Β-lactam Antibiotic Resistance Research Articles

Epidemiological, Phylogenetic, and Resistance Heterogeneity Among Acinetobacter baumannii in a Large U.S. Deep South Healthcare system.

Acinetobacter baumannii (Ab) disease in the United States is commonly attributed to outbreaks of 1 or 2 monophyletic carbapenem resistance (CR) Ab lineages that vary by region. However, there is limited knowledge regarding CRAb epidemiology and population structures in the U.S. Deep South, and few studies compare contemporary CR and carbapenem-susceptible (Cs) Ab, despite relative prevalence of the latter. We performed a multiyear analysis of 2462 Ab cases in a large healthcare system in Birmingham, AL, and 89 post-2021 Ab isolates were sequenced and phenotyped by antibiotic susceptibility tests. Although the cumulative CR rate was 17.7% in our cohort, rates regularly increased in winter months as result of seasonal changes in case incidence of CsAb, specifically. Genotyped CRAb belonged to clonal group (CG) 1, CG2, CG108, CG250, or CG499, with local clones of CG108, CG250, and CG499 persisting over multiple months. There was no clonal expansion of any CsAb lineage. Among CRAb isolates, levels of β-lactam antibiotic resistance and the repertoire of related genetic resistance determinants, which included the novel CR-conferring FtsI A515V polymorphism, differed according to CG. CG108 and CG499 isolates displayed specific heteroresistance to sulbactam and trimethoprim/sulfamethoxazole, respectively, which resulted in discrepant susceptibility results in microbroth versus agar-based antibiotic susceptibility tests modalities. We report an unusually high degree of CRAb phylogenetic diversity principally driven by emergent U.S. lineages harboring novel resistance elements that must be incorporated into diagnostic, surveillance, and preclinical research efforts.

Resistance and Co-Resistance of Metallo-Beta-Lactamase Genes in Diarrheal and Urinary-Tract Pathogens in Bangladesh.

Carbapenems are the antibiotics of choice for treating multidrug-resistant bacterial infections. Metallo-β-lactamases (MBLs) are carbapenemases capable of hydrolyzing nearly all therapeutically available beta-lactam antibiotics. Consequently, this research assessed the distribution of two MBL genes and three β-lactamases and their associated phenotypic resistance in diarrheal and urinary-tract infections (UTIs) to guide future policies. Samples were collected through a cross-sectional study, and β-lactamase genes were detected via PCR. A total of 228 diarrheal bacteria were isolated from 240 samples. The most predominant pathogens were Escherichia coli (32%) and Klebsiella spp. (7%). Phenotypic resistance to amoxicillin-clavulanic acid, aztreonam, cefuroxime, cefixime, cefepime, imipenem, meropenem, gentamicin, netilmicin, and amikacin was 50.4%, 65.6%, 66.8%, 80.5%, 54.4%, 41.6%, 25.7%, 41.2%, 37.2%, and 42.9%, respectively. A total of 142 UTI pathogens were identified from 150 urine samples. Klebsiella spp. (39%) and Escherichia coli (24%) were the major pathogens isolated. Phenotypic resistance to amoxicillin-clavulanic acid, aztreonam, cefuroxime, cefixime, cefepime, imipenem, meropenem, gentamicin, netilmicin, and amikacin was 93.7%, 75.0%, 91.5%, 93.7%, 88.0%, 72.5%, 13.6%, 44.4%, 71.1%, and 43%, respectively. Twenty-four diarrheal isolates carried blaNDM-1 or blaVIM genes. The overall MBL gene prevalence was 10.5%. Thirty-six UTI pathogens carried either blaNDM-1 or blaVIM genes (25.4%). Seven isolates carried both blaNDM-1 and blaVIM genes. MBL genes were strongly associated with phenotypic carbapenem and other β-lactam antibiotic resistance. blaOXA imparted significantly higher phenotypic resistance to β-lactam antibiotics. Active surveillance and stewardship programs are urgently needed to reduce carbapenem resistance in Bangladesh.

Genetic profile and characterization of antimicrobial resistance in Acinetobacter baumannii post-COVID-19 pandemic: a study in a tertiary hospital in Recife, Brazil.

