Prevalence of ESBL-producing Pseudomonas aeruginosa isolates in Warsaw, Poland, detected by various phenotypic and genotypic methods

Detection of Extended-Spectrum β-Lactamases, Metallo-β-Lactamases, Antimicrobial Resistance Profiles, and Biofilm-Forming Capacity in Pseudomonas aeruginosa Strains Recovered From Dogs With Otitis Externa in Italy

Pseudomonas aeruginosa is considered the second major causative agent of otitis externa in dogs, after Staphylococcus pseudintermedius. This study aimed to evaluate the antimicrobial resistance profiles and to detect the extended-spectrum β-lactamase (ESBL) and metallo-β-lactamase (MBL) genes in Pseudomonas aeruginosa (P. aeruginosa). Precisely, seventeen P. aeruginosa strains, recovered from auricular specimens of dogs affected by otitis externa, were identified by MALDI-TOF MS. Antimicrobial susceptibility testing was carried out against eleven clinically relevant antimicrobials using the Kirby Bauer disk diffusion method on Mueller Hinton agar plates. The PCR assay was performed to detect ESBL bla CTX-M ,  bla TEM ,  bla SHV ,  bla PER , and MBL bla IMP ,  bla OXA-48,  bla VIM ,  bla NDM ,  bla GES genes. The results showed that P. aeruginosa isolates had a phenotypic resistance value of 100% to ceftazidime, imipenem, and meropenem, followed by piperacillin-tazobactam, sulfamethoxazole-trimethoprim (94%), and aztreonam (88%). An alarming result was represented by the high prevalence of multidrug-resistant strains with 100% of the total isolates. The most common ESBL-genotype combination was bla PER  + bla SHV (29.4%). Thirteen isolates (76.5%) carried together bla VIM  + bla GES genes, which resulted to be the most common MBL-genotype combination. All the isolates harboring ESBL and MBL genes were biofilm producers, evaluated by the crystal violet-based assay and PCR. Precisely, 76.5% were strong biofilm producers, and 23.5% resulted in being moderate producers. No relationship was observed between strong or moderate biofilm producers and numerical variability of ESBL and MBL genes. This study revealed worrying antimicrobial resistance profiles of P. aeruginosa-associated canine otitis externa, considering also the zoonotic potential of this pathogen.

Diagnostic algorithm for the detection of carbapenemases and extended-spectrum β-lactamases in carbapenem-resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa can acquire carbapenem resistance through various mechanisms, including genomic mutations leading to the overexpression of efflux pumps, intrinsic AmpC-β-lactamase, and/or reduced permeability, and/or through the acquisition of plasmid-mediated carbapenemases and/or extended-spectrum-β-lactamases (ESBLs). Unfortunately, carbapenemase/ESBL-producing-carbapenem-resistant-P. aeruginosa (CP/ESBL-CRPA) cannot be differentiated from non-CP/ESBL-CRPA based solely on susceptibility testing results of conventional β-lactam (BL)-antibiotics. Knowing that these two groups display different activity profiles toward novel BL/β-lactamase-inhibitor (BLI) combinations, we developed and verified a cost-effective and easy-to-use diagnostic algorithm for screening and differentiation of carbapenemase and ESBL production in CRPA. We determined disc diffusion inhibition zones and gradient strip minimal inhibitory concentration values of 136 whole-genome-sequenced CRPA (70 metallo-β-lactamase-[MBL-], 1 GES-5-, 1 KPC-2-, 12 ESBL-, and 53 AmpC-hyper-producing isolates). We used the following BL-BLI combinations: ceftolozane-tazobactam (C-T), ceftazidime-avibactam, imipenem-relebactam (I-R), meropenem-vaborbactam, cefepime-enmetazobactam (C-E), and aztreonam-avibactam. We also included a lateral flow immunoassay (Carba-5, NG-Biotech) for confirmation of MBL production and double disc synergy testing (DDST) to improve ESBL detection. C-T was the most effective screening antibiotic for distinguishing MBL and ESBL producers from AmpC-hyperproducing CRPA, achieving a sensitivity of 100% for both MBL and ESBL producers. I-R reliably confirmed MBL production in C-T positive screened CRPAs, with a sensitivity of 92.8% and specificity of 100%. Incorporating Carba-5 into the phenotypic algorithm improved sensitivity for confirming MBL production to 100%. For the remaining C-T positive but I-R negative isolates, C-E showed 75% sensitivity and 78.6% specificity in detecting ESBL production. The DDST further confirmed ESBL production in six out of nine ESBL producers (66.6%). In conclusion, we established a simple and cost-effective diagnostic algorithm, enabling screening and confirmation of carbapenemase and ESBL production in CRPA.IMPORTANCECarbapenem-resistant Pseudomonas aeruginosa (CRPA) is a major global health threat, and rapid identification of its resistance mechanisms is crucial for effective treatment and infection control. Differentiating between carbapenemase-producing (CP), extended-spectrum β-lactamase-producing (ESBL), and AmpC-hyperproducing CRPA is challenging, as conventional susceptibility testing cannot reliably distinguish these resistance mechanisms. Our study presents a simple, cost-effective, and easy-to-implement phenotypic diagnostic algorithm that enables accurate screening and confirmation of CP and ESBL production in CRPA. This method is particularly valuable for laboratories lacking access to molecular diagnostics, as it provides a practical alternative for routine testing. By facilitating the early detection of resistant P. aeruginosa strains, this approach has the potential to improve patient outcomes, optimize antimicrobial therapy, and enhance global surveillance efforts against multidrug-resistant pathogens.

Activity of cefiderocol on extensively drug-resistant Pseudomonas aeruginosa from burn wound infections in Mansoura, Egypt

Background and Objectives

Increased Pseudomonas aeruginosa antibiotic resistance limits treatment options and is associated with a higher level of mortality and mordacity. The purpose of this research was to identify class 1 and 2 integrons, carbapenemase, SHV, and TEM genes in extensively drug-resistant (XDR) P. aeruginosa isolated from infected burns and evaluate their in vitro cefiderocol activity.

Materials and Methods

By using the disc diffusion method, the antimicrobial susceptibility of 110 P. aeruginosa isolates collected from infected burns were evaluated. XDR P. aeruginosa were screened phenotypically for carbapenemase and extended spectrum β-lactamases (ESBLs) production. Both MIC Test Strip and disc diffusion were employed to test the cefiderocol susceptibility. PCR was used to assess carbapenemase, SHV and TEM genes and integrons class 1 and 2.

Results

From the 110 P. aeruginosa, 54 isolates (49%) were XDR. TEM gene was detected in 35 isolates. Among XDR isolates, carbapenemase genes were detected in 31.5%, with NDM being predominant Thirty XDR isolates had class1 integrons. All isolates were sensitive to cefiderocol and its MIC50/MIC90 was 0.5/1.5mg/L (range 0.064-1.5mg/L).

Conclusion

Nearly half the P. aeruginosa isolates from burn infections were extensively drug-resistant. Cefiderocol's in vitro activity demonstrated that it is a promising therapy alternative for treating extensively drug-resistant P. aeruginosa in burn patients.

Phenotypic and molecular characterization of extended spectrum- and metallo- beta lactamase producing Pseudomonas aeruginosa clinical isolates from Egypt

BACKGROUND

Antimicrobial resistance among Pseudomonas aeruginosa (P. aeruginosa), a leading cause of nosocomial infections worldwide, is escalating. This study investigated the prevalence of extended-spectrum β-lactamases (ESBLs) and metallo-β-lactamases (MBLs) among 104 P. aeruginosa clinical isolates from Alexandria Main University Hospital, Alexandria, Egypt.

METHODS

Antimicrobial susceptibility testing was performed using agar dilution technique, or broth microdilution method in case of colistin. ESBL and MBL prevalence was assessed phenotypically and genotypically using polymerase chain reaction (PCR). The role of plasmids in mediating resistance to extended-spectrum β-lactams was studied via transformation technique using plasmids isolated from ceftazidime-resistant isolates.

RESULTS

Antimicrobial susceptibility testing revealed alarming resistance rates to carbapenems, cephalosporins, and fluoroquinolones. Using PCR as the gold standard, phenotypic methods underestimated ESBL production while overestimating MBL production. Eighty-five isolates (81.7%) possessed only ESBL encoding genes, among which 69 isolates harbored a single ESBL gene [blaOXA-10 (n = 67) and blaPER (n = 2)]. Four ESBL-genotype combinations were detected: blaPER + blaOXA-10 (n = 8), blaVEB-1 + blaOXA-10 (n = 6), blaPSE + blaOXA-10 (n = 1), and blaPER + blaVEB-1 + blaOXA-10 (n = 1). Three isolates (2.9%) possessed only the MBL encoding gene blaVIM. Three ESBL + MBL- genotype combinations: blaOXA-10 + blaAIM, blaOXA-10 + blaVIM, and blaPER + blaOXA-10 + blaAIM were detected in 2, 1 and 1 isolate(s), respectively. Five plasmid preparations harboring blaVEB-1 and blaOXA-10 were successfully transformed into chemically competent Escherichia coli DH5α with transformation efficiencies ranging between 6.8 × 10 3 and 3.7 × 10 4    CFU/μg DNA plasmid. Selected tested transformants were ceftazidime-resistant and harbored plasmids carrying blaOXA-10.

