Antimicrobial binding and growth kinetics in BacT/ALERT® FA Plus and BACTEC® Aerobic/F Plus blood culture media

Clinical and Economic Evaluation of Blood Culture Whole Process Optimisation in Critically Ill Adult Patients With Positive Blood Cultures

OBJECTIVES

Optimising blood culture processing is important to ensure that bloodstream infections are accurately diagnosed while minimising adverse events caused by antibiotic abuse. This study aimed to evaluate the impact of optimised blood culture processes on antibiotic use, clinical outcomes and economics in intensive care unit (ICU) patients with positive blood cultures.

METHODS

From March 2020 to October 2021, this microbiology laboratory implemented a series of improvement measures, including the clinical utility of Fastidious Antimicrobial Neutralization (FAN® PLUS) bottles for the BacT/Alert Virtuo blood culture system, optimisation of bottle reception, graded reports and an upgraded laboratory information system. A total of 122 ICU patients were included in the pre-optimisation group from March 2019 to February 2020, while 179 ICU patients were included in the post-optimisation group from November 2021 to October 2022.

RESULTS

Compared with the pre-optimisation group, the average reporting time of identification and antimicrobial sensitivity was reduced by 16.72 hours in the optimised group. The time from admission to targeted antibiotic therapy within 24 hours after receiving both the Gram stain report and the final report were both significantly less in the post-optimisation group compared with the pre-optimisation group. The average hospitalisation time was reduced by 6.49 days, the average antimicrobial drug cost lowered by $1720.85 and the average hospitalisation cost by $9514.17 in the post-optimisation group.

CONCLUSIONS

Optimising blood culture processing was associated with a significantly increased positive detection rate, a remarkable reduction in the length of hospital stay and in hospital costs for ICU patients with bloodstream infections.

Clinical features and outcomes of bacteremic and non-bacteremic Campylobacteriosis: a case-control study

PURPOSE

Campylobacter bloodstream infection (C-BSI) is uncommon, and its clinical significance is unclear. The aim of the study was to determine risk factors and clinical outcomes associated with Campylobacter BSI.

METHODS

We performed a single center retrospective case-control study comparing patients with C-BSI (cases) and patients with nonbacteremic Campylobacter enteritis (controls), from January 2007 through June 2020. Case and control patients were matched by age and sex at a ratio of 1:2. Demographic, clinical, and microbiological characteristics were compared between groups.

RESULTS

We identified 76 patients with C-BSI and matched them with 149 nonbacteremic patients with Campylobacter enteritis. Rates of C-BSI increased tenfold in 2014 following the introduction of BacTAlert FA/FN Plus blood culture bottles. Baseline variables significantly associated with C-BSI on multivariable logistic regression were fever, absence of diarrhea and recent exposure to antibiotics. Compared with controls, C-BSI was associated with higher 30-day mortality (12% vs. 2%, P = 0.003), more frequent need for intensive care (6.6% vs. 1.2%, P = 0.032) and longer hospital stay (median, 5 days vs. 3 days, P = 0.003). There was a high proportion of immunocompromised patients in both groups (55%).

CONCLUSIONS

C-BSI is identified with increasing frequency, reflecting both changes in epidemiology and improved sensitivity of blood culture systems. Our findings indicate that detection of Campylobacter spp. in blood culture is associated with significantly higher rates of death and other adverse outcomes.

The Impact of Implementing the Virtuo Blood Culture System on the Characteristics and Management of Patients with Staphylococcus aureus Bacteremia