To investigate the genetic profile and characterize antimicrobial resistance, including the main β-lactam antibiotic resistance genes, in Acinetobacterbaumannii isolates from a tertiary hospital in Recife-PE, Brazil, in the post-COVID-19 pandemic period. Acinetobacter baumannii isolates were collected between 2023 and 2024 from diverse clinical samples. Antimicrobial resistance testing followed standardized protocols, with β-lactamase-encoding genes detected via PCR and sequencing. Investigation into ISAba1 upstream of blaOXA-carbapenemase and blaADC genes was also conducted. Genetic diversity was assessed through ERIC-PCR. Among the 78 A. baumannii, widespread resistance to multiple antimicrobials was evident. Various acquired β-lactamase-encoding genes (blaOXA-23,-24,-58,-143, blaVIM, and blaNDM) were detected. Furthermore, this is the first report of blaVIM-2 in A. baumannii isolates harboring either the blaOXA-23-like or the blaOXA-143 gene in Brazil. Molecular typing revealed a high genetic heterogeneity among the isolates, and multi-clonal dissemination. The accumulation of genetic resistance determinants underscores the necessity for stringent infection control measures and robust antimicrobial stewardship programs to curb multidrug-resistant strains.

Molecular Characterization of Extended Spectrum β-Lactamase-Producing Escherichia coli: Insights into the O25b-ST131 Clone in Mexican Urinary Tract Infections

Background: The urgent need for antimicrobial research to address the escalating global challenge of β-lactam antibiotic resistance, particularly in Escherichia coli-induced urinary tract infections (UTI), is underscored by the increasing resistance to ciprofloxacin in Latin America. This issue has led to a heightened dependence on alternative therapeutics, such as cephalosporins. The identification of extended-spectrum β-lactamase (ESBL)-producing E. coli, notably the O25b-ST131 clone, adds complexity to UTI management. The prevalence of ESBL-producing E. coli varies globally due to factors including regional antimicrobial usage practices. Objectives: The goal of this study was to identify and molecularly characterize ESBL-producing E. coli isolates to identify the pandemic O25b-ST131 clone related to UTIs in one healthcare institution in Mexico. Methods: Bacterial species identification and antibiotic susceptibility tests were performed using the VITEK 2. The ESBL genes were identified using polymerase chain reaction (PCR). The E. coli genotyping was carried out by the phylogenetic group analysis and the O25b-ST131 identification. Results: A total of 86 unique E. coli isolates were confirmed as ESBL, and 75% were obtained from UTIs. The most prevalent β-lactamase genes were blaCTX-M (66%), blaTEM (8.1%), blaCTX-M/SHV (5.8%), blaCTX-M/TEM (4.6%), and blaSHV (2.3%). The B2 phylogroup was most prominent (54.4%), with 46.5% identified as a globally pandemic O25b-ST131 clone. No evident relationship was observed using random amplified polymorphic DNA (RAPD) between nosocomial and community-acquired infections in ESBL-producing E. coli isolates. Conclusions: The obtained findings highlight the significance of monitoring molecular epidemiology in antibiotic resistance profiles of the O25b-ST131 E. coli clone.

Epidemiological investigation and β-lactam antibiotic resistance of Riemerella anatipestifer isolates with waterfowl origination in Anhui Province, China

Riemerella anatipestifer (R. anatipestifer) is a highly pathogenic and complex serotypes waterfowl pathogen with inherent resistance to multiple antibiotics. This study was aimed to investigate the antibiotic resistance characteristics and genomic features of R. anatipestifer isolates in Anhui Province, China in 2023. A total of 287 cases were analysed from duck farms and goose farms, and the R. anatipestifer isolates were subjected to drug resistance tests for 30 antimicrobials. Whole genome sequencing (WGS) and bioinformatics analysis were performed on the bacterial genomes, targeting the β-lactam resistance genes. The results showed that a total of 74 isolates of R. anatipestifer were isolated from 287 cases, with a prevalence of 25.8%. The antimicrobial susceptibility testing (AST) revealed that all the 74 isolates were resistant to multiple drugs, ranging from 13 to 26 kinds of drugs. Notably, these isolates showed significant resistance to aminoglycosides and macrolides, which are also commonly used in clinical practices. Data revealed the presence of several β-lactamase-related genes among the isolates, including a novel blaRASA-1 variant (16.2%), the class A extended-spectrum β-lactamase blaRAA-1 (12.2%), and a blaOXA-209 variant (98.6%). Functional analysis of the variants blaRASA-1 and blaOXA-209 showed that the blaRASA-1 variant exhibited activity against various β-lactam antibiotics while their occurrence in R. anatipestifer were not common. The blaOXA-209 variant, on the other hand, did not perform any β-lactam antibiotic resistance. Furthermore, we observed that blaRAA-1 could undergo horizontal transmission among different bacteria via the insertion sequence IS982. In conclusion, this study delves into the high prevalence of R. anatipestifer infection in waterfowl in Anhui, China. The isolated strains exhibit severe drug resistance issues, closely associated with the prevalence of antibiotic resistance genes (ARG). Additionally, our research investigates the β-lactam antibiotic resistance mechanism in R. anatipestifer.

