Qualitative Ampule and Multitest for Beta-Lactam Residues in Fluid Milk Products: Collaborative Study

A collaborative study was performed on a rapid Bacillus stearothermophilus agar diffusion ampule method to detect low levels of penicillin G in 7 types of fluid milk products. A multitest technique for processing a large number of samples simultaneously was also studied. Slight modifications were made in the original method to establish more uniformity and to eliminate doubtful responses by specifying a confirmation procedure. Twenty samples spiked with penicillin G (0.000 to 0.008 IU/mL) and tetracycline hydrochloride were frozen and sent to 20 laboratories in the ampule test, and 16 laboratories in the multitest. Each analyst was asked to do a screening run and a confirmation run. Results were reported by color reaction and also as positive or negative for β-lactam inhibitors. The concentrations (penicillin G) where percent positive results equal 100 or not significantly less than 100 (α = 0.05) ranged from 0.005 to 0.007 IU/mi in the ampule test and from 0.004 to 0.007 IU/mL in the multitest. Both techniques have been adopted official first action.

Comparison of Microbiological Methods for Detecting Penicillin and Penicillin-Like Antibiotic Residues in Milk

Five microbiological methods for detecting residues of penicillin and penicillin-like antibiotics were compared, and the relative incidence of residues in whole milk samples was determined. Five groups of 10 lactating cows each and five commercial antibiotic products (penicillin G in oil, penicillin G in a water-dispersible oil base, cloxacillin, cephapirin and ampicillin) used for the treatment of mastitis were studied. Milk samples collected from the cows were tested for antibiotic content by the Sarcina lutea or Bacillus subtilis cylinder plate, International Dairy Federation-Association of Official Analytical Chemists (IDF-AOAC) Bacillus stearothermophilus ATCC 10149 disc plate, Delvotest-P, Antibiotic Residue Branch (ARB) B. stearothermophilus C 953 quantitative disc plate and ARB B. stearothermophilus C 953 quantitative cylinder plate methods. All samples tested by the original S. lutea or B. subtilis cylinder plate methods, with the exception of the penicillin G in oil product (Uni-Biotic), were free of antibiotic residues and showed no inhibitors beyond the labeled milk withdrawal time. The newer, more sensitive official IDF-AOAC method, Delvotest-P and both ARB B. stearothermophilus quantitative disc and cylinder plate methods detected measurable amounts of cephapirin and penicillin G in the post-treatment milk for one to three additional milkings beyond the labeled milk discard time. Cloxacillin, as determined by the ARB B. stearothermophilus cylinder plate method, was generally depleted by 48 h. The excretion rate of ampicillin product coincided with the labeled milk discard time. The level of detection of both disc plate methods and Delvotest-P for cephapirin and ampicillin was comparable. Variations in the concentration in milk and the persistence of two penicillin G products were probably due to differences in the formulation and the dosing regimen. Inhibitory substances and non-specific reactions were observed with the IDF-AOAC disc method, the Delvotest-P and both ARB B. stearothermophilus methods in some control and post-treatment milk samples. These results are consistent with reports of other investigators and suggest that the use of more sensitive procedures for monitoring antibiotic residues in milk may result, for some infusion preparations, in an increased incidence of violative residues of penicillin G and cephapirin.

Cylinder Plate Assay for Determining Bacitracin in Premix Feeds and Finished Feeds: Collaborative Study

A cylinder plate assay procedure was studied by 10 laboratories. For premix feeds, 3 samples of bacitracin methylene disalicylic acid and 3 samples of bacitracin zinc premixes covering the range of 10 to 50 g/lb were used. The repeatability standard deviation was 2.11, and the reproducibility standard deviation was 2.13. The average recovery of bacitracin was 101.5%. The method has been adopted official first action. For finished feeds, 6 samples of bacitracin methylene disalicylic acid and 6 samples of bacitracin zinc covering the range of 10 to 800 g/ton were used in the study. The procedure included a sample cleanup step using disposable reverse phase columns. This step appears to be the cause of the poor results reported by most collaborators. Continued study is needed to develop an acceptable method for finished feeds.

