Studies on the meningococcus and meningococcus infection

S T U D I E S ON T H E MENINGOCOCCUS AND M E N I N G O C O C C U S INFECTION NELLES SmVERT~OR~E, M.B., J. G. FITZGERALD, M.D., F.R.C.P.(C.), AND DOI~ALD T . FRASER, ~V[.B. WITH

THE TECI~NICAL ASSISTANCE OF C O L I N CAMERON TORONTO,

ONTARIO

INTRODUCTION

E R E is now an abundance of data on the various aspects of meninT Hgococcus infection in the epidemic form in adults. I t is not the purpose of this communication to review in detail the literature on this subject. Certain researches, however, are of f u n d a m e n t a l importance. The demonstration of the efficacy of antimeningococcic serum in reducing the m o r t a l i t y of meningitis was shown b y Flexner. 1 Excellent monographs on m a n y phases of meningococcus infection have been published b y N e t t e r and DebrS, 2 Gordon, 3 F i l d e s and Baker, 4 Dopter, 12 and 1V[urray} 3 D u r i n g the years of the Great W a r other i m p o r t a n t contributions were made b y FitzGerald, ~ Eastwood, ~ Griffith, 7 Scott, s Ponder, 9 Tulloch, ~~ and Glover. ~ In the postwar period additional contributions have been published. B l a c k f a n ~4 reviewed the t r e a t m e n t of meningococcus meningitis. Studies on the types of meningococci isolated in the United States have been published b y B r a n h a m and coworkers. ~ Outbreaks and epidemics have been r e p o r t e d and publications on serum t h e r a p y have appeared in recent years b y Neal, Jackson, and Appe~baum, ~ N o r t o n and Gordon, ~ Banks, ~s Walker, ~9 Shaw and T h e l a n d e r ~~ (in children), Cantacuz~ne, 21 Tillctt and Brown, 22 and Nicolau and others} 3 Observations of a similar n a t u r e d u r i n g nonepidemic periods, however, are few (Cameron, ~4 D u d l e y and Brennan, 25 and Rake~9). The following communication is a r e p o r t of clinical, epidemiologic, and bacteriologic observations made on cases of sporadic meningococeal meningitis occurring in children in and about Toronto from October, 1931, until May, 1938. CLINICAL DATA

During the seven years u n d e r review 51 cases of meningitis were studied. F r o m each of the patients Neisseria meningitidis was isolated from the spinal fluid, and the clinical picture left no doubt of the diagnosis. The patients varied in age from. 22 days to 15 years. Postmortem examinations were made in 12 of the 21 fatal cases. I n three instances there was basilar meningitis with definite evidence of meningoeoccal septicemia; that is to say, there was a hemorrhagic rash and F r o m t h e C o n n a u g h t Laboratories, U n i v e r s i t y of Toronto, t h e w a r d s a n d laboratories of the Hospital for Sick Children, Toronto, a n d t h e D e p a r t m e n t of Paediatrics, University of Toronto. 491

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THE JOURNAL OF PEDIATRICS

petechiae in various organs. F o u r of the fatal cases of the acute type showed ventricu]ar enlargement with hydrocephalus. I n the remaining five cases, there was a more chronic type of basi]ar meningitis with hydrocephalus. Clinical Course.--The patients were arbitrarily placed in one of three categories. F u l m i n a t i n g cases comprised those in which death occurred in 24 to 48 hours. A c u t e cases were the usual type seen in children during n0nepidemic periods with a history of an acute onset and a duration of three to seven days. Chronic basilar cases were characterized by a history of one to three weeks' duration, definite opisthotonos, and signs of basilar involvement (Table I ) .

Complications.--The frequency and the type of complications a r e shown in Table II. I t will be noted that the commonest was hydrocephalus, which occurred in 9 patients. This condition developed d u r i n g the final stages of the disease; that is to say, after the acute symptoms had been present from six days to three weeks. All of these were patients under 7 years of age, and all died. T r e a t m e n t . - - A l ] cases were treated with polyvalent antimeningococcal serum which was usually administered by the continuous intravenous method ~6 in doses of 20 c.c. to 150 c.c. during the first twenty-four to forty-eight hours after admission. I n addition, daily intrathecal injections of serum totalling from 70 c.c. to 460 c.c. were given. The serum was supplied by the Connaught Laboratories and was not concentrated. M o r t a l i t y . - - T h e gross mortality of the group was 42 per cent (see Table I ) . The mortality appears to depend to a great extent on the clinical type of the disease: in all those classified as " f u l m i n a t i n g " and TABLE I ~/~ENINGOCOCCIC ~ E N I I ' ~ G I T I S CLINICAL DATA TYPES

NU1V~BER

RECOVERED

DIED

~i0RTALITY

6 40 5

0 30 0'

6 10 5

100% 25% loo%

51

30

21

42%

Fulminating Acute Chronic basilar Total

TABLE

II

COMPLICATIONS ACUTE COMPLICATIONS

NO.