Analysis of Bacterial Communities and Antibiotic Resistance Genes in the Aquaculture Area of Changli County

In order to understand the distribution of microorganisms and various antibiotic resistance genes in the aquaculture area of Changli County, Qinhuangdao, high-throughput sequencing technology was used in this study. We utilized 16S rDNA gene sequencing and metagenome sequencing methods to analyze the seawater, sediment, and gut contents of the local fish Synechogobius hasta in the aquaculture area in spring. The results showed that Proteobacteria, Firmicutes, and Bacteroidota were the dominant bacteria in seawater; and Proteobacteria, Crenarchaeota, Acidobacter, and Actinobaciota were rich in the sediment; whereas Proteobacteria, Cyanobacteria, Firmicutes, and Bacteroidota were in relatively high abundance in fish gut contents. The microbial diversity of sediment samples was the most abundant, followed by seawater samples, and the microbial diversity of fish intestinal contents was the lowest. Moreover, the microbial diversity of similar samples was relatively similar, and the microbial diversity of different types of samples was quite different. For samples at different sites, there were significant differences between seawater samples at each site, and there were small differences between sediment samples at each site, and some sediment sample groups did not have significant differences in microbial composition. In all sample groups, five β-lactam antibiotic resistance genes (blaOXA-325, cepS, blaCARB-20, blaOXA-55, and blaTRU-1) and four aminoglycoside antibiotic resistance genes[aac(6')-IIb, amrA, aac(6')-Ie-aph(2″)-Ia, and aph(3')-Vc] were detected. There was also a certain correlation between antibiotic resistance genes and microbial communities.

Prevalence, molecular characterization, and antimicrobial resistance among Escherichia coli, Salmonella spp., and Staphylococcus aureus strains isolated from Egyptian broiler chicken flocks with omphalitis.

Bacterial Omphalitis has been reported as a significant cause of mortalities in newly hatched broiler chicks. This study aimed to assess the occurrence of omphalitis among broiler chickens in Gharbia governorate in Egypt. In addition, the bacteria associated with the occurrence of omphalitis in broiler chickens were also investigated and characterized. For this purpose, 43 farms in that area were surveyed. The comparative levels of omphalitis caused by Escherichia coli (E. coli), Salmonella spp., and Staphylococcus aureus (S. aureus) were screened in 129 chicks. The drug resistance to eight commonly used antimicrobials in Egyptian poultry farms was screened using the disk diffusion method. The overall incidence rate of omphalitis was 37.21%. In birds with omphalitis, the co-prevalence of S. aureus, Salmonella spp., and E. coli was 87.5%. When compared to healthy flocks, broiler chicks with omphalitis caused by Salmonella spp., E. coli, and S. aureus had a greater mortality rate in the first week of life. However, there were no significant differences in the mortality cases caused by these pathogens. Eighty-seven percent of the cases of omphalitis were linked to E. coli and 75% to Salmonella spp. and S. aureus. From the yolk sac of broiler chicks with omphalitis, E. coli, Salmonella spp., and S. aureus were isolated at rates of 87.5%, 62.5%, and 45.8%, respectively. The isolates of E. coli and Salmonella spp. exhibited great sensitivity to gentamycin and Tetracycline; however, the strongest drug resistance was observed toward cefpodoxime, sulphamethoxazole and trimethoprim, ampicillin, and amoxycillin and clavulanic acid. The recovered isolates of S. aureus showed susceptibility to chloramphenicol (72.37%), oxytetracycline (81.82%), and erythromycin (81.82%). However, every S. aureus isolate that was found resistant to amoxycillin and clavulanic acid, penicillin G and oxacillin. of blaTEM, blaSHV, and blaCTX-M genes has been proposed as the genetic cause of β-lactam antibiotic resistance in Salmonella spp. and E. coli. MecA and blaZ; however, were found in every strain of S. aureus. The frequency of omphalitis and its associated mortalities was comparatively high in Gharbia governorate. More efforts should be made to adopt strict hygienic standards for controlling and preventing such disease and this will consequently lead to minimizing the use of antimicrobials in poultry farms.

