Elsevier

Diseases of the Chest

Volume 39, Issue 2, February 1961, Pages 129-139
Diseases of the Chest

Preliminary Report: Epidemiology of Infections Due to the Atypical Acid-Fast Bacilli

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SUMMARY

  • 1.

    The atypical mycobacteria are distinct bacteriologic entities differing from M. tuberculosis both in cultural and biochemical characteristics and in animal pathogenicity. They need to be more adequately defined bacteriologically.

  • 2.

    The atypical mycobacteria need to be considered as actual or potential human pathogens with variations in pathogenicity by groups. They are less capable than M. tuberculosis of producing progressive pulmonary disease.

  • 3.

    Of all our known cases, elderly white men constitute the group of largest number. Preliminary data suggest that the colored race, and especially the colored male, has the higher attack rate.

  • 4.

    Men who were born and have lived most of their lives in the rural southeast are most commonly involved with the non-photochromogens.

  • 5.

    People found to harbor these organisms belong chiefly to the low socio-economic stratum.

  • 6.

    There is in our series a distinct seasonal variation in the occurrence and/or recognition of newly identified cases.

  • 7.

    The available data suggest a clustering by families of those exhibiting evidence of exposure to these bacteria, but conclusive evidence of transmission from man to man has not been obtained.

  • 8.

    The habitat of these organisms remains uncertain; they could be derived from an extra-human source—possibly the soil.

  • 9.

    Production of overt disease by these bacteria may be related to previous pulmonary abnormality and lowered pulmonary resistance.

  • 10.

    All aspects of these infections must have additional study.

Introduction

Max Pinner1 in 1935 emphasized the need of a critical evaluation of the significance of atypical acid-fast micro-organisms isolated from human sources. He was among the first to suggest a possible cause-effect relationship between these “saprophytes” and human disease. Our knowledge concerning the “Atypical” (also designated the “Anonymous” or the “Unclassified”) mycobacteria has increased considerably during recent years,2, 3, 4, 5, 6 but the natural habitat and communicability of these organisms remain unknown.7, 8, 9, 10, 11

Since late 1955, in Florida we have been concerned with the mode(s) of transmission and source(s) of the atypical mycobacteria. It was evident from a pilot epidemiological investigation that a long-range exacting field study would be necessary. A research grant was approved by the National Institutes of Health and a formal study became fully established in April, 1959. Presently, our special study revolves about three intimately related primary objectives: the source, the methods of transmission and the person to person communicability of these organisms.

Most of the cases upon which this report is based have come to our attention because they were either known or suspected of having tuberculosis, or they were contacts of known tuberculosis cases. Our major case-identification procedure has been the isolation of atypical mycobacteria from routine specimens examined for M. tuberculosis by public health and tuberculosis hospital laboratories. Recently, the Veterans Administration Hospitals of Florida and several private and community hospitals have assisted by submitting any acid-fast organisms which appear to be “Atypicals.” In addition, the increasing interest of Florida physicians, as well as our own epidemiological investigations, is resulting in the examination of specimens for acid-fast organisms from patients with a variety of pulmonary syndromes, patients with non-pulmonary disease and from people without manifest abnormality.

The atypical acid-fast organisms, as a group, are easily differentiated bacteriologically, from M. tuberculosis. They are subdivided into four groups designated with Roman numerals I (photochromogens), II (scotochromogens), III (non-photochromogens) and IV (rapid growers). The classification is based upon the work of Dr. Runyon6 and depends upon the temperature requirements for growth of these organisms, their ability to produce various pigments when exposed to light, their rate of growth, their uniform avirulence for the guinea pig and their pathogenicity for certain other laboratory animals.

For this presentation, the terms “isolation,” “infection” and “case” are used interchangeably and mean simply that atypical acid-fast bacilli have been cultured one or more times from the body fluids or tissues of a specific person. There may or may not be an associated pathologic process.

Section snippets

Distribution of Atypical Types

During the four years that the Florida laboratories have been studying this special group of bacteria, 585 cases have been identified (Table 1). Approximately 75 per cent of them are due to the Group III atypical mycobacteria, the non-photochromogens. Only 4.9 per cent are due to the Group I, photochromogens. Reports from elsewhere in the United States indicate that the non-photochromogens are found predominantly in the Southeast; other sections of the United States have reported more commonly

Age, Race and Sex

The age istribution is shown in Table 2. The atypical mycobacteria have been isolated only rarely from the young. They are found predominantly in the aged. Of our known cases, 51.8 per cent are above age 54; 88 per cent are above age 34. This distribution differs strikingly from that of the general population, as shown in the Table.

