Bloodstream infections in a secondary and tertiary care hospital setting

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.

Impact of age in critically Ill infected patients: a post-hoc analysis of the INFAUCI study

PURPOSE

Older patients are the fastest expanding subgroup of intensive care units (ICU) and are particularly susceptible to bacterial infections and sepsis. The aim of this study was to address the epidemiology and the main determinants of outcome of infection in old and very old patients admitted to ICU.

METHODS

We performed a post hoc analysis of all infected patients admitted to ICU enrolled in a 1-year prospective, observational, multipurpose study. Patients aged < 65, 65-74 and ≥ 75 years were compared.

RESULTS

Of the 1652 patients included, 50% were older than 65 years. There were no significant differences between young, old and very old patients in either ICU, hospital length of stay, or nosocomial infection. All-cause mortality was significantly higher in participants aged ≥ 75. Increased Gram-negative microorganisms' isolates occurred in > 65 years (25% versus 31%; p = 0.034). Multidrug-resistant (MDR) microorganisms were directly associated to inappropriate empiric antibiotic therapy (OR 4.73; 95% CI 2.99-7.47) and inversely associated with community-acquired infection (OR 0.39; 95% CI 0.19-0.83). Age (65-74 years: OR 1.10; 95% CI 0.64-1.90 and ≥ 75 years: OR 1.52; 95% CI 0.89-2.59) and sepsis severity (sepsis: OR 0.67; 95% CI 0.18-2.46; severe sepsis: OR 1.17; 95% CI 0.40-3.44; septic shock: OR 0.77; 95% CI 0.27-2.24) were not associated to MDR bacteria.

CONCLUSION

Patients > 65 years accounted for 50% of infected patients admitted to an ICU. ICU and hospital length of stay, and nosocomial infection did not increase with age. Age did predispose to increased risk for infection by Gram-negatives. These findings may optimize strategies for infection management in older patients.

Bactericidal activity of a substituted thiazole against multidrug-resistant Eggerthia catenaformis isolated from patients with dental abscess

Human infections caused by the anaerobic bacterium Eggerthia catenaformis are rare. However, a growing number of case reports have presented the bacterium as the causative agent in many serious complications. This study provides data on the isolation and antibiotic susceptibility profiles of E. catenaformis from dental abscess. Identification of isolates was performed using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). We also investigated the antibacterial activity of 5-acetyl-4-methyl-2-(3-pyridyl) thiazole (AMPT) on E. catenaformis isolates. Minimum inhibitory concentrations (MICs) were determined by an agar dilution method and bactericidal activity was evaluated by a time-kill assay. Moreover, the mechanism of action of AMPT was also explored by cell membrane disruption assay and scanning electron microscopy (SEM). MALDI-TOF MS results revealed unambiguous identification of all isolates with score values between 2.120 and 2.501. Isolates NY4 and NY9 (20% of isolates) were found resistant to multiple antibiotics judged by MIC values. As multidrug-resistant strains of E. catenaformis were not reported to date, we then confirmed the identity of NY4 and NY9 based on 16S rRNA gene sequence. Favorably, all isolates were susceptible to AMPT with an MIC range of 0.25-1 mg/L. Time-kill kinetics of AMPT indicated that it exhibited potent bactericidal activity against the multidrug-resistant isolates NY4 and NY9. Furthermore, this study also hypothesizes that AMPT exerts its antibacterial effect through damaging the cell membrane and thereby induce the release of intracellular components. AMPT could therefore be considered as a therapeutic option for infections caused by multidrug-resistant bacteria.

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.

Utility of anaerobic bottles for the diagnosis of bloodstream infections

BACKGROUND

Obligate anaerobes usually account for less than 10% of bacteria recovered from blood cultures (BC). The relevance of routine use of the anaerobic bottle is under debate. The aim of this study was to evaluate the utility of anaerobic bottles for the diagnosis of bloodstream infections (BSI).

METHODS

We conducted a 6-month, retrospective, monocentric study in a tertiary hospital. All positive BC were grouped into a single episode of bacteremia when drawn within 7 consecutive days. Bacteremia were classified into contaminants and BSI. Charts of patients with BSI due to obligate anaerobes were studied.

RESULTS

A total of 19,739 blood cultures were collected, 2341 of which (11.9%) were positive. Anaerobic bottles were positive in 1528 (65.3%) of all positive BC but were positive alone (aerobic bottles negative) in 369 (15.8%). Overall 1081 episodes of bacteremia were identified, of which 209 (19.3%) had positive anaerobic bottles alone. The majority 126/209 (60.3%) were contaminants and 83 (39.7%) were BSI. BSI due to facultative anaerobes, obligate aerobes and obligate anaerobes were identified in 67 (80.7%), 3 (3.6%) and 13 (15.7%) of these 83 episodes, respectively. BSI due to obligate anaerobic bacteria were reported in 9 patients with gastro-intestinal disease, in 3 with febrile neutropenia and in 1 burned patient.

