Anaerobic Bloodstream Infections Research Articles

An Eleven-Year Retrospective Survey of Anaerobic Bloodstream Infection in Adults in a General Hospital.

During conditions accompanied by the disruption of normal mucosal barriers, anaerobic bacteria, which a part of normal human mucosal microflora, may cause various infections. In this study, clinical features of anaerobic bloodstream infections (BSI) in a general hospital in China were investigated. Patients with anaerobic BSI were retrospectively enrolled between 2012 and 2022. Demographic data, clinical manifestations, antibiotic treatments, and disease outcomes were analyzed. In total, 391 anaerobic bacterial strains were isolated from 381 patients aged older than 11 years of age. Given that medical records of 47 patients were missing, 334 patients were included in the clinical investigation. Patients with anaerobic BSI included in the study were predominantly older than 50 years of age. Intra-abdominal infections were the most common source of anaerobic BSI (59%), followed by those of the female genital tract (10.2%) and lower respiratory tract (7.2%). Among the isolates, Bacteroides and Clostridium spp. were the most frequently isolated anaerobes. Most of the patients received antibiotic therapy. The crude mortality was 4.5%. The detection rate of anaerobic BSI in Ningxia, China, remained relatively stable from 2012 to 2022. These results provide a reference for the diagnosis and empirical treatment of anaerobic BSI in this region of China. Continuous mul-ticenter studies should be conducted to monitor the incidence of anaerobic BSI and drug resistance of anaerobic isolates to improve the treatment outcomes of patients.

Differences between bloodstream infections involving Gram-positive and Gram-negative anaerobes

BackgroundThe objectives of this study were to describe differences between bloodstream infections involving Gram-positive (GP) and Gram-negative (GN) anaerobic bacteria. MethodsPatients with clinically significant anaerobic bacteremia detected between October 2016 and July 2022 in a tertiary hospital in Granada (Spain) were retrospectively included. Species identification was performed by MALDI-TOF MS and/or molecular methods. The association between variables was analyzed using contingency tables, applying the chi-square test when expected frequencies were adequate and the Fisher exact test when not. Variables were gathered at the time of the first positive blood culture. ResultsOut of 237 cases of anaerobic bloodstream infections detected, 127 (53.6%) were GN. Crude mortality was 20.3%, corresponding to 48 patients who died of causes directly attributable to bacteremia. The presence of malignant disease (p = 0.011), abdominal and/or pelvic surgery (p = 0.001), and transplantation (p = 0.008) were significantly associated with bacteremia due to GN bacteria, while the presence of diabetes mellitus was significantly associated with bacteremia due to GP bacteria (p = 0.022). The presence of both septic shock and mortality was more frequently associated with bacteremia due to GN versus GP bacteria. ConclusionsThe association of certain variables with the presence of bloodstream infections due to GP or GN anaerobic bacteria may assist in selecting the optimal empirical therapeutic approach and improving the outcome of patients with these types of infection.

Community-onset anaerobic bloodstream infection, predisposing factors, and impact on survival: A prospective cohort study

BackgroundFew studies have examined the outcomes and predisposing risk factors for anaerobic bloodstream infections (BSIs). ObjectiveTo determine the survival impact of aerobic versus anaerobic BSI, a prospective cohort study was conducted. MethodsWe prospectively enrolled emergency department patients at a tertiary medical center with BSIs determined by laboratory testing between 2015 and 2016. Anaerobic and aerobic BSIs were compared for demographics, comorbidities, and sources of infection. Several independent risk factors were identified in a multivariable logistic regression model. Using propensity score (PS) matched data, an analysis of survival effects associated with anaerobic BSI has been conducted. ResultsOver a 2-year period, there were 1,166 episodes of BSI, of which 61 (5.2%) occurred as anaerobic episodes. Anaerobic BSIs were strongly associated with intra-abdominal infection (odds ratio [OR] 6.03, 95%CI 2.78–13.09), liver abscess (OR 3.92, 95%CI 1.47–10.45), skin and soft-tissue infection (OR 2.65, 95%CI 1.26–5.62), and metastatic cancer (OR 2.40, 95%CI 1.13–5.08) as the main positive predictors. Negative predictors included diabetes mellitus (OR 0.38, 95%CI 0.18–0.78), thrombocytopenia (OR 0.33, 95%CI 0.18–0.60), and urinary tract infection (OR 0.15, 95%CI 0.04–0.62). Anaerobic BSIs were not associated with worse prognosis after PS-matched analysis (hazard ratio [HR] 1.40, 95%CI 0.44–4.41) in our cohort. ConclusionsA significant percentage of community-onset BSI was due to anaerobic BSI. Anaerobic BSI can have a detrimental outcome if there are underlying comorbidities, high-risk infection sites, and inappropriate antibiotic choices. The findings of our study may contribute to the prescription of empiric anti-anaerobe antibiotics.

