Gram-negative Bacteria Infection Research Articles

Restoring colistin sensitivity in colistin-resistant Salmonella and Escherichia coli: combinatorial use of berberine and EDTA with colistin.

Colistin is last-resort antibiotic used to treat serious clinical infections caused by MDR bacterial pathogens. The recent emergence of transferable plasmid-mediated COL resistance gene mcr-1 has raised the specter of a rapid worldwide spread of COL resistance. Coupled with the fact of barren antibiotic development pipeline nowadays, a critical approach is to revitalize existing antibiotics using antibiotic adjuvants. Our research showed that berberine combined with EDTA effectively reversed COL resistance both in vivo and in vitro through multiple modes of action. The discovery of berberine in combination with EDTA as a new and safe COL adjuvant provides a therapeutic regimen for combating Gram-negative bacteria infections. Our findings provide a potential therapeutic option using existing antibiotics in combination with antibiotic adjuvants and address the prevalent infections caused by MDR Gram-negative pathogens worldwide.

Lipopeptide adjuvants for antibiotics and vaccines: the future step in the fight against multidrug-resistant and extensively drug-resistant pathogens

With the surge of antibiotic resistance in bacteria, the need for a larger arsenal of effective antibiotics and vaccines has drastically increased in the past decades. Antibiotics like vaccines can benefit from significant potentiation when used in combination with adjuvants. Antibiotic adjuvants can allow for gram-positive bacteria (GPB) specific treatments to be used against gram-negative bacteria (GNB) infections, with minimal antimicrobial resistance (AMR). In the case of vaccines, they allow for modulation and increase of the immune response. Lipopeptides are molecules of choice because of their ability to activate specific cell surface receptors, penetrate the outer membrane of GNB, safety and ease of synthesis. This review explores the recent developments in lipopeptide adjuvants for antibiotics and vaccines, providing a roadmap on how to develop adjuvants to efficiently combat AMR. After a brief overview of bacterial resistance, lipopeptide adjuvants for antibiotics and vaccines are discussed, providing insights into stability, sources, and delivery methods. Findings discussed in this review could be applied to the development of safer, more effective adjuvants, that could expand the use or repurpose current antibiotics or improve vaccination results in future clinical trials.

Epidemiology and clinical significance of carbapenemases in Australia: a narrative review.

Carbapenemase-producing gram-negative bacteria (CP-GNB) infections threaten public health with high mortality, morbidity and treatment costs. Although frequencies remain low in Australia (total number of CP-GNB infections reported was 907 in 2022), blaIMP-4 has established low levels of endemicity in many states. Imipenemase metallo-β-lactamase types alone accounted for more than half of all carbapenemases in carbapenemase-producing Enterobacterales isolates in Australia, particularly in Enterobacter cloacae complex. New Delhi metallo-β-lactamase constitutes almost 25% of all carbapenemases in Australia and was identified predominantly in Escherichia coli. The OXA-48-like carbapenemases include almost 10% of all carbapenemases and are mainly seen in Klebsiella pneumoniae and E. coli. Although K. pneumoniae carbapenemase-type carbapenemases are rare in Australia, some local outbreaks have occurred. Most carbapenem-resistant (CR) Pseudomonas aeruginosa strains in Australia do not produce carbapenemases. Finally, OXA-23-like carbapenemases are overwhelmingly positive in CR-Acinetobacter baumannii strains in Australia. Treatment of CR-GNB infections challenges physicians. Of 10 new antibiotics active against at least some CR-GNB infections that are approved by the USFood and Drug Administration, just three are approved for use in Australia. In this context, there is still an unmet need for novel antibacterials that can be used for the treatmentof CR-GNB infections in Australia, as well as a pressing requirement for new mechanisms to 'de-link' antibiotic sales from their availability. In this narrative review, we aim to overview the epidemiology and clinical significance of carbapenem resistance in Australia as it pertains to Enterobacterales, P. aeruginosa and A. baumannii.

