Punicalagin, a pomegranate polyphenol sensitizes the activity of antibiotics against three MDR pathogens of the Enterobacteriaceae

BACKGROUND

Multidrug resistance (MDR) in the family Enterobacteriaceae is a perniciously increasing threat to global health security. The discovery of new antimicrobials having the reversing drug resistance potential may contribute to augment and revive the antibiotic arsenal in hand. This study aimed to explore the anti-Enterobacteriaceae capability of bioactive polyphenols from Punica granatum (P. granatum) and their co-action with antibiotics against clinical isolates of Enterobacteriaceae predominantly prevalent in South Asian countries.

METHODS

The Kandhari P. granatum (Pakistani origin) extracts were tested for anti-Enterobacteriaceae activity by agar well diffusion assay against MDR Salmonella enterica serovar Typhi, serovar Typhimurium and Escherichia coli. Predominant compounds of active extract were determined by mass spectrometry and screened for bioactivity by agar well diffusion and minimum inhibitory concentration (MIC) assay. The active punicalagin was further evaluated at sub-inhibitory concentrations (SICs) for coactivity with nine conventional antimicrobials using a disc diffusion assay followed by time-kill experiments that proceeded with SICs of punicalagin and antimicrobials.

RESULTS

Among all P. granatum crude extracts, pomegranate peel methanol extract showed the largest inhibition zones of 25, 22 and 19 mm, and the MICs as 3.9, 7.8 and 7.8 mg/mL for S. typhi, S. typhimurium and E. coli, respectively. Punicalagin and ellagic acid were determined as predominant compounds by mass spectrometry. In plate assay, punicalagin (10 mg/mL) was active with hazy inhibition zones of 17, 14, and 13 mm against S. typhi, S. typhimurium and E. coli, respectively. However, in broth dilution assay punicalagin showed no MIC up to 10 mg/mL. The SICs 30 μg, 100 μg, and 500 μg of punicalagin combined with antimicrobials i.e., aminoglycoside, β-lactam, and fluoroquinolone act in synergy against MDR strains with % increase in inhibition zone values varying from 3.4 ± 2.7% to 73.8 ± 8.4%. In time-kill curves, a significant decrease in cell density was observed with the SICs of antimicrobials/punicalagin (0.03-60 μg/mL/30, 100, 500 μg/mL of punicalagin) combinations.

CONCLUSIONS

The P. granatum peel methanol extract exhibited antimicrobial activity against MDR Enterobacteriaceae pathogens. Punicalagin, the bacteriostatic flavonoid act as a concentration-dependent sensitizing agent for antimicrobials against Enterobacteriaceae. Our findings for the therapeutic punicalagin-antimicrobial combination prompt further evaluation of punicalagin as a potent activator for drugs, which otherwise remain less or inactive against MDR strains.

Inflammatory markers as prognosticators of cardiovascular dysfunction in hypothyroid patients

Hypothyroidism is a condition characterized by reduced circulating levels of thyroid hormones, T3 (tri-iodothyronine) and T4 (tetra-iodothyronine) which are produced by the thyroid gland, and increased levels of Thyroid Stimulating Hormone (TSH) from the anterior pituitary (1). The cardiovascular system is among the main targets of thyroid hormones (2), therefore, most descriptive signs and symptoms of thyroid disorders are due to their effects on the cardiovascular system (3). Direct actions of altered thyroid hormones on heart and indirect impacts through inflammatory markers, such as C-reactive protein (CRP), Interleukin-6 (IL-6) and Homocysteine (Hcy), are of great health concern. Particularly, CRP is a renowned biomarker to measure cardiovascular risks in both healthy as well as diseased subjects (4). Moreover, IL-6 is a chief mediator of tissue injury and infection, perpetuating lymphocyte infiltration in thyroid, manifesting its inflammation (5). Additionally, Hcy, having an atherogenic nature, stimulates inflammatory chemokine production and induces oxidative stress by lowering serum anti-oxidants (6). Hence, inflammatory markers may reveal the mechanism of disease progression, and can be used as a possible tool for predicting atherosclerosis and cardiovascular events (7). The aim of the present study was to assess the risk of cardiovascular dysfunctions in hypothyroid patients through predictive inflammatory markers.