Plasmid-Mediated Fluoroquinolone Resistance in Pseudomonas aeruginosa and Acinetobacter baumannii

Exploring fluoroquinolone resistance mechanisms and the effects of carbonyl cyanide 3-chlorophenylhydrazone (CCCP) in Acinetobacter baumannii

Objectives

This study aims to investigate the prevalence and mechanisms of fluoroquinolone resistance in Acinetobacter baumannii strains isolated from hospitals in Hamadan, west of Iran. It investigates the role of specific resistance genes and mutations in contributing to this resistance. In addition, the effects of carbonyl cyanide 3-chlorophenylhydrazone (CCCP) on the susceptibility of A. baumannii to fluoroquinolones will be evaluated to identify potential strategies to combat this growing problem.

Methods

A total of 102 A. baumannii isolates were collected from various clinical specimens between February and August 2023. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method according to CLSI guidelines, focusing on eight antibiotics, including ciprofloxacin and levofloxacin. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) evaluations were also performed for these fluoroquinolones. The presence of plasmid-dependent fluoroquinolone resistance (PMQR) genes and mutations in the gyrA and parC genes were assessed by PCR. The effect of CCCP on antibiotic susceptibility and expression of efflux pump encoding gene was evaluated by real-time PCR.

Results

The study revealed alarmingly high resistance rates among the 102 A. baumannii isolates, with 97% resistant to imipenem, 96% to gentamicin, 92% to ciprofloxacin, and 86% to levofloxacin. Of the isolates, 87 were classified as multidrug resistant (MDR). Several resistance genes were identified, including qnrS (77.45%), oqxA (73.52%), and qnrA (72.54%). Mutations in the gyrA and parC genes were detected in several isolates, contributing to the observed resistance. In addition, treatment with CCCP resulted in a significant reduction in MICs for both ciprofloxacin and levofloxacin, highlighting its potential role in mitigating resistance.

Conclusion

The findings underscore the urgent need for improved surveillance and treatment strategies due to the high prevalence of fluoroquinolone resistance. While CCCP demonstrated potential in restoring antibiotic susceptibility, further studies are needed to assess its clinical applicability and potential toxicity. Additionally, the study is limited by its focus on a single geographic region, and further investigations across broader populations are necessary to generalize these findings.

Prevalence of Plasmid-Mediated Fluoroquinolone Resistance Genes in Pseudomonas aeruginosa Among Patients at Aleppo University Hospital, Syria

BACKGROUND

Pseudomonas aeruginosa is a significant opportunistic pathogen, especially in hospital-acquired infections, with plasmid-mediated fluoroquinolone resistance posing a major healthcare threat. This research aimed to isolate fluoroquinolone-resistant P. aeruginosa from patients at Aleppo University Hospital, assess the prevalence of fluoroquinolone resistance, confirm molecular identity, identify plasmid-associated resistance genes, and investigate virulence factors.

METHODS

A total of 430 samples were collected from patients and cultured on selective media for identification. Molecular confirmation was achieved through PCR techniques. Various media were used to assess virulence factors and antibiotic resistance while also investigating the prevalence of resistance-related genes.

RESULTS

The study identified 29 fluoroquinolone-resistant P. aeruginosa isolates. These strains exhibited complete resistance to penicillins and all four generations of cephalosporins while remaining 100% sensitive to colistin. Notably, both hemolysin and gelatinase production rates were found to be 100%, and 48.2% of the isolates formed strong biofilms. The aac(6')-Ib gene was present in 72.4% of the isolates, the qnrS gene in 44.8%, and the qnrB gene in 13.7%. Additionally, 37.8% of the isolates contained two types of resistance genes, while 62% had one type. Importantly, all resistant isolates (100%) possessed at least four virulence factors.

CONCLUSION

The findings indicate a prevalence of plasmid-associated fluoroquinolone resistance genes in the studied isolates. It is recommended to rationalize fluoroquinolone use to preserve their effectiveness against multidrug-resistant strains.

