Performance of a BACTEC nonradiometric medium for pediatric blood cultures

Antibiotic therapy alone does not have a high success rate in cases of unexpected positive cultures in intraoperative samples from hip and knee prosthesis revision

BACKGROUND

Unexpectedly positive bacterial cultures during prosthesis revision surgery still occur on occasion despite good preoperative diagnostics. In such cases a six-week antibiotic therapy without further surgical intervention is recommended. The aim of this study was to find out how successful this procedure is.

METHODS

In a study of 508 patients, who required revision surgery of total hip (THA, n = 231) or knee arthroplasties (TKA, n = 277) because of component loosening, biopsy was carried out before their surgery. The collected tissue samples (5) from the biopsy and the revision surgery procedure itself were analyzed according the criteria of the International Consensus Meeting (ICM). Tests revealed 11 patients (7 THA, 4 TKA) with unexpectedly positive bacterial cultures from tissue samples obtained during the revision surgery due to false negative preoperative diagnostic results. These 11 patients were treated with 6 weeks antibiotic therapy and examined with a follow-up of at least 2 years (42.2 ± 16.5 months).

RESULTS

Five patients (2 TKA, 3 THA) became reinfected, resulting in a success rate of 54.5%.

CONCLUSION

Antibiotic therapy alone of an unexpected positive intraoperative bacterial culture in prosthesis revision surgery seems to be less successful than previously assumed.

Evaluation of Antibiotic Resistance Pattern in Dental Bacteremia Detected by Multiplex PCR Technique

The aim of this study was to detect oral bacteremia and offer the antibiotic resistance patterns. Bacterial resistance pattern was evaluated in 50 patients. A spectrophotometer device equipped with UV and electrophoresis of the extracted samples on agarose gel for antibiogram test were used. PCR test 15 minutes after tooth extraction showed that bacterial strains were extracted from 16 patients. Lactobacillus, Enterococcus faecalis (E. faecalis), Streptococcus sanguinis (S. sanguinis), Streptococcus salivarius (S. salivarius), and Streptococcus mutans (S. mutans) were extracted from 5, 4, 4, 4, and 6 patients. 100% of Lactobacillus, E. faecalis, S. sanguinis, S. salivarius, and S. mutans were sensitive to tigecycline. Most of the Lactobacillus antibiotic resistance was against tetracycline and ciprofloxacin. Antibiotic resistance in S. salivarius was observed in 75% of the cases against piperacillin-tazobactam, ciprofloxacin, and cefotaxime, while in S. mutans was 84% of the cases against ceftriaxone. The results of the current study showed that tooth extraction causes bacteremia before, during, and after tooth extraction. Generally, the highest antibiotic resistance occurred against tetracycline, ciprofloxacin, and ampicillin-sulbactam. In most cases, the bacteria showed partial resistance to these antibiotics; however, tigecycline showed 100% efficacy on all types of bacteria. Streptococcus strains (salivarius, mutans, and sanguinis) were sensitive to most of the antibiotics while antibiotic sensitivity was less evident in Lactobacillus and E. faecalis. Antibiotic resistance has become a critical issue, since it leads to treatment failure when there is a need for antibiotic therapy.

The diagnostic value of routine preliminary biopsy in diagnosing late prosthetic joint infection after hip and knee arthroplasty

AIMS

Biopsy of the periprosthetic tissue is an important diagnostic tool for prosthetic joint infection (PJI) as it enables the detection of the responsible microorganism with its sensitivity to antibiotics. We aimed to investigate how often the bacteria identified in the tissue analysis differed between samples obtained from preoperative biopsy and intraoperative revision surgery in cases of late PJI; and whether there was a therapeutic consequence.

METHODS

A total of 508 patients who required revision surgery of total hip arthroplasty (THA) (n = 231) or total knee arthroplasty (TKA) (n = 277) because of component loosening underwent biopsy before revision surgery. The tissue samples collected at biopsy and during revision surgery were analyzed according to the criteria of the Musculoskeletal Infection Society (MSIS).

RESULTS

In total, 178 (113 THA, 65 TKA) were classified as infected. The biopsy procedure had a sensitivity of 93.8%, a specificity of 97.3%, a positive predictive value (PPV) of 94.9%, a negative predictive value (NPV) of 96.7%, and an accuracy of 96.1%. Of the 178 infected patients, 26 showed a difference in the detected bacteria from the biopsy and the revision surgery (14.6%). This difference required a change to antibiotic therapy in only two cases (1.1%).