PHASE

] [0.

CONVALESCENCE NO.

E [ED

Hydrocephalus (9) Strabismus (4) Bronchopneumonia (4) Iridoehoroiditis (3) Otitis media (2) Pupillary paralysis (2) Staphylococcic infections (3) Cerebral thrombosis (1)

0 4 0 3 2

0 0 0

NO.

9 0 0 0 0 0 0

0 --

0

o

o

0 0 2 3 0

0 0 0 0 3 0

0

FINAL

NO. DIED

J

STAGES

NO. DIED

SILVERTHOI~NE ET AL. :

]V[ENINGOCOCCUS

493

" c h r o n i c b a s i l a r " death resulted, whereas in a relatively high proportion of those cases classified as " a c u t e " recovery occurred. Of the 10 fatal cases of the acute type 3 deaths were due to staphylococcal septicemia, staphylococcal meningitis, and staphylococcal brain abscess, respectively. I f these 3 be deducted, the m o r t a l i t y in the " a c u t e " group is reduced f r o m 25 to 14 p e r cent. BACTERIOLOGIC EXAMINATION

1. Cerebrospinal Fluid.--Cultures were obtained by planting the centrifugalized deposit from 5 to 10 c.c. of fluid directly into I per cent dextrose beef infusion broth and on to blood agar. The microorganisms were obtained from each of the cases u n d e r review, and no case has been included on clinical grounds alone. Identification of the microorganisms isolated was made by microscopic, cultural, and agglutination tests. 2. Blood Culture.--Ten cubic centimeters of blood obtained from the external jugular or median basilic vein were planted directly into 50 c.c. of 1 per cent dextrose broth, incubated overnight, examined microscopically, and subcu]tured on 10 per cent sheep's blood beef infusion agar. The original blood cultures were examined after 24 hours' incubation and re-examined at 48 hours and 72 hours. They were not incubated longer because experience had shown that this was valueless. In only 8 instances out of 28 in which Mood cultures were made was N. meningitidis obtained. This is probably due to the fact that admissions to hospital were after the p r i m a r y bacteriemic stage of the disease. In this connection it is noteworthy that the 8 positive results were obtained in patients who had presented symptoms for two or three days. 3. Nasopharyngeal Cultures.--West tube swabs were taken of the nasop h a r y n x and the material was plated immediately on 10 per cent sheep's blood agar plates. The plates were incubated aerobically overnight; suspicious colonies were selected, examined microscopically, and subcultured on 10 per cent sheep's blood agar slopes. N. meningitidis was identified by microscopic, culture, and agglutination reactions. TABLE III SOUI~CE OF IVIENINGOCOCCI ISOLATED F R O M PATIENTS SOURCE

C e r e b r o s p i n a l fluid Blood Nasopharynx Blo od s m e a r s p u r p u r i c l e s i o n s

NUIVIBER 51 28 24 7

POSITIVE 51 8 24 6

NEGATIVE 0 20 0 1

4. Purpuric Spots.--The lesions were p u n c t u r e d with a piece of sterile, broken, pointed glass after thorough cleansing of the skin. N. meningitidis was identified on a basis of morphology in the smears. No attempts were made to cultivate the organisms. Positive results were

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THE

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obtained in 6 of the 7 examinations made (Fig. 1). A similar finding of the organisms in the p u r p u r i e spots has been recorded b y McLean a n d Caffey. ~7 EPIDEI~IIOLOGIC DATA

Two series of investigations were carried out : - (1) Investigations on the Family From Which the Case Was Derived. - - T h e homes of 42 of the 51 patients were visited within a few days of the admission of the child to hospital. The e n v i r o n m e n t a l conditions w e r e studied, and the clinical h i s t o r y of the contacts was obtained, and a bacteriologic e x a m i n a t i o n of the n a s o p h a r y n g e a l cultures of the entire f a m i l y was made.

