A new selective medium forHaemophilus pertussis, containing a diamidine, sodium fluoride and penicillin

Abstract

1. A highly selective medium forH. pertussishas been made by incorporating 4:4'-diamidinodiphenylamine dihydrochloride (M & B 938), penicillin and sodium fluoride in a partially defined base.2. M & B 938 has an interesting selectivity which is much influenced by its environment, especially by the ionic composition of the medium. No pattern has emerged from a study of the effects of eighty salts and many other substances on its activity; but the gain in selectivity forH. pertussisproduced by cysteine and magnesium malonate has been usefully exploited.3. In a strict comparison with Bordet-Gengou the new medium yielded 28% more positive cultures from per-nasal swabs and 75% more from post-nasal swabs. With the new medium the incidence of serious rival growth from any part of the nasopharynx has been about 4% and, in contrast with Bordet-Gengou, postnasal swabs have yielded as many positive cultures as per-nasal swabs.4. The new medium is simple to make, stable, reliable, economical of material and time and suitable for routine use with per-nasal, post-nasal or supralaryngeal swabs, sputum or vomit.5. The new medium growsH. parapertussispoorly; but a highly selective medium forH. parapertussisis easily made by adding streptomycin and penicillin to Bordet-Gengou.6. Whatever the medium, the nature and number of swabs are important factors affecting the isolation ofH. pertussis:with the new medium positive diagnoses from per- and post-nasal swabs taken at the same time were about 40% more than from either swab alone.7. A statistical analysis strongly supports the opinion of Bradford & Slavin (1940) that the relatively poor results with post-nasal swabs on Bordet-Gengou medium are due to the overgrowth ofH. pertussisby rivals rather than to the absence ofH. pertussisfrom the pharynx. It also indicates that the expectation of isolatingH. pertussison Bordet–Gengou varies directly with the numbers present and inversely with the numbers of rivals, especially of diphtheroids and streptococci.8. Addition of 32μg. stilbamidine di-isethionate and 0·25 unit penicillin/ml. to Bordet–Gengou makes an effective selective medium for oral streptococci related to, or of, groups K and L, but not forH. pertussis.I wish to thank my clinical colleagues, especially Dr N. O. Richards and Dr A. Bogdan, for kindly sending swabs from their patients, Professor R. J. V. Pulvertaft for his continuous support, Dr J. A. Fraser Roberts for advice and help with the statistics, Dr A. J. Ewins and Dr H. J. Barber, May and Baker Ltd., for gifts of aromatic diamidines, Dr H. King for gifts of alkyl diamidines and Mr M. Breach, F.I.M.L.T., and Mr A. Drake, F.I.M.L.T., for their help with the preparation of sera, media and routine cultures. I am indebted also to the Central Research Fund of London University and to the Governors of Westminster Hospital for grants for the purchase of materials.

Antigenic modulation ofBordetella pertussis

“…In C mode, however, no differences were found: both strains had the same antigenicity, absorbing power and agglutinability. To see if these strains were exceptional, and also compare the I modes of different strains, twenty-five more strains, isolated at Westminster during 1953, were subcultured from their medium of isolation (Lacey, 1954) in parallel at 350 C. on three media: Bordet-Gengou (for X mode), EMP MgSO4 0-75, NaCl 3-25 (for I mode) and EMP MgSO4 4-0 (for C mode), and then examined for antigenic differences. From the results, summarized in Table 15, it is concluded that serotypic differences are demonstrable only in X mode.…”

“…While developing a selective medium for Bordetella pertussis (Lacey, 1954) it was found that a crude rabbit serum against B. parapertUwsis, which agglutinated B. pertu88is on the slide to a titre of 800, failed, even at a titre of 2, to agglutinate the same strain of B. pertussis grown on Bordet-Gengou medium containing magnesium sulphate in place of sodium chloride. This difference was over a hundred times greater than that often observed between growths of the same strain of bacterium from different environments.…”

The Carrier State in Pertussis

“…The nasopharyngeal swabs were taken by a specially instructed nurse and subcultured on Lacey's medium which has been shown to give a high percentage of isolations (8). The nasopharyngeal swabs were taken by a specially instructed nurse and subcultured on Lacey's medium which has been shown to give a high percentage of isolations (8).…”

Cephalexin-supplemented Jones-Kendrick charcoal agar for selective isolation of Bordetella pertussis: comparison with previously described media

“…As seen in the data presented in Table 1, both penicillinand cephalexin-supplemented media were slightly more inhibitory for the growth of B. pertussis than was the medium containing methicillin or the antibiotic-free medium. With regard to cephalexin, this was more than compensated for by its increased ability to suppress the growth of NPF (Table 2), since the presence of NPF has an inhibitory effect on the growth of B. pertussis (7). Although methicillin was less inhibitory for the growth of this organism than either penicillin or cephalexin, it was also less inhibitory for the growth of NPF when compared with cephalexin.…”