STRUCTURE AND FUNCTIONS OF THE MYCOfi •2TERIAL CELL ENVELOPE Minnikin, D.E. & O'Donnell, A.G. (1984), Actinomyeete envelope and peptidoglycan, in "The Biology of the Actinomycetes" {M. Goodfellow, M. Mordarski & S.T. Williams} (pp,337-388). Accad. Press, London, New York. Minnikin, D.E.. Mianikin, S,.M., Porlett, J.H., Goodfellow, M. & Magnusson, M. (1984) Mycolic acid patterns of some species of Myco13acterium. J. gen. MicrobiaL, 139, 225-231.

Minnikin, D.E., Minnikin, S.M., Parlen, J.H. & GoodfeUow, M. (1985), Mycolic acid patterns of some rapidly-growing species of Mycobacterium. Zbl. Bakt. Hyg. A., 259, 446-460, Rastogi, N. & David, H.L. (1988), Mechanisms of pathogenicity in mycobacteria. Biochimie, 70, 1101-1120. Ridell, M., Minnikin~ D.E., Parlen, J.H. & Mattsby-I~ahzcr, I. (1986L Detection of mycobac-

427

terial lipid antigens by a combination of thin-layer chromatography and immunostaining. Letters AppL MicrobiaL, 2, 89-92. loriyama, S., Yano, I., Masui, M., Kusunose, M. & Kusunose, E. (1978). Separation of C~o.~ and CTos0 mycolic acid molecular species and their changes by growth temperatures in &lycobacteriurn phlei. FEBS Letters, 95, 11t-1|5.

Contributing factors of pathogenesis in the Mycobacterium avium complex W.W. B a r r o w Department o f Microbiology and Immunology, Texas College o f Osteopathic Medicine, 3500 Camp Bowie Blvd., Fort Worth, T X 76107 (USA)

It is reasonable to assume that mycobacterial pathogenicity, at least in the context of the Mycobacerium avium complex, results from factors which are subtle in nature and which promote "virulence" by either protecting the organism from the destructive properties of the host's maerophages (Draper and Rees, 1970; D r a p e r , 1974; Hooper et aL, 1986; Rastogi et aL, 1989; Woodbury and Barrow, 1989) and/or by modifying the immunological response of the host (Collin~, 1986; Brownback & Barrow, 1988; Hooper & I~arrow, 1988; Tsuyuguehi et aL, 1990) So that subsequent replication of the mycobacterial agent can continue. If one assumes that members of the M. avium complex possess potent "virulence" factors, then it would be difficult to explain why they do not occupy a higher status in the history of pathogenic microbial-

ogy. Instead, they occupy a small niche in the complex milieu of "opportunistic pathogens" and, for the most part, cause only subclinical infections (Wolinsky, 1979). Placed in the setting of an i m m u n o c o m promised patient, however, the classification of "opportunistic pathogen" can quickly transgress to the higher rank of "pathoBen", thus making the etiological agent an entity that must be accounted for clinically. Unfortunately, for patients suffering from AIDS, and the clinicians that must deal with these i m m u n o e o m p r o m i s e d individuals, the lack of information regarding "virulence . . . . pathogenicity" and " d r u g resistance" has generated a critical scientific void that makes it difficult, if not impossible, to successfully treat infections involving members of the M. avium c a m plex.

Pathogenicity of the M. avium complex is sometimes associated with eotony morphology and in that regard, opinions seem to vary. Some investigators feel that the smooth-transparent colony forms are more virulent, while others feel that the rough colony f o r m s tend to be. Perhaps both rough and smoothtransparent types can, under the right conditions, transgress to pathogenic status. This would imply that at least some of the factors that c o n t r i b u t e to pathogenicity are shared by both colony types and are expressed in ~he cell envelope. Because of the nature of the mycobacteriaI cell envelope, it is likely that a number of these factors are lipids which probably tend to accumulate within the environment in which the organism is growing. These accumulating lipids or other components have been viewed at the ultrastructural

