Acquisition and clearance of multidrug resistant Acinetobacter baumannii on healthy young adults concurrently burned in a dust explosion in Taiwan: the implication for antimicrobial stewardship

Genome characterization of the novel lytic phage vB_AbaAut_ChT04 and the antimicrobial activity of its lysin peptide against Acinetobacter baumannii isolates from different time periods

Acinetobacter baumannii is an important opportunistic pathogen, usually associated with immunocompromised individuals with a prolonged period of stay in a hospital. Currently, the incidence of multi-drug resistant A. baumannii (MDR-AB) and extensively drug-resistant A. baumannii (XDR-AB) is increasing rapidly in Thailand, mirroring the trend worldwide. Novel therapeutic approaches for the treatment of A. baumannii infection using bacteriophages are being evaluated, and the use of phage-derived peptides is being tested as alternative approach to fighting infection. In this study, we isolated and determined the biological features of a lytic A. baumannii phage called vB_AbaAut_ChT04 (vChT04). The vChT04 phage was classified as a member of the family Autographiviridae of the class Caudoviricetes. It showed a short latent period (10 min) and a large burst size (280 PFU cell-1), and it was able to infect 52 out of 150 clinical MDR-AB strains tested (34.67%). Most of the phage-sensitive strains were A. baumannii strains that had been isolated during the same year that the phage was isolated. The phage showed activity across a broad pH (pH 5.0-8.0) and temperature (4-37°C) range. Whole-genome analysis revealed that the vChT04 genome comprises 41,158 bp with a 39.3% GC content and contains 48 open reading frames (ORFs), 28 of which were assigned putative functions based on homology to previously identified phage genes. Comparative genomic analysis demonstrated that vChT04 had the highest similarity to phage vB_AbaP_WU2001, which was isolated in the southern part of Thailand. An endolysin gene found in the vChT04 genome was used to synthesize an antimicrobial peptide (designated as PLysChT04) and its antimicrobial activity was evaluated using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. The MIC and MBC values of peptide PLysChT04 against MDR-AB and XDR-AB were 312.5-625 µg/mL, and it was able to inhibit both phage-susceptible and phage-resistant isolates collected over different time periods. PLysChT04 showed good efficacy in killing drug-resistant A. baumannii and other bacterial strains, and it is a promising candidate for development as an alternative therapeutic agent targeting A. baumannii infections.

Tigecycline Therapy for Infections Caused by Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae in Critically Ill Patients

: We aimed to evaluate tigecycline on the clinical effectiveness in treating complicated skin and soft tissue infections (cSSTI), complicated intra-abdominal infections (cIAI), and pneumonia, caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, as data are limited. From three medical centers in Taiwan, we retrospectively studied the cSSTI, cIAI, and/or pneumonia caused by ESBL-producing Enterobacteriaceae. Among the 71 patients, including 39 patients infected with Klebsiella pneumoniae, 30 infected with Escherichia coli and others, the clinical success rate of tigecycline-based therapy was 80%-90% for pneumonia and cSSTI caused by E. coli and 50%-60% for cIAI caused by K. pneumoniae and E. coli. Microbiological and clinical outcome of pneumonia caused by carbapenem-resistant K. pneumoniae was poor. Univariate Cox analysis showed that dyspnea, SOFA score, septic shock, thrombocytopenia, prolonged prothrombin time, and lesser microbiological eradication were significant factors associated with 30-day mortality after the end of therapy. Cox regression proportional hazards model revealed dyspnea and a SOFA score > 8 to be independently associated with time to death. For ESBL producers, tigecycline showed good effects for cSSTI and pneumonia by E. coli, ordinary for cIAI, but ineffective for pneumonia by K. pneumoniae. Dyspnea and a high SOFA score predict a poor outcome.

Trends in microbial profile of burn patients following an event of dust explosion at a tertiary medical center

Background

Microbial infection is the main cause of increased morbidity and mortality in burn patients, especially infections caused by multiple drug-resistant organisms (MDRO). The purpose of this study was to explore major microbial trends in burn patients.

Methods

This retrospective study was conducted at burn wards and intensive care units, where burn patients were admitted following an event of dust explosion. Data were collected for a number of variables including severity of burns, demographic and clinical characteristics, laboratory data, and therapeutic devices.

Results

A total of 1132 specimens were collected from 37 hospitalized burn patients with mean TBSA of 46.1%.The most commonly isolated species were Staphylococcus spp. (22.4%). The highest rate of antibiotic resistance was observed in carbapenem–resistant A. baumannii (14.6%), followed by methicillin-resistant S. aureus (11.3%). For each additional 10% TBSA, the isolation of MDRO increased 2.58–17.57 times (p < 0.05); for each additional 10% of the third-degree burn severity, the risk of MDRO significantly decreased by 47% (95% CI, 0.38–0.73, p < 0.001) by Cox model.

Conclusions

The proportion of overall microbial isolates increased with the increase in TBSA and duration of time after burns. The extent of TBSA was the most important factor affecting MDRO.

Modifiable risk factors for multidrug-resistant Gram-negative infection in critically ill burn patients: a systematic review and meta-analysis

BACKGROUND

We conducted a systematic review and meta-analysis to identify potentially modifiable risk factors for multidrug-resistant Gram-negative colonization or infection in critically ill burn patients.

METHODS

A systematic search was conducted of PubMed, Embase, CINAHL, Web of Science and Central (Cochrane). Risk factors including antibiotic use and hospital interventions were summarized in a random-effects meta-analysis. Risk of publication bias was assessed using the Grading of Recommendations Assessment, Development and Evaluation method and funnel plots.

