A method is described for assaying 5-fluorocytosine levels in serum or other body fluids. It is simpler and less expensive than the standard cylinder plate assay and is therefore more practical for routine diagnostic laboratory testing.

Nine ill patients with serologically proved pulmonary infection due to Mycoplasma pneumoniae were treated with 7-chlorolincomycin. The symptomatic responses with 900 to 1,200-mg doses were dramatic.

Contrary to the limited effects of alkyl amides and their corresponding N-derivatives, alkyl amines affected both gram-positive and gram-negative organisms. As with other alkyl derivatives the most sensitive gram-negative bacteria were usually more resistant than the most resistant gram-positive bacteria.

Compounds with a chain-length of 11 to 15 are most active. Although some of the general properties relating the activity of fatty acids to their antimicrobial action are similar to those of amine compounds, the amines are unique in that monounsaturation does not increase compound activity.

The possible modes of action of these compounds are discussed.

Five combinations of antibiotics (ampicillin/gentamicin, cephalothin/gentamicin, carbenicillin/gentamicin, polymyxin/carbenicillin, and carbenicillin/cephalothin) were investigated in vitro and in 148 severe infectious episodes caused by gram-negative bacilli in patients with disseminated cancer. The use of combinations that were synergistic in vitro against the offending microorganism (synergy was defined as occurring when the minimal inhibitory concentration of each of the drugs in the combination was one-quarter or less of the minimal inhibitory concentration of each drug alone) was associated with a significantly better response to antibacterial therapy (P < 0.01) than the use of combinations that were not synergistic against the causative agent.

Staphylococcin 1580, a bacteriocin produced by Staphylococcus epidermidis 1580, is bactericidal to sensitive cells of many gram-positive bacteria and stable staphylococcal L-forms. The bacteriocin inhibited simultaneously the syntheses of deoxyribonucleic acid, ribonucleic acid, and protein, and caused neither degradation of deoxyribonucleic acid nor induction of phages in lysogenic, sensitive cells. After 1 hr of treatment, extensive degradation of ribonucleic acid occurred, which was accompanied by leakage of ultraviolet-absorbing material out of the cell. The incorporation of glucose in acid-precipitable and glycogenlike material was inhibited. Furthermore, the staphylococcin inhibited the transport of glucose, glutamic acid, rubidium ions, and o-nitrophenyl-β-galactoside. The uptake of oxygen was only gradually affected, but the intracellular adenosine triphosphate level fell rapidly to 15% of the control value. The motility of sensitive Bacillus subtilis cells was markedly reduced on treatment. Staphylococcin 1580 exhibited no phospholipase activity. The phenomena are interpreted as resulting from an altered conformation and composition of the membrane, from an inhibition of transport through the membrane, or from a combination of these effects.

Studies were made of the synthesis of β-galactosidase by Escherichia coli in the presence of 5-fluorouracil, streptomycin, and subinhibitory concentrations of chloramphenicol. The preferential inhibition of β-galactosidase synthesis observed in the presence of the above drugs was found to be caused by catabolite repression.

The inhibitory properties of a selected number of β-lactam antibiotics were studied, with the use of three distinct types of β-lactamases. The three enzymes were found to be distinguishable on the basis of their susceptibility to inhibition. Not one of the potential inhibitors tested was found to be a potent inhibitor of all three enzymes, but nafcillin possessed the broadest inhibitory activity. The enzyme isolated from Enterobacter cloacae was found to be the most susceptible. In some cases, the degree of inhibition varied with the time of incubation, and, depending upon the time chosen, widely different observations could be made. It is suggested that, in studies such as these, every consideration should be given to the period of incubation and to the concentration of inhibitor employed. Mixtures of inhibitor and cephaloridine did not always act synergistically against growing bacteria, and a number of reasons for failure are suggested.

A direct relationship was established between the rate of uptake of isoniazid and the action of this drug on in vivo mycolic acid synthesis in Mycobacterium tuberculosis H37Ra. The rate of uptake of isoniazid increased linearly with its external concentration and appeared to reach a maximal value of 52 pmoles per hr per 109 cells at an external concentration of about 13 μm. Correspondingly, the rate of inhibition of mycolic acid synthesis increased with the rise in the rate of uptake of the drug. A 50% inhibition of mycolic acid synthesis occurred when the uptake of isoniazid reached 5.2 pmoles per 109 cells. Calculations showed that this level of drug uptake represents an internal cellular concentration of 9 μm. These results show clearly that the action of isoniazid on the mycolate synthetase system of M. tuberculosis is rapid and that this enzyme system is highly sensitive to the drug.

