The Pathogenic Role of Actinomyces spp. and Related Organisms in Genitourinary Infections: Discoveries in the New, Modern Diagnostic Era

Actinomycosis is a chronic, suppurative, granulomatous infectious disease, caused by different species of Actinomyces bacteria. To date, 26 validly published Actinomyces species have been described as part of a normal human microbiota or from human clinical specimens. Due to the rapid spread of new, modern diagnostic procedures, 13 of 26 of these species have been described in this century and the Actinomycetaceae family has undergone several taxonomic revisions, including the introduction of many novel species termed Actinomyces-like organisms (ALOs). There is scarce data available on the role of these novel bacterial species in various infectious processes in human medicine. The aim of this review is to provide a comprehensive overview of Actinomyces and closely related organisms involved in human diseases-with a special focus on newly described species-in particular their role in genitourinary tract infections in females and males.

Actinotignum (formerly Actinobaculum) schaalii: a review of MALDI-TOF for identification of clinical isolates, and a proposed method for presumptive phenotypic identification

Actinotignum schaalii is a recognised cause of urinary tract infection. Following a case of urosepsis, 20 isolates of A. schaalii were collected over an initial 18 month period from urine and blood culture. An additional 25 isolates were collected over the following 13 months. Actinotignum schaalii had likely been overlooked or dismissed as a contaminant in our laboratory prior to this study period. It grows slowly on blood agar with supplemental CO2 or anaerobically. It may not grow on MacConkey agar or chromogenic agars used for routine urine culture. Repeated attempts at identification by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) may be required as the optimal age of cultures for testing is unclear. Utilising its characteristic antibiogram may assist phenotypic identification of this organism which is otherwise difficult to distinguish from other actinomycetes.

Actinotignum schaalii (formerly Actinobaculum schaalii): a newly recognized pathogen-review of the literature

The genus Actinotignum contains three species, Actinotignum schaalii (formerly Actinobaculum schaalii), Actinotignum urinale and Actinotignum sanguinis. A. schaalii is the species most frequently involved in human infections, with 172 cases, mostly urinary tract infections (UTIs), reported so far. Invasive infections have also been described. This facultative anaerobic Gram-positive rod is part of the urinary microbiota of healthy patients. It is responsible for UTIs, particularly in elderly men and young children. A. schaalii is an underestimated cause of UTIs because of its fastidious growth on usual media and difficulties associated with its identification using phenotypic methods. Indeed, this slow-growth bacterium requires blood-enriched media and an incubation time of 48 hours under anaerobic or 5% CO2 atmosphere. Furthermore, only matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) or molecular-based methods allow the accurate identification of this bacteria. MALDI-TOF using Microflex LT with the Biotyper database (Bruker Daltonics, Bremen, Germany) is the most reliable technology for the routine identification of A. schaalii. The identification of this uropathogen is all the more important because it is resistant to trimethoprim/sulfamethoxazole and second-generation quinolones that are widely used in the treatment of UTIs. Antimicrobial therapy using β-lactams prolonged for up to 2 weeks is the most efficient treatment and should be recommended. Microbiologists should assess the presence of A. schaalii in urine using appropriate culture and identification methods in the case of a direct examination that is positive for small coccoid rods, a negative nitrite urinary stick associated with leukocyturia, treatment failure with trimethoprim/sulfamethoxazole or fluoroquinolones, or undocumented, repeated UTIs.

[Emerging uropathogens: Point for urologists and biologists]

INTRODUCTION

Technological advances during the last years in bacterial identification by molecular biology and mass spectrometry, or Matrix Assisted Laser Desorption Ionisation-Time of Flight (MALDI-TOF) have allowed identifying new bacteria involved in urinary tract infections. The purpose of this review is to familiarize clinicians with these bacteria so that they can look at a particular target population and help biologists to suspect and identify them.

METHOD

A bibliographic research was performed using the Medline database concerning the keywords Aerococcus, Actinobaculum, Alloscardovia, Trueperella.

RESULTS

If Aerococcus sp. is now well known, Actinobaculum sp., Alloscardovia sp. and Trueperella sp. remain rarely isolated and unknown from clinicians. Importance of these germs could be underestimated because of the identifying and isolation difficulties which existed beforehand. They are particularly found in a population of elderly people with underlying conditions or urological risk factors of urinary tract infection. Actinobaculum schaalii is also found more frequently in young children.

CONCLUSION

Aerococcus sp. et A. schaalii are true uropathogens not to be underestimated. Further studies are still needed to confirm the specific involvement of Trueperella and Alloscardovia in urinary diseases.

Actinobaculum schaalii: identification with MALDI-TOF

Actinobaculum schaalii is an emerging uropathogen. So far, its identification has been performed with 16S rRNA gene sequencing or PCR. The diagnosis has often been delayed due to fastidious growth and identification problems. Eleven clinical isolates of A. schaalii from bloodstream infections that were initially identified with 16S rRNA sequencing analysis were recovered and later identified with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF). We present a review of bacteriological data of these patients, an algorithm for fast laboratory work-up and advocate the use of sensitized culture of urine to allow better recovery of A. schaalii in susceptible patients.