:Fig. l.--Organisms

from

purpuric

spots.

E n v i r o n m e n t : The findings of the survey are given in Table IV. I t is noteworthy that no less t h a n 90 per cent of the patients came f r o m homes which were poverty-stricken, in the w o r s t residential quarters of the city. Overcrowding was the rule r a t h e r t h a n the exception. The f a m i l y in most instances was living in one or two rooms. Race: There was no p r e d o m i n a n t racial incidence. Season: The disease occurred m a i n l y in the autumn, winter, and spring months of the year.

SILVERTHORNE

ET AL. :

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495

P r e v i o u s I l l n e s s in t h e F a m i l y : No c o r r e l a t i o n was o b t a i n e d b e t w e e n the o c c u r r e n c e of a ease of m e n i n g i t i s a n d p r e v i o u s c o n t a c t w i t h meni n g i t i s b y o t h e r m e m b e r s of t h e f a m i l y . T h e i n c i d e n c e of u p p e r r e s p i r a t o r y t r a c t i n f e c t i o n was p a r t i c u l a r l y s t u d i e d . T w e l v e of t h e 42 ' ! p a t i e n t c o n t a c t " g r o u p s r e v e a l e d a h i s t o r y of such i n f e c t i o n s . These i n f e c t i o n s were f o r t h e m o s t p a r t s t a t e d to be " c o l d s " or " i n f l u e n z a . " B a c t e r i o l o g i c E x a m i n a t i o n of C o n t a c t C a r r i e r s : Nasopharyngeal c u l t u r e s w e r e t a k e n Of t h e c o n t a c t s w i t h W e s t t u b e swabs, a n d t h e mat e r i a l was p l a n t e d i m m e d i a t e l y on 10 p e r c e n t s h e e p ' s b l o o d a g a r plates. TABLE I V

EPIDEMIOLOGIC

DATA

Number of families visited 'Environmental conditions

42

Overcrowding Filth Poor ventilation

37 19 18

Possible etiological factors Number with history of upper respiratory infection Number of families with history of previous contact with a ease of meningitis

12 3

TABLE V ]~]PIDEMIOLOGIG DATA : BACTEtCIOLOGIC EXAMINATION OF CONTACTS

Total number of persons examined Total number of positive cultures of the meningococcus Percentage positive cultures Number of families studied Number of cases from these families Number of families in which one ot' both parents were carriers Number of families in which other members were carriers

327 102 31 42 42 33 3

The p l a t e s were s u b s e q u e n t l y s p r e a d a t t h e l a b o r a t o r y a n d i n c u b a t e d a e r o b i c a l l y o v e r n i g h t ; s u s p i c i o u s colonies w e r e p i c k e d , e x a m i n e d microscopical]y, a n d s u b c u l t u r e d on 10 p e r c e n t s h e e p ' s b l o o d a g a r slopes. N. meningitidis w a s i d e n t i f i e d b y m o r p h o l o g i e a n d c u l t u r a l c h a r a c t e r i s tics a n d a g g l u t i n a t i o n tests. T a b l e V s u m m a r i z e s t h e b a c t e r i o l o g i c exa m i n a t i o n of these contacts. T h i r t y - o n e p e r c e n t of c o n t a c t s w e r e carr i e r s of t h e m e n i n g o c o c e u s , a n d in 33 f a m i l i e s of t h e 42 e x a m i n e d one or b o t h p a r e n t s w e r e f o u n d to be c a r r i e r s .

2. Investigation on a Group of Healthy A d u l t s Living in Toronto.-Bacteriologic Examination: D u r i n g f o u r a n d o n e - h a l f y e a r s of t h e seven-year study, nasopharyngeal cultures were examined monthly from a g r o u p of h e a l t h y a d u l t s w h o w e r e n o t k n o w n t o h a v e b e e n in c o n t a c t w i t h c a s e s of m e n i n g i t i s . S i m i l a r b a c t e r i o l o g i c t e c h n i q u e w a s u s e d as in t h e case of c o n t a c t c a r r i e r s . T a b l e V I I s u m m a r i z e s t h e f i n d i n g s . I t w i l l be o b s e r v e d t h a t o f t h e 2,378 s w a b s t a k e n , 20 p e r c e n t w e r e

