The efficacy of tobramycin in the treatment of ulcerative colitis.

This paper reports a double-blind placebo-controlled trial of oral tobramycin in acute ulcerative colitis. Eighty-four patients with an acute relapse of ulcerative colitis were randomized to receive oral tobramycin or placebo for 1 week as an adjunct to steroid therapy. At endpoint, 31 of 42 (74%) in the tobramycin group achieved complete symptomatic remission compared with 18 of 42 (43%) in the placebo group (P = 0.008). The tobramycin group achieved better histological scores (P less than 0.05) at endpoint. These findings show that treatment with oral tobramycin improves the short-term outcome of patients with ulcerative colitis in relapse.

Effect of antibiotic resistance on the survival of Staphylococcus aureus.

The survival of strains of Staphylococcus aureus on glass at 30 degrees C, 37 degrees C, and room temperature was compared with derivatives of them that had either lost or gained naturally occurring antibiotic resistance. In other properties the sets of strains were identical. Neither loss nor gain of antibiotic resistance (methicillin, penicillinase, streptomycin, tetracycline, erythromycin, neomycin) altered survival.

Lack of evidence for mutation to erythromycin resistance in clinical strains of Staphylococcus aureus.

The properties of 100 erythromycin resistant strains of Staphylococcus aureus obtained from clinical material have been compared with the properties of mutants selected in vitro for resistance to erythromycin. The properties, including inducibility of the resistance and cross-resistance to spiramycin and lincomycin, of the two groups of isolates were always different. The risk that staphylococci will mutate to erythromycin resistance during therapy with this antibiotic is remote.

Susceptibility of the "penicillinase-resistant" penicillins and cephalosporins to penicillinase of Staphylococcus aureus.

The activities of some semisynthetic penicillins and cephalosporins have been tested against clinical strains of Staphylococcus aureus. The apparent activity in vitro varies with the method of testing used. Determination of MICs using light inocula fails to detect the destructive effect of penicillinase on the antibiotic. This was, however, demonstrated reproducibly by the use of a technique in which a heavy inoculum was pre-incubated for two hours before application of antibiotic to wells. This method of testing probably represents most of the clinical situations in which the drugs are used since both in vitro and in vivo a growing culture is exposed to an antibiotic gradient. Flucloxacillin was inactivated by penicillinase considerably more than either methicillin, cloxacillin, or nafcillin. Cephaloridine was the most vulnerable of the cephalosporins. Cephazolin, cephalothin, and cephalexin were intermediate. Cephradine was the least hydrolysed by staphylococcal penicillinase. It is recommended that the activities of all penicillins and cephalosporins against staphylococci should be tested by diffusion at 37 degrees C with pre-incubation of the culture for two hours at this temperature.

Present significance of resistance to trimethoprim and sulphonamides in coliforms, Staphylococcus aureus, and Streptococcus faecalis.

The incidence of trimethoprim resistance in coliforms and multiresistant strains of Staphylococcus aureus isolated in Bristol from 1970 to 1972 is low-2.3 and 1.0% respectively. The resistance is probably intrinsic; there is no evidence that it is R-factor or plasmid mediated. A single mechanism that confers resistance to both trimethoprim and sulphamethoxazole has not been detected. Normal growing one-step mutants of S. aureus and Escherichia coli resistant to trimethoprim could not be isolated in vitro. For these reasons cotrimoxazole should retain its usefulness against these bacteria for some years. However, contrimoxazole was found not to be bactericidal against many coliforms. The usefulness of cotrimoxazole against Streptococcus faecalis seems limited because mutants resistant to trimethoprim occurred at high frequency in one step.

Effect of thymidine on activity of trimethoprim and sulphamethoxazole.