CONCLUSION

Biopsy is a useful tool to diagnose PJI, but there may be a difference in the detected bacteria between the biopsy and revision surgery. However, this did not affect the choice of antibiotic therapy in most cases, rendering the clinical relevance of this phenomenon as low. Cite this article: Bone Joint J 2020;102-B(3):329-335.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2016 (J-SSCG 2016)

BACKGROUND AND PURPOSE

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2016 (J-SSCG 2016), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in February 2017 and published in the Journal of JSICM, [2017; Volume 24 (supplement 2)] 10.3918/jsicm.24S0001 and Journal of Japanese Association for Acute Medicine [2017; Volume 28, (supplement 1)] http://onlinelibrary.wiley.com/doi/10.1002/jja2.2017.28.issue-S1/issuetoc.This abridged English edition of the J-SSCG 2016 was produced with permission from the Japanese Association of Acute Medicine and the Japanese Society for Intensive Care Medicine.

METHODS

Members of the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine were selected and organized into 19 committee members and 52 working group members. The guidelines were prepared in accordance with the Medical Information Network Distribution Service (Minds) creation procedures. The Academic Guidelines Promotion Team was organized to oversee and provide academic support to the respective activities allocated to each Guideline Creation Team. To improve quality assurance and workflow transparency, a mutual peer review system was established, and discussions within each team were open to the public. Public comments were collected once after the initial formulation of a clinical question (CQ) and twice during the review of the final draft. Recommendations were determined to have been adopted after obtaining support from a two-thirds (> 66.6%) majority vote of each of the 19 committee members.

RESULTS

A total of 87 CQs were selected among 19 clinical areas, including pediatric topics and several other important areas not covered in the first edition of the Japanese guidelines (J-SSCG 2012). The approval rate obtained through committee voting, in addition to ratings of the strengths of the recommendation, and its supporting evidence were also added to each recommendation statement. We conducted meta-analyses for 29 CQs. Thirty-seven CQs contained recommendations in the form of an expert consensus due to insufficient evidence. No recommendations were provided for five CQs.

CONCLUSIONS

Based on the evidence gathered, we were able to formulate Japanese-specific clinical practice guidelines that are tailored to the Japanese context in a highly transparent manner. These guidelines can easily be used not only by specialists, but also by non-specialists, general clinicians, nurses, pharmacists, clinical engineers, and other healthcare professionals.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2016 (J-SSCG 2016)

Background and Purpose

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2016 (J-SSCG 2016), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in February 2017 in Japanese. An English-language version of these guidelines was created based on the contents of the original Japanese-language version.

Methods

Members of the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine were selected and organized into 19 committee members and 52 working group members. The guidelines were prepared in accordance with the Medical Information Network Distribution Service (Minds) creation procedures. The Academic Guidelines Promotion Team was organized to oversee and provide academic support to the respective activities allocated to each Guideline Creation Team. To improve quality assurance and workflow transparency, a mutual peer review system was established, and discussions within each team were open to the public. Public comments were collected once after the initial formulation of a clinical question (CQ), and twice during the review of the final draft. Recommendations were determined to have been adopted after obtaining support from a two-thirds (>66.6%) majority vote of each of the 19 committee members.

Results

A total of 87 CQs were selected among 19 clinical areas, including pediatric topics and several other important areas not covered in the first edition of the Japanese guidelines (J-SSCG 2012). The approval rate obtained through committee voting, in addition to ratings of the strengths of the recommendation and its supporting evidence were also added to each recommendation statement. We conducted meta-analyses for 29 CQs. Thirty seven CQs contained recommendations in the form of an expert consensus due to insufficient evidence. No recommendations were provided for 5 CQs.

Conclusions

Based on the evidence gathered, we were able to formulate Japanese-specific clinical practice guidelines that are tailored to the Japanese context in a highly transparent manner. These guidelines can easily be used not only by specialists, but also by non-specialists, general clinicians, nurses, pharmacists, clinical engineers, and other healthcare professionals.

High diagnostic value of synovial biopsy in periprosthetic joint infection of the hip

BACKGROUND

The role of the synovial biopsy in the preoperative diagnosis of a periprosthetic joint infection (PJI) of the hip has not been clearly defined.