496

THE JOURNAL OF PE:DIATRICS

positive f o r the meningocoeeus. The t o t a l n u m b e r of individuals examined ~in the period of s t u d y was 70, a n d 32 of these individuals, or 45 p e r cent, were positive at one time or another. I t m a y be noted, however, t h a t the 20 p e r cent positive culture r a t e in the n o n c o n t a c t carrier g r o u p is only slightly lower t h a n the 31 per cent found in the contact carriers examined. TABLE VI

EPIDElVIIOLOGIC DATA : :BACTERIOLOGIC ANALYSIS OF CASE AND ~ARRIEI% STRAINS N u m b e r of families completely studied N u m b e r of families in which case and carrier Strains were identical N u m b e r of families in which case and carrier strains were not identical

33 2:1 12

TABLE V I I EPIDEI~IOLOGIC D A T A :

:BACTERIOLOGICAL EXAMINATION OF ~]-ORIV~ALINDIVIDUALS (NONCONTACTS) Period of study Total number of swabs taken Total number of positive cultures obtained Total number of individuals swabbed in 489 years Average number of individuals swabbed monthly Percentage positive cultures

489 years 2378 499 7O 5O 20 9

I n this g r o u p of h e a l t h y adults it was f o u n d t h a t certain individuals were p e r s i s t e n t carriers over a m a t t e r of m o n t h s and years, others carried the meningococcus i n t e r m i t t e n t l y , while others were t r a n s i e n t carriers as n o t e d b e f o r e ? s I n 1936 R a k e 29 f o u n d t h a t a carrier m i g h t cease to h a r b o r the meningococcus a f t e r an u p p e r r e s p i r a t o r y infection. W e h a v e also observed t h a t the d e v e l o p m e n t of n a s o p h a r y n g i t i s in a persistent c a r r i e r would often be followed b y the d i s a p p e a r a n c e of the c a r r i e r state; on the other hand, it was f o u n d t h a t the onset of an upper r e s p i r a t o r y infection in some individuals initiated the carrier state. INVESTIGATION OF THE STIgAINS ISOLATED

Strains of meningococci, 20 f r o m cerebrospinal fluid, 17 from the nasop h a r y n x of these cases, 1 f r o m a case of meningitis with T y p e I meningococcus in the nasopharynx, 19 f r o m the n a s o p h a r y n x of contact carriers, and 22 f r o m the n a s o p h a r y n x of noncontact carriers, preserved, as soon a f t e r isolation as possible, in dried state in h a r d glass ampoules sealed u n d e r vacuum, were examined for virulence and type.

Determination of type was carried out b y two methods.

(a) A method

described b y Rake 3~ was used as follows: All agglutinations have been carried out i n water baths regulated to the required temperature. ~'or antigen a s t a n d a r d suspension has been adopted consisting of a suspension of meningococei of a sufficient density to give a reading of 4 cm. when tested with a Gates turbidometer and corresponding to about 2,000,000,000 organisms per cubic centimeter.

SILVE:RTHOR,NE

ET

AL. :

497

MENINGOCO,CCUS

Three-tenths cubic centimeter of this suspension is added to an equal amount of the serum or serum dilution to be investigated, the two fluids are mixed, and the rack of tubes is placed in the appropriate water bath for the required length of time. When a temperature of 37 ~ C. is used, the tubes are removed after 2 hours and left in the icebox overnight, when a final reading is taken. The reading of the results must be largely a personal matter. In order to compensate for this, readings have been made by the same person throughout. A control tube with saline and suspension in equal parts is always inserted to detect salt sensitivity. When agglutinations are done at 56 ~ C. for 24 hours or longer, a second control tube of normal serum diluted ~o is added~ but this has been found unnecessary at the lower temperature. (b) T h e o t h e r m e t h o d lows :