428 levels as an electron-transparent zone (ETZ). Discussions of the ETZ are many and varied, but it appears that the original observations and suggestions by Draper and co-workers about the contribu. tion of C-mycosides in the formation of the E T Z (Draper and Rees, t970; Draper, 1974) are still valid. The C-mycosides accumulate in culture as a fibrillar material (Draper, !974; Kim et al.j 1976; Barrow et aL, 1980) and also within macrophages, as observed with freeze-etching techniques (Fukunishi et aL, 1982}. Draper's findings were further elaborated on by the observation that tile L~ layer of M. intracellulare serovar 20 is comprised primarily of the "polar C-mycosides" or glycopeptidolipid (GPL) seretype-specific antigens (Barrow et al., 1980}. Subsequent immunocytoehemistry confirmed the superficial localization and distribution of the GPL before and immediately following phagocytests by routine macrophage (Tereletsky and Barrow, 1983). In related studies involving the ETZ, others have identified the presence of a polysaccharide layer on the surface of members of the M. avium complex (Rastogi et aL, 1986) and suggested that this "polysacchariderich outer layer" (POL) is a complex matrix of glyeoproteins, saccharides and loosely-bound lipids that contribute to the ETZ (Rastogi and David, 1988). Rastogi and eoworkers further reported that even though the rough mutant derived from the smooth-colony forming serovar 20 does not synthesize GPL (Barrow and Brennan, 1982), it still forms an ETZ, presumably comprised of inert lipids which are removed by routine alcohol dehydration procedures (Rastogi and David, 1988). The same rough mutant, however, is also apparently just as resistant to macrophage destruction as its

7th FORUM IN MICROBIOLOGY

smooth-colony-forming parent strain (Rastogl et aL, 1989). Perhaps members of the M. avium complex synthesize a variety of components that are shed into the environment in which the organism is growing, If that environment happens to he a culture flask, then those components would probably have less of a tendency to accumulate around the mycobacteria, and instead disperse into the surrounding medium, particularly if a shake-culture technique is used. If that environment happens to he a macrophage, and those components are resistant to lysosomal degradation, then they would tend to accumulate in the phagolysosomal compartment surrounding the mycobacteria. These various components might not only contribute to the survival of the mycobacteria within the phagolysosomat compartment, but likewise increase the resistance of the mycobacteria to various antimycobacterial drugs (Crowle et aL, 1988). These same components would affect in vitro drug susceptibility to a lesser degree because they would not tend to accumulate around the mycobacterium in as concentrated a mass as would be expected within the phagocytic cell. The presence of these various components (presumably inert lipids) would also explain why rough mutants can produce an ETZ, even though they do not synthesize OPL. Thus it is possible that the rough mutants symhesize lipids other than the GPL which can also contribute to the formation of an ETZ, and perhaps the smooth-colonyforming parent strains produce GPL in addition to the other lipids. If this hypothesis is valid, then one might expect that rough and smooth-colony variants share common lipids that contribute to pathogenicity and drug resistance because of their localization in the cell envelope and/or accumulation on the sur-

face of the mycobacteria following phagocytosis. Thus, effective drug development will most likely have to include the use of multiple drugs, one or more of which increases penetration across the cell envelope (Hoffner et al,, 1989) (Rastogi and Goh, 1990). In a recent study (Tassel and Barrow, to be published), a group of patients infected with a member of the M. avium complex was investigated in an attempt to correlate immunological function in the presence of these opportunistic pathogens. Each of the patients in the study was selected because they had a chronic lung infection involving a member of the M. avium complex. All of the patients were HIV-negativ¢ and in a tow risk group for AIDS. There was no evidence of previous immunological dysfunction and, with the exception of their chronic M. aviura infection and loss of weight, they appeared to be in general good health. Flow cytometry was used to quantitate peripheral blood lymphocyte populations by using FITC-labelled monoclonal antibodies (Coulter, FL) directed to BI, B4, CD3, CD4 and CD8 epitopes, as described by Coulter (Coulter Clone procedures sourcebook, part # 4235141, Coulter Immunology, FL) for direct immunofiuoreseenee cell surface staining. Age-matched controls were examined with the same FITC-labelled monoclonal antibodies to provide a comparison for the M. uvium-infected patients. Drug susceptibilities and identification of mycobacterial isolates were determined by the Texas Department of Health, Bureau of Laboratories, Austin, Texas. Mycobacterial isolates were forwarded to us by the Texas Department of Health for further studies and were also sent to National Jewish Hospital (Denver, Colorado) for serotyping. Results of serotyping are pending.