QUESTIONS/PURPOSES

We asked whether the value of a biopsy for a PJI is greater than that of aspiration and C-reactive protein (CRP).

METHODS

Before revision in 100 hip endoprostheses, we obtained CRP values, aspirated the joint, and obtained five synovial biopsy samples for bacteriologic analysis and five for histologic analysis. Microbiologic and histologic analyses of the periprosthetic tissue during revision surgery were used to verify the results of the preoperative diagnostic methods. The minimum followup was 24 months (median 32; range, 24-47 months).

RESULTS

Forty-five of the 100 prostheses were identified as infected. The biopsy, with a combination of the bacteriologic and histologic examinations, showed the greatest diagnostic value of all the diagnostic procedures and led to a sensitivity of 82% (95% CI, ± 11%), specificity of 98% (95% CI, ± 4%), positive predictive value of 97% (95% CI, ± 5%), negative predictive value of 87% (95% CI, ± 8.3%), and accuracy of 91%.

CONCLUSIONS

The biopsy technique has a greater value than aspiration and CRP in the diagnosis of PJI of the hip (Masri et al. J Arthroplasty 22:72-78, 2007). In patients with a negative aspirate, but increased CRP or clinical signs of infection, we regard biopsy to be preferable to just repeating the aspiration.

LEVEL OF EVIDENCE

Level II prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

The value of synovial biopsy, joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements

We analysed the serum C-reactive protein level, synovial fluid obtained by joint aspiration and five synovial biopsies from 145 knee replacements prior to revision to assess the value of these parameters in diagnosing late peri-prosthetic infection. Five further synovial biopsies were used for histological analysis. Samples were also obtained during the revision and incubated and analysed in an identical manner for 14 days. A total of 40 total knee replacements were found to be infected (prevalence 27.6%). The aspiration technique had a sensitivity of 72.5% (95% confidence interval (CI) 58.7 to 86.3), a specificity of 95.2% (95% CI 91.2 to 99.2), a positive predictive value of 85.3% (95% CI 73.4 to 100), a negative predictive value of 90.1% (95% CI 84.5 to 95.7) and an accuracy of 89%. The biopsy technique had a sensitivity of 100%, a specificity of 98.1% (95% CI 95.5 to 100), a positive predictive value of 95.2% (95% CI 88.8 to 100), a negative predictive value of 100% and an accuracy of 98.6%. C-reactive protein with a cut-off-point of 13.5 mg/l had a sensitivity of 72.5% (95% CI 58.7 to 86.3), a specificity of 80.9% (95% CI 73.4 to 88.4), a positive predictive value of 59.2% (95% CI 45.4 to 73.0), a negative predictive value of 88.5% (95% 81.0 to 96.0 CI) and an accuracy of 78.1%. We found that biopsy was superior to joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements.

Impact of amoxicillin prophylaxis on the incidence, nature, and duration of bacteremia in children after intubation and dental procedures

BACKGROUND

Controversy exists about the impact of prophylactic antibiotics on bacteremia after invasive dental procedures. The purpose of this double-blind, randomized, placebo-controlled study was to determine the impact of amoxicillin prophylaxis on the incidence, nature, and duration of bacteremia from nasotracheal intubation and dental procedures in children.

METHODS AND RESULTS

Children were randomly assigned before surgery to the American Heart Association (AHA)-recommended dose of amoxicillin or to a placebo. Aerobic and anaerobic blood cultures were drawn at 8 specific time points after intubation, dental restorative and cleaning procedures, and before, during, and after dental extraction(s), to include blood drawings up to 45 minutes after the last extraction. Aerobic and anaerobic blood culture results were used to determine the incidence, nature, and duration of bacteremia from these procedures. For the 100 children enrolled (mean age, 3.5 years), the overall incidence of positive blood cultures, defined as at least 1 positive culture of the 8, was significantly higher in the placebo (84%) than the amoxicillin group (33%) (P<0.0001). Bacteremia occurrence rates after intubation and after dental restorations and cleaning were 18% and 20% in the placebo group and 4% and 6% in the amoxicillin group (P=0.05 and P=0.07, respectively). At 1.5 minutes after the initiation of dental extractions, bacteremia occurred in 76% of the placebo group versus 15% of the amoxicillin group (P<0.001). The majority of the 152 positive cultures and of the 29 different bacteria identified were Gram-positive cocci. Bacteremia persisted longer in the placebo group.