Environmental microbial colistin resistance in an elderly south Brazilian long-term care facility

ABSTRACT Colistin resistance is a global health concern, with antibiotics being the last treatment for Gram-negative bacteria infections. We aimed to identify colistin-resistant enterobacteria on environmental surfaces of a long-term care facility (LTCF) for the elderly in southern Brazil. Samples were collected and screened on MacConkey agar plus colistin, followed by API20E identification and PCR. Two isolates were founded and identified as Klebsiella pneumoniae and Providencia stuartii harboring mcr-1 gene with MICs > 128 µg mL−1 for colistin. This is the first isolation of microorganisms resistant to colistin in the environment of a LTCF for the elderly in south Brazil, urging monitoring programs to reduce environmental contamination by multiresistant microorganisms.

Analysis of factors influencing the risk of secondary infection in patients colonized or infected with multidrug-resistant Gram-negative bacteria following hospitalization

We seek to investigate the multifaceted factors influencing secondary infections in patients with multidrug-resistant Gram-negative bacteria (MDR-GNB) colonization or infection post-hospitalization. A total of 100 patients with MDR-GNB colonization or infection were retrospectively reviewed, encompassing those admitted to both the general ward and intensive care unit of our hospital from August 2021 to December 2022. Patients were categorized into the control group (non-nosocomial infection, n = 56) and the observation group (nosocomial infection, n = 44) based on the occurrence of nosocomial infection during hospitalization. Clinical data were compared between the two groups, including the distribution and antibiotic sensitivity of MDR-GNB before nosocomial infection. Significant differences were observed between the two groups in terms of age, underlying diseases, immune status, length of stay, and invasive medical procedures (P < 0.05). The observation group also had fewer patients practicing optimized hygiene, strict isolation, and antibiotic control than the control group (P < 0.05). Factors influencing the risk of secondary infection after hospitalization in patients colonized or infected with MDR-GNB included patient age, underlying diseases, immune status, length of hospitalization, medical invasive procedures, optimized hygiene, strict isolation, and antibiotic control (P < 0.05). The length of hospitalization and treatment cost in the observation group were higher than those in the control group (P < 0.05). This study comprehensively analyzes the intricate mechanisms of secondary infections in patients with MDR-GNB infections post-hospitalization. Key factors influencing infection risk include patient age, underlying diseases, immune status, length of hospitalization, medical invasive procedures, optimized hygiene, strict isolation, and antibiotic control.

GRAM-NEGATIVE BACTERIA IN SOME CLINICAL SPECIMENS AND THEIR ANTIBIOTICS RESISTANCE PROFILES, SANA’A, YEMEN

Gram-negative bacteria (GNB) have emerged globally as significant public health problems owing to their high resistance to antibiotics, particularly in developing countries such as Yemen. Therefore, this study aimed to determine the antibiotic resistance profile of GNB isolated from clinical samples in Sana’a City, Yemen. A total of 420 clinical samples, including vaginal swabs, urine, and pus, were collected from patients who attended some hospitals in Sana’a City, Yemen, in 2018. The collected specimens were examined according to standard microbiological methods, and the isolated bacteria were tested against some antibacterial agents using the Kirby-Bauer disc diffusion method on Mueller-Hinton agar. Among 420 specimens, the prevalence of gram-negative bacteria infections was 49.76%. A high rate of GNB was reported among the age group of 41–50 years old (57.97%), female patients (52.19%), those who came from rural areas (60.0%), and those who were uneducated (86.56%). The vaginal specimens exhibited a higher prevalence of bacterial bacteria (60.42%), followed by urine (51.28%) and pus (35.0%). Escherichia coli accounted for the greatest proportion of bacteria recovered from the study's patients (36.62%), followed by Klebsiella pneumoniae (18.66%), Enterobacter sp. (12.32%), Acinetobacter sp. (10.92%), Pseudomonas aeruginosa (9.15%), Citrobacter sp. (6.34%), and Proteus mirabilis (5.99%). E. coli was highly resistant to imipenem and enrofloxacin. Similarly, K. pneumoniae and P. aeruginosa were highly resistant to imipenem and norfloxacin. About 62.86% of Enterobacter sp. isolates were resistant to imipenem. In addition, 83.33–78.97% of Acinetobacter sp. isolates were resistant to imipenem and meropenem. Citrobacter sp. had high resistance to norfloxacin. Additionally, over 50% of P. mirabilis isolates were resistant to ofloxacin, norfloxacin, cefuroxime, and ceftizoxime. The conclusion is that there exists a significant proportion of GNB prevalence and antibacterial resistance among the study subjects. Therefore, multisectoral approach is needed for implementing effective strategies to reduce the transmission of antibiotic-resistant bacteria among the community.

