Determination of Acquired Resistance Profiles of Pseudomonas aeruginosa Isolates and Characterization of an Effective Bacteriocin-Like Inhibitory Substance (BLIS) Against These Isolates

Assessment of bacteriocin production by clinical Pseudomonas aeruginosa isolates and their potential as therapeutic agents

INTRODUCTION

Bacterial infections and the rising antimicrobial resistance pose a significant threat to public health. Pseudomonas aeruginosa produces bacteriocins like pyocins, especially S-type pyocins, which are promising for biological applications. This research focuses on clinical P. aeruginosa isolates to assess their bacteriocin production, inhibitory spectrum, chemical structure, antibacterial agents, and preservative potential.

METHODS

The identification of P. aeruginosa was conducted through both phenotypic and molecular approaches. The inhibitory spectrum and antibacterial potential of the isolates were assessed. The kinetics of antibacterial peptide production were investigated, and the activity of bacteriocin was quantified in arbitrary units (AU ml-1). Physico-chemical characterization of the antibacterial peptides was performed. Molecular weight estimation was carried out using SDS-PAGE. qRT-PCR analysis was employed to validate the expression of the selected candidate gene.

RESULT

The antibacterial activity of P. aeruginosa was attributed to the secretion of bacteriocin compounds, which belong to the S-type pyocin family. The use of mitomycin C led to a significant 65.74% increase in pyocin production by these isolates. These S-type pyocins exhibited the ability to inhibit the growth of both Gram-negative (P. mirabilis and P. vulgaris) and Gram-positive (S. aureus, S. epidermidis, E. hirae, S. pyogenes, and S. mutans) bacteria. The molecular weight of S-type pyocin was 66 kDa, and its gene expression was confirmed through qRT-PCR.

CONCLUSION

These findings suggest that S-type pyocin hold significant potential as therapeutic agents against pathogenic strains. The Physico-chemical resistance of S-type pyocin underscores its potential for broad applications in the pharmaceutical, hygiene, and food industries.

Does Conjugation of Silver Nanoparticles with Thiosemicarbazide Increase Their Antibacterial Properties?

The opportunistic pathogen, Pseudomonas aeruginosa, uses different mechanisms as well as biofilm production to acquire antibiotic resistance. The polysaccharide synthesis locus (psl) genes play an important role in P. aeruginosa biofilm formation. Therefore, targeting the expression of psl genes can be a suitable strategy to prevent the formation of biofilms by antibiotic-resistant strains. Today, advances in nanotechnology provide a novel potential strategy to combat antibiotic-resistant bacteria. In this study, the silver nanoparticles (Ag NPs) synthesized using a chemical co-precipitation method and, after conjugation with thiosemicarbazide, their effect on the biofilm-forming ability are studied in P. aeruginosa isolates. Chemical properties of synthesized nanoparticles were determined by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy, ultraviolet-visible spectroscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy. The results confirmed the spherical/cubic morphology, solution stability, and good dispersion of Ag@Glu-TSC NPs with an average size of 40-60 nm. In addition, minimum inhibitory concentration values of functionalized Ag NPs were at least twofold lower than the Ag NPs (alone). The quantitative PCR data analysis showed a decrease in the expression of the pslA gene in the presence of Ag@Glu-TSC NPs, up to 60%, which was associated with a reduction of biofilm formation compared to control. In conclusion, the Ag@Glu-TSC NPs can be considered a new inhibitor of biofilm production in antibiotic-resistant bacteria.

Pandrug-resistant Gram-negative bacteria: a systematic review of current epidemiology, prognosis and treatment options

BACKGROUND

The literature on the epidemiology, mortality and treatment of pandrug-resistant (PDR) Gram-negative bacteria (GNB) is scarce, scattered and controversial.

OBJECTIVES

To consolidate the relevant literature and identify treatment options for PDR GNB infections.

METHODS

A systematic search in MEDLINE, Scopus and clinical trial registries was conducted. Studies reporting PDR clinical isolates were eligible for review if susceptibility testing for all major antimicrobials had been performed. Characteristics and findings of retrieved studies were qualitatively synthesized.

