Bloodstream infections in older population: epidemiology, outcome, and impact of multidrug resistance

Epidemiology and Resistance Profiles of Bacteria Isolated From Blood Samples in Septic Patients at Emergency Department Admission: A 6-Year Single Centre Retrospective Analysis From Northern Italy

OBJECTIVE

This study aimed to investigate the microbiological and clinical heterogeneity of community-onset bloodstream infections (BSIs) and identify features to support targeted empirical antibiotic therapy in the Emergency Department (ED).

METHODS

Clinical and microbiological data from 992 BSI cases (1,135 isolates) diagnosed within 24 h of ED admission at IRCCS Humanitas Research Hospital, Milan, Italy (January 2015-June 2022), were analysed. Drug resistance was interpreted using EUCAST-2023. Clinical features included age, sex, comorbidities (e.g., cancer, diabetes), infection source, presence of central venous catheters (CVC), ongoing therapies, and sepsis severity. Microbiological data included pathogen identification and antimicrobial susceptibility.

RESULTS

Antibiotic-susceptible Escherichia coli (29.5%) was the most common isolate, including extended-spectrum beta-lactamase (ESBL)-producing strains (11.3%), followed by methicillin-susceptible Staphylococcus aureus (MSSA, 8.4%). BSIs due to E. coli were more frequent in patients >60 years (43.9% vs. 27.3%, P < 0.001) and associated with ESBL production (OR = 2.202, P = 0.031) and urosepsis (OR = 1.688, P = 0.006). Younger patients (≤60 years) had more S. aureus-associated BSIs (22.4% vs. 10.8%, P < 0.001) and methicillin resistance (7.9% vs. 3.6%, P = 0.021). Carbapenem-resistant Enterobacterales were rare (2.1%-2.8%), predominantly involving Klebsiella pneumoniae. Onco-hematological patients had a lower multidrug-resistance prevalence (9.5% vs. 21.1%, P < 0.001).

CONCLUSIONS

Community-onset BSIs demonstrated substantial prevalence of resistant pathogens, including ESBL and MRSA, emphasizing the need for robust surveillance systems. Age is a critical factor in guiding empirical antibiotic therapy in the ED.

An Analysis of Bacterial Infection Distribution in the Elderly, and Their Clinical and Laboratory Profiles: Aging and Bacterial Infection

Objective

The increasing proportion of the elderly population necessitates the development of strategies for managing infections encountered by this group. We aimed to examine the distribution of bacterial infections, their clinical presentations, treatments used, and in-hospital mortality rates among elderly patients.

Materials and Methods

We examined a cohort aged 65-79 (Group 1) and aged 80 and above (Group 2) with bacterial infections. Demographic characteristics, underlying conditions, clinical/laboratory findings, and mortality rates of the cases were compared.

Results

The study included 177 patients, of which 44.6% were female, and the mean age was 76.0 ± 8.8 years. Group 2 included 36.7% of the study population with a higher incidence of sepsis and urinary system infections (p=0.038 and p=0.037, respectively). On the other hand, skin and soft tissue infections (42%) emerged as the predominant cause of hospital admissions in Group 1 (p<0.001). Fatigue and dysuria were more frequent in Group 2 (p=0.008 and p=0.044, respectively), and erythema was more common in Group 1 (p=0.012). Hypertension (58.2%) was the most frequently observed comorbidity. Neurological diseases/dementia were more common in Group 2 than in Group 1 (p=0.036). Also, a delayed procalcitonin response to antibiotics was noted in Group 2 (p=0.006). Beta-lactam/beta-lactamase inhibitors were the most frequently used antibiotics, and cephalosporin antibiotics were preferred to a greater extent in Group 2 (p=0.02).

Conclusion

The increased rates of urinary tract infections and sepsis in individuals over 80 underscores the need for vigilant clinical oversight. Effectively managing underlying conditions can reduce the incidence of some infections in vulnerable groups.

