CopyrightC 1976 AmericanSociety for Microbiology Printed inU-SA.
Halophilic Vibrio Species Isolated from Blood
Cultures
D. G. HOLLIS,* R. E. WEAVER, C. N. BAKER,ANDC. THORNSBERRY
Centerfor Disease Control, Atlanta, Georgia 30333
Received forpublication8 December 1975
The Special Bacteriology Section of the Center for Disease Control has
re-cieved38 culturesofahalophilicbacterium which isapparently unnamed. On the basisof theminimalcharacteristics of Vibriospecies proposed byHugh and Sakazaki,this bacteriumbelongstothegenusVibrio.The unnamedspeciescan
bedifferentiated from Vibrioparahaemolyticusbyalowertolerance forsodium chloride (NaCl)and thefermentation of lactose. The failure to fermentsucroseis anadditional characteristic which differentiates these organismsfrom V. algi-nolyticus. Of33unnamedspecies strains tested, allweresensitive topenicillin, ampicillin, carbenicillin, cephalothin, chloramphenicol, gentamicin, tetracy-cline, rifampin, nitrofurantoin, and sulfisoxazole by agar diffusion and agar
dilution tests. The sources of isolation of the cultures of the unnamed species
suggestthatit isaclinically important organism. Twentystrainswereisolated
from blood cultures. Two of these were isolated from spinal fluid also. The remaining cultureswereisolated from localizedinfections of the extremities. In
contrast, only 2 of 60 cultures of V. parahaemolyticus and V. alginolyticus
receivedinourlaboratoryashumanisolates from extra-intestinal sources were isolated from blood.
In 1950 Vibrioparahaemolyticus, ahalophilic organism, was demonstrated to be a major causeoffoodbornegastroenteritis inJapan (9). Therehave been several subsequent reports of the isolationof V.parahaemolyticus from var-ious marine sources (1, 8, 14, 20, 24). Asecond halophilic organism frequently found in the marine environment but not in association withgastroenteritisisV. alginolyticus(18, 26). The first documented outbreak of gastroen-teritis inthe UnitedStates due to V. parahae-molyticus was in 1971 (4). Prior to 1971 strains of V.
parahaemolyticus
and V. alginolyticus isolated inthe United States from tissue infec-tionshadbeenreferredto ourlaboratory. Some of these strains were studied by Twedt et al. (23).During the last 11 years we have also re-ceived38halophilic cultures, isolated from hu-mans inthe United States, which were similar but not identical to V. parahaemolyticus and V.alginolyticus. The ability of these cultures to ferment lactose isonecharacteristic that distin-guishesthem from V.parahaemolyticusand V. alginolyticus, and they will be referred to as thelactose-positive (L+)Vibrio in the remain-der of this report.
The source of isolation of 20 to 38 cultures was reported to be blood, which indicates that the recognition of these organisms by clinical microbiologists is important. The purpose of
our report isto describethe L+ Vibrio andto
indicate how it can be differentiated from V. parahaemolyticus andV. alginolyticus.
MATERIALS AND METHODS
Strains. Thirty-eight strainsofL+Vibriospecies
weresubmitted totheSpecial Bacteriology Section
ofthe Center for Disease Control for identification
from 15 states in the United States. Twenty-four
strains of V.parahaemolyticus and 24 strains of V.
alginolyticus were also examined. These included
thefollowing cultures, which also have been studied
in other laboratories: V.parahaemolyticus KC821,
KC824, KC833, and KC830 (2); A1889, A5704, and
A6202 (26); and A1334 and A8633 (3, 25); and V.
alginolyticus B3471, B3481, B3591, B9083, B4185,
B984, B3744, B6512, B835, B6550, B1650, B4364,
B9003, A1539, and B3660 (2, 3); A3637, A4871, and
A5002 (25); and A3454 andA6670 (3,25).
Mediaandmethods. Most of the media
prepara-tion and the procedures used in determining the
biochemical characteristics have been previously
described (6, 11). Tubes containing methyl
red-Voges-Proskauermedium (2 ml) and Moeller
decar-boxylase medium (3 ml) were each supplemented
with 0.1 ml of a 20% NaCl solution. None ofthe
other media was supplemented with additional
NaCl.
