Bacteremia/septicemia due to Aerococcus-like organisms: report of seventeen cases. Danish ALO Study Group

Emerging pathogens Aerococcus urinae and Aerococcus sanguinicola from a Canadian tertiary care hospital

Background: Aerococcus urinae and Aerococcus sanguinicola are emerging pathogens linked with urinary tract infections. We present a case series of A. urinae and A. sanguinicola isolates characterizing the spectrum of clinical presentation, microbiological characteristics and antimicrobial sensitivities.Methods: Retrospective chart review was performed on patients who grew positive cultures for A. urinae and A. sanguinicola identified on MALDI-TOF in Saskatchewan from January to June 2023. Demographic and clinical variables, antimicrobial susceptibility and prescription were documented.Results: This cohort (n = 115) had a median age 82 years. A. urinae and A. sanguinicola infections spanned from urinary tract infection (n = 96) to urosepsis (n = 6). These infections were predominantly monomicrobial (73.9%) and were susceptible to ceftriaxone, penicillin G and vancomycin. Antimicrobials were seldom prescribed within the urinary tract infection cohort (31.2%).Conclusion: Untreated A. urinae and A. sanguinicola infections can precipitate into urosepsis. The reported antimicrobial susceptibility for these Aerococcus isolates should be utilized to provide appropriate antimicrobial coverage.

Fatal infective endocarditis caused by Aerococcus sanguinicola: a case report and literature review

Aerococcus sanguinicola is a bacterium that can cause urinary tract infections and on rare occasions infective endocarditis (IE). The prognosis of IE caused by aerococci is generally favourable despite that the patients are typically old and have multiple comorbidities. Here we report a case of A. sanguinicola native valve aortic IE in a 68-year-old man with an underlying urinary tract condition. The infection led to severe aortic valve insufficiency and rapid death before the patient could be subjected to surgery. This demonstrates that IE caused by A. sanguinicola can be severe and cause valve destruction. In addition to the case report, we provide a review of the current literature on A. sanguinicola IE.

The Infectious Tale of Aerococcal Aortic Endocarditis: Cardiac Pacing in Acute Aortic Insufficiency With Complete Heart Block as a Bridge to Aortic Valve Replacement

Here, we describe a rare case of Aerococcus endocarditis causing aortic insufficiency and paravalvular abscess presenting as complete heart block and shock. A 76-year-old man with diabetes mellitus presented to the emergency department with fever and dyspnea. His temperature was 102.4°F, heart rate 59 beats per minute, blood pressure 105/44 mmHg, and oxygen saturation was 98% on 6L oxygen. Examination revealed bounding carotid pulses, a 2/6 early blowing diastolic murmur at the left lower sternal border, and diminished lung sounds at the bases. Laboratory data showed leukocytosis of 19.65 k/µL, blood urea nitrogen 72 mg/dL, creatinine 2.92 mg/dL, lactic acid 3.1 mmol/L, pro-B-type natriuretic peptide 15,342 pg/mL, high-sensitivity troponin 136 ng/L, aspartate aminotransferase 129 U/L, and alanine aminotransferase of 115 U/L. An electrocardiogram showed complete heart block, and a transvenous pacemaker was placed. A transesophageal echocardiogram revealed an aortic root abscess and severe aortic insufficiency secondary to Aerococcus urinae. Ventricular pacing was used to decrease aortic insufficiency and optimize computed tomography with gating to view the coronary arteries due to wall motion abnormalities seen on the transthoracic echocardiogram. His aortic valve was replaced, and a pacemaker was planned. Aortic valve Aerococcus endocarditis is rare and can lead to complete heart block and aortic insufficiency. Cardiac pacing improves hemodynamics by increasing heart rate and decreasing left ventricular end-diastolic pressure.

Aerococcus-Related Infections and their Significance: A 9-Year Retrospective Study

Introduction:

Aerococcus spp. is a Gram-positive, catalase- and oxidase-negative, microaerophilic, nonmotile bacteria species rarely associated with human infections such as arthritis, bacteremia, endocarditis, and meningitis. The bacteria are also often confused with streptococci species or treated as a contaminant.