CONCLUSIONS

The study highlights the importance of the expeditious characterization of ESBLs and MBLs using genotypic methods among P. aeruginosa clinical isolates to hinder the development and dissemination of multidrug resistant strains.

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.

Multidrug Resistant Pseudomonas aeruginosa in Clinical Settings: A Review of Resistance Mechanisms and Treatment Strategies

Pseudomonas aeruginosa is causing increasing concern among clinicians due to its high mortality and resistance rates. This bacterium is responsible for various infections, especially in hospital settings, affecting some of the most vulnerable patients. Pseudomonas aeruginosa has developed resistance through multiple mechanisms, making treatment challenging. Diagnostic techniques are evolving, with rapid testing systems providing results within 4-6 h. New antimicrobial agents are continuously being developed, offering potential solutions to these complex clinical decisions. This article provides a review of the epidemiology, at-risk populations, resistance mechanisms, and diagnostic and treatment options for Pseudomonas aeruginosa.

Mechanisms leading to in vivo ceftazidime/avibactam resistance development during treatment of GES-5-producing Pseudomonas aeruginosa infections

The mechanisms underlying ceftazidime/avibactam resistance development in four ceftazidime/avibactam susceptible/resistant pairs of GES-5-producing ST235 Pseudomonas aeruginosa clinical isolates were investigated. In three of the cases, ceftazidime/avibactam resistance was driven by a single mutation leading to GES-27 (P162Q), GES-29 (P162A), or the novel GES-60 (N136S), as confirmed through cloning experiments. Moreover, these mutations were associated with increased cefiderocol MICs but reduced carbapenem, particularly imipenem/relebactam, resistance. Understanding the complexity of resistance mechanisms to the growing repertoire of antipseudomonal β-lactams is crucial to guide optimized treatments and antimicrobial stewardship measures.

Genomic Insights into Vietnamese Extended-Spectrum β-Lactamase-9-Producing Extensively Drug-Resistant Pseudomonas aeruginosa Isolates Belonging to the High-Risk Clone ST357 Obtained from Bulgarian Intensive Care Unit Patients

Extensively drug-resistant P. aeruginosa (XDR-PA) has been highlighted as a serious public health threat. The present study aimed to explore the genomic characteristics of two Vietnamese extended-spectrum β-lactamase-9 (VEB-9)-producing XDR-PA isolates from Bulgaria in comparison to all blaVEB-9-positive strains with available genomes. The isolates designated Pae51 and Pae52 were obtained from tracheobronchial aspirates of intensive care unit (ICU) patients. Antimicrobial susceptibility testing, whole-genome sequencing, RT-qPCR, and phylogenomic analysis were performed. Pae51 and Pae52 were resistant to most antipseudomonal β-lactams including carbapenems, aminoglycosides, and fluoroquinolones but remained susceptible to colistin and cefiderocol. Numerous resistance determinants were detected: blaVEB-9, blaPDC-3, blaOXA-10, blaOXA-50, aac(6')-II, ant(2″)-Ia, ant(3″)-IIa, aph(3')-IIb, cprP, catB7, dfrB2, sul1, fosA, and tet(A). Both isolates carried complex integrons with blaVEB-9 and tet(A) embedded next to the conservative 3' end sequences. A variety of virulence factors were also identified, including the type III secretion system exotoxin U. Pae51 and Pae52 differed by only four SNPs and belonged to the high-risk clone ST357. To our knowledge, this is the first report of blaVEB-9-positive XDR-PA isolates in Bulgaria presenting a detailed genomic analysis. The development of novel antimicrobial strategies for such pathogens should be an essential part of infection control stewardship practices in ICU wards.

Complete genome sequence of carbapenem-resistant pathogenic Klebsiella aerogenes strain CH7 isolated from vermicompost

We announce the complete genome of Klebsiella aerogenes strain CH7, isolated from a vermicompost sample. A total of 9.14131 million high-quality reads comprised 96 contigs with 5,273 genes and 5,038 protein-coding genes.

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.

Antibiotic resistance among Aerobic Gram-Negative Bacilli isolated from patients with oral inflammatory dysbiotic conditions-a retrospective study

Introduction

Aerobic gram-negative bacilli (AGNB) are not part of the resident oral microflora but are occasionally found in high abundance under inflammatory dysbiotic conditions at various oral niches. The aim of the present study was to investigate the identity and antibiotic susceptibility of AGNB isolated from patients in Sweden with mucosal lesions, periodontitis, and peri-implantitis, with special attention to antibiotic resistance and on the presence of phenotypic Extended Spectrum Beta-Lactamase (ESBL) isolates.

Materials and methods

Microbiolgical samples were harvested from 211 patients in total, experiencing mucosal lesions (N = 113), periodontitis (N = 62), or peri-implantitis (N = 36). The growth of AGNBs was semiquantified by selective and non-selective culture and the strains were isolated, identified, and tested for antibiotic susceptibility. A total of 251 AGNB strains, occurring in moderate to heavy growth (>100 CFU/ml sample), indicating a dysbiotic microbiota, were identified. The disc diffusion method was used for screening of the antibiotic susceptibility of the isolates. Phenotypic identification of ESBL isolates was based on resistance to ceftazidime and/or cefotaxime.

Results

The most commonly detected AGNB isolates in oral inflammatory dysbiotic conditions were fermentative species belonging to Enterobacteriaceae e.g. Citrobacter spp., Enterobacter spp., Escherichia coli, Klebsiella spp, and the non-fermentative environmental Burkholderia cepacia, Pseudomonas spp., and Stenotrophomonas maltophilia. No clear trends were seen in frequency of the various species in samples from mucosal lesions, severe periodontitis, and peri-implantitis cases. The 138 Enterobacteriaceae isolates and 113 environmental AGNB isolated showed a high antibiotic resistance in general against antibiotics commonly used in dentistry (Amoxicillin, Amoxicillin + Clavulanic acid, Ampicillin, Clindamycin, Doxycycline, Erythromycin, Oxacillin, PenicillinV, and Tetracycline). The majority of these isolates were susceptible to ciprofloxacin. Ten isolates (4.1%) were phenotypically classified as ESBL positive. The ESBL isolates were predominantly found among isolates of S. maltophilia, while only one ESBL positive isolate was found among Enterobacteriaceae.

Conclusions

Phenotypically identified ESBL isolates can occasionally be present among oral AGNB strains isolated in abundance from the dysbiotic microbiota occurring in cases with oral mucosal lesions, severe periodontitis, or peri-implantitis.

Intravenous Fosfomycin for Systemic Multidrug-Resistant Pseudomonas aeruginosa Infections

Human Pseudomonas infections have high morbidity and mortality rates. Pseudomonas bacteria can cause sepsis or septic shock; they produce biofilm and commonly exhibit a multidrug-resistant phenotype. The choice of antimicrobial therapy in many cases is challenging, and deep knowledge of clinical, microbiological, and pharmacological issues is required. Intravenous fosfomycin is being repurposed in a combination given its favorable pharmacokinetic/pharmacodynamic properties (a small molecule with favorable kinetic both in bloodstream infection and in deep-seated infections), antibiofilm activity, and its interesting synergistic effects with other antimicrobials. Recent literature on epidemiological, microbiological, pharmacological, and clinical data on intravenous fosfomycin therapy against Pseudomonas is herein reviewed and discussed.

Antibiotic resistance and genetic diversity among Pseudomonas aeruginosa isolated from urinary tract infections in Iran

Aims: To determine the antibiotic resistance and genetic diversity of Pseudomonas aeruginosa isolates. Methods: The antibiotic resistance, genetic diversity and the conjugate transformation among Pseudomonas aeruginosa collected from patients with urinary tract infection in Tehran, Iran, was investigated. Results: Antibiotic resistance against cefepime was seen in 51.74% of the isolates, followed by amikacin (47.76%). blaOXA-10 and blaVIM were the most prevalent extended-spectrum β-lactamase and metallo-β-lactamases genes, respectively. Five clusters (C1-C5) were obtained by pulse field gel electrophoresis and multilocus sequence typing revealed two strain types, ST235 and ST664. Conjugation detected blaOXA-48 and blaNDM genes were transferred to Escherichia coli K12. Conclusion: The resistance of P. aeruginosa to antibiotics is increasing, which highlights the need to determine the resistance patterns to design better treatment strategies.

Evolving landscape of carbapenem-resistant Pseudomonas aeruginosa at a single centre in the USA

Objectives

The increased identification of carbapenem-resistant Pseudomonas aeruginosa (CR-PA) is an ongoing concern. However, information on the evolving antimicrobial resistance profile and molecular epidemiology of CR-PA over time is scarce. Thus, we conducted a cross-sectional analysis to investigate the phenotypic and genotypic characteristics of CR-PA recovered over different time periods, focusing on the isolates exhibiting a ceftolozane/tazobactam resistance phenotype.

Methods

A total of 169 CR-PA isolated from clinical specimens at a single centre in Houston, TX, USA were studied. Among them, 61 isolates collected between 1999 and 2005 were defined as historical strains, and 108 collected between 2017 and 2018 were defined as contemporary strains. Antimicrobial susceptibilities against selected β-lactams was determined. WGS data were used for the identification of antimicrobial resistance determinants and phylogenetic analysis.