Anaerobic bloodstream infections in Italy (ITANAEROBY): A 5-year retrospective nationwide survey

IntroductionA lack of updated data on the burden and profile of anaerobic bloodstream infections (ABIs) exists. We assessed the incidence of ABIs and trends in antimicrobial resistance in anaerobes isolated from blood in Italy. Material and methodsWe conducted a retrospective study on 17 Italian hospitals (2016–2020). Anaerobes isolated from blood culture and their in vitro susceptibility profiles (EUCAST-interpreted) were registered and analyzed. ResultsA total of 1960 ABIs were identified. The mean age of ABIs patients was 68.6 ± 18.5 years, 57.6% were males. The overall incidence rate of ABIs was 1.01 per 10.000 patient-days. Forty-seven% of ABIs occurred in medical wards, 17% in ICUs, 14% in surgical wards, 7% in hemato-oncology, 14% in outpatients. The three most common anti-anaerobic tested drugs were metronidazole (92%), clindamycin (89%) and amoxicillin/clavulanate (83%). The three most common isolated anaerobes were Bacteroides fragilis (n = 529), Cutibacterium acnes (n = 262) and Clostridium perfringens (n = 134). The lowest resistance rate (1.5%) was to carbapenems, whereas the highest rate (51%) was to penicillin. Clindamycin resistance was >20% for Bacteroides spp., Prevotella spp. and Clostridium spp. Metronidazole resistance was 9.2% after excluding C. acnes and Actinomyces spp. Bacteroides spp. showed an increased prevalence of clindamycin resistance through the study period: 19% in 2016, 33% in 2020 (p ≤ 0.001). ConclusionsOur data provide a comprehensive overview of the epidemiology of ABIs in Italy, filling a gap that has existed since 1995. Caution is needed when clindamycin is used as empirical anti-anaerobic drug.

Venous thromboembolism is not a risk factor for the development of bloodstream infections in critically ill COVID-19 patients

Venous thromboembolism is not a risk factor for the development of bloodstream infections in critically ill COVID-19 patients

Application of MALDI-TOF MS to assess clinical characteristics, risk factors, and outcomes associated with anaerobic bloodstream infection: a retrospective observational study

BackgroundCorrectly identifying anaerobic bloodstream infections (BSIs) is difficult. However, a new technique, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), enables more accurate identification and appropriate treatment. Anaerobic BSIs identified by MALDI-TOF MS were retrospectively analyzed to determine the clinical and microbiological features and patient outcomes based on the anaerobic genera or group.MethodsMedical records of patients with anaerobic BSIs were used to conduct a single-center retrospective cohort study from January 2016 to December 2020 in Nagoya, Japan. Multivariate logistic regression analysis was performed to determine the independent risk factors for in-hospital mortality.ResultsOf the 215 patients with anaerobic BSIs, 31 had multiple anaerobic organisms in the blood culture, including 264 total episodes of anaerobic BSIs. Bacteroides spp. were isolated the most (n = 74), followed by gram-positive non-spore-forming bacilli (n = 57), Clostridium spp. (n = 52), gram-positive anaerobic cocci (GPAC) (n = 27), and gram-negative cocci (n = 7). The median patient age was 76 years; 56.7% were male. The most common focal infection site was intra-abdominal (36.7%). The in-hospital mortality caused by anaerobic BSIs was 21.3%, and was highest with Clostridium spp. (36.5%) and lowest with GPAC (3.7%). Age, solid tumors, and Clostridium spp. were independent risk factors for in-hospital mortality.ConclusionsWe identified current anaerobic BSI trends using MALDI-TOF MS and reported that mortality in patients with anaerobic BSIs patients was highest with Clostridium spp. infections.

