The resistance to antimicrobial drugs and the incidence of R factors were determined in coliform bacteria, isolated from stool and environmental (soil, water) specimens from an urban Xhosa community, as well as from a remote drug-frea Xhosa community in the Transkei. The significant reservoir of R factors in the urban environmental and stool specimens indicates the strong selective force of antimicrobial drugs. This contrasts with the low frequency of R faciors from the remote community and its environment. S. Afr. Med. J., 47, 340 (1973)

Marcos, D

Woods, DR

English

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340 S.A. MEDICAL JOURNALEcology of R Factors24 February 1973A STUDY OF URBAN AND REMOTE COMMUNITIES AND THEIRENVIRONMENTSD. MARCOS AND D. R. WOODS, Department of Botany and Microbiology, Rhodes University,Grahamstown, CPSUMMARYTh. resistance to antimicrobial drugs and the incidenceof R factors were determined in coliform bacteria, iso-lated from stool and environmental (soil, water) speci-mens from an urban Xhosa community, as well as froma remote drug-frea Xhosa community in the Transkei.The significant reservoir of R factors in the urban environ-mental and stool specimens indicates the strong selectiveforce of antimicrobial drugs. This contrasts with the lowfrequency of R faciors from the remote community and itsenvironment.s. Afr. Med. l., 47, 340 (1973).In a recent study' it was shown that the incidence ofR factors in bacteria from an urban Xhosa populationwas strikingly high. This high incidence was attributedto the use of drugs among an overcrowded, poor anduneducated population, with inadequate domestic h.ygienefacilities and sewage treatment. It was also ·'cstulatedthat the unhygienic neighbourhood could serve as areservoir for resistant strains.The present study was undertaken to test this hypo-thesis and to determine whether the incidence of Rfactors in the environment would reflect a similarpattern of resistance to that shown by bacteria fromthe inhabiting population. A comparative study wasthus carried out between an urban Xhosa populationand a remote Xhosa population, and their respectiveenvironments.MATERIALS AND METHODSarea of the Transkei is served by only one mISSIOnhospital, and the majority of the people have not beenexposed to antimicrobial drugs. Human stool specimens(90) were obtained only from 'first time' patients atthe mission hospital, with no record of previous contactwith a doctor or hospital. Environmental samples (51)were obtained from the soil, water, rivers, huts, cookingareas and cattle pens.Faecal or environmental samples were incubated insterile, brilliant-green bile broth (Diteo) at 3rC beforestreaking on MacConkey purple agar. Isolated yellownon-mucoid colonies were tested for their ability toform gas at 37°C in brilliant-green bile lactose brothwithin 48 hours. Those which formed gas were regardedas coliforms. Strains which were also indole-positivewere classed as Escherichia coli.Resistance Spectra and TransferThe methods for determining drug resistance and itstransfer have been previously described. 1 Selective mediawere prepared as before, except that Wellcotest agarwas used in the case of trimethoprim and Septrin (Septrin-sulphamethoxazole 23,5 p.g + trimethoprirn 1,5 p.g).RESULTSThe results shown in Table I indicate the strikingdifference between the incidence of resistance and Rfactors among bacteria from urban and from remotecommunities and their environments. Only 2 strainsfrom the remote population were found to transferresistance, while no strains isolated from the environmentTABLE I. INCIDENCE OF RESISTANCE AND R FACTORSIN COLIFORM BACTERIA FROM URBAN AND REMOTECOMMUNITIES::R = % resistant strains.tTR = % resistant strains which carry A: fBctors.Bacterial StrainsThe urban population studied was a Xhosa communityliving in a crowded, modern township near East London.These people have easy access to hospitals and doctors.and are thus exposed to antimicrobial drugs.Human stool specimens (67) were obtained fromhospitalized patients, and environmental specimens (83)from the soil, water, sewage and drains in the township.The remote population was a Xhosa community fromthe eastern Transkei. These primitive, rural people livein thatched, mud huts which are clustered in groupsof 5 to 10, each with its own cattle pen. This vastRemote populationRemote environmentUrban populationUrban environmentNo. ofstrainstested90516783R*18,925,568,666,3TRt11,8o47,823,124 Februarie 1973 S.