Results

Non-susceptibility to ceftolozane/tazobactam and ceftazidime/avibactam increased from 2% (1/59) to 17% (18/108) and from 7% (4/59) to 17% (18/108) from the historical to the contemporary collection, respectively. Carbapenemase genes, which were not identified in the historical collection, were harboured by 4.6% (5/108) of the contemporary strains, and the prevalence of ESBL genes also increased from 3.3% (2/61) to 16% (17/108). Genes encoding acquired β-lactamases were largely confined to the high-risk clones. Among ceftolozane/tazobactam-resistant isolates, non-susceptibility to ceftazidime/avibactam, imipenem/relebactam and cefiderocol was observed in 94% (15/16), 56% (9/16) and 12.5% (2/16), respectively. Resistance to ceftolozane/tazobactam and imipenem/relebactam was primarily associated with the presence of exogenous β-lactamases.

Conclusions

Acquisition of exogenous carbapenemases and ESBLs may be a worrisome trend in P. aeruginosa.

Efflux-Related Carbapenem Resistance in Acinetobacter baumannii Is Associated with Two-Component Regulatory Efflux Systems' Alteration and Insertion of ΔAbaR25-Type Island Fragment

The efflux pumps, beside the class D carbapenem-hydrolysing enzymes (CHLDs), are being increasingly investigated as a mechanism of carbapenem resistance in Acinetobacter baumannii. This study investigates the contribution of efflux mechanism to carbapenem resistance in 61 acquired bla_CHDL-genes-carrying A. baumannii clinical strains isolated in Warsaw, Poland. Studies were conducted using phenotypic (susceptibility testing to carbapenems ± efflux pump inhibitors (EPIs)) and molecular (determining expression levels of efflux operon with regulatory-gene and whole genome sequencing (WGS)) methods. EPIs reduced carbapenem resistance of 14/61 isolates. Upregulation (5-67-fold) of adeB was observed together with mutations in the sequences of AdeRS local and of BaeS global regulators in all 15 selected isolates. Long-read WGS of isolate no. AB96 revealed the presence of AbaR25 resistance island and its two disrupted elements: the first contained a duplicate ISAba1-bla_OXA-23, and the second was located between adeR and adeA in the efflux operon. This insert was flanked by two copies of ISAba1, and one of them provides a strong promoter for adeABC, elevating the adeB expression levels. Our study for the first time reports the involvement of the insertion of the ΔAbaR25-type resistance island fragment with ISAba1 element upstream the efflux operon in the carbapenem resistance of A. baumannii.

PlyKp104, a Novel Phage Lysin for the Treatment of Klebsiella pneumoniae, Pseudomonas aeruginosa, and Other Gram-Negative ESKAPE Pathogens

Klebsiella pneumoniae and Pseudomonas aeruginosa are two leading causes of burn and wound infections, pneumonia, urinary tract infections, and more severe invasive diseases, which are often multidrug resistant (MDR) or extensively drug resistant. Due to this, it is critical to discover alternative antimicrobials, such as bacteriophage lysins, against these pathogens. Unfortunately, most lysins that target Gram-negative bacteria require additional modifications or outer membrane permeabilizing agents to be bactericidal. We identified four putative lysins through bioinformatic analysis of Pseudomonas and Klebsiella phage genomes in the NCBI database and then expressed and tested their intrinsic lytic activity in vitro. The most active lysin, PlyKp104, exhibited >5-log killing against K. pneumoniae, P. aeruginosa, and other Gram-negative representatives of the multidrug-resistant ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, K. pneumonia, Acinetobacter baumannii, P. aeruginosa, and Enterobacter species) without further modification. PlyKp104 displayed rapid killing and high activity over a wide pH range and in high concentrations of salt and urea. Additionally, pulmonary surfactants and low concentrations of human serum did not inhibit PlyKp104 activity in vitro. PlyKp104 also significantly reduced drug-resistant K. pneumoniae >2 logs in a murine skin infection model after one treatment of the wound, suggesting that this lysin could be used as a topical antimicrobial against K. pneumoniae and other MDR Gram-negative infections.

Antimicrobial Resistance in Romania: Updates on Gram-Negative ESCAPE Pathogens in the Clinical, Veterinary, and Aquatic Sectors

Multidrug-resistant Gram-negative bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, and members of the Enterobacterales order are a challenging multi-sectorial and global threat, being listed by the WHO in the priority list of pathogens requiring the urgent discovery and development of therapeutic strategies. We present here an overview of the antibiotic resistance profiles and epidemiology of Gram-negative pathogens listed in the ESCAPE group circulating in Romania. The review starts with a discussion of the mechanisms and clinical significance of Gram-negative bacteria, the most frequent genetic determinants of resistance, and then summarizes and discusses the epidemiological studies reported for A. baumannii, P. aeruginosa, and Enterobacterales-resistant strains circulating in Romania, both in hospital and veterinary settings and mirrored in the aquatic environment. The Romanian landscape of Gram-negative pathogens included in the ESCAPE list reveals that all significant, clinically relevant, globally spread antibiotic resistance genes and carrying platforms are well established in different geographical areas of Romania and have already been disseminated beyond clinical settings.

The distribution characteristics of global blaOXA-carrying Klebsiella pneumoniae

Objective

To analyze the distribution of blaOXA among global Klebsiella pneumoniae and the characteristics of blaOXA-carrying K. pneumoniae.

Materials and Methods

The genomes of global K. pneumoniae were downloaded from NCBI by Aspera software. After quality check, the distribution of blaOXA among the qualified genomes was investigated by annotation with the resistant determinant database. The phylogenetic tree was constructed for the blaOXA variants based on the single nucleotide polymorphism (SNP) to explore the evolutionary relationship between these variants. The MLST (multi-locus sequence type) website and blastn tools were utilized to determine the sequence types (STs) of these blaOXA-carrying strains. and sample resource, isolation country, date and host were extracted by perl program for analyzing the characteristics of these strains.

Results

A total of 12,356 K. pneumoniae genomes were downloaded and 11,429 ones were qualified. Among them, 4386 strains were found to carry 5610 blaOXA variants which belonged to 27 varieties of blaOXAs, blaOXA-1 (n = 2891, 51.5%) and blaOXA-9 (n = 969, 17.3%) were the most prevalent blaOXA variants, followed by blaOXA-48 (n = 800, 14.3%) and blaOXA-232 (n = 480, 8.6%). The phylogenetic tree displayed 8 clades, three of them were composed of carbapenem-hydrolyzing oxacillinase (CHO). Totally, 300 distinct STs were identified among 4386 strains with ST11 (n = 477, 10.9%) being the most predominant one followed by ST258 (n = 410, 9.4%). Homo sapiens (2696/4386, 61.5%) was the main host for blaOXA-carrying K. pneumoniae isolates. The blaOXA-9-carrying K. pneumoniae strains were mostly found in the United States and blaOXA-48-carrying K. pneumoniae strains were mainly distributed in Europe and Asia.

Conclusion

Among the global K. pneumoniae, numerous blaOXA variants were identified with blaOXA-1, blaOXA-9, blaOXA-48 and blaOXA-232 being the most prevalent ones, indicating that blaOXA rapidly evolved under the selective pressure of antimicrobial agents. ST11 and ST258 were the main clones for blaOXA-carrying K. pneumoniae.

Molecular Detection of Extended Spectrum Beta-Lactamases in Clinical Isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa producing extended spectrum beta lactamases (ESBL) is a major concern in the hospital settings. It is usually reported in Enterobacteriaceae and is less frequently observed in P. aeruginosa. There is no recommended test for ESBL detection in P.aeruginosa. Therefore, we determined the occurrence of ESBL in clinical isolates of P.aeruginosa by both phenotypic and genotypic methods. Antimicrobial susceptibility tests were done on two hundred and thirteen isolates of P. aeruginosa. Phenotypic detection of ESBL was performed using combined disk method and ESBL encoding genes such as blaVEB, blaPER, blaPSE, blaGES, blaTEM, blaSHV, blaCTX-M, blaBEL, blaOXA1, blaOXA10, blaOXA2 were studied by simplex PCR. Of the 213 isolates, 85 were identified as resistant to ceftazidime and 27/85 isolates were confirmed to be ESBL producers by phenotypic method. The presence of genes encoding ESBLs comprising of blaTEM (n=44), blaOXA-10 (n=19) isolates, blaOXA-1 (n=5), blaOXA-2 (n=3) were found. All OXA gene positive isolates exhibited the ESBL phenotype. The blaGES gene were identified in 4/85 (5%) isolates. This study shows the prevalence of ESBL among clinical isolates of P.aeruginosa and in particular, the presence of GES β lactamases.