was an agglutination

t e s t c a r r i e d o u t as fol-

Heat-killed saline suspensions of meningococci containing approximately 2,000,000,000 organisms per cubic centimeter were used as antigens. One-half cubic centimeter amounts of the antigen were added to the same volume of serial dilutions of Type I and Type I I sera which were previously absorbed by a sufficiently large absorbing dose of meningococci (]/~ to 89 c.e. of packed cells) to remove all Type I I agglutinins from Type I serum and vice versa. The suspensions of meningococci in tile type sera were then incubated at 56 ~ C. in a water bath overnight. Readings were made the next day. F o r s o m e y e a r s w e w e r e f r e q u e n t l y u n a b l e to a l l o c a t e s t r a i n s of m e n i n g o c o c c i to d e f i n i t e t y p e s w i t h s e r a p r e p a r e d f r o m a n t i g e n s o f t h e f o u r accepted types. Only by indirect typing, namely by preparing a rabbit s e r u m f r o m t h e s t r a i n t o be t y p e d a n d u s i n g c u l t u r e s o f t h e f o u r t y p e s of m e n i n g o c o e e i as s u s p e n s i o n s i n a g g l u t i n a t i o n tests, w e r e w e a b l e to d e m o n s t r a t e t h a t m o s t o f t h e s t r a i n s i s o l a t e d , e a r l y i n t h e c o u r s e of t h e s e s t u d i e s , w e r e T y p e I I . I n r e c e n t y e a r s w e h a v e u s e d t h e t w o m e t h o d s ref e r r e d to a n d h a v e f a i l e d to t y p e c e r t a i n s t r a i n s , a l t h o u g h o t h e r s t r a i n s have fallen into clearly defined serologic types (Table VIII). TABLE V I I I T Y P E AND V I R U L E N C E OF S T R A I N S OF 1V[ENINGOCOCCI TYPES

N0.

SOURCE

20 C . S . F . * 18 N.P.t

I

II

u

CROSS AGGLUTINATION WITtt I&II DOUBTFUL

10

10~I 10-2 10-3 10-~ 10-5 10-6 1G-7 10-s

~. a 2

4

2

11

1

3

1

]5

2

0

0

32

4

50

eases

19 22

N.P. Contact carriers N.P. Noncontact carriers Total

* C . S . F . ---- c e r e b r o s p i n a l ~ N . P . ---- n a s o p h a r y n x .

fluid.

I0

12

3

25

13

3

3

12

2

3

2

9

17

32

498

THE, J O U R N A L

OF P E D I A T R I C S

The two methods gave identical results in 36 per cent of the strains that were typed. I n 28 per cent no agglutination occurred by the first method, but agglutination occurred with the second method. I n 5 per cent of instances the type was obtained by the first method but not b y the second. I n no less than 31 per cent cross agglutination occurred to such an extent that we could not be certain of the type. The failure of the first method to t y p e 28 per cent of strains is probably due to the fact t h a t a low-titer serum was used. Most of the strains, 50 out of 79, were f o u n d to be T y p e I I (Table V I I I ) . Indeed, only four T y p e I strains have been isolated f r o m the group studied; three of these were from meningitis patients and one f r o m a carrier. Our results indicate that certain strains of meningococci are " n a r r o w , " and others are " b r o a d " in respect of their agglutination in t y p e sera. B r a n h a m a3 has demonstrated serologic diversity among strains of meningocoeci. D u r i n g the early y e a r s of our epidemiologic studies, typing" of strains was carried out with unabsorbed four t y p e sera. W e were unable with this method to type the strains isolated. We were interested, however, in ascertaining whether contact-carrier strMns were identical with ease strains in our family groups. Strains f r o m 33 family contact-carrier groups were studied in this way. The method used was the agglutinin absorption test as described by Butterfield and NeilP * with the modification t h a t a surplus of 1A e.c. of packed cells was added to 2 c.c. of 1/50 dilution of each serum to ensure complete absorption of agglutinins. Table I X gives an example of strains which p r o v e d by test to be identical by agglutinin absorption. TABLE I X

mL~TIO~ OF S ~ ANTIGEN

SERUI~{

A A B

+ + +

A serum A abs. A sermn A abs. A serum

]3 B A

+ + +

A serum B abs. A serum 13 a b s . A s e r u m

~%o

%00

~Aoo

%00

4 0 0 4 0 0

4 0 0 4 0 0

4 0 0 4 0 0

3 0 0 3 0 0

SALIN~

CONTROL 0

0

I t is q u i t e obvious f r o m this e x a m p l e t h a t strains A and B are identical in respect of complete a b s o r p t i o n of agglutinins f r o m A serum. I n two instances we r e s o r t e d to r e c i p r o c a l agglutinin absorptions and similar results were obtained. B y this technique we were able to d e m o n s t r a t e t h a t f r o m 21 families we obtained carriers with strains identical with the ease strain and in 12 families strains which were not identical with the case strains (Table V I ) . I t is difficult to explain some of the discrepancies in the a g g l u t i n i n a b s o r p t i o n tests: in the twelve instances in which the strains were of the same serologic t y p e but were not identical. I n s t a n c e s w h e r e the " p a r e n t s t r a i n s "

SILVERTIIORNE

ET

AL. :

MENINGOCOCCUS

499

were identical a n d other contact strains were not identical are also difficult to explain. I f a large n u m b e r of these c o n t a c t - c a r r i e r strains had been " r o u g h " v a r i a n t s and avirulent, the discrepancies might be accounted f o r (Wilson and MilesaT). I n only one instance was a strain " a v i r u I e n t " and thus possibly a "rough" strain (Table V I I I ) .

