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PubMed1993

[Evaluation of the serum bactericidal test].

The serum bactericidal test (SBT) is used to monitor antibiotic treatment during therapy. Compared to other methods of sensitivity testing, such as MIC (minimum inhibitory concentration) determination, the SBT also takes into consideration the pharmacokinetic qualities of the drug tested. Serum bactericidal titers are measured during therapy of different infectious diseases to estimate therapeutic outcome. Until now serum bactericidal titers of 1:8 in non-granulocytopenic patients, and titers > or = 1:16 in granulocytopenic patients have been shown to correlate with a successful treatment outcome in patients with gram-negative sepsis. In patients with endocarditis a peak serum bactericidal titer of at least 1:32 should be achieved. Another way to apply the serum bactericidal test is to compare the activity of different antibiotics in volunteers. The present study as well as data from the literature indicate that ciprofloxacin has markedly higher serum bactericidal activity than ofloxacin. Of the so called "basic cephalosporins" cefotiam achieved the highest serum bactericidal activity against the Enterobacteriaceae tested. Since 3rd generation cephalosporins are in general highly active against gram-negative rods, we were interested in using the SBT to compare different dosage regimens. In several studies serum bactericidal titers of > or = 1:8 were achieved with the 1 g dosis of cefotaxime, cefmenoxime and especially ceftazidime against the gram-negative rods tested.

Agranulocytosis↗

PubMed1988

Serum bactericidal test.

The serum bactericidal test represents one of the few in vitro tests performed in the clinical microbiology laboratory that combines the interaction of the pathogen, the antimicrobial agent, and the patient. Although the use of such a test antedates the antimicrobial era, its performance, results, and interpretation have been subject to question and controversy. Much of the confusion concerning the serum bactericidal test can be avoided by an understanding of the various factors which influence bactericidal testing. In addition, the methodologic aspects of the serum bactericidal test have recently been addressed and should place this test on firmer ground. New information on the clinical utility of this test is becoming available; additional data are needed to establish more clearly the usefulness of the serum bactericidal test in specific infections. Such clinical trials from multiple centers will enable firmer recommendations for the future use of the serum bactericidal test.

Anti-Bacterial Agents↗

PubMedDate not supplied

The serum bactericidal test.

The serum bactericidal test (SBT) has been used for almost 40 years to monitor therapy in patients with bacterial endocarditis, osteomyelitis, and other serious infections. The SBT is basically a variation of the broth dilution test adapted to assess the activity of a treated patient's own serum against the infecting microorganism. Only recently, however, have rigorous attempts been made to standardize all the relevant variables that affect results of the SBT. The widely recommended goal of a peak bactericidal titer of 1:8 in the therapy for infective endocarditis may be inadequate for the treatment of some patients. Peak titers of 1:64 or greater in the microdilution SBT should be sought if they can be achieved without toxicity. Titers of less than 1:8 may be acceptable, although they are less often successful, if serious toxicity would result from increased dosage. Peak SBT titers of 1:8 or greater yield high cure rates for acute osteomyelitis in children; data are limited in adults. A defined SBT method is necessary for additional multicenter clinical trials on which firmer recommendations for its future use can be made.

Anti-Bacterial Agents↗

PubMed1992

[Evaluation of the so-called basic cephalosporins using the serum bactericidal test].

The serum bactericidal activity (SBA) was studied one hour and four hours after intravenous administration of 1 g and 2 g cefotiam, 1.5 g cefuroxime and 2 g cefazolin to six volunteers. The 136 clinical isolates tested included Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Haemophilus influenzae. One hour after administration no significant differences in the activity against staphylococci were noted in the antibiotics tested. Four hours after administration of cefazolin 96% of the Staphylococcus aureus strains were killed at a serum dilution of 1:8, whereas only one strain was killed by cefuroxime and none by cefotiam under the same conditions. The highest SBA-titers against Haemophilus influenzae were achieved with cefotiam at a dosage of 2 g. SBA-titers against Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis were higher after administration of 1 g cefotiam than after administration of 1.5 g cefuroxime and 2 g cefazolin, respectively.

Blood Bactericidal Activity↗

PubMed1991

The activity of clarithromycin and its 14-hydroxy metabolite against Haemophilus influenzae, determined by in-vitro and serum bactericidal tests.

