Comparative phenotypic and genotypic analysis of community-acquired and hospital-acquired intra-abdominal infections among liver transplanted patients

AIM

During liver transplantation, both hospital-acquired (HA) and community-acquired (CA) intra-abdominal infections (IAIs) are involved causing life-threatening diseases. Therefore, comparative studies of aerobic and facultative anaerobic HA-IAIs and CA-IAIs after liver transplantation surgery are necessary.

METHODS AND RESULTS

The species of detected isolates (310) from intra-abdominal fluid were identified and classified into hospital-acquired intra-abdominal infections (HA-IAIs) and community-acquired intra-abdominal infections (CA-IAIs). Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii were the most commonly detected species. The resistant phenotypes were commonly detected among the HA-IAIs; however, the virulent phenotypes were the predominant strains of CA-IAIs. Regrettably, the resistance profiles were shocking, indicating the inefficacy of monotherapy in treating these isolates. Therefore, we confirmed the use of empirical combination therapies of amikacin and meropenem for treating all IAIs (FICI ≤ 0.5). Unfortunately, the high diversity and low clonality of all identified HA and CA-IAIs were announced with D-value in the range of 0.992-1.

CONCLUSION

This diversity proves that there are infinite numbers of infection sources inside and outside healthcare centers.

Symptomatic Subdural Hygroma Following Acinetobacter Meningitis in an Infant

We present a case of a full-term newborn with prenatal congenital heart disease, admitted to a level III neonatal intensive care unit. After undergoing a surgical palliation procedure, he experienced a complicated recovery, including nosocomial sepsis with isolation of Acinetobacter nosocomialis in both blood and cerebrospinal fluid. Subsequently, he developed focal clonic seizures that were refractory to antiepileptic drugs, and imaging studies revealed the presence of a subdural hygroma. Surgical drainage was performed, resulting in the resolution of the seizures. This report highlights the rare occurrence of Acinetobacter meningitis unrelated to neurosurgery and its progression to subdural hygroma in an infant, emphasizing the importance of recognizing such complications as potential causes of refractory seizures following infectious processes.

Use of Eravacycline for Acinetobacter baumannii Infections: A Case Series

This case series describes the clinical course of 10 patients who received eravacycline antimicrobial therapy for a variety of different Acinetobacter baumannii infection types at a community care hospital.

OXA-66 structure and oligomerisation of OXAAb enzymes

The OXA β-lactamases are responsible for hydrolysing β-lactam antibiotics and contribute to the multidrug-resistant phenotype of several major human pathogens. The OXAAb enzymes are intrinsic to Acinetobacter baumannii and can confer resistance to carbapenem antibiotics. Here we determined the structure of the most prevalent OXAAb enzyme, OXA-66. The structure of OXA-66 was solved at a resolution of 2.1 Å and found to be very similar to the structure of OXA-51, the only other OXAAb enzyme that has had its structure solved. Our data contained one molecule per asymmetric unit, and analysis of positions responsible for dimer formation in other OXA enzymes suggest that OXA-66 likely exists as a monomer.

Efficacy and In Vitro Activity of Novel Antibiotics for Infections With Carbapenem-Resistant Gram-Negative Pathogens

Infections by Gram-negative multi-drug resistant (MDR) bacterial species are difficult to treat using available antibiotics. Overuse of carbapenems has contributed to widespread resistance to these antibiotics; as a result, carbapenem-resistant Enterobacterales (CRE), A. baumannii (CRAB), and P. aeruginosa (CRPA) have become common causes of healthcare-associated infections. Carbapenems, tigecycline, and colistin are the last resource antibiotics currently used; however, multiple reports of resistance to these antimicrobial agents have been documented worldwide. Recently, new antibiotics have been evaluated against Gram-negatives, including plazomicin (a new aminoglycoside) to treat CRE infection, eravacycline (a novel tetracycline) with in vitro activity against CRAB, and cefiderocol (a synthetic conjugate) for the treatment of nosocomial pneumonia by carbapenem-non-susceptible Gram-negative isolates. Furthermore, combinations of known β-lactams with recently developed β-lactam inhibitors, such as ceftazidime-avibactam, ceftolozane-tazobactam, ceftazidime-tazobactam, and meropenem-vaborbactam, has been suggested for the treatment of infections by extended-spectrum β-lactamases, carbapenemases, and AmpC producer bacteria. Nonetheless, they are not active against all carbapenemases, and there are reports of resistance to these combinations in clinical isolates.This review summarizes and discusses the in vitro and clinical evidence of the recently approved antibiotics, β-lactam inhibitors, and those in advanced phases of development for treating MDR infections caused by Gram-negative multi-drug resistant (MDR) bacterial species.