Patients and Methodology:

We conducted a retrospective, observational cohort study on all patients with Aerococcus spp. isolates in blood samples from July 2010 to June 2019. All categorical data were presented as counts and proportions, whereas continuous data were presented as median and interquartile ranges.

Results:

A total of 20 Aerococcus spp. isolates were identified over the study period of 9 years. Of these, Aerococcus urinae was isolated in 10 (50%), Aerococcus viridans in 6 (30%), and Aerococcus spp. (not speciated) in 4 (20%). The median age was 74.3 years (12 males and 8 females). The two most frequent presentations were fever (15 of 20) and altered mentation (6 of 15). Most of the patients (11 of 15) had at least one predisposing comorbidity related to the urinary tract system (8 with recurrent urinary tract infection, 7 with urinary incontinence, 3 with an indwelling catheter, 2 with renal stones, and 1 each with benign prostatic hyperplasia and a recent cystoscopy). The median white blood cell count was 18,426 cells/mL, median hemoglobin 10.96 g/dL, median platelet count 191,000 cells/μL, median blood urea nitrogen 28.6 mg/dL, and median creatinine 1.54 mg/dL. The urinary tract was the most likely source of bacteremia (10 of 20) based on either imaging findings (5 cases), positive urine culture for Aerococcus spp. (4 cases), or instrumentation history (1 case). In the rest, the cause of bacteremia could not be found. Endocarditis was suspected in 9 out of 20 patients. Transthoracic echocardiography/transesophageal echocardiography (TEE) confirmed 3 cases (2 aortic valves, 1 mitral valve and pacemaker). Interestingly, one case had septic emboli causing a right frontal stroke with a normal TEE and normal Doppler study for deep venous thrombosis. Blood cultures were positive in 35% (7 of 20) with polymicrobial growth, 3 with coagulase-negative staphylococci, 2 with Enterococcus faecalis, and the other 2 each with Diphtheroids spp. and Proteus mirabilis. Of the 20 cases, 9 and 10 required intensive care unit level care and vasopressor support, respectively. Most of the patients were treated for 5–14 days except the 3 cases with infective endocarditis (IE). The median hospital stay duration was 6.55 days with 2 fatalities (2 out of 20 patients).

Conclusion:

Old age and underlying urologic conditions are the best-known risk factors for Aerococcus spp. infection. Recent advances in diagnostic technology have led to an increase in detection of Aerococcus spp.-related infections. The rare occurrence of Aerococcus spp. in human infections and resultant lack of randomized control trials have resulted in a significant degree of clinical uncertainty in the management of Aerococcus spp. IE.

Prosthetic valve endocarditis caused by Aerococcus Urinae

Infective endocarditis (IE) caused by Aerococcus urinae is rare. The true incidence rate of this pathogen is likely underestimated as this is easily misidentified as Staphylococci or Streptococci. It is also associated with increased risk of complications such as systemic emboli. Aerococcus usually affects elderly males with underlying urological conditions. Here we present a case of IE with this rare Aerococcus urinae in a young man with a bioprosthetic aortic valve, despite negative urine cultures.

Aerococcus urinae - A potent biofilm builder in endocarditis

The diagnosis of infective endocarditis (IE) remains a challenge. One of the rare bacterial species recently associated with biofilms and negative cultures in infective endocarditis is Aerococcus urinae. Whether the low number of reported cases might be due to lack of awareness and misidentification, mainly as streptococci, is currently being discussed. To verify the relevance and biofilm potential of Aerococcus in endocarditis, we used fluorescence in situ hybridization to visualize the microorganisms within the heart valve tissue. We designed and optimized a specific FISH probe (AURI) for in situ visualization and identification of A. urinae in sections of heart valves from two IE patients whose 16S rRNA gene sequencing had deteced A. urinae. Both patients had a history of urinary tract infections. FISH visualized impressive in vivo grown biofilms in IE, thus confirming the potential of A. urinae as a biofilm pathogen. In both cases, FISH/PCR was the only method to unequivocally identify A. urinae as the only causative pathogen for IE. The specific FISH assay for A. urinae is now available for further application in research and diagnostics. A. urinae should be considered in endocarditis patients with a history of urinary tract infections. These findings support the biofilm potential of A. urinae as a virulence factor and are meant to raise the awareness of this pathogen.