Persistent Staphylococcus aureus bacteremia (SAB) has been associated with increased mortality. Enhanced microbial detection with new blood culture technology may improve detection of S. aureus in patients with SAB. We performed a 24-month retrospective study of hospitalized adults with SAB and an infectious diseases consult comparing two time periods pre- (January to December 2018) and postimplementation (January to December 2019) in which the VersaTREK and BacT/Alert Virtuo blood culture systems were used, respectively. Measurements included SAB duration, time to positivity, source of bacteremia, antimicrobial therapy, and mortality. A total of 416 episodes of SAB occurred during the study period: 176 (42%) pre- and 240 (58%) postimplementation. Patients in both periods had similar clinical characteristics; however, patients in the postimplementation period were more likely to have intermediate (3 to 6 days; 23% versus 40%; P < 0.001) and prolonged SAB duration (>7 days; 4% versus 14%; P < 0.001). Combination antistaphylococcal therapy was more frequent postimplementation (6.3% pre- versus 15.8% postimplementation; P = 0.003), and the median time to source control was shorter (4 versus 2 days; P = 0.02). Median time to positivity for the index blood culture was shorter postimplementation (17.8 h pre- versus 13.3 h postimplementation; P < 0.001). There was no difference in 90-day all-cause readmissions (51% versus 44%; P = 0.11) or mortality (32% versus 32%; P = 0.95). An increased frequency of prolonged SAB with increased use of combination antistaphylococcal therapy was noted with implementation of a new blood culture system, likely secondary to the blood culture media; however, no differences on adverse outcomes were noted.

Novel strategies to diagnose prosthetic or native bone and joint infections

INTRODUCTION

Bone and Joint Infections (BJI) are medically important, costly and occur in native and prosthetic joints. Arthroplasties will increase significantly in absolute numbers over time as well as the incidence of Prosthetic Joint Infections (PJI). Diagnosis of BJI and PJI is sub-optimal. The available diagnostic tests have variable effectiveness, are often below standard in sensitivity and/or specificity, and carry significant contamination risks during the collection of clinical samples. Improvement of diagnostics is urgently needed.

AREAS COVERED

We provide a narrative review on current and future diagnostic microbiology technologies. Pathogen identification, antibiotic resistance detection, and assessment of the epidemiology of infections via bacterial typing are considered useful for improved patient management. We confirm the continuing importance of culture methods and successful introduction of molecular, mass spectrometry-mediated and next-generation genome sequencing technologies. The diagnostic algorithms for BJI must be better defined, especially in the context of diversity of both disease phenotypes and clinical specimens rendered available.

EXPERT OPINION

Whether interventions in BJI or PJI are surgical or chemo-therapeutic (antibiotics and bacteriophages included), prior sensitive and specific pathogen detection remains a therapy-substantiating necessity. Innovative tests for earlier and more sensitive and specific detection of bacterial pathogens in BJI are urgently needed.

Real World Evaluation of the Impact of Implementation of the VIRTUO Blood Culture System in a Tertiary Care Hospital

The bioMerieux BACT/ALERT VIRTUO (VIRTUO) blood culture system used in combination with resin-containing media may enhance the growth of microorganisms. Our objective was to assess the impact of transitioning to the VIRTUO system in comparison to the VersaTREK blood culture system at a tertiary care medical center. We retrospectively reviewed all blood cultures performed at a 1250-bed academic medical center between January-December 2018 (VersaTREK) and January-December 2019 (VIRTUO). Blood culture positivity rates and contamination rates were compared pre- versus post-VIRTUO implementation. Of 101,438 blood cultures performed during the study period, 48,839 (48.1%) were processed pre-implementation and 52,599 (51.9%) post-implementation. The blood culture positivity rate increased from 8.1% pre-implementation to 11.7% post-implementation (p<0.001). Staphylococcus aureus was the most frequently isolated species in both time periods and had higher recovery rate post-implementation (1.5% of all blood cultures obtained pre- vs. 3.4% post-implementation, p<0.001). A higher recovery rate in the post-implementation period was also noted for coagulase-negative staphylococci (1.9% pre- vs. 2.7% post-implementation, p<0.001), as well as modest but statistically significant changes for E. coli (0.8% vs. 1.0%, p<0.001), K. pneumoniae (0.4% vs. 0.5%, p=0.005) and Candida albicans. (0.1% vs. 0.2%, p=0.038). The inpatient blood culture contamination rate was higher post-implementation (1.5% pre- vs. 1.9% post-implementation, p<0.001). The VIRTUO blood culture system was associated with a higher observed proportion of positive blood cultures compared to the previous VersaTREK system. Future studies are needed to assess whether an increased rate of positive blood cultures is associated with changes in clinical outcomes.

