A critical review of the antibody-coated bacteria test.

Reports extolling the virtues of the antibody-coated bacteria immunofluorescent test continue to appear and therapeutic decisions are being made on the results of this test. In this review 2 unresolved issues are examined: 1) what constitutes a positive test and 2) how accurately does the antibody-coated bacteria test define the tissue source of infection. These issues should be resolved before all clinicians and researchers jump on the antibody-coated bacteria test bandwagon.     

Epididymitis as cause of antibody-coated bacteria in urine.

The antibody-coated bacteria (ACB) immunofluorescence test has emerged as the preferred noninvasive technique to distinguish reliably between pyelonephritis and cystitis. Investigators have recently correlated a positive test with chronic bacterial prostatitis and cystitis complicating a bladder tumor or stone. We present data that appear to prove that acute bacterial epididymitis associated with bacteriuria can also evoke a positive ACB determination.     

Clinical significance of the antibody-coated bacteria test in patients with candiduria

The clinical significance of the antibody-coated bacteria (ACB) test was evaluated with urine from 20 patients with candiduria. The relationship between the in vitro antibody-coating test for Candida albicans, urinary immunoglobulin (Ig) levels and serum antibody titres was evaluated in 40 patients without candiduria, 23 of whom had bacterial urinary tract infection (UTI). Urine specimens from 19 of the 20 patients with candiduria gave a positive result regardless of clinical symptoms; 12/23 specimens of urine from patients with bacterial UTI were positive for antibody-coated C. albicans cells, but there were no positive samples in the patients without UTI. All of the coating-positive patients had serum antibody titres greater than or equal to 1:160, the class of antibody being dependent on the urinary Ig levels. The ACB test for candiduria is of little clinical value in indicating invasive Candida UTI as the Candida cells appear to adhere to antibodies in urine contaminated with circulating fluids.     

India ink immune method for the study of antibody-coated urinary bacteria

The sediments of 373 urines were studied for antibody-coated bacteria by the India ink immune method. Positive results were obtained in 14.7 per cent of upper urinary tract infections, 18.9 per c nt of lower urinary tract infections, 29 per cent of bacteriuria, and 15.2 per cent in healthy girls. Since antibody-coated bacteria could find their way into negative urines only by contamination, 296 vulvar secretions were also examined. Positive results were obtained in 15.5 per cent of girls with urinary tract infections, 63.9 per cent of those with vulvitis and 24.1 per cent in girls with no infection. It is concluded from the results that the presence or absence of antibody-coated bacteria in the urine is unrelated to the site of urinary infection.     

Do antibody-coated bacteria reflect local immune response in the urinary tract?

We examined whether antibody-coated bacteria (ACB) reflect local immune response or passive adsorption of immune globulins (Ig). For this purpose, bacterial subcultures from infected urines and third-party bacteria were incubated with Ig preparations. These were obtained from infected urine either by removal of Ig from ACB (dissociation in alpha-methylmannoside, 0.1 M glycine-HCl, or 3 M NaSCN) or by staphylococcal protein A affinity chromatography from the supernatant of infected urine. Coincubation of either Ig preparation with bacterial substrains of the original urine and with third-party strains (Pseudomonas aeruginosa, Proteus mirabilis, several Escherichia coli strains, enterococci, Serratia marcescens, Klebsiella pneumoniae, Staphylococcus aureus) caused coating of the bacterial surface with Ig. Coating was not measurably influenced by coincubation with various carbohydrates or by preincubation of bacteria with glucosidases. Adsorption of Ig was observed after heat denaturation and formalin treatment of bacteria and was independent of bacterial growth phase. Coating was observed both with intact IgG and with F(ab)2 fragments. We further examined the proportion of bacteria coated with IgA, IgG, and IgM in urines of 200 bacteriuric women with symptomatic urinary tract infection. The frequency histogram plot showed a continuous nonlinear unimodal distribution. Consequently, any selection of a 'normal range' is arbitrary. It is concluded that coating of the bacterial surface with Ig may not necessarily reflect local immune response. A major problem of the ACB test is definition of the normal range.     

Clinical and laboratory evaluation of the antibody-coated bacteria test in children.

