Profiling Antibiotic Resistance in Acinetobacter calcoaceticus

Acinetobacter Non-baumannii Species: Occurrence in Infections in Hospitalized Patients, Identification, and Antibiotic Resistance

BACKGROUND

Acinetobacter species other than A. baumannii are becoming increasingly more important as opportunistic pathogens for humans. The primary aim of this study was to assess the prevalence, species distribution, antimicrobial resistance patterns, and carbapenemase gene content of clinical Acinetobacter non-baumannii (Anb) isolates that were collected as part of a sentinel surveillance program of bacterial infections in hospitalized patients. The secondary aim was to evaluate the performance of MALDI-TOF MS systems for the species-level identification of Anb isolates.

METHODS

Clinical bacterial isolates were collected from multiple sites across Russia and Kazakhstan in 2016-2022. Species identification was performed by means of MALDI-TOF MS, with the Autobio and Bruker systems used in parallel. The PCR detection of the species-specific blaOXA-51-like gene was used as a means of differentiating A. baumannii from Anb species, and the partial sequencing of the rpoB gene was used as a reference method for Anb species identification. The susceptibility of isolates to antibiotics (amikacin, cefepime, ciprofloxacin, colistin, gentamicin, imipenem, meropenem, sulbactam, tigecycline, tobramycin, and trimethoprim-sulfamethoxazole) was determined using the broth microdilution method. The presence of the most common in Acinetobacter-acquired carbapenemase genes (blaOXA-23-like, blaOXA-24/40-like, blaOXA-58-like, blaNDM, blaIMP, and blaVIM) was assessed using real-time PCR.

RESULTS

In total, 234 isolates were identified as belonging to 14 Anb species. These comprised 6.2% of Acinetobacter spp. and 0.7% of all bacterial isolates from the observations. Among the Anb species, the most abundant were A. pittii (42.7%), A. nosocomialis (13.7%), the A. calcoaceticus/oleivorans group (9.0%), A. bereziniae (7.7%), and A. geminorum (6.0%). Notably, two environmental species, A. oleivorans and A. courvalinii, were found for the first time in the clinical samples of patients with urinary tract infections. The prevalence of resistance to different antibiotics in Anb species varied from <4% (meropenem and colistin) to 11.2% (gentamicin). Most isolates were susceptible to all antibiotics; however, sporadic isolates of A. bereziniae, A. johnsonii, A. nosocomialis, A. oleivorans, A. pittii, and A. ursingii were resistant to carbapenems. A. bereziniae was more frequently resistant to sulbactam, aminoglycosides, trimethoprim-sulfamethoxazole, and tigecycline than the other species. Four (1.7%) isolates of A. bereziniae, A. johnsonii, A. pittii were found to carry carbapenemase genes (blaOXA-58-like and blaNDM, either alone or in combination). The overall accuracy rates of the species-level identification of Anb isolates with the Autobio and Bruker systems were 80.8% and 88.5%, with misidentifications occurring in 5 and 3 species, respectively.

CONCLUSIONS

This study provides important new insights into the methods of identification, occurrence, species distribution, and antibiotic resistance traits of clinical Anb isolates.

Biological Preparation of Chitosan-Loaded Silver Nanoparticles: Study of Methylene Blue Adsorption as Well as Antibacterial Properties under Light

Human beings have made significant progress in the medical field since antibiotics were widely used. However, the consequences caused by antibiotics abuse have gradually shown their negative effects. Antibacterial photodynamic therapy (aPDT) has the ability to resist drug-resistant bacteria without antibiotics, and as it is increasingly recognized that nanoparticles can effectively solve the deficiency problem of singlet oxygen produced by photosensitizers, the application performance and scope of aPDT are gradually being expanded. In this study, we used a biological template method to reduce Ag⁺ to silver atoms in situ with bovine serum albumin (BSA) rich in various functional groups in a 50 °C water bath. The aggregation of nanomaterials was inhibited by the protein's multistage structure so that the formed nanomaterials have good dispersion and stability. It is unexpected that we used chitosan microspheres (CMs) loaded with silver nanoparticles (AgNPs) to adsorb methylene blue (MB), which is both a pollutant and photosensitive substance. The Langmuir adsorption isothermal curve was used to fit the adsorption capacity. The exceptional multi-bond angle chelating forceps of chitosan make it have a powerful physical adsorption capacity, and dehydrogenated functional groups of proteins with negative charge can also bond to positively charged MB to form a certain amount of ionic bonds. Compared with single bacteriostatic materials, the bacteriostatic capacity of the composite materials adsorbing MB under light was significantly improved. This composite material not only has a strong inhibitory effect on Gram-negative bacteria but also has a good inhibitory effect on the growth of Gram-positive bacteria poorly affected by conventional bacteriostatic agents. In conclusion, the CMs loaded with MB and AgNPs have some possible applications in the purification or treatment of wastewater in the future.

Impact of parabens on drinking water bacteria and their biofilms: The role of exposure time and substrate materials

Parabens have been detected in drinking water (DW) worldwide, however, their impact on DW microbial communities remains to be explored. Microorganisms can easily adapt to environmental changes. Therefore, their exposure to contaminants of emerging concern, particularly parabens, in DW distribution systems (DWDS) may affect the microbiological quality and safety of the DW reaching the consumers tap. This work provides a pioneer evaluation of the effects of methylparaben (MP), propylparaben (PP), butylparaben (BP), and their combination (MIX), in bacterial biofilms formed on different surfaces, representative of DWDS materials - high-density polyethylene (HDPE), polypropylene (PPL) and polyvinyl chloride (PVC). Acinetobacter calcoaceticus and Stenotrophomonas maltophilia, isolated from DW, were used to form single and dual-species biofilms on the surface materials selected. The exposure to MP for 7 days caused the most significant effects on biofilms, by increasing their cellular culturability, density, and thickness up to 233%, 150%, and 224%, respectively, in comparison to non-exposed biofilms. Overall, more pronounced alterations were detected for single biofilms than for dual-species biofilms when HDPE and PPL, demonstrating that the surface material used affected the action of parabens on biofilms. Swimming motility and the production of virulence factors (protease and gelatinase) by S. maltophilia were increased up to 141%, 41%, and 73%, respectively, when exposed to MP for 7 days. The overall results highlight the potential of parabens to interfere with DW bacteria in planktonic state and biofilms, and compromise the DW microbiological quality and safety.