Roles of the vagina and the vaginal microbiota in urinary tract infection: evidence from clinical correlations and experimental models

Mounting evidence indicates that the vagina can harbor uropathogenic bacteria. Here, we consider three roles played by the vagina and its bacterial inhabitants in urinary tract infection (UTI) and urinary health. First, the vagina can serve as a reservoir for Escherichia coli, the most common cause of UTI, and other recognized uropathogens. Second, several vaginal bacterial species are frequently detected upon urine culture but are underappreciated as uropathogens, and other vaginal species are likely under-reported because of their fastidious nature. Third, some vaginal bacteria that are not widely viewed as uropathogens can transit briefly in the urinary tract, cause injury or immunomodulation, and shift the balance of host-pathogen interactions to influence the outcomes of uropathogenesis. This chapter describes the current literature in these three areas and summarizes the impact of the vaginal microbiota on susceptibility to UTI and other urologic conditions.

Subacute Aerococcus urinae Infective Endocarditis With Mycotic Aneurysms in a Pediatric Patient: Case Report and Literature Review

Aerococcus urinae has been found to cause urinary tract infection in elderly patients and has been reported as a rare cause of infective endocarditis associated with significant morbidity and death in adults. However, information regarding its occurrence in children is lacking. We report here the case of a pediatric patient with subacute A urinae infective endocarditis with mycotic aneurysms.

Risk for Endocarditis in Bacteremia With Streptococcus-Like Bacteria: A Retrospective Population-Based Cohort Study

Background

Many genera and species of Streptococcus-like bacteria (SLB) can cause infective endocarditis (IE), but little is known about the epidemiology of and the risk factors for IE in SLB-bacteremia. The aim of the study was to analyze this in a cohort of patients with SLB-bacteremia, focusing on Abiotrophia, Aerococcus, Gemella, and Granulicatella. We also evaluated whether published scoring systems generated for other Gram-positive bacteria known to cause IE (HANDOC for streptococci and NOVA and DENOVA for enterococci) could be used in SLB bacteremia to decide whether transesophageal echocardiography (TEE) could be omitted.

Methods

Positive blood cultures with SLB were retrieved from population-based registries in Sweden (3.2 million inhabitants), from January 2012 to December 2017. Clinical data were collected from medical records. Risk factors for IE were analyzed and the performances of the scoring systems were calculated.

Results

The incidence of bacteremia with the 4 SLB genera was 30 episodes/1 000 000 population per year, of which Aerococcus contributed with 18. Among 568 episodes of bacteremia, 32 cases of IE were identified (5.6%). Infective endocarditis was most common in bacteremia with Abiotrophia (4 of 19) followed by Granulicatella (9 of 124), Gemella (6 of 87), and Aerococcus (13 of 338). NOVA had 100% sensitivity to identify IE but a low specificity (15%). For HANDOC and DENOVA, the sensitivities were 97% and 91%, respectively, whereas specificities were 85% and 90%, respectively, and numbers needed to screen were 3.6 and 2.8, respectively.

Conclusions

Bacteremia with these SLB is relatively rare, and the decision whether TEE should be performed or not could be based on either HANDOC or DENOVA.

Perigenital necrotizing soft tissue infection caused by Aerococcus urinae

Aerococcus urinae can cause severe invasive infections emanating from the urinary tract especially in older males with comorbidities. Here we describe a case of an 80 year-old man with multiple comorbidities presenting with a peri-penile abscess and signs of severe infection. Upon incision A. urinae was isolated in pure culture and the infection was cured by a combination of drainage and antimicrobials. This case demonstrates the potential of A. urinae to cause severe soft tissue infections in predisposed individuals.

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.

A rare case of Aerococcus urinae infective endocarditis in an atypically young male: case report and review of the literature

BACKGROUND

Aerococcus urinae is a gram-positive, alpha-hemolytic coccus bacterium primarily implicated in less than 1 % of all symptomatic urinary tract infections. Risk factors for disease include male gender, advanced age, and comorbid genitourinary tract pathology. Infections beyond the genitourinary tract are rare, though spondylodiscitis, perineal abscesses, lymphadenitis, bacteremia, meningitis, and endocarditis have been reported. Less than fifty cases of A. urinae infective endocarditis (IE) have been described in the literature. The rare occurrence of A. urinae in human infections and resultant lack of randomized controlled trials have resulted in a significant degree of clinical uncertainty in the management of A. urinae IE.