The in-vitro activity of clarithromycin and its main metabolite 14-hydroxy clarithromycin against Haemophilus influenzae was evaluated by determining minimum inhibitory and minimum bactericidal concentrations. The 14-hydroxy metabolite was more active than the parent compound against H. influenzae. The activity of the parent compound/metabolite combination was evaluated against 20 strains of H. influenzae by the chequerboard technique. The combination was synergistic against seven isolates in terms of fractional bactericidal concentration index and against five isolates in terms of fractional inhibitory concentration index; the combination demonstrated additive activity against the remaining strains. Serum bactericidal activity against H. influenzae was measured in sera from six healthy volunteers who had received 250 mg clarithromycin by mouth. The area under the serum bactericidal activity curve correlated with the area under the curves for clarithromycin and 14-hydroxy clarithromycin, and with the in-vitro susceptibility of the strains tested. Serum bactericidal activity was detected at 30 min after dosing and lasted for 5-6 h.

Clarithromycin↗

PubMed2001

Effect of serum from different patient populations on the serum bactericidal test.

We evaluated the effect of serum from normal and uraemic volunteers, neutropenic patients and burn patients on the serum bactericidal test. Serum samples were spiked with ceftazidime to mimic in vivo peak (75 mg/L) and trough (5 mg/L) concentrations. Serum inhibitory and bactericidal titres (SIT and SBT) were performed in triplicate using Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. For E. coli, the trough SIT and SBT were significantly higher in serum from burn patients compared with normal volunteers (P < or = 0.024). The trough SIT was significantly higher in serum from burn patients compared with neutropenic patients (P = 0.022) and in uraemic patients compared with normal volunteers (P = 0.04). No significant differences between subject populations were found for P. aeruginosa.

Adult↗

PubMed1986

Evaluation of novel antipseudomonal drugs using the serum bactericidal activity test.

Serum bactericidal activity against Pseudomonas aeruginosa was determined in six volunteers 1 and 4 h after administration of 2 g ceftazidime, 4 g piperacillin, 500 mg imipenem, 80 mg tobramycin and four combinations of these agents. Ceftazidime produced the highest serum bactericidal titers, killing 100% and 86% of the 50 Pseudomonas aeruginosa strains tested after 1 and 4 h respectively at a serum dilution of 1:8. Imipenem had lower serum bactericidal titers than ceftazidime, killing 88% of the isolates after 1 h at a serum dilution of 1:8. The combination showed only slightly higher titers. Killing curves were determined for nine strains of Pseudomonas aeruginosa using undiluted volunteer serum drawn 1 h after administration of the antibiotics. The combinations ceftazidime/tobramycin and piperacillin/tobramycin exhibited higher killing activity than the single drugs. As the activity of the aminoglycosides could be underestimated on the basis of their low serum bactericidal titers, it is concluded that determination of these titers is inappropriate for evaluating the efficacy of the aminoglycosides.

Ceftazidime↗

PubMed1986

Serum bactericidal testing with the Autobac system.

Current methodology for the serum bactericidal test requires a minimum of 48 h. A procedure was devised for performing this test with the Autobac system (General Diagnostics, Div. Organon Inc., Raleigh, N.C.) in a shortened time span. All titers obtained with the Autobac were compared against results obtained with a standardized tube dilution procedure. The Autobac low-thymidine eugonic broth performed comparably to the tube dilution diluent, a 1:1 ratio of pooled human serum and cation-supplemented Mueller-Hinton broth (99.2% correlation between bactericidal endpoints). Over 300 tests were conducted by using stock reference bacterial strains, clinical isolates, pooled human serum seeded with antimicrobial agents, and serum from patients on antimicrobial therapy. With the Autobac procedure, serum inhibitory titers can be reported in 3 to 4 h (93.4% correlation with the tube dilution procedure). Serum bactericidal titers can be obtained in 24 h without the necessity of subculturing (95.6% correlation). With the exception of staphylococci tested against penicillin, serum bactericidal titers can be obtained in 3 to 4 h (88.4% correlation). The Autobac procedure can provide the clinical laboratory with a rapid, reliable method for performing the serum bactericidal test.