RESULTS

Of 81 studies reviewed, 47 (58%) were published in the last 5 years. The reports reflected a worldwide dissemination of PDR GNB in 25 countries in 5 continents. Of 526 PDR isolates reported, Pseudomonas aeruginosa (n=175), Acinetobacter baumannii (n=172) and Klebsiella pneumoniae (n=125) were most common. PDR GNB were typically isolated in ICUs, but several studies demonstrated wider outbreak potential, including dissemination to long-term care facilities and international spread. All-cause mortality was high (range 20%-71%), but appeared to be substantially reduced in studies reporting treatment regimens active in vitro. No controlled trial has been performed to date, but several case reports and series noted successful use of various regimens, predominantly synergistic combinations, and in selected patients increased exposure regimens and newer antibiotics.

CONCLUSIONS

PDR GNB are increasingly being reported worldwide and are associated with high mortality. Several treatment regimens have been successfully used, of which synergistic combinations appear to be most promising and often the only available option. More pharmacokinetic/pharmacodynamic and outcome studies are needed to guide the use of synergistic combinations.

Antimicrobial resistance patterns of Pseudomonas aeruginosa isolated from canine clinical cases at a veterinary academic hospital in South Africa

Although Pseudomonas aeruginosa (P. aeruginosa) can infect both animals and humans, there is a paucity of veterinary studies on antimicrobial resistance of P. aeruginosa in South Africa. Secondary data of canine clinical cases presented at the hospital from January 2007 to December 2013 was used. The following information was recorded: type of sample, the date of sampling and the antimicrobial susceptibility results. Frequencies, proportions and their 95% confidence intervals were calculated for all the categorical variables. In total, 155 P. aeruginosa isolates were identified and included in this study. All the isolates were resistant to at least one antimicrobial (AMR), while 92% were multi-drug resistant (MDR). Most isolates were resistant to lincomycin (98%), penicillin-G (96%), orbifloxacin (90%), trimethoprim-sulfamethoxazole (90%) and doxycycline (87%). A low proportion of isolates was resistant to imipenem (6%), tobramycin (12%), amikacin (16%) and gentamicin (18%). A high proportion of MDR-P. aeruginosa isolates was resistant to amoxycillin-clavulanic acid (99%), tylosin (99%), chloramphenicol (97%) and doxycycline (96%). Few (6%) of MDR-P. aeruginosa isolates were resistant to imipenem. Pseudomonas aeruginosa was associated with infections of various organ systems in this study. All P. aeruginosa isolates of P. aeruginosa exhibited resistance to β-lactams, fluoroquinolones and lincosamides. Clinicians at the hospital in question should consider these findings when treating infections associated with P. aeruginosa.

Investigation of the prevalence of genes conferring resistance to carbapenems in Pseudomonas aeruginosa isolates from burn patients

Background and aim: Currently, the rate of hospital-acquired infections due to drug-resistant Pseudomonas aeruginosa strains shows an increasing trend and remains one of the principal reasons for mortalilty in burn patients. This study aimed to investigate the prevalence of genes conferring resistance to carbapenems in P. aeruginosa isolates from burn patients. Methods: A total of 50 P. aeruginosa isolates were tested for antibiotic susceptibility and presence of multidrug-resistant (MDR) and extensively drug resistant (XDR) isolates, using phenotypic tests. Screening for genes conferring resistance to carbapenems was investigated by multiplex PCR method. Results: Susceptibility testing demonstrated the highest resistance against amikacin, ceftazidime (n=44/88% each), and gentamicin (84%), while colistin sulfate was the most effective antibiotic. The rate of MDR and XDR isolates was revealed as 50% and 40% respectively. We detected the following carbapenemase genes: blaNDM (32%), followed by blaOXA-48 (18%), and blaBIC-1 (14%). This study revealed a high antibiotic resistance in P. aeruginosa isolates with a total of 40% and 50% MDR and XDR isolates respectively, and 70% carbapenem resistance. The prevalence of carbapenem conferring genes tested among carbapenem-resistant isolates was demonstrated as 65.7%. Conclusion: Due to the prevalence of P. aeroginosa strains carrying blaOXA-48 and blaNDM genes in our hospital, more attention and implementation of effective control measures against nosocomial infection are recommended.