CASE PRESENTATION

We present an unusual case of a forty-three year-old male with A. urinae infective endocarditis (IE) who was successfully treated with mitral valve replacement and six weeks of penicillin/gentamicin therapy. In addition, we include a comprehensive review of all reported cases of IE due to A. urinae with specific attention to therapeutic regimens and treatment durations.

CONCLUSION

Recent advances in diagnostic technology have led to an increase in the frequency A. urinae is diagnosed. Reviewing cases of Aerococcus urinae infections, their clinical courses and subsequent management can assist future healthcare providers and their patients.

A Case of Pacemaker Endocarditis Caused by Aerococcus urinae

Background

Aerococcus urinae has lately been acknowledged as a cause of infective endocarditis (IE) especially in older males with underlying urinary tract disorders. In this population, cardiac implanted electronical devices (CIED) are not uncommon, but despite the capacity of A. urinae to form biofilm in vitro, no cases of aerococcal CIED infections have been reported to date.

Case Presentation

An 84-year-old male with pacemaker was admitted with dysuria one month after a transurethral procedure for urinary bladder cancer. A. urinae was isolated from urine and blood. Transesophageal echocardiography (TEE) was without signs of vegetation on valves or pacing cables. The patient was treated with a twelve-day course of β-lactam antibiotics. Forty days after the initial admission, the patient was readmitted due to malaise, general pain of the joints, chills, and renewed blood cultures grew A. urinae. TEE demonstrated a 10 × 5 mm vegetation on either the tricuspid valve or one of the pacing cables. The pacemaker system was completely removed and demonstrated macroscopic signs of infection. A temporary system was implanted, and after 14 days of penicillin G treatment, a new system permanent system was implanted. Total treatment time was 40 days. Recovery was uneventful.

Conclusion

This report demonstrates that A. urinae can cause CIED infection. In patients with A. urinae bacteremia and a CIED, this risk must be considered, especially if bacteremia reoccurs.

Aerococcus urinae Mitral Valve Endocarditis-Related Stroke: A Case Report and Literature Review

Background. Aerococcus urinae is a rare causative pathogen of infective endocarditis that results in a high risk of embolic events. The mortality rate for A urinae endocarditis is high. Old age and underlying urologic conditions are the best-known risk factors for infection. Case Description. We report the clinical course of the disease in a 49-year-old man who presented symptoms of a urinary tract infection. A few days later, transthoracic echocardiography showed a conspicuous mitral valve with myxomatous alterations. Following the detection of a cerebral embolism with associated stroke symptoms, as well as at the beginning of cardiac failure, the emergency indication for the surgical treatment of mitral valve endocarditis was given. On the second day following the operation, circulatory collapse rapidly developed. Following an unsuccessful attempt at cardiopulmonary resuscitation, the patient died. Review of the Literature. From 1991 to 2017, 29 cases of A urinae–induced endocarditis have been described in PubMed and Medline. One or 2 new cases are published annually. We review all reported cases of A urinae endocarditis, with an emphasis on the predisposing factors, course, and outcomes of the disease. Conclusion. A urinae endocarditis is a rare disease primarily affecting elderly men with urinary tract pathologies and comorbidities. The course of the disease is severe, and the outcome is often fatal. A 16S rDNA polymerase chain reaction investigation of bacterial genome provides proof of the presence of A urinae. Because of the high risk of embolism, rapid treatment should focus on the diseased heart valve. Based on existing data and the experience gained from handling cases, treatment with β-lactam and aminoglycosides is recommended. It is also recommended that operative therapy take place as soon as possible.

A prospective observational treatment study of aerococcal urinary tract infection

OBJECTIVES

Aerococcus urinae and Aerococcus sanguinicola cause urinary tract infections (UTIs) and antibiotic treatment recommendations are solely based on in vitro findings and limited clinical experience. Our objective was to investigate the effectiveness of different treatment strategies in aerococcal UTI through a prospective observational study.

