Throat colonization of neonatal nursery staff by Ureaplasma urealyticum : An infection control or occupational health consideration ?

JE EMBREE, M ALFA, J LERTZMAN , G GRAY, C FAJARDO, A YASSI. Throat colonization of neonatal nursery staff by Ureaplasma urealyticum: An infection control or occupational health consideration? Can J Infect Dis 1994;5(5):233-236. Vety low birth weight infa n ts often have protracted respiratory tract colonizalion wilh Ureaplasma urealylicum. To delem1ine whelher prolonged con tact wiU1 very low birth weight infants resulted in higher rates of upper respiratory tract colon ization with this organism for caregivers. throat swabs for U urealyiicum cu lture were obtained from medical. nursing and oU1er support staff' working in the neonatal intensive care and level!! nurseties allhe Heallh Sciences Centre and the Sl Boniface Hospita l in Winnipeg. Manitoba . Th roat colonization by U urealylicum was demonslmled in 7.3% (95% CI 0 to 15.6%) of 41 nurses working in the intens ive ca re nurset·ies but in none of the 48 nurses working in olher locations or the 66 other individua ls tested (P=0.02). However. throat colonization was not s ignificanUy higher a mong the neonatal intensive care nurses than among the women delivering at one of the study institutions. Close contact with very low birth weight infants appears to constitute a minimal risk for increased lhroat colonization with U urealylicum among hospital staff members .

Colonisation par Ureaplasma urealyticum de Ia gorge chez le personnel d'une pouponniere : Le probleme releve-t-il de Ia lutte contre !'infection ou de Ia securite du travail?RESUME : Les enfa nls de lres petit poids a Ia na issancc soulTrenl souvenl d'une colonisation de leurs voies respira loires par Ureaplasma urealylicum.Pour determiner si le contact prolonge avec des enfanls de petit poids a Ia naissance a donne lie u a des laux plu s e levcs de colonisation des voies respiraloires supeneures c h ez le personnel soign a n l. des prclevemenls de gorge pour cu ltu res afin de dcceler Ia presence de U urealyiicum.ont ete oblenus a u pres du personnel medical, infirmier et autre.d'un iles de soins intensifs neonataux el de po uponn ieres de niveau II au Heallh Sciences Centreet au St. Boniface Hospital de Winnipeg au Ma nitoba .Une colonisation de Ia gorge par U urealyticum a ete observee chez 7.3 % (intervall e de confiance de 95% .d e 0 a 15,6 %) des 4 1 infirmie res des pouponnieres de soins inlensifs.ma is n•a ete no tee ch ez a ucune d es 48 infirmieres qui lravailla ienl e n d'a ulres e nd roils.ni c hez 66 a ulres s uj els soumis a eel exam e n (P=0 .02).Toutefois .Ia colon isa tion de Ia go rge n•a pas ete nellemenl plus elevce parmi les infim1ieres de soins intensifs neona taux que panni les accouc hces de run de ces deux etablissements .La proximite des nourrissons d e pe tit poids a Ia na issance semble represenler un ri sque minimc de colon isation accrue de Ia gorge pa r U urealylicum a u pres du pe rsonnel hospilalier.
I NTEREST liAS RECENTLY BEEN DIRECTED TO\VAimS TilE potentia l pathogenic role that Ureaplasma urea-Lyticum may play in the development of acute and c hronic lung disease in very low birth weight infa nts.Th e organism can readi ly be recovered from various sites in lhe infant's respiratory tract as well as from lhe genital lracl of female infants.Both term and prelerm infa nts may become colonized with U urealyticum following delivery .with isolation rates varying from 0 to 53% (l-9).However.colonization is reported more frequently among prelerm infants a nd is often persistent.lasting for several months following birth.Persistent resp iratory tract colonization among prelerm infa nts has been assoc iated with the clcvelopmen l of bronchopulmonary dysplasia (l 0-13).Although there a rc no treatment t1ials.anecdotal reports show th a llh e organism may slill be recovered following therapy with e rythromycin.implying eith er lhallhis drug does nol reliably erad icate it or th at there is subsequent nosocomia l transmission from other infants or from co lonized caregive rs (1 4) .Throat co lonization of adults by U urealyticum has been reported to occur ra re ly but the actual prevalence of U urealyticum in lhe upper res piratory tract of ad ults is unknown (l).Recc nlly .we clocumcntecl U urealyticum throat colonization in 1.8 and 3 .8% of mothers de livering term and prelerm infants.res pec tively.at one of our hospitals (unpubl ished data).li enee .we questioned wheth e r throa t co loniza tion by U urealylicum of adults involved in th e care of these infa nts might b e a pote ntial source of infant infec tion or reinfection in the n eonatal nursery.
As infa nts with bronchopulmonary dysplasia lend to h ave very prolonged hospital slays.th e preva le nc e of U urealyticurn in n eo natal nurseries with a high percen tage of low birth weight infants m ay b e significant.If staff caring for these infants readily become colonized from contact with U urealyticLLm from th e infant's respira tory secretions.th en continuous exposure to infected infants in the n eonatal intensive care selling would be expec ted to result in an increased upper respiratory tract colonization ra te among the hospital staff with close co ntac t with th ese infants compared with othe r staff a nd the gen eral population.To de te rmine whether there was an increased rate of upper respiratory tract co lonization by U urealyticum among neonatal intensive care unit staff.we conducted the following cross-sectiona l study at th e two hospitals in Winnipeg.Man itoba that provide acute and c hron ic care for very low birth weight infa nts.