The Resistome of ESKAPEE Pathogens in Untreated and Treated Wastewater: A Polish Case Study

The aim of this study was to quantify ESKAPEE bacteria, genes encoding resistance to antibiotics targeting this group of pathogens, as well as integrase genes in municipal wastewater and river water. Environmental DNA was extracted from the collected samples and used in deep sequencing with the Illumina TruSeq kit. The abundance of bacterial genera and species belonging to the ESKAPEE group, 400 ARGs associated with this microbial group, and three classes of integrase genes were determined. A taxonomic analysis revealed that Acinetobacter was the dominant bacterial genus, whereas Acinetobacter baumannii and Escherichia coli were the dominant bacterial species. The analyzed samples were characterized by the highest concentrations of the following ARGs: bla_GES, bla_OXA-58, bla_TEM, qnrB, and qnrS. Acinetobacter baumannii, E. coli, and genes encoding resistance to β-lactams (bla_VEB-1, bla_IMP-1, bla_GES, bla_OXA-58, bla_CTX-M, and bla_TEM) and fluoroquinolones (qnrS) were detected in samples of river water collected downstream from the wastewater discharge point. The correlation analysis revealed a strong relationship between A. baumannii (bacterial species regarded as an emerging human pathogen) and genes encoding resistance to all tested groups of antimicrobials. The transmission of the studied bacteria (in particular A. baumannii) and ARGs to the aquatic environment poses a public health risk.

The biogenesis of β-lactamase enzymes

The discovery of penicillin by Alexander Fleming marked a new era for modern medicine, allowing not only the treatment of infectious diseases, but also the safe performance of life-saving interventions, like surgery and chemotherapy. Unfortunately, resistance against penicillin, as well as more complex β-lactam antibiotics, has rapidly emerged since the introduction of these drugs in the clinic, and is largely driven by a single type of extra-cytoplasmic proteins, hydrolytic enzymes called β-lactamases. While the structures, biochemistry and epidemiology of these resistance determinants have been extensively characterized, their biogenesis, a complex process including multiple steps and involving several fundamental biochemical pathways, is rarely discussed. In this review, we provide a comprehensive overview of the journey of β-lactamases, from the moment they exit the ribosomal channel until they reach their final cellular destination as folded and active enzymes.

Genotyping of Extended Spectrum Beta-Lactamase-Producing Pseudomonas aeruginosa Isolated from People with Nosocomial Infections

Background: Pseudomonas aeruginosa nosocomial infections are among major problems associated with increased mortality and mobility among patients. Objectives: The aim of this research was to determine the molecular epidemiology of extended spectrum beta-lactamase (ESBL)-producing P. aeruginosa genotypes isolated from patients with nosocomial infections. Methods: One hundred forty-six clinical isolates of Pseudomonas spp. were obtained from a tertiary referral hospital. Phenotypic identification and PCR detection of gyrB were used to characterize P. aeruginosa. Extended spectrum beta-lactamases in samples were identified using the disk approximation test and the combination disk test (CDT). The blaSHV and blaTEM genes were detected by PCR. The strains were typed by the pulse field gel electrophoresis (PFGE), repetitive element sequence (Rep)-PCR, and enterobacterial repetitive intergenic consensus (ERIC)–PCR methods. Results: A total of 134 (91.78%) P. aeruginosa isolates were separated, 41.79% of whom were related to nosocomial infections. The extended spectrum beta-lactamase analysis test revealed that 5.97% and 66.41% of the isolates harbored the blaSHV and blaTEM genes, respectively. Enterobacterial repetitive intergenic consensus PCR, Rep-PCR, and PFGE each showed 56, 55, and 55 different patterns, respectively. Pulse-field gel electrophoresis indicated that pulso types C3 were dominant. Conclusions: The associations between ESBL production, blaSHV and blaTEM positivity, and ERIC, Rep-PCR, and PFGE patterns were not significant (P ≥ 0.05). Among nosocomial infections, a relatively high prevalence of ESBL-producing P. aeruginosa isolates was observed in the Kurdistan province of Iran. Periodic review of antibiotic resistance and molecular characterization of P. aeruginosa isolates is recommended to prevent the spread of nosocomial infections in hospitals.

Combination of phage therapy and cefiderocol to successfully treat Pseudomonas aeruginosa cranial osteomyelitis

Background

Pseudomonas aeruginosa has the ability to exhibit resistance to a broad range of antibiotics, highlighting the importance of identifying alternative or adjunctive treatment options, such as phages.

Patients and methods

We report the case of a 25-year-old male who experienced an accidental electrocution resulting in exposed calvarium in the left parieto-temporal region, complicated by a difficult-to-treat P. aeruginosa (DTR-P. aeruginosa) infection. Cefiderocol was the sole antibiotic with consistent activity against six bacterial isolates obtained from the infected region over a 38 day period.

Results

WGS analysis identified a bla GES-1 gene as well as the MDR efflux pumps MexD and MexX in all six of the patient's ST235 DTR-P. aeruginosa isolates, when compared with the reference genome P. aeruginosa PA01 and a P. aeruginosa ST235 isolate from an unrelated patient. After debridement of infected scalp and bone, the patient received approximately 6 weeks of cefiderocol in conjunction with IV phage Pa14NPøPASA16. Some improvement was observed after the initiation of cefiderocol; however, sustained local site improvement and haemodynamic stability were not achieved until phage was administered. No medication-related toxicities were observed. The patient remains infection free more than 12 months after completion of therapy.

Conclusions

This report adds to the growing literature that phage therapy may be a safe and effective approach to augment antibiotic therapy for patients infected with drug-resistant pathogens. Furthermore, it highlights the importance of the GES β-lactamase family in contributing to inactivation of a broad range of β-lactam antibiotics in P. aeruginosa, including ceftolozane/tazobactam, ceftazidime/avibactam and imipenem/relebactam.

High prevalence of blaVEB , blaGES and blaPER genes in beta-lactam resistant clinical isolates of Pseudomonas aeruginosa

The increased prevalence of β-lactamase is one of the main factors in resistance to β-lactams in Pseudomonas aeruginosa. This study aimed to investigate the prevalence of blaVEB , blaPER , and blaGES genes in β-lactam-resistant P. aeruginosa. We collected 100 non-duplicated clinical isolates of P. aeruginosa and identified them by standard tests. Using disk agar diffusion test, we detected the β-lactam-resistant isolates and extracted the DNAs of the isolates by alkaline lysis method. Then, the prevalence of blaVEB , blaPER and blaGES genes were detected by PCR method. The results were assessed by SPSS 21 software and Chi-square test. Out of 100 isolates, 43% were detected as resistant against at least one of the beta-lactams tested. Piperacillin-tazobactam was the most effective antibiotic, while 39% and 37% of the isolates were resistant to aztreonam and meropenem, respectively. A significant relationship was observed between the resistance to tested antibiotics and the presence of blaVEB , blaGES , and blaPER genes. Among 43 isolates that were resistant to at least one of the tested β-lactams, 93.02%, 83.72%, and 81.39% of them carried blaVEB , blaGES , and blaPER genes, respectively. According to this study and due to high prevalence of β-lactam resistance genes, it is better to check the level of antibiotic resistance and resistance genes for better management of patients with infection caused by this bacterium. Also, high prevalence of class A β-lactamases indicates the significant role of these enzymes in emerging resistance to beta-lactams.

Multidrug-resistant bacteria isolated from surgical site of dogs, surgeon's hands and operating room in a veterinary teaching hospital in Brazil

Surgical environment can play as a source of multidrug-resistance organism, what can pose as a big threat to the patients and health care professionals. This study aimed to evaluate the prevalence and antimicrobial resistance profile of Gram-positive cocci (GPC) and Gram-negative bacilli (GNB) isolated from the surgical environment. All samples were collected during the intraoperative period of clean/clean-contaminated (G1) and contaminated (G2) surgery. A total of 150 samples were collected from the superficial surgical site in the beginning (n=30) and the end (n=30) of the procedure, surgeon's hands before (n=30) and after (n=30) antisepsis, and the surgical environment (n=30). MALDI-TOF MS and antimicrobial susceptibility testing by disk diffusion method were performed for species identification, and determination of the resistance profile. Sixty-eight isolates of GPC and 15 of GNB were obtained. Staphylococcus spp. were the most frequent species isolated from surgical site (55.26% [21/38]), surgeon's hands (46.15% [6/13]), and environment (56.67% [17/30]). GPC were mostly resistance to penicillin (85.71% [54/63]), and erythromycin (77.78% [49/63]), and GNB were mostly resistance to cefazolin (58.33% [7/12]), and azithromycin (58.33% [7/12]). High incidence of multidrug resistance was observed in coagulase-negative staphylococci (86.21% [25/29]), coagulase-positive staphylococci (86.67% [13/15]), Enterococcus spp. (68.42% [13/19]) and Gram-negative bacilli (60% [9/15]). The high rate of resistance of commensal bacteria found in our study is worrying. Coagulase-negative staphylococci are community pathogens related to nosocomial infections in human and veterinary hospitals, their presence in healthy patients and in veterinary professionals represent an important source of infection in the one health context. Continuous surveillance and application of antimicrobial stewardship programs are essential in the fight against this threat.