Anti-Bacterial Agents↗

PubMed1979

Comparison of a micromethod for performance of the serum bactericidal test with the standard tube dilution method.

A micromethod for performance of the serum bactericidal test is described, and the results obtained with this method are compared with those obtained with the standard tube dilution macromethod. An agreement within +/- 1 dilution was achieved in 23 of 25 (92%) determinations of the serum bactericidal titer. The micromethod used approximately one-third of the amount of pooled normal human serum and of the technician's time required for performance of the macromethod. The micromethod offers an accurate and economical alternative to the macromethod for the performance of the serum bactericidal test and is particularly useful with infants and children since it minimizes blood loss.

Anti-Bacterial Agents↗

PubMed1986

Technical aspects and clinical correlations of the serum bactericidal test.

A review of the studies using 50% human serum as a diluent for the serum bactericidal test has shown correlations with patient outcome. Human serum used as diluent of the patient's serum appears to be essential because of high protein binding of some antibiotics. An inoculum of 10(5)-10(6) bacteria/ml and a bactericidal criteria of 99.9% killing are technical aspects that have gained popularity. Careful timing of serum collection for the assay is important. Neither the macrotube nor microtiter techniques are entirely satisfactory. The latter method, however, has the advantage of being more reproducible than the macrotube method, less cumbersome and requiring less serum. Preliminary guidelines for performing and interpreting the test are provided. Future research should be directed toward making the microtiter technique more sensitive for identifying antibiotic tolerance, developing effective methods to eliminate the need for human serum as a diluent and obtaining more clinical correlations.

Anti-Bacterial Agents↗

PubMed1985

Multicenter collaborative evaluation of a standardized serum bactericidal test as a prognostic indicator in infective endocarditis.

One hundred twenty-nine patients with bacterial endocarditis were evaluated in a multicenter collaborative study to determine whether a standardized serum bactericidal test could predict the outcome of the infection. All centers used a microdilution test method that defined all known test variables, including inoculum size, culture medium, dilution technique, incubation time, method of subculture, and bactericidal endpoint. Peak serum bactericidal titers of 1:64 or more and trough serum bactericidal titers of 1:32 or more predicted bacteriologic cure in all patients. The traditionally recommended serum bactericidal titer of 1:8 had statistically significant predictive accuracy at trough antibiotic levels only. The serum bactericidal test was a poor predictor of bacteriologic failure and ultimate clinical outcome, which depends on many factors. Wider recognition by physicians and clinical microbiologists that this in vitro test of antimicrobial activity can accurately predict bacteriologic success but cannot accurately predict either bacteriologic failure or clinical outcome could lead to a better consensus about its appropriate use. On the basis of the results of this study, peak serum bactericidal titers of 1:64 or more and trough serum bactericidal titers of 1:32 or more are recommended to provide optimal medical therapy for infective endocarditis.

Adolescent↗

PubMed1993

Serum bactericidal test as a prognostic indicator in acute pulmonary exacerbations of cystic fibrosis.

The serum bactericidal test has been used for many years for optimal assessment of the efficacy of antibiotic therapy in patients with infective endocarditis and other bacterial infections. Its capacity to predict the bacteriological outcome of acute pulmonary exacerbations in patients with cystic fibrosis was evaluated. A total of 54 courses of intravenous antibiotic therapy were analyzed in 22 patients, whose ages ranged from 4 months to 24 years (mean age: 10 years). The serum bactericidal activity of blood samples, taken at expected peak and trough antibiotic levels on day 4 of therapy, were determined against the potentially pathogenic strains isolated in sputum at the time of admission. For 104 isolates (64 Pseudomonas aeruginosa, 28 Staphylococcus aureus, and 12 Haemophilus influenzae strains), the peak and trough bactericidal titers were compared to bacteriological outcome. Bacteriological success was defined as a decrease of 2 log10 units or more in the bacterial density in sputum between days 0 and 7 of therapy. At peak antibiotic levels, serum bactericidal titers of 1:128 or more were 96% (all isolates) and 89% (P aeruginosa isolates), predictive of cure, whereas serum bactericidal titers of less than 1:16 were 100% predictive of failure for all infecting bacteria. In patients aged less than 18 years, the best peak titer for predicting success was 1:64, with a predictive value of 96% for titers of 1:64 or greater. The peak titer that best predicted success in patients aged 18 years or more was 1:128, with a predictive value of only 83% for titers of 1:128 or greater.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1974

Variation in performance of the serum bactericidal test.