CONCLUSIONS

Bacteremia from these procedures occurs more often, from a wider variety of bacterial species, and for a longer duration after dental extractions than previously reported in any age group. Amoxicillin has a significant impact on the incidence, nature, and duration of bacteremia after nasal intubation, dental restorative and cleaning procedures, and dental extractions.

Detection of group B streptococcal bacteremia in simulated intrapartum antimicrobial prophylaxis

The diagnostic value of negative blood cultures from neonates whose mothers receive intrapartum antimicrobial prophylaxis for prevention of perinatal group B streptococcal disease is uncertain. We investigated whether blood culture medium containing resin designed to adsorb antibiotic improved group B streptococcal detection following simulated intrapartum antimicrobial prophylaxis. Group B streptococcus (Streptococcus agalactiae) was preincubated with varying antibiotic concentrations before inoculation into BACTEC Peds Plus resin-containing medium, BACTEC Standard, or Trek ESP 80A. In the presence of 10 mcg/mL ampicillin, detection of both low (<500 CFU/mL) and high (>500 CFU/mL) S. agalactiae inocula ranged between 75-100% of resin-containing medium bottles; detection rates in both non-resin-containing media were lower. When S. agalactiae was detected, it was detected sooner with resin-containing medium. The addition of gentamicin to ampicillin did not affect sensitivity of resin-containing medium for S. agalactiae. In our model, resin-containing medium more consistently and more rapidly detected S. agalactiae than did either of two non-resin-containing media, in the presence of antibiotic levels likely present in fetal sera following intrapartum antimicrobial prophylaxis.

Experience of changing between signal and Bactec 9240 blood culture systems in a children's hospital

AIM

To compare experience of positive blood cultures in successive years before and after changing from Signal (Unipath) to Bactec 9240 (Becton Dickinson) blood culture systems.

METHODS

Analysis of data collected prospectively on 7967 Signal and 7062 Bactec blood culture sets.

RESULTS

Significant growths occurred in 5.7% of Signal and 8.9% of Bactec cultures; 33.0% more significant isolates and 24.0% more episodes of bacteraemia were detected in the second year, following introduction of the Bactec system. Inpatient hospital activity increased by 8.2% between the first and second years, although the numbers of blood cultures received actually fell by 11.4%. There were striking increases in numbers of isolates of coagulase negative staphylococci (47.7%) and Enterobacteriaceae (56.8%) from Bactec cultures. Two anaerobic bacteraemias were detected in Signal blood cultures, whereas none was detected by the Bactec system, despite 12.1% of sets including an anaerobic bottle. Of significant positive cultures, 90.2% were detected within one day with the Bactec 9240, compared with only 50.0% of Signal cultures; 20.7% of significant positive Signal blood cultures were detected only on terminal subculture. Microorganisms that were not significant were isolated from 5.1% Signal and 3.8% Bactec cultures.

CONCLUSIONS

Compared with the Signal system, the Bactec 9240 offers markedly more rapid and sensitive detection of bacteraemia, together with a lower rate of non-significant isolates. However, using a single PEDS PLUS/F bottle the few episodes of anaerobic bacteraemia that occur in children are likely to be missed.

Comparative study of three different BACTEC culture media for the detection of bacteremia in ambulatory and hospitalized children

To compare the yield of two aerobic and an anaerobic BACTEC blood culture media in detecting bacteremia in ambulatory and hospitalized care settings at a children's hospital, a prospective cohort study was completed. Over an 18-month period, equal blood volumes (minimum of 1 mL/bottle) were inoculated into a three-bottle culture set including aerobic BACTEC NR 6A, aerobic BACTEC PEDS Plus and anaerobic NR 7A broths. Chart reviews were completed on all children with bacteremia to determine whether the isolate was clinically significant based on predefined criteria. Among 5328 evaluable blood culture sets, 323 clinically significant organisms (110 from ambulatory and 213 from hospitalized children) were isolated. Most Streptococcus pneumoniae, Haemophilus species, and Neisseria or Moraxella species were recovered from children attending the emergency department or out-patient clinics. Important isolates in hospitalized children included most of the staphylococci and Enterobacteriaceae, and all group D enterococci, Gram-negative nonfermentative bacilli and all Candida species. Overall, significantly more isolates were detected only in the anaerobic bottle from ambulatory children (P<0.0001), including 13 of 54 (24%) patients with S pneumoniae bacteremias presenting to the emergency department. This study indicated that different BACTEC blood culture media combinations are needed in ambulatory and hospitalized pediatric care settings to ensure the optimal recovery of all types of isolates. Whereas aerobic blood culture bottles are adequate for detection of bacteremia in hospitalized children, the common occurrence of fastidious organisms mandates the need for a combined aerobic/anaerobic culture set in ambulatory pediatric care settings.