STRUCTURE AND FUNCTIONS OF THE MVCOBACTERIAL CELL ENVELOPE Mycobacterial isolates were cultivated in 7H9 Middlebrook m e d i u m (Difco) c o n t a i n i n g glycerol and oleie acid-albumindextrose (OADC, Difco) and lipids were extracted f r o m mycobacterial cells as described previously (Barrow et al., 1980). Lipids were examined by thinlaver chromatography (TLC) anci G P L were detected with the orcinol-sulphurie acid reagent (Brennan et aL, 1978; Barrow et aL, 1980). C.olony morphology was assessed as either rough, transparent, or opaque (Schacf::r et al., 1970) after cultivation of isolates on 7H9 Middlebrook agar containing OADC, Cultures of 34. avium serotypes 1 (TMC # 706), 4 (TMC # 1463) and 8 (TMC # t468) were kindly supplied by Anna Tsang (National Jewish Hospital and Research Cemer, Denver, Colo.). Examination of M. avium isolates revealed variations in colonial morphology with the s m o o t h transparent a n d opaque

forms predominating (table 1). Only one isolate demonstrated rough morphology, and personal

communication with the Texas Department of Health Mycobacteriology Section confirmed the morphology to be consistent on several previous cultures during the last year. All isolates demonstrated multiple drug resistance (table I) and although serotyping information is pending, analysis of native and deacety!at,~d lipids extracted from the isolates (Brennan et el., 1878) indicated that none of the isolates had lipid profiles similar to the common zerotypes found in AIDS patients (i.e. serotypes, i, 4 or g). ;.n addition, lipid analysis of the rough isolate f r o m female patient 1 revealed a similar pattern to that of the previously described rough variant from ~erotype 20 (Barrow and Brennan, 1982) and a complete lack of any polar GPL components, as visualized by the orcinol reagent (Brennan et aL, I978). In all except one patient (female patient 4, table IlL a reduced C D 4 / C D 8 ratio was a p p a r e n t in the M. aviuminfected g r o u p . The most pronounced decrease was

429

observed in male patient 1 and female patient t (table II), whose CD4/CD8 ratios strongly suggest an immunodysfurtetion of some type. Because of the limited number of patients in this study, it is n o t possible to draw any definitive conclusions re[~arding the reduced CD4/CD8 ratios and the role o f the underlying M. o~ium infections as a possible contributing factor; however, several observations are interesting in regard to the topic of this Forum. First, all o f the patients oe~oustrated a redl~eed CD4/CD8 ratio with one exception, female patient 4, who was infected with an M. avium isolate that had only a smoothopaque colony type. Secondly, the isolates from the two patients that demonstrated the greatest decrease in the CD4/CD8 ratio represented the two ends of the spectrum with regard to colony morphology, rough and transparent. Even so, the organisms were able to persist in those patients for several years (since 1965 for male patient 1 and since 1968 for female patient 1), even

Table I. Patients and M. avium isolale information (as of 1989).

Male patients Patient 1

Age 68

Patient 2

59

Patient 3 ~'~ Patient 4

39 64

Female patients Patient 1 Patient 2

62 71

Patient 3 Patient 4

77 65

Colony morphology opaque with few transparent transparent with few opaque culture not available culture not available

Drugs-resistant I,Em,Rp,S,K,Cp, Et(3/90),Rb(3/90) I,Em,Rp

Drugs-susceptible Et(11/89y ")t°) Rb(11/89) ~'~')

.I,Em, Rp,S,K,Cp

Et,Cy

rough only opaque with few transparent culture not available opaque only

I,Rp,S,Et,K,Cp I,Rp,S,Et,K,Cp

Em,Rb Em

I,Rp,S,K,Cp

Em,Et,Rb

Drugs and concentration {ug/mI):l=isoniazid (1.0), Em ~ethambutol {5.0), Rp- rifampia (I.0), S-streptcrnycin (2.0), K= kataamycin {5.01, Cp E cap~eomycira(10.0), Cy = cycloserinc (20.0), Et = ethionamid~ (5.0). Rb = ~fabutin (2.0). (-i Diagnosis of M. avium infection wu~ made after only one culture i~olale from thi~. patient. ("r Drug pattern ¢haau:ed.

4,~0

7lfl FORUM 1N MICROBIOLOGY

TahOe I1. Flow eytometric data of peripheral blood drawn from patients infected with M, avlum complex wilh dates that blood was drawn given in parenthesis.