Association of blaVIM-2, blaPDC-35, blaOXA-10, blaOXA-488 and blaVEB-9 β-Lactamase Genes with Resistance to Ceftazidime–Avibactam and Ceftolozane–Tazobactam in Multidrug-Resistant Pseudomonas aeruginosa

Ceftazidime–avibactam and ceftolozane–tazobactam are approved for the treatment of complicated Gram-negative bacterial infections including multidrug-resistant (MDR) Pseudomonas aeruginosa. Resistance to both agents has been reported, but the underlying mechanisms have not been fully explored. This study aimed to correlate β-lactamases with phenotypic resistance to ceftazidime–avibactam and/or ceftolozane–tazobactam in MDR-P. aeruginosa from Qatar. A total of 525 MDR-P. aeruginosa isolates were collected from clinical specimens between 2014 and 2017. Identification and antimicrobial susceptibility were performed by the BD Phoenix^TM system and gradient MIC test strips. Of the 75 sequenced MDR isolates, 35 (47%) were considered as having difficult-to-treat resistance, and 42 were resistant to ceftazidime–avibactam (37, 49.3%), and/or ceftolozane–tazobactam (40, 53.3%). They belonged to 12 sequence types, with ST235 being predominant (38%). Most isolates (97.6%) carried one or more β-lactamase genes, with bla_OXA-488 (19%) and bla_VEB-9 (45.2%) being predominant. A strong association was detected between class B β-lactamase genes and both ceftazidime–avibactam and ceftolozane–tazobactam resistance, while class A genes were associated with ceftolozane–tazobactam resistance. Co-resistance to ceftazidime–avibactam and ceftolozane–tazobactam correlated with the presence of bla_VEB-9, bla_PDC-35, bla_VIM-2, bla_OXA-10 and bla_OXA-488. MDR-P. aeruginosa isolates resistant to both combination drugs were associated with class B β-lactamases (bla_VIM-2) and class D β-lactamases (bla_OXA-10), while ceftolozane–tazobactam resistance was associated with class A (bla_VEB-9), class C (bla_VPDC-35), and class D β-lactamases (bla_OXA-488).

Characterisation of AmpC / ESBL genes in some pathogen gram-negatives isolated from clinical cases of livestock and companion animals

This study was aimed to search and characterize the AmpC and/or ESBL genes of Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa isolated from clinical cases of local livestock and companion animals between 2017 and 2019. A total of eight ceftiofur-resistant E. coli (n= 7) and ceftiofur-resistant K. pneumoniae (n= 1) and seven P. aeruginosa were isolated from different cases in local animals. By combination disc method, six E. coli isolates and one K. pneumoniae isolate were found to be ESBL producers. By combination of the disc method and double disc synergy test, no P. aeruginosa isolates were found as ESBL producers. In the agar disc diffusion test (ADDT) performed with cefoxitin and cefoxitin-boronic, only one E. coli was determined as AmpC producer. In ESBL-producing isolates, only the CTX-M class gene was detected by polymerase chain reaction (PCR) and subsequent sequence analysis revealed CTX-M-3 and CTX-M-15 variants. An AmpC positive E. coli isolate was found to carry plasmidic ampC gene in cmy-2 variant from CIT family. It was observed that P. aeruginosa isolates did not carry the plasmidic ampC gene. After the chromosomal ampC gene of one P. aeruginosa was amplified by PCR and sequenced, R79Q and T105A mutations in the chromosomal ampC gene was revealed. This showed that overproduction of the ampC enzyme is involved in the resistance to β-lactams in P. aeruginosa isolates in the study.

Bacterial profile of high-touch surfaces, leftover drugs and antiseptics together with their antimicrobial susceptibility patterns at University of Gondar Comprehensive Specialized Hospital, Northwest Ethiopia

Background

The hospital environment serves as a source of nosocomial infections, which pose a major therapeutic challenge. Although many bacteria species are common in hospital environments, their distribution, frequency, and antimicrobial susceptibility pattern from high-touch surfaces, leftover drugs, and antiseptics in different wards remain largely unknown. Hence, the aim of this study was to assess the magnitude and frequency of bacterial contaminants and their antimicrobial susceptibility patterns.

Methods

A total of 384 samples were collected from five selected wards and processed according to standard bacteriological procedures. Samples were collected from high-touch surface using swabs and inoculated on Blood agar, MacConkey agar, Chocolate agar and Mannitol salt agar plates, and incubated at 37 °C for 24 h. On the other hand, the leftover drugs and 80% ethanol samples were collected using sterile cotton swab immersed in sterile tryptone soy broth then inoculated on culture medias and incubated at 37 °C for 24 h. Identification of bacteria species was done using the morphological characteristics, Gram stain, and biochemical tests while antimicrobial susceptibility tests were done using modified Kirby-Bauer disk diffusion technique following the Clinical Laboratory Standards Institute 2021guidelines.

Results

Among the 384 samples processed, 102 (26.6%) were culture positive and a total of 114 bacterial isolates were identified. Gram-positive bacterial isolates were predominant, 64.9%, while Gram-negatives were 35.1%. The most frequently isolated bacteria were coagulase negative Staphylococci (38.6%) followed by S. aureus (13.2%) and P. aeruginosa (11.4%). On the other hand, the proportion of bacteria isolated from surgical ward, post-natal ward, orthopedic ward, trauma ward, and neonatal intensive care unit ward were 24.6, 21, 20.2, 18.4,15.8%, respectively. Sinks were mainly contaminated with Klebsiella species (81.8%) and A. baumannii (55.6%), while A. baumannii (22.2%) was the most contaminant for 80% ethanol. Gram-positive bacteria had significantly high resistance levels to penicillin (67.6%), cotrimoxazole (67.8%), and cefepime (80%). On the other hand, Gram-negative bacteria revealed the highest resistance levels to tetracycline (82.4%), amoxicillin-clavulanic acid (76.5%), cefepime (66.7%), ceftazidime (67.5%), and piperacillin (92.3%). Moreover, the proportion of multidrug resistant bacteria isolates was 44.7%.

Conclusions

Data of the present study showed that coagulase negative Staphylococci was the dominant bacterial isolates followed by S. aureus and P. aeruginosa. The proportion of multi-drug resistant bacteria isolates was relatively high. Therefore, appropriate infection prevention and control measures should be implemented.

Antibiotic Resistance Pattern of Pseudomonas aeruginosa Isolated from Clinical Specimens from a Tertiary Care Centre in Central Kerala with Special Reference to Carbapenemase Detection

Pseudomonas aeruginosa is inherently resistant to many drugs. It is now an emerging opportunistic pathogen of clinical relevance. The emergence of carbapenemases is another major concern. Initiation of appropriate therapy is of paramount importance thus highlighting the need of active surveillance for newer emerging resistance trends for better infection control. To study the resistance pattern of P. aeruginosa isolates obtained from lab specimens and to determine the production of ESBL and Carbapenemase among them. A hospital-based cross-sectional study was carried out in the Department of Microbiology, Government medical college Thrissur, among P. aeruginosa isolates obtained from lab specimens, from January 2018 – December 2018. 162 isolates were studied. Antimicrobial susceptibility testing was done by Kirby – Bauer disc diffusion method, extended-spectrum beta-lactamase (ESBL) production was confirmed by and phenotypic confirmatory disc diffusion test. Carbapenemase detection was done using the modified carbapenemase inactivation (mCIM) method. The obtained data was analysed. Among 162 isolates 83% were non-multidrug-resistant (MDR) strains and 17% were MDR strains. 22% of ceftazidime resistant isolates were ESBL producers. 6.2% isolates were resistant to imipenem. Among the imipenem resistant isolates, Carbapenemase production was seen in 30% isolates by mCIM test. According to our study, the most effective antibiotic against P. aeruginosa were imipenem and cefoperazone/sulbactam showing resistance in 6.3% and 6.9% isolates respectively. The diversity of antibiotic resistance mechanisms and the emergence of carbapenem resistance is a threat that limits treatment choices. This suggests the need for ongoing antimicrobial susceptibility studies in the future.

In Vivo Evolution of GES β-Lactamases Driven by Ceftazidime/Avibactam Treatment of Pseudomonas aeruginosa Infections

The mechanisms underlying an in vivo switch in the resistance phenotype of P. aeruginosa after ceftazidime-avibactam treatment was investigated. The initial isolate (a blood culture) was resistant to meropenem but remained susceptible to antipseudomonal cephalosporins and combinations with β-lactamase inhibitors. One week after ceftazidime-avibactam therapy, a subsequent isolate (a rectal swab) recovered from the same patient showed the opposite phenotype. Whole-genome sequence analysis revealed a single SNP difference between both (ST235) isolates, leading to a P162S change in bla_GES-5, creating bla_GES-15. Thus, bla_GES-1, bla_GES-5, and bla_GES-15 were cloned and expressed in the wild-type strain PAO1. Susceptibility profiles confirmed the P162S substitution reverted the carbapenemase phenotype determined by the G170S change of GES-5 back into the ESBL phenotype of GES-1.

Coming from the Wild: Multidrug Resistant Opportunistic Pathogens Presenting a Primary, Not Human-Linked, Environmental Habitat

The use and misuse of antibiotics have made antibiotic-resistant bacteria widespread nowadays, constituting one of the most relevant challenges for human health at present. Among these bacteria, opportunistic pathogens with an environmental, non-clinical, primary habitat stand as an increasing matter of concern at hospitals. These organisms usually present low susceptibility to antibiotics currently used for therapy. They are also proficient in acquiring increased resistance levels, a situation that limits the therapeutic options for treating the infections they cause. In this article, we analyse the most predominant opportunistic pathogens with an environmental origin, focusing on the mechanisms of antibiotic resistance they present. Further, we discuss the functions, beyond antibiotic resistance, that these determinants may have in the natural ecosystems that these bacteria usually colonize. Given the capacity of these organisms for colonizing different habitats, from clinical settings to natural environments, and for infecting different hosts, from plants to humans, deciphering their population structure, their mechanisms of resistance and the role that these mechanisms may play in natural ecosystems is of relevance for understanding the dissemination of antibiotic resistance under a One-Health point of view.