Controlled comparison of bioMérieux VITAL and BACTEC NR-660 systems for detection of bacteremia and fungemia in pediatric patients

The bioMérieux VITAL automated blood culture system measures a decrease in fluorescence to detect the presence of microorganisms in blood. To assess the performance of VITAL with AER aerobic medium versus that of the nonradiometric BACTEC NR-660 PEDS PLUS medium for the detection of sepsis in children, a total of 12,146 blood specimens were collected at three university medical centers and inoculated into AER and PEDS PLUS bottles that were weighed before and after filling. The sample volumes were considered adequate in 6,276 bottle pairs. The total yield of isolates was 629, of which 489 (78%) were judged to be the cause of true infections. Staphylococci (P < 0.001) and yeasts (P < 0.05) were detected more often in PEDS PLUS bottles, as were all microorganisms combined (P < 0.001). The improved detection in the PEDS PLUS medium was most marked for patients on antimicrobial therapy (P < 0.001), but remained statistically significant even for patients not on therapy (P < 0.025). There were 431 episodes of sepsis, including 407 considered adequate for analysis. Of the 363 unimicrobial episodes, 278 were detected by both bottles, 64 were detected by PEDS PLUS bottles only, and 21 were detected by AER bottles only (P < 0.01). No false-negative cultures were detected by terminal subculture of the PEDS PLUS bottles when the companion AER bottle was positive. However, there were 14 false-negative cultures (7 yeasts, 5 staphylococci, 1 Enterococcus faecalis, and 1 Enterobacter sp.) on terminal subculture of the AER bottles when the companion PEDS PLUS bottle was positive. When both systems were positive, the VITAL system detected bacteria earlier than did the BACTEC system by a mean of 1.6 h. Also, false-positive signals were less common with the VITAL system. We conclude that the VITAL system with AER medium must be modified to improve the detection of clinically important staphylococci and yeasts if it is to perform comparably to the BACTEC NR-660 nonradiometric system with PEDS PLUS medium for a pediatric population.

Comparison of Isolator 1.5 and BACTEC NR660 aerobic 6A blood culture systems for detection of fungemia in children

The Isolator 1.5 microbial system (ISO 1.5) (Wampole Laboratories, Cranbury, N.J.) was compared with the BACTEC NR660 aerobic NR6A bottle (NR6A) (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) for the detection of fungemia in hospitalized pediatric patients. For 4,825 paired blood cultures evaluated retrospectively from April 1992 to December 1994, at least one blood culture system was positive for 89 clinically important fungal isolates involved in 36 episodes of fungemia in 34 patients. Sixty isolates (44 Candida albicans, 12 Candida parapsilosis, and 4 Candida tropicalis isolates) were recovered from both systems, 13 were recovered from NR6A bottles only (10 C. albicans, 1 C. parapsilosis, and 2 Cryptococcus neoformans isolates), and 16 were recovered from ISO 1.5 tubes only (8 C. albicans and 5 C. parapsilosis isolates and 1 C. tropicalis, 1 Candida lusitaniae, and 1 Rhodotorula glutinis isolate) (P > 0.05). For the 60 Candida isolates from both systems, the mean time to detection was the same in each system. Thirty-seven isolates were detected by both systems on the same day, 9 isolates were detected earlier by NR6A, and 14 isolates were detected earlier by ISO 1.5 (P > 0.05). Of the 36 clinically important episodes of fungemia, 22 were detected by both systems (13 C. albicans isolates and 9 other Candida isolates), 4 were detected by NR6A only (3 C. albicans isolates and 1 C. neoformans isolate), and 10 were detected by ISO 1.5 only (3 C. albicans isolates, 6 other Candida isolates, and 1 R. glutinis isolate) (P > 0.05). Of the 22 episodes in which cultures from both systems were positive at some point during the episode, 12 were detected on the same day by both systems, 8 were detected earlier by NR6A, and 2 were detected earlier by ISO 1.5. Thus, for our pediatric population, NR6A is comparable to ISO 1.5 in both yield and time to detection of yeasts in fungemic patients.