Thetestfor 3-D-galactosidase activity on
o-nitro-phenyl-,8-D-galactopyranoside (ONPG) was
per-formed byaddingoneONPGtablet (Key Scientific
Co.) to 1 ml of distilled water, inoculating with a heavy suspension of growth from an overnight triple 425
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sugariron agar slantor heart infusionagar slant,
and incubatingin a waterbathat37C. A positive
resultwasindicated by the development ofayellow
color within 6 to 24 h. Negut and Hermann's (16) modification of themethod of Giammanco and Falci
was also used for the ONPG test. NaCl tolerance
wasdetermined byusingnutrientbroth (Difco) with varyingpercentages(6to12%)of NaCl. Themethod ofKobayashietal. (12)wasused to testforgrowth
onthiosulfate-citrate-bile salt-sucroseagar (TCBS).
Leifson's method (13)was used todemonstrate fla-gella morphology.
Antimicrobial susceptibility. Susceptibilityto 13 antimicrobial agents wasdetermined byagar dilu-tionandagardiffusionmethods (5, 15).
For the agardiffusiontests, the organismswere
grown inTrypticase soybroth (BBL) tocontain
ap-proximately 10" colony-forming units/ml, asjudged
by comparison with the 0.5 McFarland standard (15).Ifnecessary,theculture wasdiluted with ster-ile Trypticase soybroth. The cultureswereapplied
toMueller-Hinton (BBL)agarplates for
susceptibil-ity testing as described previously (15). No
addi-tional NaCl wasaddedto either of these media.In theagar dilutiontests, theinoculum wasprepared inTrypticase soybrothtoaturbidityequivalentto that of the0.5McFarland standard (approximately 101colony-forming units/ml) and then diluted 1:10 in Trypticasesoybrothtoaconcentration of 107
colony-forming units/ml. The inocula were added to the
surface ofMueller-Hinton agarplateswithaSteers
replicating device (19). By this method, approxi-mately 104 colony-forming units of each culturewas
deposited on each plate. No additional NaCl was
added to these media either. Not all strains were
tested by agardilution.
The13antimicrobialagentsusedinthestudyare shown inTable5. Thesourcesof theseagentswere:
ampicillin, Wyeth Laboratories, Westchester, Pa.; carbenicillin, penicillin, and tetracycline, Pfizer, Inc., New York, N.Y.; cephalothin, Eli Lilly, Indi-anapolis, Ind.; chloramphenicol, Parke-Davis Co., Detroit, Mich; clindamycin and erythromycin, Up-john Co., Kalamazoo, Mich.; colistin, Warner-Lam-bertLaboratories, Morris Plains, N.J.;gentamicin, Schering Corp., Bloomfield, N.J.;kanamycin, Bris-tol Laboratories, Syracuse, N.Y.; nitrofurantoin, NorwichPharmacal Co., Norwich, N.Y.; rifampin, CibaPharmaceutical Co., Summit, N.J.; and sulfi-soxazole, Hoffman-LaRoche, Inc., Nutley, N.J.
RESULTS
When received in our laboratory, all of the
L+ Vibrio, V.parahaemolyticus, and V. algi-nolyticus cultures grew readily on heart
infu-sion agar to which no extra NaCl was added.
Heart infusion agar and many media
com-monlyusedinclinical laboratories contain 0.5% or more NaCl.
At 18to24h,thecolonies of the L+ Vibrioon
heart infusionagarcontaining5% rabbit blood
were approximately 2 to 4 mm in diameter.
There was usually a narrow clear zone of
he-molysisaround individual colonies anda green-ish or lavender-greenish discoloration of the blood cells inthe areaofconfluent growth.
Several cultures weretested fortheir ability to grow on TCBS (Difco) agar. The colonies wereblueorbluishgreen.Thesecolonieswere difficulttodistinguishfromcolonies ofV. para-haemolyticus. One strain fermented sucrose andproduced bluish-green colonies after over-night incubation; however, after4days of
incu-bation, yellow areas developedwithin most of thecolonies, andanoccasional colony showeda yellow center.
The L+ Vibrio organisms were
gram-nega-tive rods which exhibited pleomorphism.
Coc-coid to long, comma-shaped to straight, and
swollen rods were observed. Flagella strains
were made from 18- to 24-h, 25 C broth
cul-tures with 24 strains, and all showed single polar and occasional subpolar flagellation.
Characteristics commontotheL+ Vibrio, V. parahaemolyticus, and V. alginolyticus are
listed inTable1. Inusing the Moeller base for
decarboxylase and dihydrolase tests, we have
found theresultstobemoreconsistent if0.1ml
ofa20%NaCl solutionisaddedtoeach tubeof 3 mlof medium.