Extended-spectrum β-lactamases: an update on their characteristics, epidemiology and detection

Extended-spectrum β-lactamase (ESBL)-producing Gram-negative pathogens are a major cause of resistance to expanded-spectrum β-lactam antibiotics. Since their discovery in the early 1980s, they have spread worldwide and an are now endemic in Enterobacterales isolated from both hospital-associated and community-acquired infections. As a result, they are a global public health concern. In the past, TEM- and SHV-type ESBLs were the predominant families of ESBLs. Today CTX-M-type enzymes are the most commonly found ESBL type with the CTX-M-15 variant dominating worldwide, followed in prevalence by CTX-M-14, and CTX-M-27 is emerging in certain parts of the world. The genes encoding ESBLs are often found on plasmids and harboured within transposons or insertion sequences, which has enabled their spread. In addition, the population of ESBL-producing Escherichia coli is dominated globally by a highly virulent and successful clone belonging to ST131. Today, there are many diagnostic tools available to the clinical microbiology laboratory and include both phenotypic and genotypic tests to detect β-lactamases. Unfortunately, when ESBLs are not identified in a timely manner, appropriate antimicrobial therapy is frequently delayed, resulting in poor clinical outcomes. Several analyses of clinical trials have shown mixed results with regards to whether a carbapenem must be used to treat serious infections caused by ESBLs or whether some of the older β-lactam-β-lactamase combinations such as piperacillin/tazobactam are appropriate. Some of the newer combinations such as ceftazidime/avibactam have demonstrated efficacy in patients. ESBL-producing Gram-negative pathogens will continue to be major contributor to antimicrobial resistance worldwide. It is essential that we remain vigilant about identifying them both in patient isolates and through surveillance studies.

Molecular Characterization of Extended-Spectrum Beta-Lactamase-Producing Enterobacteriaceae Isolates Collected from Inanimate Hospital Environments in Addis Ababa, Ethiopia

INTRODUCTION

The hospital environment contributes to the spread of Extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-PE), which are contributing to increased morbidity and mortality rates. The present study was carried out to detect environmental contamination, antimicrobial susceptibility testing of ESBL-PE, and to explore molecular characterization of ESBL encoding genes.

METHODS

A cross-sectional study was conducted within the intensive care units (ICUs) of Tikur Anbessa Specialized Hospital from June to July 2018. A total of 97 swabs were taken from high-contact inanimate surfaces near immediate patient environments. All isolates were cultured by using ESBL ChromoSelect Agar and identified with conventional bacteriological methods. Antimicrobial susceptibility testing was performed as recommended by Clinical and Laboratory Standards Institute. Combination disk test was used to confirm ESBL production, while molecular characterizations of ESBL genes were performed by polymerase chain reaction.

RESULTS

Out of 97 swabbed sample, 24 (24.7%) were confirmed as ESBL-PE. The most predominant ESBL-PE was from E. coli (41.7%) and K. pneumoniae (25%). The Pediatrics and Neonatal ICU (29.2%, 7/24) exhibited highest ESBL-PE. The most contaminated materials were bed linens (33.3%). Most of ESBL-PE isolates were resistant to ampicillin (100%) and ceftriaxone (91.7%). A low resistance level was recorded for amikacin (25%). Among ESBL-producing genes, bla_CTX-M (35.7%) was the most prevalent, followed by bla_TEM and bla_SHV gene 32.1% for each.

CONCLUSIONS

Appearance of ESBL-PE in ICUs environment is posing a serious threat to control healthcare associated infections. The high level of resistance shows the need of policies for devising infection control procedures and detection of ESBL-PE.

The Building Blocks of Antimicrobial Resistance in Pseudomonas aeruginosa: Implications for Current Resistance-Breaking Therapies

P. aeruginosa is classified as a priority one pathogen by the World Health Organisation, and new drugs are urgently needed, due to the emergence of multidrug-resistant (MDR) strains. Antimicrobial-resistant nosocomial pathogens such as P. aeruginosa pose unwavering and increasing threats. Antimicrobial stewardship has been a challenge during the COVID-19 pandemic, with a majority of those hospitalized with SARS-CoV2 infection given antibiotics as a safeguard against secondary bacterial infection. This increased usage, along with increased handling of sanitizers and disinfectants globally, may further accelerate the development and spread of cross-resistance to antibiotics. In addition, P. aeruginosa is the primary causative agent of morbidity and mortality in people with the life-shortening genetic disease cystic fibrosis (CF). Prolonged periods of selective pressure, associated with extended antibiotic treatment and the actions of host immune effectors, results in widespread adaptive and acquired resistance in P. aeruginosa found colonizing the lungs of people with CF. This review discusses the arsenal of resistance mechanisms utilized by P. aeruginosa, how these operate under high-stress environments such as the CF lung and how their interconnectedness can result in resistance to multiple antibiotic classes. Intrinsic, adaptive and acquired resistance mechanisms will be described, with a focus on how each layer of resistance can serve as a building block, contributing to multi-tiered resistance to antimicrobial activity. Recent progress in the development of anti-resistance adjuvant therapies, targeting one or more of these building blocks, should lead to novel strategies for combatting multidrug resistant P. aeruginosa. Anti-resistance adjuvant therapy holds great promise, not least because resistance against such therapeutics is predicted to be rare. The non-bactericidal nature of anti-resistance adjuvants reduce the selective pressures that drive resistance. Anti-resistance adjuvant therapy may also be advantageous in facilitating efficacious use of traditional antimicrobials, through enhanced penetration of the antibiotic into the bacterial cell. Promising anti-resistance adjuvant therapeutics and targets will be described, and key remaining challenges highlighted. As antimicrobial stewardship becomes more challenging in an era of emerging and re-emerging infectious diseases and global conflict, innovation in antibiotic adjuvant therapy can play an important role in extending the shelf-life of our existing antimicrobial therapeutic agents.

Detection of extended spectrum beta-lactamase genes in Pseudomonas aeruginosa isolated from patients in rural Eastern Cape Province, South Africa

The proliferation of extended spectrum beta-lactamase (ESBL) producing Pseudomonas aeruginosa represent a major public health threat. In this study, we evaluated the antimicrobial resistance patterns of P. aeruginosa strains and characterized the ESBLs and Metallo- β-lactamases (MBL) produced. Strains of P. aeruginosa cultured from patients who attended Nelson Mandela Academic Hospital and other clinics in the four district municipalities of the Eastern Cape between August 2017 and May 2019 were identified; antimicrobial susceptibility testing was carried out against thirteen clinically relevant antibiotics using the BioMérieux VITEK 2 and confirmed by Beckman autoSCAN-4 System. Real-time PCR was done using Roche Light Cycler 2.0 to detect the presence of ESBLs; bla_SHV, bla_TEM and bla_CTX-M genes; and MBLs; bla_IMP, bla_VIM. Strains of P. aeruginosa demonstrated resistance to wide-ranging clinically relevant antibiotics including piperacillin (64.2%), followed by aztreonam (57.8%), cefepime (51.5%), ceftazidime (51.0%), piperacillin/tazobactam (50.5%), and imipenem (46.6%). A total of 75 (36.8%) multidrug-resistant (MDR) strains were observed of the total pool of isolates. The bla_TEM, bla_SHV and bla_CTX-M was detected in 79.3%, 69.5% and 31.7% isolates (n = 82), respectively. The bla_IMP was detected in 1.25% while no bla_VIM was detected in any of the strains tested. The study showed a high rate of MDR P. aeruginosa in our setting. The vast majority of these resistant strains carried bla_TEM and bla_SHV genes. Continuous monitoring of antimicrobial resistance and strict compliance towards infection prevention and control practices are the best defence against spread of MDR P. aeruginosa.

Diversity and Distribution of Resistance Markers in Pseudomonas aeruginosa International High-Risk Clones

Pseudomonas aeruginosa high-risk clones are disseminated worldwide and they are common causative agents of hospital-acquired infections. In this review, we will summarize available data of high-risk P. aeruginosa clones from confirmed outbreaks and based on whole-genome sequence data. Common feature of high-risk clones is the production of beta-lactamases and among metallo-beta-lactamases NDM, VIM and IMP types are widely disseminated in different sequence types (STs), by contrast FIM type has been reported in ST235 in Italy, whereas GIM type in ST111 in Germany. In the case of ST277, it is most frequently detected in Brazil and it carries a resistome linked to bla_SPM. Colistin resistance develops among P. aeruginosa clones in a lesser extent compared to other resistance mechanisms, as ST235 strains remain mainly susceptible to colistin however, some reports described mcr positive P. aeurigonsa ST235. Transferable quinolone resistance determinants are detected in P. aeruginosa high-risk clones and aac(6′)-Ib-cr variant is the most frequently reported as this determinant is incorporated in integrons. Additionally, qnrVC1 was recently detected in ST773 in Hungary and in ST175 in Spain. Continuous monitoring and surveillance programs are mandatory to track high-risk clones and to analyze emergence of novel clones as well as novel resistance determinants.