Effect of photodynamic therapy with 5-aminolevulinic acid and EDTA-2Na against mixed infection of methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa.

The increasing abundance of drug-resistant bacteria is a global threat. Photodynamic therapy is an entirely new, non-invasive method for treating infections caused by antibiotic-resistant strains. We previously described the bactericidal effect of photodynamic therapy on infections caused by a single type of bacterium. We showed that gram-positive and gram-negative bacteria could be killed with 5-aminolevulic acid and 410 nm light, respectively. However, clinically, mixed infections are common and difficult to treat. We investigated the bactericidal effects of photodynamic therapy on mixed infections of methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. We compared bacterial growth with and without photodynamic therapy invitro. Then, invivo, we studied mixed infections in a mouse skin ulcer model. We evaluated the rates of ulcer area reduction and transitions to healing in treated and untreated mice. In addition, a comparison was made between PDT and existing topical drugs. We found that photodynamic therapy markedly reduced the growth of both methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa, in culture, and it reduced the skin ulcer areas in mice. PDT was also more effective than existing topical medicines. This study showed that photodynamic therapy had antibacterial effects against a mixed infection of gram-positive and gram-negative bacteria, and it promoted skin ulcer healing. These results suggested that photodynamic therapy could be effective in both single- and mixed-bacterial infections.

Comparative pharmacokinetics of polymyxin B in critically ill elderly patients with extensively drug-resistant gram-negative bacteria infections.

Introduction: Elderly patients are more prone to develop acute kidney injury during infections and polymyxin B (PMB)-associated nephrotoxicity than young patients. The differential response to PMB between the elderly and young critically ill patients is unknown. We aimed to assess PMB exposure in elderly patients compared with young critically ill patients, and to determine the covariates of PMB pharmacokinetics in critically ill patients. Methods: Seventeen elderly patients (age ≥ 65years) and six young critically ill patients (age < 65years) were enrolled. Six to eight blood samples were collected during the 12h intervals after at least six doses of intravenous PMB in each patient. PMB plasma concentrations were quantified by high-performance liquid chromatography-tandem mass spectrometry. The primary outcome was PMB exposure as assessed by the area under the concentration-time curve over 24h at steady state (AUCss, 0-24h). Results and Discussion: The elderly group had lower total body weight (TBW) and higher Charlson comorbidity scores than young group. Neither AUCss, 0-24h nor normalized AUCss, 0-24h (adjusting AUC for the daily dose in mg/kg of TBW) was significantly different between the elderly group and young group. The half-life time was longer in the elderly patients than in young patients (11.21 vs 6.56h respectively, p = 0.003). Age and TBW were the covariates of half-life time (r = 0.415, p = 0.049 and r = -0.489, p = 0.018, respectively). TBW was the covariate of clearance (r = 0.527, p = 0.010) and AUCss, 0-24h (r = -0.414, p = 0.049). Patients with AUCss, 0-24h ≥ 100mg·h/L had higher baseline serum creatinine levels and lower TBW than patients with AUCss, 0-24h < 50mg·h/L or patients with AUCss, 0-24h 50-100mg·h/L. The PMB exposures were comparable in elderly and young critically ill patients. High baseline serum creatinine levels and low TBW was associated with PMB overdose. Trial registration: ChiCTR2300073896 retrospectively registered on 25 July 2023.

Synergistic Activity and Mechanism of Sanguinarine with Polymyxin B against Gram-Negative Bacterial Infections.

Compounds that potentiate the activity of clinically available antibiotics provide a complementary solution, except for developing novel antibiotics for the rapid emergence of multidrug-resistant Gram-negative bacteria (GNB). We sought to identify compounds potentiating polymyxin B (PMB), a traditional drug that has been revived as the last line for treating life-threatening GNB infections, thus reducing its nephrotoxicity and heterogeneous resistance in clinical use. In this study, we found a natural product, sanguinarine (SA), which potentiated the efficacy of PMB against GNB infections. The synergistic effect of SA with PMB was evaluated using a checkerboard assay and time-kill curves in vivo and the murine peritonitis model induced by Escherichia coli in female CD-1 mice in vivo. SA assisted PMB in accelerating the reduction in bacterial loads both in vitro and in vivo, improving the inflammatory responses and survival rate of infected animals. The subsequent detection of the intracellular ATP levels, membrane potential, and membrane integrity indicated that SA enhanced the bacterial-membrane-breaking capacity of PMB. A metabolomic analysis showed that the inhibition of energy metabolism, interference with nucleic acid biosynthesis, and the blocking of L-Ara4N-related PMB resistance may also contribute to the synergistic effect. This study is the first to reveal the synergistic activity and mechanism of SA with PMB, which highlights further insights into anti-GNB drug development.