The antibody-coated bacteria test can distinguish upper from lower urinary tract infection. In this study 67 bacteriuric children were selected from meningomyelocele and urology clinics. There was close correlation between radiological evidence of upper tract changes and the presence of antibody-coated bacteria. There was a distinct lack of correlation between serum antibody titers to the infecting organism and antibody-coated bacteria. In vitro laboratory studies indicated that 1) antibody coating in the urine occurred immediately upon exposure of the infecting isolate to the urine of the patient, 2) only the homologous isolate was coated and 3) the pH range for antibody coating was wide (pH 4.0 to 9.0).     

Correlation of antibody-coated bacteria with intravenous pyelogram in children with refluxing and nonrefluxing units

A fluorescent technique for detecting immune globulins on the surface of urinary bacteria has been used to differentiate upper from lower urinary tract infections. In an attempt to correlate positive fluorescence with deteriorative changes on the intravenous pyelogram, a total of 79 pediatric patients was studied. Twenty-three had ileal conduits with freely refluxing urine. The remaining 56 children had intact urinary tracts. Thirty of these had vesicoureteral reflux. Urine cultures were studied in conjunction with fluorescent antibody determinations. In patients with significant bacteriuria good correlation was seen with the presence of bacterial fluorescence and positive renal changes. This correlation was 88 per cent in patients with bowel conduits, 71 per cent in patients with vesicoureteral reflux, and 38 per cent in patients without reflux. Possible false positive and false negative results were relatively low, each occurred in 10 per cent of the specimens examined. It is concluded that the combination of urinary tract infection and positive bacterial fluorescence is seen when upper tract deterioration has occurred and is seen most frequently in association with urinary reflux. In these instances aggressive therapy is often indicated.     

Localization of catheter-induced urinary tract infections: interpretation of bladder washout and antibody-coated bacteria tests

Accurate differentiation of upper from lower urinary tract infection (UTI) has been reported based on the presence or absence of antibody-coated bacteria (ACB) in the urinary sediment. The specificity of ACB localization in adults has been reported to be high based on a strong correlation with localization results obtained with the bladder washout technique. The present study examines the efficacy of ACB testing with respect to accurate anatomic localization of UTI in 20 studies in 14 patients exhibiting bacteriuria as a result of chronic urethral catheterization. 17 studies (85%) demonstrated significant ACB. Localization of UTI was assessed in each study by the bladder washout technique. Following instillation of a washout solution, a normal decrease in colony counts was observed in only 3 studies (15%), a frequency significantly lower than the value of 90% previously reported in noncatheterized bacteriuric patients (p less than 0.001). Each of these 3 patients was ACB-positive, yet anatomic localization indicated lower tract UTI. The observed characteristics of the 14 patients included the absence of upper tract signs and symptoms, and spontaneous clearing of ACB and bacteriuria following catheter removal. These findings suggest that in chronically catheterized patients, both (1) the observed abnormal resistance of bacteria to bladder washout and (2) the high frequency of positive ACB tests are indices of severe chronic tissue invasion and intense antibody production in the lower urinary tract in this condition and thus not of value in localizing infection to the upper tract. Neither ACB nor washout testing with current techniques can reliably localize UTI in chronically catheterized patients.     

Failure of antibody-coated bacteria and bladder washout tests to localize infection in spinal cord injury patients

The validity of the antibody-coated bacteria test and Fairley washout procedure to determine whether urinary tract infections were of kidney or bladder origin in spinal cord injury patients was assessed by comparing test results with those obtained from culture of ureteral urine specimens. It was concluded that neither the presence of antibody-coated bacteria nor a positive bladder washout test can be considered as definitive evidence that bacteriuria is of renal origin in these patients.     

Treatment of urinary tract infections by cefaclor, with special reference to the antibody-coated bacteria (ACB) detected by the immunoenzyme technique

Twenty out-patients suffering from urinary tract infections (UTI) were treated with cefaclor. Cefaclor was administrated orally in daily doses of 1,500 mg for 7 days against 15 cases of simple UTI and 5 cases of complicated UTI. Of 20 cases with acute simple cystitis, acute pyelonephritis and complicated UTI, clinical responses were excellent in 10 cases, good in 6 cases and poor in 4 cases. The efficacy rate was 80%. No side effect was observed. The site of infection determined by the ACB detection method was in good agreement with that determined by clinical findings. Cefaclor appeared to be equally effective in the treatment of both ACB-positive and ACB-negative infections. The presence of absence of antibody-coated bacteria did not correlate with clinical symptoms or response to therapy.     