Acompilation of thebiochemical characteris-tics determined for the 38 strains of the L+
Vibrio is given in Table 2. Lactose was fer-mented, usually within 24 h, but in a few
in-stances the acid reaction was weak or not
de-tected until 3 to 7 days. With one culture the
medium didnotbecome acid. The ONPG
reac-tionwaspositiveforall 20strains ofL+ Vibrio tested, whereasitwasnegativefor 10strainsof
V. parahaemolyticus and 6 strains ofV. algi-nolyticus tested. The ONPG reaction did not
depend upon growth of the organism on a lac-tose-containing medium. The one culture whichdidnotfermentlactosewasONPG
nega-tive when the ONPG tablets were used;
how-ever, it was ONPG positive when the ONPG mediumwasused. Acidwasproducedfrom
sali-cin and cellobiose by all 38 strains. None of the
TABLE 1. Common biochemicalcharacteristicsof
L+ Vibrio, V.parahaemolyticus, and V.
alginolyticus
Test Result"
Fermentationofglucose ... ... +
Oxidase ... +
Lysinedecarboxylase ... ... +
Argininedihydrolase .
Ornithinedecarboxylase ... ... + or(+) *1 +,90%ormorepositivein 1 or 2days; -,90%or
morenegative; + or(+), majority ofcultures
posi-tive,somedelayed.
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VOL. 3, 1976
TABLE 2. Biochemical characteristics of L+ Vibrio
species Testorsubstratea
Oxidase Fermentation Growthon
MacConkeyagar SSagar Nitrate reduction Citrate(Simmons) Alk Urease(Christensen's agar) Gelatin(7days)
Moeller's decarboxylase medium Lysine
Arginine
Ornithine Indole ONPG
Voges-Proskauer
Nutrient broth without NaCl Nutrient broth with6%NaCl Nutrient broth with8%NaCl Motility
Acid from Glucose Mannitol Lactose Sucrose Maltose Glycerol Salicin Galactose Levulose Mannose Trehalose Cellobiose Melibiose Dextrin Glycogen Starch
Signb
+ or+
+ or
+ or
+or(+)
-or
+ +
+
%Positivec
100 100
100 39 (8) 100 76 (11)
0
97
97(3)
0
66(26) 97(3) 100
0 0
100 8 97
100 66 81(16) 3 100 0 (47) 100 100 100 100 100 100 26(53) 97 100 100
aAcidnotproduced byanyof the strains studied:xylose,
arabinose, adonitol, dulcitol, rhamnose, sorbitol, inositol, inulin, erythritol, melezitose, and raffinose.
bSign: +, 90% or morepositive in 1 or2 days; -, no reaction (90%ormore); + or -moststainspositive, some
negative;-or+,moststrainsnegative,somepositive;+ or
(+), mostreactions occur within 1 or 2 days, some are delayed; - or (+), most strains negative, some positive
delayed; d, different biochemicalreactions[+,(+), -].
cFigures indicate percent positive in 2days;those in
parentheses indicate percent positive delayed 3 or more days. Resultsarebasedonthestudy of38strains,withone exception. The ONPG reaction was determined with 20 strains.
L+ Vibriostrainsgrewinnutrient broth
with-out NaCl, and all 38 culturesgrewinnutrient
broth with 6% NaCl. The upper limit of the
NaCl tolerance of these organisms is usually
below 8% NaCl.
In Table3the key reactions for differentiat-ing the L+ Vibrio species, V. parahaemolyti-cus, and V. alginolyticus are presented.
Lac-tose fermentation and ONPG reactions have
beenfoundpositive onlyfor thelactose-positive
species. Sucrose is fermented by V. alginolyti-cus but only rarely by the other two species.
HALOPHILIC VIBRIO SPECIES 427
Salicin has been fermented rapidly by all strains of the L+ Vibrio species. Strains of V. parahaemolyticus or V. alginolyticus that pro-duced acid from salicin usuallyrequired3 to 14
days. Mannitol is usually fermented by all threespecies, but 13of38strainsofL+ Vibrio species did not ferment it. The Voges-Pros-kauer reaction is only positive for V. alginolyti-cus (NaCl must be added to the Voges-Pros-kauer medium or the orgnanisms will not grow). The NaCl tolerance of the L+ Vibrio is usuallybelow8%. V.parahaemolyticus usually grows at 8% but not at 10%, and V. alginolyti-cus usually grows at10% or higher concentra-tions.
The minimal characteristics necessary for the identification of the L+ Vibrio species are recorded in Table 4.
