Antimicrobial peptides in combination with citronellal efficiently kills multidrug resistance bacteria

BACKGROUND

Antimicrobial peptides (AMPs) are considered as the most potential alternatives to antibiotics, but they have several drawbacks, including high cost, medium antimicrobial efficacy, poor cell selectivity, which limit clinical application. To overcome the above problems, combination therapy of AMPs with adjuvants might maximize the effectiveness of AMPs. We found that citronellal can substantially potentiate the ZY4R peptide efficacy against Escherichia coli ATCC25922. However, it is unclear whether ZY4R/citronellal combination poses synergistic antimicrobial effects against most bacteria, and their synergy mechanism has not been elucidated.

PURPOSE

To investigate synergistic antimicrobial efficacies, biosafety, and synergy mechanism of ZY4R/citronellal combination.

METHOD

Checkerboard, time-kill curves, cytotoxicity assays, and in vivo animal models were conducted to assess synergistic antimicrobial effects and biosafety of the ZY4R/citronellal combination. To evaluate their synergy mechanism, a series of cell-based assays and transcriptome analysis were performed.

RESULTS

ZY4R/citronellal combination exhibited synergistic antimicrobial effects against 20 clinically significant pathogens, with the fractional inhibitory concentration index (FICI) ranging from 0.313 to 0.047. Meanwhile, ZY4R/citronellal combination enhanced antimicrobial efficacies without compromising cell selectivity, contributing to decreasing drug dosage and improving biosafety. Compared with ZY4R (4 mg/kg) and citronellal (25 mg/kg) alone, ZY4R (4 mg/kg)/citronellal (25 mg/kg) combination significantly decreased the bacterial load in peritoneal fluid, liver, and kidney (P < 0.05) and alleviated pathological damage of the organs of mice. Mechanistic studies showed that ZY4R allowed citronellal to pass through the outer membrane rapidly and acted on the inner membrane together with citronellal, causing more potent membrane damage. The membrane damage prompted the continuous accumulation of citronellal in cells, and citronellal further induced energy breakdown and inhibited exopolysaccharide (EPS) production, which aggravated ZY4R-induced outer membrane damage, thereby resulting in bacterial death.

CONCLUSIONS

ZY4R/citronellal combination exhibited broad-spectrum synergy with a low resistance development and high biosafety. Their synergy mechanism acted on two important cellular targets (energy metabolism and membrane integrity). Combination therapy of ZY4R with citronellal may be a promising mixture to combat bacterial infections facing an antibiotic-resistance crisis.

Enterobacter Cloacae keratitis after corneal cross-linking for keratoconus: A case report

PURPOSE

To report a case of Enterobacter cloacae (E. cloacae) keratitis in a patient who underwent corneal crosslinking (CXL) for progressive keratoconus.

OBSERVATIONS

A 19-year-old female underwent CXL for keratoconus in her left eye. The patient neglected her post-procedure medications and missed the follow-up visit. Subsequently, she presented on day-10 post CXL with redness and pain in the treated eye. Clinical examination revealed a ring-shape infiltrate measuring 7.8 mm in diameter. Culture indicated the presence of E. cloacae. Treatment with gentamicin failed after the emergence of resistance. The patient was successfully treated with amikacin and moxifloxacin over several weeks.

CONCLUSIONS

Judicious antibiotic selection is crucial to limit the emergence of resistance in multidrug-resistant (MDR) pathogens. All patients need to be educated about their role in the management plan.

Biocidal and biocompatible hybrid nanomaterials from biomolecule chitosan, alginate and ZnO

Biocidal activity and biocompatibility of nanomaterials (NMs) are crucial for healthcare applications. This study aims to develop biocidal hybrid NMs with high inhibition rates to control multidrug-resistant bacterial infection compared to conventional antibiotics. Herein, ZnO, chitosan-ZnO (CZnO) and alginate-ZnO (AZnO) NMs were synthesized via a simple one-pot technique. The one-pot process facilitates the efficiency of a chemical reaction whereby a reactant is subjected to successive chemical reactions in just one step. The resulted NMs bio-physicochemical features were analyzed using various analytical methods. The bactericidal and bacteriostatic mechanism of NMs strongly depends on the production of reactive oxygen species in NMs, due to their size, large surface areas, oxygen vacancies, ion release, and diffusion ability. The antibacterial potential of the NMs was tested against methicillin-resistant Staphylococcus aureus. The inhibition zone disclosed that the AZnO possessed an excellent antibacterial activity compared to ZnO and CZnO. Furthermore, toxicity studies revealed that the AZnO demonstrated low toxicity to the HepG2 cell lines. These results confirmed that the AZnO hybrid nanomaterials are promising futuristic biocidal agents suitable for the clinical and healthcare industries.