The Evolution of Antimicrobial Resistance in Acinetobacter baumannii and New Strategies to Fight It

Acinetobacter baumannii is considered one of the prioritized ESKAPE microorganisms for the research and development of novel treatments by the World Health Organization, especially because of its remarkable persistence and drug resistance. In this review, we describe how this can be acquired by the enzymatic degradation of antibiotics, target site modification, altered membrane permeability, multidrug efflux pumps, and their ability to form biofilms. Also, the evolution of drug resistance in A. baumannii, which is mainly driven by mobile genetic elements, is reported, with particular reference to plasmid-associated resistance, resistance islands, and insertion sequences. Finally, an overview of existing, new, and alternative therapies is provided.

The mobilome landscape of biocide-resistance in Brazilian ESKAPE isolates

The increasing frequency of antibiotic-resistant bacteria is a constant threat to global human health. Therefore, the pathogens of the ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Enterobacter spp.) are among the most relevant causes of hospital infections responsible for millions of deaths every year. However, little has been explored about the danger of microorganisms resistant to biocides such as antiseptics and disinfectants. Widely used in domestic, industrial, and hospital environments, these substances reach the environment and can cause selective pressure for resistance genes and induce cross-resistance to antibiotics, further aggravating the problem. Therefore, it is necessary to use innovative and efficient strategies to monitor the spread of genes related to resistance to biocides. Whole genome sequencing and bioinformatics analysis aiming to search for sequences encoding resistance mechanisms are essential to help monitor and combat these pathogens. Thus, this work describes the construction of a bioinformatics tool that integrates different databases to identify gene sequences that may confer some resistance advantage about biocides. Furthermore, the tool analyzed all the genomes of Brazilian ESKAPE isolates deposited at NCBI and found a series of different genes related to resistance to benzalkonium chloride, chlorhexidine, and triclosan, which were the focus of this work. As a result, the presence of resistance genes was identified in different types of biological samples, environments, and hosts. Regarding mobile genetic elements (MGEs), around 52% of isolates containing genes related to resistance to these compounds had their genes identified in plasmids, and 48.7% in prophages. These data show that resistance to biocides can be a silent, underestimated danger spreading across different environments and, therefore, requires greater attention.

Antibiotic resistance in Pseudomonas aeruginosa: mechanisms and emerging treatment

Pseudomonas aeruginosa, able to survive on the surfaces of medical devices, is a life-threatening pathogen that mainly leads to nosocomial infection especially in immunodeficient and cystic fibrosis (CF) patients. The antibiotic resistance in P. aeruginosa has become a world-concerning problem, which results in reduced and ineffective therapy efficacy. Besides intrinsic properties to decrease the intracellular content and activity of antibiotics, P. aeruginosa develops acquired resistance by gene mutation and acquisition, as well as adaptive resistance under specific situations. With in-depth research on drug resistance mechanisms and the development of biotechnology, innovative strategies have emerged and yielded benefits such as screening for new antibiotics based on artificial intelligence technology, utilizing drugs synergistically, optimizing administration, and developing biological therapy. This review summarizes the recent advances in the mechanisms of antibiotic resistance and emerging treatments for combating resistance, aiming to provide a reference for the development of therapy against drug-resistant P. aeruginosa.

Occurrence of Plasmid-Mediated Quinolone Resistance and Carbapenemase-Encoding Genes in Pseudomonas aeruginosa Isolates from Nosocomial Patients in Aguascalientes, Mexico

Pseudomonas aeruginosa is a leading cause of healthcare-associated infections, which are related to substantial morbidity and mortality. The incidence of Plasmid-Mediated Quinolone Resistance (PMQR) determinants has been previously reported in this bacterium. However, there is limited information regarding the presence of PMQR and carbapenemase-encoding genes simultaneously. This study aims to analyze the prevalence of these determinants on P. aeruginosa strain isolated from clinical patients in the State of Aguascalientes, Mexico. Fifty-two P. aeruginosa isolates from nosocomial patients were collected from Centenario Hospital Miguel Hidalgo. This is a retrospective observational study conducted at a single center. Antibiotic susceptibility was tested using the Vitek-2 system. Only carbapenem-resistant isolates were included in this study. Carbapenemase-encoding genes and PMQR determinants were screened by polymerase chain reaction (PCR). Resistance rates of 100% were found on tigecycline and ceftriaxone. Of the 52 isolates, 34.6% were positive for the qnr genes, 46.2% for the oqxA gene, and 25% for the aac-(6')-lb gene. The most frequent carbapenemase genes found in the samples were blaOXA-51 (42.3%), blaOXA-1 (15.4%), and blaVIM (15.4%). blaOXA-51 co-carrying oqxA was detected in 21.1% of the isolates, blaOXA-51 co-carrying aac-(6')-lb in 11.5%, blaVIM co-carrying aac-(6')-lb in 3.8%, and blaKPC co-carrying oqxA in 5.8%. Systematic surveillance to detect carbapenemase-encoding genes and PMQR determinants, and rational prescription using the last-line drugs could help in preventing the dissemination of multidrug-resistant determinants.