Nitric Oxide and Hypochlorite Assessment and Screening of some β-Lactamase Encoding Genes among Gram Negative Bacteria in Patients with Acute Leukemia

Objective: The serologic levels of both nitric oxide (NO) and hypochlorite (ClO-) were assessed in this study for Iraqi acute leukemic patients infected with Gram negative bacteria (GNB). Alongside, the phylogenetic analysis for both blaSHV and blaTEM genes of GNB was performed. Methods: The clinical samples were recovered from acute leukemic patients at hematology center in Baghdad from January 2021 to December 2021. The identification of bacterial isolates and susceptibility test were performed using Vitek 2 Compact System. Serum levels of NO and ClO- were assayed by Enzyme Linked Immunosorbent assay and colorimetric method, respectively. Gene screening was done utilizing polymerase chain reaction. DNA sequencing, GenBank accession numbers submission, and phylogenetic analysis were also conducted. Results: From 260 patients with acute leukemia, 485 clinical samples were collected from different sites. Of this total, 70 (15%) isolates of GNB were obtained, distributing as Klebsiella pneumoniae 23 (33%), Escherichia coli 21 (30%), Pseudomonas aeruginosa 18 (26%), and Acinetobacter baumannii 8 (11%). These isolates were mainly collected from urine 39 (55.71%), followed by blood 23 (32.85%), and the least from swabs 8 (11.42%). The infections of GNB were higher among acute myeloblastic leukemia (AML) patients 40 (57.14%) than these with acute lymphoblastic leukemia (ALL) 30 (42.85%). The levels of NO were higher among groups of patients than control groups. Additionally, ClO-levels were observed to be slightly increased in patients above these of controls. Most isolates of K. pneumoniae and E. coli showed high resistance rates for penicillins (ampicillin and ticarcillin), cephalosporins (ceftazidime, cefotaxime, ceftriaxone, and cefepime), followed by gentamicin and ciprofloxacin. Cefoxitin, aztreonam, imipenem and meropenem were nearly more effective against GNB isolates. On the other hand, about half isolates P. aeruginosa and all A. baumannii were resistant to the tested antibiotics. Extended Spectrum β- Lactamases (ESBLs) were released in 49 (70%) of the tested isolates of GNB. The multidrug resistant (MDR) pattern was noticed among 58 (82.85%) of GNB. Interestingly, ESBLs producing MDR isolates were determined in 34 (58.62%) of the studied GNB. Genotypic screening revealed that blaSHV and blaTEM genes were characterized in 20 (28.57%) and 32 (45.71%) of GNB isolates, respectively, while all GNB were negative for blaCTX-M. DNA sequencing of blaSHV amplicons revealed the occurrence of one point mutation (111T&gt;A) in six isolates of K. pneumoniae with a missense effect (p.31Q&gt;L) on the encoded protein. Forty-five GenBank accession numbers were recorded in NCBI to represent the studied variants of ESBLs. Phylogenetic analysis of both blaSHV and blaTEM displayed the possible epidemiologic routes of the tested GNB by detecting the origin host, source of collection, and geographic spread as compared with the reference sequences. Conclusion: high serum levels of both NO and ClO- indicated the potential role of these microbicidal agents to predict the serious infections of GNB in acute leukemia population. Phylogenetic analysis represented an important tool, possibly aiding in early control and prevention of pathogenic GNB.

Clinical outcomes of intensive care unit patients infected with multidrug-resistant gram-negative bacteria treated with ceftazidime/avibactam and ceftolozane/tazobactam.

