Antibiotic resistance profile and co-production of extended spectrum beta lactamases and AmpC in Acinetobacter spp. in a level 1 trauma center from India

Associations between β-Lactamase Types of Acinetobacter baumannii and Antimicrobial Resistance

Background and objective: Acinetobacter baumannii (A. baumannii) is an important nosocomial pathogen that not only possesses intrinsic resistance to many classes of antibiotics, but is also capable of rapidly developing antimicrobial resistance during treatment. The aim of this study was to determine the characteristics of resistance of A. baumannii strains to β-lactams and other tested antibiotics, to evaluate the associations between the phenotypes of resistance to β-lactams and other tested antibiotics, and to evaluate the changes in antibiotic resistance of A. baumannii strains over 5 years by comparing the periods of 2016-2017 and 2020-2021. Materials and methods: A total of 233 A. baumannii strains were isolated from different clinical specimens of patients treated at the Hospital of Lithuanian University of Health Sciences in 2016-2017 (n = 130) and 2021-2022 (n = 103). All clinical cultures positive for A. baumannii were analyzed. The type of β-lactamase was detected by phenotypic methods using ESBL plus AmpC screen disk tests and the combination meropenem disk test. Results: In both periods, all A. baumannii strains were resistant to ciprofloxacin; resistance to carbapenems, piperacillin/tazobactam, gentamicin, and tobramycin was noted in more than 80% of strains. A comparison of two periods showed that the percentages of A. baumannii strains producing two or three types of β-lactamases were significantly greater in 2021-2022 than in 2016-2017 (94.2% and 5.8% vs. 17.7% and 2.3%, respectively, p < 0.001). Isolates producing two or three types of β-lactamases were more often resistant to tigecycline, tetracycline, and doxycycline than strains producing one type of β-lactamase (p < 0.001). Conclusions: The frequency of isolation of A. baumannii strains producing two different types of β-lactamases (AmpC plus KPC, AmpC plus ESBL, or ESBL plus KPC) or three types of β-lactamases (AmpC, KPC, and ESBL) and the resistance rates to ampicillin/sulbactam, tigecycline, tetracycline, and doxycycline were significantly greater in 2020-2021 as compared with 2016-2017. The production of two or three types of β-lactamases by A. baumannii strains was associated with higher resistance rates to tetracyclines.

Rapid identification of carbapenemases by CarbAcineto NP test and the rate of beta-lactamases among Acinetobacter baumannii from a teaching hospital

Background and Objectives

Acinetobacter baumannii has emerged as a major organism accounting for hospital acquired infections particularly in intensive care units. Due to production of different kinds of beta lactamases these bacteria have developed drug resistance rendering the treatment of such infections very difficult and expensive. Rapid identification of A. baumannii producing such beta-lactamases is the need of the hour in reducing morbidity and mortality associated with A. baumannii infections.

Materials and Methods

A. baumannii was isolated from clinical samples like endotracheal aspirates, sputum, urine, exudates using standard culture techniques. Identification and drug sensitivity was done using Vitek 2 system. All the isolates were subjected to detection of ESBLs using phenotypic confirmatory test, plasmid mediated AmpC beta-lactamase by AmpC disc test, Carbapenemase production by CarbAcineto NP Test and Modified hodge method.

Results

149 A. baumannii isolates were analysed for antimicrobial susceptibility and various beta-lactamase production. Results were evaluated for statistical significance using Chi-Square and P value. 81.8% of isolates were from male patients with majority of them above 50 years of age. 88.5% of samples were from ventilator associated pneumonia patients. 83.8% of isolates were sensitive to tigecycline. Only 10% to 12% of isolates were sensitive to carbapenems. 23.4% of isolates were ESBL producers and 46.9% of them were AmpC producers. Modified Hodge test method identified 63.7% of A. baumannii as carbapenemase producers where as CarbAcineto NP test identified 63% and exibiting 94.74% sensitivity, 93.22% specificity when compared to Modified Hodge test.

Conclusion

Multidrug resistant Acinetobacter spp. is on the rise. Present study showed that high percentage of drug resistance in A. baumannii could be due to production of ESBLs, AmpC and carbapenemases. Among all beta lactamases carbapenemase producers are more and quickly raising in A. baumannii. Rapid, cost effective assay which can be adopted in all clinical laboratories is critical to prevent their further transmission particularly in hospital environment.

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.