Effect of sub-inhibitory concentrations of antibiotics on biofilm formation and expression of virulence genes in penicillin-resistant, ampicillin-susceptible Enterococcus faecalis

A novel endolysin from an Enterococcus faecalis phage and application

Enterococcus faecalis is the primary species detected in cases of secondary persistent infection resulting from root canal therapy failure. Due to the overuse of antibacterial agents, E. faecalis has developed resistance to these drugs, making it challenging to treat clinical diseases caused by E. faecalis infection. Therefore, there is an urgent need to explore new alternative drugs for treating E. faecalis infections. We aimed to clone and express the genes of phage endolysins, purify the recombinant proteins, and analyze their antibacterial activity, lysis profile, and ability to remove biofilm. The crude enzyme of phage endolysin pEF51 (0.715 mg/mL), derived from phage PEf771 infecting E. faecalis, exhibited superior bacterial inhibitory activity and a broader bactericidal spectrum than its parental phage PEf771. Furthermore, pEF51 demonstrated high efficacy in eliminating E. faecalis biofilm. Therapeutic results of the infected Sprague-Dawley (SD) rat model indicated that among 10 SD rats, only one developed a thoracic peritoneal abscess and splenic peritoneal abscess after 72 h of treatment with pEF51. This suggests that pEF51 could provide protection against E. faecalis infection in SD rats. Based on the 16S rDNA metagenomic data of the intestinal microbial community of SD rats, endolysin pEF51 exerted a certain influence on the diversity of intestinal microorganisms at the genus level. Thus, pEF51 may serve as a promising alternative to antibiotics in the management of E. faecalis infection.

A growing battlefield in the war against biofilm-induced antimicrobial resistance: insights from reviews on antibiotic resistance

Biofilms are a common survival strategy employed by bacteria in healthcare settings, which enhances their resistance to antimicrobial and biocidal agents making infections difficult to treat. Mechanisms of biofilm-induced antimicrobial resistance involve reduced penetration of antimicrobial agents, increased expression of efflux pumps, altered microbial physiology, and genetic changes in the bacterial population. Factors contributing to the formation of biofilms include nutrient availability, temperature, pH, surface properties, and microbial interactions. Biofilm-associated infections can have serious consequences for patient outcomes, and standard antimicrobial therapies are often ineffective against biofilm-associated bacteria, making diagnosis and treatment challenging. Novel strategies, including antibiotics combination therapies (such as daptomycin and vancomycin, colistin and azithromycin), biofilm-targeted agents (such as small molecules (LP3134, LP3145, LP4010, LP1062) target c-di-GMP), and immunomodulatory therapies (such as the anti-PcrV IgY antibodies which target Type IIIsecretion system), are being developed to combat biofilm-induced antimicrobial resistance. A multifaceted approach to diagnosis, treatment, and prevention is necessary to address this emerging problem in healthcare settings.

Resistance Profiles and Virulence Determinants in Biofilm-Forming Enterococcus faecium Isolated from Raw Seafood in Bangladesh

Pathogenic, antibiotic-resistant, and biofilm-forming bacteria can be transferred to humans through the consumption of contaminated seafood. The present study was carried out to determine antibiotic resistance profiles and virulence determinants in biofilm-forming Enterococcus faecium isolated from seafood in Bangladesh. A total of 150 seafood samples, including shrimp (n = 50), crabs (n = 25), and marine fish (n = 75), were screened using cultural, staining, biochemical, polymerase chain reaction (PCR), Congo red (CR), and disk diffusion (DD) assays. In PCR, E. faecium was detected in 27.3% (41/150; CI95% 20.8; 34.9) of samples, where marine fish (34.7%, CI95% 24.9; 45.9) had the highest prevalence (p < 0.05) compared to crabs (32%, CI95% 17.2; 51.6) and shrimp (14%, CI95% 7.0; 26.1). Thirty-two (78.1%, CI95% 63.3; 88.0) of the E. faecium isolates were determined to be biofilm formers in the CR test, where 43.9% (18/41, CI95% 29.9; 59.0) and 34.2% (14/41, CI95% 21.6; 49.5) of the isolates were strong and intermediate biofilm formers, respectively. In PCR, virulence genes, i.e., pil (100%), ace (92.7%), agg (68.3%), fsrA (65.9%), gelE (63.4%), sprE (53.7%), fsrB (51.2%), and fsrC (43.9%), were detected in E. faecium isolates. All the E. faecium isolates were phenotypically resistant to ≥3 antimicrobial categories and ≥3 antibiotics, including WHO-classified reserve antibiotics linezolid (70.7%) and fosfomycin (19.5%). Moreover, the multiple antibiotic resistance index ranged up to 0.8, showing resistance to ten antibiotics and eight antibiotic classes. In this study, the prevalence of virulence genes and antibiotic resistance was significantly greater (p < 0.05) in strong biofilm-forming E. faecium strains as compared to strains with intermediate and non-biofilm-forming abilities. As far as we know, this study, for the first time in Bangladesh, determined antibiotic resistance and detected virulence genes in biofilm-forming E. faecium isolated from seafood samples. The data from this study could play a significant role in evaluating potential health hazards linked to the ingestion of uncooked or minimally processed seafood.

Antimicrobial Resistance Profiles, Virulence Determinants, and Biofilm Formation in Enterococci Isolated from Rhesus Macaques (Macaca mulatta): A Potential Threat for Wildlife in Bangladesh?

Enterococci are commensal bacteria that inhabit the digestive tracts of animals and humans. The transmission of antibiotic-resistant genes through human-animal contact poses a potential public health risk worldwide, as zoonoses from wildlife reservoirs can occur on every continent. The purpose of this study was to detect Enterococcus spp. in rhesus macaques (Macaca mulatta) and to investigate their resistance patterns, virulence profiles, and biofilm-forming ability. Conventional screening of rectal swabs (n = 67) from macaques was followed by polymerase chain reaction (PCR). The biofilm-forming enterococci were determined using the Congo red agar plate assay. Using the disk diffusion test (DDT), antibiogram profiles were determined, followed by resistance and virulence genes identification by PCR. PCR for bacterial species confirmation revealed that 65.7% (44/67) and 22.4% (15/67) of the samples tested positive for E. faecalis and E. faecium, respectively. All the isolated enterococci were biofilm formers. In the DDT, enterococcal isolates exhibited high to moderate resistance to penicillin, rifampin, ampicillin, erythromycin, vancomycin, and linezolid. In the PCR assays, the resistance gene bla_TEM was detected in 61.4% (27/44) of E. faecalis and 60% (9/15) of E. faecium isolates. Interestingly, 88.63 % (39/44) of E. faecalis and 100% (15/15) of E. faecium isolates were phenotypically multidrug-resistant. Virulence genes (agg, fsrA, fsrB, fsrC, gelE, sprE, pil, and ace) were more frequent in E. faecalis compared to E. faecium; however, isolates of both Enterococcus spp. were found negative for the cyl gene. As far as we know, the present study has detected, for the first time in Bangladesh, the presence of virulence genes in MDR biofilm-forming enterococci isolated from rhesus macaques. The findings of this study suggest employing epidemiological surveillance along with the one-health approach to monitor these pathogens in wild animals in Bangladesh, which will aid in preventing their potential transmission to humans.