Thymidine at levels as low as 0.05 mg/1 reduces the activities of sulphamethoxazole and trimethoprim and their combination in vitro. Using a biological assay procedure, levels of thymidine greater than this were interpreted as being present in urine. The addition of sulphamethoxazole and trimethoprim, singly or in combination, to urine obtained from patients with urinary tract infections showed that all the antibacterial effect towards sensitive organisms was due to the trimethoprim component. It is suggested that trimethoprim should replace the combination co-trimoxazole for the treatment of some lower urinary tract infections, and that laboratory media, if they are to resemble the clinical environment, should contain thymidine.

Unusual skin sepsis due to a strain of multiresistant Staphylococcus aureus.

A strain of Staphylococcus aureus resistant to as many as nine distinct antibiotics has shown unusally high virulence as indicated by its ability to cause an epidemic of furunculosis amongst hospital nurses.

A reappraisal of the antibacterial action of cotrimoxazole in vitro.

The in-vitro action of the sulphamethoxazole/trimethoprim combination (cotrimoxazole) against coliforms, Proteus spp, and Staphylococcus aureus was re-examined. In nutrient broth the components of cotrimoxazole did not produce bacteriostatic synergy against most sulphonamide-resistant and a significant proportion of sulphonamide-sensitive strains. Any bactericidal action appeared to be due to the trimethoprim component. After addition to urine the combination was only bacteriostatic against most coliforms and Proteus spp over six hours. Further clinical trials are needed to determine the circumstances under which cotrimoxazole is superior to either trimethoprim or sulphonamides against some infections, particularly of the urinary tract.

Failure to demonstrate an advantage in combining sulphamethoxazole with trimethoprim in an experimental model of urinary infection.

Co-trimoxazole was found to have a predominantly bacteriostatic effect upon 28 urinary isolates of Enterobacteriaceae in nutrient broth and was never bactericidal in artificially infected urine. The components of co-trimoxazole were tested individually and trimethoprim was found to be at least as effective as co-trimoxazole in nutrient broth and in urine. Trimethoprim alone produced some bactericidal effect in urine but this was antagonized by sulphamethoxazole. Laboratory tests for evaluating these drugs may give a misleading impression of their activity in vivo. Further clinical comparisons should therefore be made between trimethoprim and cotrimoxazole to determine when trimethoprim should be used in preference to the combination.

Properties of an unusual genetic element in Staphylococcus aureus.

A strain of Staphylococcus aureus (M7) contains a transmissible element determining production of penicillinase, and resistance to cadmium ions, neomycin, streptomycin and kanamycin (CPNS). This element was transferred either in toto or in fragments at low frequency from strain M7. The fragment (NS) possesses features typical of chromosomal genes and the fragment (CP), like (CPNS) itself, exhibits plasmid features. The element (CPNS) is transferred in mixed culture at high frequency, up to 10(-3), between other strains of staphylococci. Lysogenisation of the recipient increases the frequency of transfer. The frequency of transduction of (CPNS), (CP) and (NS) from cell-free lysates corresponds well with the transfer frequency of each of these elements in mixed culture. A possible mechanism for the evolution of (CPNS) is discussed.

Effect of plasmid carriage on the virulence of staphylococcus aureus.

The possession of any of eight different plasmids by Staphylococcus aureus strain 649--either singly or simultaneously (in no. 649MR)--caused changes in growth kinetics. Six of the plasmids caused an increase in exponential doubling time (by 8-25%), and most also altered the duration of the lag period. Strain 649MR was significantly less virulent for 10-day chick embryos than the corresponding plasmid-negative culture (no. 649N). The avirulence persisted even after loss of the plasmids from no. 649MR. The presence of a single plasmid specifying tetracycline resistance produced a moderate reduction in virulence, but chromosomal tetracycline resistance had an insignificant effect on it. The decrease in virulence could not be attributed to reduced formation of soluble products. It probably resulted from alterations in the cell surface, but membrane-polypeptide profiles of virulent and avirulent cells lacking plasmids were similar. Survival of strains 649MR and 649N on glass was identical. Therefore, reduction in the incidence of staphylococcal sepsis may be due in part to loss of virulence that has resulted from plasmid carriage.

