Growth hormones/breast cancer and antibiotics/E. coli

[Kathy]

Here are a couple of newer studies out there which do not look favorably upon the use of growth promoters/ and or antibiotics by the cattle industry.

Growth hormones and breast cancer

Breast J. 2004 Nov-Dec;10 (6):514-521.

Transformation of MCF-10A human breast epithelial cells by zeranol and estradiol-17beta.

Liu S, Lin YC.

Laboratory of Reproductive and Molecular Endocrinology, College of Veterinary Medicine, Ohio State University, 1900 Coffey Rd., Columbus, Ohio 43210-1092, USA.

Among the endocrine factors associated with breast cancer, estrogens are considered to play a central role in human breast carcinogenesis. Breast cancer risks are increased by long-term exposure to estrogens. Zeranol (Ralgro) is a nonsteroidal agent with estrogenic activity that is used as a growth promoter in the U.S. beef and veal industry. To determine whether zeranol and estradiol-17beta play a role in the neoplastic transformation of human breast and to compare the estrogenic potency of zeranol to that of estradiol-17beta in human breast, we treated human breast epithelial cell MCF-10A with different doses of zeranol or estradiol-17beta for 10 repeated treatment cycles. By utilizing the doubling time assay, soft agar assay, and reverse transcriptase polymerase chain reaction (RT-PCR) assay, we showed that 10 repeated estradiol-17beta or zeranol treatment cycles to MCF-10A cells decrease the doubling time of the cells by 30 to 40% and stimulate colony formation in soft agar and induce estrogen receptor beta (ER-beta) mRNA expression, all of which are not dose related in our tested dose range. Furthermore, we show that zeranol and estradiol-17beta have a similar potency in the stimulation and inhibition of gene expressions in human breast cancer cell line MCF-7 by RT-PCR. These results indicate that both zeranol and estradiol-17beta can induce human breast epithelial cell neoplastic transformation with similar potency in the long-term exposure through the oxidation-reduction (redox) pathway and/or ER-beta-mediated pathway.

PMID: 15569208 [PubMed - indexed for MEDLINE]

(What this study is saying, is that at levels even lower than those approved by the FDA (USA), for growth hormones in meat, they are capable of causing tumor growth (neoplastic transformation) in breast cells. Some will be malignant and some may be benign. Also, the hormones caused an increase of 30 to 40%, in the time it takes for these cells to double, ie: 10 to 20, 20 then to 40, and so on. This report was supposedly funded by the Pentagon.)



Antibiotics and E. Coli:

J. Food Prot. 2005 Nov; 68(11):2411-9.


Antibiotic resistance and hypermutability of Escherichia coli O157 from feedlot cattle treated with growth-promoting agents.

Lefebvre B, Diarra MS, Giguere K, Roy G, Michaud S, Malouin F.

Centre d'Etude et de Valorisation de la Diversite Microbienne, Departement de Biologie, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, Canada J1K 2R1.

In a longitudinal study (165 days), we investigated the effect of growth-promoting agents (monensin and trenbolone acetate-estradiol) and an antibiotic (oxytetracycline) on the incidence in feedlot steers of Escherichia coli O157, including antibiotic-resistant and hypermutable isolates. Eighty steers in 16 pens were treated with eight combinations of promoters, and each treatment was duplicated. Fecal samples were collected at nine different sampling times for detection of E. coli O157. Overall, 50 E. coli O157 isolates were detected in treated animals, and none were found in untreated animals. Compared with untreated controls, there was a significant association between the utilization of growth-promoting agents or antibiotics and the shedding of E. coli O157 at day 137 (P = 0.03), when a prevalence peak was observed and 50% of the isolates were detected. Multiplex PCR assays were conducted for some virulence genes. PCR results indicated that all except one isolate possessed at least the Shiga toxin gene stx2. MICs for 12 antibiotics were determined, and eight oxytetracycline-resistant E. coli O157 strains were identified. Antibiotic-resistant strains were considered a distinct subpopulation of E. coli O157 by pulsed-field gel electrophoresis typing. Seven of these antibiotic-resistant strains were isolated early in the study (on or before day 25), and among them two were also hypermutable as determined by rifampin mutation frequencies. The proportion of hypermutable strains among E. coli O157 isolates remained relatively constant throughout the study period. These results indicate that the use of growth-promoting agents and antibiotics in beef production may increase the risk of environmental contamination by E. coli O157.

(This study is saying that animals dosed with antibiotics and/ or growth hormones, shed E. coli 0157 strains of bacteria. The animals in the test study which were not treated with them, did not shed the E. coli bacteria in their feces. There are others studies similar to this. One such report, stated calves fed milk replacers with antibiotics increased the levels of E. coli 0157 shed in their feces, as well. This explains why meat processors are very concerned about manure on the cattle - tag.)