Vaginal colonization with group B Streptococcus (Streptococcus agalactiae) and peritonitis in a woman on CAPD

Renzo Scanziani1, Beatrice Dozio1, Ivano Baragetti1, Paolo Grillo1, Laura Colombo2, Sebastiano De Liso3 and Maurizio Surian1

1 Renal Unit, 2 Department Clinical Pathology, 3 Obstetrics and Gynaecology Department, Desio Hospital, Milan, Italy

Correspondence and offprint requests to: Renzo Scanziani MD, Renal Unit, Desio Hospital, I-20033 Desio, Milan, Italy.

Keywords: CAPD; peritonitis; Streptococcus agalactiae; vaginal colonization



   Introduction
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 Discussion
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Group B streptococcus, or Streptococcus agalactiae, is a Gram-positive coccus, catalase negative, facultatively anaerobic, spherical or ovoid, and less than 2 µm in diameter; it is usually ß-haemolytic and is reliably identified by its production of Lancefield group B antigen [1]. Streptococcus agalactiae causes invasive disease primarily in newborns and in women in the postpartum period [2]. Adults with severe infections unrelated to pregnancy are usually elderly and have underlying illness such as diabetes mellitus, liver failure, malignancy, acquired immunodeficiency syndrome, or renal failure [2]. In non-pregnant adults, skin or soft-tissue infection, bacteraemia, genitourinary infection, and pneumonia are the most common manifestations of disease [3]. Peritonitis due to group B ß-haemolytic streptococcus is infrequent in continuous ambulatory peritoneal dialysis (CAPD) patients [47]. We describe a case of S. agalactiae peritonitis in a young female on CAPD, which gives some clues as to the mode of infection.



   Case
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The patient is a 23-year-old female with a history of end-stage renal failure (ESRD) secondary to renal dysplasia and chronic pyelonephritis. On 27 December 1997 a Tenckhoff catheter was placed and on 15 January 1998 she successfully completed training and started CAPD. Six months later she was admitted with a 12-h history of abdominal pain, vomiting, and chills. Her blood pressure was 130/80 mmHg, heart rate 96 per minute and regular, temperature 38.2°C. Abdominal examination showed diffusive tenderness on palpation. The bowel sounds were active. Haematological investigations showed an increased white blood cell count (16.2x103/mm3) with a marked shift to the left. The peritoneal effluent was cloudy with a WBC of 760/mm3 and 85% segmented neutrophilis. Gram stain of the dialysate showed few Gram-positive cocci and many polymorphonuclear cells. Samples of peritoneal dialysis fluid and blood were cultured and an exit-site culture was also performed. After two quick dialysate exchanges without addition of antibiotics, treatment was started according to the current peritonitis schedule, i.e. after a loading dose of 500 mg/l cephalothin plus 8 mg/l netilmicin intraperitoneally, administration of 125 mg/l cephalothin and 4 mg/l netilmicin per dialysis bag with a dwell time of 6 h. Heparin 1000 U/l was added to each bag, until the effluent was clear. After 24 h group B streptococcus, S. agalactiae, was isolated from the peritoneal fluid and the two blood cultures. The organism was sensitive to ampicillin, cephalothin, penicillin, clindamycin, erythromycin, and vancomycin (see below). A vaginal swab was then cultured. Abdominal symptoms resolved and dialysate WBC decreased to normal levels within 72 h. After 48 h peritoneal fluid cultures were negative. The vaginal swab culture was positive for group B streptococcus, S. agalactiae, while the exit-site culture was negative. Cephalothin was administered for a total treatment period of 14 days and netilmicin for 1 week.

The patient, whose menses were irregular, was on the third day of her menstrual cycle when she was admitted to the hospital. Upon further questioning she reported that she had had sexual intercourse 12 h before admission.

After recovery oestrogens were administered to regularize the patient cycle, and cephalosporin (cephalexin 1 g b.i.d.) during the menstrual period was prescribed to prevent GBS infection.