Transfer of gentamicin resistance between cultures of Staphylococcus aureus in nutrient broth, serum and urine.

Only one of 23 gentamicin-resistant cultures of Staphylococcus aureus transferred its resistance in mixed culture in broth to the non-lysogenic S. aureus strain 1030; the transfer-frequency was 10(-3)-10(-4). Transfer between non-lysogenic clones of strain 1030 occurred at a similar frequency in urine, and at a frequency of approximately 10(-1) in serum. The resistance determinant for transfer between non-lysogenic clones was usually linked to phage genome, as shown by the possession by resistant recipients of immunity to typing phage 75, plaque-forming particles in their culture filtrates and inducibility by mitomycin C. Stability of the resistance on storage and transduction kinetics suggested that these genes were chromosomal. Two resistant derivatives were isolated that had lost some phage functions and were unable to transfer their resistance further. The epidemiology of gentamicin resistance may in part be explicable by the transient formation of an auto-transmissible element with subsequent integration of the resistance genes into a variety of replicons (i.e., transposition).

Further evolution of a strain of Staphylococcus aureus in vivo: evidence for significant inactivation of flucloxacillin by penicillinase.

A strain of Staphylococcus aureus (no. FAR4) has been isolated at intervals, for 32 months, from the sputum of a patient with cystic fibrosis of the lung. Changes in the properties of isolates of this strain over the first 18 months have been reported previously (Lacey et al., 1973 and 1974). During the last 14 months (May 1973 to July 1974), further evolution has occurred to produce a total of 31 distinct phenotypes. Recent changes are as follows. 1. The ability of isolates to produce penicillinase in vitro was closely correlated with flucloxacillin therapy. Inactivation of flucloxacillin by penicillinase was demonstrated by diffusion testing (but not MIC determination) in vitro and may have occurred to a significant extent in vivo. 2. Lincomycin-resistant mutants slowly disappeared from the sputum after the termination of clindamycin therapy. 3. All of the recent isolates were resistant to erythromycin, possibly because of the linkage of the genes coding for erythromycin resistance with those coding for the production of delta-haemolysin; delta-haemolysin may be an important "virulence factor".

Sensitivity of staphylococci to fatty acids: novel inactivation of linolenic acid by serum.

The inhibition of coagulase-negative staphylococci and Staphylococcus aureus of human or animal origin by most free fatty acids was similar, but coagulase-positive staphylococci were sensitive and coagulase-negative cultures were resistant to linolenic acid. Animal strains of S. aureus were more sensitive to linolenic acid than were human strains. These differences were reflected in the relative abilities of the three categories of strains to survive on human skin. The antibacterial effects of 20 mg of linolenic acid were inactivated by 1 ml of serum in vitro. A test organism seeded on to skin also survived better if first suspended in serum. The mechanism of the interaction between serum and linolenic acid may be due to a detergent effect of the serum and could account for colonisation of diseased skin with S. aureus. Cultures of S. aureus seeded on to human skin were rapidly killed after the skin has been covered with linolenic acid. The possibility of therapeutic use of linolenic acid as an antibacterial agent should be explored.

Variation in the properties of a strain of Staphylococcus aureus isolated over three months from a single hospital.

A strain of Staphylococcus aureus has been isolated from a hospital environment over 3 months. Every isolate was lysed by phage 77, had high-level resistance to streptomycin, and was resistant to about 250 pg per ml of both tetracycline and sulphonamide; a combination of sulphamethoxazole and trimethoprim produced little bacteristatic synergy towards each isolate. All These organisms were thus considered to be "the same"; the variation in other properties was probably due to rapid evolutionary change in vivo. the variation in senxitivity to methicillin and neomycin, and the absence of penicillinase production in some isolates, probably indicated loss of the relevant genes. Several isolates had probably acquired resistance to lincomycin by a one-step mutatuon in vivo. The usefulness of lincomycin and analogues in treating staphylococcal infections seems limited.

