In Vitro Study of the Interaction of Gentamicin with Ceftriaxone and Azithromycin against Neisseria gonorrhoeae Using Agar Dilution Method

Novel synergistic interactions between monolaurin, a mono-acyl glycerol and β lactam antibiotics against Staphylococcus aureus: an in vitro study

BACKGROUND

A major worldwide health issue is the rising frequency of resistance of bacteria.Drug combinations are a winning strategy in fighting resistant bacteria and might help in protecting the existing drugs.Monolaurin is natural compound extracted from coconut oil and has a promising antimicrobial activity against Staphylococcus.aureus. This study aims to examine the efficacy of monolaurin both individually and in combination with β-lactam antibiotics against Staphylococcus aureus isolates.

METHODS

Agar dilution method was used for determination of minimum inhibitory concentration (MIC) of monolaurin against S.aureus isolates. Scanning electron microscope (SEM) was used to detect morphological changes in S.aureus after treatment with monolaurin. Conventional and Real-time Polymerase chain reaction (RT-PCR) were performed to detect of beta-lactamase (blaZ) gene and its expressional levels after monolaurin treatment. Combination therapy of monolaurin and antibiotics was assessed through fractional inhibitory concentration and time-kill method.

RESULTS

The antibacterial activity of monolaurin was assessed on 115 S.aureus isolates, the MIC of monolaurin were 250 to 2000 µg/ml. SEM showed cell elongation and swelling in the outer membrane of S.aureus in the prescence of 1xMIC of monolaurin. blaZ gene was found in 73.9% of S.aureus isolates. RT-PCR shows a significant decrease in of blaZ gene expression at 250 and 500 µg/ml of monolaurin. Synergistic effects were detected through FIC method and time killing curve. Combination therapy established a significant reduction on the MIC value. The collective findings from the antibiotic combinations with monolaurin indicated synergism rates ranging from 83.3% to 100%.In time-kill studies, combination of monolaurin and β-lactam antibiotics produced a synergistic effect.

CONCLUSION

This study showed that monolaurin may be a natural antibacterial agent against S. aureus, and may be an outstanding modulator of β-lactam drugs. The concurrent application of monolaurin and β-lactam antibiotics, exhibiting synergistic effects against S. aureus in vitro, holds promise as potential candidates for the development of combination therapies that target particularly, patients with bacterial infections that are nearly incurable.

Impact of Alternative Growth Supplements on Antimicrobial Susceptibility Testing of Neisseria gonorrhoeae

Purpose

The accurate detection of antibiotic susceptibility of Neisseria gonorrhoeae (N. gonorrhoeae) is of great importance for the treatment of patients with gonorrhea as well as to hinder the progress of drug resistance. To promote the application of gonococcal antibiotic susceptibility monitoring in primary hospitals and remote medical institutions, this study evaluated the effect of alternative growth supplements on the antibiotic susceptibility testing of N. gonorrhoeae isolates.

Methods

We divided the antimicrobial-containing media into three groups by adding different growth supplements (sterile defibrinated sheep blood, bovine hemoglobin, and Vitox). We tested the antimicrobial susceptibility of 80 N. gonorrhoeae isolates in different groups against eight antibiotics. Nonparametric signed-rank tests were utilized to compare the minimum inhibitory concentration (MIC) results of each group. Taking the MIC results of Vitox group as expected, the essential agreement (EA) and category agreement (CA) of the other two groups were calculated.

Results

For the group using sheep blood as growth supplements, the EA values and CA values of each antibiotic were above 90.00% and minor error rates were less than 7.00%. No very major error and major error were observed. For the group using hemoglobin as growth supplements, the EA values of the susceptibility results of zoliflodacin, penicillin, and ceftriaxone were lower than 90.00%. The overall MIC results of using hemoglobin as a growth supplement were higher than those of sheep blood and Vitox in the susceptibility testing of these three antibiotics.

Conclusion

Compared with the expected results, sheep blood may be considered for the use as an alternative material for N. gonorrhoeae antibiotics susceptibility surveillance, while hemoglobin may not be suitable for supplement to antimicrobial-containing medium.