Gentamicin, sisomicin, tobramycin, and kanamycin were compared in parallel tests in vitro and in vivo against a variety of bacterial strains and species. A number of differences were seen in vitro, in particular: (i) the lower activity of kanamycin, (ii) the greater activity of tobramycin against Pseudomonas, (iii) the greater activity of gentamicin and sisomicin against Serratia, and (iv) the generally similar results with tobramycin, gentamicin, and sisomicin against species other than Pseudomonas and Serratia, with the ranking in order of decreasing activity being sisomicin, gentamicin, and tobramycin. Analysis of disc test results suggested that the gentamicin disc is not adequate for testing the susceptibility of all bacteria to sisomicin or tobramycin. In vivo tests did not confirm all specifics of in vitro tests; results of in vivo tests indicated that sisomicin may be the most active. It is suggested that the place of each of the antibiotics in human therapy can best be evaluated by more rigorous in vivo tests and clinical studies rather than extensive in vitro comparisons.

The in vitro inhibitory and bactericidal activities of spectinomycin hydrochloride were tested against a variety of bacteria. The antibiotic was inhibitory at 31.2 μg/ml to most strains of Escherichia coli, Klebsiella, Enterobacter, and Staphylococcus epidermidis. Concentrations of antibiotic exhibiting bactericidal activity exceeded the inhibitory concentration by at least fourfold. Regression graphs were plotted for results obtained with 30-, 100-, 200-, and 300-μg spectinomycin discs; tentative interpretative standards are proposed.

Clotrimazole (Bay b 5097) is a new synthetic antifungal drug with in vitro activity against Candida spp., Torulopsis glabrata, and Saccharomyces spp. Pharmacological studies in man after the oral administration of 1.5 and 3 g of clotrimazole produced mean peak concentrations in the serum of 1.16 and 1.29 μg/ml, respectively, 2 hr after administration. In six patients taking 1.5 g of clotrimazole every 6 hr, there was a progressive decline in the serum concentrations after administration of a dose on days 1, 4, and 8. Nine other patients begun on a similar schedule manifested gastrointestinal symptoms attributed to the clotrimazole and were unable to complete the study. Concentrations of active drug in the urine were less than 1% of the administered dose.

A rapid method for assay of antimicrobial agents in human serum was modified to provide a method for rapidly assessing the activity of antimicrobial discs being used for susceptibility testing. Each morning, discs are taken from the clinical laboratory's working supply and are applied directly onto test plates which have been inoculated, preincubated, and stored in a refrigerator. Inhibitory zones can be measured within 5 to 6 hr, i.e., before that day's batch of tests is to be set up. If the zone of inhibition for any agent is more than 2 standard deviations below the mean, the discs are discarded and another cartridge is selected from the stock supply for that day's susceptibility tests. In this way, discs of questionable potency are discarded before they are used for testing, rather than waiting until the next day as is usually done with the standard methods. The rapid control test yields zones which are slightly smaller and somewhat more variable than with the standard Kirby-Bauer or agar overlay methods, but the slight decrease in precision is outweighed by the advantages of rapidity and simplicity.

Sec-α-halo-nitro compounds are active antibacterial and antifungal agents, and the sec-bromo derivatives are the most active and stable.

Diumycin A, a new antibiotic, was found to inhibit cell wall synthesis by Staphylococcus aureus, a phenomenon accompanied by accumulation of uridine-5′-diphosphate-N-acetyl-muramyl-pentapeptide. The antibiotic inhibited in vitro peptidoglycan synthesis by particulate preparations of Bacillus stearothermophilus and Escherichia coli by preventing the utilization of N-acetyl-glucosamine-N-acetyl-muramyl-pentapeptide. In contrast to vancomycin, the antibiotics diumycin, prasinomycin, moenomycin, 11.837 RP, and enduracidin do not inhibit particulate d-alanine carboxypeptidase.

The effect of incubation with interferon prior to the stimulation of interferon production (priming) and of sequential treatment with cycloheximide and actinomycin D (superinduction) on the interferon yield from polyinosinic-polycytidylic acid (poly I·poly C)-induced diploid human foreskin cell cultures (FS-3 strain) was studied. Suitable priming with interferon produced, on the average, about an eightfold increase over the control yield, with a greater increase noted on some occasions when the control interferon yield was very low. Under the optimal conditions carefully defined in our experiments, superinduction produced about a 100-fold increase over the average control yield, resulting in interferon yields of about 10,000 reference units from cultures containing about 106 cells. Combined superinduction and priming did not produce yields markedly higher than obtainable by superinduction alone. Essentially similar results were obtained in cultures of human embryonic kidney cells and in FS-3 cells stimulated with other double-stranded polynucleotide inducers. However, stimulation of cells with certain concentrations of a mixture of diethylaminoethyl-dextran and poly I·poly C altered the interferon response; the yield was considerably higher than in cells stimulated with poly I·poly C alone, but it could not be markedly increased further by superinduction.