METHODS

Urine samples with aerococci were identified and patients were enrolled. The aerococci were subjected to Etests. Information on clinical symptoms, and the treatment given, was collected. Patients were interviewed after the conclusion of treatment to assess clinical cure and a control urine culture assessed the microbiological cure.

RESULTS

Of 31,629 urine samples, 144 grew aerococci and fulfilled the inclusion criteria. 91 patients gave consent and the 72 patients with UTI were assessed for treatment outcome. 53 patients had A. urinae UTI, while 19 had A. sanguinicola UTI. Nitrofurantoin was most commonly prescribed, achieving clinical and microbiological success in 71/76% of cases of A. urinae UTI, and 42/50% of cases of A. sanguinicola UTI. Pivmecillinam achieved success in patients with A. urinae cystitis and ciprofloxacin in patients with pyelonephritis.

CONCLUSIONS

Our results support that nitrofurantoin is a valid option for the treatment of cystitis caused by A. urinae.

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.

Gram-Positive Uropathogens, Polymicrobial Urinary Tract Infection, and the Emerging Microbiota of the Urinary Tract

Gram-positive bacteria are a common cause of urinary-tract infection (UTI), particularly among individuals who are elderly, pregnant, or who have other risk factors for UTI. Here we review the epidemiology, virulence mechanisms, and host response to the most frequently isolated Gram-positive uropathogens: Staphylococcus saprophyticus, Enterococcus faecalis, and Streptococcus agalactiae. We also review several emerging, rare, misclassified, and otherwise underreported Gram-positive pathogens of the urinary tract including Aerococcus, Corynebacterium, Actinobaculum, and Gardnerella. The literature strongly suggests that urologic diseases involving Gram-positive bacteria may be easily overlooked due to limited culture-based assays typically utilized for urine in hospital microbiology laboratories. Some UTIs are polymicrobial in nature, often involving one or more Gram-positive bacteria. We herein review the risk factors and recent evidence for mechanisms of bacterial synergy in experimental models of polymicrobial UTI. Recent experimental data has demonstrated that, despite being cleared quickly from the bladder, some Gram-positive bacteria can impact pathogenic outcomes of co-infecting organisms. When taken together, the available evidence argues that Gram-positive bacteria are important uropathogens in their own right, but that some can be easily overlooked because they are missed by routine diagnostic methods. Finally, a growing body of evidence demonstrates that a surprising variety of fastidious Gram-positive bacteria may either reside in or be regularly exposed to the urinary tract and further suggests that their presence is widespread among women, as well as men. Experimental studies in this area are needed; however, there is a growing appreciation that the composition of bacteria found in the bladder could be a potentially important determinant in urologic disease, including susceptibility to UTI.

Clinical and microbiological features of Actinotignum bacteremia: a retrospective observational study of 57 cases

The purpose of this study was to investigate the incidence, clinical presentation, and prognosis of Actinotignum bacteremia in southern Sweden. Actinotignum isolates in blood cultures were identified retrospectively between 1st January 2012 and 31st March 2016 through searches in the clinical microbiology laboratory database. The population covered by this laboratory is approximately 1.3 million. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used for species determination. Etests were used for minimum inhibitory concentration (MIC) determination. The patients’ medical charts were reviewed. Fifty-eight episodes in fifty-seven patients with Actinotignum bacteremia were identified (A. schaalii = 53, A. sanguinis = 1, A. urinale = 2, and Actinotignum species = 3), which corresponds to an incidence of 11 cases per million inhabitants. Fifty-one percent of the isolates were in pure culture. The MICs were low for β-lactam antibiotics, whereas high MICs were recorded for ciprofloxacin and trimethoprim. Patients had a median age of 82 years, 72% were male, and a majority had underlying urological conditions. Thirty-six of the patients were diagnosed with a focus from the urinary tract. Thirty-one patients developed severe sepsis and nine patients died during the hospital stay. Our study is the largest of Actinotignum bacteremia and demonstrates that it is a condition with a significant fatality that affects elderly persons with underlying conditions. β-Lactams represent a rational treatment option.

