APPLED MICROIOLOGY, Jan. 1969, P. 71-77Copyright © 1969 American Society for Microbiology

Neisseria lactamicus sp. n., a Lactose-fermentingSpecies Resembling Neisseria meningitidisDANNIE G. HOLLIS, GERALDINE L. WIGGINS, AND ROBERT E. WEAVER

Bacterial Reference and Serology Units, National Communicable Disease Center,Atlanta, Georgia 30333

Received for Publication 21 October 1968

The biochemical and serological characteristics of lactose-utilizing strains ofNeisseria were determined. These organisms were found in the nasopharynx of manand grew well on Thayer-Martin Selective Medium. They were compared with N.meningitidis to ascertain whether they were variants of this species. Differencesbetween the lactose-using strains and the recognized species of Neisseria were

considered significant enough to warrant designation of a new species, Neisserialactamicus. This group has not been widely recognized as being separate from N.meningitidis; therefore, the normal incidence and clinical significance of theseorganisms has not been fully established. These organisms are oxidase-positive andpositive for #3-D-galactosidase activity; they demonstrate fermentation in KingOxidation-Fermentation Medium; and they produce acid from only glucose,lactose, and maltose, of the 27 substrates incorporated in Cystine Trypticase Agar.Individual strains vary in their ability to grow on Nutrient Agar at both 25 and 37 Cand in their pigmentation on Loeffler Medium. Results indicated that these orga-

nisms are serologically distinct from the N. meningitidis serogroups. Only 34 of 116strains of N. lactamicus were smooth and could be tested by slide agglutination. Noneof the 34 could be grouped as N. meningitidis group A, B, C, D, X, Y, or Z. Thirty-one of these strains could, however, be specifically grouped with antisera preparedwith N. lactamicus strains. Cross absorptions confirmed that N. lactamicus is sero-

logically distinguishable from N. meningitidis.

As early as 1934, Jessen (6) reported a strain ofNeisseria which used lactose, as well as glucoseand maltose, but this organism has not receivedmuch attention in the literature until recentyears. Mitchell, Rhoden, and King (10) studiedseveral strains of the organism serologically, usingfluorescent antibody (FA) and slide agglutinationprocedures. On the basis of reactions obtainedwith these two tests, they reported that some ofthe strains were serologically indistinguishablefrom group B N. meningitidis. Other authors (2,8) have also dealt with these organisms, but none

has made a definite proposal concerning theirproper nomenclature.These organisms are frequently encountered in

carrier studies, and the number of carrier surveyshas increased since the recognition of sulfona-mide-resistant strains of N. meningitidis. As a

result, the number of lactose-using strains sub-mitted to the National Communicable DiseaseCenter (NCDC) for identification or confirma-tion has increased.We reviewed the results of the examinations of

a number of these strains, including approxi-mately 10 serologically smooth cultures, andnoted that several had been submitted with a pre-sumptive identification as nongroupable N.meningitidis. Frequently, the referring labora-tories had not tested them for lactose utilization.In contrast to an earlier report (10), none of thesmooth strains could be grouped as N. meningi-tidis by slide agglutination. These observationsprompted an evaluation of the serological andbiochemical characteristics of the Neisseriastrains that utilize lactose.We attempted to determine whether the lactose-

utilizing Neisseria strains were variants of N.meningitidis group B, whether they constitutedan additional serogroup of N. meningitidis whichwas different from groups A, B, C, D, X, Y, andZ, or whether these organisms were a distinctspecies that was different from any other speciesof Neisseria. Data of the serological and bio-chemical studies of lactose-utilizing strains ofNeisseria are reported.These strains were compared with strains of N.

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meningitidis and a strain of N. subflava, sincethese are the species to which they are mostsimilar.The authors propose that this group of orga-

nisms which utilize lactose be designated a sepa-rate species, Neisseria lactamicus, sp. n.