Molecular Profile of Metallo-β-Lactamase Producing Bacterial Isolates from Clinical Samples; South-South Nigeria Perspective

One of the major clinical problems regarding β-lactam antibiotics resistance is attributed to metallo-beta-lactamases (MβL), which are a group of enzymes that is a subset of beta- lactamases belonging to group B of the Ambler classification, which causes hydrolysis of carbapenems. The study was conducted to check the prevalence of MβL and its genes (IMP, VIM, and NDM) among Gram-negative isolates. Methods. 312 clinical samples (urine and wound) were cultured, and antimicrobial susceptibility testing was performed using the conventional disk diffusion method. MβL-phenotypic detection was uncovered by standard bacteriological techniques, MβL genes were amplified using pre-determined conditions set on an AB19700 Applied Biosystem thermal cycler. Results. 157 (56.1%) Gram-negative and 123 (43.9%) Gram-positive were isolated. Escherichia coli 32 (11.4%) and Pseudomonas aeruginosa 32 (11.4%) were the most predominant. Providencia stuartii 3 (1.1%), Klebsiella ornitholytica 2 (0.7%), and Stenotrophomonas maltophilia 1 (0.4%) were some of the less predominant isolates. Imipenem and Ertapenem were the most sensitive, while Gentamicin, Amoxicillin-Clavulanate, and Ceftriaxone were the most resistant. Twelve species (7.6%) were identified as MβL producers. The VIM gene (12: 100%) was the predominant gene, followed by the NDM gene (6: 50%) and the IMP gene (2: 16.7%). Conclusions. The detection of blaVIM, blaNDM, and blaIMP genes in South-south Uyo is really worrisome, and proper infectious control measures should be taken in order to prevent outbreaks of MβL-producing Gram-negative bacteria isolated in Uyo, South South Nigeria.

Mechanisms of total phosphorus removal and reduction of β-lactam antibiotic resistance genes by exogenous fungal combination activated sludge

This study utilized Trichoderma and activated sludge to construct combined activated sludge (TAS). The metagenomic approach was employed to examine the shifts in microbial community structure and function of TAS under amoxicillin stress and investigate the mechanism underlying the reduction of β-lactam antibiotic resistance genes (β-ARGs). The findings demonstrated that the elevated aundance of glpa, glpd, ugpq, glpq, and glpb were primarily responsible for the reduction in total phosphorus (TP) removal by TAS. The increased abundance of Proteobacteria and Verrucomicrobia led to enhanced expression of ugpb, phnd, and phne, thereby improving the TP removal of TAS. Furthermore, antibiotic inactivation has gradually become the primary antibiotic resistance mechanism in TAS. Specifically, an increase in the abundance of OXA-309 in TAS will decrease the probability of amoxicillin accumulation in TAS. A decrease in β-ARGs diversity confirmed this. This study presents a novel approach to reducing antibiotic and ARG accumulation in sludge.

A Review of the Resistance Mechanisms for β-Lactams, Macrolides and Fluoroquinolones among Streptococcus pneumoniae.

Streptococcus pneumoniae (S. pneumoniae) is a bacterial species often associated with the occurrence of community-acquired pneumonia (CAP). CAP refers to a specific kind of pneumonia that occurs in individuals who acquire the infection outside of a healthcare setting. It represents the leading cause of both death and morbidity on a global scale. Moreover, the declaration of S. pneumoniae as one of the 12 leading pathogens was made by the World Health Organization (WHO) in 2017. Antibiotics like β-lactams, macrolides, and fluoroquinolones are the primary classes of antimicrobial medicines used for the treatment of S. pneumoniae infections. Nevertheless, the efficacy of these antibiotics is diminishing as a result of the establishment of resistance in S. pneumoniae against these antimicrobial agents. In 2019, the WHO declared that antibiotic resistance was among the top 10 hazards to worldwide health. It is believed that penicillin-binding protein genetic alteration causes β-lactam antibiotic resistance. Ribosomal target site alterations and active efflux pumps cause macrolide resistance. Numerous factors, including the accumulation of mutations, enhanced efflux mechanisms, and plasmid gene acquisition, cause fluoroquinolone resistance. Furthermore, despite the advancements in pneumococcal vaccinations and artificial intelligence (AI), it is not feasible for individuals to rely on them indefinitely. The ongoing development of AI for combating antimicrobial resistance necessitates more research and development efforts. A few strategies can be performed to curb this resistance issue, including providing educational initiatives and guidelines, conducting surveillance, and establishing new antibiotics targeting another part of the bacteria. Hence, understanding the resistance mechanism of S. pneumoniae may aid researchers in developing a more efficacious antibiotic in future endeavors.