In intensive care units (ICUs), infection rates range from 18 to 54%, which is five to ten times higher than those observed in other hospital units, with a mortality rate of 9% to 60%. In recent decades, the susceptibility pattern has changed and Gram-Negative Bacteria (GNB) have become a threat due to their high frequency of multidrug resistance associated with a scarcity of therapeutic options. However, the drugs Ceftolozane/Tazobactam (C/T) and Ceftazidime/Avibactam (C/A) are demonstrating good clinical and microbiological response in the treatment of severe nosocomial infections. Therefore, this study aims to evaluate the clinical outcome of patients with severe infections caused by Multidrug-Resistant (MDR) GNB treated with C/T and C/A. Our study evaluates a total of 131 patients who received treatment with C/T and C/A due to infections caused by MDR GNB within the period from 2018 to 2021. The main infections were urinary tract (46,6%) and respiratory (26,7%) infections. Pseudomonas aeruginosa was the prevailing agent in the sample evaluation (34.3%), followed by Klebsiella pneumoniae (30,1%). About 54,9% of patients showed a favorable response, with culture negativation in 66,4% of the samples, with no discrepancy in negativations when comparing ages: 67,7% in young and 66% in elderly patients. Among the patients, 62,6% received monotherapy with C/T and C/A with a better response observed with monotherapy compared to combination therapy (58,6% vs 41,4%). The overall mortality rate was 45%, with MDR GNB infections responsible for 33,9% of these deaths, and the others (66,1%) due to factors such as oncological, hematological, and degenerative neurological diseases. In regards to hematological aspect, 35,1% of patients showed changes, with 28,2% of them presenting anemia, 4,5% thrombocytopenia, and 2,5% thrombocytosis. Concerning the use of invasive devices, higher mortality was observed in patients on mechanical ventilation (52%). In this manner, it was possible to observe that therapy with C/T and C/A yielded a favorable clinical outcome in patients with severe infections caused by MDR GNB in the study. These drugs also demonstrated good tolerability regardless of age or the presence of preexisting comorbidities and were deemed safe when assessing adverse effects. Our data also demonstrate the importance of determining the mechanism of resistance to carbapenems so that these drugs can be used more effectively and rationally.

Combining with domiphen bromide restores colistin efficacy against colistin-resistant Gram-negative bacteria in vitro and in vivo

Today, colistin is considered a last-resort antibiotic for treating multidrug-resistant (MDR) Gram-negative bacteria (GNB). However, the increased and improper use of colistin has led to the emergence of colistin-resistant (Col-R) GNB. Thus, it is urgent to develop new drugs and therapies in response to the ongoing emergence of colistin resistance. In this study, we investigated the antibacterial and antibiofilm activities of the quaternary ammonium compound domiphen bromide (DB) in combination with colistin against clinical Col-R GNB both in vitro and in vivo. Checkerboard assay and time-kill analysis demonstrated significant synergistic antibacterial effects of the colistin/DB combination. The synergistic antibiofilm activity was confirmed through crystal violet staining and scanning electron microscopy (SEM). Furthermore, the colistin/DB combination exhibited increased survival rates in infected larvae and reduced bacterial loads in a mouse thigh infection model. The cytotoxicity measurement and hemolysis test showed that the combination did not adversely affect cell viability at synergistic concentrations. The alkaline phosphatase (ALP) leak test and propidium iodide (PI) staining analysis further revealed that the colistin/DB combination enhanced the therapeutic effect of colistin by altering bacterial membrane permeability. The ROS assays revealed that the combination induced the accumulation of bacterial ROS, leading to bacterial death. In conclusion, our study is the first to identify DB as a colistin potentiator, effectively restoring the sensitivity of bacteria to colistin. It provides a promising alternative approach for combating Col-R GNB infections.

Molecular characterization of blaNDM-harboring plasmids reveal its rapid adaptation and evolution in the Enterobacteriaceae

Carbapenem is one of the few available drugs to treat multidrug-resistance Gram-negative bacteria infections. Recently, the plasmid-mediated spread of the carbapenem resistance gene blaNDM poses a significant threat to public health, requiring global monitoring and surveillance. Here, we used both short-read (n = 2461) and long-read (n = 546) sequencing data to characterize the global distribution of blaNDM. We analyzed the replicon type of blaNDM-positive plasmids and found that the dominant plasmid type was different in diverse geographical locations. Although blaNDM gene has been transferred across diverse countries, its genetic backgrounds are highly conserved, and the mobile genetic element ISAba125, IS5, and IS26 may play an important role in the mobilization of blaNDM. A significant association was observed between host origin and gene presence/deletion variation on IncX3 plasmid, which may be a key factor in the bacterial adaption to diverse hosts. In this study, we analyzed the diversity, distribution and transmission of blaNDM-positive plasmids from a global perspective, and emphasize the importance of plasmid analysis for understanding the evolution and adaptation of blaNDM-positive plasmids and their co-evolution with bacterial genomes (resistome).