CONCLUSIONS

Anaerobic bottles contributed to the diagnosis of a significant number of episodes of bacteremia. Isolated bacteria were mostly contaminants and non-obligate anaerobic pathogens. Rare BSI due to obligate anaerobes were reported mainly in patients with gastro-intestinal disorders and during febrile neutropenia.

Inpatient healthcare-associated bloodstream infections in older people

This retrospective study describes inpatient healthcare-associated bloodstream infections (HABSI) in older adults and explores whether urinary catheters (presence/insertion/removal) were related to HABSI events. One hundred and sixty-seven HABSI events were identified, predominantly (124, 74%) with Gram-negative bacteria. HABSI was attributed to a urinary source in 110 patients (66%), with over half (63, 57%) of these associated with urinary catheters. Catheter-associated HABSI may be avoidable and potential preventative strategies are discussed.

Prevalence of ESBL-Producing Enterobacteriaceae in Pediatric Bloodstream Infections: A Systematic Review and Meta-Analysis

Background

Pediatric bloodstream infections (BSIs) with Extended-Spectrum Beta-Lactamase- producing Enterobacteriaceae (ESBL-PE) are associated with worse clinical outcomes. We aimed to estimate the prevalence of and the mortality associated with ESBL-PE in this patient population.

Methods

A systematic review and meta-analysis using PubMed and EMBASE and included studies reporting the prevalence of ESBL-PE among confirmed BSIs in patients <19 years old.

Results

Twenty three (out of 1,718 non-duplicate reports) studies that provided data on 3,381 pediatric BSIs from 1996 to 2013 were included. The prevalence of ESBL-PE was 9% [95%CI (6, 13)] with an annual increase of 3.2% (P = 0.04). The prevalence was 11% [95%CI (6, 17)] among neonates, compared to 5% [95%CI (0, 14)] among children older than 28 days. The pooled prevalence was 15% in Africa [95%CI (8, 23)], 12% in South America [95%CI (5, 23)], 11% in India [95%CI (7, 17)], 7% in the rest of Asia [95%CI (0, 22)], 4% in Europe [95%CI (1, 7)] and 0% in Oceania [95%CI (0, 3)]. Importantly, the mortality in neonates with BSI due to ESBL-PE was 36% [95%CI (22, 51)], compared to 18% [95%CI (15, 22)] among all other neonates with BSI and this difference was statistically significant (P = 0.01).

Conclusions

In the pediatric population, the prevalence of BSI due to ESBL-PE is significant and is associated with increased mortality in neonates. Further studies are warranted to establish a high-risk group and the evaluation of preventive measures, such as antibiotic stewardship programs and infection control measures, in this population is urgently needed.

Timing of positive blood samples does not differentiate pathogens causing healthcare-associated from community-acquired bloodstream infections in children in England: a linked retrospective cohort study

Paediatricians recognize that using the time-dependent community-acquired vs. hospital-acquired bloodstream infection (BSI) dichotomy to guide empirical treatment no longer distinguishes between causative pathogens due to the emergence of healthcare-associated BSIs. However, paediatric epidemiological evidence of the aetiology of BSIs in relation to hospital admission in England is lacking. For 12 common BSI-causing pathogens in England, timing of laboratory reports of positive paediatric (3 months to 5 years) bacterial blood isolates were linked to in-patient hospital data and plotted in relation to hospital admission. The majority (88·6%) of linked pathogens were isolated <2 days after hospital admission, including pathogens widely regarded as hospital acquired: Enterococcus spp. (67·2%) and Klebsiella spp. (88·9%). Neisseria meningitidis, Streptococcus pneumoniae, group A streptococcus and Salmonella spp. were unlikely to cause hospital-acquired BSI. Pathogens commonly associated with hospital-acquired BSI are being isolated <2 days after hospital admission alongside pathogens commonly associated with community-acquired BSI. We confirm that timing of blood samples alone does not differentiate between bacterial pathogens. Additional factors including clinical patient characteristics and healthcare contact should be considered to help predict the causative pathogen and guide empirical antibiotic therapy.

Predictors of early mortality in very elderly patients with bacteremia: a prospective multicenter cohort

OBJECTIVES

The proportion of very elderly people in the population is increasing, and infectious diseases in this patient group may present with specific characteristics. The objective of this study was to investigate the outcome predictors of bacteremia among the very elderly.

METHODS

This was a multicenter prospective cohort study of bloodstream infections (BSI) in patients ≥ 80 years old in 15 hospitals in Spain. The outcome variables were 14-day and 30-day mortality. Multivariate analysis was performed.