MATERIALS AND METHODSStrains. Strains of N. lactamicus were received from

17 states in the United States and from Canada. Theneotype strains of N. meningitidis suggested by Bran-ham (1) and the type strains of Slaterus (12) were alsoused. Other strains of N. meningitidis studied wererandom selections of those cultures which state healthlaboratories had sent to this laboratory for identifica-tion or confirmation. A culture of N. subflava (ATCCno. 19243) was obtained from American Type CultureCollection. One previously studied lactose-utilizingstrain of Neisseria (10), no. SD9, was obtained fromthe Bacterial Chemistry Unit, NCDC.

Antisera. Antisera for N. meningitidis groups A, B,C, D, X, Y, and Z were obtained from the BiologicalReagents Section, NCDC, and antisera to groupsA, B, C, and D were purchased from two commercialsources.

Rabbit antisera preparation. Following the methodof Hollis et al. (4), three strains of N. lactamicus(A2894, A5906, and A7515) were used to prepareantisera.

Absorption of antisera. Strains were removed di-rectly from storage at -40 C to plates of 5% rabbitblood Heart Infusion Agar (HIA). The surfaces ofthe plates were moistened with approximately 0.25 mlof Heart Infusion Broth (HIB). The organisms wereharvested following incubation at 37 C for 18 to 24 hrin a candle jar. The antisera to be absorbed werediluted 1:2 in distilled water, and the procedure de-scribed previously (4) was employed.

Serological procedures. Serological methods de-scribed by Hollis et al. (4) were used.

Biochemical procedures. The production of acidfrom 27 substrates was determined in Cystine Trypti-case Agar (CTA) Medium. Stock solutions of sub-strates which had been Seitz-filtered were addedaseptically to give final concentrations of 1%. Thesubstrates tested included glucose, xylose, mannitol,lactose, sucrose, maltose, glycerol, salicin, L-arabinose,adonitol, dulcitol, D-galactose, levulose, mannose,rhamnose, trehalose, raffinose, sorbitol, inositol,cellobiose, inulin, dextrin, glycogen, erythritol,melibiose, melezitose, and starch. Both 1 and 3% con-centrations of ethyl alcohol, isopropyl alcohol, iso-amyl alcohol, methanol, and ligroin in CIA mediumwere also tested. Optimal pH and pH tolerances weredetermined in HIB with pH values ranging from S to10. Sodium chloride tolerance was determined inNutrient Broth (NB) with varying percentages ofNaCl (0.5 to 6.0%). Growth at 25 and 37 C wasdetermined on Nutrient Agar (NA) with a minimalinoculum (one loopful of 24-hr HIB or a light suspen-sion of organisms in HIB). Loeffler Medium was usedin pigment studies. Victoria Blue Fat Medium, asmodified by Davis and Ewing (3), was used to de-

tect hydrolysis of corn oil. Tests for fl-D-galactosi-dase activity on o-nitrophenyl-,3-D-galactopyranoside(ONPG) were performed according to the methodoutlined by LeMinor and Ben Hamida (9), except that5% rabbit blood HIA and 5% rabbit blood HIA with1% lactose were substituted for Lactose-GlucoseSH2 Medium. Oxidative versus fermentative (OF)studies were done with King OF Medium [0.5%Casitone (Difco), 0.3% agar, 0.003% phenol redaqueous; pH 7.31, Difco OF Basal Medium, and CTAMedium with 1% glucose, mannitol, lactose, andmaltose. The media used for the OF studies wereboiled and cooled in an ice bath just before inocula-tion. Duplicate sets of media were inoculated witheach strain, and one set was overlayered with sterilepetrolatum. Shake tubes containing 12 ml of CTAMedium were used to determine the oxygen require-ments. The remainder of the biochemical methodsemployed were outlined by King (7). These includedthe use of MacConkey Agar and Simmons CitrateAgar, and catalase, oxidase, nitrate, and indole tests.