Enhancing pathogens detection in suspected geriatric bloodstream infections using Nanopore-targeted sequencing

Bloodstream infections (BSIs) are a critical concern for elderly patients, where prompt and accurate diagnosis is vital for effective treatment. Traditional blood culture methods suffer from delayed results and susceptibility to false-negatives. Nanopore-targeted sequencing (NTS) offers rapid pathogen detection and reporting, presenting a promising alternative. However, the application of NTS for diagnosing suspected BSIs in geriatric patients remains insufficiently studied. We conducted a retrospective cohort study from January 2022 to January 2024, including 198 geriatric patients suspected of BSIs. We utilized NTS to detect pathogen characteristics and compared the effectiveness and consistency of NTS with simultaneous blood culture testing for pathogen detection. NTS demonstrated a pathogen detection rate of 61.1%. The most common bacterial pathogens were Escherichia coli and Staphylococcus aureus (each 7.7%), while Candida albicans was the most prevalent fungal pathogen (30%). Mixed-bacterial infections were detected in 21.7% of NTS-positive cases, and concurrent bacterial-fungal infections were observed in 9.92% of these cases. NTS-positive patients had higher rates of comorbidities, elevated inflammatory markers, and worse prognoses compared to NTS-negative patients. NTS exhibited a significantly higher pathogen detection rate and faster turnaround time than blood culture (78.1% vs 42.2%, P < 0.001), with an agreement rate of 65.6%. The elderly BSI patients frequently involve multiple or mixed infections and correlate with poorer prognoses. NTS provides a faster and more sensitive diagnostic alternative to traditional blood culture, potentially improving clinical outcomes and guiding more effective treatment strategies. This study highlights the need for further research to validate the routine clinical integration of NTS for managing BSIs in geriatric populations.

IMPORTANCE

Bloodstream infections (BSIs) in elderly patients pose substantial diagnostic and therapeutic challenges due to the limitations of traditional blood culture methods, which are hampered by slow turnaround times and false-negatives. Nanopore-targeted sequencing (NTS) emerges as a significant advancement, offering rapid and accurate pathogen detection directly from blood samples. This study demonstrates that NTS provides a higher detection rate and faster results than conventional blood cultures, crucial for the timely management of BSIs in geriatric patients, who often present with multiple or mixed infections and have poorer clinical outcomes. The findings underscore the potential of NTS to enhance diagnostic accuracy and speed, informing more effective treatment strategies and improving overall patient outcomes. Further research is essential to establish NTS as a routine diagnostic tool in the clinical management of BSIs in the elderly.

Evaluation of a nucleic acid amplification system, GENECUBE, for rapid detection of staphylococcal nuc and mecA in blood culture samples

OBJECTIVE

This study determined whether the GENECUBE rapid nucleic acid amplification test could directly detect nuc and mecA genes in clinical blood culture samples of Staphylococcus and various other pathogens.

METHODS

Between September 2020 and December 2021, 537 blood culture samples from 192 patients with suspected bacteremia were tested using conventional assays (MicroScan WalkAway96 or VITEK 2 systems) and GENECUBE nuc and mecA assays. Isolates from samples with discrepant results between the conventional and GENECUBE assays were further evaluated using MALDI-TOF mass spectrometry, disk diffusion testing using cefoxitin, broth microdilution testing using oxacillin, and sequencing for mecA. Bacterial solutions containing a mixture of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) were prepared to evaluate the limit of detection (LOD) of mecA.

RESULTS

Using conventional assays as the reference, the sensitivity, specificity, and positive and negative predictive values (95 % confidence interval) of GENECUBE were 100 % (96.8-100 %), 100 % (99.1-100 %), 100 % (96.8-100 %), and 100 % (99.1-100 %), respectively, for nuc detection and 100 % (96.1-100 %), 98.9 % (97.4-99.6 %), 94.9 % (88.5-98.3 %), and 100 % (99.2-100 %), respectively, for mecA detection. Sequencing analysis of five samples identified as methicillin-sensitive staphylococci using conventional assays and methicillin-resistant staphylococci using GENECUBE revealed the presence of methicillin-resistant isolates in all samples. The estimated LOD of mecA was 104 colony-forming units (CFU)/mL of MRSE with GENECUBE, compared with 105 CFU/mL with conventional assays.

CONCLUSION

The GENECUBE assay accurately detected mecA in positive blood culture samples and had higher sensitivity than conventional assays.

Increase of multidrug-resistant bacteria after the COVID-19 pandemic in a major teaching Hospital in Sicily (2018-2021)

INTRODUCTION

The COVID-19 pandemic has further highlighted the continuing threat of antimicrobial resistance (AMR) to global health and economic development. In the last two decades, AMR has raised increasing concern, with an estimated 4.95 million deaths globally due to bacterial AMR in 2019 alone. The aim of this study was to analyse the impact of the pandemic on the spread of multidrug-resistant organisms (MDROs) using data from the Hospital "P. Giaccone" in Palermo, comparing pre-pandemic and pandemic periods.