Antimicrobial effects of trimethoprim and sulphadiazine in infected urine and blood.

Sulphadiazine and trimethoprim in a wide range of concentrations were added to urine from patients with untreated urinary-tract infections. At therapeutic concentrations, the antibacterial activity of trimethoprim was not increased by the addition of sulphadiazine. Exposure of Escherichia coli to trimethoprim in urine was not associated with an increase in resistance to that agent. It was also not possible to select, in vitro, stable resistance to trimethoprim in sensitive cultures of E. coli. At therapeutic levels in blood, trimethoprim and sulphadiazine singly produced mainly a bactericidal action on pathogens responsible for urinary-tract infections. Sulphadiazine occasionally enhanced the effect of trimethoprim at subtherapeutic levels. These findings support the need for further evaluation of trimethoprim alone, rather than its use as a combination with a sulphonamide.

Evaluation of the Rosco system for the identification of Listeria species.

The Rosco system was used to identify previously confirmed isolates of the seven currently recognised species of Listeria. These included reference cultures and recent isolates from clinical material, food products and environmental sources. The system identified all correctly. Results were obtained after 4 h if heavy inocula, as suggested by the manufacturers, were used. The method may be used to aid identification of isolates of Listeria from clinical and non-clinical specimens and would be of particular value in laboratories examining small numbers of isolates relatively infrequently. Essential tests not included in the system are beta-haemolysis on sheep-blood agar and the CAMP test.

Properties of methicillin-resistant Staphylococcus aureus colonizing patients in a burns unit.

One hundred cultures of methicillin-resistant Staphylococcus aureus (MRSA) were isolated from patients in a Regional Burns Unit between December 1984 and May 1985. These organisms produced large amounts of beta-lactamase which readily hydrolyzed flucloxacillin but they were sensitive to teicoplanin, dicloxacillin and cephalothin at 37.5 degrees C. The MRSA strains did not differ from methicillin-sensitive isolates in sensitivity to unsaturated fatty acids, survival in serum and plasma or desiccation. However, each culture of this strain was negative or only weakly-positive for bound coagulase and cell bound protein A. Few (eight out of 44) cultures contained plasmids and the resistance to four antibacterials was not transferable in mixed cultures. No attempt was made to isolate patients colonized with MRSA which were rarely isolated elsewhere in the hospital.

Effect of recent food on estimation of high-density lipoprotein and total cholesterol in normal subjects.

Magnesium/phosphotungstic acid was confirmed as specific for precipitation of chylomicrons, low-density and very low density lipoprotein particles in serum from healthy volunteers who were either fasting or who had eaten egg yolks or a salmon sandwich containing Flora margarine 2 hours previously. In eight subjects who ate salmon sandwiches that contained butter or Flora margarine, neither the total cholesterol nor the high-density lipoprotein (HDL) cholesterol differed significantly from the fasting level over 7 hours. In eight subjects, egg yolks also did not alter significantly either the total serum cholesterol or the HDL cholesterol at 1/2, 1, 1 1/2, 2, 5, and 7 hours after eating. Patients may be screened for HDL cholesterol and total cholesterol estimation when not fasting. However, individual subjects showed variation in their total cholesterol and, particularly, HDL cholesterol over a three-month period. Replicate analysis of HDL cholesterol may be required for its complete assessment.

Rarity of tylosin resistance in human pathogenic bacteria.

Of 3812 human cultures of Staphylococcus aureus, Streptococcus pyogenes and Campylobacter species only 1.0 per cent were resistant to tylosin, an antibiotic used extensively in animals but not in man. There was no evidence for a significant animal source of these resistant cultures, a result which provides further evidence for the rarity of the flow of resistant organisms (or their genes) from animal sources to human beings.