Bl Male controls ~'

Patient 1 (418o} (7/89) (11/89) Patient 2 (4/89) (7/89) (9/89) Patiem 3(~) (4/88) Patient 4 (8/88)

B4

CD3

5.1:!: 1.5

73.7±8.9

3.0 2.0 --

3.8 4.9 12

41,5 NA NA

13 32 31

19 34 42

0.7 0.9 0.7

12 2 2

3.1 6~7 7.4

69.5 NA NA

44 50 45

24

1.8

33

1,5

35

1.3

18.5

7.5

59.4

33

34

0.96

4

72

26

1.35

4.6_+2.3

19

Female controls (b~ 7.2±3.7

Patient 1 (7/89) (9/89) Patient 2 (7/89) (9/89) Patient 3 (7/89) Patient 4 (7/88) (4/89) (12/89)

3.4_+0.1 73.7_+6.7

CD4

CD8

CD4/CD8

43.1___8.7 18.9+4,6

35 50.2+8.7

2.5±0.9

(range !.6-3.0)

20.7__+7.6 2.69a: 1.0 (range 1.6-4.2)

1.2 2.0

4.0 3.1

NA NA

16.3 9.1

47.7 21.0

0,3 0.4

6,0 3.0

10.5 3. I

NA NA

18 11

28 7

0.6 1.6

3.0

3.9

NA

38

24

1.6

1.5 4.5 1.1

4.7 4.2 2.0

43.6 35.3 NA

27.8 23.6 64.1

9.6 5.2 10.3

2.9 4.5 6.2

CBl~ 4,

~dDi~gno~is of M . a~iurn infection was made ~ftcr only one culeure isolate from ~hl.5. patient, N A ~ non-at~plicable, Company discontinued supplying the fluor~cenl antibody tag.

though they had been on multipie drug therapy for most of that time. This wot, ld suggest that factors which contribute to longterm survival of the organism (presumably within the macrophages), were apparently operable in both the rough and smooth variants, thus supporting the hypothesis that rough and smooth variants share common factors that allow them to resist phagolysosome destruction. In addition, even though these patients have chronic long-term infections, they have not yielded to the disease, which also sup-

ports the previous suggestion that "virulence factors'* associated with the M. avium complex are subtle in nature and do not contribute overtly to pathogenesis. Thirdly, air isolates demonstrated multiple drug resistance, even though all three types were observed in this study. This finding suggests that the factors which contribute to in vitro drug resistance are present in all three colony types: rough, transparent, and opaque. Similar drug resistance findings for transparent and opaque colony forms were observed in a

study involving M. avium cornpie× infections in AIDS patients (Kiehn et al., 1985). If the mycobacterial cell envelope is a major determining factor for drug susceptibility (David, 1981; Rastogi et aL, 1981), then it is reasonable to expect that the contributing faetorz are perhaps lipide common to all morghological types and to-'areal in the cell envelope. Because the polar GPL are unique to the M. avium complex (Brennan and Goren, 1979; Goren and Brennan, 1979) and because they represent a major

431

STRUCTURE A N D FUNCTIONS OF THE M Y C O B A C T E R I A L CELL ENVELOPE

component in the cell envelope that may contribute to pathogenicity and drug resistance, we have been conducting studies in an effort to decipher the biosynthetic pathv~ay of these liquid components, tn that regard, we have examined rough variants derived from serotypes 4, 8 and 20, for the presence of potential G L P lipopeptide precursors. The rough variants were obtained as previously d e s c r i b e d (Barrow and Brennan, 1982) and internally r a d i o l a b e l l e d w i t h 14Cp h e n y l a l a n i n e (l+C-Phe) using procedures previously developed (Hopper et al., 1986; W o o d b u r y a n d Barrow, 1989). Separation o f the resulting radiolabelled lipids by H P L C revealed the presence of at least two t4C-Phecontaining lipopeptides that were c o m m o n to all three rough variants (peaks 1 and 2, fig. 1) (Wright and Barrow, to be published; also presented in part at the First International Conference o n the P a t h o g e n e s i s of Mycobaeterial Infections, Stockholm, June, 1990). At least one of the lipopeptides (peak t, fig. 1) is also f o u n d in the smoothcolony-forming parent strains of these serotypes. Limited chemical analysis o f peak I indicates t h a t it is a p h e n y l a l a n i n e containing lipopeptide that does not contain any carbohydrate. We are currently collaborating w i t h Dr. P a t r i c k B r e n n a n (Colorado State University) in a n effort to obtain a structural analysis of the lipopeptide to see if it may be a precursor in G P L biosynthesis or a lipid c o m m o n to both the rough and smooth forms of the organism.

i 3.84

,,m,

& I

I I

T'" I 7O

53

!!