An Uncommon Cause of Acute Transverse Myelitis Following Acinetobacter Baumannii-Associated UTI, Which Responded to Intravenous Pulse Methylprednisolone Alone

Acute transverse myelitis (ATM) is a non-compressive localized inflammation involving one or more levels of the spinal cord due to various etiologies characterized by motor weakness, sensory impairments, and autonomic dysfunction. It can be idiopathic or primary or secondary due to infection, autoimmune disorder, connective tissue disorder, and uncommonly after vaccination which came to the limelight during the ongoing massive vaccine drive against coronavirus disease 2019 (COVID-19). We report a case of a 21-years-old male who presented with gradually progressive weakness of both lower limbs following urinary tract infection (UTI) with a history of similar illness in the family which improved with high dose methylprednisolone and antibiotic therapy followed by physical rehabilitation. A diagnosis of long segment ATM possibly following UTI was suggested after ruling out other secondary causes and was confirmed by magnetic resonance imaging (MRI) of the spinal cord. Asymmetric symptoms and signs with small lesions involving <two vertebral segments, peripheral lesion, presence of Lhermitte's sign and relapsing-remitting course distinguish ATM from more debilitating disorder multiple sclerosis (MS) in patients with family history. Infection like UTI can precipitate ATM as well as UTI may develop along with neurogenic lower urinary tract dysfunction (NLUTD) even after recovery from the motor and sensory impairment. Patients with acute transverse myelitis need to be on regular follow up particularly those with subacute presentation and positive family history to rule out relapse and development of multiple sclerosis. Common etiologies like UTI may precipitate uncommon disorders like ATM.

The roles of history, chance, and natural selection in the evolution of antibiotic resistance

History, chance, and selection are the fundamental factors that drive and constrain evolution. We designed evolution experiments to disentangle and quantify effects of these forces on the evolution of antibiotic resistance. Previously, we showed that selection of the pathogen Acinetobacter baumannii in both structured and unstructured environments containing the antibiotic ciprofloxacin produced distinct genotypes and phenotypes, with lower resistance in biofilms as well as collateral sensitivity to β-lactam drugs (Santos-Lopez et al., 2019). Here we study how this prior history influences subsequent evolution in new β-lactam antibiotics. Selection was imposed by increasing concentrations of ceftazidime and imipenem and chance differences arose as random mutations among replicate populations. The effects of history were reduced by increasingly strong selection in new drugs, but not erased, at times revealing important contingencies. A history of selection in structured environments constrained resistance to new drugs and led to frequent loss of resistance to the initial drug by genetic reversions and not compensatory mutations. This research demonstrates that despite strong selective pressures of antibiotics leading to genetic parallelism, history can etch potential vulnerabilities to orthogonal drugs.

Correlation between Acinetobacter baumannii Resistance and Hospital Use of Meropenem, Cefepime, and Ciprofloxacin: Time Series Analysis and Dynamic Regression Models

Acinetobacter baumannii is one of the most difficult-to-treat pathogens worldwide, due to developed resistance. The aim of this study was to evaluate the use of widely prescribed antimicrobials and the respective resistance rates of A. baumannii, and to explore the relationship between antimicrobial use and the emergence of A. baumannii resistance in a tertiary care hospital. Monthly data on A. baumannii susceptibility rates and antimicrobial use, between January 2014 and December 2017, were analyzed using time series analysis (Autoregressive Integrated Moving Average (ARIMA) models) and dynamic regression models. Temporal correlations between meropenem, cefepime, and ciprofloxacin use and the corresponding rates of A. baumannii resistance were documented. The results of ARIMA models showed statistically significant correlation between meropenem use and the detection rate of meropenem-resistant A. baumannii with a lag of two months (p = 0.024). A positive association, with one month lag, was identified between cefepime use and cefepime-resistant A. baumannii (p = 0.028), as well as between ciprofloxacin use and its resistance (p < 0.001). The dynamic regression models offered explanation of variance for the resistance rates (R² > 0.60). The magnitude of the effect on resistance for each antimicrobial agent differed significantly.