RESULTS

One hundred and twenty episodes were included. Mortality was 22% (n = 26) on day 14 and 28% (n = 34) on day 30. In the univariate analysis, the variables associated with mortality were neutropenia, recent surgery, Pitt score ≥ 2, intensive care unit (ICU) admission, severe sepsis or shock, and abdominal, unknown, and respiratory tract sources. In the multivariate analysis, variables associated with mortality on day 14 were high-risk source (abdominal, unknown, and respiratory tract sources; odds ratio (OR) 7.9, 95% confidence interval (CI) 1.8-33.9), Pitt score ≥ 2 (OR 5.6, 95% CI 1.3-23.3), inadequate empirical treatment (OR 11.24, 95% CI 1.6-80.2), and severe sepsis or shock at presentation (OR 5.3, 95% CI 1.4-20.7); the interaction between empiric treatment and high-risk source was significant. On day 30, mortality was independently related to a high-risk source (OR 2.92, 95% CI 1.1-7.5) and presentation with severe sepsis or shock (OR 3.81, 95% CI 1.2-12.4).

CONCLUSIONS

Presentation with severe sepsis or shock and a high-risk source of BSI were independent predictors of 14-day and 30-day mortality. Inadequate empirical treatment was also a predictor of early mortality in patients with a high-risk source.

Community-acquired, healthcare-associated and hospital-acquired bloodstream infection definitions in children: a systematic review demonstrating inconsistent criteria

BACKGROUND

Historically, bacterial infections were categorized as either community-acquired (CA) or hospital-acquired (HA). However, the CA/HA dichotomy no longer adequately reflects patterns of emerging healthcare-associated (HCA) infections in complex patients managed between hospital and the community. Studies trying to define this evolving epidemiology often excluded children.

AIM

To identify what criteria have been used to distinguish between CA, HCA and HA bloodstream infections (BSIs) in children, and the proportional distribution of CA, HCA and HA among total BSIs and by organism.

METHODS

We systematically reviewed published literature from PubMed, UK Department of Health and US Centers for Disease Control and Prevention websites.

FINDINGS

Results from 23 studies and the websites highlighted the use of inconsistent criteria. There were 13 and 15 criteria variations for CA and HA BSI respectively, although a 48h cut-off for cultures sampled post admission was most commonly reported. Five studies used variable clinical criteria to define HCA. The mean proportion of paediatric CA BSI in nine studies was 50%. Only four BSI organisms from five studies were predominantly CA (Streptococcus pneumoniae, Salmonella spp.) or HA (coagulase-negative staphylococci, Enterococcus spp.), whereas Pseudomonas spp., Klebsiella spp. and Enterobacter spp. did not clearly fit into either category.

CONCLUSIONS

Our study reveals inconsistent use of criteria, and a lack of evidence upon which to base them, to distinguish between CA, HCA and HA BSI in children. Criteria for CA, HCA and HA BSI need to be developed using population-based studies that consider patients' clinical characteristics, recent healthcare exposure as well as isolated organism species.

Reappraisal of the outcome of healthcare-associated and community-acquired bacteramia: a prospective cohort study

Background

Healthcare-associated (HCA) bloodstream infections (BSI) have been associated with worse outcomes, in terms of higher frequencies of antibiotic-resistant microorganisms and inappropriate therapy than strict community-acquired (CA) BSI. Recent changes in the epidemiology of community (CO)-BSI and treatment protocols may have modified this association. The objective of this study was to analyse the etiology, therapy and outcomes for CA and HCA BSI in our area.

Methods

A prospective multicentre cohort including all CO-BSI episodes in adult patients was performed over a 3-month period in 2006–2007. Outcome variables were mortality and inappropriate empirical therapy. Adjusted analyses were performed by logistic regression.

Results

341 episodes of CO-BSI were included in the study. Acquisition was HCA in 56% (192 episodes) of them. Inappropriate empirical therapy was administered in 16.7% (57 episodes). All-cause mortality was 16.4% (56 patients) at day 14 and 20% (71 patients) at day 30. After controlling for age, Charlson index, source, etiology, presentation with severe sepsis or shock and inappropriate empirical treatment, acquisition type was not associated with an increase in 14-day or 30-day mortality. Only an stratified analysis of 14th-day mortality for Gram negatives BSI showed a statically significant difference (7% in CA vs 17% in HCA, p = 0,05). Factors independently related to inadequate empirical treatment in the community were: catheter source, cancer, and previous antimicrobial use; no association with HCA acquisition was found.

Conclusion

HCA acquisition in our cohort was not a predictor for either inappropriate empirical treatment or increased mortality. These results might reflect recent changes in therapeutic protocols and epidemiological changes in community pathogens. Further studies should focus on recognising CA BSI due to resistant organisms facilitating an early and adequate treatment in patients with CA resistant BSI.