Determination of Virulence.--In examination of strains for virulence we have used the mouse-mucin test described b y Rake. sl The mice used in these experiments were obtained f r o m one colony of Swiss white mice which gave u n i f o r m results. Each batch of mucin was tested for sterility before use and with a previously known virulent strain of the meningococcus and f o u n d in each instance to be satisfactory. F r o m Table V I I I it is seen that the vast m a j o r i t y (90 per cent) of strains obtained from the spinal fluid and the n a s o p h a r y n x of these patients as well as from contact carriers possessed some degree of virulence. The virulence varied between 10 0 to 10 .8 (10 -s contain a p p r o x i m a t e l y 20 meningoeocei). On the other hand, only seven of the 22 strains (32 per cent} recovered f r o m n o n c o n t a c t carriers were f o u n d to be v i r u l e n t in mice. The fact t h a t the strains f r o m n o n c o n t a c t carriers t e n d to be a v i r u l e n t and those f r o m contact carriers, virulent, is of considerable i m p o r t a n c e . I n other words, 94 per cent of the case and c o n t a c t - c a r r i e r strains are virulent as c o m p a r e d to 32 p e r cent in the n o n e o n t a e t - e a r r i e r group. I n view of this, the r a t e of 31 p e r cent positive eultm'es in 327 contact carriers s w a b b e d assumes g r e a t e r significance t h a n 20 p e r cent positive cultures in 2,378 swabs t a k e n f r o m the n o n c o n t a e t - e a r r i e r group. I t is difficult to explain the finding t h a t most strains in the c o n t a c t - c a r r i e r group are v i r u l e n t w h e n m a n y of them fail to show t h a t t h e y are identical in the a b s o r p t i o n test. I n this connection reference may be made to the work of others in the e x a m i n a t i o n of strains of meningoeoeei isolated f r o m the n a s o p h a r y n x of healthy adults. Cameron 2~ demonstrated a noneontaet-earrier rate of 13 per cent in a g r o u p of 29 adults examined. D u d l e y and Brenn a n ~s r e p o r t e d a c a r r i e r r a t e of 50 per cent, p e r s i s t i n g for o v e r a year, . in the absence of eases of meningitis a m o n g the p e r s o n n e l of n a v a l and m i l i t a r y establishments. I n view of the f a c t t h a t we h a v e demons t r a t e d t h a t only 32 p e r cent of the cultures (7 out of 22) examined were v i r u l e n t in a g r o u p of normal adults, it is possible t h a t the carrier r a t e s r e p o r t e d b y C a m e r o n =4 and D u d l e y and B r e n n a n =s do not represent the true p e r c e n t a g e of carriers h a r b o r i n g disease-producing strains. R a k e =~ c o n t r i b u t e d additional i n f o r m a t i o n on this subject b y d e m o n s t r a t i n g t h a t strains of T y p e I I meningocoeeus are " f r e q u e n t in the t h r o a t s of n o r m a l i n d i v i d u a l s " not in contact w i t h eases "during endemic p e r i o d s . " These T y p e I I strains, however, R a k e p o i n t s out, " c a n also act as a p a r a s i t e and produce sporadic eases of the disease." H e states, however, t h a t b y and large most of these n o n c o n t a e t strains