Bacterial Genome Wide Association Studies (bGWAS) and Transcriptomics Identifies Cryptic Antimicrobial Resistance Mechanisms in Acinetobacter baumannii

Antimicrobial resistance (AMR) in the nosocomial pathogen, Acinetobacter baumannii, is becoming a serious public health threat. While some mechanisms of AMR have been reported, understanding novel mechanisms of resistance is critical for identifying emerging resistance. One of the first steps in identifying novel AMR mechanisms is performing genotype/phenotype association studies; however, performing these studies is complicated by the plastic nature of the A. baumannii pan-genome. In this study, we compared the antibiograms of 12 antimicrobials associated with multiple drug families for 84 A. baumannii isolates, many isolated in Arizona, USA. in silico screening of these genomes for known AMR mechanisms failed to identify clear correlations for most drugs. We then performed a bacterial genome wide association study (bGWAS) looking for associations between all possible 21-mers; this approach generally failed to identify mechanisms that explained the resistance phenotype. In order to decrease the genomic noise associated with population stratification, we compared four phylogenetically-related pairs of isolates with differing susceptibility profiles. RNA-Sequencing (RNA-Seq) was performed on paired isolates and differentially-expressed genes were identified. In these isolate pairs, five different potential mechanisms were identified, highlighting the difficulty of broad AMR surveillance in this species. To verify and validate differential expression, amplicon sequencing was performed. These results suggest that a diagnostic platform based on gene expression rather than genomics alone may be beneficial in certain surveillance efforts. The implementation of such advanced diagnostics coupled with increased AMR surveillance will potentially improve A. baumannii infection treatment and patient outcomes.

Photoinactivation of ESKAPE pathogens: overview of novel therapeutic strategy

The emergence of antimicrobial drug resistance requires development of alternative therapeutic options. Multidrug-resistant strains of Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa and Enterobacter spp. are still the most commonly identified antimicrobial-resistant pathogens. These microorganisms are part of the so-called 'ESKAPE' pathogens to emphasize that they currently cause the majority of hospital acquired infections and effectively 'escape' the effects of antibacterial drugs. Thus, alternative, safer and more efficient antimicrobial strategies are urgently needed, especially against 'ESKAPE' superbugs. Antimicrobial photodynamic inactivation is a therapeutic option used in the treatment of infectious diseases. It is based on a combination of a photosensitizer, light and oxygen to remove highly metabolically active cells.

Fluorescence-Based Detection of Natural Transformation in Drug-Resistant Acinetobacter baumannii

Acinetobacter baumannii is a nosocomial agent with a high propensity for developing resistance to antibiotics. This ability relies on horizontal gene transfer mechanisms occurring in the Acinetobacter genus, including natural transformation. To study natural transformation in bacteria, the most prevalent method uses selection for the acquisition of an antibiotic resistance marker in a target chromosomal locus by the recipient cell. Most clinical isolates of A. baumannii are resistant to multiple antibiotics, limiting the use of such selection-based methods. Here, we report the development of a phenotypic and selection-free method based on flow cytometry to detect transformation events in multidrug-resistant (MDR) clinical A. baumannii isolates. To this end, we engineered a translational fusion between the abundant and conserved A. baumannii nucleoprotein (HU) and the superfolder green fluorescent protein (sfGFP). The new method was benchmarked against the conventional antibiotic selection-based method. Using this new method, we investigated several parameters affecting transformation efficiencies and identified conditions of transformability one hundred times higher than those previously reported. Using optimized transformation conditions, we probed natural transformation in a set of MDR clinical and nonclinical animal A. baumannii isolates. Regardless of their origin, the majority of the isolates displayed natural transformability, indicative of a conserved trait in the species. Overall, this new method and optimized protocol will greatly facilitate the study of natural transformation in the opportunistic pathogen A. baumannii IMPORTANCE Antibiotic resistance is a pressing global health concern with the rise of multiple and panresistant pathogens. The rapid and unfailing resistance to multiple antibiotics of the nosocomial agent Acinetobacter baumannii, notably to carbapenems, prompt to understand the mechanisms behind acquisition of new antibiotic resistance genes. Natural transformation, one of the horizontal gene transfer mechanisms in bacteria, was only recently described in A. baumannii and could explain its ability to acquire resistance genes. We developed a reliable method to probe and study natural transformation mechanism in A. baumannii More broadly, this new method based on flow cytometry will allow experimental detection and quantification of horizontal gene transfer events in multidrug-resistant A. baumannii.

Outbreak Column 22: How to manage an outbreak

This outbreak column uses the Health Protection Scotland (HPS) Outbreak Process and Algorithm to examine and reflect on a published outbreak report. The report involved an extensively drug-resistant Acinetobacter baumannii in an oncology unit. High-reliability theory is then used to reflect on how the outbreak was managed and consider how best to improve local outbreak prevention, preparedness, detection and management. The conclusion of this exercise is that if the possibility of an era of untreatable infections caused by antibiotic-resistant organisms is to be significantly postponed, Infection Prevention and Control Teams must improve their ability to get others to prevent cross-transmission in the absence of recognised risks.

