J Clin Pathol: first published as 10.1136/jcp.11.3.270 on 1 May 1958. Downloaded from J. clin. Pat/i. (1958), 11, 270. THE SENSITIVITY IN VITRO OF THE PROVIDENCE GROUP OF ENTERIC BACTERIA TO 14 ANTIBIOTICS AND NITROFURANTOIN BY J. E. MIDDLETON From the Louis Jenner Laboratory, St. Thomas's Hospital and Medical School, London (RECEIVED FOR PUBLICATION JANUARY 8, 1958) During the course of an investigation into the oxytetracycline (100 Pg.), chloramphenicol (100 p-g.), antibiotic sensitivity of strains of the Proteus polymyxin (500 u.), and nitrofurantoin 10,000 pg.). per paper disc or group of bacteria isolated from infections of the (The concentration of each drug test tablet is given in brackets.) A zone of inhi- urinary tract (Middleton, 1957) a few strains of bition of growth 10 mm. or more in diameter were examined. This the Providence group also was considered to indicate sensitivity to the anti- group of the Enterobacteriaceae called type 29911 biotics, the discs or test tablets being 5 mm. in by Stuart, Wheeler, Rustigian, and Zimmerman diameter. Any inhibition of growth round the nitro- (1943), and named Providence by Kauffmann furantoin test tablet was taken to indicate that the (1951), has close affinities in many characteristics organism was sensitive to the drug. with the Proteus group (Singer and Bar-Chay, A few strains were also tested by the serial dilution copyright. 1954), and a similarity between strains of the two technique against streptomycin, tetracycline, and ml.) of a groups was found here in their common resistance chloramphenicol. A standard drop (0.02 dilution of an overnight broth culture was to many antibiotics in vitro. An opportunity has 1/10,000 to a series of tubes containing 1 ml. of nutrient a of Provi- added since arisen to study larger number broth plus doubling dilutions of each of the anti- dence strains and a relationship has also been biotics separately. These results, as also those of the demonstrated between the biochemical types of disc tests, were read after about 18 hours' incubation Providence strains and their antibiotic spectra. at 37° C. http://jcp.bmj.com/ Results Material and Methods The biochemical classification of the 40 Provi- Forty Providence strains were examined. Nine in Table I. All the strains of which eight were dence strains is shown were isolated in this laboratory, were of Ewing's from urine and one from faeces. The 31 other isolated from urinary infections strains were obtained from Dr. K. P. Carpenter. biotype 27. Director of the Dysentery Reference Laboratory. TABLE I on September 30, 2021 by guest. Protected Central Public Health Laboratory, Colindale, London. BIOCHEMICAL CLASSIFICATION OF 40 PROVIDENCE These were recently isolated organisms which had STRAINS sent there from various centres in Britain and been Ewing, Tanner, No. of Ewing, Tanner, No. of the Commonwealth; one was from urine, 29 from and Dennard and Dennard Strains faeces, and the source of one strain was unknown. Biochemical Group Stra Biotype 5 The identification of the strains isolated in this 4 4 laboratory was based on the criteria described by 1 20 47 Kauffmann (1954). This identity was kindly confirmed 6 4 by Dr. Carpenter, who, in addition, classified these 21 7 strains, and those supplied by her, into the bio- 2 20 27 13 chemical subdivisions described by Ewing, Tanner, and Dennard (1954). The dried disc technique described by Fairbrother All the 40 strains were resistant to penicillin, and Jennings (1955) was Llsed for testing the sensi- novobiocin, bacitracin, erythromycin, spiramycin, tivity of the strains to penicillin (2.5 units), novobiocin and oleandomycin. All were sensitive to neo- (20 ug.), bacitracin (10 u.), erythromycin (10 pag.), mycin, soframycin, and nitrofurantoin. Fifteen spiramycin (60 PJg.), oleandomycin (10 pg.), strepto- bio- g.-). per cent. of strains belonging to Ewing's mycin (80 pg.), neomycin (50 'ig.), soframycin (50 1 of bio- tetracycline (100 ,tg.), chlortetracycline (100 ,ig.). chemical group and 10°b Ewing's J Clin Pathol: first published as 10.1136/jcp.11.3.270 on 1 May 1958. Downloaded from SENSITIVITY IN VITRO OF PROVIDENCE GROUP OF ENTERIC BACTERIA 271 TABLE II BACTERIAL SENSITIVITY IN VITRO OF 40 PROVIDENCE STRAINS (DISC TEST) Percentage Sensitive to Certain Antibiotics and Average Diameter of Zone of Inhibition Organism StraiNo. of of Growth (mm.) of All Strains Streptomycin Tetracycline Chlortetracycline Oxytetracycline Chloramphenicol Biochemical Group 1 .. 20 100 45 15 75 100 11-7 (1014)* 9-6 (7-15) 8-7 (6-13) 11-0 (6-16) 15-6 (11-20) 2 .. 