The agardiffusion and agardilution suscep-tibility results are shown in Table 5. On the basis of minimal inhibitory concentrations (MICs), all the strains in allthreegroups were
susceptible to cephalothin, chloramphenicol, gentamicin, tetracycline, rifampin, nitrofuran-toin, and sulfisoxazole. Most strains were also susceptibleto kanamycin, but three strains of the L+ Vibrio group had MICs of32
pAg/ml.
Allof the L+Vibrio strains werealso suscep-tibletoampicillin, carbenicillin, andpenicillin. Penicillin MICs of 1 to 2
/ig/ml
may also be considered intermediate, but these levels are easily achieved in the serum. All L+ Vibrio strains were resistantto colistin. The V. algi-nolyticus strains wereallresistant to the peni-cillins, as were all butone of thestrainsofV. parahaemolyticus; both species varied in their susceptibilitytocolistin.TheL+Vibrio strainsvariedintheir suscep-tibility to clindamycin and erythromycin, whereas the V. alginolyticus and V. parahae-molyticus strainsvaried intheirsusceptibility
to erythromycin and colistin. Nine of the L+ Vibriostrainshaderythromycin MICs of 1 or 2
,tg/ml
(sensitive), 12 had MICs of4jig/ml
(in-termediate), and two had MICs of8/Ag/ml
(re-sistant), but all the zone sizes (22 to 30 mm) indicated susceptibility (21). Twenty of the V. alginolyticus strains were resistant to erythro-mycinby MICs (8 or 16 ,ug/ml) and one strain wasintermediate (4 ,ug/ml), but all zone sizes(21 to 23 mm) again indicated susceptibility.
The largest number of discrepancies between MICs andzonesizeswasobtained with V. para-haemolyticus strains and clindamycin, erythro-mycin, and colistin. The clindamycin MICs (8
to 32 ,tg/ml) indicated resistance, but many of the zone sizes wereinthe intermediate or sus-ceptible range. With erythromycin, all were
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TABLE 3. Differentiation ofL + Vibrio species, V.parahaemolyticus, andV.alginolyticus L+Vibrio V.parahaemolyticus V.alginolyticus Testorsubstrate
Signa No. +b/no. tested Sign No. +/no. tested Sign No. +/no. tested
Lactose + 37/38 - 0/24 - 0/24
ONPG + 38/38 - 0/11 - 0/6
Sucrose - 1/38 - 1/24 + 24/24
Salicin + 38/38 -or(+) 0(4)/24 d 3(10)/24
Mannitol + or - 25/38 + 24/24 + 24/24
Voges-Proskauer - 0/38 - 0/24 + 24/24
NaCltolerance
<8% + 36/38 + 24/24 + 24/24
28% <10% - 2/38 + 24/24 + 24/24
.10% - 0/38 - 0/24 + 24/24
aSign:+, 90% or morepositivein 1or2days;-, no reaction(90%ormore);+or-,moststrainspositive,somenegative; -or(+), most strainsnegative,somepositivedelayed; d,different biochemical reactions [+,(±), -].
bReactionspositive within48h;parentheses indicate reactionsdelayed3to14days.
TABLE 4. Minimal charac
identification ofL + Vibi
Characteristic Gram-negative, asporogenous
rod Oxidase
Triplesugarironagarbutt,acid Glucose, gas
Lactose, acid ONPG Sucrose,acid Acetylmethylcarbinol
Hydrogen sulfide, blackbutt in
triplesugarironagar L-Lysine decarboxylase L-Arginine dihydrolase L-Ornithinedecarboxylase Growth in nutrient broth
with-outNaCl
Growth in nutrient broth with
6%NaCl
Growth in nutrient broth with 8% NaCl
aBasedon astudyof 38 strains'
ONPG reactionwasdetermined wi
b+,90%or morepositive in 1o: (90%ormore);+or(+),mostreacd
days,somedelayed.
cReactions positive within 48 ] reactionsdelayed 3 to14days.
either 8 or 16 ,g/ml (resi;
whichwas4,ug/ml (interme
sizes indicatedsusceptibility
24 strains were susceptible intermediate and 14 were r
the 24 strainswere susceptit
(3were intermediate and 1
Of the 38 cultures ofL+
wereisolated fromblood, an
the organism was also iso
fluid.This is incontrast to t
tion of the other halophilic
received; 1 of 42 strains of V.
humanswasisolated from bli
V.parahaemolyticus culture
cteristicsfor the tinal sources was isolated from blood. The other rio sp. strainsa sources were:
leg, nine;
hand,
three;
and one Signb Positive(%)c each from wound (site not given), throat,cor-+ 100 nea, wrist, and thumb. The source of one
cul-ture was notknown.