Prevention of colistin-induced neurotoxicity: a narrative review of preclinical data.

Polymyxin E or colistin is an effective antibiotic against MDR Gram-negative bacteria. Due to unwanted side effects, the use of this antibiotic has been limited for a long time, but in recent years, the widespread of MDR Gram-negative bacteria infections has led to its reintroduction. Neurotoxicity and nephrotoxicity are the significant dose-limiting adverse effects of colistin. Several agents with anti-inflammatory and antioxidant properties have been used for the prevention of colistin-induced neurotoxicity. This study aims to review the preclinical studies in this field to prepare guidance for future human studies. The data was achieved by searching PubMed, Scopus, and Google Scholar databases. All eligible pre-clinical studies performed on neuroprotective agents against colistin-induced neurotoxicity, which were published up to September 2023, were included. Finally, 16 studies (ten in vitro and eight in vivo) are reviewed. Apoptosis (in 13 studies), inflammatory (in four studies), and oxidative stress (in 14 studies) pathways are the most commonly reported pathways involved in colistin-induced neurotoxicity. The assessed compounds include non-herbal (e.g., ascorbic acid, rapamycin, and minocycline) and herbal (e.g., curcumin, rutin, baicalein, salidroside, and ginsenoside) agents. Besides these compounds, some other measures like transplantation of mitochondria and the use of nerve growth factor and mesenchymal stem cells could be motivating subjects for future research. Based on the data from experimental (in vitro and animal) studies, a combination of colistin with neuroprotective agents could prevent or decrease colistin-induced neurotoxicity. However, well-designed randomized clinical trials and human studies are essential for demonstrating efficacy.

Risk factors for clinical treatment failure and death in patients with ceftazidime-avibactam-resistant Gram-negative bacteria: A single-centre retrospective analysis

ObjectiveIn recent years, the number of Gram-negative bacteria (GNB) resistant to ceftazidime-avibactam (CZA) isolated from clinic has been increasing. We aimed to evaluate the clinical efficacy in patients with CZA-resistant GNB infections, and analyze the risk factors for clinical treatment failure and death. MethodsClinical data of patients with CZA-resistant GNB infections were collected retrospectively, and the influencing factors were analyzed by binary logistic regression. ResultsA total of 75 patients with CZA-resistant GNB infections were enrolled in the study, and the clinical effective rate was 56% (42/75). Multivariate analysis showed that continuous renal replacement therapy (CRRT) during anti-infection treatment was an independent risk factor for clinical treatment failure (OR 0.177, 95% CI 0.05–0.63, p ​= ​0.008). The 28-day mortality rate in 75 patients was 18.7% (14/75). Multivariate analysis showed that the regimen of colistin E 750,000 U q12h (OR 0.020, 95% CI 0.00–0.56, ​p ​= ​0.021), co-administration of tigecycline (OR 8.851, 95% CI 2.38–1316.87, ​p ​= ​0.012) and CRRT during anti-infection treatment (OR 79.610, 95% CI 4.87–1300.26, p ​= ​0.002) were independent affecting factors for 28-day mortality in patients with CZA-resistant GNB infections. ConclusionsPatients with CZA-resistant GNB infections had a higher possibility of clinical treatment failure and death. The results of the study based on small sample size from a single center showed that clinical treatment failure and death were more likely to happen in patients on CRRT, and the regimen of colistin E 750,000 U q12h or co-administration of tigecycline may reduce or increase mortality, respectively. Further validation in rigorously designed multicenter clinical studies with larger sample sizes is needed.