Clinical and microbiological characteristics of Eggerthella lenta bacteremia at a Japanese tertiary hospital

Eggerthella lenta is an important cause of anaerobic bloodstream infections and is associated with high mortality. However, there are few reports of E. lenta infection in Japan. This study aimed to evaluate the clinical and microbiological characteristics of bacteremia caused by E. lenta in Hiroshima, Japan. We retrospectively analyzed E. lenta bacteremia patients at the Hiroshima University Hospital between January 2012 and December 2020. During the study period, 14 patients with E. lenta bacteremia were identified. All E. lenta isolates were cultured in anaerobic bottles, and the median time to blood culture positivity was 52.9 h. In most cases (85.6%), the source of E. lenta bacteremia was associated with intra-abdominal infections, and colon perforation was the most frequent source of E. lenta bacteremia (42.9%, n = 6). Antimicrobial susceptibility testing showed high minimal inhibitory concentrations (MIC) of piperacillin-tazobactam (TZP) and 100% susceptibility to ampicillin-sulbactam, carbapenems, and metronidazole. This study demonstrates that E. lenta bacteremia is associated with intra-abdominal infections, particularly colon perforation, and a high MIC of TZP. When gram-positive anaerobes are detected in the blood cultures of patients with severe intra-abdominal infections, clinicians should suspect E. lenta, and it may be better to change antimicrobial agents from TZP.

Relevance of anaerobic bacteremia in adult patients: A never-ending story?

Obligate anaerobic bacteria are considered important constituents of the microbiota of humans; in addition, they are also important etiological agents in some focal or invasive infections and bacteremia with a high level of mortality. Conflicting data have accumulated over the last decades regarding the extent in which these pathogens play an intrinsic role in bloodstream infections. Clinical characteristics of anaerobic bloodstream infections do not differ from bacteremia caused by other pathogens, but due to their longer generation time and rigorous growth requirements, it usually takes longer to establish the etiological diagnosis. The introduction of matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) has represented a technological revolution in microbiological diagnostics, which has allowed for the fast, accurate and reliable identification of anaerobic bacteria at a low sample cost. The purpose of this review article is to summarize the currently available literature data on the prevalence of anaerobic bacteremia in adults for physicians and clinical microbiologists and to shed some light on the complexity of this topic nowadays.

Short-term culture for rapid identification of anaerobic bacteria from blood cultures

Identification of anaerobic bacteria causing blood stream infections (BSI) is challenging. This study describes the epidemiology of anaerobic BSI at a tertiary care hospital and the performance of a rapid method for identification of anaerobic bacteria from blood cultures over three years, between June 2015 and June 2018. Short-term culturing is a low-cost user-friendly method and may be used for rapid identification of bacteria from positive blood cultures by matrix-associated laser desorption ionization time of flight (MALDI-TOF). Short-term culturing is performed after Gram staining on all positive blood culture bottles (BCBs) before 10:30 a.m. in our laboratory. Successful short-term cultures were defined as growth and reliable MALDI-TOF result in maximum 8 h after culture positivity. Data pertaining to unique anaerobic episodes and short-term cultures was collected retrospectively from our laboratory information system. Overall, during the three-year period, 692 unique anaerobic episodes (including Propionibacterium spp) were isolated. A total of 17 anaerobic bacterial genera were isolated in our laboratory, with 5 GNB genera and 12 GPB genera. The most prevalent bacteria were Bacteroides spp. 266/692 (38%), Propionibacterium spp. 128/692 (18%), Clostridium spp. 103/692 (15%), Fusobacterium spp. 34/692 (5%), and Actinomyces spp. 34/692 (5%). We performed short-term cultures on 270/564 (48%) clinically relevant episodes (excluding Propionibacterium spp) on chocolate agar plates. Growth within 8 h from culture positivity was detected in 33/270 (12%) short-term cultures. There were 22/33 (67%) gram negative (GNB) and 11/33 (33%) gram positive bacteria (GPB). Only two genera were identified: Bacteroides spp 22/33 (67%) and Clostridium spp 11/33 (33%). Thus, short-term culturing can function as a low-cost add-on to already existing protocols involving MALDI-TOF, where both GNB and GPB can be identified.

Eggerthella lenta Bloodstream Infections Are Associated With Increased Mortality Following Empiric Piperacillin-Tazobactam (TZP) Monotherapy: A Population-based Cohort Study.