In vitro adherence of bacteria to prosthetic grafting materials

Adherence of bacteria to prosthetic grafting material is thought to play an important role in the ultimate development of prosthetic infections. To evaluate the role of bacterial adherence in the initiation and colonization of prosthetic materials, Proplast II, Gore-Tex, and silicone were evaluated for adherence of Escherichia coli and Staphylococcus aureus. Bacteria were radio labeled and incubated with the study material. Adherence was determined by scintillation. Adherence to Proplast II and Gore-Tex reached a maximum at approximately 45 minutes of incubation and demonstrated a detachment phenomenon with E. coli. Similar results were noted with S. aureus, but with a maximal attachment at approximately 30 minutes. Interestingly, bacterial attachment to silicone continued to increase throughout the time of the incubation. In addition, adherence of S. aureus was at a faster rate than E. coli. Attachment of bacteria is a multifactorial process. However, the PTFE graft demonstrates a slower rate of attachment, lower total number of attached bacteria, and faster detachment. The importance of this phenomenon may help explain the foreign body effect of increased susceptibility to infection of foreign materials.     

In vitro quantitative adherence of bacteria to intravascular catheters

Adapting standard techniques, a simple in vitro system was devised to compare quantitative bacterial adherence to iv catheters of different compositions. Upon brief immersion of catheters in suspensions of Staphylococcus aureus, coagulase-negative staphylococci, and Escherichia coli, organisms adhered to catheter surfaces. After overnight growth in broth, organisms remained adherent and formed colonies, as shown by light and scanning electron microscopy. In addition, quantitative adherence using a blood agar roll technique, expressed as bacteria per square centimeter of catheter surface area per 10(6) colonies per milliliter inoculum, was calculated. Adherence was greater on polyvinylchloride (PVC) catheters (geometric mean 342) than on Teflon catheters (geometric mean 49.6) for coagulase-negative staphylococci (P less than 0.005). Also, the number of coagulase-negative staphylococci adherent to PVC catheters was significantly greater than for E. coli (geometric mean 70.6) at analogous inocula (P less than 0.02). Differences in bacterial adherence to the surface of iv devices may be important in the pathogenesis of catheter-associated infections. This in vitro method could prove useful in testing bacterial adherence properties of newly developed catheter materials, and allow development of catheters less prone to be associated with bacterial adherence and catheter-related infections.     

In vitro adherence of bacteria to sutures in cardiac surgery

The adherence of bacteria to sutures used in cardiac surgery was studied by in vitro quantitative determination with [3H]-leucine-labeled Staphylococcus epidermidis, Staphylococcus aureus and Streptococcus sanguis. The adherence per unit area for staphylococci was least for monofilament polypropylene (Prolene), 3 times higher (p less than 0.05) for braided polyester (Mersiline) and greatest (10 times, p less than 0.005) for braided polyester sutures coated with polybutylate (Ethibond). Mean values for the adherence of streptococci were low for all the sutures. Sutures pretreated with human plasma showed a 12-37% increase in bacterial adherence. The cell surface hydrophobicity, surface charge and the haemagglutinating property of bacteria did not correlate with their adherence property. In view of these observations, it is suggested that: (a) the preferential adherence of staphylococci to intra-cardiac sutures may be one of the explanations for its being the commonest cause of early prosthetic valve endocarditis, (b) there is a need for a careful selection of sutures used in cardiac surgery and (c) the described in vitro assay for bacterial adherence may be used for monitoring the development of better designed sutures and the effect of incorporation of antibiotics in the sutures.     

In vitro antibiotic susceptibility of bacteria isolated from prostatic fluid.

Bacterial isolates from expressed prostatic secretions were tested in vitro for susceptibility to five antimicrobial agents used in the treatment of prostatitis. Comparisons of susceptibility and resistance were made between minocycline and each of the other four agents: tetracycline, cephalexin, ampicillin, and trimethoprim-sulfamethoxazole. A high percentage of the isolates from patients with prostatitis which were resistant to tetracycline and trimethoprimsulfamethoxazole were susceptible to minocycline.