Clinical characteristics associated with mortality of patients with anaerobic bacteremia

Effects of extended anaerobic antibiotic coverage on anaerobic bloodstream infection: A multisite retrospective study

OBJECTIVES

Routine clinical practice with extended anaerobic antibiotic coverage (EAC) has been recently reconsidered for several infections; however, its benefits remain unclear even in patients with anaerobic bacteremia (AB). Here, we aimed to elucidate the effects of EAC on AB prognosis.

METHODS

A multicenter retrospective observational study was conducted in patients with AB. Multivariate logistic regression analysis was performed to assess the effect of EAC on 30-day mortality. Inverse probability of treatment weighting analysis was performed to confirm the robustness of the findings.

RESULTS

In total, 483 patients were included, of whom 387 received EAC and 96 received limited anaerobic antibiotic coverage (LAC). Atypical foci of anaerobic infection, such as urinary tract infection and pneumonia, together with undetectable infection foci, comprised a larger proportion of infection foci in the LAC group than that in the EAC group (46.9% vs 30.5%). The 30-day mortality rates of the EAC and LAC groups were similar (12.5% and 14.2%, respectively; P = 0.664). Primary analysis revealed that EAC was not significantly associated with high mortality (odds ratio [OR], 1.42; 95% confidence interval [CI], 0.7-2.8), whereas source control significantly reduced this risk (OR, 0.28; 95% CI, 0.2-0.5). The sensitivity analysis results were consistent with those of the primary analyses.

CONCLUSION

This study demonstrated a less significant effect of initial EAC on AB compared with source control, particularly on AB with atypical infection foci. These findings would prompt reconsideration of the necessity of an initial EAC in several infections.

Utility of anaerobic blood cultures in the clinical management of infectious patients

Paired aerobic/anaerobic cultures are routinely performed for the diagnosis of bacteraemia. This study aimed to assess the utility of anaerobic cultures in the management of infectious patients. All positive blood cultures taken from adult patients in a French hospital between November 2018 and March 2020 were evaluated. Clinical and microbiological data were collected for all patients with a positive anaerobic culture. Among the 17,272 positive pairs, 1402 included an anaerobic culture (8 %). In the 487 patients with anaerobic bacteraemia, the most commonly detected microorganisms were Enterobacterales (45 %), Staphylococcus aureus (16 %) and obligate anaerobes (6 %). In the 30 patients with obligate anaerobic bacteraemia, the most commonly detected bacterial species were Bacteroides spp. (30 %). When the bacteraemia-causing microorganism grew in both cultures (76 %), the anaerobic culture became positive prior to the aerobic culture in 54 % of cases-mainly for Enterobacterales and S. aureus. Our findings support the utility of performing anaerobic cultures.

Urethrocutaneous fistula and subcutaneous abscess in the inguinal region with bacteremia caused by Bilophila wadsworthia in a Japanese patient: A case report

Bilophila wadsworthia is an anaerobic, gram-negative bacillus commonly associated with acute appendicitis. However, bacteremia is exceedingly rare. Herein, we report a case of B. wadsworthia bacteremia associated with a urethrocutaneous fistula and a subcutaneous abscess in the left inguinal region. A 75-year-old man was referred to our hospital due to persistent fever despite piperacillin treatment. The patient was diagnosed with a urethrocutaneous fistula and a subcutaneous abscess in the left inguinal region. B. wadsworthia was isolated from his blood culture and identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Subsequently, the patient underwent a four-week course of piperacillin-tazobactam therapy. Since a susceptibility breakpoint has not been established for B. wadsworthia, standardized treatment guidelines are currently unavailable. This case represents the first successful treatment of B. wadsworthia bacteremia with piperacillin-tazobactam, suggesting it may be an effective therapeutic option for infections caused by B. wadsworthia.