1

I

°b

|

--I~

I I -i~mo{n~,n)

t

t

I

I

f 7D

1;

C ~o

_

L

,

t

,

~

,

)

,

,

,

',

t

I

t

I

0

70 1im0 lmml I II

Fig. 1. HPLC pattern of '+C-phe-radiolabelIed lipid from rough variant serovars 4 (A), 8 (BI and 20 (C). Lipids were separated on an '+LJItrasphere" 5 ~m spherical 80 ~ pore S1 analytical column (4.6x 250 rnml attached up a guard column containing the same solid support (4.6x45 ram)- Samples were analysed using a "Beckman System Gold Methods Development System which included a model 126 p+ogrammable solvent delivery module, a model 166 programmable variable UV detector (set at 257 am) and a 171 solid system radioisotope detector. Lipid samples were injected at concentrations ranging from 200 #g to 800 ~g and separated in a mobile phase of lO0~o chloroform for l0 min fo~|owed by a 40 rain gradient of 0-10% methanol in chloroform, at a flow rate of 1.0 ml/min.

Conclusions

It is reasonable to assume that pathogenicity o f the M. a v i u m c o m p l e x resutts f r o m many factors that contribute to the organism's ability to persist within the host a n d become refractive to various antimyco-

bacterial agents. A number of these factors are most likely lipids, glycolioids, peptidolipids or glycopeptidolipids, that have t h e t e n d e n c y to a c c u m u l a t e within or on the periphery of the m y c o b a e t e r i a l cell e n v e l o p e . Because of the variability regard-

ing colonial m o r p h o l o g y and virulence, it is reasonable to assume ",hat at least some of the f a c t o r s t h a t c o n t r i b u t e to pathogenicity and drug resistance are s h a r e d by the d i f f e r e n t colony types. It is therefore also plausib!e that the development of

432

7th FORUM IN MICROBIOLOGY

effective antimycobacterial therapy s h o u l d c o n s i d e r these paralnelers when defining specific targets for appropriate drug interaction.

plex. Infect. Immun., 56, t044-1050. Collins, F.M. (1986), Myrobacterium avium-complex infections and development of the acquired immunodeficiency syndrome: casual opportunist or causal cofactor ? Inter. j. Leprosy, 54, 458-474. Crowle, A,J., Elkins, N. & May, M.H. (1988), Effectiveness of ofloxacin against Mycobaeterium tuberculosis and Mycobacterium avium, and rifaml~in against M. tubereulo.. s/s in cultured human macrophages. Amet. Ray. Rezp. Dis., 137, 1141-1146. David, H.L. (1981), Basis for tack of drug susceptibility of atypical myeobacteria. Ray. inf. Dis., 3, 878-884. Draper, P. (1974), The myeoside capsule of Mycobacteriura avium 357. J. gen. MicrobioL, 83, 431-433. Draper, P. & Rees, R.J.W. {1970L Electron-transparent zone of mycobacteria may be a defense mechanism. Nature (Load.), 228, 860-861. Fukunishi, Y., Okada, S., Nishiura, M, & Kohsada, K. (1982), Ultrastruetural features of the multi0iieation of human and marine leprosy bacilli in macrophages of nude mice. Int. Z Leprosy, 50, 68-75. Goren, M, & Brennan, P.J. (1979), Mycobacterlal lipids : chemistry and biological activities., in "Mycobacterial lipids: chemistry and biological activities". (Youmans, G.P.) (63-193). W.B. Saunders Co., Philadelphia. Hoffner, S.E., Kratz, M,, Ols~onLifjequist, B., Svenson, S.B. & Kallenius, O. (1989), In vitro synergistic activity between ethambutol and fluorinated quinulones against Mycobacterium avium complex. J. Antimicrob. Chemother., 24, 317-324. Hopper, L.C. & Barrow, W.W. (1988), Decreased mitogenie response of murine spleen cell.~ following intraperitoneal injection of serovar-specifie glycopeptidolipid antigens from the Mycobacterium avium com~ plex. Advanc. exp. Med. Biol., 239, 309-325. Hopper, L.C., Johnson, M.M.,