Aerococcus urinae, a rare cause of infective endocarditis

We present the case of an elderly male who was initially seen in our hospital for a urinary tract infection that was treated with oral ciprofloxacin. He was admitted 2 weeks later with altered mental status and fever, and was found to have bacteraemia with Aerococcus urinae Owing to altered mental status a brain MRI was performed which showed evidence of embolic stroke. Following this, a transesophageal echocardiogram showed severe mitral regurgitation and a vegetation >1 cm involving the mitral valve with associated destruction of posterior valve leaflets. The patient was started on antibiotics intravenous penicillin G and intravenous gentamicin for a total duration of 6 weeks. He underwent mitral valve replacement on day 4 of hospitalisation. The postoperative course was complicated by ventilator-dependent respiratory failure, requiring tracheostomy and eventual transfer to a skilled nursing facility. Unfortunately, he died after 2 weeks of stay at the facility.

A population-based study of aerococcal bacteraemia in the MALDI-TOF MS-era

The purpose of this study was to determine the incidence of aerococcal bacteraemia in the MALDI-TOF MS-era, to describe the clinical presentation and to determine the MIC values of aerococci for ten antibiotics. Aerococci in blood cultures were identified through searches in the laboratory database for the years 2012-2014. MALDI-TOF MS, sequencing of the 16S rRNA gene and a PYR test were used for species identification. Patients' medical charts were systematically reviewed. Etests were used to determine MIC values. Seventy-seven patients were identified (Aerococcus urinae n = 49, Aerococcus viridans n = 14, Aerococcus sanguinicola n = 13 and Aerococcus christensenii n = 1) corresponding to incidences of 14 cases per 1,000,000 inhabitants per year (A. urinae) and 3.5 cases per 1,000,000 inhabitants per year (A. sanguinicola and A.viridans). A. urinae was in pure culture in 61 %, A. sanguinicola in 46 % and A. viridans in 36 % of the cases. The A. urinae and A. sanguinicola patients were old and many had urinary tract disorders, and a majority had a suspected urinary tract focus of the bacteraemia. Eighty percent of the A. urinae patients were men. Five A. urinae patients were diagnosed with infective endocarditis. Six patients died within 30 days. Most isolates had low MICs to penicillins and carbapenems. MALDI-TOF MS has led to an increased identification of aerococcal bacteremia. A. urinae remains the most common Aerococcus in blood cultures and in aerococcal IE.

Clinical and microbiological features of infective endocarditis caused by aerococci

PURPOSE

To define the clinical presentation of aerococcal infective endocarditis (IE) and the prevalence of synergy between penicillin and gentamicin on aerococcal isolates.

METHODS

Cases of aerococcal IE between 2002 and 2014 were identified in the Swedish Registry of Infective Endocarditis (SRIE). MALDI-TOF MS was used to confirm species determination. The medical records were analysed and compared to cases reported to the SRIE caused by other pathogens.

RESULTS

Sixteen cases of aerococcal IE, fourteen with Aerococcus urinae and two with Aerococcus sanguinicola, were confirmed. Etest-based methods and time-kill experiments suggested synergy between penicillin and gentamicin towards seven of fifteen isolates. The patients with aerococcal IE were significantly older than those with streptococci or Staphylococcus aureus IE. Most of the patients had underlying urinary tract diseases or symptoms suggesting a urinary tract focus of the infection. Seven patients with aerococcal IE presented with severe sepsis but ICU treatment was needed only in one patient and there was no fatality. Valve exchange surgery was needed in four patients and embolization was seen in three patients.

CONCLUSIONS

This report is the largest on aerococcal IE and suggests that the prognosis is relatively favourable despite the fact that the patients are old and have significant comorbidities.

Epidemiology and antibiotic susceptibility of aerococci in urinary cultures

In this study, we present population-based data regarding the prevalence of aerococci in clinical urinary samples. During a 3-month period, all aerococcal isolates from urinary samples from 2 clinical microbiology laboratories were collected. We identified 64 Aerococcus urinae isolates and 40 Aerococcus sanguinicola isolates, which correlates with an incidence of 33 cases of aerococcal bacteriuria per 100,000 inhabitants per year. The median age was 83years for all patients with aerococcal bacteriuria, which was significantly higher than for patients with Escherichia coli or Enterococcus faecalis bacteriuria. Sex was almost equally distributed between men and women with aerococcal bacteriuria, whereas females dominated in E. coli bacteriuria. The aerococcal isolates displayed low MICs for ampicillin, cefalotin, mecillinam, and nitrofurantoin. Most A. sanguinicola isolates were resistant to ciprofloxacin, whereas most A. urinae isolates had low MICs. Clinical studies are needed to establish clinical breakpoints and optimal treatment.