Clinical and microbiological characteristics of anaerobic bacteremia during 1994-2019: A Danish population-based cohort study

OBJECTIVES

Bacteremia with anaerobic bacteria is generally a marker of severe prognosis. However, population-based data is lacking. Our aim was to describe the epidemiology and the 30-day mortality rate of anaerobic bacteremia in a Danish population-based setting.

METHODS

In this population-based cohort study, all first-time episodes of anaerobic bacteremia from the North Denmark Bacteremia Research Database during 1994-2019 were identified. Information on comorbidities, discharge diagnoses, and mortality was retrieved. 30-day mortality rates were calculated and a multivariate logistic regression analysis to identify risk factors for death was performed.

RESULTS

1750 episodes with anaerobic bacteremia were identified, corresponding to an incidence rate of 12.5 per 100,000 inhabitants (increasing from 11.2 in 1994-2014 to 17.7 in 2015-2019). Of these episodes, a third were polymicrobial, and the majority (70 %) of patients had one or more comorbid conditions. Abdominal infection was the source of bacteremia in 61 % of patients, while it was unknown for 15 %. The most frequently isolated genera were Bacteroides (45 %), Clostridium (20 %) and Fusobacterium (6 %). The overall crude 30-day mortality rate was 27 %, but rates were even higher for patients of high age, with liver disease, and solid tumors. The odds ratio (OR) for 30-day mortality was 1.32 for Clostridium species, and 1.27 for polymicrobial bacteremia with aerobic bacteria.

CONCLUSIONS

The incidence rate of anaerobic bacteremia increased, and the 30-day mortality rate remained high during the study period. Multiple factors influence 30-day mortality rates, including high age, liver disease, solid tumor, polymicrobial bacteremia, and bacteremia with Clostridium species.

Mortality risk factors and fulminant sub-phenotype in anaerobic bacteremia: a 10-year retrospective, multicenter, observational cohort study

PURPOSE

During the last decade, the incidence of anaerobic bacteremia (AB) has been increasing. Patients with AB may develop complex underlying diseases, which can occasionally be accompanied by fatal or fulminant outcomes. However, the risk factors for AB-related mortality remain unclear. Herein, we sought to elucidate the risk factors for AB-related mortality.

METHODS

In this multicenter, retrospective, observational study, we enrolled patients with culture-proven AB from six tertiary hospitals in Japan, between January 2012 and December 2021. Data on patient and infection characteristics, laboratory findings, treatment, and outcome were collected, and their associations with mortality were analyzed.

RESULTS

A total of 520 participants were included. The 30-day mortality in the study cohort was 14.0% (73 patients), and malignant tumors were frequently observed comorbidities in 48% of the entire cohort. Multivariable logistic regression analysis showed a Charlson comorbidity score of > 6, serum creatinine level of > 1.17 mg/dL, and hypotension to be independent risk factors for 30-day mortality in AB (odds ratios [ORs] 2.12, 2.25, and 5.12, respectively; p < 0.05), whereas drainage significantly reduced this risk (OR, 0.28; p < 0.0001). Twelve patients (2.3% of the whole cohort and 16.4% of the deceased patients) presented with extremely rapid progression leading to fatal outcome, consistent with "fulminant AB."

CONCLUSIONS

This study identified acute circulatory dysfunction and performance of drainage as independent predictive factors for 30-day AB-related mortality and revealed the existence of a fulminant AB sub-phenotype. Our findings could serve as a practical guide to predict the clinical outcomes of AB.

Recent Trends in Antimicrobial Resistance among Anaerobic Clinical Isolates

Anaerobic bacteria are normal inhabitants of the human commensal microbiota and play an important role in various human infections. Tedious and time-consuming, antibiotic susceptibility testing is not routinely performed in all clinical microbiology laboratories, despite the increase in antibiotic resistance among clinically relevant anaerobes since the 1990s. β-lactam and metronidazole are the key molecules in the management of anaerobic infections, to the detriment of clindamycin. β-lactam resistance is usually mediated by the production of β-lactamases. Metronidazole resistance remains uncommon, complex, and not fully elucidated, while metronidazole inactivation appears to be a key mechanism. The use of clindamycin, a broad-spectrum anti-anaerobic agent, is becoming problematic due to the increase in resistance rate in all anaerobic bacteria, mainly mediated by Erm-type rRNA methylases. Second-line anti-anaerobes are fluoroquinolones, tetracyclines, chloramphenicol, and linezolid. This review aims to describe the up-to-date evolution of antibiotic resistance, give an overview, and understand the main mechanisms of resistance in a wide range of anaerobes.