I would like to acknowledge the contributions or S.K. Tassel and E.L. Wright to ~hcsc studies and -'hank ~. King.. R.N. (Texas Public Heahh Depart., Ft. Worth, TXL foc her as~islance in patient data collection, DF. Dunbar (Texas. Depl. O["Health, Austin. TX) [or identification and drug susceptibilities of M, avium isolmcs, and J,W. Mea:,el for the flow cytometrlc analysis. The research reported here was supported by United States Public Health Set,ice grant At 21946, f[om the National Institutes of Health. the Americait~ Osteopathic Association grant no, 8g-t 1-285, and the American Foundation for AIDS re.~careh grant no. 090322.

References Barrow, W.W. & Brennan, P.J. (1982), Isolation in high frequency of rough va.riant~ of Mycobacterium intracellulare lacking C-mycoside glycopeptidolipid antige'~s, J. BaeL, 150, 381-384. Barrow, W.W.. Ullom, B.P. & Bremaan, P.3. (1980), Peptidoglyeolipid nature of the superficial cell wall sheath of smo ot h - c o l o n y - f o : ' m i n g myc~hacter~.a.d. Bart., 144, 814-822. Brennan, P.J. & Goren, M.B. (1979L Structural studies on the type-specific antigens and lipids of the Mycobacterium aviumMycobacterium intracellulareMyeobacterium scrofulaceum serocompfex. J. biol, Chem., 254, 4205-4211. Brennan, P.J, Souhrada, M., Ullom, B,, ivicLiatchy, J,K. & Gorcn, M,B, (1978), Ider.tificanon of atypical mycohacteria by thin-inter chromatography of their surface antigens. J. Clin. MicrobioL, 8, 374-379. Brownback, P.E. & Barrow, W.W. (1988), Modified lymphocyte response to mitogens after intraperitoneM injection of glycopeptidoUpid antigens from Mycobacterium aviura cant-

Khera, V.R. & Barrow, W.W. (1986), Maerophage uptake and retention of radiolabeled glycopeptidolipid antigens associated with the superficial L t layer of Mycobacterium intraeetlulare serovar 20. Infect. Immun., 54, 133-141. Kichn, T.E., Edwards, F.F., Brannon, P., Tsang, A.Y., Main, M., Gold, J.W.M,, Whimbey, E., Wong, B., McClatchy, J.K. & Armstrong, D. (1985), Infections caused by Mycolmcterium avium complex in immunoeompromised patients: diagnosis of blood culture and fecal ~xamination, antimicrobial susceptibility tests, and morphologleal and seroagglutination characteristics, d. Gila. Microbiol., 21, 168-173. Kim, K.S., Salton, M.R.J. & Barksdale, L. (1976), Ultrastrueture of sup,, ficial mycosidlc integuments of Mycobaeteriura sp. £ Bart., 125, 739-743. Rastogi, N. & David, H.L. (1988), Mechanisms of pathogenicity in mycobacteria. Biochimie, 70, llOl-ll20. Rastogi, hi., Fr~he|, C. & David, H.L. (1986), Triple-layered structure of the mycobacteriai cell wail: evidence for the existence of a polysaccharide-rieh outer layer in 18 mycobacterial species. Curt, MierobioL, 13, 237-242. Rastogi, N., Frdhel, C., Ryter, A., Ohayon, H., Lesourd, M. & David, H.L. (1981), Multiple drug-resistance in JWyeobeeteriura avium: is the cell wall architecture responsible for the exclusion of antimicrobi~l agents? AtMmicrob. Agents a, Chemother., 20, 666-677. Rastogi, N. & Gob, K.S. (1990)~ Action of 1 isonicotinyl-2-paimitoyl hydrazine against the Mycobacterium avium complex and enhancement of its activity by m-fluorophenylalaline. Antimicrob, Agents. a. Uhemother., 34, 2061-2064. Rastogi~ N., Ldvy-Fr&bault, V., Blom-Potar. M. & David, H.L. {1989), Ability of smooth and rough variants of myeobacterium avium and M. intraceltulare to multiply and survive intracellulatly: Role of Cmycosides. Zbl. Bakt. Hyg, A 270, 345-360.