METHODS

This observational study involved adult patients who were discharged from the hospital between 01 January 2018 and 31 December 2021. Hospital Discharge Cards were linked with microbiological laboratory reports to assess MDRO isolations. SARS-CoV-2 positivity during hospitalisation was evaluated using the National Institute of Health surveillance system.

RESULTS

A total of 58 427 hospitalisations were evaluated in this study. Half the patients were aged over 65 years (N=26 984) and most admissions were in the medical area (N=31 716). During the hospitalisation period, there were 2681 patients (5%) with MDROs isolations, and 946 patients (2%) were positive for SARS-CoV-2. Multivariable analyses showed that during 2020 and 2021, there was a significantly increased risk of isolation of Staphylococcus aureus, Acinetobacter baumannii, and Klebsiella pneumoniae. Age, weight of the Diagnosis-Related Group (DRG), wards with higher intensity of care, and length-of-stay were associated with a higher risk of MDRO isolation.

CONCLUSION

This study provides new insights into the impact of the COVID-19 pandemic on MDRO isolation and has important implications for infection control and prevention efforts in healthcare facilities. Age, DRG-weight, and longer hospital stays further increased the risk of MDRO isolation. Thus, it is imperative to improve and follow hospital protocols to prevent healthcare-associated infections.

Real-life impact of respiratory panel PCR assay on antibiotic prescription in geriatric acute care in the pre-COVID-19 era

OBJECTIVES

In this era of bacterial resistance, avoiding inappropriate use of antibiotic treatments is of major importance. Respiratory tract infections are frequent among older patients, and differentiating viral from bacterial infections is a challenge. The aim of our study was to evaluate the impact of recently available respiratory PCR testing on antimicrobial prescription in geriatric acute care.

METHODS

We performed a retrospective study, including all hospitalized geriatric patients who had had multiplex respiratory PCR testing prescribed from 1st October 2018 to 30th September 2019. The PCR test comprised a respiratory viral panel (RVP) and a respiratory bacterial panel (RBP). PCR testing could be prescribed at any time during hospitalization by geriatricians. Our primary endpoint was antibiotic prescription after viral multiplex PCR testing results.

RESULTS

All in all, 193 patients were included, 88 (45.6%) of whom had positive RVP, while none had positive RBP. Patients with positive RVP had significantly fewer antibiotic prescriptions following test results than patients with negative RVP (odds ratio (OR) 0.41, 95% confidence interval (CI) 0.22-0.77; p = 0.004). Among positive-RVP patients, factors associated with antibiotic continuation were presence of radiological infiltrate (OR 12.02, 95%CI 3.07-30.29), and detected Respiratory Syncytial Virus (OR 7.54, 95%CI 1.74-32.65). That said, discontinuation of antibiotic treatment seems safe.

CONCLUSION

In this population, the impact of viral detection by respiratory multiplex PCR on antibiotic therapy was low. It could be optimized by means of clearly formulated local guidelines, qualified staff and specific training by infectious disease specialists. Cost-effectiveness studies are necessary.

Escalation of antimicrobial resistance among MRSA part 1: focus on global spread

INTRODUCTION

Staphylococcus aureus produce numerous virulence factors that influence tissue invasion, cytotoxicity, membrane damage, and intracellular persistence allowing them to be very common human pathogens. S. aureus isolates exhibit considerable diversity though specific genotypes have been associated with antimicrobial resistance (AMR) and toxin gene profiles. MRSA is an important pathogen causing both community-acquired (CA) and healthcare-acquired (HCA) infections. Importantly, over the past several decades, both HCA-MRSA and CA-MRSA have spread all over the globe. Even more concerning is that CA-MRSA clones have disseminated into hospitals and HCA-MRSA have entered the community. Factors that enhance spread of MRSA include: poor antimicrobial stewardship and inadequate infection control. The emergence and spread of multidrug resistant (MDR) MRSA has limited therapeutic options.

AREAS COVERED

The authors discuss the escalation of MRSA, both HCA-MRSA and CA-MRSA across the globe. A literature search of MRSA was performed via PubMed (up to September 2022), using the key words: antimicrobial resistance; β-lactams; community-associated MRSA; epidemiology; infection; multidrug resistance; Staphylococcus aureus.

EXPERT OPINION

Over the past several decades, MRSA has spread all over the globe. We encourage the judicious use of antimicrobials in accordance with antimicrobial stewardship programs along with infection control measures to minimize the spread of MRSA.