Molecular Detection of Antibiotic-Resistant Genes in Pseudomonas aeruginosa from Nonclinical Environment: Public Health Implications in Mthatha, Eastern Cape Province, South Africa

Evaluation of resistant profiles and detection of antimicrobial-resistant genes of bacterial pathogens in the nonclinical milieu is imperative to assess the probable risk of dissemination of resistant genes in the environment. This paper sought to identify antibiotic-resistant genes in Pseudomonas aeruginosa from nonclinical sources in Mthatha, Eastern Cape, and evaluate its public health implications. Samples collected from abattoir wastewater and aquatic environment were processed by membrane filtration and cultured on CHROMagarTM Pseudomonas medium. Species identification was performed by autoSCAN-4 (Dade Behring Inc., IL). Molecular characterization of the isolates was confirmed using real-time polymerase chain reaction (rPCR) and selected isolates were further screened for the possibility of harboring antimicrobial resistance genes. Fifty-one Pseudomonas species were recovered from abattoir wastewater and surface water samples, out of which thirty-six strains were Pseudomonas aeruginosa (70.6%). The P. aeruginosa isolates demonstrated resistance to aztreonam (86.1%), ceftazidime (63.9%), piperacillin (58.3%), cefepime (55.6%), imipenem (50%), piperacillin/tazobactam (47.2%), meropenem (41.7%), and levofloxacin (30.6%). Twenty out of thirty-six P. aeruginosa displayed multidrug resistance profiles and were classified as multidrug-resistant (MDR) (55.6%). Most of the bacterial isolates exhibited a high Multiple Antibiotic Resistance (MAR) Index ranging from 0.08 to 0.69 with a mean MAR index of 0.38. In the rPCR analysis of fifteen P. aeruginosa isolates, 14 isolates (93.3%) were detected harboring bla SHV, six isolates (40%) harbored bla TEM, and three isolates (20%) harbored bla CTX-M, being the least occurring ESBL. Results of the current study revealed that P. aeruginosa isolates recovered from nonclinical milieu are resistant to frontline clinically relevant antipseudomonal drugs. This is concerning as it poses a risk to the environment and constitutes a public health threat. Given the public health relevance, the paper recommends monitoring of multidrug-resistant pathogens in effluent environments.

A Critical Evaluation of Newer β-Lactam Antibiotics for Treatment of Pseudomonas aeruginosa Infections

OBJECTIVE

This article critically evaluates common Pseudomonas aeruginosa resistance mechanisms and the properties newer β-lactam antimicrobials possess to evade these mechanisms.

DATA SOURCES

An extensive PubMed, Google Scholar, and ClinicalTrials.gov search was conducted (January 1995 to July 2020) to identify relevant literature on epidemiology, resistance mechanisms, antipseudomonal agents, newer β-lactam agents, and clinical data available pertaining to P aeruginosa.

STUDY SELECTION AND DATA EXTRACTION

Relevant published articles and package inserts were reviewed for inclusion.

DATA SYNTHESIS

Therapeutic options to treat P aeruginosa infections are limited because of its intrinsic and acquired resistance mechanisms. The goal was to identify advances with newer β-lactams and characterize improvements in therapeutic potential for P aeruginosa infections.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Multidrug-resistant (MDR) P aeruginosa isolates are increasingly encountered from a variety of infections. This review highlights potential activity gains of newer β-lactam antibacterial drugs and the current clinical data to support their use. Pharmacists will be asked to recommend or evaluate the use of these agents and need to be aware of information specific to P aeruginosa, which differs from experience derived from Enterobacterales infections.

CONCLUSIONS

Newer agents, including ceftazidime-avibactam, ceftolozane-tazobactam, imipenem-relebactam, and cefiderocol, are useful for the treatment of MDR P aeruginosa infections. These agents offer improved efficacy and less toxicity compared with aminoglycosides and polymyxins and can be used for pathogens that are resistant to first-line antipseudomonal β-lactams. Selection of one agent over another should consider availability, turnaround of susceptibility testing, and product cost. Efficacy data specific for pseudomonal infections are limited, and there are no direct comparisons between the newer agents.

Evaluation of the Resistance Profile of Bacteria Obtained From Infected Sites of Dogs in a Veterinary Teaching Hospital in Brazil: A Retrospective Study

The aim of this study was to evaluate the prevalence and antimicrobial resistance profile of bacterial species isolated from infected sites of canines. All samples were collected from canine patients who received clinical or surgical care at the veterinary teaching hospital between March 2016 and November 2017. The samples were analyzed in a private pathology laboratory. A descriptive analysis of 295 antimicrobial susceptibility test reports was performed. Staphylococcus spp. (104/295 [35.25%]), Escherichia coli (100/295 [33.90%]), Proteus spp. (44/295 [14.92%]), Pseudomonas spp. (25/295 [8.47%]), and Klebsiella spp. (20/295 [6.78%]) were more frequently isolated, and a high incidence of multidrug resistance was observed (69,83% [206/295]). Methicillin-resistant Staphylococcus spp. accounted for 33% (33/100) of the Staphylococcus strains. Enterobacteriaceae cefotaxime resistance constituted 22.82 ± 4.49% and Enterobacteriaceae imipenem resistance constituted 5% (1/20) for Klebsiella spp., 5% (5/100) for E coli, and 6.82% (3/44) for Proteus spp. Pseudomonas spp. strains accounted for 8% (2/25) of imipenem resistance and 45.45% (10/22) of polymyxin B resistance. Our findings revealed a high rate of multidrug-resistant bacteria involvement in the infectious process of dogs. From the perspective of the One Health scenario, our results showed alarming data, given the high risk of resistant-strain dissemination between animals, owners, and healthcare professionals. There is an urgent need for strategies to control and prevent the evolution of new multidrug-resistant bacteria in veterinary hospitals. It is also crucial to understand and emphasize the role of veterinary professionals in this public health battle.

β-lactamase-mediated resistance in MDR-Pseudomonas aeruginosa from Qatar

Background

The distribution of β-lactam resistance genes in P. aeruginosa is often closely related to the distribution of certain high-risk international clones. We used whole-genome sequencing (WGS) to identify the predominant sequence types (ST) and β-lactamase genes in clinical isolates of multidrug-resistant (MDR)-P. aeruginosa from Qatar

Methods

Microbiological identification and susceptibility tests were performed by automated BD Phoenix™ system and manual Liofilchem MIC Test Strips.

Results

Among 75 MDR-P. aeruginosa isolates; the largest proportions of susceptibility were to ceftazidime-avibactam (n = 36, 48%), followed by ceftolozane-tazobactam (30, 40%), ceftazidime (n = 21, 28%) and aztreonam (n = 16, 21.3%). All isolates possessed Class C and/or Class D β-lactamases (n = 72, 96% each), while metallo-β-lactamases were detected in 20 (26.7%) isolates. Eight (40%) metallo-β-lactamase producers were susceptible to aztreonam and did not produce any concomitant extended-spectrum β-lactamases. High risk ST235 (n = 16, 21.3%), ST357 (n = 8, 10.7%), ST389 and ST1284 (6, 8% each) were most frequent. Nearly all ST235 isolates (15/16; 93.8%) were resistant to all tested β-lactams.

Conclusion

MDR-P. aeruginosa isolates from Qatar are highly resistant to antipseudomonal β-lactams. High-risk STs are predominant in Qatar and their associated MDR phenotypes are a cause for considerable concern.

Evaluation of in vitro activity of ceftazidime/avibactam and ceftolozane/tazobactam against MDR Pseudomonas aeruginosa isolates from Qatar

OBJECTIVES

To investigate the in vitro activity of ceftazidime/avibactam and ceftolozane/tazobactam against clinical isolates of MDR Pseudomonas aeruginosa from Qatar, as well as the mechanisms of resistance.

METHODS

MDR P. aeruginosa isolated between October 2014 and September 2015 from all public hospitals in Qatar were included. The BD PhoenixTM system was used for identification and initial antimicrobial susceptibility testing, while Liofilchem MIC Test Strips (Liofilchem, Roseto degli Abruzzi, Italy) were used for confirmation of ceftazidime/avibactam and ceftolozane/tazobactam susceptibility. Ten ceftazidime/avibactam- and/or ceftolozane/tazobactam-resistant isolates were randomly selected for WGS.

RESULTS

A total of 205 MDR P. aeruginosa isolates were included. Of these, 141 (68.8%) were susceptible to ceftazidime/avibactam, 129 (62.9%) were susceptible to ceftolozane/tazobactam, 121 (59.0%) were susceptible to both and 56 (27.3%) were susceptible to neither. Twenty (9.8%) isolates were susceptible to ceftazidime/avibactam but not to ceftolozane/tazobactam and only 8 (3.9%) were susceptible to ceftolozane/tazobactam but not to ceftazidime/avibactam. Less than 50% of XDR isolates were susceptible to ceftazidime/avibactam or ceftolozane/tazobactam. The 10 sequenced isolates belonged to six different STs and all produced AmpC and OXA enzymes; 5 (50%) produced ESBL and 4 (40%) produced VIM enzymes.

CONCLUSIONS

MDR P. aeruginosa susceptibility rates to ceftazidime/avibactam and ceftolozane/tazobactam were higher than those to all existing antipseudomonal agents, except colistin, but were less than 50% in extremely resistant isolates. Non-susceptibility to ceftazidime/avibactam and ceftolozane/tazobactam was largely due to the production of ESBL and VIM enzymes. Ceftazidime/avibactam and ceftolozane/tazobactam are possible options for some patients with MDR P. aeruginosa in Qatar.

