Tetracycline and oxytetracycline resistance determinants detected in Bacillus cereus strains isolated from honey samples / Detección de determinantes de resistencia a tetraciclina y oxitetraciclina en cepas de Bacillus cereus aisladas de muestras de miel

The aim of this study was to investigate the presence of tetracycline and oxytetracycline resistance determinants in Bacillus cereus strains isolated from honey samples. Of a total of 77 isolates analyzed, 30 (39%) exhibited resistance to tetracyclines according to the results of a disk diffusion method. Resistant strains (n=30) were screened by PCR for the presence of the resistant determinants tetK, tetL, tetM, tetO, tetW, otrA and otrB and their MIC values for tetracycline, oxytetracycline and minocycline were assessed. According to the PCR results, 23 isolates (77%) presented at least one tetracycline or oxytetracycline resistance determinant. The tetK genotype was present in 10 isolates while the tetL, tetM, and otrA genotypes were present in 3, 2, and 5 isolates, respectively. In addition, 2 isolates of the tetK plus tetM genotype, 1 of the tetK plus tetL genotype, and 1 of the tetK plus otrA genotype were found. All isolates were tetW, tetO and otrB negatives. On the other hand, 7 isolates (23%) showed a tetracycline-resistant and/or minocyclineresistant phenotype (MIC) but did not carry any of the tet or otr determinants investigated in this study. This research has shown that B. cereus isolates from honey samples contain a variety of tetracycline and oxytetracycline resistance genes, including the tetK and tetL determinants which encode for efflux proteins, and tetM and otrA, which encode for ribosomal protection proteins. These findings indicate that strains isolated from honeys could represent a reservoir for tetracycline resistance genes. To our knowledge, this is the first report of tetracycline-resistant and oxytetracyclineresistant B. cereus strains carrying the tetK determinant, and also the first report of oxytetracycline-resistant and tetracycline- resistant Bacillus species carrying the otrA determinant.

El objetivo del presente estudio ha sido investigar la presencia de diversos determinantes de resistencia a tetraciclina y oxitetraciclina en las poblaciones de Bacillus cereus presentes en la miel. De un total de 77 aislamientos evaluados, 30 (39%) resultaron resistentes a tetraciclina y/o minociclina de acuerdo con los resultados de las pruebas de difusión en disco. Dentro del grupo que presentó un fenotipo resistente, se investigó la presencia de los determinantes tetK, tetL, tetM, tetO, tetW, otrA y otrB por PCR y se determinaron los valores de CIM para tetraciclina, oxitetraciclina y minociclina. De acuerdo con los resultados obtenidos por PCR, 23 aislamientos (77%) presentaron al menos un determinante de resistencia a tetraciclina o a oxitetraciclina; el genotipo tetK se encontró en 10 de esos aislamientos, mientras que los genotipos tetL, tetM y otrA se hallaron en 3, 2 y 5 aislamientos, respectivamente. Ningún aislamiento presentó los genotipos tetW, tetO ni otrB. Adicionalmente, se encontraron los genotipos tetK plus tetM (2 aislamientos); tetK plus tetL (1 aislamiento) y tetK plus otrA (1 aislamiento). Por otra parte, 7 cepas (23%) resultaron resistentes a tetraciclina, oxitetraciclina y/o minociclina por CIM, pero no presentaban ninguno de los determinantes tet u otr estudiados. Estos resultados indican la existencia de un alto porcentaje de cepas de B. cereus aisladas de miel con genes de resistencia a tetraciclina y oxitetraciclina, incluyendo los determinantes tetK, tetL, tetM y otrA. Este estudio constituye el primer registro de la presencia del determinante tetK de resistencia a tetraciclina en B. cereus, como así también la presencia del determinante otrA dentro del género Bacillus.