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

BACKGROUND

The objectives of this study were to describe differences between bloodstream infections involving Gram-positive (GP) and Gram-negative (GN) anaerobic bacteria.

METHODS

Patients 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.

RESULTS

Out 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.

CONCLUSIONS

The 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.

Antimicrobial susceptibility of anaerobic clinical isolates: A two-year surveillance

A total of 866 anaerobic strains isolated from clinical samples were tested by E-TEST for antimicrobial susceptibility. The most frequent antimicrobial resistance among the isolated genera, both Gram-positive and Gram-negative, was observed for clindamycin, and therefore, it cannot be considered as an empirical treatment. The antimicrobial resistance to benzylpenicillin was predominant among the Gram-negative bacteria, in particular the Bacteroides spp. The resistance percentages to meropenem and metronidazole are still low. However, metronidazole showed a considerable resistance in Finegoldia magna isolates, alone or in combination with other antibiotics. These data provide novel and useful epidemiological information on infections promoted by anaerobic bacteria.

Epidemiology and outcome of anaerobic bacteremia in a tertiary hospital

Despite a low incidence, anaerobic bacteremia remains a serious and often underestimated condition. This retrospective study aims to describe the epidemiology of anaerobic bacteremia and to identify risk factors affecting mortality and the impact of treatment. We included all positive anaerobic blood cultures from January 2018 to December 2019 at the University Hospital of Charleroi (Belgium). We identified 105 episodes of clinically significant anaerobic bacteremia (mean age of patients: 66.4 +/- 16.8 years). The main comorbidities were hypertension, chronic kidney disease, and diabetes. Bacteremia was community-acquired in 70.5% of the episodes. Two thirds of the blood cultures were mono-microbial, and the commonest bacteria found were Bacteroides fragilis group (31.4%), Fusobacterium spp. (17.1%) and Clostridium spp. (15.2%). The main sources of bacteremia were abdominal (35.2%), urinary (17.1%), osteoarticular (14.2%) and pulmonary (12.3%). Surgery within 30 days before hospitalization was more frequent in patients with nosocomial bacteremia (45.2% vs 2.7%, p &lt; 0.0001). An appropriate empirical antibiotic therapy was initiated in 74.7% of patients, and the median duration of antibiotic therapy was 10 [5 - 15] days. One third of patients had a surgical management. Patients who did not survive at day 30 (n = 23 [21.9%]) had significantly lower time to positivity (TTP) values than patients alive at day 30, presented more often with sepsis, had higher Charlson scores and chronic kidney disease, and were more likely to suffer from Clostridium spp. bacteremia. In a Cox proportional hazard analysis, sepsis (OR: 7.32 [95% CI: 2.83- 18.97], p&lt; 0.0001) was identified as an independent risk factors for 30-day mortality, whereas time to positivity ≥ 30 h (OR: 0.24 [95% CI: 0.07 - 0.84], p = 0.025) and an adequate empirical antibiotic therapy (OR: 0.37 [95% CI: 0.15 - 0.94], p = 0.037) were associated with better outcomes. Anaerobic bacteremia has a high mortality rate which justifies the maintenance of empirical antibiotic therapy.