Eggerthella lenta is a anaerobic gram-positive bacilli associated with polymicrobial intraabdominal infections. Recently, E. lenta was recognized as an important cause of anaerobic bloodstream infections (BSIs) associated with high mortality. Eggerthella lenta has been reported to have high minimal inhibitory concentrations (MICs) to piperacillin-tazobactam (TZP), a broad-spectrum antibiotic with anaerobic coverage commonly used in multiple centers for empiric treatment of abdominal sepsis. We describe a retrospective population-based analysis of invasive E. lenta infections from 2009 through 2015. A logistic regression analysis for 30-day mortality risk factors was conducted. We identified 107 E. lenta infections, 95 (89%) were BSIs, 11 (10%) skin and soft tissue infections, and 1 intraabdominal abscess. Polymicrobial infections were found in 40%; 72% of isolates were from a gastrointestinal source, most commonly appendicitis (33%) of which two-thirds were perforated. TZP MIC50 and MIC90 for E. lenta isolates were 32 μg/mL and 64 μg/mL, respectively. The overall 30-day mortality for BSI was 23% and was independently associated with empiric TZP monotherapy (odds ratio [OR], 4.4; 95% confidence interval [CI], 1.2-16; P = .02) and intensive care unit stay (OR, 6.2; 95% CI, 1.4-27.3; P = .01). Thirty-day mortality rates were significantly influenced by the use of different TZP MIC breakpoints. Our results demonstrate the increased recognition of E. lenta as an anaerobic opportunistic pathogen and highlight the need for improved empiric antimicrobial guidelines and TZP MIC breakpoints with better correlation to clinical outcomes to guide appropriate management of invasive E. lenta infections.

Temporal Trends in Blood Stream Infection Isolates from Surgical Patients.

Blood stream infections (BSIs) are a common source of morbidity and death in hospitalized patients. We hypothesized that the proportions of bacteremia from gram-positive and fungal pathogens have decreased over time, whereas rates of gram-negative bacteremia have increased as a result of better central venous catheter management. All U.S. Centers for Disease Control and Prevention-defined BSIs in patients treated on the general surgery and trauma services at our institution between January 1, 1998, and December 31, 2009 were identified prospectively. These cases were analyzed on a yearly basis to compare rates of various infections over time. The Cochran-Armitage test for trend was used to evaluate categorical data, whereas the Jonckheere-Terpstra test for ordered values was used to analyze continuous data. A total of 1,040 patients had 1,441 episodes of BSI caused by 1,632 strains of bacteria or fungi. There was no difference over time in the proportion of BSI among overall infections. Rates of BSI for gram-negative and fungal pathogens increased over time (p=0.03 and<0.0001, respectively), whereas rates of gram-positive BSI decreased (p<0.0001). Positive changes in anaerobic BSI approached statistical significance. Although our hypothesis was only partly true, over the last 12 y, our institution clearly has witnessed a shift in the types of organisms causing BSIs. There was a decrease in the rates of BSI caused by gram-positive pathogens with an associated increase in the rates of BSI of infections by fungal and gram-negative pathogens. Interventions to reduce institutional rates of BSI should include targeted therapies based on historical institutional trends.

Population-based assessment of the incidence, risk factors, and outcomes of anaerobic bloodstream infections

Anaerobes are a relatively uncommon but important cause of bloodstream infection. However, their epidemiology has not been well defined in non-selected populations. We sought to describe the incidence of, risk factors for, and outcomes associated with anaerobic bacteremia. Population-based surveillance for bacteremia with anaerobic microorganisms was conducted in the Calgary area (population 1.2 million) during the period from 2000 to 2008. A total of 904 incident cases were identified, for an overall population incidence of 8.7 per 100,000 per year; 231 (26 %) were nosocomial, 300 (33 %) were healthcare-associated community-onset, and 373 (41 %) were community-acquired. Elderly males were at the greatest risk. The most common pathogens identified were: Bacteroides fragilis group (3.6 per 100,000), Clostridium (non-perfringens) spp. (1.1 per 100,000), Peptostreptococcus spp. (0.9 per 100,000), and Clostridium perfringens (0.7 per 100,000). Non-susceptibility to metronidazole was 2 %, to clindamycin 17 %, and to penicillin 42 %. Relative to the general population, risk factors for anaerobic bloodstream infection included: male sex, increasing age, a prior diagnosis of cancer, chronic liver disease, heart disease, diabetes mellitus, stroke, inflammatory bowel disease, human immunodeficiency virus (HIV) infection, chronic obstructive pulmonary disease (COPD), and/or hemodialysis-dependent chronic renal failure (HDCRF). The 30-day mortality was 20 %. Increasing age, nosocomial acquisition, presence of malignancy, and several other co-morbid illnesses were independently associated with an increased risk of death. Anaerobic bloodstream infection is responsible for a significant burden of disease in general populations. The data herein establish the extent to which anaerobes contribute to morbidity and subsequent mortality. This information is key in developing preventative, empiric treatment and research priorities.