Examination for capsules was carried out withIndia ink.Drug sensitivity. Sulfadiazine sensitivity tests were

performed according to a modified method of P. F.Frank, U.S. Naval Medical Research Unit, GreatLakes, Ill. Briefly, this procedure consisted of in-corporating various amounts of sulfadiazine in 20 mlof Mueller-Hinton (MH) Agar. The agar was pouredinto plates which were marked off in pie-shaped sec-tions. The inoculum consisted of a suspension ofapproximately 108 organisms from an 18-hr HIAslant containing 5% rabbit blood. The inoculum wasstreaked on plates containing 0.05, 0.1, 0.5, 1.0, 3.0,5.0, 10, and 20 mg of sulfadiazine per 100 ml. Plateswere incubated for 18 to 24 hr in a candle jar. Peni-cillin sensitivity tests were performed as describedabove, except that plates containing 0.01, 0.25, 0.05,and 0.1 pg of potassium penicillin (1,600 units/mg)per ml were used. Other antibiotic sensitivity testswere performed with commercial antibiotic discs.Plates of MH Agar were streaked evenly over thesurface with a sterile cotton swab moistened in a 24-hr broth culture. Results were read after 24 hr ofincubation.

Selective medium. Thayer-Martin (TM) SelectiveMedium employing either vancomycin, colistimethate,and nystatin (VCN) or ristocetin with polymyxin Bwas used in MH agar.

RESULTSN. lactamicus organisms were gram-negative

cocci and diplococci which were strongly oxidasepositive. The size of the colonies varied with thestrain and ranged from 0.5 to 1.5 mm in 24 hr onHIA with 5% rabbit blood. Colonies were lowconvex to convex, entire, smooth, glossy, bu-tyrous, and semitranslucent to semiopaque.Yellowish pigment was observed with somestrains.

Biochemical tests were carried out to determinewhether reactions, other than the formation of

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acid from lactose, could be found that would dis-tinguish the lactose-utilizing strains from N.meningitidis strains and from the other species ofNeisseria.

Glucose, mannitol, lactose, sucrose, maltose,and levulose in CTA Medium are the substratesroutinely used in this laboratory for identifyingpossible Neisseria species. N. kactamicus pro-duced acid from glucose, maltose, and lactose,whereas the N. meningitidis produced acid onlyfrom glucose and maltose. As has been reported(8, 11; H. A. Fox and M. S. Goodson, Bacteriol.Proc., p. 89, 1967), an occasional strain of N.meningitidis failed to produce acid from eitherglucose or maltose. No acid was produced byeither species in 26 other substrates tested. ThepH range and NaCl tolerance studies did not re-veal a consistent difference between the strains ofN. lactamicus and N. meningitidis. With both ofthese species, no growth was observed on Mac-Conkey Agar or Simmons Citrate Agar. Nitratewas not reduced to nitrite, indol was not pro-duced, and corn oil was not hydrolized. Yellowishpigmentation on Loeffler Medium was observedwith some of the lactose-utilizing strains, butsome strains of N. meningitidis, including someneotype strains, were also yellowish.At 37 C, 10 lactose-utilizing strains which had

been transferred only 2 to 3 times following iso-lation grew on NA, but at 25 C only 2 of 10 grew.Of an additional 103 strains of N. lactamicus

(transferred an undetermined number of times),18.4% grew on NA at both 25 and 37 C, 59.2%grew at 37 C only, and 22.3% failed to grow onNA at either temperature. We have observed nostrains of N. meningitidis which grow at 25 C onNA, and only an occasional strain has grown at37 C on this medium.

Thirty N. lactamicus strains were tested for f3-D-galactosidase activity, and all gave positiveONPG reactions within 10 min. The neotypestrains of N. meningitidis groups A, B, C, D, X,Y, and Z, N. subflava (ATCC No. 19243) grownon lactose-containing medium, and several otherN. meningitidis cultures gave negative ONPG re-sults at 48 hr.OF studies were conducted with 10 N. menin-

gitidis strains, including the 7 neotype strains,and 9 N. lactamicus strains. When King OF Me-dium was used, N. lactamicus strains were definitefermenters of glucose, lactose, and maltose (acidwas produced in both the open and overlayeredtube); however, when CTA medium was used,acid was produced in glucose, lactose, and mal-tose in open tubes, but only slightly acid or neu-tral reactions were seen in the overlayered tubes.In contrast, the OF studies with N. meningitidisstrains showed less growth and, therefore, less

