The Increased Prevalence of rmpA Gene in Klebsiella pneumoniae Isolates Coharboring blaNDM and blaOXA-48-like Genes.

The emergence of carbapenemase-producing Klebsiella pneumoniae poses a substantial risk to public health. It is essential to comprehend the influence of carbapenemase on the virulence characteristics of K. pneumoniae in order to devise successful strategies for combating these infections. In this study, we explored the distribution disparity of virulence determinants between carbapenemase-producing (CP-Kp, n = 52) and carbapenemase-nonproducing (CN-Kp, n = 43) isolates. The presence of carbapenemases was detected via the modified carbapenem inactivation method and confirmed by PCR. The New Delhi metallo-ß-lactamase (blaNDM) and Oxacillinase-48-like (blaOXA-48-like) genes were the most prevalent (94.23% and 76.92%, respectively) in CP-Kp isolates. Coexistence of blaNDM and blaOXA-48-like was observed in 71.15% of isolates, whereas 5.77% coharbored blaNDM and blaKPC. PCR analysis revealed the presence of several virulence genes, including adhesins (fimH, 92.63%, mrkD, 97.89%), capsule-associated virulence (uge, 90.53%), the K2 capsule serotype (k2, 6.32%), the iron acquisition system (kfu, 23.16%), and the regulator of mucoid phenotype (rmpA, 28.42%). A significantly higher prevalence of rmpA was detected in the CP-Kp compared with the CN-Kp (24/52 vs. 3/43, p < 0.0001), indicating a potential association between rmpA and carbapenemase acquisition. In addition, the majority of rmpA (22/24) positive isolates in the CP-Kp isolates coharbored blaNDM and either blaOXA-48-like or blaKPC.

Investigating the relationship between carbapenemase production and biofilm formation in Klebsiella pneumoniae clinical isolates.

OBJECTIVE: Carbapenemase production and biofilm formation in K. pneumoniae are crucial factors influencing the pathogenicity and antibiotic resistance of this bacterium. This study investigated the interplay between carbapenemase production and biofilm formation in K. pneumoniae clinical isolates. RESULTS: The distribution of biofilm-forming ability significantly differed between carbapenemase-producing (CP-Kp) (n = 52) isolates and carbapenemase-nonproducing (CN-Kp) isolates (n = 37), suggesting a potential link between carbapenemase production and biofilm formation. All the blaNDM-1-harbouring isolates demonstrated biofilm formation, with varying levels classified as strong (33.33%), moderate (22.22%), or weak (44.45%). blaNDM-1 and blaKPC-coharbouring isolates did not exhibit strong or moderate biofilm formation. blaNDM-1 and blaOXA-48-coharbouring isolates were predominantly moderate (48.65%), followed by weak (32.43%), with none showing strong biofilm production. These findings suggest a correlation between the presence of carbapenemases and biofilm-forming ability; however, the heterogeneity in biofilm-forming abilities associated with different carbapenemase types and the absence of strong biofilm producers in the detected carbapenemase combinations prompt a closer look at the complex regulatory mechanisms governing biofilm formation in CP-Kp isolates.

Genome Analysis of Pseudomonas aeruginosa Strains from Chronically Infected Patients with High Levels of Persister Formation.

The appearance of persister cells with low metabolic rates are key factors leading to antibiotic treatment failure. Such persisters are multidrug tolerant and play a key role in the recalcitrance of biofilm-based chronic infections. Here, we present the genomic analyses of three distinct Pseudomonas aeruginosa Egyptian persister-isolates recovered from chronic human infections. To calculate the persister frequencies, viable counts were determined before and after treatment with levofloxacin. The susceptibilities of isolates to different antibiotics were determined using the agar-dilution method. To determine their recalcitrance, the levofloxacin persisters were further challenged with lethal concentrations of meropenem, tobramycin, or colistin. Furthermore, the biofilm formation of the persister strains was estimated phenotypically, and they were reported to be strong biofilm-forming strains. The genotypic characterization of the persisters was performed using whole genome sequencing (WGS) followed by phylogenetic analysis and resistome profiling. Interestingly, out of the thirty-eight clinical isolates, three isolates (8%) demonstrated a persister phenotype. The three levofloxacin-persister isolates were tested for their susceptibility to selected antibiotics; all of the tested isolates were multidrug resistant (MDR). Additionally, the P. aeruginosa persisters were capable of surviving over 24 h and were not eradicated after exposure to 100X-MIC of levofloxacin. WGS for the three persisters revealed a smaller genome size compared to PAO1-genome. Resistome profiling indicated the presence of a broad collection of antibiotic-resistance genes, including genes encoding for antibiotic-modifying enzymes and efflux pump. Phylogenetic analysis indicated that the persister isolates belong to a distinct clade rather than the deposited P. aeruginosa strains in the GenBank. Conclusively, the persister isolates in our study are MDR and form a highly strong biofilm. WGS revealed a smaller genome that belongs to a distinct clade.

