Prevalence and antibiotic resistance of Acinetobacter baumannii among patients in postcardiac surgery intensive care units of Rajaei Hospital, Tehran

Overall status of carbapenem resistance among clinical isolates of Acinetobacter baumannii: a systematic review and meta-analysis

BACKGROUND

Resistance to carbapenems, the first-line treatment for infections caused by Acinetobacter baumannii, is increasing throughout the world. The aim of the present study was to determine the global status of resistance to carbapenems in clinical isolates of this pathogen, worldwide.

METHODS

Electronic databases were searched using the appropriate keywords, including: 'Acinetobacter' 'baumannii', 'Acinetobacter baumannii' and 'A. baumannii', 'resistance', 'antibiotic resistance', 'antibiotic susceptibility', 'antimicrobial resistance', 'antimicrobial susceptibility', 'carbapenem', 'carbapenems', 'imipenem', 'meropenem' and 'doripenem'. Finally, following some exclusions, 177 studies from various countries were included in this study. The data were then subjected to a meta-analysis.

RESULTS

The average resistance rate of A. baumannii to imipenem, meropenem and doripenem was 44.7%, 59.4% and 72.7%, respectively. A high level of heterogeneity (I2 > 50%, P value < 0.05) was detected in the studies representing resistance to imipenem, meropenem and doripenem in A. baumannii isolates. Begg's and Egger's tests did not indicate publication bias (P value > 0.05).

CONCLUSIONS

The findings of the current study indicate that the overall resistance to carbapenems in clinical isolates of A. baumannii is relatively high and prevalent throughout the world. Moreover, time trend analysis showed that the resistance has increased from the year 2000 to 2023. This emphasizes the importance of conducting routine antimicrobial susceptibility testing before selecting a course of treatment, as well as monitoring and controlling antibiotic resistance patterns in A. baumannii strains, and seeking novel treatment options to lessen the emergence and spread of resistant strains and to reduce the treatment failure.

Incidence of colistin heteroresistance among carbapenem-resistant Acinetobacter baumannii clinical isolates in a tertiary care hospital in Pakistan

PURPOSE

The emergence of colistin-resistant and heteroresistant strains of carbapenem-resistant Acinetobacter baumannii (CRAB) complicates treatment and exacerbates the global health crisis of drug-resistant bacteria. This study aims to investigate the incidence and clinical implications of colistin heteroresistance in carbapenem-resistant Acinetobacter baumannii isolates from a tertiary hospital in Pakistan.

MATERIALS AND METHODS

A total of 130 CRAB isolates were collected from December 2022 to December 2023. Colistin susceptibility was assessed using broth microdilution, and heteroresistance was detected through population analysis profiling.

RESULTS

Heteroresistance (HR) was identified in 31.5% (41/130) of the isolates, while 7.7% were colistin-resistant, despite initial susceptibility indicated by broth microdilution. Clinical data revealed that HR was associated with significant 14-day clinical failure but not with 30-day all-cause mortality. Heteroresistant strains showed extensive multidrug resistance, posing a serious threat to effective treatment.

CONCLUSIONS

The study highlights the critical need for accurate detection of colistin HR to prevent treatment failure and improve patient outcomes. The prevalence of colistin HR underscores the necessity for revised diagnostic and treatment strategies in Pakistan, emphasizing the importance of recognizing and addressing this emerging threat in healthcare settings.

Isolation and Identification of Effective Probiotics on Drug-Resistant Acinetobacter baumannii Strains and Their Biofilms

Introduction

This study aimed to identify, assess, and isolate strong lactobacilli demonstrating broad antibacterial and anti-biofilm activity against drug-resistant strains of Acinetobacter baumannii. Additionally, the mechanism of inhibition of these organisms was to be determined.

Methods

Over a 6-month period (from December 2021 to June 2022), 53 clinical A. baumannii strains were collected from clinical samples. Twenty probiotic strains were isolated from local dairy products. Antibacterial activity of Lactobacillus strains' cell-free supernatant (CFS) was identified using the agar well diffusion method and the microbroth dilution test. Anti-biofilm effect was performed by the microtiter plate assay. The MTT assay was also used to look into the probiotics' cytotoxic effects on the L929 fibroblast cell line.

