In vitro susceptibility of Staphylococcus aureus strains isolated from cows with subclinical mastitis to different antimicrobial agents.

Sensitivity to commercial teat dips (nonoxinol-9 iodine complex and chlorhexidine digluconate) of 56 Staphylococcus (S.) aureus strains isolated from quarter milk samples of various German dairy herds treated with different teat dipping schemes was investigated in this study. The minimum inhibitory concentration was determined using a broth macrodilution method according to the German Veterinary Association guidelines. The main objective of the current study was to induce in vitro resistance induction of S. aureus to chemical disinfectants. Ten different strains were repeatedly passed ten times in growth media with sub-lethal concentrations of disinfectants. Nine strains showed a significant reduction in susceptibility to the nonoxinol-9 iodine complex but only one strain developed resistance to chlorhexidine digluconate. Stability of the acquired resistance was observed in all S. aureus strains adapted to the nonoxinol-9 iodine complex and chlorhexidine digluconate. In contrast, simultaneous resistance to different antibiotics was not observed in any of the ten investigated S. aureus strains. However, the isolates exhibited a high degree of resistance to penicillin G. Based on these results, resistance of S. aureus to chemical disinfectants may be more likely to develop if the chemicals are used at concentrations lower than that required for an optimal biocidal effect.

Source identification of airborne Escherichia coli of swine house surroundings using ERIC-PCR and REP-PCR.

Evidence is mounting that microorganisms originating from livestock impact the air quality of the animal houses themselves and the public in the surrounding neighborhoods. The aim of this study was to develop efficient bacterial source tracking capabilities to identify sources of Escherichia coli aerosol pollution caused by pigs. Airborne E. coli were isolated from indoor air, upwind air (10 and 50 m away) and downwind air samples (10, 50, 100, 200 and 400 m away) for five swine houses using six-stage Andersen microbial samplers and Reuter-Centrifugal samplers (RCS). E. coli strains from pig fecal samples were also collected simultaneously. The enterobacterial repetitive intergenic consensus polymerize chain reaction (ERIC-PCR) and the repetitive extragenic palindromic (REP-PCR) approaches were used to study the genetic variability and to determine the strain relationships among E. coli isolated from different sites in each swine house. Results showed that 35.1% (20/57) of the bacterial DNA fingerprints from the fecal isolates matched with the corresponding strains isolated from indoor and downwind air samples (similarity > or = 90%). E. coli strains from the indoor and downwind air samples were closely related to the E. coli strains isolated from feces, while those isolated from upwind air samples (swine house C) had low similarity (61-69%). Our results suggest that some strains isolated from downwind and indoor air originated in the swine feces. Effective hygienic measures should be taken in animal farms to prevent or minimize the downwind spread of microorganism aerosol.

Simultaneous detection of airborne aflatoxin, ochratoxin and zearalenone in a poultry house by immunoaffinity clean-up and high-performance liquid chromatography.

An AOZ method, based on high-performance liquid chromatography (HPLC), was optimized on HPLC condition such as mobile phase and wavelength to simultaneously quantify six kinds of mycotoxins [four aflatoxins (AFs), ochratoxin A (OTA) and zearalenone (ZEA)]. Conditions for immunoaffinity clean-up, HPLC and photo-derivatization were optimized in this study and successfully applied in assessment of airborne mycotoxins from a poultry house in Dalian, China. Fifty-two air samples were collected with AGI-30 air samplers using pure water as collection media. Twenty air samples (20/52, 38.46%) were positive for four toxins. Among the positive samples, airborne mycotoxin concentrations (mean+/-S.D.) for AFG(2), AFB(1), and ZEA were 0.189+/-0.024 (n=9), 0.080+/-0.003 (n=11) and 2.363+/-0.030 (n=5)ng/m(3) air, while the concentration for OTA was 8.530 (n=1)ng/m(3). No positive sample was found for either AFG(1) or AFB(2). A chicken may inhale 0.019-0.057 ng AFG(2), 0.013-0.019 ng AFB(1), 0.436-0.513 ng ZEA, and 1.706 ng OTA, respectively, in a day. A poultry worker may inhale 0.504-1.512 ng AFB(1), 0.752-2.28 ng AFG(2), 68.240 ng OTA, and 17.432-20.512 ng ZEA in a working day. This is the first report on airborne mycotoxins in poultry house. These data may have importance in animal and public health implications.

[Biodegradation of estrogens in stream water]. / Biologischer Abbau von Ostrogenen im Flusswasser.

Estrogens of human and animal origin that reach the aquatic environment may enter human or animal organism and act as endocrine disruptors.To investigate the persistency of estrogens in laboratory experiments, estrone respectively 17beta-estradiol were added to stream water sampled from river Spree in Berlin. The concentration of estrone and 17beta-estradiol was quantified using enzyme-immuno-assay. The estrone concentration decreased to less than 5 % of the starting concentration at storage temperature of 5 degrees C within 56 days and at storage temperature of 20 degrees C within 14 days. If the estrone were added to autoclaved stream water, no biodegradation was observed. Biodegradation was enhanced when activated sludge was added. Escherichia coli, Pseudomonas fluorenscens and Aeromonas hydrophila in monoculture did not degrade estrone in autoclaved stream water. The concentrations of 17beta-estradiol and estrone decreased similarly. The logistic function proved to be suitable to describe the course of time for the decrease of concentration.