Inactivation of Clinically Frequently Used Antimicrobial Agents By BacT/ALERT FAN Plus and BACTEC Aerobic and Anaerobic Culture Media in Simulated Blood Cultures: First Comparative Evaluation in China Mainland

Purpose

To evaluate the antimicrobial inactivation capabilities of BacT/ALERT (FA Plus and FN Plus) and BACTEC (Plus Aerobic/F and Lytic/10 Anaerobic/F) media.

Patients and Methods

The inactivation capabilities of the commercial blood culture media were compared using 21 microorganism-antimicrobial combinations in simulated adult blood cultures.

Results

BacT/ALERT culture media demonstrated higher detection rates than the BACTEC culture media. The recovery rates of the aerobic bottles were 74/115 (64.3%) for FA Plus bottles and 64/115 (55.7%) for BACTEC Aerobic Plus bottles. The BacT/ALERT FAN Plus culture media exhibited a shorter time to detection (TTD). The TTD of FA Plus media was 14.7 h, 4.85 h shorter than the BACTEC Aerobic media (19.55 h), while the TTDs of FN Plus media and BACTEC Anaerobic media were 16.8 h and 18.4 h, respectively.

Conclusion

BacT/ALERT (FA Plus and FN Plus) media showed relative, but not absolute, advantages, as it had higher detection rates and shorter TTD and thus can be selectively applied to patients with prior use of antimicrobial agents before blood culture samples are taken.

Nonautomated Blood Cultures in a Low-Resource Setting: Optimizing the Timing of Blind Subculture

Laboratory procedures for blood cultures in a hospital in Phnom Penh were adapted to optimize detection of Burkholderia pseudomallei, an important pathogen in this setting. The effects of these changes are analyzed in this study. Blood cultures consisted of two BacT/ALERT bottles (bioMérieux, Marcy-l’Etoile, France). Growth was detected visually by daily inspection of the bottles. In 2016, the aerobic–anaerobic pair (FA/FN FAN) was substituted by an aerobic pair of BacT/ALERT FA Plus bottles. Blind subculture (BS) (subculture in the absence of visual growth) was advanced from day 3 to day 2 of incubation in July 2016. In July 2018, it was further advanced to day 1 of incubation. From July 2016 to October 2019, 9,760 blood cultures were sampled. The proportion of cultures showing pathogen growth decreased from 9.6% to 6.8% after the implementation of the laboratory changes (P < 0.001). Advancing the BS from day 3 to day 2 led to an increased proportion of pathogens detected by day 3 (92.8% versus 82.3%; P < 0.001); for B. pseudomallei, this increase was even more remarkable (92.0% versus 18.2%). Blind subculture on day 1 similarly increased the proportion of pathogens detected by day 2 (82.9% versus 69.0% overall, 66.7% versus 10.0% for B. pseudomallei; both P < 0.001). However, after implementation of day 1 subculture, a decrease in recovery of B. pseudomallei was observed (12.4% of all pathogens versus 4.3%; P < 0.001). In conclusion, earlier subculture significantly shortens time to detection and time to actionable results. Some organisms may be missed by performing an early subculture, especially those that grow more slowly.

Effect of delayed entry on performance of the BACT/ALERT FAN PLUS bottles in the BACT/ALERT VIRTUO blood culture system

Delayed entry of patient blood culture samples into a microbial detection system is unavoidable at times, due to off-shift staffing or transporting samples to centralized laboratories. Pre-incubation time and temperature of blood culture bottles are the most critical factors impacting recovery and detection of microorganisms. A total of 1377 BACT/ALERT® (BTA) Fastidious Antimicrobial Neutralization (FAN® PLUS) bottles (FA PLUS, FN PLUS, and PF PLUS) were tested after delayed entry times of 24 and 36 h at 20–25 °C (room temperature, RT) prior to loading into the BACT/ALERT® VIRTUO® microbial detection system (VIRTUO). Clinically relevant organisms were inoculated into bottles with 5–84 colony forming units (CFU) per bottle, and human blood (0 to 10 mL), and then loaded into the VIRTUO. When bottles were loaded without delay, a mean time to detection (TTD) of 9.6 h was observed. For delayed bottles, the TTD reported by the VIRTUO was added to the 24-h and 36-h delay times and resulted in average time to results of 32.5 h and 42.5 h, respectively. The FAN PLUS bottles in conjunction with the VIRTUO produced acceptable results when delays up to 24 h at 20–25 °C occur in loading.