Questionnaires were sent to 37 diagnostic microbiology laboratories to assess their methods for performance of the serum bactericidal test. Of the 28 responding laboratories, 26 utilized the test, with considerable variation among methods. Culture and dilution media included Trypticase soy, Mueller-Hinton, brain heart infusion, Columbia broth, dextrose phosphate, and pooled human serum. Several different schemes for dilution of the test serum were employed, including both micro and macro methods. The greatest variation occurred in the size of the bacterial inoculum, with only eight laboratories having a method for standardization of the inoculum. Other differences included the time of incubation, the method of subculture, and determination of the bactericidal end point. These studies emphasize the need for assessment of the variables in the performance of this test and for the development of a standard method for diagnostic laboratories.

Blood Bactericidal Activity↗

PubMed1987

Multicenter collaborative evaluation of a standardized serum bactericidal test as a predictor of therapeutic efficacy in acute and chronic osteomyelitis.

Forty-eight episodes of osteomyelitis, 30 acute and 18 chronic, were evaluated in a prospective multicenter collaborative study to determine whether a standardized serum bactericidal test could predict outcome of infection. All centers used a microdilution test method that defined the recognized important test variables, including inoculum size, culture medium, dilution technique, incubation time, method of subculture, and bactericidal endpoint. In patients with acute osteomyelitis, peak serum bactericidal titers had no predictive value; however, trough titers of 1:2 or greater accurately predicted cure, whereas trough titers of less than 1:2 predicted therapeutic failure. In patients with chronic osteomyelitis, peak serum bactericidal titers of 1:16 or greater and trough titers of 1:4 or greater accurately predicted cure, whereas peak titers of less than 1:16 and trough titers of less than 1:2 accurately predicted failure. It is concluded that this standardized serum bactericidal test provides good prognostic information in patients with osteomyelitis, and it is recommended that patients with acute osteomyelitis have serum bactericidal titers of 1:2 or greater at all times and that patients with chronic osteomyelitis have serum bactericidal titers of 1:4 or greater at all times.

Acute Disease↗

PubMed1986

Serum bactericidal test in volunteers--a review.

A review is given of work utilizing the serum bactericidal test for preclinical evaluation of agents considered for treatment of gram-negative sepsis among neutropenic cancer patients. Following a description of the methodology of the two major groups, the results of the various antibiotic trials are summarized. First the extended-spectrum cephalosporins (cefotaxime, cefoperazone, and moxalactam) were tested and found to be, at best, of limited value as single agents for Pseudomonas aeruginosa, a common pathogen of neutropenic cancer patients. When the extended-spectrum penicillins became available, the serum bactericidal levels in volunteers of mezlocillin and piperacillin were compared alone or in combination with an aminoglycoside to ticarcillin with or without aminoglycoside against the same organisms. Piperacillin proved to be most effective followed by mezlocillin and then ticarcillin; in each case the addition of the aminoglycoside improved serum bactericidal activity. Recent studies suggest that imipenem alone is as active as the combination of a broad-spectrum penicillin plus an aminoglycoside and is worthy of a carefully controlled clinical trial. These types of volunteer-based evaluations of the serum bactericidal activity of new compounds may help predict useful clinical approaches for the future.

Adult↗

PubMed1978

Comparison of antigenic heterogeneity of Neisseria gonorrhoeae strains by micro-immunofluorescence and serum bactericidal tests.

The antigenic heterogeneity of Neisseria gonorrhoeae strains was assessed by the micro-immunofluorescence (micro-IF) and the serum bactericidal tests. The micro-IF test verified the antigenic heterogeneity of nine strains received from the Center for Disease Control and placed them into immunotypes A and B. The serum bactericidal system also detected different antigenic determinants among the strains. Although the micro-IF and bactericidal assays did not correspond in each instance, the overall pattern of similarities and differences among these gonococcal strains was similar. The micro-IF pattern obtained with mouse antisera was identical to the pattern revealed with guinea pig antisera. Different colony type organisms showed similar sensitivity in the bactericidal test. The micro-IF test is a rapid technique for the immunotyping of N. gonorrhoeae and has the additional advantages of reproducibility and simplicity.