+ 100 Histories were obtained on seven patients
+ 100 from whom L+ Vibrio cultures were isolated +or(+
10
fromblood. Four hadleg
lesions,
one of which+ or() 81 (16)
+ 100 was culture positivefor L+ Vibrio, andafifth
- 3 had skin lesions at an unspecified site.
- 0 The clinical information we have received concerningthepatientsfromwhom theL+
Vi-+ 97(3) brio strains were isolated has been sketchy.
- 0 However, the information we have does
indi-+ or (indi-+) 66(26) cate that this organism causes systemic
infec-tions, which maybefatal within 2 or 3daysof
+ 100 theonsetof symptoms. Summaries of the
histo-ries of five persons from whom blood isolates
- 8 were obtained are as follows. The first was a patient, age 83, who died within 12 h after th oneexception.The comingtotheemergencyroom. Cellulitis of the
1r
2days; -,noreaction leg wasnoted. The second case was a45-year-tions occur within 1 or 2 old male who entered the hospital with skin
lesions and diedsuddenly. The third case was a
h;
parentheses indicate 69-year-oldmale, who had ulcers on one leg. Hedied 4h after admission. The fourth case was
anadultmale whodeveloped lesionsonhis legs stant) except one, while on a fishing trip and died within 48 h. A diate), but all zone leg lesion also contained the L+ Vibrio orga-Withcolistin,7of nism. The fifth case was an elderly man. The by MICs (3 were organism was cultured from both blood and esistant), but 20 of spinal fluid 4 h before death. He was found
bleby the disktest unconscious in his room 12 h before death. He
was resistant). had been seen the previous day and did not Vibrio species, 20 seem to be ill.
idin two instances Of the patients whose sex was known, the
)lated from spinal majority were male (28 of 29 cultures).
;he sourcesof isola- Seven cultures of the L+ Vibrio organisms
Vibrio species we were referred to our laboratory from Louisiana, alginolyticus from six from Florida, five from Alabama, four from ood andonly1of18 Texas, four from Rhode Island, two from
Ha-?sfrom extra-intes- waii, two from Virginia, and one each from
428 HOLLIS ET AL. J. CLIN. MICROBIOL.
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E-HALOPHILIC VIBRIO SPECIES 429
North Carolina, Arkansas, Georgia, Califor-nia, South Carolina, Wisconsin, Maryland, and Pennsylvania. All but three cultures were from coastal states.
DISCUSSION
Biochemical studies show that the L+ Vibrio cultures are not identical to V.
parahaemolyti-cus or V.alginolyticus. However, on the basis oftheminimal characteristics of Vibriospecies proposed byHugh and Sakazaki (10), this bac-terium belongs to the genus Vibrio. The two mostdistinctive reactions of this unnamed spe-cies arefermentation of lactose and production of B-i-galactosidase. These organisms can be further differentiated from V. parahaemolyti-cusby alower NaCltolerance.Additional char-acteristics thatdistinguish thesebacteria from V. alginolyticus are failure to ferment sucrose and lack ofacetylmethylcarbinol production.
The antimicrobial susceptibility studies of the L+ Vibrio, V. parahaemolyticus, and V. alginolyticus also suggest that this unnamed species is distinct from V. parahaemolyticus and V.alginolyticus. All of the L+ Vibrio cul-tures tested were sensitive to penicillin,
car-benicillin, and ampicillin and resistant to colis-tin; all of the V. alginolyticus strains and all but one of the V. parahaemolyticus strains were resistant to penicillin, carbenicillin, and ampicillin.
The standardized disk diffusion technique v (15) canbe used withthese Vibrio species and C withall the antimicrobial agents tested except Cu erythromycin, clindamycin, and colistin.
Be-X causeof the largenumber ofdiscrepancies
be-= tween MICs andzonesizesfor thelatterthree
O antibiotics, susceptibilities tothese antibiotics c should be
performed by
a dilution method. It S remainstobeseen iftheinvitro susceptibilityX results are useful clinically.