RESULTS

A total of 11 studies met the inclusion criteria. We identified several potentially modifiable risk factors and were able to grade their importance based on effect size. Related to prior antibiotic exposure, extended-spectrum cephalosporins (pooled odds ratio (OR) 7.00, 95% confidence interval (CI) 2.77-17.67), carbapenems (pooled OR 6.65, 95% CI 3.49-12.69), anti-pseudomonal penicillins (pooled OR 4.23, 95% CI 1.23-14.61) and aminoglycosides (pooled OR 4.20, 95% CI 2.10-8.39) were most significant. Related to hospital intervention, urinary catheters (pooled OR 11.76, 95% CI 5.03-27.51), arterial catheters (pooled OR 8.99, 95% CI 3.84-21.04), mechanical ventilation (pooled OR 5.49, 95% CI 2.59-11.63), central venous catheters (pooled OR 4.26, 95% CI 1.03-17.59), transfusion or blood product administration (pooled OR 4.19, 95% CI 1.48-11.89) and hydrotherapy (pooled OR 3.29, 95% CI 1.64-6.63) were most significant.

CONCLUSION

Prior exposure to extended-spectrum cephalosporins and carbapenems, as well as the use of urinary catheters and arterial catheters pose the greatest threat for infection or colonization with multidrug-resistant Gram-negative organisms in the critically ill burn patient population.

Association between higher ambient temperature and orthopaedic infection rates: a systematic review and meta-analysis

INTRODUCTION

Many infectious diseases display seasonal variation corresponding with particular conditions. In orthopaedics a growing body of evidence has identified surges in post-operative infection rates during higher temperature periods. The aim of this research was to collate and synthesize the current literature on this topic.

METHODS

A systematic review and meta-analysis was performed using five databases (PubMed, Embase, CINAHL, Web of Science and Central (Cochrane)). Study quality was assessed using the Grading of Recommendations Assessment, Development and Evaluation method. Odds ratios (ORs) were calculated from monthly infection rates and a pooled OR was generated using the DerSimonian and Lairds method. A protocol for this review was registered with the National Institute for Health Research International Prospective Register of Systematic Reviews (CRD42017081871).

RESULTS

Eighteen studies analysing over 19 000 cases of orthopaedic related infection met inclusion criteria. Data on 6620 cases and 9035 controls from 12 studies were included for meta-analysis. The pooled OR indicated an overall increased odds of post-operative infection for patients undergoing orthopaedic procedures during warmer periods of the year (pooled OR 1.16, 95% confidence interval 1.04-1.30).

CONCLUSION

A small but significantly increased odds of post-operative infection may exist for orthopaedic patients who undergo procedures during higher temperature periods. It is hypothesized that this effect is geographically dependent and confounded by meteorological factors, local cultural variables and hospital staffing cycles.

Clinical features, outcomes, and molecular characteristics of an outbreak of Staphylococcus haemolyticus infection, among a mass-burn casualty patient group, in a tertiary center in northern Taiwan

BACKGROUND/PURPOSE

We reported an outbreak of Staphylococcus haemolyticus (SH) infection in a group of young patients (mean age 21.6) simultaneously hospitalized due to a mass-burn incident. This study analyzed the clinical features of these patients and the microbiological characteristics of the outbreak.

METHODS

All 50 patients hospitalized for burns were enrolled, and their clinical differences were analyzed based on culture results. A drug sensitivity test and pulsed-field gel electrophoresis (PFGE) were conducted to analyze the microbiological difference between SH isolates from the mass-burn casualty patients (the study group) and SH isolates from other patients hospitalized during the same period (the control group) with the intention of identifying the strain of SH outbreak.

RESULTS

Patients with isolated SH (N = 36) had a significantly higher disease severity (higher revised Baux score, APACHE II score, and concurrent bacteremia rate), and a significantly poorer clinical outcome (longer ICU and hospital stay, and longer MV usage). Significant differences in the phenotype (antibiotics drug sensitivity test) and genotype (PFGE typing) were observed between the study and control groups. The dominant PFGE type C identified among the study group was related to poorer outcomes in a subgroup analysis.

CONCLUSION

A dominant PFGE type of SH infection was found in these mass-burn casualty patients. Pathogenesis or virulence factors may have contributed to our results. Further study of isolated SH should be conducted.

The antimicrobial cathelicidin peptide hlF(1-11) attenuates alveolar macrophage pyroptosis induced by Acinetobacter baumannii in vivo

Acinetobacter baumannii is a Gram-negative coccobacillus found primarily in hospital settings that has recently emerged as a source of hospital-acquired infections, including bacterial pneumonia. The hLF(1-11) peptide comprising the first 11 N-terminal residues of human lactoferrin exerts antimicrobial activity in vivo and was highly effective against multidrug-resistant A. baumannii strains in vitro and in vivo. Pyroptosis is a caspase-1-dependent inflammatory cell death process and is induced by various microbial infections. In the present study, we investigated the molecular mechanisms that regulate pyroptosis induced by A. baumannii in macrophages. Our results revealed that A. baumannii induced pyroptosis through caspase-1 activation and IL-1β production. We also found that caspase-1 activation and IL-1β maturation in A. baumannii-triggered pyroptotic cell death were reduced by hLF(1-11) treatment. Moreover, hLF(1-11) inhibited the A. baumannii-induced caspase-1 activation and pyroptosis of pulmonary alveolar macrophages in vivo.