Carbapenemase-producing Pseudomonas aeruginosa in Spain: interregional dissemination of the high-risk clones ST175 and ST244 carrying blaVIM-2, blaVIM-1, blaIMP-8, blaVIM-20 and blaKPC-2

Carbapenemase-producing (CP) Pseudomonas aeruginosa is rare compared with mutation-driven carbapenem-resistance, but this situation may be changing. A collection of CP P. aeruginosa isolates was characterized in this study. In 2016, 232 unduplicated carbapenem-resistant P. aeruginosa isolates, of which 71 (30.6%) carried carbapenemase genes, were submitted to the Spanish antibiotic reference laboratory and were further analysed by whole-genome sequencing (WGS). Of the 71 CP P. aeruginosa, 39 (54.9%) carried bla_VIM-2, 14 (19.7%) bla_VIM-1, 8 (11.3%) bla_IMP-8, 6 (8.5%) bla_VIM-20, 2 (2.8%) bla_VIM-2 plus bla_KPC-2, one (1.4%) bla_IMP-13 and one (1.4%) bla_VIM-1 plus bla_IMP-18. Four sequence types (ST175, ST244, ST815 and ST155) encompassed 83.1% of the 71 CP P. aeruginosa; ST175 was detected in hospitals from seven provinces. Using core genome multilocus sequence typing (cgMLST), four clusters were detected: Cluster 1 included nine ST815/VIM-2 isolates; Cluster 2 included five ST175/VIM-2 isolates; Cluster 3 included seven ST244 isolates (five VIM-2 and two VIM-2 plus KPC-2); and Cluster 4 included 11 ST175 isolates (seven VIM-2 and four IMP-8). The average number of acquired resistance genes was significantly higher in the bla_VIM-1-carying isolates (7.1 ± 0.94) than in the bla_VIM-2-carrying isolates (4.5 ± 0.20). CP P. aeruginosa isolates are spreading in Spain, mainly due to the dissemination of high-risk clones such as ST175 and ST244 producing VIM and IMP carbapenemases. Emergence of CP P. aeruginosa is a cause of clinical and epidemiological concern.

Evaluating the antimicrobial resistance patterns and molecular frequency of bla oxa-48 and bla GES-2 genes in Pseudomonas aeruginosa and Acinetobacter baumannii strains isolated from burn wound infection in Tehran, Iran

The aim of this study is to evaluate the antimicrobial resistance patterns and molecular frequency of bla_GES-2 and bla_oxa-48 genes in Pseudomonas aeruginosa and Acinetobacter baumannii strains isolated from burn wound infection in Tehran, Iran. In this study, 50 isolates of A. baumannii and 48 isolates of P. aeruginosa were collected from the Burn Unit of Shahid Motahari Hospital at Tehran, Iran. Antibiotic susceptibility tests of all isolates were carried out using the disc diffusion method, and the production of extended-spectrum β-lactamases (ESBLs) in isolates was surveyed by the double disc synergy method and based on CLSI (2019 AST M100) criteria. Finally, the frequency of bla_GES-2 and bla_oxa-48 genes was surveyed by PCR. Antibiotic susceptibility tests showed that 48/48 (100%) of P. aeruginosa isolates and 49/50 (98%) of A. baumannii isolates were resistant to ceftriaxone and cefotaxime, respectively. Ceftazidime exhibited the lowest (26/48; 54.1%) resistance rates against P. aeruginosa isolates. The production of ESBLs was seen in 8/48 (16.6%) and 3/50 (6%) of P. aeruginosa and A. baumannii isolates, respectively. On the basis of conventional PCR and sequencing, the frequencies of the bla_GES-2 gene among P. aeruginosa and A. baumannii was 87.5% and 58%, respectively. Moreover, bla_oxa-48 gene was detected in 70.83% and 92% of P. aeruginosa and A. baumannii isolates, respectively. Results suggest that antibiotic-resistant A. baumannii and P. aeruginosa strains isolated from burn patients are frequently found; therefore, it is absolutely necessary to implement continuous screening and follow-up programmes for detecting antimicrobial resistance.

Detection and genetic characterization of extended-spectrum beta-lactamases producers in a tertiary care hospital

BACKGROUND

Extended-spectrum beta-lactamase (ESBL)-producing organisms inactivate extended beta-lactam antibiotics and monobactams and also exhibit coresistance to many other classes of antibiotics. The present study was carried out to assess the prevalence of the ESBLs and to determine the most prevalent genotype in our hospital.

MATERIALS AND METHODS

All clinically significant Gram-negative isolates were identified, and their antimicrobial susceptibility testing was done by Kirby-Bauers' disc diffusion method. ESBL detection was confirmed by minimal inhibitory concentration method using agar dilution technique for those who screened positive by ceftazidime (30 μg) disc. Further, the established ESBL-positive isolates were subjected to genotyping for bla TEM, bla CTX-M, and bla SHV genes by using conventional polymerase chain reaction.

RESULTS

Escherichia coli was the most common (28.84%) Gram-negative bacillus followed by Klebsiella pneumoniae (18.07%), while Pseudomonas spp. (9.61%) was the most commonly identified nonfermenter. ESBL production was detected in 160 (30.8%) isolates. Klebsiella oxytoca (46.7%) followed by E. coli (44%) were the common ESBL producers. Most predominant ESBL gene was bla TEM, found in 122 (76.25%) isolates. Combinations of two genes were seen in 109 (68.1%) isolates, the most common (43.12%) combination being bla_TEM and bla_CTX-M. In this study, 16 (10%) strains had all the three types of genes. Most of the isolated Gram-negative bacilli (GNB) were sensitive to amikacin, imipenem, and colistin.

CONCLUSION

In our study, the 30.8% of GNB were ESBL producers. This is the only study that shows that TEM is the most prevalent ESBL genotypes in our area. Of concern is a good number of isolates showing all three patterns of genes (TEM, SHV, and CTX-M). Amikacin, imipenem, and colistin were the most useful antibiotics in our setup.

In vitro Reducing Effect of Cloxacillin on Minimum Inhibitory Concentrations to Imipenem, Meropenem, Ceftazidime, and Cefepime in Carbapenem-resistant Pseudomonas aeruginosa Isolates

Today, resistance to antibacterial agents is the most important problem facing public health. Pseudomonas aeruginosa is a common gram-negative bacterium and an important cause of nosocomial infections. Resistance to many antibiotics in strains of P. aeruginosa isolated from hospital settings such as cephalosporins and carbapenems have been recently reported. Therefore, the introduction of a new strategy to treat the infection of these organisms will be beneficial. In this study we determined the ability of cloxacillin to reduce Minimum Inhibitory Concentrations (MICs) of carbapenem-resistant P. aeruginosa to imipenem (IMI), meropenem (MEM), ceftazidime (CAZ), and cefepime (FEP). From 2015 to 2017, 61 non-duplicates of carbapenem-resistant P. aeruginosa were collected from clinical samples of hospitalized patients in Kerman, Iran. The MICs of the isolates to IMI, MEM, CAZ, and FEP with/without cloxacillin were determined by microbroth dilution method. The level of MIC of isolates to carbapenems (IMI and MEM) and cephalosporins (CAZ and FEP) ranged from 1-256 μg/mL and 4-1024 μg/mL alone and from 1-32 μg/mL and 1-512 μg/mL in combination with cloxacillin, respectively. The MIC showed a significant difference reduction after the addition of cloxacillin (P ≤ 0.05). Our results showed in vitro potentially of cloxacillin in reduction of MIC to IMI, MEM, CAZ, and FEP in multi-drug resistant P. aeruginosa, therefore combination of these antibiotics with cloxacillin could be beneficial for treatment of infections caused by multi-drug resistant P. aeruginosa.

Epidemiology of β-Lactamase-Producing Pathogens

β-Lactam antibiotics have been widely used as therapeutic agents for the past 70 years, resulting in emergence of an abundance of β-lactam-inactivating β-lactamases. Although penicillinases in Staphylococcus aureus challenged the initial uses of penicillin, β-lactamases are most important in Gram-negative bacteria, particularly in enteric and nonfermentative pathogens, where collectively they confer resistance to all β-lactam-containing antibiotics. Critical β-lactamases are those enzymes whose genes are encoded on mobile elements that are transferable among species. Major β-lactamase families include plasmid-mediated extended-spectrum β-lactamases (ESBLs), AmpC cephalosporinases, and carbapenemases now appearing globally, with geographic preferences for specific variants. CTX-M enzymes include the most common ESBLs that are prevalent in all areas of the world. In contrast, KPC serine carbapenemases are present more frequently in the Americas, the Mediterranean countries, and China, whereas NDM metallo-β-lactamases are more prevalent in the Indian subcontinent and Eastern Europe. As selective pressure from β-lactam use continues, multiple β-lactamases per organism are increasingly common, including pathogens carrying three different carbapenemase genes. These organisms may be spread throughout health care facilities as well as in the community, warranting close attention to increased infection control measures and stewardship of the β-lactam-containing drugs in an effort to control selection of even more deleterious pathogens.