Evolution of drug resistance and minimum inhibitory concentration to enrofloxacin in Tenacibaculum maritimum strains isolated in fish farms

Abstract

The in vitro susceptibility of 63 isolates of Tenacibaculum maritimum from four fish farms to eight chemotherapeutic agents used for the treatment of bacterial diseases in fish were assessed. The results indicated that all strains were resistant to oxolinic acid and susceptible to amoxicillin, nitrofurantoin, florfenicol, oxytetracycline and trimethoprim-sulphamethoxazole. However, some isolates presented resistance to enrofloxacin and flumequine, ranging from 10 to 30%, and from 25 to 60%, respectively, depending on the farm sampled. These data were used in an attempt to predict whether the resistance to enrofloxacin was static or evolved during the time of sampling from 2003 to 2004. A relationship between the use of enrofloxacin and levels of resistance was detected in the studied farm, increasing significantly from no resistant isolates in 2003 to 44.8% resistant strains in 2004, the year in which this drug was commonly employed. This result was accompanied by a marked decline of about 29.2% of the inhibition zone sizes for the T. maritimum strains in comparison to the initial values (average 21.5 mm). Minimum inhibitory concentration (MIC) of enrofloxacin for 100 T. maritimum strains was determined by the microdilution method. Twenty isolates were resistant to enrofloxacin (> 256 mg ml À1 ), while the remaining strains showed a bimodal distribution, which ranged from 0.5 to 32 mg ml À1 . Our interpretation of the enrofloxacin MIC data suggests that the breakpoint for T. maritimum should be 4 mg ml À1 . However, similar studies in other laboratories are necessary to validate this breakpoint value.

A review of infectious gill disease in marine salmonid fish

“…In vitro susceptibility testing of 63 isolates of T. maritimum (Avendaño‐Herrera, Núñez, Barja & Toranzo 2008) to eight different antibiotics found it to be susceptible to amoxycillin, nitrofurantoin, florfenicol, oxytetracycline and trimethoprim–sulphamethoxazole; however, it was resistant to oxolinic acid. In addition, some isolates of T. maritimum were found to be resistant to enrofloxacin and flumequine.…”

Roseobacter Group Probiotics Exhibit Differential Killing of Fish Pathogenic Tenacibaculum Species

“…T. maritimum is susceptible to multiple antibiotics (11,15,16) and their application is a possible treatment of tenacibaculosis. However, the use of antibiotics poses a series of challenges including poor efficacy when administered in situ (17), but also in terms of sustainable rearing practices.…”

A Novel Cecropin-LL37 Hybrid Peptide Protects Mice Against EHEC Infection-Mediated Changes in Gut Microbiota, Intestinal Inflammation, and Impairment of Mucosal Barrier Functions

“…Historically, the broad-spectrum antibiotic enrofloxacin (Enro) has been used to treat diseases during previous decades ( 10 – 13 ). However, antibiotic resistance has become a serious global issue and is steadily increasing worldwide in almost every species treated with antibiotics ( 15 , 16 ). Also of increasing concern, long-term antibiotic treatment can alter the microecosystem balance by causing compositional changes in the intestinal microbiota and may lead to a homeostatic imbalance by altering the expression of tight junction proteins, mucin, antimicrobial peptides, and cytokines in intestinal epithelial cells ( 17 , 18 ).…”