Phenotypic and genotypic assessment of fluoroquinolones and aminoglycosides resistances in Pseudomonas aeruginosa collected from Minia hospitals, Egypt during COVID-19 pandemic

BACKGROUND

One of the most prevalent bacteria that cause nosocomial infections is Pseudomonas aeruginosa. Fluoroquinolones (FQ) and aminoglycosides are vital antipseudomonal drugs, but resistance is increasingly prevalent. The study sought to investigate the diverse mechanisms underlying FQ and aminoglycoside resistance in various P. aeruginosa strains particularly during the COVID-19 crisis.

METHODS

From various clinical and environmental samples, 110 P. aeruginosa isolates were identified and their susceptibility to several antibiotic classes was evaluated. Molecular techniques were used to track target gene mutations, the presence of genes encoding for quinolone resistance, modifying enzymes for aminoglycosides and resistance methyltransferase (RMT). Efflux pump role was assessed phenotypically and genotypically. Random amplified polymorphic DNA (RAPD) analysis was used to measure clonal diversity.

RESULTS

QnrS was the most frequently encountered quinolone resistance gene (37.5%) followed by qnrA (31.2%) and qnrD (25%). Among aminoglycoside resistant isolates, 94.1% harbored modifying enzymes genes, while RMT genes were found in 55.9% of isolates. The aac(6')-Ib and rmtB were the most prevalent genes (79.4% and 32.3%, respectively). Most FQ resistant isolates overexpressed mexA (87.5%). RAPD fingerprinting showed 63.2% polymorphism.

CONCLUSIONS

Aminoglycosides and FQ resistance observed in this study was attributed to several mechanisms with the potential for cross-contamination existence so, strict infection control practices are crucial.

Unveiling the microevolution of antimicrobial resistance in selected Pseudomonas aeruginosa isolates from Egyptian healthcare settings: A genomic approach

The incidence of Pseudomonas aeruginosa infections in healthcare environments, particularly in low-and middle-income countries, is on the rise. The purpose of this study was to provide comprehensive genomic insights into thirteen P. aeruginosa isolates obtained from Egyptian healthcare settings. Phenotypic analysis of the antimicrobial resistance profile and biofilm formation were performed using minimum inhibitory concentration and microtiter plate assay, respectively. Whole genome sequencing was employed to identify sequence typing, resistome, virulome, and mobile genetic elements. Our findings indicate that 92.3% of the isolates were classified as extensively drug-resistant, with 53.85% of these demonstrating strong biofilm production capabilities. The predominant clone observed in the study was ST773, followed by ST235, both of which were associated with the O11 serotype. Core genome multi-locus sequence typing comparison of these clones with global isolates suggested their potential global expansion and adaptation. A significant portion of the isolates harbored Col plasmids and various MGEs, all of which were linked to antimicrobial resistance genes. Single nucleotide polymorphisms in different genes were associated with the development of antimicrobial resistance in these isolates. In conclusion, this pilot study underscores the prevalence of extensively drug-resistant P. aeruginosa isolates and emphasizes the role of horizontal gene transfer facilitated by a diverse array of mobile genetic elements within various clones. Furthermore, specific insertion sequences and mutations were found to be associated with antibiotic resistance.

Coexistence of plasmid-mediated quinolone resistance (PMQR) and extended-spectrum beta-lactamase (ESBL) genes among clinical Pseudomonas aeruginosa isolates in Egypt

BACKGROUND

Data about the prevalence of plasmid-mediated quinolone resistance (PMQR) and extended-spectrum beta-lactamase (ESBL) production in P. aeruginosa compared to the Enterobacteriaceae family is limited. The availability of limited therapeutic options raises alarming concerns about the treatment of multidrug-resistant P. aeruginosa. This study aimed to assess the presence of PMQR and ESBL genes among P. aeruginosa strains.