20 10 0 0 10 15 6-7 (5-11) 6-4 (5-8) 6-5 (5-8) 7-1 (5-12) 7-8 (5-11) * Limits of inhibition of growth in brackets. Disc diameter 5 mm. chemical group 2 strains were sensitive to poly- oxytetracycline, and chloramphenicol. Biochemic- myxin. With streptomycin, the tetracycline ally these strains resemble strains of Ewing's bio- antibiotics, and chloramphenicol a difference in chemical group 2 and especially biotype 21, sensitivity between strains of biochemical groups although from the details given by Brooke it is not 1 and 2 was found, as is shown in Table II. possible to reclassify the organisms precisely Strains of the former group were mainly sensitive under Ewing's system. Lutz and Hofferer (1955) and those of the latter group resistant to these examined 16 strains; all were sensitive to neo- antibiotics. There was no marked variation from mycin and soframycin, and 11 were sensitive to this general pattern with individual strains of the chloramphenicol, but all were resistant to strepto- biotypes composing these biochemical groups, mycin and the tetracycline antibiotics. Bio- except that all biotype 1 strains tested were resis- chemically 14 of these strains correspond to tant to the tetracycline analogues; biotype 21 Ewing's biotype 4 and the other two to biotype strains were all uniformly resistant to 27. The findings of the present investigation are strepto- copyright. mycin, the tetracycline drugs, and chloram- in general agreement with these results, except phenicol. The average diameters, and the limits, that the four strains of biotype 4 which were of the zones of inhibition of growth found in the tested here were more sensitive to streptomycin disc tests, which were also recorded in Table II, and the tetracycline drugs than those of Lutz and show that the difference in sensitivity between the Hofferer (1955). two biochemical groups was marked. Relatively Lutz and Hofferer showed that Providence large zones of inhibition of growth were obtained strains as a whole have a different antibiotic http://jcp.bmj.com/ with biochemical group 1 strains, whereas with spectrum from that of the four Proteus species, biochemical group 2 strains either no inhibition of each of which has a relatively distinct pattern of growth occurred or only small zones were pro- sensitivity to antibiotics, as has been found by duced. This difference was confirmed by the these authors and Poole (1954) and Potee, Wright, results of the serial dilution tests (Table III), and and Finland (1954). This has in general been was more than 16-fold with each antibiotic. confirmed, but if the antibiotic spectra of the TABLE III strains of Ewing's biochemical groups 1 and 2 are on September 30, 2021 by guest. Protected BACTERIAL SENSITIVITY IN VITRO (TEST TUBE) considered separately they show some resem- blance to the antibiotic spectra of strains of Minimum Inhibitory Concentration of P. morganii and P. rettgeri. Strains of these Pro- Providence Strain Antibiotic (pg./ml.) (Typical) Strepto- Tetra- Chloram- teus species are more often either uniformly sen- mycin cycline phenicol sitive or resistant to streptomycin, the tetracycline antibiotics, and chloramphenicol than those of Biochemical Biotype 6 31 39 7-8 Group 1 P. mirabilis and P. vulgaris. There is also a very Biochemical ,, 21 > 500 > 500 250 close similarity between them and Providence Group 2 ,, 27 >500 250 250 strains in their susceptibility to other antibiotics, and it is these Proteus species which Providence is most like in other respects. Providence strains Discussion are not infrequently confused with the shigellae, Brooke (1951) tested the antibiotic sensitivity of and biochemical group 1 strains have an antibiotic 35 Providence strains isolated from urine. These spectrum similar to that of the latter genus. How- were all resistant to penicillin and sulphathiazole, ever, Proteus and Providence are generally resis- and most of the strains were resistant or only tant to polymyxin, whereas the shigellae are very slightly sensitive to streptomycin, chlortetracycline, sensitive to this antibiotic as was shown by J Clin Pathol: first published as 10.1136/jcp.11.3.270 on 1 May 1958. Downloaded from 272 J. E. MIDDLETON Felsenfeld, Volini, Ishihara, Bachman, and cases which, as a result of prophylactic or repeated Young (1950). chemotherapy, often become infected with resis- It is recognized that strains from only six of the tant organisms. 31 biotypes described by Ewing et al. (1954) have been studied, but, since these six biotypes com- Summary prised 71 % and 62.70% respectively of strains of The sensitivity in vitro of 40 strains of the the biochemical groups 1 and 2 formulated by Providence group of enteric bacteria to 14 anti- these authors during their study of 611 strains, the biotics and nitrofurantoin has been determined. results are considered to be reasonably repre- The strains had been classified biochemically sentative. into the biochemical groups and biotypes It is interesting that all the nine strains isolated described by Ewing et al. (1954). from urine belonged to biotype 27. It is possible The individuality of the antibiotic spectrum of that some of the eight found in this laboratory this group as a whole has been confirmed, but were examples of cross-infection, but it is un- strains of the biochemical groups 1 and 2 differed likely that they all were, since they were isolated in their sensitivity to some antibiotics and con- over a period of a number of years and some were sidered separately showed a resemblance to strains from different hospitals.