Table 3 presents the race and sex of these people. Approximately three-fourths are males. The white male is the group of largest number. The computed rates for 1959 (

Variations in Incidence with Time

Figure 1 depicts the varying incidence of newly identified atypical infections since the beginning of our studies. There has been a gradual increase in incidence over the past five years. The obvious seasonal peak, which occurred in early 1959 and appears to be recurring in 1960, is particularly impressive. It is reasonable to suspect that a proportion of the gradual increase is due to increasing awareness of these organisms by the laboratories. The explanation of the seasonal peaks is not

Geographic Considerations

There is evidence that infections due to the non-photochromogens are found predominantly in the Southeastern United States. The results of skin tests with the Battey Strain tuberculin (PPD-B) on Navy recruits and other groups by United States Public Health Service teams12 provide strong support for this view.

In Florida, variations between counties of both rates of newly found infections and rates of positive reactors to Battey-tuberculin have been noted. Workers in Georgia find a similar county

Tuberculin Sensitivity

To gain further insight into the natural history of these infections, mass tuberculin surveys have been undertaken in selected sections of Florida. Table 6 reflects the results of Mantoux tests with typical (PPD-S) and atypical (PPD-B) tuberculins* among first and second grade public school children in three selected counties of Florida. The total of 1,677 children tested constitutes

Tests on Contacts

The household associates of 55 school children who were positive to PPD-B alone, 14 school children who were positive to PPD-S alone and the contacts of 80 patients known to be infected with non-photochromogenic atypical acid-fast bacilli were examined with tuberculin tests, chest x-ray films and sputum cultures. The results of these studies are summarized in Table 7.

One hundred and ninty-one household contacts of the 55 school children positive to PPD-B were tested with both PPD-B and PPD-S.

Pathology Associations

Adequate clinical records have been obtained, to date, on 386 (90 per cent) of the 428 persons in Florida from whom non-photochromogens have been isolated. In only 146 (38 per cent) of the 386 cases is there reasonably secure evidence of a primary cause-effect relationship between the atypical organism and demonstrable pathology. Four of these had evidence of acid-fast disease of the kidney and 142 had x-ray evidence of pulmonary pathology. All yielded only non-photochromogens upon repeated

Comment

It appears that the non-photochromogenic atypical organisms are widely distributed. If it can be assumed that PPD-B sensitivity is indicative of past exposure to these organisms, results of tuberculin tests indicate that these are not uncommon infections and that a fairly large percentage of the population comes in contact with them early in life. Our limited epidemiological data suggest a familial clustering of these infections; but there is no evidence that they are commonly transmitted from

RESUMEN

  • 1.

    Las micobacterias antípicas son entidades bacteriologicas que difieren del micobacterium tuberculosis tanto en los cultivos como en las características bioquímicas y su patogenicidad en los animales.

  • 2.

    Las micobacterias atípicas necesitan considerarse como verdaderos patógenos humanos con variaciones en su patogenicidad por grupos. Son menos capaces de producir enfermedad pulmonar progresiva que el M. tuberculosis.

  • 3.

    De todos los casos conocidos el grupo mayor se encuentra entre los ancianos de raza

RESUMÉ

  • 1.

    Les mycobactéries atypiques sont des entités bactériologiques distinctes du M. tuberculosis à la fois par leur caractère de culture, par leur nature boichimique, et par leur action pathogène chez l'animal. Elles demandent à être déterminées bactériologi-quement avec une plus grande précision.

  • 2.

    Les mycobactéries atypiques doivent être considérées comme des germes actuellement pathogènes pour l'homme ou susceptibles de le devenir avec des variations du pouvoir pathogène selon les groupes. Elles

ZUSAMMENFASSUNG

  • 1.

    Die atypischen Mykobakterien sind deutliche bakteriologische Wesenheiten und unterscheiden sich vom M. tuberculosis sowohl durch kulturelle als auch biochemische Merkmale und hinsichtlich der Tierpathogenitat. Sie müßen aber eine bakteriologisch besser angepaßte Definition erfahren.

  • 2.

    Die atypischen Mykobakterien müssen als aktuelle Oder potentielle für den Menschen pathogene Keime angesehen werden mit Gruppenvariationen in der Pathogenität. Sie sind weniger als der M. tuberculosis im Stande, eine

References (13)

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These investigations are supported in part by Grant No. E2377 from the National Institute of Health.

Presented at the 26th Annual Meeting, American College of Chest Physicians, Miami Beach, Florida, June 8-12, 1960.

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