PATIENTS AND METHODS
Following informed consent.throat swab c ultures were performed on various personnel working in the neon a tal te rti a ry and secondary level intensive care units a t b oth th e Health Sciences Centre (l! SC) a nd St Boniface Hospital (StB) durin g March 1993.
Samples we re obtained using throat swabs for con-234  (1).However. the sites of upper respiratory tract co lon ization in adu lts have not b een slucliecl and a nother method of sampling, s u ch as nasopharyngeal swabs.might have yielded a h igher colonization rate .The issu e of hand carriage was a lso not aclclressecl in this study because the assumption was made that such carriage wou ld be related to upper respira tory tract colonization.Al l nursing.med ical and support staff were invited to participate .The testing was anonymous with only the profession and the unit in which he or she was working when recruited recorded for each incliviclual.
Calgiswabs (Spectrum Laboratories, Ill inois ) were used to collect the throat cultures.They were placed directly into bromo thymol blue broth (B broth) ( 15) and transported clireclly to the microbiology research laboratori es at StB and IISC hospitals.The B broth was incubated aerobically at 37°C and inspected daily for any colour change from yell ow to green (an indication of growth of mycoplasmas).B broth lubes were held for a total of five clays.Once a colour change was cle leclccl.the broth was subcultured onto GM agar (15) to observe colonial morphology.If no colour change was cleteclecl.the B broth was subcultured on clay 3 to check for ureaplasmal growth that might have gone unnoticed clue to competing pH changes .GM agar p lates were incuba ted for 48 hat 37°C in a carbon dioxide incubator.Wh en colon ies were cletectecl a urease spot test was used to clelecl U urealyticwn.
Colon ization rates were compared using lhe lwolailecl Fisher exact lest.

RESULTS
In lola!. 155 ind ividuals agreed lo be leslccl .On ly nin e who were asked lo lake part refused.Nurses involved in direct patient care formed the largest group lesled.The doctors tested included n eonatologists.n eonatal fellows and pedia tric residents (11) as well as consulting pediatricians who h appened lo a llend palienls in lhe unil during lhe lime lh e study was condueled (nine).Th e olher personnel involved includ ed lwo respiratory technologists.ward clerks, clini cal laboratory technologists.pharmacy personne l. occu pational lherapisls.nurses• a ids and cleaning slaff.The coloniza tion rale.lhe number lesled in each unil and lhe number in each professional group a re shown in Table 1.U urealyLicum was isolated from only lhree individu als (2%).All colonized slaff were nurses involved in direct palienl care while working in lhe n eonatal intensive care unils; lhus, lhe ra le of colonization in tha t group was 7.3% (95% C I 0 lo 15.6%) while that in all other groups was 0 (P=0.02).In this study other demographic dala were nol co llec led; however.a pproximately 90% of the nurses a nd 50% of lh e other staff tested were women of reproductive age .