Aerococci and aerococcal infections

Aerococcus is a genus that comprises seven species, of which Aerococcus urinae, and Aerococcus sanguinicola are emerging human pathogens. Aerococci are gram positive cocci that are easily misidentified as streptococci or staphylococci, and thus the incidence of aerococcal infections has been underestimated. With the introduction of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) clinical microbiologists now have access to a rapid and accurate method to identify aerococci. A. urinae and A. sanguinicola are isolated in a small proportion of urinary specimens in many laboratories and many patients with bacteriuria with aerococci have symptoms of urinary tract infection (UTI). A. urinae, and also A. sanguinicola, cause invasive infections including infective endocarditis (IE) with many reported fatalities. Especially older men with urinary tract abnormalities are at risk for bacteraemia with A. urinae but the prognosis of bacteraemia without IE is favourable. Penicillin is appropriate for treatment of invasive infections and in IE, addition of an aminoglycoside should be considered. Treatment of UTI with aerococci is complicated by uncertainty about the effect of trimethoprim-sulphametoxazole and fluoroquinolones on aerococci. This review will discuss identification of Aerococcus spp., antibiotic resistance, the clinical presentation and management of aerococcal infections as well as the virulence mechanisms of these bacteria.

[A case of infective Aerococcus urinae endocarditis successfully treated by aortic valve replacement]

Aerococcus urinae is a endocarditis rare causative organism with low virulene. We report an A. urinae endocarditis case treated by aortic valve replacement. An 80-year-old woman hospitalized for urinary tract infection and hydronephrosis due to three-week renal calculi. Blood culture on admission isolated Streptococcus acidominimus. During the course, she was transferred to our care for surgical intervention after developing congestive heart failure due to severe aortic regurgitation. Echocardiographic findings indicated infective endocarditis. She underwent aortic valve replacement, and gram staining of the resected valve tissue showed gram-positive cocci, although valve culture was negative. PCR amplification and DNA sequencing using the valve material matched an A. urinae sequence. The woman recovered and was discharged six weeks after antibiotic treatment.

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.

Actinobaculum schaalii: a common cause of urinary tract infection in the elderly population. Bacteriological and clinical characteristics

To-date only 21 clinical cases of Actinobaculum schaalii infection have been published, and A. schaalii has been considered a rare cause of urinary tract infection (UTI) and urosepsis. Between y 2005 and 2008, we isolated A. schaalii from 55 predisposed elderly patients. In these cases, microscopic findings of coccoid rods in wet smears of urine gave rise to clinical suspicion and subsequently to its isolation from urine. Typically only scant growth of A. schaalii occurred after incubation of the urine for 24 h, but it became visible after 2 days of incubation in 5% CO(2). Preliminary biochemical identification was carried out by combining the API Coryne and Rapid ID32A test systems, and the identification was later confirmed by partial 16S rDNA gene sequencing. During the 4-y period, A. schaalii caused septicaemia, UTIs and asymptomatic bacteriuria. One patient was later infected with Actinobaculum massiliense. The incidence of A. schaalii infections is much higher than previously reported. We present numerous case reports and describe the bacteriological and clinical characteristics of this overlooked uropathogen.

Fatal infective endocarditis due to Aerococcus urinae--case report and review of literature

Aerococcus-related infective endocarditis is a rare form of endocarditis with a high mortality. Most cases have associated genitourinary system pathology. Aerococcus urinae is a Gram-positive coccus that is arranged in clusters resembling Staphylococcus, but its growth characteristics and colonial morphology are closer to that of an alpha-hemolytic Streptococcus. This organism may initially be dismissed as a contaminant in clinical cultures from nonsterile sites. We report a representative case and review the literature concerning this unusual case of infective endocarditis.