Validation of Microbiological Testing of Cellular Medicinal Products Containing Antibiotics

Background

The risk of microbial contamination of cellular products can be reduced when cultured in the presence of antibiotics. This however, may impact the sensitivity of microbiological tests. Given that the addition of antibiotics to cell/tissue products does not guarantee sterility but may just reduce the proliferation rate of microorganisms, microbiological testing of medicinal products remains obligatory. Thus, an appropriate method to test for microbial contamination of antibiotic-containing products has to be validated.

Objectives

In the context of microbiological testing of a cellular advance therapy medicinal product, the method was validated and approved by German competent authorities for four different matrices with three matrices containing antibiotics. The paper shall provide help for establishing test methods for other investigational medicinal products which contain antibiotics.

Methods

Matrices were spiked individually with Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Streptococcus pyogenes, Escherichia coli, Clostridium sporogenes, Propionibacterium acnes, Candida albicans, and Aspergillus brasiliensis. Samples were pretreated with penicillinase for 1 h before inoculation and incubation in BacT/ALERT iFA Plus and iFN Plus culture bottles using 3D BacT/ALERT automates. Microorganisms within positive BacT/ALERT bottles were specified. The procedure was performed in two different laboratories to prove robustness of test.

Results

All nine tested microorganisms were detected within 14 days of incubation in accordance with requirements of the European Pharmacopoiea in terms of sensitivity, specificity and robustness of the test. Penicillin and streptomycin did not have any influence on specifications defined within the investigational medicinal product dossier.

Conclusions

Culturing cellular products in the presence of antibiotics can serve as an effective method to reduce contamination risk but only if the chosen antibiotics neither have any influence on specifications of the investigational medicinal product nor interfere with microbiological tests. Consequently, cells and tissues primarily contaminated with microorganisms, like placenta, may be considered as a source of cellular therapeutics when cultured for a sufficient time with antibiotics and tested with a validated method. The choice of microorganisms for the validation of the microbiological test should always consider all conceivable scenarios and should not be reduced to minimal criteria defined in European Pharmacopoiea, wrongfully believing to thus save time and effort.

Effect of Clinically Meaningful Antibiotic Concentrations on Recovery of Escherichia coli and Klebsiella pneumoniae Isolates from Anaerobic Blood Culture Bottles with and without Antibiotic Binding Resins

Blood cultures are routinely collected in pairs of aerobic and anaerobic bottles. Artificial sterilization of Gram-negative bacteria in aerobic bottles containing clinically meaningful antibiotic concentrations has previously been observed. This study assessed recovery from anaerobic bottles with and without antibiotic binding resins. We studied the recovery of Escherichia coli and Klebsiella pneumoniae when exposed to meropenem, imipenem, cefepime, cefazolin, levofloxacin, and piperacillin-tazobactam in resin-containing BacT/Alert FN Plus and BD Bactec Plus anaerobic/F bottles as well as resin-free BacT/Alert SN and BD Bactec standard anaerobic bottles. Bottles were inoculated with bacteria and whole blood containing peak, midpoint, or trough concentrations and incubated for up to 120 hours in their respective detection systems. In E. coli resin-containing bottles, recovery was observed in 10/24 (42%), 17/24 (71%), and 18/24 (75%) (P = 0.034) of those exposed to peak, midpoint, and trough concentrations, respectively. In K. pneumoniae resin-containing bottles, recovery was observed in 8/16 (50%), 10/16 (63%), and 10/16 (63%) (P = 0.710), respectively. No growth was detected in bottles containing cefepime regardless of concentration, while recovery was observed in the presence of all concentrations of cefazolin and piperacillin-tazobactam. Recovery in bottles with meropenem and imipenem was more frequently observed in BacT/Alert FN Plus bottles compared with Bactec Plus bottles. Resin-free bottles demonstrated significantly lower recovery than bottles containing binding resin. Clinical concentrations of certain antibiotics can adversely affect detection of E. coli and K. pneumoniae in anaerobic blood culture bottles. Obtaining blood cultures immediately before a dose and utilizing resin-containing anaerobic bottles will maximize the likelihood of recovery.