Animals↗

PubMed1997

External quality assessment of the serum bactericidal test: results of a methodology/interpretation questionnaire.

Two hundred microbiology laboratories in the UK took part in two separate experimental external quality assessment distributions related to the serum bactericidal test (SBT). In the first, Staphylococcus aureus NCTC 6571 (vancomycin MIC 1 mg/L), was tested against a human serum containing vancomycin 38 mg/L plus gentamicin 0.5 mg/L. In the second, Streptococcus oralis PAJ 112/4183 (penicillin MBC < or = 0.03 mg/L) and Streptococcus sanguis PAJ 107/4184 (penicillin MBC = 128 mg/L) were tested against human serum containing penicillin 15 mg/L. Respondents returned their laboratory results and a questionnaire on clinical interpretation and technical aspects. Most laboratories (194/199, 97.5%) recommend the use of the SBT in the management of infective endocarditis but only 48 (25.2%) often or always change therapy on the basis of the result. A wide range of interpretative criteria, definitions of bactericidal endpoints and methodologies are used. Performance in the first distribution was acceptable for 75% of laboratories but in the second only 34% could identify penicillin tolerance; 34 respondents reported an SBT result of < or = 2 for the tolerant strain, 81 laboratories reported one of > or = 16. Technical factors related to acceptable performance were: sonication of broth before counting the inoculum; knowing the inoculum size in cfu/mL; use of a 4-8 h broth culture to make the inoculum; incubation of recovery plates for > 36 h; use of a calibrated pipette to sample for surviving bacteria; use of measured volumes to add the inoculum. Use of uncalibrated pipettes or standard loops to recover survivors was related to poor performance. Microbiology departments in the UK should review the clinical need to perform the SBT in the light of their local circumstances and if they elect to continue to offer this test, revise their methodologies which could be producing misleading results when testing alpha-haemolytic streptococci.

Bacteriological Techniques↗

PubMed1976

Ovine campylobacterosis: preliminary studies of the efficacy of the in vitro serum bactericidal test as an assay for the potency of Campylobacter (Vibrio) fetus subsp intestinalis bacterins.

An in vitro serum bactericidal test was developed to assess the efficacy of Campylobacter fetus bacterins. Four experimental monovalent bacterins (either serotype C or A-2) and 2 commercial bivalent bacterins (a "suspect" and an "efficacious" bacterin) with aluminum hydroxide adjuvant were administered to sheep and rabbits from which antiserums were then prepared. The different vaccines were evaluated by comparing the in vitro bactericidal activity of the sheep and rabbit antiserums. Results of the in vitro tests were compared to the protection induced in vaccinated ewes which were orally exposed to C fetus. The sheep and the rabbit antiserums after they were heated at 56 C for 30 minutes were unable to exert a killing effect on C fetus cells. Addition of a fresh homologous complement source to the heated antiserums was necessary to demonstrate the in vitro bactericidal capacity. In the comparison of the suspect and the efficacious commercial bacterins, which both reportedly contain serotype C cells, there was a statistically significant difference in bactericidal activities for serotype C cells of antiserums from sheep 14 days after the 2nd vaccination. There was a corresponding significant difference in the antiserums from rabbits 14 days after the 2nd vaccination. Proportionally, more abortions and stillbirths were observed in the ewes vaccinated with the suspect bacterin and then orally exposed to C fetus-serotype C cells than in those vaccinated with the efficacious bacterin. The results indicated that the ability of vaccinated sheep to overcome infection is reflected in the in vitro bactericidal capacity of antiserum from the animal. Since 89% of the variation in sheep antiserums from 14 days after 2nd vaccination can be accounted for by rabbit antiserums from 14 days after 2nd vaccination, the in vitro bactericidal capacity of rabbit antiserums probably provides a reliable index of the protective effect of bacterins containing serotype C for ewes exposed to the homologous serotype.

Abortion, Veterinary↗