Sch 14342 is an aminoglycoside antibiotic coproduced as a minor component in the gentamicin fermentation. Sch 14342 was found to have the same antibacterial spectrum as gentamicin in vitro and in vivo, and was approximately one-third as active in mouse protection tests. Sch 14342 relative to gentamicin was one-third as toxic in acute tests in mice, one-eighth as toxic in renal toxicity tests in dogs, and an estimated one-tenth as toxic in cat ataxia tests. Sch 14342 possesses a significantly improved therapeutic index relative to gentamicin with reference to ataxia potential and renal toxicity.

Tests to determine the potential use of a quaternary ammonium resin-triiodide complex as a sterilizing agent showed that it was an ineffective sporicide and that bactericidal activity was impaired by complex milieu.

No cross-resistance between gentamicin and tobramycin was found among 19 recent clinical isolates representing four genera of gram-negative bacilli.

The in vitro activity of five antibiotics against 368 strains of Escherichia coli was determined by use of Mueller-Hinton agar and Oxoid sensitivity test medium. Minimal inhibiting concentrations were essentially identical with both media.

At a concentration of 10 μm, camptothecin inhibited vaccinia deoxyribonucleic acid (DNA) synthesis in HeLa cells. Inhibition of viral DNA synthesis was observed when the drug was added before infection or at 1 or 2 hr after infection. Inhibitory effects of camptothecin on vaccinia DNA synthesis could be reversed, even after exposure to the alkaloid for 2 hr. Viral DNA, isolated from vaccinia-infected, camptothecin-treated cells, displayed an altered sedimentation constant after alkaline sucrose density gradient centrifugation. Incorporation of uridine into vaccinia messenger ribonucleic acid was inhibited by camptothecin, but the activity of ribonucleic acid polymerase, as tested in isolated vaccinia cores, was not affected by the drug. Camptothecin had essentially no effect on replication of poliovirus in HeLa cells.

Silver sulfadiazine (AgSu) was found to interact with isolated deoxyribonucleic acid (DNA) to form nondissociable complexes. These complexes differ in physical and chemical properties from those that are established when silver nitrate is added to DNA. The reaction between AgSu and DNA is visualized as occurring in two stages: (i) a weak and reversible interaction (intercalation) between DNA and the sulfadiazine moiety and (ii) a tight binding involving the silver atom. In the first stage, sodium sulfadiazine competes with AgSu for the DNA.

Even though the addition of silver sulfadiazine (AgSu) to purified deoxyribonucleic acid (DNA) results in the formation of AgSu-DNA complexes, no such complexes were detected in bacteria treated with AgSu. AgSu blocked macromolecular syntheses in treated bacteria, DNA synthesis being slightly more sensitive to this inhibitory action. The ribosomes, ribonucleic acid, and DNA isolated from treated cells were normal qualitatively. Bacteria deficient in DNA polymerase were not more sensitive than their parent strain to the lethal action of AgSu. Radioactive AgSu was localized mainly in the cytoplasmic membrane fraction of treated cells.

A new method for rapid, automatic radiometric measurement of antibiotic effects on bacterial growth was developed and compared with a conventional broth dilutior technique. The radiometric method measures the amount of radioactive CO2 generated by the bacterial metabolism of 14C-glucose in the presence of antibiotics. Antibiotic effect on bacterial growth was standardized by measuring the evolution of 14CO2 3 hr after inoculation. This measurement was found to be quantitatively related to increasing concentration of antibiotic provided the organism was susceptible to the antibiotic tested. In 50 of 179 experiments (28%), each testing one organism against serial concentrations of an antibiotic, the concentration of antibiotic producing a 50% reduction of 14CO2 within 3 hr after inoculation in comparison with a control culture was the same as the minimal inhibitory concentration (MIC) determined by the broth dilution technique. In 129 experiments (72%), the antibiotic concentrations inhibiting 14CO2 release to 50% of the control level were less than the MIC values. Results of the radiometric method were related to those of the broth dilution method by constant factors characteristic of the organism and antibiotic tested. Our results indicate that the radiometric method provides a reproducible, quantitative, rapid, and sensitive measurement of the inhibitory effects of antibiotics on bacterial growth. The constant relationship between the results of the radiometric and conventional technique should facilitate the adaptation of the automated method to clinical testing of antibiotic susceptibility.

A simple photometric assay of β-lactamase activity was developed. The method is based on a decrease in optical density at 620 nm caused by the formation of a penicilloic acid-iodine complex. The enzymatic reaction is instantaneously stopped by the addition of a concentrated iodine-tungstate solution. Data showing the time and concentration dependence of the reaction are presented. By varying both the time of the assay and the concentration of the enzyme, substrates of widely different Vmax values could be assayed. The assay is compared with other methods of determining β-lactamase activity.