Value of routine anaerobic blood cultures for pediatric patients

OBJECTIVE

Anaerobic bacteremia rarely occurs in children. Therefore we assessed the usefulness of routinely obtaining anaerobic blood cultures in our pediatric patients.

STUDY DESIGN

Records of 9360 paired aerobic anaerobic blood culture bottles (Bactec NR660 System) containing blood specimens from pediatric inpatients and outpatients at Duke University Medical Center, Durham, N.C., were reviewed retrospectively. Yield and speed of detection were calculated for each bottle and compared for statistical significance by the McNemar test.

RESULTS

A total of 723 clinically important microorganisms were isolated; only 15 (2.1%) were strict anaerobes. Significantly more microorganisms (p < 0.001), especially staphylococci, nonfermenting gram-negative rods, enteric gram-negative rods, and yeasts, were detected by use of the aerobic bottle. The anaerobic bottle was important in identifying an anaerobic microorganism as the cause of sepsis in only five patients, all of whom were at increased risk of having anaerobic infection.

CONCLUSIONS

Anaerobic blood cultures are rarely helpful in the majority of pediatric patients and usually show positive results only in clinical settings associated with anaerobic infection. Microorganisms that prefer an aerobic environment, such as Pseudomonas aeruginosa and yeasts, are now far more common than anaerobes in children; aerobic culturing of the entire volume of blood collected might increase the yield from pediatric blood cultures.

Prevention of gram-positive sepsis in neonates weighing less than 1500 grams

A prospective, randomized study to evaluate the effectiveness of a continuous low-dose vancomycin infusion to prevent nosocomial gram-positive bacteremia was initiated within the first 2 weeks of life in neonates weighing < 1500 gm. Seventy-one infants received constant infusion of vancomycin (25 micrograms/ml) mixed with their total parenteral nutrition solution; 70 infants served as control subjects. The groups were clinically similar in birth weight, estimated gestational age, and severity of illness. Administration of vancomycin was begun at a mean age of 5.4 +/- 2.9 days. Infants had mean serum vancomycin concentrations of 2.4 micrograms/ml, and received vancomycin for a mean of 11 +/- 7 days. No vancomycin-resistant organisms were detected in surveillance cultures during the 2-year study period. Twenty-four of seventy control infants, in comparison with 1 of 71 infants receiving vancomycin, had gram-positive bacteremia (p < 0.001). The addition of a low dose of vancomycin to alimentation fluids virtually eliminated the incidence of gram-positive bacteremia in an at-risk population of very low birth weight infants. However, the widespread use of vancomycin in total parenteral nutrition solution is not recommended until better data on the emergence of vancomycin-resistant organisms are available.

Assessment of gelatin supplementation of PEDS Plus BACTEC blood culture medium

Gelatin supplementation of blood culture media has been shown to neutralize the effects of sodium polyanetholesulfonate and enhance detection of Neisseria species. We evaluated the effect of 1.2% gelatin supplementation of nonradiometric Peds Plus Bactec blood culture medium on the rate and speed of recovery of pathogens from pediatric patients. From June 1991 to June 1992, a total of 6451 paired comparisons of blood cultures in Peds Plus medium and gelatin-supplemented Peds Plus medium were done: 465 organisms were isolated, of which 338 were significant. There were no significant differences in recovery of organisms or the speed of detection of microbial growth between the two media. In particular, the recovery of Neisseria meningitidis (eight isolates) was not improved with gelatin supplementation. In conclusion, gelatin supplementation of Peds Plus Bactec medium does not offer any advantage over the regular Peds Plus Bactec medium.

