Prostatic abscess caused by Streptococcus mutans

The first reported case of prostatic abscess caused by Streptococcus mutans isolated in pure culture is described. Urethral dilation for obstruction was unsuccessful. so suprapubic cystostomy was performed. Perineal aspiration under ultrasonic guidance resu lted in 10 mL of pus containing pure Strep mutans. DiagPROSTATIC ABSCESS. AN INFECTION USUALLY OCCURring as a complication of acute or chronic prostatitis (1) . is most common in the fifth and sixth decades of life (2). Predisposing factors include local conditions such as benign prostatic hypertrophy, prostatic carcinoma and bladder outlet obstruction, or following procedures such as urethral instrumentation. needle aspiration and biopsy of the prostate (2-4). In addition. diabetes mellitus is a common risk factor (3). In the pre-antibiotic era. Neisseria gonorThoea was one of the most common causes of prostatic abscess ( l); however. in recent years Gram-negative bacilli have become more prominent as etiologic agents of this infection (3). Prostatic abscesses are usually complications of contiguous genitourinary infections. and less often they occur via hematogenous spread. Common organisms Department of Microbiology and lq{eclious Diseases. Sir Mortimer 8 Davis -Jewish General Hospital and McGill University. Montreal. Quebec Con·espondence and reprints: DrJ Mendelson. Department of Microbiology and Iqfeclious Diseases. Sir Mortimer 8 Davis -Jewish General Hospital. 3755 Cote St Catherine Road. Montreal. Quebec H3T I E2 Received for publication May 7. 1990. Accepted July 28.

were Gram-negative bacilli and StaphyLococcus aureus, with some anaerobes, fungi and mycobacteria.In addition, polymicrobial prostatic abscesses can occur with either route of infection (3).Streptococcus viridans and enterococci have been reported in some cases of chronic p rostatitis (2.5,6).Other than two cases of prostatic abscesses caused by Enterococcus jaecaLis and one case by a 'Streptococcus species' that was not further identified (7,8), no case of prostatic abscess due to viridans streptococci was reported.
A case of prostatic abscess is reported in which Strep mutans, a species of the viridans streptococci group, was isolated in pure culture.

CASE PRESENTATION
In June 1989.a 39-year-old patient was admitted to the Jewish General Hospital in Montreal because of fever.dysuria, hesitancy and hematuria.He had had suprapubic removal of an obstructing vesicular stone at age four years.He had been otherwise well until one week prior to admission when dysuria, hesitancy and hematuria occurred.Without blood or urine cultures.he was treated by his family physician with amoxicillin for one week with initial improvement.but soon developed left flank pain that radiated to the scrotum with fever and chills.There had been no recent dental problems or procedures performed, and no history of p1ior cardiac valvu lopathy.
On examination.he appeared ill with a temperature of 38.5°C .No dental caries or gingival infection was found; there was left lower quadrant but no costovertebral angle tenderness; rectal examination revealed a non tender, normal size prostate.Cardiovascular examination was entirely normal and no cardiac murmur was heard.There were no manifestations of endocarditis.Blood leukocyte count was 17.2xl0 9 /L with 86% neutrophils.Although there was pyuria, multiple urine and blood cultures were negative.An intravenous pyelogram was normal.Treatment was begun with intravenous ampicillin and gentamicin.
On day 3 the patient developed perineal pain with a swollen tender prostate.Although pelvic ultrasound showed a mall prostatic abscess, perineal aspiration revealed no pus.Urethral obstruction from the abscess then developed.As urethral dilation was unsuccessful.suprapubic cystotomy was performed.Antibiotic coverage was changed to ceftriaxone with little improvement.On day 8 transrectal ultrasound revealed a large multiloculated abscess.and perineal aspiration under ultrasonic guidance resulted in 10 mL of pus.Culture of this material yielded a pure growth of Sirep mutans.The patient recovered uneventfully and completed a six week course of amoxicillin.A cystostomy catheter was removed eight months later with only residual hesitancy persisting.
The organism was identified as Sirep muians as follows: fermentation of mannitol.lactose.raffinose, sucrose and sorbitol but not of sorbose.ribose , and arabinose : fa il ure to grow at 1 0°C; and sodium hippurate negative.The organi m was sensitive to penicillin.

DISCUSSION
Prostatic abscesses usually occur following acute or chronic prostatitis (l).They may occur even when patients are on appropriate therapy (9).as demonstrated in the present case.Although he had a urological problem at age four years.this patient did not seem to have any risk factors usually associated with this condition.Diagnosis may be difficult since the clinical manifestations are nonspecific.with fever and urinary retention occurring in one-third of patients.Other symptoms such as dysuria, frequency and difficulty voiding occur less frequently (3).This patient presented initia lly with symptoms resembling urinary tract infection with hematuria and flank pain; these occur in only 7 and 1% of patients with prostatic absce ses.respectively Strep mutans prostatic abscess (10).Although prostatic enlargement occurred in 75% of cases.tenden1ess and bagginess were present in only 35 and 12%, respective ly (2).As such, prostatic abscesses can be easily missed on rectal exam.
A variety of techniques have been used to improve the diagnostic yield.Trans u rethral u ltrasound has been replaced by the transrectal approach, shown to be more usefu l as periprostatic structures can be better visualized and cystoscopy is not needed (11).As in the present case it also allowed guidance for transperineal prostatic abscess drainage which resu lts in fewer complications than other approaches (transurethral or transrectal) (4, 12.13).Computed tomography has been used with success (14.15).but Peeli ng and Griffiths (16) found ultrasound uperior to computed tomography in detecting different d iseases within the prostatic capsule.
Sirep muians is one of several species of viridans streptococci known to colonize tooth surfaces and contribute to the formation of dental plaques and caries (17).Although it has been isolated from intestinal and genitourinary sources.Sirep muians is primarily a cause of endocarditis and bacteremia -rarely urinary tract infections (10.18).Because of these facts, it is probable thai the present patient had a bacteremia with this organism from an oral source thai seeded the prostate.resu lting in abscess formation.li is unlikely that the patient had endocarditis as the initiating event.since the cardiovascular exam was entirely normal and there were no manifestations of infective endocarditis during the entire course of his illness.Viridans streptococci have been isolated occasionally in chronic pro tatitis (2.5.6).and a review of the medical literature reveals only one case of prostatic abscess caused by a •streptococcus species• thai was not further identified (8).The present patient is the first reported case of prostatic abscess caused by Sirep muians isolated in pure culture.
Studies on antibiotic penetration into prostatic tis ue and abscess are few .Excell ent concentration in the prostate were found with trimethoprim (19), ciprofloxacin (20) and carbenicillin (21).Concentrations for cephalosporins are largely unknown.and poor levels occurred with aminoglycosides (22).Treatment recommendation in terms of antibiotic choice and duration is largely empirical.depending on organisms isolated from abscess and blood cultures.as well as clinical response.Surgical therapy may require more than just simple aspiration.and on occasion transurethral resection of the prostate with subsequent drainage of the abscess may be required.