Clinical significance of Aerococcus urinae: a retrospective review

A retrospective chart review was performed on 54 patients with positive urine cultures during a 1-year period to assess the clinical significance of Aerococcus urinae. Based on predetermined criteria, patients were classified into 2 groups: those with urinary tract infections (UTIs) and those who were considered colonized. The majority of the patients were > or =65 years old and were female. Only 31% of patients with UTI and 45% of colonized patients had A. urinae isolated in pure cultures. Both groups had significant but similar underlying medical conditions, with urologic conditions being predominant. Significantly more patients in the UTI group had urinary catheters (P < .01). No direct complications or invasive disease was recognized in either group regardless of whether patients were treated with antibiotics. Apparently, A. urinae is a relatively avirulent organism when cultured from urine.

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.

Phenotypic description and antimicrobial susceptibilities of Aerococcus sanguinicola isolates from human clinical samples

This report describes the clinical sources and phenotypic characterization of 16 isolates of Aerococcus sanguinicola. Sixteen conventional tests were used to describe and differentiate the 16 isolates of A. sanguinicola from 30 strains of Aerococcus viridans, 27 strains of Aerococcus urinae, and a single strain each of Aerococcus christensenii and Aerococcus urinaehominis. The phenotypic characterizations of the type strains for each species and 14 A. sanguinicola isolates were also compared in the two reference laboratories. A. sanguinicola are catalase-negative, vancomycin-susceptible, gram-positive cocci arranged in clusters and tetrads, as are all Aerococcus species except A. christensenii (which is arranged in short chains). All 16 isolates of A. sanguinicola were leucine aminopeptidase and pyrrolidonylarylamidase positive, which is unique to this species among the aerococci. All A. sanguinicola isolates grew in broth containing 6.5% NaCl, hydrolyzed hippurate, and were variable in the bile-esculin test. None of the isolates deaminated arginine or were Voges-Proskauer positive. The type strain of A. sanguinicola was isolated from a blood culture of a patient living in Denmark. Seven additional isolates were from patients living in Canada, all with urinary tract infections (six were female). Eight isolates were from patients living in five different states in the United States; five were from patients with urinary tract infections, and three were from blood cultures of one patient each with pneumonia, suspected endocarditis, and unknown clinical conditions. The antimicrobial susceptibility patterns were unremarkable; all isolates tested were susceptible to penicillin, amoxicillin, cefotaxime, cefuroxime, erythromycin, chloramphenicol, vancomycin, quinupristin-dalfopristin (Synercid), rifampin, linezolid, and tetracycline. Six of the 15 cultures were resistant to ciprofloxacin and levofloxacin, but all 15 strains were susceptible to sparfloxacin. High-level resistance was detected for meropenem (2 strains) and trimethoprim-sulfamethonazole (1 strain). Intermediate resistance was detected for trimethoprim-sulfamethoxazole (10 strains) and clindamycin (3 strains).

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.

Endocarditis due to Aerococcus urinae: diagnostic tests, fatty acid composition and killing kinetics

Two cases of Aerococcus urinae endocarditis are reported. The organism is not included in any database of commercial identification systems at this time. Formation of tetrades and positive reactions for leucine arylamidase and beta-glucuronidase pointed strongly to A. urinae. The cellular fatty acid pattern was similar to that of Aerococcus viridans, with predominantly C16:0, C18:1 omega 9c and C18:0; the presence of C18:1 omega 7t differentiated our isolates from A. viridans and can support the diagnosis of A. urinae. Furthermore, susceptibility to penicillin but resistance to cotrimoxazole represents a pattern opposite to that of A. viridans. Minimal inhibition concentrations of gentamicin and netilmicin were < or = 64 mg/l but those of tobramycin were > or = 256 mg/l. Penicillin combined with either gentamicin or netilmicin showed distinct synergy in killing kinetics. These combinations seem to be the appropriate regimen to treat A. urinae endocarditis.

Urinary tract infections with Aerococcus 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 of Aerococcus urinae urinary tract infections (> or = 10(5) cfu/ml) were investigated in two large medical microbiology laboratories in the Netherlands. The incidence of Aerococcus 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.