METHODS

Fifty-six P. aeruginosa strains were isolated from 330 patients with different clinical infections. Phenotypically fluoroquinolone-resistant isolates were tested by PCR for the presence of six PMQR genes. Then, blaTEM, blaSHV, and blaCTX-M type ESBL genes were screened to study the co-existence of different resistance determinants.

RESULTS

Overall, 22/56 (39.3%) of the studied P. aeruginosa isolates were phenotypically resistant to fluoroquinolones. PMQR-producing P. aeruginosa isolates were identified in 20 isolates (90.9%). The acc(6')-Ib-cr was the most prevalent PMQR gene (77.3%). The qnr genes occurred in 72.7%, with the predominance of the qnrA gene at 54.5%, followed by the qnrS gene at 27.3%, then qnrB and qnrC at 22.7%. The qepA was not detected in any isolate. The acc(6')-Ib-cr was associated with qnr genes in 65% of positive PMQR isolates. Significant differences between the fluoroquinolone-resistant and fluoroquinolone-susceptible isolates in terms of the antibiotic resistance rates of amikacin, imipenem, and cefepime (P value < 0.0001) were found. The ESBL genes were detected in 52% of cephalosporin-resistant P. aeruginosa isolates. The most frequent ESBL gene was blaCTX-M (76.9%), followed by blaTEM (46.2%). No isolates carried the blaSHV gene. The acc(6')-Ib-cr gene showed the highest association with ESBL genes, followed by the qnrA gene. The correlation matrix of the detected PMQR and ESBL genes indicated overall positive correlations. The strongest and most highly significant correlation was between qnrA and acc(6')-Ib-cr (r = 0.602) and between qnrA and blaCTX-M (r = 0.519).

CONCLUSION

A high prevalence of PMQR genes among the phenotypic fluoroquinolone-resistant P. aeruginosa isolates was detected, with the co-carriage of different PMQR genes. The most frequent PMQR was the acc(6')-Ib-cr gene. Co-existence between PMQR and ESBL genes was found, with 75% of PMQR-positive isolates carrying at least one ESBL gene. A high and significant correlation between the ESBL and PMQR genes was detected.

Ciprofloxacin- and levofloxacin-loaded nanoparticles efficiently suppressed fluoroquinolone resistance and biofilm formation in Acinetobacter baumannii

The spread of fluoroquinolone (FQ) resistance in Acinetobacter baumannii represents a critical health threat. This study aims to overcome FQ resistance in A. baumannii via the formulation of polymeric nanoFQs. Herein, 80 A. baumannii isolates were obtained from diverse clinical sources. All A. baumannii isolates showed high resistance to most of the investigated antimicrobials, including ciprofloxacin (CIP) and levofloxacin (LEV) (97.5%). FQ resistance-determining regions of the gyrA and parC genes were the most predominant resistant mechanism, harbored by 69 (86.3%) and 75 (93.8%) of the isolates, respectively. Additionally, plasmid-mediated quinolone resistance genes aac(6')-Ib and qnrS were detected in 61 (76.3%) and 2 (2.5%) of the 80 isolates, respectively. The CIP- and LEV-loaded poly ε-caprolactone (PCL) nanoparticles, FCIP and FLEV, respectively, showed a 1.5-6- and 6-12-fold decrease in the MIC, respectively, against the tested isolates. Interestingly, the time kill assay demonstrated that MICs of FCIP and FLEV completely killed A. baumannii isolates after 5-6 h of treatment. Furthermore, FCIP and FLEV were found to be efficient in overcoming the FQ resistance mediated by the efflux pumps in A. baumannii isolates as revealed by decreasing the MIC four-fold lower than that of free CIP and LEV, respectively. Moreover, FCIP and FLEV at 1/2 and 1/4 MIC significantly decreased biofilm formation by 47-93% and 69-91%, respectively. These findings suggest that polymeric nanoparticles can restore the effectiveness of FQs and represent a paradigm shift in the fight against A. baumannii isolates.

How to treat severe Acinetobacter baumannii infections

PURPOSE OF REVIEW

To update the management of severe Acinetobacter baumannii infections (ABI), particularly those caused by multi-resistant isolates.