Comparison of the BacT/Alert pediatric blood culture system, Pedi-BacT, with conventional culture using the 20-milliliter Becton-Dickinson supplemented peptone broth tube

The performance of the Pedi-BacT system, the BacT/Alert (Organon Teknika Corp., Durham, N.C.) pediatric blood culture bottle, was compared with that of a conventional 20-ml supplemented peptone broth tube (Becton-Dickinson Corp., Cockeysville, Md.) (BD system) in matched aerobic cultures. The tubes of the BD system were visually examined daily for 7 days and were subcultured during the first 24 h of incubation. Pedi-BacT cultures were mechanically agitated and continuously monitored for growth by the instrument. Of the 6,628 compliant pairs, 331 (5.0%) were positive in both systems, 220 (3.3%) were positive in the Pedi-BacT system only, and 170 (2.6%) were positive in the BD system only. One (0.02%) false-negative culture and 15 (0.2%) false-positive cultures occurred with the Pedi-BacT system while 20 (0.3%) false-negative cultures and 35 (0.5%) false-positive cultures occurred with the BD system. Of 288 clinically significant organisms detected in matched pairs from which a single isolate was recovered, 176 (61%) were recovered from both systems, 83 (29%) were recovered from the Pedi-BacT system only (P < 0.0001), and 29 (10%) were recovered from the BD system only. Members of the family Enterobacteriaceae (P < 0.01), miscellaneous nonfermenters (P < 0.05), and Candida spp. (P < 0.01) were isolated more frequently in the Pedi-BacT system than in the BD system. No significant difference in recovery of other organisms was found between the systems. The average time to detection for the Pedi-BacT system ranged from 11.5 h for streptococci to 29.7 h for enterococci, while that for the BD system ranged from 20.3 h for streptococci to 66.4 h for some nonfermenters. The BacT/Alert system is a reliable, labor-saving alternative to conventional blood culture methods.

Comparison of the Bactec Peds Plus pediatric blood culture vial with Roche pediatric Septi-Chek for blood cultures from pediatric patients

Equal volumes of blood from 4,112 blood cultures were inoculated into one Bactec Peds Plus bottle and one Roche Septi-Chek bottle. There were no significant differences in the recoveries of bloodstream pathogens. Initial detection occurred earlier with Bactec Peds Plus, while growth on solid media occurred earlier with Roche Septi-Chek.

Determination of growth value thresholds for BACTEC PLUS aerobic blood culture vials

Growth value thresholds used to identify positive blood culture vials can be defined by users for each BACTEC NR-660 bacteremia detection instrument. Growth values were compared with the recovery of organisms from vials flagged as positive during the testing of 3.056 high-volume vials containing aerobic (BACTEC PLUS 26) medium over a 2-month period. Results showed that optimal threshold values for our use of these vials varied from those recommended by the manufacturer; if the thresholds defined from these data had been used during the study period, total vials flagged as positive from which no organisms were recovered (false alarms) would have been reduced from 181 (5.9/100 vials tested) to 71 (2.3/100 vials tested), with a minimal decrease in the identification of vials containing usual or occasional pathogens (hits). Adjustments of growth value thresholds by the individual user can make the use of BACTEC instruments more efficient by decreasing further processing of vials from which no organisms are recovered.

Pediatric blood culture evaluation of the BACTEC PEDS Plus and the DuPont Isolator 1.5 systems

A new nonradiometric BACTEC medium has been developed for culturing pediatric blood samples. The BACTEC PEDS Plus medium (BACTEC PED) consists of 20 ml of an enriched broth with resins. In contrast to the other aerobic BACTEC media, there is a lower concentration of sodium polyanetholesulfonate in the medium and more CO2 in the headspace of the vial. This study was conducted in two different pediatric settings to compare the performance of the BACTEC PED medium with the Du Pont Isolator 1.5 system (ISO 1.5) in terms of overall organism recovery and time to detection. Equal volumes of up to 1.5 ml were tested in both systems. A total of 4063 culture sets were analyzed, yielding 301 (7.4%) clinically significant isolates. Of these, 86 (29%) were recovered only from the BACTEC PED and 12 (4%) only from the ISO 1.5 (p less than 0.001). BACTEC PED recovered significantly more staphylococci and Enterobacteriaceae than ISO 1.5 (p less than 0.001 and p less than 0.005, respectively). Detection times of isolates recovered in both systems were comparable. For those patients on antibiotic therapy at the time of culture, 21 (37%) were positive only in the BACTEC PED, whereas two (4%) were positive only in the ISO 1.5. The nontherapy group had 61 (27%) organisms that were detected in BACTEC PED only and 9 (4%) in ISO 1.5 only. These results indicate that BACTEC PED is a significant advance in blood culture systems that will provide a sensitive method for detecting pediatric bacteremias.