reaction in King OF Medium. The results ob-tained with these strains, with the exception ofgroups B and Z neotype strains, indicated anoxidative, with a questionable fermentative, reac-tion with CTA Medium. Groups B and Z neotypestrains gave a definite fermentative reaction withmaltose in CTA Medium. With Difco OF BasalMedium, we observed no growth to very slightlyquestionable reactions with both species.Oxygen requirements determined with shake

tubes indicated that N. lactamicus, N. menin-gitidis, and N. subflava are aerobic to microaero-philic organisms.No definite capsules were observed with N.

lactamicus, and no Quellung reaction was ob-tained with the homologous or heterologousantisera.Three lactose-utilizing strains and two strains of

N. meningitidis were tested for drug susceptibilityto 27 chemotherapeutic agents by use of com-mercial discs. Results were similar in that both theN. lactamicus and the N. meningitidis strains weresensitive and resistant to the same antibiotics.N. meningitidis and N. lactanicus strains werefurther studied with sulfadiazine and penicillinwith a plate dilution method. All of the lactose-utilizing strains were sensitive to 0.1 jg of penicil-lin per ml as were the N. meningitidis strains. Only4 (5.4%) of 74 strains of N. lactamicus were re-sistant to 1 mg of sulfadiazine per 100 ml, whereasa much greater percentage of N. meningitidisstrains have been reported to be resistant to sul-fadiazine (5).

Since many of the N. lactamicus strains re-ceived recently were isolated from TM plates, wedecided to determine whether strains which hadbeen isolated before the introduction of TMwould also grow on this medium. All grew well onTM using either VCN or polymyxin B with risto-cetin. Viability counts, with MH Agar and theantibiotics suggested by Thayer and Martin,showed that N. lactamicus strains grew equally aswell as those of N. meningitidis. Approximatelyone-half of the organisms of both the N. lacta-micus and N. meningitidis strains were inhibited.A N. subflava strain was streaked on TM, and

except for a few colonies in the primary area ofgreatest inoculum, it failed to grow. This straingrew well on NA at both 25 and 37 C and wasyellow on Loeffler Medium.The serology of the lactose-utilizing strains

was studied with antisera prepared from threestrains (A2894, A5906, and A7515). Table 1 givestube agglutination titers obtained by use of theseantisera with N. meningitidis A, B, C, D, X, Y,and Z antigens and with the homologous N. lacta-micus strains.Serum A2894 did not agglutinate any of the

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TABLE 1. Tube agglutination titers with N.lactamicus antisera and N. meningitidis

and N. lactamicus strains

N. lactamicus antiserumstrain no.

Antigens

A2894 A5906 A7515

N. meningitidis sero-group

All ................. _b

B .................._.......... . ..

D..20C d

Z. _d d

Homologous N. lac-tamicus strain........ 1:1,280 1:80 1:320

a Branham and Slaterus neotype strains used.bNo agglutination at serum dilutions of 1:20

or greater.o The reciprocal of the dilution.d Minimal reaction (<3+) at 1:20.

neotype strains of the various serogroups of N.meningitidis. Serum A5906 produced completeagglutination of the group D antigen and partialagglutination of the group Z antigen only at the1:20 dilution. Partial agglutination also occurredat the 1:20 dilution when the group D and Z anti-gens were tested in serum A7515.When the three N. lactamicus strains were

tested with antisera to the same N. meningitidisstrains in the tube agglutination, there was noagglutination at the 1:20 dilution of serum or atgreater dilutions.The N. lactamicus antisera were absorbed with

the homologous strains of N. lactamicus and withgroups A, B, C, D, X, Y, and Z strains of N.meningitidis. Table 2 shows the results of the tubeagglutination test with these sera following ab-sorption and testing with their homologous anti-gens.