Bacteriemia por anaerobios estrictos: estudio de 68 pacientes

There is some controversy regarding the current rates of anaerobic bacteremia. Some authors have described an increasing incidence in recent years, whereas others report declining rates. There is even debate over whether to routinely perform anaerobic blood cultures. We present a prospective analysis of anaerobic bloodstream infections diagnosed at our medical center from January 2003 to May 2008. Sixty-eight patients had bloodstream infection caused exclusively by anaerobic bacteria. Median age was 64+/-19 years and 63.2% had at least one comorbid condition, including 20.6% with a solid neoplasm, often related to the gastrointestinal tract. The main focus of anaerobic bacteremia was the abdomen (42.6%). The most common isolates were several species from the Bacteroides fragilis group (36.7%), Clostridium spp. (17.6%), Peptostreptococcus spp. (16.1%), and Prevotella spp. (16.1%). Empirical antimicrobial treatment was adequate in 69.1%. Overall mortality was 23.5%, and bacteremia-related mortality was 9.2%. Sepsis, septic shock, and a Pitt score >4 were independent predictors of mortality. The incidence of anaerobic bacteremia in our hospital was 0.89 cases per 1000 hospital admissions. Patients at high risk were elderly persons with associated underlying diseases including malignant disease. Mortality was high.

Use of anaerobically incubated media to increase yield of positive blood cultures in children.

During a 3-year period we received 10024 blood samples for culture from pediatric patients. Overall 181 episodes of significant bacteremia were documented. During the study period we would have missed 35 (19%) of all significant episodes of pediatric bloodstream infections if we had not been using the anaerobically incubated blood bottle. Anaerobically incubated blood samples are also necessary in the pediatric population.

Risk factors for anaerobic bloodstream infections in bone marrow transplant recipients.

The incidence of anaerobic bloodstream infections (BSI) in patients who underwent bone marrow transplantation (BMT) recently increased at our institution. A retrospective case-control study of patients undergoing BMT from January 1995 through December 1998 was performed to determine the microbiological characteristics, epidemiology, and outcome of anaerobic BSI and to identify independent risk factors for infection. Anaerobic BSI occurred in 23 patients, for a rate of 4 BSIs per 100 BMT procedures, and it accounted for 17% of all BSIs that occurred during the study period. Infection occurred at a mean (+/- standard deviation) of 7+/-4 days after BMT and 7+/-5 days after the onset of neutropenia. Fusobacterium nucleatum was the most frequently isolated pathogen (in 17 patients), followed by Leptotrichia buccalis (in 4), Clostridium septicum (in 1), and Clostridium tertium (in 1). Two case patients (9%) died. Severity of mucositis was an independent predictor of anaerobic BSI (odds ratio, 4.4; P=.01). Controlling mucositis is critical for the prevention of anaerobic BSI in this patient population.

Reevaluation of Anaerobic Blood Cultures in a Veteran Population

Studies suggest that the selective use of anaerobic blood cultures may represent a more cost-effective laboratory approach when anaerobic bacterial infection is suspected. A 5-year retrospective study was done at a Veterans' Affairs hospital to determine the utility of routinely including anaerobic blood culture when sampling for bacteremia. A total of 22,075 anaerobic blood cultures were collected from our adult population. Significant anaerobic pathogens were isolated from only 0.14% of these blood cultures. An anaerobic infection could have been suspected in 92% of our patients. Significant anaerobic bloodstream infections occurred in only 0.14% of blood cultures. In addition, the majority of the patients identified with anaerobic bacteremia had clinical conditions that would have suggested a high likelihood of anaerobic bacteremia. These observations suggest that selective rather than routine use of anaerobic blood cultures may be appropriate in a veteran population.

Anaerobic Bacteremia in a Neutropenic Patient with Oral Mucositis

An increasing number of anaerobic bloodstream infections in neutropenic cancer patients have been reported in the last decade. The type of anaerobes isolated from most of these patients suggests an oral source of infection. We describe a case of anaerobic bacteremia in a neutropenic patient with oral mucositis that highlights the importance of considering these organisms when selecting empiric prophylactic or therapeutic antimicrobial regimens, especially in the setting of periodontal disease or oral mucositis.