In vitro and in vivo susceptibility of the honeybee bacterial pathogen Paenibacillus larvae subsp. larvae to the antibiotic tylosin

Abstract

The minimal inhibitory concentrations (MICs) of tylosin were determined to 67 strains of Paenibacillus larvae subsp. larvae, the causal agent of American Foulbrood (AFB) disease, from different geographical origins. MIC values obtained ranged from 0.0078 to 0.5 mg/ml. These very low values imply that no resistance to tylosin was found in any isolate of the Foulbrood pathogen.The measurement of diseased larvae with AFB-clinical symptoms in three different field studies demonstrated that tylosin treatment could be effective in vivo. No negative effects in colonies were noted at any dosage rates or forms of application. These studies demonstrate that tylosin, as tartrate, can be used to treat AFB in honeybee colonies. #

Determination of tylosins A, B, C and D in bee larvae by liquid chromatography coupled to ion trap-tandem mass spectrometry

“…Indeed, the accumulation of this antibiotic in honey has been determined in several studies [5][6][7]. However, tetracycline resistant strains have been identified in the USA, Canada and Argentina [8][9][10][11][12][13], and so other antibiotics, such as tylosin and lincomycin have also been proposed to control AFB [14][15][16][17][18][19].…”

Evaluation of kinetic behaviour of two preparations of tylosin administered in beehives for American foulbrood control

“…Accordingly, the concentrations of tylosin in the YLs indicated that although both forms of delivery -via paper pack or by dustinghad proven effective in controlling AFB in previous field trails (Hitchcock et al, 1970;Peng et al, 1996;Alippi et al, 2005;Reynaldi et al, 2010b), the more rapid elimination of tylosin applied by paper pack made this treatment the better one. The more time a microorganism spends at sub-inhibitory concentrations, the greater the chances of selection for a resistant microorganism.…”

“…Among them, tylosin appeared as an attractive alternative exhibiting both a bactericidal effect and the best in vitro inhibition of P. larvae in terms of the MIC, MBC, and MBC/MIC values (Peng et al, 1996;Alippi et al, 2005;Reynaldi et al, 2010b). Furthermore, the field efficacy of tylosin had already been demonstrated by several authors (Elzen et al, 2002;Alippi et al, 2005;Pettis & Feldlaufer, 2005). However, the consumption of tylosin was a trouble, for this reason, Peng et al (1996) recommended the use of cherry jelly as an attractant to improve the palatability of tylosin treatment.…”

“…A probability level of less than 0.05 was considered statistically significant. for the growth of Paenibacillus larvae (Alippi et al, 2005) is indicated by a horizontal line. The arrows above the curves, point the days on which tylosin doses were added to the hives.…”

“…Oxytetracycline (OTC) and tylosin are the only antibiotics approved for the control of AFB in bee hives, nonetheless the high selection pressure because of the intensive use of OTC in professional beekeeping, added to the fact that OTC having been also used against Melisococcus plutonius (Oldroy et al, 1989;Thompson et al, 2005) possibly favoured the oxytetracycline-resistant P. larvae isolates in Argentina (Alippi, 2000), Canada (Colter, 2000) and the USA (Miyagi et al, 2000). In addition, the efficacy of tylosin has already been proven through the use of different application methods (dusting or the placement in paper-packs, syrupy sugar, and patties) by different authors (Hitchcock et al, 1970;Peng et al, 1996;Alippi et al, 2005;Pettis & Feldlaufer, 2005;Reynaldi et al, 2009). This feature makes tylosin an alternative for the control of infected hives with oxytetracycline-resistant isolates.…”