Absorptions of the three antisera with N. menin-gitidis groups A, B, C, D, X, Y, and Z strainsshowed no reduction in titers. The detectableagglutinins of A2894, A5906, and A7515 anti-sera were removed or greatly reduced when theseantisera were absorbed by the homologous N.lactamicus strains.When the antisera to N. meningitidis groups A,

B, C, D, X, Y, and Z were absorbed with thethree N. lactamicus strains, the homologous titersof the A, B, C, D, X, Y, and Z antisera remainedunchanged by the absorptions.There were 116 strains of N. lactamicus avail-

able for testing by slide agglutination in the anti-sera for the 7 serogroups of N. meningitidis andthe 3 N. lactamicus antisera. Only 34 of thesestrains were smooth and, therefore, suitable forexamination. These strains were tested withgroups A, B, C, D, X, Y, and Z N. meningitidisantisera and with the three N. lactamicus anti-sera (Table 3).The N. lactamicus strains were not agglutinated

by the N. meningitidis groups A, B, C, D, X, Y.and Z antisera, except for three strains which re-acted as follows: two strains agglutinated withgroups C and X and with two N. lactamicus anti-sera, and one strain reacted with group Y andwith all three N. lactamicus antisera. The remain-ing 31 strains agglutinated specifically with N. lac-tamicus antisera. Approximately 100 N. meningi-tidis strains have been tested by slide agglutina-tion with A2894, A5906, and A7515 N. lactamicusantisera and none agglutinated. In addition, onelactose-utilizing strain, No. SD9, studied byMitchell et al. (10), was available for serologicalstudy. This strain agglutinated with A5906 anti-serum, but not with the N. meningitidis antisera.Of 116 N. lactamicus strains, 70.7% were

autoagglutinable when received for testing in thislaboratory. We attempted to determine whetherthis rough reaction might be due to repeatedtransferring of the cultures before testing. Slideagglutination tests were performed on 11 cul-tures which had been transferred only once fol-lowing isolation. Eight of these 11 strains autoag-glutinated

TABLE 2. Tube agglutination titers oflactamicus antisera with the homologous

antigens following absorptions

Serogroup used forabsorption

N. meningitidisAa

. ...

B.................C.................D................x.................Y.................z.................

Homologous N. lac-tamicus strain.....

Homologous titerunabsorbed ......

N.

N. lactamicus antiserum strain no.

A2894

2, 560b2,5601,2802,5602,5602,5602,560

<20

1,280

A5906

80808080808080

<20

80

A7515

640640640640640640640

<20

320

a Branham and Slaterus neotype strains usedfor absorptions.

b The reciprocal of the dilution.

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TABLE 3. Slide agglutination results with 116 strains ofN. lactamicus

N. meningitidis antisera group N. lactamicus antiseraNo. of strains cent

A B C D X Y Z A2894 A5906 A7515

Groupable23 19.8 -~- - - - - - + + +6 5.2 - - - - - - - - + ±1 0.9 - - - - - - - - - +1 0.9 - - - - - - - + -

Nongroupable82 70.7 ag ag ag ag ag ag ag ag ag ag2 1.7 --o+-g+-ogt-e+ +1 0.9 - - - - - + - + + +

Symbols: ag, autoagglutinable; -,agglutination did not occur; +, agglutination occurred.

TABLE 4. Number of N. lactamicus strains bygeographical origin and source

Clinical source

Geographical origin $to 0

Areas of U.S.Northeast..............3 1Middle Atlantic........ 6 2East North Central... 2 7South Atlantic......... 50 18East South Central..... 3West South Central.... 3Mountain.............. 3 3. 1Pacific................. 9 1

Canada.................. 4

Totals.................. 83 1 3 1 28

a All three of these strains were from the samepatient.

The geographical origin and the clinical sourceof the N. lactamicus strains are shown in Table 4.The strains were from eight different areas of theUnited States and Canada. Of 116 cultures, 83were reported to be from the nasopharynx, threefrom the lung (same patient), one from spinalfluid, and one from amniotic fluid.A summary of some of the distinguishing char-

acteristics of some of the Neisseria species is givenin Table 5. The species included are N. meningiti-dis, N. lactamicus, and N. subflava.

