Pharmaceuticals in the Environment—A Human Risk?

Determination of penicillin G and its degradation products in a penicillin production wastewater treatment plant and the receiving river

Enzyme immunoassays are attaining increased usage for the direct detection of microbial antigens in body fluids. Advantages of enzyme immunoassays include a high degree of sensitivity resulting from the inherent magnification of the enzyme-substrate reaction and the use of objective end points without the need for radioactivity. Enzyme immunoassays have been developed for the reliable detection of several important microbial antigens in body fluids, including antigens of rotavirus, hepatitis B virus, and Haemophilus influenzae type b. However, standard enzyme immunoassay techniques are not sufficiently sensitive for the measurement of some antigens from other viruses, bacteria, and parasites in concentrations that commonly occur in body fluids during the course of infectious diseases. This review examines some of the limitations of currently available enzyme immunoassay technology and discusses approaches to increasing the sensitivity and specificity of enzyme immunoassay systems. Methods for improving these assay systems include the use of monoclonal antibodies, improved methods of enzyme-immunoreactant conjugation, more sensitive substrate systems, improved methods of antigen-antibody access, and the direct measurement of microbial enzymes. The use of such techniques should lead to the development of efficient enzyme immunoassay systems for the direct detection of a wide range of bacterial, viral, and parasitic infections.

Enzyme Immunoassays for the Detection of Infectious Antigens in Body Fluids: Current Limitations and Future Prospects

Synopsis: Tobramycin is a new aminoglycoside antibiotic with a broad antibacterial spectrum in vitro, and pharmacokinetic properties similar to those for gentamicin. Tobramycin is more active than gentamicin against Pseudomonas aeruginosa and active against many gentamicin resistant strains, but is not active against enterobacteriaceae resistant to gentamicin.

Tobramycin: A Review of its Antibacterial and Pharmacokinetic Properties and Therapeutic Use

Publisher Summary This chapter describes the process of microbial transformation of antibiotics into useful compounds, which is mostly concentrated upon the production of 6-aminopenicillanic acid (6-APA) by enzymatic hydrolysis of biosynthetic penicillins. The chapter describes biotransformation processes of penicillins into 6-APA that use, as a source of acylase, intact bacterial cells, fungal mycelium, fungal spores, crude cell extracts, purified enzyme preparations, stabilized enzymes, and supernatant liquid of extracellular acylase-producing microorganisms. The chapter examines methods to isolate and purify penicillin acylases and to stabilize these enzyme preparations. It reviews the physicochemical properties and the degradation reactions in relation to the structure of penicillins and describes the reaction of cysteine and related compounds with penicillins, resulting in a loss of antibacterial activity. 6-APA was originally produced by fermentation synthesized in a purely chemical way. Enzymatic transformation of biosynthetic penicillins into 6-APA is an industrial process of economic importance as the main source of 6-APA used in the preparation of semisynthetic penicillins.

Microbial Penicillin Acylases

Penicillins can be metabolized to penicilloic acids in man, the extent being dependent on the penicillin structure. In the phenoxy penicillin series, phenoxymethyl penicillin was found to be particularly unstable, but the higher homologues were more stable. In the isoxazolyl series, oxacillin was unstable, and progressive insertion of halogen in the phenyl ring increased stability. Ampicillin and amoxycillin showed some instability, ampicillin possibly being the more stable. After intramuscular administration, carbenicillin was very stable in the body, ampicillin was fairly stable, and benzyl penicillin was unstable. It is important to take into account the penicilloic acid content of urine when estimating total absorption of a penicillin. Increased stability in the body as well as slower renal clearance can lead to high concentrations in the serum. Penicilloic acids seemed to be more slowly cleared from the body than penicillins. The liver is probably the site of inactivation.

Metabolism of Penicillins to Penicilloic Acids and 6-Aminopenicillanic Acid in Man and Its Significance in Assessing Penicillin Absorption

Penicillins can bemetabolized topenicilloic acids inman, theextentbeing dependent on thepenicillin structure. Inthephenoxypenicillin series, phenoxymethyl penicillin was foundtobeparticularly unstable, butthehigher homologues were more stable. Intheisoxazolyl series, oxacillin was unstable, andprogressive insertion ofhalogen inthephenyl ringincreased stability. Ampicillin andamoxycillin showed some instability, ampicillin possibly being themore stable. Afterintramuscular administration, carbenicillin was very stable inthebody,ampicillin was fairly stable, andbenzyl penicillin was unstable. Itisimportant totakeintoaccountthepenicilloic acidcontent of urine whenestimating total absorption ofapenicillin. Increased stability inthe bodyaswell asslower renal clearance can leadtohighconcentrations inthe serum. Penicilloic acids seemedtobemore slowly cleared fromthebodythan penicillins. Theliver isprobably thesite ofinactivation. Thepresent investigation ofthefateof penicillins inhealthy humanswascarried out asapreliminary tostudying whathappens in humanswithvarious types ofbacterial infection. Penicillins canbreak downtobacteriologically inactive penicilloic acids byhydrolysis of thef,-lactam ring, a reaction whichoccurs slowly inaqueous solution butrapidly inthe presence of,B-lactamase, anenzymeproduced bymanybacteria. Therehasbeenverylittle workpublished on theoccurrence ofthis reaction while penicillins arecirculating inthebodyofman.However, Bimer(2)reported thechromatographic detectionandassayofpenicilloic acids inhuman urine samples after oral administration ofpenicillin V andphenethicillin. Birner foundhigh concentrations ofpenicilloic acidinurine, the concentrations oftenbeing ashighorhigher thanthose ofthepenicillin. Fromthisitwas clear thatthere wasconsiderable destruction in thebody, whichisconfirmed byourownwork, butBirner didnotcalculate theproportion of thedoseexcreted aspenicillin ordiscuss the significance ofhisresults. Hismethods were veryinvolved anddepended onsolvent extractionfollowed bythin-layer chromatography, removal fromtheplate, nitration, andspectrophotometric assay. Thismethodisthusonly 463 applicable tosolvent-extractable penicillins.

M. Cole

Papers

Metabolism of Penicillins to Penicilloic Acids and 6-Aminopenicillanic Acid in Man and Its Significance in Assessing Penicillin Absorption

Metabolism ofPenicillins toPenicilloic Acids and6-Aminopenicilla nic AcidinManandIts Significance inAssessing Penicillin Absorption