Studies on enteric red mouth disease [ERM] among freshwater fish

Six isolates of Yersinia ruckeri [Y. ruckeri], the aetiological agent of Enteric Red Mouth [ERM] disease were recovered from healthy and septicaemic Oreochromis niloticus [O.niloticus] fish collected from River Nile at Giza Governorate. The isolate No. 2 was the most pathogenic strain of the six isolates, causing high mortality percent among the experimentally infected fish under different stress conditions, namely overcrowdness, external parasitism and transportation with mortality rates of 83%, 70% and 60% in O. niloticus respectively. The mortality rate was 100% in intraperitoneally inoculated O. niloticus and Clarias lazera [C. lazera], while it was 40% in subcutaneously inoculated C. lazera. The main recorded clinical signs in experimentally infected fishes were general septicemia and redness of the eyes. The in-vitro antibiotic sensitivity test for Y. ruckeri isolates revealed their high sensitivity to oxytetracycline

Antibiotics and garlic clove extract--inhibitory agents of cell wall degrading enzymes.

Four antibiotics were tested against Erwinia causing soft rot of onion (Allium cepa var. aggregatum) of which streptomycin sulphate 90% and tetracycline hydrochloride 10% (streptocycline) recorded the maximum inhibition zone of 27.66 mm. In the enzyme studies the maximum inhibition of pectinlyase (PL), polygalacturonase (PG) and protopectinase production was recorded by the same antibiotic. The antibiotics have a significant influence on the production and activity of cell wall degrading enzymes produced by the plant pathogenic microorganisms. Garlic clove extract was equally effective in inhibiting the growth and enzyme production.

Effect of some antibiotics on Macrophomina phaseolina, a charcoal rot fungus of soybean.

Effect of agrimycin-100, ampicillin, griseofulvin and tetracycline on colony growth of Macrophomina phaseolina, incitant of charcoal rot of soybean has been studied in vitro. Amongst them tetracycline posed most effective inhibiting the growth by 73.9% at 1000 micrograms/ml concentration. On the basis of effectiveness antibiotics have been listed as tetracycline greater than ampicillin greater than griseofulvin greater than agrimycin-100.

Estudo dos efeitos do fenobarbital, clordano e oxitetraciclina sobre a eliminaçäo do DDT pela via biliar em ratos

Foram realizados estudos sobre efeitos do fenobarbital, clordano e oxitetraciclina sobre a eliminaçäo de DDT através da bile em ratos. Procurou-se também evidenciar a relaçäo entre um possível aumento do fluxo biliar induzido por aqueles compostos e a eliminaçäo de DDT. O fenobarbital (2,5 mg ml-1) foi colocado na água de beber e o clordano (200 mg kg-1) na raçäo, por um período de três dias consecutivos; a oxitetraciclina (200 mg kg-1/dia) foi administrada por via oral por um período de oito dias consecutivos. Após estes tratamentos, foi feita a administraçäo de 14C-DDT por via digestiva, em animais anestesiados e a seguir a bile foi coletada por canulaçäo do canal colédoco. Os resultados obtidos mostram que: -O fenobarbital e o clordano provocam uma diminuiçäo significativa no tempo de paralisis induzida pela zoxazolamina e determinam um aumento de peso do fígado, do fluxo biliar, da eliminaçäo do 14C-DDT pela bile e simultaneamente uma diminuiçäo da 14C-DDT no plasma; -A oxitetraciclina aumenta significativamente o tempo de paralisia induzido pela zoxazomina, efeito contrário ao do fenobarbital e do clordano; por outro lado, este composto näo altera o peso do fígado, o fluxo biliar, nem a eliminaçäo do 14C-DDT, mas determina uma menor concentraçäo do inseticida no sangue; -A análise dos dados das concentraçöes de 14C-DDT por ml de bile nos períodos de 2, 4, 6 e 7 horas mostrou que os mesmos näo säo significantes para o fenobarbital, clordano e oxitetraciclina, o que permite concluir que a quantidade de 14C-DDT eliminada através do canal colédoco depende da velocidade de eliminaçäo da bile