In Vitro Efficacy of Antibiotic Combinations with Carbapenems and Other Agents against Anaerobic Bacteria

We investigated the in vitro efficacy of combinations of carbapenems with clindamycin (CLDM) and minocycline (MINO) against Bacteroides fragilis and Peptostreptococcus species. We selected the carbapenems imipenem, meropenem, panipenem, doripenem, and biapenem. To evaluate the antibiotic efficacy of these combination regimens, the fractional inhibitory concentration index (FICI) was calculated against clinical isolates. Consequently, combination regimens of each carbapenem with CLDM or MINO showed synergistic or additive effects against 83.3−100.0% and no antagonistic effects against P. anaerobius isolates. However, against the B. fragilis group (B. fragilis, B. thetaiotaomicron, and Parabacteroides distasonis), although the combination with other carbapenems and CLDM or MINO did not show remarkable synergistic effects, the combination regimen of IPM with CLDM or MINO indicated mainly additive antibiotic efficacies (FICIs: >0.5 to ≤1.0) to B. fragilis groups. Then, antagonistic effects were admitted in only 5.6% of B. fragilis groups. The effectiveness of antibiotic combination therapy against pathogenic anaerobes has remained unclear. Then, our results can provide new insights to explore the effective combination regimens against multidrug-resistant anaerobic bacteria as empirical and definitive therapies, while this study used only carbapenem susceptible isolates. Hence, further studies are needed to use highly antibiotic-resistant anaerobic isolates to carbapenems.

Bloodstream infection caused by Bacteroides caccae in a patient with renal hypertension: a case report

Bacteroides caccae is an anaerobic bacterium with a reportedly high isolation rate; however, it rarely causes bloodstream infections. Patients with hypertension are at increased risk of developing anaerobic bacterial infection. In this study, we report a case of bacteremia caused by B. caccae in a patient with renal hypertension and gastrointestinal hemorrhage. This study describes the clinical manifestations of bloodstream infection involving B. caccae to provide guidance for laboratory technicians and clinicians. A 42-year-old Chinese man was admitted for gastrointestinal hemorrhage and subsequently diagnosed with anaerobic blood infection. The pathogenic bacteria isolated from anaerobic blood culture bottles were identified as B. caccae by using an automatic bacterial identification instrument and mass spectrometry (MS). B. caccae is an intestinal opportunistic pathogen that can invade the intestinal mucosa and cause anaerobic bloodstream infection. Two or more sets of blood cultures and MS identification can greatly improve the positive detection rate of blood cultures of anaerobic bacteria. Furthermore, the increased drug resistance of anaerobic bacteria necessitates drug sensitivity tests for anaerobic bacteria in many hospitals. Thus, the early prevention and control of primary diseases with appropriate diagnoses and timely anti-infection therapies are necessary to reduce B. caccae bloodstream infection.

Rapid detection and surveillance of cfiA-positive Bacteroides fragilis using matrix-assisted laser desorption ionization time-of-flight mass spectrometry

OBJECTIVES

To perform surveillance of cfiA-positive Bacteroides fragilis using new subtyping software module, MALDI Biotyper Subtyping Module (MBT Subtyping Module), on MALDI-TOF MS system, and to evaluate the detection ability of the module.

METHODS

cfiA-positive strains were presumed using the module against B. fragilis isolated between 2006 and 2019. The cfiA gene was confirmed using PCR. In cfiA-positive B. fragilis, the insertion sequence (IS) elements were examined and the MBT STAR-BL assay was performed to examine meropenem hydrolysis activity.

RESULTS

Of the 396 B. fragilis strains included, the MBT Subtyping Module detected 33 presumptive cfiA-positive strains (8.3%), of which 32 harbored the cfiA gene. The sensitivity and specificity of the MBT Subtyping Module for detecting cfiA-positive B. fragilis were 100.0% and 99.7%, respectively. Of the 32 strains harboring the cfiA gene, seven strains possessed IS elements, which were thought to induce high cfiA expression. Meropenem hydrolysis was detected in all seven strains that were positive for both cfiA and IS elements, and they exhibited resistance to meropenem and imipenem. The overall non-susceptibility rates to meropenem and imipenem were 84.8% and 36.4%, respectively, in the 33 presumptive cfiA-positive strains.