Changes in the behavior of Staphylococcus aureus strains in the presence of oxacillin under the effect of gamma radiation

Staphylococcus aureus (S. aureus) as a major pathogen is implicated in a wide range of foodborne and hospital-acquired infections, its methicillin resistant variants contribute to the spread of β-lactam antibiotic resistance. It is essentially important to destroy these pathogens, their resistance genes and the antibiotics in wastewaters. For this purpose reactions of reactive radicals (advanced oxidation processes), first of all hydroxyl radicals (•OH), are suggested. Here the radiolysis of water supplied these radicals. In the experiments B.01755 oxacillin sensitive and B.02174 resistant S. aureus strains were used to study their behaviorr in suspensions under the effect of irradiation in presence and absence of oxacillin. Oxacillin inactivation depended on concentration of the antibiotic used (0.042 and 1 g dm−3), higher concentration required a higher dose. When 106–109 CFU cm−3 S. aureus suspensions were irradiated with γ-radiation the bacteria were inactivated at low absorbed doses: 4 orders of magnitude decrease ocurred in the number of culturable cells at ∼0.6 kGy dose. Both cell membrane and DNA suffered considerable damages during irradiation. Due to the membrane damage the cells could not be stained, and the DNA content of cells in several days period was released into the solution. In DNA damage the oxacillin resistance mecA gene was also modified, it did not multiply in PCR test. These findings are important from the point of view of applying irradiation technology to stop the spread of antibiotic resistance.

Multidrug-resistant Enterobacter spp. in wastewater and surface water: Molecular characterization of β-lactam resistance and metal tolerance genes

Among the ESKAPE group pathogens, Enterobacter spp. is an opportunistic Gram-negative bacillus, widely dispersed in the environment, that causes infections. In the present study, samples of hospital wastewater, raw and treated urban wastewater, as well as surface receiving water, were collected to assess the occurrence of multidrug-resistant (MDR) Enterobacter spp. A molecular characterization of β-lactam antibiotic resistance and metal tolerance genes was performed. According to identification by MALDI-TOF MS, 14 isolates were obtained: 7 E. bugandensis, 5 E. kobei, and 2 E. cloacae. The isolates showed resistance mainly to β-lactam antibiotics, including those used to treat infections caused by MDR bacteria. Multiple antibiotic resistance index was calculated for all isolates. It allowed verify whether sampling points showed a high risk due to antibiotic resistant Enterobacter spp., as well as to determine if the isolates have been in environments with a frequent antibiotic use. Twelve isolates showed β-lactam antibiotic resistance gene, being the blaKPC widely detected. Regarding metal tolerance, 13 isolates showed at least two genes that encode metal tolerance mechanisms. Overall, metal tolerance mechanisms to silver, copper, mercury, arsenic and tellurium were found. New data on metal tolerance mechanisms dispersion and antibiotic-resistance characterization of the E. bugandensis and E. kobei species were here provided. The occurrence of MDR Enterobacter spp. in analyzed samples draws attention to an urgent need to put control measures into practice. It also evidences waterborne spread of clinically important antibiotic-resistant bacteria recognized as critical priority pathogens.

Down-regulation of β-lactam antibiotics resistance and biofilm formation by Staphylococcus epidermidis is associated with isookanin.

Biofilm formation is the major pathogenicity of Staphylococcus epidermidis (S. epidermidis), which enhances bacterial resistance to antibiotics. Isookanin has potential inhibitory activity on biofilm. The inhibiting mechanisms of isookanin against biofilm formation through surface hydrophobicity assay, exopolysaccharides, eDNA, gene expression analysis, microscopic visualization, and molecular docking were explored. Additionally, the combination of isookanin and β-lactam antibiotics were evaluated by the broth micro-checkerboard assay. The results showed that isookanin could decrease the biofilm formation of S. epidermidis by ≥85% at 250 μg/mL. The exopolysaccharides, eDNA and surface hydrophobicity were reduced after treatment with isookanin. Microscopic visualization analysis showed that there were fewer bacteria on the surface of the microscopic coverslip and the bacterial cell membrane was damaged after treatment with isookanin. The down-regulation of icaB and up-regulation of icaR were observed after treatment with isookanin. Additionally, the RNAIII gene was significantly up-regulated (p < 0.0001) at the mRNA level. Molecular docking showed that isookanin could bind to biofilm-related proteins. This indicated that isookanin can affect biofilm formation at the initial attachment phase and the aggregation phase. The FICI index showed that the combination of isookanin and β-lactam antibiotics were synergistic and could reduce doses of antibiotics by inhibiting biofilm formation. This study improved the antibiotic susceptibility of S. epidermidis through inhibition of the biofilm formation, and provided a guidance for the treatment of antibiotic resistance caused by biofilm.

