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 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.     

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.     

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.     

Three Cases of Serious Infection Caused by Aerococcus urinae

 Three cases of serious infection caused by Aerococcus urinae are presented: a patient with endocarditis and two patients with soft-tissue infection (phlegmon and balanitis respectively). The literature on Aerococcus urinae infections is reviewed and the antibiotic therapy discussed. Aerococcus urinae is a pathogen isolated primarily from urine specimens of elderly patients with local or systemic predisposing conditions. Most infections are mild, but serious infections such as endocarditis and septicemia/urosepsis have been described. Penicillin or ampicillin in combination with an aminoglycoside and close monitoring of the patient's clinical status and laboratory results would seem to be the best strategy for management of cases of serious infection.     

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.     

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.     

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.     

Aerococcus bacteremia associated with granulocytopenia

Two cases of bacteremic infection due to aerococci in granulocytopenic patients with acute leukemia and oral mucositis are described. Strains isolated from blood cultures of both patients were resistant to the antibiotics given orally for prophylaxis. One patient died in septic shock; surveillance cultures from oral washings in the other repeatedly showed high concentrations of aerococci. Aerococci were also isolated from surveillance cultures taken from 5 of 17 other patients with acute leukemia; however, their viable counts were lower than in the surviving patient.     

Penicillin-resistant Aerococcus viridans bacteremia associated with granulocytopenia

Aerococcus viridans, a catalase-negative gram-positive coccus rarely causing bacteremia, was isolated from blood cultures of a 52-yr-old man under the granulocytopenic condition. The isolate showed the typical characteristics of A. viridans, i.e., tetrad arrangements in gram stain, positive pyrrolidonyl aminopeptidase (PYR) and negative leucine aminopeptidase (LAP) reactions, and no growth at 45 degrees C.The isolate was revealed to be highly resistant to penicillin, erythromycin, clindamycin, and ceftriaxone, although most strains of A. viridans isolated from the previously reported patients were susceptible to penicillin and other commonly used antibiotics. Even though A. viridans is rarely associated with human infections, it could be a potential causative agent of bacteremia, especially in immunocompromised patients.     

Endocarditis caused byAerococcus urinae,a newly recognized pathogen

Aerococcus urinae is a newly described pathogen. A case ofAerococcus urinae endocarditis is presented, the primary focus being a urinary tract infection. The diagnosis of endocarditis was supported by isolation ofAerococcus urinae from blood as well as from heart vegetations.     

Actions of potassium channel openers in rat detrusor urinae.

This study was performed to investigate the action of potassium channel openers on the mechanical activity of detrusor muscle isolated from rats. Detrusor muscle strips, 15 mm in length, were myographied isometrically in an isolated organ bath. P 1060, RP 49356 and BRL 38277, potassium channel activators, reduced the basal tone and diminished the phasic activity of detrusor concentration-dependently. P 1060, RP 49356 and BRL 38227 suppressed the maximal responses to bethanechol and shifted the concentration-response curves of bethanechol-induced contraction to the right. RP 49356 and BRL 38227 reduced the contraction by low (20 mM) concentration of potassium. P 1060, however, diminished the high (80 mM) and low (20 mM) concentration of potassium-induced contraction. Glibenclamide, an inhibitor of ATP-dependent potassium channel, antagonized the suppressive action of P 1060, RP 49356 and BRL 38227 on the basal tone. Apamin or procaine did not antagonize it significantly. Based on these results, it is suggested that the relaxation of detrusor muscle strip caused by P 1060, RP 49356 and BRL 38227 may predominantly involve opening of the same potassium channel, i.e., the ATP-dependent potassium channel.     

Characterization of Aerococcus viridans isolates from swine clinical specimens

We present here the biochemical and genetic characterization and antimicrobial susceptibility of 58 isolates of Aerococcus viridans isolated in pure culture from different clinical specimens of normally sterile body sites of pigs. A. viridans isolates were commonly susceptible to beta-lactam antimicrobials and exhibited a great genetic heterogeneity as determined by pulsed-field gel electrophoresis typing. The results indicate that A. viridans might be included in the list of possible etiological agents causing disease in pigs.     

Urinary tract infections withAerococcus urinae in the South of the Netherlands

Aerococcus urinae is an uncommon urinary tract pathogen that causes infections predominantly in elderly persons with local or general predisposing conditions. During a one-year study, the clinical features ofAerococcus urinae urinary tract infections (10⁵ cfu/ml) were investigated in two large medical microbiology laboratories in the Netherlands. The incidence ofAerococcus urinae urinary tract infections ranged between 0.31 and 0.44% for the two laboratories. The median age (range 35–95 years) of patients with this infection was 82.5 years for women and 77.5 for men. Men had significantly (p < 0.01) more local predisposing conditions than did women. Underlying systemic diseases such as diabetes mellitus, malignancy, and dementia were found in 67.5% of patients. Most patients (97.5%) had the classic signs of a urinary tract infection, but none of them developed serious symptoms. All isolates tested were susceptible to penicillin, amoxicillin, and nitrofurantoin, 78.3% were susceptible to norfloxacin, and all were resistant to sulfonamides. The majority of patients were treated with amoxicillin, amoxicillin with clavulanic acid, or norfloxacin.