CONCLUSION

The MBT Subtyping Module can detect cfiA-positive B. fragilis rapidly and accurately, supporting its use for surveillance of cfiA-positive B. fragilis in clinical settings.

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

Background

Correctly 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.

Methods

Medical 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.

Results

Of 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.

Conclusions

We 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.

Anaerobic resistance: should we be worried?

PURPOSE OF REVIEW

Anaerobic bacteria are implicated in a broad range of infections and can cause significant morbidity and mortality. As such, development of antimicrobial resistance (AMR) increases the risk of worse clinical outcomes and death.

RECENT FINDINGS

Anaerobe AMR is highly variable according to region and species included in the survey. The overall trend is to increasing resistance, particularly in Europe and Asia, and in the Bacteroides fragilis group and Clostridium sp. Conversely, with the decline in RT027, resistance in Clostridiodes difficile is decreasing. Resistance to moxifloxacin and clindamycin has reached 30-50%, whereas prevalence of metronidazole and carbapenem resistance is generally low. Infections due to multidrug anaerobes have been increasingly reported, with clinical studies demonstrating adverse clinical outcomes, including higher mortality, with anaerobic resistance or inappropriate therapy. The role of antimicrobial stewardship in the setting of increasing anaerobe resistance is yet to be fully elucidated.

SUMMARY

These findings highlight the importance of continuous surveillance in monitoring emerging trends in anaerobe AMR. Mean inhibitory concentrations should be reported due to variable susceptibility breakpoints and for detection of isolates with reduced susceptibility. At a local level, the clinical microbiology laboratory has a key role in identifying and undertaking susceptibility testing to inform individual patient management, develop local antibiograms and liaise with antimicrobial stewardship teams. A greater understanding of the clinical impact of anaerobic resistance and the role of antimicrobial stewardship in preventing resistance is required.

Clinical Findings and Antimicrobial Susceptibility of Anaerobic Bacteria Isolated in Bloodstream Infections

The objectives of this study were to report on the antimicrobial susceptibility of 141 clinically significant anaerobic bacteria isolated from bloodstream infections between January 2016 and April 2020 in a tertiary-care hospital in Granada (Spain) and to describe the main clinical features of the patients. Species identification was performed by MALDI-TOF MS (Bruker Daltonics, Billerica, MA, USA). Antimicrobial susceptibility tests were performed against penicillin, amoxicillin-clavulanic acid, imipenem, moxifloxacin, clindamycin, metronidazole, and piperacillin-tazobactam using the gradient diffusion technique and EUCAST breakpoints, except for moxifloxacin (CLSI breakpoints). The most frequent anaerobes were Bacteroides (43.9%, n = 62), Clostridium (24.1%, n = 34) and Gram-positive anaerobic cocci (GPACs) (15.6%, n = 22). Almost all tested anaerobes were susceptible to imipenem and amoxicillin-clavulanic acid, except for Bacteroides. High overall resistance rates to clindamycin were observed, especially for Gram-positive anaerobic cocci (GPACs) (54.5%) and for Bacteroides spp. (45.1%). Overall, low resistance rates to almost all antibiotics were observed for Clostridium. High resistance rates to penicillin were also observed for Gram-positive anaerobic bacilli (GPABs) (44.4%), as well as to metronidazole (22.2%), although only nine isolates were included. Antimicrobial susceptibility testing for anaerobes should always be performed in severe infections, such as those localized in the bloodstream. The information obtained contributes to selecting empirical treatments according with local data on resistance.