DISCUSSIONBiochemical studies showed that N. lactamicus

strains are not identical to any of the other Neis-

TABLE 5. Distinguishing characteristics of someNeisseria species

Neisseria species

Biochemical testslactamicus meningitidis sub-

Growth on Thayer +' + -Martin

Acid from substratesin CTAbGlucose + + +Lactose + _Maltose + + +Mannitol _ _Sucrose - -Levulose - _

Yellow pigmentation + or - -or + +on Loeffler's medium

Growth on NA25 C -or + +37 C + or- +

,B-D-Galactosidase ac- + _ -

tivity

a Symbols: +, 90%P or more positive; -, 90%0or more negative; + or -, majority of culturespositive; - or +, majority of cultures negative.

b An additional 21 substrates not used routinelyfor the identification of Neisseria were all nega-tive with these three species.

seria species. The two most distinctive reactionsof the N. lactamicus strains are fermentation oflactose and production of f3-D-galactosidase(ONPG reaction). According to Bergey's Manual,none of the Neisseria species use lactose. The twospecies of Neisseria which appear to be most simi-lar to N. lactamicus biochemically are N. meningi-

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tidis and N. subflava. All three of these speciesuse glucose and maltose and fail to form acidfrom 29 other substrates in CTA Medium.

Studies employing King OF Medium indicatethat N. lactamicus is a fermentative organism. Afew strains of N. meningitidis appeared to fer-ment maltose in CTA Medium, but none demon-strated definite fermentation in King OF Medium.Fermentative reactions were not observed withglucose in either medium inoculated with N.meningitidis. The N. lactamicus strains did notappear to grow as well in CTA Medium as theydid in the King OF Medium.The production of acid by some of these strains

is not always evident in CTA Medium untilafter 48 hr. For this reason, the CTA Mediumtubes should be held for 1 week before the finalreadings are taken. The ONPG test can be usedfor a rapid indication of lactose-utilizing strains.As reported by Corbett and Catlin (2), it is notnecessary to grow the organisms on a lactose-containing medium before determining theONPG reaction.

Although to the experienced worker colonialdifferences between most strains of N. lactamicusand N. meningitidis may be apparent on certainmedia, we feel they should not be relied upon fordistinguishing between species.Thayer and Martin (13, 14) reported that their

medium inhibits the growth of Neisseria speciesother than N. gonorrhoeae and N. meningitidis.However, they are now aware (personal communi-cation) that lactose-utilizing strains are being iso-lated on their medium. Our results showed that allof the N. lactamicus strains grew well on both ofthe antibiotic formulas recommended by theseauthors and that a N. subflava strain grew onlyin the primary area of heavy inoculum.

In this laboratory, approximately 1,500 group-able N. meningitidis strains have not grown at 25C on NA, and only an occasional strain has grownat 37 C on NA. The N. lactamicus strains studiedvaried in their ability to grow at both 37 and 25C on NA. Therefore, as a group, N. lactamicusstrains vary from this species in this characteristic;however, individual strains cannot be reliablydifferentiated just on the basis of their ability togrow on NA.

Since N. lactamicus may or may not exhibityellow pigmentation on Loeffler Medium, thischaracteristic also cannot be used to separatethese Neisseria species.

In considering whether the lactose-utilizingNeisseria are variants of N. meningitidis, it is per-tinent to note that H. A. Fox and M. S. Goodson(Bacteriol. Proc., p. 89, 1967) were unable todemonstrate spontaneous lactose-negative vari-ants of the lactose-utilizing strains. Similarly,

lactose-utiliing variants of N. meningitidis strainswere not detected.Another factor we considered in attempting to

determine the proper taxonomical speciation ofthese organisms was their serology. Results of ag-glutination, both slide and tube, showed a dis-tinguishable difference between three antiseraprepared from N. lactamicus strains and antiserato N. meningitidis serogroups A, B, C, D, X, Y.and Z. Cross absorptions showed that these N.lactamicus strains were not identical with the N.meningitidis strains.Only one strain of N. lactamicus which was

studied by Mitchell et al. (10) was available forexamination. This strain was reported to havebeen agglutinated by group B antiserum uponprimary isolation and, subsequently, to havebecome nonreactive in A, B, C, or D groupingsera. When reexamined in this study, it failed toagglutinate in the N. meningitidis grouping sera,but was agglutinated by N. lactamicus antiserumA5906.