Periodontal pathogens and antibiotic resistance genes in individuals with chronic generalized periodontitis

Relevance. Considering the role of personalized medicine in dental practice, the accumulation of knowledge about the genetic determinants of bacterial resistance and the use of antibacterial drugs, the learning of periodontal microbiota, sensitivity to antimicrobial drugs, the identification of key periodontal pathogens will allow predicting the development mechanisms of inflammatory periodontal diseases and monitoring and prescribing effective antibacterial therapy.Aim. The study aimed to determine the prevalence of pathogens and the occurrence of antibiotic resistance genes in individuals with chronic generalized periodontitis (CGP).Materials and methods. Clinical and laboratory examinations studied 163 subjects aged 18 to 45 years, of which there were 100 patients with inflammatory periodontal diseases and 63 subjects with intact periodontium. The study obtained periodontal pocket and gingival crevice swabs. The real-time PCR isolated marker bacteria and resistance genes to glycopeptide and β-lactam antibiotics.Results. The patients with chronic periodontitis demonstrated a periodontal pathogen detection rate of 96.4 %. Among the isolated periodontal pathogens, bacteria of the red complex were the most common: T. forsythia (81%; p &lt; 0.001), T. denticola (63%; p = 0.054) and P. gingivalis (69%; p &lt; 0.001). In healthy individuals with intact periodontium, P. gingivalis (12.7%), T. denticola (47.62%), and T. forsythia (36.51%) prevailed in the studied material, i.e., gingival fluid. The mean ratio of bone loss in relation to the root length (the Fuchs Index) was 0.83 ± 0.03 in patients with mild CGP and 0.71 ± 0.05 with moderate CGP. The β-lactam antibiotic resistance genes appeared to occur frequently (%). So, TEM and SHV genes were in 72% and 26%. The control group demonstrated the TEM gene in 41.27% (p &lt; 0.001) and the SHV gene in 4.76% (p &lt; 0.001).The group with CGP appeared to have resistance genetic markers: MecA to cephalosporins (15%) and OXA-51 to carbapenems (9%). The control group detected MecA (6.35%; p = 0.0948), while OXA-51 markers were absent (p = 0.014). Both groups did not show resistance genes to other antibiotic groups (AB).Conclusion. The "red complex" microorganisms T. forsythia, T. denticola and P. gingivalis, which were the most frequent during the progression of bone destruction, appeared to play the leading role in the onset and progression of inflammatory periodontal diseases.The oral microbiome can serve as a reservoir for the transfer of resistance genes: the study results indicate a high incidence rate (%) of β-lactam antibiotic resistance genes in the group of patients with chronic periodontitis. The group with chronic periodontitis revealed TEM and SHV genes in 72% and 26%, respectively. The group with intact periodontium also demonstrated a high occurrence rate of the TEM gene in 58.3 % of cases.

Tautomer-Specific Deacylation and Ω-Loop Flexibility Explain the Carbapenem-Hydrolyzing Broad-Spectrum Activity of the KPC-2 β-Lactamase.

KPC-2 (Klebsiella pneumoniae carbapenemase-2) is a globally disseminated serine-β-lactamase (SBL) responsible for extensive β-lactam antibiotic resistance in Gram-negative pathogens. SBLs inactivate β-lactams via a mechanism involving a hydrolytically labile covalent acyl-enzyme intermediate. Carbapenems, the most potent β-lactams, evade the activity of many SBLs by forming long-lived inhibitory acyl-enzymes; however, carbapenemases such as KPC-2 efficiently deacylate carbapenem acyl-enzymes. We present high-resolution (1.25-1.4 Å) crystal structures of KPC-2 acyl-enzymes with representative penicillins (ampicillin), cephalosporins (cefalothin), and carbapenems (imipenem, meropenem, and ertapenem) obtained utilizing an isosteric deacylation-deficient mutant (E166Q). The mobility of the Ω-loop (residues 165-170) negatively correlates with antibiotic turnover rates (kcat), highlighting the role of this region in positioning catalytic residues for efficient hydrolysis of different β-lactams. Carbapenem-derived acyl-enzyme structures reveal the predominance of the Δ1-(2R) imine rather than the Δ2 enamine tautomer. Quantum mechanics/molecular mechanics molecular dynamics simulations of KPC-2:meropenem acyl-enzyme deacylation used an adaptive string method to differentiate the reactivity of the two isomers. These identify the Δ1-(2R) isomer as having a significantly (7 kcal/mol) higher barrier than the Δ2 tautomer for the (rate-determining) formation of the tetrahedral deacylation intermediate. Deacylation is therefore likely to proceed predominantly from the Δ2, rather than the Δ1-(2R) acyl-enzyme, facilitated by tautomer-specific differences in hydrogen-bonding networks involving the carbapenem C-3 carboxylate and the deacylating water and stabilization by protonated N-4, accumulating a negative charge on the Δ2 enamine-derived oxyanion. Taken together, our data show how the flexible Ω-loop helps confer broad-spectrum activity upon KPC-2, while carbapenemase activity stems from efficient deacylation of the Δ2-enamine acyl-enzyme tautomer.