Anaerobic bacteraemia: A score predicting mortality

The objectives of this study were to report those variables which are readily identifiable at the bedside and that are able to predict mortality in patients with bacteraemia caused by anaerobes. Patients with clinically significant anaerobic bacteraemias detected between January 2016 and December 2019 in a tertiary hospital in Granada (Spain) were retrospectively included. Species identification was performed by MALDI-TOF MS and/or molecular methods. Finally, 136 cases of anaerobic bacteraemia were included, being the most frequent anaerobes Bacteroides (45.5%; n = 62), Clostridium (24.2%, n = 33), and Gram-positive anaerobic cocci (16.1%, n = 22). Crude mortality was 25.7%, corresponding to 35 patients who died, with 82.8% of deaths directly attributable to bacteraemia. A multivariable logistic regression model with non-parametric bootstrap estimation identified three variables that were independently and significantly associated with an increased risk of death: 1) hospitalization in the intensive care unit; 2) septic shock; and 3) presence of any kind of cancer. These variables were as recorded at the time that the first positive blood culture was obtained. An index score, obtained from these variables, was calculated and divided patients into two groups with increasing likelihood of mortality resulting from anaerobic bacteraemia. The sensitivity and specificity of a prediction of death based on this model were 65.2% and 97%, respectively.

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.

The effect of intervention by an antimicrobial stewardship team on anaerobic bacteremia

The effect of antimicrobial stewardship (AS) on anaerobic bacteremia is uncertain. This study aimed to assess the effect of interventions by the AS team (AST) on clinical and microbiological outcomes and antimicrobial use. An AS program was introduced at Osaka City University Hospital in January 2014; an interdisciplinary AST was established. We enrolled patients with anaerobic bacteremia between January 2009 and December 2018. Patients were classified into the pre-intervention group (from January 2009 to December 2013) and the post-intervention group (from January 2014 to December 2018). A significant decrease in definitive carbapenem use (P = 0.0242) and an increase in empiric tazobactam/piperacillin use (P = 0.0262) were observed in the post-intervention group. The de-escalation rate increased significantly from 9.38% to 32.7% (P = 0.0316) in the post-intervention group. The susceptibility of Bacteroides species and 30-day mortality did not worsen in the post-intervention group. These results showed that interventions by an AST can reduce carbapenem use and increase the de-escalation rate without worsening patient outcomes.

Epidemiology and microbiological features of anaerobic bacteremia in two French University hospitals

Bacteremia implicating anaerobic bacteria (BIAB) represents 2-6% of all episodes of bacteremia and is associated with high mortality. In this retrospective study from June 2015 to December 2016, we compared BIAB frequency in two hospital centers in Montpellier (France): Montpellier university hospital (MUH) and a center specialized in cancer (ICM). Among the 2465 microbiologically relevant episodes of bacteremia, we identified 144 (5.8%) in which anaerobic bacteria were implicated. BIAB frequency was higher at ICM than MUH (10.4%, vs. 4.9%, p < 0.01). Poly-microbial bacteremia was more frequent among the BIAB episodes (31.9% vs. 11.0% for aerobic-only bacteremia, p < 0.01). Bacteroides and Clostridium were the most frequently identified genera of anaerobic bacteria (64 and 18 episodes, respectively), with the B. fragilis group (BFG) involved in 68/144 episodes. We could perform antibiotic susceptibility typing in 106 of the 144 anaerobic isolates, including 67 BFG isolates. All isolates but one were susceptible to metronidazole. In the BFG, sporadic resistant or intermediate results were found for amoxicillin-clavulanate (5/67), piperacillin-tazobactam (2/67) and imipenem (1/67). BFG isolates were susceptible also to cefoxitin (90.8%), rifampicin (97.0%) and tigecyclin (91.0%). Multidrug resistance in this group (7 isolates) was mostly due to acquired resistance to moxifloxacin, clindamycin and tigecyclin. This study shows that BIAB frequency can vary among hospitals and services. They should especially be taken into account in centers specialized in cancer treatment. However, the implicated bacteria remain frequently susceptible to the most used antibiotics used against anaerobic bacteria, although resistance does exist.