Results

During the 6-month period, 53 clinical A. baumannii strains were obtained and identified. Out of 20 lactobacillus strains, the CFS of a lactobacillus strain (named L9) showed an inhibitory effect against all A. baumannii strains. Using the broth microdilution method, it was shown that the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of CFS extracts of L9 strains against A. baumannii strains were both ¼ mg/mL. The result of the anti-biofilm showed that the selected probiotic could inhibit biofilm formation. The most common organic acid produced by all Lactobacillus strains, according to the HPLC method, was lactic acid, which was followed by acetic acid. The L929 fibroblast cell line was used in the cytotoxicity assay, which revealed that 100% of the cells in the L929 fibroblast cell line survived treatment with successive doses of CFSs for a full day.

Conclusion

The probiotic strain isolated from local yogurt in this study showed potential anti-biofilm and antimicrobial properties against all drug-resistant Acinetobacter isolates. Given the increasing interest in probiotic microorganisms based on their high health benefits, further studies are recommended on the mechanisms of action between probiotics and A. baumannii strains to find new solutions for biological control and treatment of these infections without the use of antibiotics.

A Comprehensive Study of the Relationship between the Production of β-Lactamase Enzymes and Iron/Siderophore Uptake Regulatory Genes in Clinical Isolates of Acinetobacter baumannii

Background

The iron/siderophore uptake system (IUS) involved in the Acinetobacter baumannii pathogenicity. However, IUS's role in antibiotic resistance and the production of β-lactamase enzymes of A. baumannii are unclear. This study aimed to investigate the relationship between the production of β-lactamase enzymes and IUS regulatory genes in clinical isolates of A. baumannii. Methods. A. baumannii isolates were collected from clinical isolates using biochemical tests. The antibiotic resistance patterns and β-lactamase-producing strains were identified using the disk diffusion method (DDM). Also, IUS genes were detected by the polymerase chain reaction (PCR) method.

Results

Seventy-two (72) A. baumannii isolates were collected from a different clinical specimen. Gentamicin-resistant strains (43%) had the highest frequency, and aztreonam-resistant strains (12.5%) had the lowest frequency. Also, the distribution of AmpC and MBL producing isolates were 27.7% and 35%, respectively. Moreover, the frequencies of basD, bauA, pld, paaE, entA, feoB, hemO, and tonB genes were as follows: 12.5%, 15.2%, 11.1%, 15.2%, 19.4%, 16.6%, 23.6%, and 6.9%. Further, a strong correlation was observed between the abundance of β-lactamase-producing strains and IUS genes.

Conclusions

Based on our knowledge from this study, the association between β-lactamase production and IUS genes in A. baumannii plays an essential role in the emergence of drug-resistant strains.

Molecular Epidemiology and Clone Transmission of Carbapenem-Resistant Acinetobacter baumannii in ICU Rooms

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a major cause of nosocomial infections and hospital outbreaks worldwide, remaining a critical clinical concern. Here we characterized and investigated the phylogenetic relationships of 105 CRAB isolates from an intensive care unit from one hospital in China collected over six years. All strains carried bla_OXA-23, bla_OXA-66 genes for carbapenem resistance, also had high resistance gene, virulence factor, and insertion sequence burdens. Whole-genome sequencing revealed all strains belonged to ST2, the global clone CC2. The phylogenetic analysis based on the core genome showed all isolates were dominated by a single lineage of three clusters and eight different clones. Two clones were popular during the collection time. Using chi-square test to identify the epidemiologically meaningful groupings, we found the significant difference in community structure only existed in strains from separation time. The haplotype and median-joining network analysis revealed genetic differences appeared among clusters and changes occurred overtime in the dominating cluster. Our results highlighted substantial multidrug-resistant CRAB burden in the hospital ICU environment demonstrating potential clone outbreak in the hospital.