PREVALENCE OF MULTIDRUG RESISTANT ESCHERICHIA COLI AND KLEBSIELLA PNEUMONIAE SPECIES ISOLATED FROM URINE SAMPLES OF PATIENTS AT ALEX EKWUEME FEDERAL UNIVERSITY TEACHING HOSPITAL ABAKALIKI, EBONYI STATE, NIGERIA

Aim and Objective: In hospitals and community, morbidity and mortality are attributed to urinary tract infections (UTIs). This study investigated the prevalence of multi-drug resistant isolates of Escherichia coli and Klebsiella species from urine samples of patients visiting Alex Ekwueme Federal University Teaching Hospital Abakaliki (AE-FUTHA), Ebonyi State. Method: With the use of standard microbiological and biochemical techniques for analysis, a total of 300 mid-stream samples of urine were collected in sterile bottles. Phynotype screening for extended spectrum beta lactamase (ESBL) production was achieved by double disc synergy test (DDST). Disc diffusion method was used to check for ESBL producing bacteria susceptible to antibiotics. With specific primers, the presence of temoniera (TEM) and sulfhydryl variable (SHV) beta lactamases genes was determined using polymerase chain reaction (PCR). Results: 88 isolates of E coli and Klebsiella species were isolated from the urine samples; 29 were E coli and 59 were K. pneumonia species. 47 ESBL positive isolates were identified with E. coli, 19 (40%) and Klebsiella, 28 (60%). Escherichia coli isolated from GOPD patients, gynecology, and men's surgery ward were 100% resistant to ofloxacin, ceftazidime, amoxicillin, nitrofurantoin, chloramphenicol, and aztreonam, while Klebsiella species isolated from gynecology department, maternity ward, and psychiatric ward were 100% resistant to ofloxacin, Nitrofurantoin and chloramphenicol. Multiple antibiotics resistance index (MARI) of E. coli and Klebsiella species isolated recorded an average of 0.64 for E. coli and 0.41 for Klebsiella species.The molecular analysis revealed that 44.4% of SHV beta lactamase and 65.6% TEM-type β-lactamase genes were present in ESBL producing E. coli while 54.5% of SHV beta lactamase gene and 45.5% TEM-type β-lactamase genes were present in ESBL producing Klebsiella species. Conlusion: In conclusion, TEM and SHV-type β-lactamase genes are the primary cause of β-lactam antibiotic resistance in E. Coli and Klebsiella species resulting in increased infections caused by organisms harboring the ESBL gene. Nitrofurantoin, ceftazidime, cefalexin, and cefotaxime may be the antibiotic of choice in the treatment of UTIs. Peer Review History: Received: 1 January 2023; Revised: 14 February; Accepted: 7 March 2023, Available online: 15 March 2023 Academic Editor: Dr. Amany Mohamed Alboghdadly, Princess Nourah bint abdulrahman university, Riyadh, amalbgadley@pnu.edu.sa Received file: Reviewer's Comments: Average Peer review marks at initial stage: 5.0/10 Average Peer review marks at publication stage: 7.0/10 Reviewers: Prof. Hassan A.H. Al-Shamahy, Sana'a University, Yemen, shmahe@yemen.net.ye Dr. Tamer Elhabibi, Suez Canal University, Egypt, tamer_hassan@pharm.suez.edu.eg Similar Articles: ANALYSIS OF THE ANTIBIOGRAM PROFILES OF BIOFILM FORMING STAPHYLOCOCCUS AUREUS AND ESCHERICHIA COLI

Investigation of bacterial and fungal population structure on environmental surfaces of three medical institutions during the COVID-19 pandemic.

To evaluate the population structure of environmental bacteria and fungi in three different types of medical institutions and the potential risks due to antibiotic resistance during the coronavirus disease 2019 (COVID-19) pandemic. One hundred twenty-six environmental surface samples were collected from three medical institutions during the COVID-19 pandemic. A total of 6,093 and 13,514 representative sequences of 16S and ITS ribosomal RNA (rRNA) were obtained by amplicon sequencing analysis. The functional prediction was performed using the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States tool based on the Greengenes database and the FAPROTAX database. On environmental surfaces in three medical institutions during the COVID-19 pandemic, Firmicutes (51.6%) and Bacteroidetes (25%) were the dominant bacteria, while Ascomycota (39.4%) and Basidiomycota (14.2%) were the dominant fungi. A number of potential bacterial and fungal pathogens were successfully identified by the metagenomic approach. Furthermore, compared with the bacterial results, the fungi showed a generally closer Bray Curtis distance between samples. The overall ratio of Gram-negative bacteria to Gram-positive bacteria was about 3:7. The proportion of stress-tolerant bacteria in medical institutions A, B and C reached 88.9, 93.0 and 93.8%, respectively. Anaerobic bacteria accounted for 39.6% in outdoor environments, 77.7% in public areas, 87.9% in inpatient areas and 79.6% in restricted areas. Finally, the β-Lactam resistance pathway and polymyxin resistance pathway were revealed through functional prediction. We described the microbial population structure changes in three different types of medical institutions using the metagenomic approach during the COVID-19 pandemic. We found that the disinfection measures performed by three healthcare facilities may be effective on the "ESKAPE" pathogens, but less effective on fungal pathogens. Moreover, emphasis should be given to the prevention and control of β-lactam and polymyxin antibiotics resistance bacteria during the COVID-19 pandemic.