Clinical relevance of Clostridium bacteremia: An 8-year retrospective study

Clostridium spp. are recovered from 25% of the blood culture positive with anaerobes. However, the clinical relevance of Clostridium bacteremia has been controverted in the literature, particularly for C. perfringens. We aimed to evaluate the clinical relevance of Clostridium bacteremia, either due to C. perfringens or other Clostridium species, and to identify the risk factors of mortality in these patients. A retrospective cohort study was conducted from January 2010 to April 2018. All the patients with at least one blood culture positive with any Clostridium species were included. Eighty-one patients with a least one blood culture positive with any Clostridium species were included. Seventy patients (86.4%) fulfilled the criteria for clinically relevant bacteremia. Bacteremia due to C. perfringens tended to be less clinically relevant than other Clostridium species but this was not statistically significant (76% vs 91.2%, P = 0.09). In case of clinically relevant bacteremia, the 30-day mortality rate was 31.4%. In multivariate analysis, adequate empiric antimicrobial therapy was significantly associated with survival (P = 0.03). In conclusion, bacteremia due to C. perfringens or other Clostridium species is usually clinically relevant. This finding was also supported by an improved survival at 30 days when adequate empiric antimicrobial therapy was administered.

Antimicrobial Stewardship Opportunities in Patients with Bacteremia Not Identified by BioFire FilmArray

A subset of bacteremia cases are caused by organisms not detected by a rapid-diagnostics platform, BioFire blood culture identification (BCID), with unknown clinical characteristics and outcomes. Patients with ≥1 positive blood culture over a 15-month period were grouped by negative (NB-PC) versus positive (PB-PC) BioFire BCID results and compared with respect to demographics, infection characteristics, antibiotic therapy, and outcomes (length of hospital stay [LOS] and in-hospital mortality). Six percent of 1,044 positive blood cultures were NB-PC. The overall mean age was 65 ± 22 years, 54% of the patients were male, and most were admitted from home; fewer NB-PC had diabetes (19% versus 31%, P = 0.0469), although the intensive care unit admission data were similar. Anaerobes were identified in 57% of the bacteremia cases from the NB-PC group by conventional methods: Bacteroides spp. (30%), Clostridium (11%), and Fusobacterium spp. (8%). Final identification of the NB-PC pathogen was delayed by 2 days (P < 0.01) versus the PB-PC group. The sources of bacteremia were more frequently unknown for the NB-PC group (32% versus 11%, P < 0.01) and of pelvic origin (5% versus 0.1%, P < 0.01) compared to urine (31% versus 9%, P < 0.01) for the PB-PC patients. Fewer NB-PC patients received effective treatment before (68% versus 84%, P = 0.017) and after BCID results (82% versus 96%, P = 0.0048). The median LOS was similar (7 days), but more NB-PC patients died from infection (26% versus 8%, P < 0.01). Our findings affirm the need for the inclusion of anaerobes in BioFire BCID or other rapid diagnostic platforms to facilitate the prompt initiation of effective therapy for bacteremia.

[Anaerobiospirillum succiniciproducens and Desulfovibrio desulfuricans in 2 cases of insidious bacteremia]

Two cases of insidious bacteremia by uncommon curve and spiral-shaped, motile anaerobic gram-negative rods are presented. Both of them were of an unclear origin and occurred in immunosuppressed patients with simultaneous diseases. The key tests for the identification of Anaerobiospirillum were its micromorphology, a strictly anaerobic condition, negative catalase activity, the special-potency disk profile, glucose fermentation, and β-NAG production. Desulfovibrio species was identified by all the above preliminary tests but with a different disk profile, as well as for being asaccharolytic and desulfoviridin and H₂S producer. We here alert about the resistance or intermediate susceptibility of Anaerobiospirillum succiniciproducens against antimicrobial agents, such as metronidazole, one of the first-line drugs used for the treatment of anaerobic gram-negative infections. Aminopenicillins with β-lactamase-inhibitor combinations and imipenem were active for this agent. Desulfovibrio desulfuricans was β-lactamase producer and resistant to cephalosporins, while metronidazole, imipenem and levofloxacin were active. A reliable identification of these microorganisms is important for establishing the best therapeutic scheme.