Recovery of Gram-Negative Bacteria from Aerobic Blood Culture Bottles Containing Antibiotic Binding Resins after Exposure to β-Lactam and Fluoroquinolone Concentrations

Blood culture bottles containing antibiotic binding resins are routinely used to minimize artificial sterilization in the presence of antibiotics. However, the resin binding kinetics can differ between antibiotics and concentrations. This study assessed the impact of clinically meaningful peak, midpoint, and trough concentrations of meropenem, imipenem, cefepime, cefazolin, levofloxacin, and piperacillin-tazobactam on the recovery of Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae from resin-containing BacT/Alert FA Plus and Bactec Aerobic/F blood culture bottles. P. aeruginosa-inoculated bottles alarmed positive in 4/20 (20%), 16/20 (80%), and 20/20 (100%) of those with peak, midpoint, and trough concentrations of antipseudomonal agents, respectively (P ≤ 0.001). E. coli was recovered from 8/24 (33%), 11/24 (46%), and 14/24 (58%) of bottles with peak, midpoint, and trough concentrations, respectively (P = 0.221). K. pneumoniae was recovered from 8/16 (50%) at all concentrations of the studied antibiotics (P = 1.0). BacT/Alert and Bactec bottles inoculated with antibiotics and P. aeruginosa had similar times to detection (TTD) (P = 0.352); however, antibiotic-containing BacT/Alert bottles had a shorter TTD compared with antibiotic-containing Bactec bottles for E. coli (P = 0.026) and K. pneumoniae (P ≤ 0.001). Pathogen recovery in BacT/Alert FA Plus and Bactec Aerobic/F blood culture bottles containing antibiotic binding resins was greatly reduced in the presence of antibiotics, especially at higher concentrations. These data support the practice of drawing blood cultures immediately before an antibiotic dose to maximize the chances of pathogen recovery.

A comparative evaluation of BACT/ALERT FA PLUS and FN PLUS blood culture bottles and BD BACTEC Plus Aerobic and Anaerobic blood culture bottles for antimicrobial neutralization

The performance of BACT/ALERT FA and FN PLUS (FA PLUS and FN PLUS) blood culture bottles with the BACT/ALERT VIRTUO (bioMérieux, Inc., Durham, NC) and BD BACTEC Plus Aerobic and Anaerobic (BD Aerobic and BD Anaerobic) blood culture bottles with the BD BACTEC FX (BD Diagnostics, Sparks, MD) for antimicrobial neutralization at peak serum concentration was evaluated. The following antibiotic agents and microbial strains were used: ampicillin, cefepime, cefotaxime, gentamicin, levofloxacin, meropenem, piperacillin-tazobactam, and vancomycin; methicillin-sensitive Staphylococcus aureus, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Bacteroides fragilis. The detection rate of FA PLUS bottles was 69.1% (259/375) and that of BD Aerobic bottles was 75.5% (283/375) (p = 0.050). In the case of anaerobic culture, the overall detection rate of FN PLUS bottles was 77.0% (231/300) and that of BD Anaerobic bottles was 71.3% (214/300) (p = 0.113). The time to detection (TTD) from aerobic culture was 2.8 h shorter in FA PLUS bottles (12.4 h) compared to BD Aerobic bottles (15.2 h) (p < 0.001). And the TTD from anaerobic culture was 1.6 h shorter in FN PLUS bottles (18.1 h) compared to BD Anaerobic bottles (19.7 h) (p = 0.061). The FA PLUS bottles exhibited a lower detection rate compared to BD Aerobic bottles, while FN PLUS bottles showed a higher detection rate compared to BD Anaerobic bottles. The BACT/ALERT VIRTUO system exhibited shorter TTD compared to the BD BACTEC FX system for both aerobic and anaerobic cultures.

