Related Experiment Video

Updated: Sep 23, 2026

Amikacin Protection Assay for Quantification and Visualization of Escherichia coli Cell Invasion
09:22

Amikacin Protection Assay for Quantification and Visualization of Escherichia coli Cell Invasion

Published on: July 3, 2026

Combination effects of cephalexin and gentamicin on Edwardsiella tarda and Streptococcus iniae

Jong-Hwan Lim1, Youn-Hwan Hwang, Byung-Kwon Park

  • 1Division of Veterinary Pharmacology and Toxicology, Chungnam National University, 220 Gung-dong, Yuseong-Gu, Daejeon, South Korea.

International Journal of Antimicrobial Agents
|July 5, 2003
PubMed

Insights

This study found that combining cephalexin and gentamicin showed additive or synergistic effects against Edwardsiella tarda and Streptococcus iniae. The combination did not show antagonistic activity, suggesting potential therapeutic benefits.

Area of Science:

  • Veterinary Microbiology
  • Antimicrobial Resistance
  • Aquatic Animal Health

Background:

  • Edwardsiella tarda and Streptococcus iniae are significant pathogens in aquaculture and food fish.
  • Antibiotic resistance necessitates the evaluation of combination therapies.
  • Cephalexin and gentamicin are commonly used antimicrobials.

Purpose of the Study:

  • To evaluate the in vitro synergistic, additive, or antagonistic effects of cephalexin-gentamicin combination therapy.
  • To determine the antimicrobial activity against clinical isolates of E. tarda and S. iniae.
  • To assess the Fractional Inhibitory Concentration (FIC) index for the combination.

Main Methods:

  • Microbroth dilution checkerboard technique was employed.
  • Testing was performed against clinical isolates of Edwardsiella tarda and Streptococcus iniae.
  • Fractional Inhibitory Concentration (FIC) index was calculated to determine interaction type.

Main Results:

  • Gentamicin demonstrated greater susceptibility than cephalexin against both bacterial species.
  • The cephalexin-gentamicin combination exhibited additive interactions against both E. tarda and S. iniae.
  • Synergistic interaction was observed in 22% of E. tarda isolates, with a borderline FIC index <0.5.
  • No antagonistic effects were detected for the combination against any tested strain.

Conclusions:

  • The cephalexin-gentamicin combination shows potential as an effective treatment strategy against E. tarda and S. iniae.
  • Additive and synergistic interactions suggest improved efficacy compared to monotherapy.
  • Further in vivo studies are warranted to confirm therapeutic efficacy and safety.

More Related Videos

Antimicrobial Synergy Testing by the Inkjet Printer-assisted Automated Checkerboard Array and the Manual Time-kill Method12:03

Antimicrobial Synergy Testing by the Inkjet Printer-assisted Automated Checkerboard Array and the Manual Time-kill Method

Published on: April 18, 2019

Related Concept Videos

Determination of Multiple Dosing Parameters: Steady-State, Minimum and Maximum Concentrations01:15

Determination of Multiple Dosing Parameters: Steady-State, Minimum and Maximum Concentrations

Gentamicin, an aminoglycoside antibiotic, is commonly administered via intermittent intravenous infusion to treat severe infections. An intermittent one-hour infusion of gentamicin, administered at eight-hour intervals, allows for precise control of plasma drug concentrations, minimizing toxicity while ensuring therapeutic efficacy. Pharmacokinetic principles govern the dynamics of plasma concentrations and can be mathematically described using specific equations.The plasma drug concentration...
Inhibitors of Bacterial Protein Synthesis01:25

Inhibitors of Bacterial Protein Synthesis

Aminoglycosides constitute a highly potent class of bactericidal antibiotics that exert their antimicrobial effects by targeting the bacterial ribosome, specifically disrupting protein synthesis. These polycationic molecules consist of amino-modified sugars linked via glycosidic bonds to an aminocyclitol core such as 2-deoxystreptamine or streptamine. Their strong positive charges facilitate tight binding to the negatively charged phosphate backbone of ribosomal RNA (rRNA), primarily at the 16S...
Mechanism of Antibiotic Resistance in MRSA01:25

Mechanism of Antibiotic Resistance in MRSA

Antibiotic resistance in bacteria arises when microorganisms evolve the ability to withstand drugs designed to kill them or inhibit their growth, rendering once-effective treatments useless. This phenomenon, driven by genetic change and selection under antibiotic exposure, poses a profound threat to modern medicine. Mechanisms include drug-inactivating enzymes (e.g., β-lactamases), efflux pumps that eject antibiotics, mutations altering antibiotic targets, decreased drug uptake, and acquisition...
Pharmaceutical Alternatives: Stability-Related Therapeutic Nonequivalence01:22

Pharmaceutical Alternatives: Stability-Related Therapeutic Nonequivalence

Generic intravenous (IV) drugs are considered bioequivalent to their branded counterparts due to their 100% bioavailability upon administration. However, variations in stability among different drug products can significantly influence their therapeutic performance, even if they are pharmaceutically equivalent.Cefuroxime, a prophylactic antimicrobial, is often used as a single-dose IV injection for patients undergoing coronary artery bypass grafting surgery. A 3 g dose typically provides...
Effects of EDTA on End-Point Detection Methods01:18

Effects of EDTA on End-Point Detection Methods

Different methods, such as visual observance of metal-ion indicators, spectroscopic techniques, and potentiometric methods, can determine the endpoint of an EDTA titration.
In the visual method, metal-ion indicators (metallochromic dyes), which have distinct colors in their free and complex forms, are added to the mixture to signal the titration's end point. They form stable complexes with metal ions, but these complexes are weaker than the corresponding metal–EDTA complexes. As a result, EDTA...
Clinical Significance of Antibiotic Resistance01:25

Clinical Significance of Antibiotic Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist β-lactam antibiotics due to acquisition of the mecA gene within the staphylococcal cassette chromosome mec (SCCmec). This gene encodes penicillin-binding protein 2a (PBP2a), which impairs binding efficacy of methicillin and other β-lactams. MRSA has evolved into distinct clonal lineages impacting humans and animals alike, reinforcing its significance within the One...