[Infection of chronic otitis media with Acinetobacter：6 cases report]

Objective:To investigate the clinical characteristics, diagnostic methods and prognosis of patients with chronic otitis media with Acinetobacter infection. Method:Retrospective analysis of clinical data of 6 cases of chronic otitis media complicated with Acinetobacter infection. Including history, clinical manifestations, laboratory examination, audiology, inner ear, CT, MRI imaging characteristics, treatment and prognosis of etc. to summarize the clinical characteristics, diagnosis and treatment of chronic otitis media with Acinetobacter infection. Result:The age was between 17 years old and 61 years old (Median age 30 years) .Two of them was male and 4 were female. Four cases were had underlying diseases. Five cases with main symptom of cholesteatoma, 1 case with earache symptoms, and 1 case with facial paralysis symptoms. Four cases had vary degrees of physical decline and destruction of bone. After surgery treatment, five patients improved ear pus, among 3 cases was cured, 2 cases of recurrence. Conclusion:Chronic otitis media with Acinetobacter infection occurs in the patient with elderly, poor physical constitution. However, the recurrence rate of conventional treatment is higher. The disease has high misdiagnosis rate. Operation combined with sensitive antibiotic therapy is a radical cure method.

Treatment for patients with multidrug resistant Acinetobacter baumannii pulmonary infection

Bacterial infections are common but have become increasingly resistant to drugs. The aim of the present study was to examine the combined treatment of traditional Chinese and Western medicine in 30 cases of pulmonary infection with multidrug resistant Acinetobacter baumannii. Patients were divided into groups A and B according to drug treatments. Cefoperazone or sulbactam and tanreqing were administered in group A, and cefoperazone or sulbactam in group B. The curative effect and prognosis of the two groups were recorded and the remaining treatments were performed routinely in the clinic. For the combined therapy group, which was administered sulperazone and tanreqing, 8 patients were recovered, 6 patients had significant effects, 3 patients exhibited some improvement and 1 patient had no response. One of the patients did not survive after 28 days. By contrast, there were 4 patients that were successfully treated, 3 patients with significant effects, 2 patients with some improvement and 2 patients had no response in the sulperazone group, and 4 patients did not survive after 28 days. In conclusion, the combined therapy of cefoperazone or sulbactam supplemented with tanreqing was identified to be more effective than cefoperazone or sulbactam as monotherapy, for treating multidrug resistant Acinetobacter baumannii.

Inferred metagenomic comparison of mucosal and fecal microbiota from individuals undergoing routine screening colonoscopy reveals similar differences observed during active inflammation

The mucosal microbiota lives in close proximity with the intestinal epithelium and may interact more directly with the host immune system than the luminal/fecal bacteria. The availability of nutrients in the mucus layer of the epithelium is also very different from the gut lumen environment. Inferred metagenomic analysis for microbial function of the mucosal microbiota is possible by PICRUSt. We recently found that by using this approach, actively inflamed tissue of ulcerative colitis (UC) patients have mucosal communities enriched for genes involved in lipid and amino acid metabolism, and reduced for carbohydrate and nucleotide metabolism. Here, we find that the same bacterial taxa (e.g. Acinetobacter) and predicted microbial pathways enriched in actively inflamed colitis tissue are also enriched in the mucosa of subjects undergoing routine screening colonoscopies, when compared with paired samples of luminal/fecal bacteria. These results suggest that the mucosa of healthy individuals may be a reservoir of aerotolerant microbial communities expanded during colitis.

Isolation and identification of endosulfan-degrading bacteria and evaluation of their bioremediation in kor river, iran

Objectives

Endosulfan is a lipophilic insecticide, which causes severe health issues due to its environmental stability, toxicity, and biological reservation in organisms. It is found in the atmosphere, soil, sediments, surface waters, rain, and food in almost equal proportions. The aim of this study was to isolate and identify endosulfan-degrading bacteria from the Kor River and evaluate the possibility of applying bioremediation in reducing environmental pollution in the desired region.

Methods

Samples of surface sediments and water were collected from three different stations in two seasons (summer and autumn), as these are areas with high agricultural activity. Isolated bacteria were identified by various biochemical tests and morphological characteristics. The amounts of degradation of endosulfan isomers and metabolites produced as a result of biodegradation were then analyzed using gas chromatography/mass spectrometry.

Results

In this study, the following five bacterial genera were able to degrade endosulfan: Klebsiella, Acinetobacter, Alcaligenes, Flavobacterium, and Bacillus. During biodegradation, metabolites of endosulfan diol, endosulfan lactone, and endosulfan ether were also produced, but these had lesser toxicity compared with the original compound (i.e., endosulfan).

Conclusion

The five genera isolated can be used as a biocatalyst for bioremediation of endosulfan.