Efficient Inactivation of Clinically Relevant Antimicrobial Drug Concentrations by BacT/Alert or Bactec Resin-Containing Media in Simulated Adult Blood Cultures

We assessed the antimicrobial-inactivation capability of BacT/Alert (FA Plus and FN Plus) or Bactec (Plus Aerobic/F and Plus Anaerobic/F) media for 40 antibiotic-bacterium combinations in simulated adult blood cultures. Aside from high recovery rates (93.2% and 88.4%, respectively), we showed that at the lowest but clinically relevant antibiotic concentrations, both BacT/Alert and Bactec media recovered all the organisms tested with drugs except for Escherichia coli, which was tested in the presence of meropenem. Delayed recoveries were mainly associated with vancomycin.

Best Practices of Blood Cultures in Low- and Middle-Income Countries

Bloodstream infections (BSI) have a substantial impact on morbidity and mortality worldwide. Despite scarcity of data from many low- and middle-income countries (LMICs), there is increasing awareness of the importance of BSI in these countries. For example, it is estimated that the global mortality of non-typhoidal Salmonella bloodstream infection in children under 5 already exceeds that of malaria. Reliable and accurate diagnosis of these infections is therefore of utmost importance. Blood cultures are the reference method for diagnosis of BSI. LMICs face many challenges when implementing blood cultures, due to financial, logistical, and infrastructure-related constraints. This review aims to provide an overview of the state-of-the-art of sampling and processing of blood cultures, with emphasis on its use in LMICs. Laboratory processing of blood cultures is relatively straightforward and can be done without the need for expensive and complicated equipment. Automates for incubation and growth monitoring have become the standard in high-income countries (HICs), but they are still too expensive and not sufficiently robust for imminent implementation in most LMICs. Therefore, this review focuses on "manual" methods of blood culture, not involving automated equipment. In manual blood cultures, a bottle consisting of a broth medium supporting bacterial growth is incubated in a normal incubator and inspected daily for signs of growth. The collection of blood for blood culture is a crucial step in the process, as the sensitivity of blood cultures depends on the volume sampled; furthermore, contamination of the blood culture (accidental inoculation of environmental and skin bacteria) can be avoided by appropriate antisepsis. In this review, we give recommendations regarding appropriate blood culture sampling and processing in LMICs. We present feasible methods to detect and speed up growth and discuss some challenges in implementing blood cultures in LMICs, such as the biosafety aspects, supply chain and waste management.

Effects of Clinically Meaningful Concentrations of Antipseudomonal β-Lactams on Time to Detection and Organism Growth in Blood Culture Bottles

The effectiveness of antimicrobial binding resins present in blood culture (BC) bottles in removing meropenem, ceftolozane-tazobactam, and ceftazidime-avibactam is unknown. We assessed the time to detection (TTD) and growth of 2 Pseudomonas aeruginosa isolates in the presence of clinically meaningful concentrations of these antibiotics. Bactec Plus Aerobic/F and BacT/Alert FA Plus BC bottles were inoculated with one of two isolates (1 meropenem susceptible and 1 resistant), followed by fresh whole blood containing the peak, midpoint, or trough plasma concentrations for meropenem, ceftolozane-tazobactam, and ceftazidime-avibactam. Matching bottles were loaded into their respective detection instruments and a standard incubator at 37°C, with TTD and CFU being monitored for up to 72 h. Bacterial growth was observed for 11/48 (22.9%), 22/48 (45.8%), and 47/48 (97.9%) of all BC bottles inoculated with the peak, midpoint, and trough concentrations, respectively (P ≤ 0.001). When P. aeruginosa was isolated, the TTD was typically <26 h, and no differences between Bactec and BacT/Alert bottles were observed. In both systems, meropenem was removed to a greater degree than were ceftolozane and ceftazidime; however, concentrations for all antibiotics remained above the MIC for the susceptible organisms at 12 h. BC bottles containing antibiotic binding resins may not sufficiently inactivate achievable concentrations of meropenem, ceftolozane-tazobactam, and ceftazidime-avibactam. The consistent identification of both P. aeruginosa isolates was observed only in the presence of antibiotic trough concentrations. To minimize false-negative BC results for patients already receiving these antibiotics, cultures should be collected just prior to the next dose, when antibiotic concentrations are lowest.