Pathogens in PICU before and during the SARS-CoV-2 pandemic in China: a multicenter retrospective study

BackgroundNonpharmacological interventions for COVID-19 could reduce the incidence of children hospitalized in pediatric intensive care units (PICU) and the incidence of children with bacterial infections. This study aimed to evaluate changes in the bacterial profile of children in PICU before and during the COVID-19 pandemics.MethodsThis is a retrospective study, involving clinical data of children with positive bacterial cultures admitted to the PICU respectively in 2019 and 2021.ResultsIn total 652 children were included in this study. The total number of hospitalized patients and the incidence of bacteria-positive children in 2021 were lower than those in 2019. There were no significant differences in the ratio of Gram-positive bacterial infection, Gram-negative bacteria infection or fungi infection between the two years. The rate of Streptococcus pneumoniae in 2021 was higher than that in 2019(p = 0.127). The incidence of Haemophilus influenzae in hospitalized patients decreased with a downward trend(p = 0.002). The distribution of previous underlying diseases in children admitted to PICU with different outcomes of bacterial infection between the two years were homogeneous (p > 0.05).ConclusionAfter the implementation of COVID-19 isolation, prevention and control measures, the number of hospitalizations and bacterial infections in PICU decreased, which may be due to changes in population’s behavior patterns. Meanwhile, the incidence of Haemophilus influenzae in hospitalized patients decreased with a downward trend.

Multidrug-resistant Gram-negative bacterial infections and associated factors in a Kenyan intensive care unit: a cross-sectional study

BackgroundPatients admitted to intensive care units (ICU) are at risk of Gram-negative bacteria (GNB) infections, especially those caused by multidrug-resistant (MDR) isolates, increasing morbidity, mortality, and healthcare costs. However, epidemiological surveillance data on MDR bacteria to inform infection prevention and control (IPCs) interventions is limited in our study setting. Here we assessed the prevalence and factors associated with GNB infections in ICU- patients admitted in our study setting.MethodsThis was a hospital-based cross-sectional study among patients admitted to ICU at the Nairobi West Hospital, Kenya, between January and October 2022. Altogether, we recruited 162 patients, excluding those hospitalized for less than 48 h and declining consent, and collected demographics and clinical data by case report form. Blood, wound and throat swab, ascetic tap, stool, urine, tracheal aspirate, and sputum samples were collected cultured. Isolates identity and antimicrobial susceptibility were elucidated using the BD Phoenix system.ResultsThe prevalence of GNB infections was 55.6%, predominated by urinary tract infections (UTIs). We recovered 13 GNB types, with Escherichia coli (33.3%) and Klebsiella pneumoniae (31.1%) as the most common isolates. Factors associated with GNB infections were a history of antibiotic use (aOR = 4.23, p = 0.001), nasogastric tube use (NGT, aOR = 3.04, p = 0.013), respiratory tract (RT, aOR = 5.3, p = 0.005) and cardiovascular (CV, aOR = 5.7, p = 0.024) conditions. 92% of the isolates were MDR,predominantly Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa.ConclusionWe report a high prevalence of MDR-GNB infections, predominated by UTI, in ICU, whereby patients with a history of antibiotic use, using the NGT, and having RT and CV conditions were at increased risk. To improve the management of ICU-admitted patients, continuous education, training, monitoring, evaluation and feedback on infection prevention and control are warranted in our study setting.

Identification of TMexCD-TOprJ-producing carbapenem-resistant Gram-negative bacteria from hospital sewage.