500

THE

J O U R N A L O~ P E D I A T R I C S

of Type II are avirulent. These results are in complete agreement with our observations, and such researches suggest the necessity of testing the virulence of strains from cases, contacts and noncontacts before a proper evaluation of the carrier rate of potentially pathogenic strains may be arrived at or too many claims made for different therapeutic procedures. In view of the fact that determination of the virulence of meningococci is a highly artificial method, the ability of meningococci to resist the bactericidal power of human blood has been employed in the hope that it would provide additional information as to the potential pathogenicity of the organism for man. It was shown 3~ that a cerebrospinal fluid strain of the meningococcus from a patient with meningitis survived to the limiting dilution (10 -6) in samples of bloods (citrated) of 11 infants and 8 of 33 adults. On the other hand, avirulent strains do not survive in any sample of citrated human blood. 36 It is true, as we have shown, 3G that strains virulent for mice are able to survive in human blood. But recently strains have been encountered (particularly those frozen and dried for one to three years) which have retained their mouse virulence but have lost their ability to resist the bactericidal power of human blood. It is evident therefore that the correlation between the two methods of test need not necessarily always hold. And it may well be that the method of assay in blood is a more reliable method for the assessment of pathogenicity for man than is the mouse-mucin test. On the other hand, the fact that strains which once survived in human blood and after storage do not may be interpreted as an indication of degradation of such strains. It is quite evident that sporadic meningitis as it occurs in childhood is due to Type II meningococcus in which respect it differs from the adult epidemic form which is usually due to Type I meningococcus. This statement may find support from investigations that have been carried out during the past year2 ~ Recently a Type I strain of t h e meningococcus (No. 520 obtained from Dr. Rake) was found to survive to the limiting dilution (10 -6) when grown with samples of blood from 7 different adults. On the other hand, 5 of these bloods were markedly bactericidal to a recently isolated and equally virulent Type II strain. One could advance the hypothesis from the examination of these two strains that although they were equally virulent for mice, the. Type I strain would most likely be more pathogenic for a greater number of humans than the Type II strain2 * T h i s s a m e h y p o t h e s i s h a s b e e n s u g g e s t e d in c o n n e c t i o n w i t h p n e u m o c o e c a l i n f e c t i o n s in m a n in a r e c e n t p u b l i c a t i o n b y M a c l e a n , R o g e r s , a n d F l e m i n g . 38 T h e s e a u t h o r s f o u n d t h a t t h e s e n s i t i v i t y of d i f f e r e n t p n e u m o c o c e i to t h e a n t i b a c t e r i a l p o w e r of n o r m a l h u m a n blood is e x t r e m e l y v a r i a b l e . T h e y s t a t e t h a t " i t is l i k e l y t h a t t h i s v a r i a t i o n is r e l a t e d to t h e p a t h o g e n i c i t y of t h e s e cocci in m a n . "

SILVER T H O R N E ET AL. :

MENINGOCOCCUS

501

DISCUSSIOI~

There is thus m u c h evidence that the incidence of virulent strains is higher among contacts t h a n among noncontacts, and it is probable t h a t the infection is derived f r o m the former. I t is also noteworthy t h a t the m a j o r i t y of close contacts (parents) of the patients h a r b o r meningococci of the same t y p e a n d virulence. I t must, however, be borne in m i n d that the carriers m a y have been infected b y the case in their midst. This hypothesis is most unlikely in view of the history of u p p e r r e s p i r a t o r y infection in some of the carriers previous to development of the disease in the patient. SUMMARY ANn CONCLUSIONS 1. F i f t y - o n e cases of three clinical types of meningococcic meningitis are reported. The m o r t a l i t y was 42 per cent. I n 40 cases of the acute type the m o r t a l i t y was 25 per cent, and, if the three deaths f r o m complicating staphylococcal infections be deducted, the m o r t a l i t y was 14 per cent. 2. Gram-negative diplococei were f o u n d in blood smears of the p u r p u r i c lesions in 6 of the 7 patients examined. 3. F o r t y - t w o families were visited and environmental conditions investigated. 4. I n these families 327 contacts were examined for the presence of the meningococeus in their n a s o p h a r y n x and 102 persons (or 31 p e r cent) were f o u n d to be h a r b o r i n g meningococci. The m a j o r i t y of these strains tested (94 per cent) were v i r u l e n t for mice. 5. I n 33 of the 42 families, one or both p a r e n t s were f o u n d to be harboring meningococci. 6. I n a period of four and one-half years, 2,378 n a s o p h a r y n g e a l cult u r e s were examined f r o m an average of fifty individuals monthly. No less t h a n 20 per cent of the cultures were positive. 7. The m a j o r i t y of strains isolated f r o m cases, contact carriers and noncontact carriers are T y p e I I . 8. I t is suggested f r o m results of our experiments t h a t the bactericidal power of h u m a n blood against the meningococcus or the ability of strains to survive in h u m a n blood m a y be as i m p o r t a n t in assessing the potential pathogenicity of a strain of the meningococcus for m a n as is an artificial mouse virulence test. REFERENCES