Evaluation of carcinogenic activities and sperm abnormalities of Gram-negative bacterial metabolites isolated from cancer patients after subcutaneous injection in albino rats

Microbial pathogens drive tumorigenesis in 20% of cancer cases, so the present study is aimed to evaluate the carcinogenic activities, sperm abnormalities and other dangerous effects of the subcutaneous injection of extracts obtained from various clinical Gram-negative bacteria derived from cancer patients using albino rats. We isolated, identified and extracted of their secondary metabolites of carbapenem resistant Gram-negative bacteria derived from cancer patients. Various methods have been used to determine hepatotoxicity, nephrotoxicity, tumorigenesis, inflammatory and sperm abnormalities in the albino rats injected with extracts. In comparison with the normal animals group, all extracts induced hepatotoxicity which was evidenced by the significant elevation in the activity of the serum alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltransferase and alkaline phosphatase; also, nephrotoxicity that was indicated through the marked increase in the serum urea and creatinine levels; tumorigenesis was achieved from the sharp elevation in serum levels of alpha fetoprotein, carcinoembryonic antigen and lactate dehydrogenase values as tumor markers; as well as severe inflammatory characteristics were monitored from the marked raise of tumor necrosis factor alpha and interleukin-1beta. Furthermore, the proportion of micronuclei in polychromatic erythrocytes and sperm abnormalities were statistically significant in all groups compared to control group. Various kinds of head abnormalities and coiled tail were noted. Histopathological examination of hepatic tissue came in line with the biochemical and cytological findings. It could conclude that the extracts of Serratia sp. Esraa 1, Stenotrophomonas sp. Esraa 2, Acinetobacter sp. Esraa 3, Escherichia sp. Esraa 4 and Pseudomonas sp. Esraa 5 were able to initiate cytotoxicity and tumorigenesis in rats.

Ventilator-associated pneumonia in patients with cancer: Impact of multidrug resistant bacteria

BACKGROUND

Patients with cancer have several risk factors for developing respiratory failure requiring mechanical ventilation (MV). The emergence of multidrug resistant bacteria (MDRB) has become a public health problem, creating a new burden on medical care in hospitals, particularly for patients admitted to the intensive care unit (ICU).

AIM

To describe risk factors for ventilator-acquired pneumonia (VAP) in patients with cancer and to evaluate the impact of MDRB.

METHODS

A retrospective study was performed from January 2016 to December 2018 at a cancer referral center in Mexico City, which included all patients who were admitted to the ICU and required MV ≥ 48 h. They were classified as those who developed VAP versus those who did not; pathogens isolated, including MDRB. Clinical evolution at 60-d was assessed. Descriptive analysis was carried out; comparison was performed between VAP vs non-VAP and MDRB vs non-MDRB.

RESULTS

Two hundred sixty-three patients were included in the study; mean age was 51.9 years; 52.1% were male; 68.4% had solid tumors. There were 32 episodes of VAP with a rate of 12.2%; 11.5 episodes/1000 ventilation-days. The most frequent bacteria isolated were the following: Klebsiella spp. [n = 9, four were Extended-Spectrum Beta-Lactamase (ESBL) producers, one was Carbapenem-resistant (CR)]; Escherichia coli (n = 5, one was ESBL), and Pseudomonas aeruginosa (n = 8, two were CR). One Methicillin-susceptible Staphylococcus aureus was identified. In multivariate analysis, the sole risk factor associated for VAP was length of ICU stay (OR = 1.1; 95%CI: 1.03-1.17; P = 0.003). Sixty-day mortality was 53% in VAP and 43% without VAP (P = 0.342). There was not higher mortality in those patients with MDRB.

CONCLUSION

This study highlights the high percentage of Gram-negative bacteria, which allows the initiation of empiric antibiotic coverage for these pathogens. In this retrospective, single center, observational study, MDRB VAP was not directly linked to increased mortality at 60 days.