Carbapenems and tigecycline are crucial antimicrobials for the treatment of gram-negative bacteria infections. Recently, a novel resistance-nodulation-division (RND) efflux pump gene cluster, tmexCD-toprJ, which confers resistance to tigecycline, has been discovered in animals and clinical isolates. It was reported that hospital sewage could act as a reservoir for gram-negative bacteria with high antimicrobial resistance genes. In this study, we analyzed 84 isolates of carbapenem-resistant gram-negative bacteria (CR-GNB) from hospital sewage, and identified five isolates of TMexCD-ToprJ-producing CR-GNB, including one Raoultella ornithinolytica isolate and four Pseudomonas spp. isolates. All these five isolates carried at least one carbapenem resistance gene and were resistant to multiple antibiotics. Multiple tmexCD-toprJ clusters were detected, including tmexC2D2-toprJ2, tmexC3D3-toprJ3, tmexC3.2D3.3-toprJ1b and tmexC3.2D3-toprJ1b. Among these clusters, the genetic construct of tmexC3.2D3-toprJ1b showed 2-fold higher minimum inhibitory concentration (MIC) of tigecycline than other three variants. In addition, it was found that the tmexCD-toprJ gene cluster was originated from Pseudomonas spp. and mainly located on Tn6855 variants inserted in the same umuC-like genes on chromosomes and plasmids. This unit co-localized with blaIMP or blaVIM on IncHI5-, IncpJBCL41- and IncpSTY-type plasmids in the five isolates of TMCR-GNB. The IncHI5- and IncpSTY-type plasmids had the ability to conjugal transfer to E. coli J53 and P. aeruginosa PAO1, highlighting the potential risk of transfer of tmexCD-toprJ from Pseudomonas spp. to Enterobacterales. Importantly, genomic analysis showed that similar tmexCD-toprJ-harboring IncHI5 plasmids were also detected in human samples, suggesting transmission between environmental and human sectors. The emergence of TMCR-GNB from hospital sewage underscores the need for ongoing surveillance of antimicrobial resistance genes, particularly the novel resistance genes such as the tmexCD-toprJ gene clusters in the wastewater environment.

In vitro effects of deferoxamine on antibiotic susceptibility in Gram-negative bacteria.

Iron is a vital element for the growth of bacteria. Bacteria use several strategies to scavenge iron, such as siderophores, which are thought to be important virulence components. The mammalian host uses various iron-binding substances to make iron unavailable for bacterial uptake. Deferoxamine (DFO) is a semi-synthetic iron chelator that has been licensed for medical use. Iron chelators like DFO may provide an alternative therapeutic technique for treating Gram-negative bacteria infections, which frequently display multidrug resistance. We assumed that iron deprivation or interactions with the cell membrane caused by DFO or increased siderophore synthesis may cause the inhibition or inactivation of proteins and enzymes necessary for critical processes in bacteria. Additionally, we proposed that these bacterial alterations might be the origin of synergistic interactions between DFO and several antibiotics. To test this hypothesis, we used disc diffusion, broth microdilution and checkerboard synergy testing methods on combinations of DFO with ceftriaxone, cefepime, meropenem, amikacin, levofloxacin, and tigecycline, respectively, in a total of 55 isolates (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, and Proteus mirabilis strains - 11 isolates for each genus). No synergistic or antagonistic interactions were observed between DFO and the tested antibiotics in the E. coli, K. pneumoniae, P. aeruginosa, and A. baumannii isolates, while the addition of DFO significantly increased the inhibition zone diameters of cefepime, amikacin, meropenem, tigecycline, and levofloxacin in P. mirabilis isolates. According to the checkerboard synergy results, a synergistic interaction was found between DFO and tigecycline, cefepime and amikacin for P. mirabilis isolates. Among the investigated bacteria, a synergy between antibiotics and DFO was only discovered against P. mirabilis. We do not believe that this entirely disproves our hypothesis, though. The production of siderophores triggered by the increased metabolic activity of actively proliferating bacteria at the infection site may provide better results. Therefore, expanding these investigations and developing infection models through animal testing would be advantageous.

Looking for Stenotrophomonas maltophilia treatment: in vitro activity of ceftazidime/avibactam alone and in combination with aztreonam

During the Sars-Cov-2 pandemic, Stenotrophomonas maltophilia (S.maltophilia) secondary pulmonary infections have increased, especially in critically ill patients, highlighting the need for new therapeutic options. Trimethoprim-sulfamethoxazole (SXT) is the treatment of choice but the increase of resistant strains or adverse drug reactions limited its clinical use. Recently ceftazidime/avibactam (CZA) has been approved for the treatment of multi drug resistant (MDR) Gram-negative bacteria infections, including hospital acquired pneumonia. The aim of this study was to evaluate the in vitro activity of ceftazidime/avibactam (CZA) alone and in combination with aztreonam (ATM) against S. maltophilia clinical isolates by E-test method. Susceptibility of SXT and levofloxacin (LEV) was also investigated. Our results showed 22% of resistance to CZA, 2% to SXT and 26% to LEV. CZA in combination with ATM demonstrated synergistic activity against 86% of the strains, including all those resistant to CZA. The combination of CZA with ATM provides a new therapeutic option for the treatment of severe respiratory infections in critically ill patients.