Elimination of multidrug-resistant Proteus mirabilis biofilms using bacteriophages.

Proteus mirabilis is responsible for a wide range of infections that affect the urinary tract, the respiratory tract, burns, wounds and the feet of individuals with diabetes. They are highly resistant to antimicrobial agents, and new therapeutic options are therefore needed to combat this pathogen. The use of bacteriophages is one option that may be useful in treating multidrug-resistant (MDR) Proteus mirabilis infections, especially biofilm-based infections. The aim of this study was to control biofilms formed by MDR Proteus mirabilis using bacteriophages. Proteus mirabilis isolates were identified based on biochemical tests, and their resistance profiles were determined by the disk diffusion method. The biofilm-forming capacity of the isolates was assessed by the spectrophotometric method. Bacteriophages attacking Proteus mirabilis were isolated from sewage. The effect of phage on biofilm formation was investigated by the viable count method. A high rate of drug resistance was found (87.2%). Strong biofilm formation was observed in 80.5% of isolates, while moderate production was found in 19.5%. Five bacteriophages were isolated from sewage and were tested for their ability to eliminate biofilms. Significant disruption of pre-formed biofilms was observed that reached up to 99.9% decrease in the number of viable cells. The use of bacteriophages is considered a promising strategy against the biofilm infections caused by MDR Proteus mirabilis isolates.

Integron occurrence is linked to reduced biocide susceptibility in multidrug resistant Pseudomonas aeruginosa.

OBJECTIVE: Integrons are gene acquisition systems commonly found in bacterial genomes that play a major role in the dissemination of resistance to antibiotics. This work aimed to study the relationship between the presence of integrons and the reduced susceptibility of multidrug-resistant (MDR) Pseudomonas aeruginosa isolates towards different groups of biocides. METHODS: The antimicrobial susceptibility patterns of 104 clinical isolates were determined against different antibiotics by the disk diffusion method. The isolates were also tested for their susceptibility to six biocides (glutaraldehyde, benzalkonium chloride, cetrimide, chlorhexidine gluconate, chlorocresol and gluconate, and phenyl mercuric nitrate) by agar dilution. The presence of integrons and resistance genes in MDR isolates were detected by polymerase chain reaction. RESULTS: Thirty-six Pseudomonas isolates were MDR, and the majority of these isolates showed reduced susceptibility to biocides. In the MDR isolates, Class I integron was detected in 22 isolates (61.1%), while Class II and III integrons were identified in only four isolates (11.1%), In addition, aacA4 and qacE genes were detected in 22 (61.1%) and 11 (30.5%) isolates, respectively. Integron I-positive isolates showed reduced susceptibility to tested biocides. CONCLUSIONS: The current study reveals the presence of different classes of integrons, with class I being predominant. Class I integron may be responsible for generating MDR P. aeruginosa isolates with reduced susceptibility to biocides. This linkage between integrons and biocide resistance in MDR-Pseudomonas isolates is notable and could be clinically important. Strict antibiotic prescription policies and the adequate use of biocides could help in controlling this problem.

Potential biological indicators for glutaraldehyde and formaldehyde sterilization processes.

The present study aimed to isolate, select, and evaluate bacterial isolates with potential for use as biological indicators for sterilization with glutaraldehyde and/or formaldehyde. A total of 340 local Bacillus isolates were screened for glutaraldehyde and/or formaldehyde resistance by determination of minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and extinction time and were compared with B. subtilis (var. niger) ATCC 9372, the biological indicator for ethylene oxide sterilization, as reference. Of these, 85 isolates had glutaraldehyde MICs of 0.5% or higher, while 29 had formaldehyde MICs of 0.04% or higher. Of the 29 resistant isolates, 15 had MBCs of 0.05% or more. Extinction times were used to evaluate the bactericidal/sporicidal activity of glutaraldehyde. Eight had inactivation times of more than 5 h in 2% glutaraldehyde (pH 8), whereas 12 had inactivation times of more than 3 h in l% formaldehyde, with one isolate in common. These 19 isolates were selected and evaluated as potential biological indicators for aldehydes by determination of the decimal reduction times ( D values), compared with the reference strain. Eight glutaraldehyde-resistant isolates exhibited D values 2.0- to 3.5-fold higher than the reference strain (30 min.). Only five of 12 formaldehyde resistant isolates had D values higher than that of the reference strain. Using six resistant isolates, temperature coefficient values between 2.11 and 3.02 were obtained for 2% formaldehyde. Finally, 14 isolates were tested for potential pathogenicity and were identified to species level. All of the eight glutaraldehyde-resistant isolates, including the isolate with dual resistance, and three formaldehyde-resistant isolates were B. licheniformis, while two other formaldehyde-resistant isolates were B. cereus. Six of the selected B. licheniformis isolates are potential biological indicators for sterilization processes using aldehydes. Three can be suggested for glutaraldehyde only and three for both aldehydes.