-A. M.OllSE TYOSICIUI' 341TABLE 11. RESISTANCE AND TRANSFER PATIERNS FOR INDIVIDUAL DRUGSAemote-- Urbtlnfirst admission I'lemote Xhoea hospital Urb<!!n Xho!!i!1mission hospital environment patients environment(90 strain!!) (51 strains) (67 strains) (83 strains)Drug A' TAt R TA R TA R TAAmpicillin (25 f-lg) e,7 le,7 3,9 49,3 45,4 20,5 29,4Cephalorexin (15 f-lg) 8,g 15,7 5,9 41,0 15,eCephaloridine (15 f-l) 5,5 15,7 7,3 31,3 16,0Chloramphenicol (30 f-lg) 1,1 2,0 19,4 30,7 3,6 66,7Kanamycin (30 pg) -t 18,0 41,7 3,6Naladixlc acid (30 f-lg) 1,5Nitrofurantoin (200 f-lg)Streptomycin (25 f-lg) 11,0 6,0 46,3 9,7 24,1Tetracycline (50 f-lg) 1,1 22,4 26,7 7,2 16,7Trimethoprim (1,5 f-lg) M 8,9 4,8Septrin (25 f-lg) 8,9 1,2+R = % resistant strains. tTR = % r.sistent strains which transfer r.sisunce. = 0%.contained R factors. The incidence of resistance inbacteria from the urban Xhosa and th.eir environmentwas high (68,6°:' and 66,3%, respectively). Of these re-sistant strains, 47,8% from the urban Xhosa and 23,6%from the environment showed transferable resistance.The resistance and transfer patterns for each drugare shown in Table ll.The percentage of resistance was lower in E. coli thanin the other coliform strains from both communities(Table Ill). However, the percentage of these E. colistrains which were able to transfer resistance (43,7%urban; 11,1 % remote) was higher than that of the othercoliform strains (19% urban; 0% remote).TABLE Ill. INCIDENCE OF RESISTANCE AND R FACTORSIN E COLI AND OTHER COLlFO'RMS FROM URBAN ANDREMOTE COMMUNITIESArea E. coli Other coliformsNo. R* TRt No. R TRUrban 106 60,4 43,7 44 84,1 19Remote 125 14,4 11,1 16 75,0 0*R = % resistant strains.tTR = % resistant strains with R factors.DISCUSSIONThe high incidence of resistance and R factors in thehuman stool specimens from the urban Xhosa agreeswith our previous results regarding R factors in urbanXhosa communities.' These results also indicate thatR factors exist and survive in bacteria from the envi-ronment, and that the crowded township studied isserving as a reservoir for R factors.The detection of only 2 R factors in 141 specimensfrom the remote community suggests that R factorshave a Iow incidence in drug-free communities. Thisagrees with the findings of Gardner et al.' and Davis andAnandan.' The striking differences between the urbanand remote communities demonstrate the selective forceof antimicrobial drugs.The resistance and transferable resistance patterns forcephalosporins are interesting. A higher percentage ofresistance to cephalosporins was obtained in bacteriaisolated from the environment than from stool specimens.Only bacteria from the urban environment, particularlythose from sewers, were found to transfer resistance tocephalosporins. The cephalosporins are at present notused extensively in either this urban community orthe mission hospital studied. Cephalosporin was firstobtained from the fungus Cephalosporium isolated froma sewer in Sardinia.' If this fungus is present in theenvironment, it may have resulted in the selection ofcephalosporin-resistant strains.This study indicates that careful monitoring oftransferable drug resistance in overcrowded, unhygienicand underdeveloped communities is essential if the fullbenefit of modern antimicrobial therapy is to be derived.The increasing introduction of antimicrobial drugs inthis remote area of the Transkei should provide auseful opportunity for the study of the evolution of Rfactors.This work WM ~upported by a grant from the South AfricanMedical Research Council. We thank Bristol Laboratories;Burroughs Wellcome; Glaxo-Allenburys, Parke-Davis andRoche for donating drugs or media, and Dr G. H. Beer,Dr E. F. Rose and Mr B. West for assistance with thecollection of samples.REFERENCES1. Wood" D. R., MaTeos, D. and HendTY, D. A. (1972): S. AfT. Med.J., 46, 189.2. GaTdneT, P., Smith, D. H., Beer, H. and MoeJlering, R. C. (1969):Lancet, 2, 774.3. Davi" C. E. and Anandan, 1. (1970): New Eng!. J. Med., 282, 117.4. Abraham, E. P. (1967): Postgrad. Med. J., 43, ,upp!., p. 9.

Ecology of R Factors

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Ecology of R Factors

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