405 IN-VITRO MINOCYCLINE ACTIVITY AGAINST TETRACYCLINE-RESISTANT STAPHYLOCOCCUS AUREUS

SiR,-Our experience of in-vitro susceptibility to minocycline of tetracycline-resistant Staphylococcus aureus differs completely from that of Leigh and Simmons.1 We used disc-diffusion sensitivity to test for resistance against tetracycline (25 g.) and minocycline (10 g. and 30 jig.). An organism was regarded as resistant when it grew up to or within 2 mm. of the disc margin. Oxford staphylococcus (N.C.T.C. 6571) was used as the control organism. Of 152 tetracycline-resistant strains isolated from infected patients, only 33 (22%) seemed to be sensitive to minocycline (zone radius 10-13 mm.). There was very little difference in the zone sizes produced by the high and low strength discs. All the isolates tested were resistant to penicillin, but none was resistant to methicillin. When minimum inhibitory concentrations (M.l.c.) were measured by the tube dilution technique using an inoculum

......

1-’’’’’

1111.

fig. I-Susceptibility of 152 strains of Staph. cycline and tetracycline.

M.B.C. MICROGRAM

aureus to

mino-

per mi.

Fig. 2.-M.B.C. of minocycline against 152 tetracycline-resistant

Staph.

aureus

given. Nevertheless, bearing in mind the blood-level expected after the usual recommended oral dose (2-5 µg. per ml.), 22% of these tetracycline-resistant strains must have been sensitive to minocycline. Unless there is wide geographical variation, this difference in the results cannot be explained. Since the strains were not phage typed it is not possible to attribute this resistance to a particular phage-type pattern. Minocycline is regarded by some workers as the drug of choice for eradicating meningococci from the nasopharynx of carriers, but because of its acute and often severe vestibular effect this opinion may have to be reconsidered.3,4 However, minocycline inhibits Candida spp.,5 and may prove useful when there is a risk of superinfection owing to the use of a conventional tetracycline. Minocycline is definitely more active in vitro than tetracycline, but because of its cost it is unlikely to replace tetracycline altogether for the treatment of minor

not

strains.

of 105 bacteria per ml., these 33 strains were inhibited by concentrations of 2 µg. per ml. or lower of minocycline. Most of the remaining strains were inhibited by 4-32 µg. per ml. (fig. 1). The M.l.C. of the Oxford staphylococcus was 012 µg. per ml. The minimum bactericidal concentration (M.B.C.) of minocycline in the 33 sensitive strains was 4 µg. per ml. or less, leaving no surviving cells. The other strains required much higher concentrations of minocycline for complete bactericidal action (fig. 2). In a previous study in the U.S.A., 87 % of the tetracyclineresistant Staph. aureus strains were sensitive to minocycline, but only 13 strains were examined.2 Lately, in a survey in England on 48 such strains, 96% were susceptible to this new antibiotic.1 However, the criteria of resistance were

infections. Public Health Laboratory, Whipps Cross Hospital, Leytonstone, London E11.

B. CHATTOPADHYAY E. HARDING.

EFFECT OF BROXYQUINOLINE AND BROXALDINE IN LEPROSY SIR,—A few months ago, a patient with lepromatous leprosy came to me in a reaction stage. During the pretreatment investigations, he was found to have intestinal amcebiasis. He was advised to take a combination of broxyquinoline 500 mg. and broxaldine 100 mg. three times a day for one week. Treatment for leprosy was to start after this. Unfortunately, after this visit, the patient stopped coming and he was only seen by me again after 6 months. To my surprise, I found that his lepromatous lesions showed remarkable clinical improvement. During this period he had continued to take the abovementioned combination of broxyquinoline and brobenzoxaldine in the dose suggested. He had not taken any specific treatment for leprosy, nor had he gone to any other leprosy centre. Broxyquinoline and broxaldine are dibromo derivatives of quinoline and quinaldine respectively. In a specific ratio of 5/1 they have been shown to act synergistically against several pathogens.6 The clinical improvement in this patient prompted me to treat more cases of lepromatous leprosy with this combination at the dose mentioned above. So far twelve patients have been treated on this schedule-six of them for 9 months and six more for 6 months. Appreciable clinical and bacteriological improvement was noticed within 3-4 months. The nodules showed shrivelling within about 6 weeks and flattening in about 4 months. Generalised infiltration gradually became less, leaving a dry, wrinkled skin. Microbiologically, there has been a rapid fall in the morphological index and an appreciable fall in the bacteriological index. Throughout the period of therapy no serious adverse reactions have been encountered. These patients did not receive any specific

anti-leprosy treatment. My experience with these patients seems to indicate that a combination of broxyquinoline and broxaldine might have some specific effect in leprosy. This possibility should be further investigated. 79/81 Anna Salai, Madras 600006, India.

C. S. GANGADHAR SHARMA, Deputy Director of Health Services

(Leprosy), Tamil Nadu.

4.

Guttler, R. B., Counts, G. W., Avent, C. K., Beaty, H. N. J. infect. Dis. 1971, 124, 199. Williams, D. N., Laughlin, L. W., Lee, Y. H. H. Lancet, 1974, ii,

5. 6.

Waterworth, P. M. J. clin. Path. 1974, 27, 269. Brack, A. Arzneimittel-Forsch. 1962, 12, 144.

3.

744.

1. 2.

Leigh, D. A., Simmons, K. Lancet, 1974, i, 1006. Frisk, A. R., Tunevall, G. Antimicrob. Ag. A. 1968, 8,

335.

Letter: In-vitro minocycline activity against tetracycline-resistant Staphylococcus aureus.

405 IN-VITRO MINOCYCLINE ACTIVITY AGAINST TETRACYCLINE-RESISTANT STAPHYLOCOCCUS AUREUS SiR,-Our experience of in-vitro susceptibility to minocycline...
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