DISCUSSION
U urealyLicum was isola ted from throat s wabs from 2% of all staff and from 7.3% of nurses working in lhe neonatal intensive care units of lhc two hospitals surveyed.The isolation rate in nurses working in lhe intensive care units was significanlly higher than that of other nurses and slaff.However, it was nol s ign ificanlly higher (P=O.l)compared with the rates of throat colonization among women delivering at one of th e study hospitals in a survey conducted during lh e previous year and completed six months before lhis sludy.In lhal sludy.U LLrealyLicum was cultured from lhroal swabs in 1. 8% of 108 mothers delivering al lerm a nd 3.8% of 104 women delivering premature ly (unpublished data).While these results may nol be slriclly comparable because lhe studies were conducted during separate time periods.lhe population served by lh c hospital in which lhe preceding sludy was co nducted is stable.and lhus lhe patient colonization rales we re unlike ly to vary appreciab ly over the shorl lime period thal elapsed between lhe lwo studies.
There may be workplace exposure to U urealyLicwn through lhe intensive care of very low birth weight infants, as implied by the higher rale of isolation from lhroal swabs among lhe nurses in the intensive care unils compared with that of nurses working in oth er unils and of lhe olher groups lesled.The nurses in lh e lerliary care areas had close conlacl wilh venlilaled premature infants .and in the course of lhe ir dulies had frequ ent exposu re lo lhe respiratory secretions of these infants .In con lrasl.nurses in the secondary leve l nurseries did not care for venlilaled palienls and generally had much less contact wilh respiratory secretions.Th e other slaff h ad variable close conlacl wilh lhe patients.and wilh lhe exception of the allending neonatologists.neonatal fellows.pedia!J•ic residents and res piratory therapists, had no conlacl wilh respiratory secretions.However.lhis exposure to secretions does not appear lo place lhe nurses in lhe n eonatal intensive care selling a t our inslilulions al a sign ifi canlly increased risk for res piratory tracl acquisition of the organism compared wilh women who delivered their infants al one of the sludy inslitulions.Carriage of U urealyLicum by lhe nurses may be related lo independent factors related to being primarily women of ch ild -b earing age .Despite lhe 90% predominance of premature infa nts in the neona tal intensive care unils evaluated in lhis sludy.our previous sludy comp leted six months earlier revealed lha t only 9.6% of 115 premature infants ad mitted lo one of lhe unils were colon ized wilh U urealyLicum.This low prevalence of U urealyLicum among infants in one of our instilulions m ay explain why we did nol observe a high rale of throat co lonization among caregivers .Of nole .lhe ra les of genita l isolation of U urealylicum among our pregnant population is approximately 20% .which is lower than most reports in the literature in which ra les vary from 30 to 80% (1 -3.5).In our in s titutions .respira tory lracl carhage of U LLrealylicum by nursing and m edical staff is unlikely lo in crease s ubslanlially lhe risk of infection by lhis organism for infa nts in our nurseries above that of perinatal transmission .However.lhis may be reflective of lhe relatively low prevalence of lhe organsims in our popul a tion .a nd surveys in other centres wilh high er U urealyLicum prevalen ce may yield diffe re nt results.To our knowledge.lhis is the only published study add ressing the issue of U urealyLicum respira tory tract co lonizati on by med ical slaff who provide care for n eon ates.
De termina tion of whether nosocomial transmission occurs from ad ulls who have upper respirato ry lracl carriage of U urealyLicum to pre ma ture infants would be imporla nl before lhe inslitulion of screening and lreatm enl regimens d esigned lo prevent or modify bronchopulmonary dysplasia a mong infa nts vvilh perinalally acquired U urealylicum infec tion.
CAN j INFECT DIS VOL 5 No 5 SEPTEMBER/OCTOBER 1994 Ureaplasma urealyticum throat infection

TABLE l Ureap/asma urea/yticum isolation from staff members in neonatal intensive care units
Wang EL.F'rayha H. Walls J. el al. Ro le of Ureaplasma urealylicum and other path ogens in the clcvc lopmen t of chro nic lung disease of pre matw-il~' • Pedialr Infect D is J 1988:7:547-51.I I. Cassell Gil.Wailes K.B. Crouse DT. el al. Association of Ureaplasma urealylicum infec tion of the lower r esp iratory tract with c hronic lung disease and death in 236 vc ty-low -b irth -weigh l i nfan ts .Lancet 1988: ii: 240-4.12. H or owi tz S .Landau D. Shi nwell ES. cl al. Rcsp i ratoty tract colon ization w i th Ureaplasma urealylicum and bronchopu l monary dysplasia in neonates i n southern Israe l.Pecl ia t r In fec t D is J 1992: I l :84 7 -51.13.Walsh WF'.Stan ley S .Lally KP. el a l.Ureaplasma urea lylicwn clcmonslratecl by open lung biopsy in newborns with chron ic l u n g disease.Ped ialr In fect Di J 199 1: 10:823-7.14.Wailes !ill.C r ouse DT.Cassell GH.An ti b iotic susceptibili ties and the r apeutic options for Ureaplasma urealylicwn i nfec tions in neonates .Pecl ialr Infect Dis J 1992: 1 I :23-9.15.Robertson JA.Bromolhymol blue broth: improved medium lor clclcction of Ureaplasma urealylicwn (T-slrain