2 (CAV-2), and Bordetella bronchiseptica (9). Experimental infection of older pups or adult dogs with CHV isolates often resulted in either no clinical signs or mild upper respiratory symptoms (1, 15, 24, 32). Consequently, CHV has not generally been regarded to be a primary cause of canine ITB (9, 11). On the other hand, CHV has repeatedly been detected in dogs with ITB (3, 16, 24, 36), and a longitudinal study on the respiratory diseases of dogs housed in a rehoming kennel in the United Kingdom (8) indicated that CHV should be reevaluated as a significant agent responsible for ITB.This report is an account of a novel outbreak of canine ITB which was accompanied by deaths among dogs hospitalized in an animal referral medical center near Tokyo, Japan. It was concluded that CHV alone was responsible for the nosocomial outbreak. All of the dogs had been fully vaccinated before they entered the hospital, and during the hospitalization, most of the dogs had received steroid medication, surgery, or radiation therapy. It was considered that such medical treatments, in addition to hospitalization itself, might induce stress in the patients, leading to a condition of low-level immune resistance, and cause the recrudescence of latent CHV. Canine herpesvirus might then have spread contagiously among the dogs in the same clinic. The results of the present study suggest the need for caution, because CHV, which was previously thought to be an agent of low pathogenicity for adult dogs, should not be overlooked in specific circumstances.     

Development of a polymerase chain reaction test for specific identification of the urinary tract pathogen Aerococcus urinae.

A polymerase chain reaction test was developed for identification of the gram-positive urinary tract pathogen Aerococcus urinae. Oligonucleotide primers were based on highly specific sequences within the small-subunit rRNA gene. A confirmatory test based on hybridization of the amplified products to a highly specific internal probe was also developed.     

Endocarditis Caused by Rhodotorula Infection

Rhodotorula is an emerging opportunistic fungal pathogen that is rarely reported to cause endocarditis. We describe a case involving a patient who developed endocarditis due to Rhodotorula mucilaginosa and Staphylococcus epidermidis, proven by culture and histopathology. The case illustrates the unique diagnostic and therapeutic challenges relevant to Rhodotorula spp.     

Two Unusual Cases of Severe Soft Tissue Infection Caused by Streptococcus dysgalactiae subsp. equisimilis

We present two cases of invasive infection caused by Streptococcus dysgalactiae subsp. equisimilis, one that showed rapidly developing necrotizing fasciitis in a previously healthy man and one that showed severe cellulitis and septic shock even though the bacterium possessed a mutated emm gene, predicted to encode a truncated M protein.     

Thumb Infection Caused by Streptococcus pseudoporcinus

Streptococcus pseudoporcinus, a recently described organism found in the genitourinary tract of women, was isolated from a thumb wound in a male patient subsequent to trauma. This case describes a rarely reported non-genitourinary tract clinical isolate of S. pseudoporcinus.     

Persistent Infection Caused by Hobi-Like Pestivirus

A calf persistently infected by Hobi-like pestivirus was monitored for about 6 months, displaying clinical signs typical of bovine viral diarrhea virus persistent infection and shedding the virus through all body secretions, with maximal titers detected in urine. This report provides new insights into the pathogenesis of the emerging pestivirus.     

Three Clustered Cases of Candidemia Caused by Candida quercitrusa and Mycological Characteristics of This Novel Species

We investigated three nosocomial Candida quercitrusa candidemia cases occurring within 2 months in a Chinese hospital. Isolates were identifiable only by DNA sequencing of the rRNA genes. Genetic (via random amplified polymorphic DNA [RAPD]) and protein mass spectral (via matrix-assisted laser desorption ionization–time of flight mass spectrometry [MALDI-TOF MS]) analyses yielded identical profiles suggesting an outbreak. The fluconazole MICs of all the strains were 16 to 32 μg/ml.