Recovery and time to growth of isolates in blood culture bottles: Comparison of BD Bactec Plus Aerobic/F and BD Bactec Plus Anaerobic/F bottles

Identification and distribution of anaerobic bacteria isolated from clinical specimens in a University Hospital: 4 years’ experience

Anaerobes, which are components of microbiota, can cause life-threatening infections. Because of their fastidious nature, they are difficult to isolate and are often overlooked. The goal of this study was to identify the anaerobic bacteria isolated from clinical specimens at the Central Laboratory of Hacettepe University Hospital in 2015-2018 and to evaluate the distribution of the isolated bacterial species among the different specimen types. The anaerobic bacteria isolated from the specimens were identified by the conventional methods and MALDI-TOF MS.

Overall, 15,300 anaerobic cultures were studied. Of these, 14,434 (94.3%) were blood samples and 866 (5.7%) were other clinical specimens. A total of 138 anaerobic bacteria were isolated: 62 (44.9%) were isolated from blood samples and 76 (55.1%) from other specimens. The most isolated anaerobes from blood cultures were Bacteroides spp. (41.9%), followed by Cutibacterium acnes (25.8%) and Clostridium spp. (9.7%). The most isolated anaerobes from the other specimens were Gram-negative bacilli, including Bacteroides spp. (15.8%), Fusobacterium spp. (14.5%), Prevotella spp. (14.5%), and Porphyromonas spp. (2.6%). Anaerobic Finegoldia magna represented the major species among the isolated Gram-positive bacteria (10.5%). Anaerobic growth was observed in 0.4% of all the blood cultures and in 5.8% of the positive blood cultures. The results of our study showed that the incidence of anaerobic bacteremia was stable during the 2015-2018 period.

Effects of Blood Culture Aerobic/Anaerobic Bottle Collection Patterns from Both Sides of the Body on Positive Blood Culture Rate and Time-to-Positivity

Background

Although the principles for blood cultures (BCs) guidelines provide a recommendation for collection patterns, the complexity of clinical practice occasionally prompts clinicians to adopt non-standard collection patterns. Here, we investigate the influences of different BC collection patterns on detection of pathogens.

Methods

The BC collection patterns of 96 hospitals were surveyed online. And a retrospective study of BC data from a tertiary hospital was conducted.

Results

The results showed that 53.1% of hospitals adopted the recommended patterns. Among the 1439 episodes of true-positive BCs, 67.4% were found in both the left- and right-sided bottles; 58.2% were found in both aerobic and anaerobic bottles.

Conclusion

The present study suggested that the rate of standard collection patterns of blood culture was low and the non-standard collection patterns were associated with decreased detection of pathogens. Simultaneous collection of blood on the left and right sides was recommended as an effective pattern of BC collection.

Midtrimester amniotic fluid from healthy pregnancies has no microorganisms using multiple methods of microbiologic inquiry

BACKGROUND

There is controversy about whether the amniotic fluid contains bacteria. With the use of sequencing-based methods, recent studies report that the amniotic fluid is colonized by microorganisms. However, background-contaminating DNA might lead to false-positive findings when such a low microbial biomass sample is examined.

OBJECTIVE

The purpose of this study was to determine whether the midtrimester amniotic fluid of patients who subsequently had normal pregnancy outcomes contains a microbial signature.

STUDY DESIGN

In this prospective cohort study, 42 amniotic fluid samples were collected from 37 pregnancies (5 twin and 32 singletons) during genetic amniocentesis in the midtrimester. The subsequent pregnancy outcomes of all the participants were followed. Multiple methods were used to detect the presence of microorganisms in this study, which included cultivation, quantitative real-time polymerase chain reaction, and 16S ribosomal RNA gene sequencing. Multiple positive control samples (n=16) served as quality control samples and included 3 adult fecal samples, 4 vaginal swabs, and 9 artificial bacterial communities that were run in parallel with negative control samples (n=12) that included 4 samples from the hospital operating room and 8 samples from the laboratory, to account for background-contaminating DNA during each step of the experiments.

RESULTS

No bacteria under anaerobic or aerobic conditions or genital mycoplasmas were cultured from any of the amniotic fluid samples. Quantitative polymerase chain reaction did not reveal greater copy numbers of 16S ribosomal RNA gene in amniotic fluid samples than in negative control samples. 16S Ribosomal RNA gene sequencing did not indicate a significant difference in the microbial richness or community structures between amniotic fluid and negative control samples.

CONCLUSION

With multiple methods of microbiologic inquiry, no microorganisms were identified in the midtrimester amniotic fluid of healthy pregnancies with a normal pregnancy outcome.

Role of Anaerobic Blood Cultures in Neonatal Bacteremia

BACKGROUND

Evaluation for neonatal sepsis routinely includes performing both aerobic and anaerobic blood cultures despite our lack of knowledge of the true incidence of anaerobic bacteremia in this age group and the consequences of not performing these paired cultures.

METHODS

We performed a retrospective review of all blood cultures performed for neonates in a children's hospital. Clinically significant pathogens were defined as microorganisms that rarely are considered to be contaminants, that were recovered from multiple blood cultures or sites, or were considered significant according to the patient's attending physician. The chart of every patient with positive culture results was reviewed for patient characteristics.

RESULTS

A total of 662 culture sets among 403 patients were obtained between November 1, 2013, and April 30, 2015. A clinically significant organism was isolated from 64 (9.7%) culture sets from 25 patients (1.9% contamination rate). A total of 56 organisms were isolated; 35 (62.5%) grew from both the aerobic and anaerobic bottles, 19 (33.9%) grew from the anaerobic bottle alone, and 2 (3.6%) grew from the aerobic bottle alone. One (0.2%) obligate anaerobic bacterium (Clostridium symbiosum) was identified.

CONCLUSIONS

Although the incidence of anaerobic bacteremia in neonates is rare, anaerobic culture remains important in this population, given the increased yield of both aerobic and facultative anaerobic organisms isolated from anaerobic blood culture bottles.