: Studies ofsome other workers further indi-r catethat theselactose-positive halophilic orga-nisms are a separate species. Baumann et al. studiedsomeofourL+ Vibrio strains and des-ignated them group C-2 (3). Results of their X studies indicate that V.
parahaemolyticus,
V. -: alginolyticus, and the L+ Vibrio are distinct Q from each other. Two of our lactose-positive < cultures were studied by Zen-yoji et al. (25). They found them to be neither V. parahaemoly-ticus nor V.alginolyticus and included them in E other species of Vibrio. Also, Morris Fishbein : studiedtwoofourL+Vibrioorganisms,and he.>
reported
that neitherorganism
was aV.para-u
haemolyticus
strainbiochemically,
that bothfailed toreact inany of theV.
parahaemolyti-cus 0 and K antisera, and that the salt
toler-3, 1976
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430
ance and cellobiose fermentation reactions were nottypical ofV.parahaemolyticus (per-sonalcommunication).
When the firstfew strains of the L+ Vibrio werereceived in our laboratory, it wasthought that they were a variantofV. parahaemolyti-cus,and wereported their identityaccordingly. Ourfailure at first to appreciate thedistinction between the lactose-positive halophilic orga-nisms and V. parahaemolyticus was responsi-ble for our erroneously reporting as V. para-haemolyticus theorganisms that wereisolated from patients described byRoland (17) andby Zide et al. (27).
Recently Thorsteinsson et al. (22) and Fer-nandez and Pankey (7)reported clinical mani-festations ofhalophilic Vibrio infections. Two of theisolatesintheformerreport, cases 1and 2, and two of theisolates in the latter report, cases2 and3, are L+ Vibrio cultures included inthis study.
Theclinicalsources andavailablehistoriesof the L+ Vibrio suggest that it is a medically important organism. Of38 cultures, 20 (53%) wereisolatedfromblood;twoofthesewerealso fromspinal fluid. At least fiveofthesepatients hadfatal fulminativesepticemias.The remain-ingcultures wereisolatedfrom localized infec-tions of the extremities. It is interesting that none of the lactose-positive halophilic orga-nismsreceivedinourlaboratoryhavebeen iso-lated from intestinal sources. Incontrast,
only
2 (3%) of60 cultures of V.
parahaemolyticus
andV.
alginolyticus
received inourlaboratory ashumanisolates fromextra-intestinalsourceswereisolatedfromblood. The L+ Vibriogroup ofhalophilicvibriosappearstobemorelikelyto
produce serious localized or systemic illnesses than are V.parahaemolyticus andV.
alginoly-ticus.
Studies ofthe lactose-positive halophilic vi-brios have shown characteristics that distin-guishthem from strains of V.
parahaemolyti-cus causing gastroenteritisand from strains of V. alginolyticus. Theoverall characteristics of the lactose-positive microorganisms indicate that they shouldberegarded asaspecific sub-species of V.
parahaemolyticus
orpossibly
as adistinct species. Further studies ofgenetic
re-latedness may be needed to resolve this ques-tion. The sources of isolation and the clinical historiesavailable indicate that this isan orga-nismhaving thepotentialfor
producing
serious systemic infections.ACKNOWLEDGMENT
Wewishtoacknowledgethe assistanceofJeanJordan, FrancesSottnek, SusanBickham, RuthFranklin, Harvey Tatum, and PerryRiley.
ADDENDUM
Two strains of the L + Vibrio species were
deposited with the American Type Culture
Collec-tion (ATCC). They were assigned ATCC numbers
as follows: CDC A1402 = ATCC 29306; CDC
A8694 =ATCC 29307.
LITERATURE CITED
1. Baross, J., and J. Liston. 1968. Isolation of Vibrio para-haemolyticus from northwest Pacific. Nature (Lon-don)217:1263-1264.
2. Baumann, P.,L.Baumann,and M.Mandel. 1971. Tax-onomy of marine bacteria: the genus Beneckea. J. Bacteriol. 107:268-294.
3. Baumann, P., L. Baumann, andJ. L. Reichelt.1973. Taxonomy of marinebacteria: Beneckea parahaemo-lytica and Beneckea alginolytica. J. Bacteriol. 113:1144-1155.
4. Dadisman,T. A., Jr.,R.Nelson,J. R.Molenda,and H. J. Garber. 1973. Vibrioparahaemolyticus gastroen-teritis in Maryland. I. Clinical and epidemiologic aspects.Am. J. Epidemiol. 96:414-426.
5. Ericsson, H. M., and J. C. Sherris. 1971. Antibiotic sensitivity testing-reportof aninternational collab-orativestudy. Acta Pathol. Microbiol. Scand.Sect. B 217(Suppl.):1-90.
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