Actinobaculum schaalii, a commensal of the urogenital area

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Actinobaculum schaalii is considered to be a part of the normai flora in the genital and urinary tract area. It has been associated to urinary tract infection (UTI), sepsis, osteomyelitis, endocarditis and Foumier's gangrene. So far it has mainly been isolated from urine, blood and pus, and predominantly in elderly patients. This study examined the habitat of A. schaalii by collecting samples from skin and urine in patients with kidney or ureter stones before and after treatment with Extracorporeal Shock Wave Lithotripsy (ESWL). Additionally faeces and vaginal swabs from routine specimen in patients not undergoing ESWL and without known urinary calculi were also analysed. The study does not find A. schaalii in faeces but shows it to be presents on skin and mucosa in the genital area. A. schaalii is also shown a possible pathogen in the stone-patient group undergoing ESWL.

OBJECTIVE

To study the habitat of Actinobaculum schaalii by examing groin swabs, faeces samples and vaginal swabs, and to determine whether it is a common uropathogen in patients with kidney or ureter stones.

PATIENTS AND METHODS

A quantitative real-time PCR assay was used to analyse all samples, which were collected between 2010 and 2011. A total of 38 patients (24 men and 14 women), with kidney or ureter stones and undergoing extracorporeal shock wave lithotripsy (ESWL), provided urine samples and had groin swabs taken. In addition, 30 faecal samples and 19 vaginal swabs that had been sent for routine microbiological examinations from patients outside the ESWL group were analysed. A chi-squared test was used to analyse the differences between patient groups, studying samples from urine, faeces samples, groin swabs and vaginal swabs.

RESULTS

Actinobaculum schaalii was found in the urine samples from 14 (37%) patients undergoing ESWL, and in both urine and groin swabs from seven (18%) patients. Actinobaculum schaalii was not found in faeces samples but it was found in six (32%) of the vaginal swabs, predominantly in patients >50 years (P = 0.06).

CONCLUSION

The study indicates that A. schaalii is a commensal found on skin, urine and vaginal mucosa in the human urogenital area and supports other investigations in its finding that the elderly are at greatest risk of being colonized with A. schaalii.

Actinobaculum schaalii an emerging pediatric pathogen?

Background

Actinobaculum schaalii was first described as a causative agent for human infection in 1997. Since then it has mainly been reported causing urinary tract infections (UTI) in elderly individuals with underlying urological diseases. Isolation and identification is challenging and often needs molecular techniques. A. schaalii is increasingly reported as a cause of infection in humans, however data in children is very limited.

Case presentation

We present the case of an 8-month-old Caucasian boy suffering from myelomeningocele and neurogenic bladder who presented with a UTI. An ultrasound of the urinary tract was unremarkable. Urinalysis and microscopy showed an elevated leukocyte esterase test, pyuria and a high number of bacteria. Empiric treatment with oral co-trimoxazole was started.

Growth of small colonies of Gram-positive rods was observed after 48 h. Sequencing of the 16S rRNA gene confirmed an A. schaalii infection 9 days later. Treatment was changed to oral amoxicillin for 14 days. On follow-up urinalysis was normal and urine cultures were negative.

Conclusions

A.schaalii is an emerging pathogen in adults and children. Colonization and subsequent infection seem to be influenced by the age of the patient. In young children with high suspicion of UTI who use diapers or in children who have known abnormalities of their urogenital tract, infection with A. schaalii should be considered and empiric antimicrobial therapy chosen accordingly.

Actinobaculum schaalii: review of an emerging uropathogen

Actinobaculum schaalii is a facultative anaerobic, Gram-positive rod-shaped species phylogenetically related to Actinomyces that is likely part of the commensal flora of the human genitourinary tract. Because of its fastidious growth under aerobic conditions and its resemblance to bacteria of the resident flora, A. schaalii is frequently overlooked or considered as a contaminant. It is also difficult to identify phenotypically, still requiring molecular identification. Note that the recent technology of matrix-assisted laser desorption/ionisation time-of-flight-mass spectrometry could be a promising tool for its identification. Recent studies using sensitive PCR assays showed that its clinical significance was largely underestimated. Since its first description in 1997, A. schaalii has been responsible for numerous urinary tract infections (UTIs), mainly in elderly (usually >60 years) and patients with underlying urological conditions. Infected urines usually show many Gram-positive rods with significant leukocyturia and a negative test for nitrites. Numerous cases of severe infections have also been described, such as urosepsis, bacteremia, cellulitis, spondylodiscitis, and endocarditis. In vitro, A. schaalii is highly susceptible to β-lactams but it is resistant to ciprofloxacin and cotrimoxazole, first-choice antimicrobials for the oral treatment of UTIs. A penicillin (e.g. amoxicillin) or a cephalosporin (e.g. cefuroxime, ceftriaxone) should be the preferred treatment.