RECENT FINDINGS

The in vitro activity of the various antimicrobial agents potentially helpful in treating ABI is highly variable and has progressively decreased for many of them, limiting current therapeutic options. The combination of more than one drug is still advisable in most circumstances. Ideally, two active first-line drugs should be used. Alternatively, a first-line and a second-line drug and, if this is not possible, two or more second-line drugs in combination. The emergence of new agents such as Cefiderocol, the combination of Sulbactam and Durlobactam, and the new Tetracyclines offer therapeutic options that need to be supported by clinical evidence.

SUMMARY

The apparent limitations in treating infections caused by this bacterium, the rapid development of resistance, and the serious underlying situation in most cases invite the search for alternatives to antibiotic treatment, the most promising of which seems to be bacteriophage therapy.

Comparison of loop-mediated isothermal amplification, multiplex PCR, and REP- PCR techniques for identification of carbapenem-resistant Acinetobacter baumannii clinical isolates

Background and Objectives

Acinetobacter baumannii, an opportunistic pathogen, is related to hospital-acquired infections and increased mortality. This study aimed to develop the loop-mediated isothermal amplification (LAMP) test for the fast-detecting of A. baumannii isolates as well as determining genetic relatedness for these isolates via the REP-PCR technique.

Materials and Methods

LAMP primers and multiplex PCR primers were designed for recognizing A. baumannii isolates harboring the bla SHV-1 , bla PER-1 , bla TEM-1, AMPC, qnr, and aac (6)-1 genes, were collected (October 2020 to February 2021) from Shahid Motahari Hospital, Tehran, Iran. Combination disc test (CDT) results were used to assess the phenotypic identification of isolates from ESBL producers. The sensitivity of the LAMP method was evaluated using a range of serial dilutions of genomic DNA. Results were compared between the LAMP technique, and multiplex PCR. The genetic diversity of clinical isolates was determined by REP-PCR.

Results

Among one hundred A. baumannii samples and based on the combined disc test, 56% of isolates were ESBL producers. The sensitivity of the LAMP technique for the identification of A. baumannii was 4.06 ng/μl whilst the multiplex PCR was (16.2 ng/μl). Regarding multiplex PCR, (68%) of the isolates were bla SHV-1 positive, (40%) bla PER-1, (85%) aac (6')-1, AMPC (67%), bla TEM-1 (63%), and (15%) qnr respectively. While in LAMP, (69%) of isolates were bla SHV-1 positive, (86%) aac (6')-1, and (20%) qnr. The results of AMPC, bla TEM-1 , and bla PER-1 genes showed 100% compatibility between multiplex PCR and LAMP assays. The results of REP-PCR indicated there were 17 clones, clone A at 14% was the most prevalent of the isolates.

Conclusion

Wherever equipment and financial constraints are crucial, the LAMP test offers a better and more potent detection rate for the identification of A. baumannii isolates than multiplex PCR. Furthermore, the genetic diversity of A. baumannii in these clinical isolates showed frequent commonality of genotypes.

Acinetobacter baumannii in the critically ill: complex infections get complicated

Acinetobacter baumannii is increasingly associated with various epidemics, representing a serious concern due to the broad level of antimicrobial resistance and clinical manifestations. During the last decades, A. baumannii has emerged as a major pathogen in vulnerable and critically ill patients. Bacteremia, pneumonia, urinary tract, and skin and soft tissue infections are the most common presentations of A. baumannii, with attributable mortality rates approaching 35%. Carbapenems have been considered the first choice to treat A. baumannii infections. However, due to the widespread prevalence of carbapenem-resistant A. baumannii (CRAB), colistin represents the main therapeutic option, while the role of the new siderophore cephalosporin cefiderocol still needs to be ascertained. Furthermore, high clinical failure rates have been reported for colistin monotherapy when used to treat CRAB infections. Thus, the most effective antibiotic combination remains disputed. In addition to its ability to develop antibiotic resistance, A. baumannii is also known to form biofilm on medical devices, including central venous catheters or endotracheal tubes. Thus, the worrisome spread of biofilm-producing strains in multidrug-resistant populations of A. baumannii poses a significant treatment challenge. This review provides an updated account of antimicrobial resistance patterns and biofilm-mediated tolerance in A. baumannii infections with a special focus on fragile and critically ill patients.