1. Flexner, Simon: 3. Exper. Med. 9: 105, 1907. 2. l\letter, A., and Debr6, R.: La m~ningite c6r6bro-spinale, Paris, 1911, :~'r & Cie. 3. Gordon, M.H.: l~Iedical Research Council Special Report Series, No. 3, 1917. 4. Fildes, P., and Baker, S.L.: Medical Research Council Special Report Series, 1~o. 17, 1918. 5. FitzGerald~ J.G.: Canad. !Y[. A. 5. 6: 695, 1916. 6. Eastwood, A.: J-. ttygiene 17: 63, 1918.

502 7. 8. 9. ]0. 11. ]2. 13. 14. 15. ]6.

17. ]8. ]9. 20. 21. 22. 23. 24. 25. 26. 27. 28~ 29. 30. 3L 32. 33. 34. 35. 36. 37. 38.

TI-IE JOURNAL OF PEDIATRICS Griffith, F.: J. Hygiene 17: 124, 1918. Scott, W . M . : J. Hygiene 17: ]91, 1918. Ponder, C.: ft. Hygiene 17: 247, ]918. Tulloch, W . J . : J. Hygiene 17: 316, 1918. Glover, J . A . : J. I-Iygiene 17: 350, 367, 1918. Dopter, C.: L ' i n f e c t i o n m6ningococcique~ Paris, ]92], Bailli~re et Fils. Murray, E. O . D . : Medical Research Council Special Report Series, No. ]24, 1929. B l a e k f a n , K e n n e t h D.: Medicine 1: ]39, 1922. Neal, Josephine B., Jackson, H e n r y W., a n d Appelbaum, E m a n u e h J . A . 1VL A. 87: 1992, ]926. Norton, J~ F., Gordon, J. E., and others: J. Exper. Med. Vols. 4 & 5, 1930 a n d ]931. a. B r a n h a m , Sara E., Taft, Clara E , and Carlin, Sadie A.: U n i t e d States T r e a s u r y D e p t , Public H e a l t h Reports 46: No. 16, 1931. b. B r a n h a m , Sara E., and Carlin, Sadie A.: J. Bacteriol. 34: No. 3, 1937. Banks~ I-I. Stanley: L a n c e t 1: 747, 1931. Walker, W.: J. Roy. A r m y l~[ed. Corps, Dec., ]932, Jan. and Feb., 1933. Shaw, E. B., and The]ander, H . E . : J . A . M . A . 101: 746, 1933. Cantacuz6ne, J.: Office i n t e r n a t i o n a l d ' h y g i ~ n e publique 25: P a r t II, ]216, 1933. Tillett, William S., and Brown, Thomas McPherson: J o h n s Hopkins Hosp. Bull. 57: 297, 1935. Nicolau, I., a n d others: Arch. roum. de pathol, exp6r. 9: 365, 1936. Cameron, D . W . : Trans. Roy. Soc. Canad. 25: Section V, 97, ]93]. Dudley, S. l~.j and B r e n n a n , J . R . : J. Hygiene 34: 1935. Silverthorne, N.: J. PEDIAT. 9: 755, 1936. McLean, S., and Caffey, J . P . : Am. J. Dis. Child. 35: 357, 1928. Silverthorne, N.: J. PEDIAT. 9: 328, ]936. Rake, G.: Canad. Pub. Health J. 27: 105, 1936. Rake, G.: ft. Exper. Med. 57: 56], 1933. Rake, G.: J. Exper. Med. 61: 545, 1935. Silverthorne, N.: Studies on the Bactericidal Power of Human Blood (Unpublished). B r a n h a m , Sara E.: J. Immunol. 23: 49, ]932. Butterfield, C. T., and Neill, M. I-L: 9 T r e a s u r y Dept., U n i t e d States Public H e a l t h Service Hygienic L a b o r a t o r y Bull. ]24, 1920. Silverthorne~ N , and Fraser, D. T.: Brit. J. Exper. Pathol. 15: 362, ]934. Silverthorne, N., and Fraser, D . T . : J. Immunol. 31: 43, 1936. Wilson, G. S., and h~iles, A . A . : Brit. J. Exper. Pathol. 13~ ], 1932. Maclean, I a n H., Rogers, I