Genome Sequence Analysis of a Wohlfahrtiimonas chitiniclastica Strain Isolated from a Septic Wound of a Hospitalized Patient in Uganda

We report a genome sequence of Wohlfahrtiimonas chitiniclastica strain MUWRP0946, isolated from a hospitalized patient in Uganda. The genome size was 2.08 million bases, and the genome completeness was 94.22%. The strain carries tetracycline, folate pathway antagonist, β-lactam, and aminoglycoside antibiotic resistance genes.

Beta-Lactam Antibiotic Resistance Genes in the Microbiome of the Public Transport System of Quito, Ecuador.

Multidrug-resistant bacteria present resistance mechanisms against β-lactam antibiotics, such as Extended-Spectrum Beta-lactamases (ESBL) and Metallo-β-lactamases enzymes (MBLs) which are operon encoded in Gram-negative species. Likewise, Gram-positive bacteria have evolved other mechanisms through mec genes, which encode modified penicillin-binding proteins (PBP2). This study aimed to determine the presence and spread of β-lactam antibiotic resistance genes and the microbiome circulating in Quito's Public Transport (QTP). A total of 29 station turnstiles were swabbed to extract the surface environmental DNA. PCRs were performed to detect the presence of 13 antibiotic resistance genes and to identify and to amplify 16S rDNA for barcoding, followed by clone analysis, Sanger sequencing, and BLAST search. ESBL genes blaTEM-1 and blaCTX-M-1 and MBL genes blaOXA-181 and mecA were detected along QPT stations, blaTEM being the most widely spread. Two subvariants were found for blaTEM-1, blaCTX-M-1, and blaOXA-181. Almost half of the circulating bacteria found at QPT stations were common human microbiota species, including those classified by the WHO as pathogens of critical and high-priority surveillance. β-lactam antibiotic resistance genes are prevalent throughout QPT. This is the first report of blaOXA-181 in environmental samples in Ecuador. Moreover, we detected a new putative variant of this gene. Some commensal coagulase-negative bacteria may have a role as mecA resistance reservoirs.

Structural basis of broad-spectrum β-lactam resistance in Staphylococcus aureus

Broad-spectrum β-lactam antibiotic resistance in Staphylococcus aureus is a global healthcare burden1,2. In clinical strains, resistance is largely controlled by BlaR13, a receptor that senses β-lactams through the acylation of its sensor domain, inducing transmembrane signalling and activation of the cytoplasmic-facing metalloprotease domain4. The metalloprotease domain has a role in BlaI derepression, inducing blaZ (β-lactamase PC1) and mecA (β-lactam-resistant cell-wall transpeptidase PBP2a) expression3–7. Here, overcoming hurdles in isolation, we show that BlaR1 cleaves BlaI directly, as necessary for inactivation, with no requirement for additional components as suggested previously8. Cryo-electron microscopy structures of BlaR1—the wild type and an autocleavage-deficient F284A mutant, with or without β-lactam—reveal a domain-swapped dimer that we suggest is critical to the stabilization of the signalling loops within. BlaR1 undergoes spontaneous autocleavage in cis between Ser283 and Phe284 and we describe the catalytic mechanism and specificity underlying the self and BlaI cleavage. The structures suggest that allosteric signalling emanates from β-lactam-induced exclusion of the prominent extracellular loop bound competitively in the sensor-domain active site, driving subsequent dynamic motions, including a shift in the sensor towards the membrane and accompanying changes in the zinc metalloprotease domain. We propose that this enhances the expulsion of autocleaved products from the active site, shifting the equilibrium to a state that is permissive of efficient BlaI cleavage. Collectively, this study provides a structure of a two-component signalling receptor that mediates action—in this case, antibiotic resistance—through the direct cleavage of a repressor.