Five-year retrospective epidemiological survey of anaerobic bacteraemia in a university hospital and rewiew of the literature

In spite of the developments in microbiological methods, blood cultures remain the cornerstone for the diagnosis of bacteraemia. Classically, minimum of two bottles are collected on a routine basis: an aerobic bottle, allowing preferential growth of aerobic and facultative anaerobic microorganisms, and an anaerobic bottle, providing suitable environment for strict anaerobic bacteria. Recent reports have documented a decrease in anaerobic bacteraemias and have questioned the need for routine anaerobic blood cultures. Bacteraemia due to anaerobic organisms occurs in 0.5-12% of blood cultures worldwide; however, recent studies from Europe and the USA presented inconsistent data regarding the prevalence of anaerobic bacteraemias between 1993 and 2006. The aims of this retrospective survey were to determine the prevalence of bacteraemias due to anaerobic bacteria and evaluate the importance of anaerobic blood cultures in a university hospital in Szeged, Hungary. We examined the occurrence of bacteraemias due to anaerobic bacteria during a 5-year period, from January 2005 to 2009, in order to identify current trends of anaerobic bacteraemias in our university.

Current management of bloodstream infections

Bloodstream infection (BSI) is a frequent complication of invasive infections. The presence of bacteremia has therapeutic and prognostic implications. Here we review recent changes in the epidemiology, diagnosis and treatment of BSI (excluding candidemia). The evidence of the impact of healthcare-association in many community-onset episodes and the increase in drug-resistant pathogens causing BSI in the community and hospitals is reviewed. The emergence of molecular methods as an alternative tool for the diagnosis of BSI and novel aspects of clinical management, particularly of some multidrug-resistant organisms. Several quality indicators related to the diagnosis and management of bacteremia in hospitals are proposed.

The role of anaerobic bacteria in bacteremia

Anaerobic bacteria remain an important cause of bloodstream infections and account for 1-17% of positive blood cultures. This review summarizes the epidemiology, microbiology, predisposing conditions, and treatment of anaerobic bacteremia (AB) in newborns, children, adults and in patients undergoing dental procedures. The majority of AB are due to Gram-negative bacilli, mostly Bacteroides fragilis group. The other species causing AB include Peptostreptococcus, Clostridium spp., and Fusobacterium spp. Many of these infections are polymicrobial. AB in newborns is associated with prolonged labor, premature rupture of membranes, maternal amnionitis, prematurity, fetal distress, and respiratory difficulty. The predisposing conditions in children include: chronic debilitating disorders such as malignant neoplasm, hematologic abnormalities, immunodeficiencies, chronic renal insufficiency, or decubitus ulcers and carried a poor prognosis. Predisposing factors to AB in adults include malignant neoplasms, hematologic disorders, transplantation of organs, recent gastrointestinal or obstetric gynecologic surgery, intestinal obstruction, diabetes mellitus, post-splenectomy, use of cytotoxic agents or corticosteroids, and an undrained abscess. Early recognition and appropriate treatment of these infections are of great clinical importance.

Clinical characteristics and outcomes of patients with vancomycin-susceptible Enterococcus faecalis and Enterococcus faecium bacteraemia--a five-year retrospective review

The purpose of this study was to assess the epidemiology and outcomes of enterococcal bacteraemia. A retrospective review of demographic, microbiological and clinical data in patients 16 years of age and over with Enterococcus faecalis or E. faecium bacteraemia at Auckland City Hospital, New Zealand, from June 2002 to May 2007 was carried out. A total of 212 patients fulfilled the inclusion criteria, with 205 being included in the analysis. E. faecalis accounted for 86% (176/205) and E. faecium 14% (29/205) of the patients. Amoxycillin resistance occurred in 69% (20/29) of E. faecium isolates. High-level gentamicin resistance was present in 38% (65/171) of E. faecalis isolates and 25% (7/28) of E. faecium isolates (P = NS). No vancomycin-resistant enterococci were isolated. Healthcare association was present in 73% (149/205) of patients. Co-morbidities were present in 86% (176/205) of patients. The 7-day mortality was 13% (27/205) and the 30-day mortality 25% (52/205). On multivariate analysis, the 7-day mortality was statistically significantly associated with cirrhosis and shorter intravenous amoxycillin therapy. The 30-day mortality was statistically significantly associated with cirrhosis, malignancy, E. faecium bacteraemia and not receiving active antimicrobial therapy. No statistically significant association between high-level gentamicin resistance and mortality was demonstrated on multivariate analysis. Enterococcal bacteraemia occurs in a co-morbid, healthcare-exposed population. Associated mortality is high, and is associated with severe underlying disease, E. faecium bacteraemia and treatment factors.