Turbidimetric Microbiological Determination of Oxytetracycline Hydrochloride in Finished Feeds and a Feed Premix: Collaborative Study

New automated and manual turbidimetric microbiological assay methods for oxytetracycline (OTC) in finished feeds and a feed premix were submitted to 17 collaborating laboratories for comparison with the official AOAC method. Six finished feeds of 50 and 100 g/ton levels and one premix containing 20 g OTC/lb were sent to the collaborators. Results were received from 12 laboratories. Six laboratories provided results derived from the Autoturb System and 7 laboratories performed the turbidimetric analyses manually. All 12 laboratories assayed the samples by the AOAC cylinder-plate method. Ranges of recoveries expressed as percent were 89.5–102.0, 91.2–97.0, and 91.4–96.0 for the AOAC, Autoturb turbidimetric, and manual turbidimetric methods, respectively. Average recoveries were 96.3, 93.4, and 93.6%, respectively. The mean relative standard deviation values were 5.7, 6.3, and 7.2, respectively. There was little significant difference between the turbidimetric methods and the AOAC method; however, the turbidimetric methods were faster.

Dibekacin intrarenal distribution characteristics and renal cortical elution kinetics. Comparison with gentamicin and tobramycin

Dibekacin (3',4-dideoxykanamycin B) is a new semisynthetic aminoglycoside developed in Japan and one which has found wide clinical acceptance in that country. The antibacterial activity of this compound indicates that it is relatively similar to gentamicin. Since it appears that the intrarenal distributional characteristics and renal cortical kinetics of aminoglycosides provide some predictive information concerning the clinical incidence of nephrotoxicity, we designed a series of pharmacokinetic studies in healthy mongrel dogs which would define such kinetic information for dibekacin and would contrast the results with similar studies for gentamicin and tobramycin. The renal cortical kinetics of dibekacin, as developed in these studies, show that in a canine model the behavior of dibekacin is similar to that of gentamicin and significantly different from tobramycin. Dibekacin and gentamicin show reproducibly higher renal cortical tissue concentrations than tobramycin in both the acute infusion studies and multiple dosing studies. The results suggest that dibekacin may possess the same inherent nephrotoxic potential as that of gentamicin. In order to show any difference in clinical toxicity between gentamicin and dibekacin, a very extensive randomized, double-blind, prospective clinical trial of efficacy and toxicity will be needed.

Therapeutic implications of doxycycline and cephalothin concentrations in the female genital tract

The pharmacokinetics of doxycycline and cephalothin in genital tissues and serum were evaluated in 38 patients undergoing hysterectomy. Antibiotic concentrations in the ovary, fallopian tube, myometrium, cervix, and endometrium were measured at varying intervals after antibiotic administration. Cephalothin concentrations in tissues were critically dependent on the time interval between preoperative antibiotic administration and removal of the genital tract tissues, whereas doxycycline concentrations in tissues were consistently reproducible in the time frame evaluated (1/2 to 4 1/2 hours after drug administration). Doxycycline endometrial concentrations were consistently higher than those measured elsewhere in the genital tract (P less than 0.05). These results are of importance in a reassessment of traditional approaches to antibiotic use in gynecologic surgery and in the management of pelvic inflammatory disease (PID).

Pharmacokinetic characteristics of doxycycline accumulation in normal and severely diseased kidneys

Intrarenal concentrations of doxycycline were measured in 48 normal canine kidneys during wide variations in urine pH and the systemic state of hydration of the experimental animals. The results were compared with the renal parenchymal levels achieved in 10 severely diseased human kidneys. Although the state of hydration, the urine pH, and renal disease all significantly influenced the urinary concentrations and rate of renal clearance of doxycycline, there was no detectable difference between concentrations in normal renal tissue and those in severely diseased kidneys. This result is in contradistinction of the findings for previously evaluated antibiotics. The levels of doxycycline measured in renal tissue averaged twice the concentration in serum without notable difference among levels in renal cortex, medulla, and papilla. Prospective clinical trials will be necessary for identification of any solid correlation between the remarkable characteristics of accumulation of doxycycline in diseased renal parenchymal tissue and the clinical, therapeutic importance of such an observation.

Bullet embolization to the heart. Report of a case and review of the literature on indications for removal of intracardiac foreign bodies

The hospital course of a young man with a bullet migration through the venous system to the right ventricle is reviewed. The intraoperative management of foreign bodies to the heart using x-ray image intensifier is employed.