STRUCTURE AND FUNCTIONS OF THE MYCOBACTER1AL CELL ENVELOPE Schaefer, W.B., Davis, C.L. & Cohn, M.L. (1970), Pathogenicity of transparent, opaque, and rough variants of Mycobacterium avium Jn chickens and mice. Amer. Rev. Respir. Dis,, 102, 499-506. Tereletsky, M.J. & Barrow, W.W. (1983), Postphagncytic detection of glycopeptidolipids a~sociated with the superficial L~ layer of l~tycobacteriura

intraceltulum, infect, lmmun, 41, 1312-1321. Tsuyugttchi, 1., gawasumi, H., Taka~hima, T., Tsuyugu¢lli, T. & Kishimoto, S. (1990), Mycobecteriutn tzviaat-Mycobtxcierium intraceOulore complex-~nduced suppression of T-cell proliferation in vitro by regulation of monoc~te accessory cell ac~i,*ity, Infect. Immun., 58, 1369-137g.

433

Wolinsky, E. (19'79), Nontuber¢ulous mycobactetia and a~soeiated diseases. Amer,, Roy. Respir. Dis., I 19, 107-159. Woodbury, J.L. & Barrow, W,W. (1989), Radiolabetling of Myeobacrerium aviutn oligosaecharide determinant and use in macrophage studies. J. gen. M'ieJ'obiot., 135, Ig75t ~84.

Myeobacterial cell wall and pathogenicity: a lipodologist's view G . Landelle and M. D a f f , ~ Centre de Recherche de Biochimie et Gdndtique Cellulaires du CNRS, and UniveesiM P. Sabatier, t l & route de Narbonne, 31062 Toulouse cedex (France)

INTRODUCTION

As stated by H. Smith (i984), to be p a t h o g e n i c a m i c r o organism must be able to: 1) infect the mucous surfaces of the respiratory, alimentary or urogenital tracts; 2) enter the host, usually by penetration o~ the mucous surfaces; 3)multiply in the environment of host's tissues; 4) resist or interfere with host defence mechanisms that try to remove or destroy them; 5) cause damage to the tissues of the host. All five steps, or at least 3 if there is a direct introduction into the tissues, must be accomplished for pathogenicity. Loss o f ability to carry out any one of the steps causes the microbe to lose virulence. The cardinal fact about pathogenicity is its multifactoriai nature". Only the last two items are well documented for a number

of pathogens, but not so much for mycobacteria.

Resistance to host's defence~

It is currently assumed that ~ymphoeytes and 9hagoc~tes represent the main defence of infected hosts against mycobactcria. However, virulent mycobacterial strains are not eliminated by maerophages and, in addition, such bacteria have an intracellular development after phagocytosis, it could be proposed that this ~s at least partly due to disruption of phagolysosome membrane (by acyltrehalose sutphatides), inhibition of macrophage priming (by acyltrehalose sulphatides) or of macrophage activation [by lipoarabinomannan) and inhibition of lymphocyte proliferation (by arabinogalactan, lipoaratrirtomannan or phenolic glycolipids).

Damage to hosl

The origin of damage to host by mycobacteria is not wetl documented. No exotoxin is kr~awrt. The only 9 o t e u t i a l "endotoxins" are mycotic esters of wall glycoconjugates that inhibit both rezpiratioJa ant~ phosphorylatlon ill mitochondria (dimyco[oyl trehalo~e-= cord factor, monomycoloyl trehalose, mycoloyl diarabinose derived from acylated arabinogalactau). Durin~ mycobacteriosis, much of the damage may result from dysfunctions o f the immune system, e.g. T-cellmediated hypersensitivity reactions. This could, for instance be, at the origin of the tubercle liquefaction that leads to spreading of the infection in tuberculosis. Again, macrophages are supposed to be essential mediators o f this damage, since they are stimuIated by dimycotoyl treha-

Contributing factors of pathogenesis in the Mycobacterium avium complex.

STRUCTURE AND FUNCTIONS OF THE MYCOfi •2TERIAL CELL ENVELOPE Minnikin, D.E. & O'Donnell, A.G. (1984), Actinomyeete envelope and peptidoglycan, in "The...
491KB Sizes 0 Downloads 0 Views