   Discussion
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Streptococcus agalactiae is a Gram-positive group B ß-haemolytic streptococcus (GBS). The gastrointestinal tract is the most likely human reservoir of GBS, with the genitourinary tract the most common site of secondary spread [2]. Colonization rates can differ between ethnic groups, geographic areas, and age groups [2]. It is a member of the normal flora of the female genital tract, and in most studies from 10 to 30% of pregnant women were colonized with GBS in the vaginal or rectal area [8]. This agent is frequently implicated as an important cause of severe invasive disease primarily in newborns, pregnant women, and adults with underlying diseases [2,3,9]. In newborns, the most frequent presentations are bacteraemia, pneumonia, or meningitis [2,3]. In pregnant women GBS infection causes urinary-tract infection, amnionitis, endometritis, and wound infection postpartum [2]. In non-pregnant adults bacteraemia, genitourinary infection, and pneumonia are the most frequent manifestations [9]. Adults with bacteraemia unrelated to pregnancy are usually elderly and suffer from diseases such as diabetes mellitus, malignancy, liver or renal failure, or AIDS [9].

CAPD peritonitis is rarely caused by S. agalactiae. Streptococcus species are the cause of peritonitis in CAPD patients, with a frequency of 10 to 15% [10]. Usually the organism isolated belongs to the {alpha}- haemolytic variety. The most frequent agents are viridans streptococci (Streptococcus sanguis, S. mitis, S. salivarius, S. bovis, S. constellatus) [11]. These infections are probably caused by spread via a haematogenous route, e.g. after dental work [12] or direct intraluminal infection [13] from the oral flora. As the streptococcus species is rarely found on the skin, it is doubtful whether these microbes enter through the catheter exit site [14]. Streptococcus faecalis peritonitis indicates faecal contamination [11].

Five cases of S. agalactiae peritonitis in chronic peritoneal dialysis patients have been reported in the literature [47]. In four cases of S. agalactiae peritonitis described in CAPD patients, the course was severe, i.e. two children who developed septic shock [4], a 52-year-old male who developed fatal septic shock complicated by a pleuroperitoneal fistula [5], a 63-year-old man who presented with septic shock and bacteraemia [6], and a 25-year-old patient admitted with stupor, in whom blood cultures remained negative [7]. The evolution in the last two patients was favourable. Schröder et al. [4] underlined the similarities of severe peritonitis from GBS with group B ß-haemolytic streptococcal disease in neonates [15], and discussed a role of IgG2 deficiency which has been reported in children treated with CAPD [16]. This immunoglobulin interacts with the type-specific polysaccharide antigens of group B streptococci. An IgG2 deficit cannot explain the severity of GBS peritonitis in adults, however, as abnormal levels of IgG2 were never demonstrated in adult patients. In general, CAPD peritonitis is rarely accompanied by bacteraemia. In our opinion, the high mortality of GBS peritonitis in CAPD patients [47], as well as of other GBS infections [15], is the result of bacteraemia.

The favourable course in the cases of Yinnon et al. [6] and Pagniez et al. [7] was presumably due to the fact that treatment was begun within few hours after the dialysate had turned cloudy and before the onset of severe systemic symptoms.

The most active antibiotics in treating GBS are penicillin G, third-generation cephalosporins, and meropenem [17]. Penicillin G is an excellent antibiotic for the treatment of GBS peritonitis because of its lower cost, proven safety, efficacy, and narrow spectrum of antimicrobial activity. Its extensive use for intrapartum chemoprophylaxis may lead to chemoresistance; however, ceftriazone, cefamandole, cefotaxime, and meropenem are as effective as penicillin G and more effective than cephalothin, rifampicin, and vancomycin [17]. The use of second- and third-generation cephalosporins and meropenem is recommended in case of penicillin G allergy [17]. Macrolides should be avoided in GBS because of their widespread use for gynaecological infections [18].

Streptococcus agalactiae is a facultative member of the normal flora of the female genital tract. Contamination and even infection of the peritoneal fluid of female CAPD patients caused by retrograde menstruation have been described [19,20]. In the case we report here the recovery of this micro-organism from the vaginal swab sample of the patient during the episode of peritoneal infection suggests a possible ascending contamination of the peritoneum from the genital tract, eventually favoured by sexual intercourse within the menstrual period.



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Received for publication: 6. 4.99
Accepted in revised form: 14. 5.99