It should be noted that none of the 34 smoothstrains of N. lactamicus in the present study, in-cluding three strains examined at the time ofprimary isolation, were agglutinated by N. menin-gitidis group B antiserum. Of the 34 smoothstrains, 31 were agglutinated specifically by one ormore of the N. lactamicus antisera. Three strainsgave cross reactions: two strains were aggluti-nated by both group C and X antisera and one bygroup Y antiserum. These three strains were alsoagglutinated by at least two of the three N. lac-tamicus antisera. This is in contrast to the findingsof Mitchell et al. (10), who reported that six ofeight lactose-utilizing strains were serologicallyindistinguishable from N. meningitidis group B.At present, no explanation for this difference inresults is evident. Mitchell and co-workers alsofound that after several laboratory subcultures,often as few as three passages, the lactose-utilizingstrains were no longer agglutinated by group Bantiserum, and they noted that this loss of agglu-tinability had not been observed with nonlactose-fermenting strains of group B N. meningitidis.We also made this latter observation.Of 116 N. lactamicus strains, 70.7% autoag-

glutinated. Although some strains of N. meningi-tidis are autoagglutinable, the percentage is ap-preciably below 70.7 %, even when strains isolatedfrom throat and nasopharynx only are included(4, 5).

Neisseria cultures which have been isolatedfrom either blood or spinal fluid are submitted toNCDC by laboratories in all sections of theUnited States. Of approximately 1,200 strainsstudied over a 15-year period, a lactose-ferment-ing organism has been implicated in only one case

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NEISSERIA LACI

of meningitis. We feel that further study of theN. lactamicus strains is needed. The carrier rateshould be determined, and data should be col-lected on any possible clinical manifestations con-

nected with the isolation of this organism. Wefeel that these organisms should not just be"lumped" with N. meningitidis and that theirclinical significance should be adequately de-termined.

Because the clinical significance of N. lactami-cus appears to be different from that of N. menin-gitidis and since these organisms appear to be bio-chemically and serologically distinct from otherNeisseria species, we feel that the designation ofthese organisms as a new species is warranted.The selection of the specific epithet lactamicus isderived from the Lating words lactis meaning milkand amicus meaning friend or friendly.

Representative strains of N. lactamicus were

deposited with the American Type Culture Col-lection (ATCC) and National Collection ofType Cultures (NCTC). They were assignedATCC and NCTC numbers as follows: N. lac-

tamicus, NCDC A2894-ATCC 23972-NCTC10616; N. lactamicus, NCDC A7515-ATCC23970-NCTC 10617; and N. lactamicus, NCDCA5906-ATCC 23971-NCTC 10618. StrainA7515 is designated as the type strain.

ACKNOWLEDGMENTS

We thank William H. Ewing, Enteric Bacteriology Unit,NCDC, for his guidance in the selection of a species name. Wealso thank Dwane L. Rhoden, Bacterial Reference Unit,NCDC, for providing primary subcultures of 11 strains of N.iactamtkw.

'AMICUS SP. N. 77

LIERATURE CITED

1. Branham, S. E. 1958. Reference strains for the serologic groupsof meningococcus. Intern. Bull. Bacteriol. Nomen. Taxon.8:1-15.

2. Corbett, W. P., and B. W. Catlin. 1968. Galactosidase activityof lactose-positive Neisseria. J. Bacteriol. 95:52-57.

3. Davis, B R., andW. H. Ewing. 1964. Lipolytic, pectolytic, andaliginolytic activities of Enterobacteriaceae. J. Bacteriol.88:16-19.

4. Hollis, D. G., G. L. Wiggins, and J. H. Schubert. 1968. Sero-logical studies of ungroupable Neisseria meningitidis. J.Bacteriol. 95:1-4.

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VOL. 17, 1969

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