Antibacterial and photocatalytic activities of 5-nitroindole capped bimetal nanoparticles against multidrug resistant bacteria

The emergence of antibiotic resistance to commercially- available antibiotics is becoming a major health crisis worldwide. Non-antibiotic strategies are needed to combat biofilm-associated infectious diseases caused by multidrug resistant (MDR) bacterial pathogens. In this study, MBR1 was isolated from a membrane bioreactor used in wastewater treatment plants, and the resistance profile was explored. 5-Nitroindole (5 N)-capped CuO/ZnO bimetal nanoparticles (5 NNP) were synthesized using a one pot method to improve the antibacterial and antibiofilm activities of 5 N against Gram-negative (Escherichia coli ATCC700376 and Pseudomonas aeruginosa PA01) and positive (Staphylococcus aureus ATCC6538) human pathogens. 5 NNP containing 1 mM of 5 N exhibited strong antibacterial and antibiofilm properties to most MDR bacteria. In addition, the photocatalytic activity of CuO/ZnO reduced bacterial cell growth by 1.8 log CFU/mL maximum when exposed to visible light. Scanning electron microscopy showed that 5 NNP reduced the cell density and biofilm attachment of MBR1 by >90% under static conditions. In addition to the antimicrobial and antibiofilm activities, 5 NNP inhibited the persister cell formation of MDR bacterial strains P. aeruginosa, MBR1, E. coli and S. aureus. Therefore, it is speculated that 5 NNP potentially inhibits biofilm and persister cells; hence, 5 NNP could be an alternative agent to combat MDR infectious diseases using a non-antibiotic therapeutic approach.

Characterization and in vitro evaluation of new bacteriophages for the biocontrol of Escherichia coli

In the present study two new phages (phT4A and ECA2) were characterized and their efficacy was evaluated separately and in cocktail (phT4A/ECA2) to control Escherichia coli. The isolated phages, phT4A and ECA2, belonged to the Myoviridae and Podoviridae family, respectively and both are safe (no integrase and toxin codifying genes) to be used in bacterial control. In general, the increase of multiplicity of infection (MOI) from 1 to 100 promoted a significant increase in the efficiency of phage phT4A and phage cocktail phT4A/ECA2. Both phages were effective against E. coli, but phage phT4A (reduction of 5.8 log CFU/mL after 8h treatment) was more effective than phage ECA2 phage (reduction of 4.7 log CFU/mL after 8h treatment). The use of a cocktail phT4A/ECA2 was significantly more effective (reductions of 6.2 log CFU/mL after 6h treatment) than the use single phage suspensions of phT4A and ECA2 (reductions 5.3 log CFU/mL and 4.9 log CFU/mL, respectively, after 6h treatment). The rate of emergence of phage-resistant mutants was lower for phage phT4A when compared with phage ECA2 and phage cocktail phT4A/ECA2.The results indicate that in addition to the efficacy, the potential development of phage-resistant mutants must also be considered in the design of phage cocktails.

Hospital-acquired infections at an oncological intensive care cancer unit: differences between solid and hematological cancer patients

Background

Cancer patients have a higher risk of severe sepsis in comparison with non-cancer patients, with an increased risk for hospital-acquired infections (HAI), particularly with multidrug resistant bacteria (MDRB). The aim of the study is to describe the frequency and characteristics of HAI and MDRB in critically ill cancer patients.

Methods

We conducted an 18-month prospective study in patients admitted ≥48 h to an ICU at a cancer referral center in Mexico. Patients with hematological malignancies (HM) were compared with solid tumors. Demographic and clinical data were recorded. Mortality was evaluated at 30-days.

Results

There were 351 admissions during the study period, among whom 157 (66 %) met the inclusion criteria of the study as follows: 104 patients with solid tumors and 53 with HM. Sixty-four patients (40.7 %) developed 95 episodes of HAI. HAI rate was 4.6/100 patients-days. MDRB were isolated in 38 patients (24 %), with no differences between both groups. Escherichia coli was the main bacteria isolated (n = 24), 78 % were extended spectrum beta-lactamases producers. The only risk factor associated with HAI was the presence of mechanical ventilation for more than 5 days (OR 3.12, 95 % CI 1.6 – 6.2, p = 0.001). At 30-day follow-up, 61 patients (39 %) have died (38 % with solid tumors and 60 % with HM, p < 0.001). No differences were found in mortality at 30-day between patients with HAI (n = 25, 39 %) vs. non-HAI (n = 36, 38.7 %, p = 0.964); neither in those who developed a HAI with MDRB (n = 12, 35.3 %) vs. HAI with non-MDRB (n = 13, 43.3 %, p = 0.51).

Conclusions

Patients with cancer who are admitted to an ICU, have a high risk of HAI, but there were no differences patients with solid or hematologic malignancies.