Exploring the Numerous and Dynamic World of Actinomycetes: Unveiling Their Ecological Significance, Biotechnological Potential, and Medicinal Purposes

Exploring the Numerous and Dynamic World of Actinomycetes: Unveiling Their Ecological Significance, Biotechnological Potential, and Medicinal Purposes

 

INTRODUCTION

Actinomycetes are a household of micro organism that kind lengthy, branch-

ing filaments that resemble the hyphae of fungi (Determine 22–1).

They’re gram-positive, however some (reminiscent of Nocardia asteroides)

are additionally weakly acid-fast rods (Desk 22–1).

Extra data relating to the scientific features of

infections attributable to the organisms on this chapter is supplied

in Half IX entitled Infectious Ailments starting on web page 589.

ACTINOMYCES ISRAELII

Illness

Actinomyces israelii causes actinomycosis.

Essential Properties & Pathogenesis

Actinomyces israelii is an anaerobe that kinds a part of the nor-

mal flora of the oral cavity. After native trauma reminiscent of a damaged

jaw or dental extraction, it could invade tissues, forming fila-

ments surrounded by areas of irritation.

Medical Findings

The everyday lesion of actinomycosis seems as a tough, non-

tender swelling that develops slowly and ultimately drains

pus by sinus tracts (Determine 22–2). Laborious, yellow granules

(sulfur granules) composed of a mass of filaments are shaped

in pus.

In about 50% of instances, the preliminary lesion includes the face

and neck; in the remainder, the chest or stomach is the location. Pelvic

actinomycosis can happen in girls who’ve retained an intra-

uterine gadget for an extended time period. Actinomyces israelii and

Arachnia species are the commonest causes of actinomycosis

in people. The illness shouldn’t be communicable.

Laboratory Prognosis

Prognosis within the laboratory is made by (1) seeing gram-

constructive branching rods, particularly within the presence of sulfur

granules and (2) seeing development when pus or tissue specimens

are cultured below anaerobic circumstances. Organisms may be

recognized by immunofluorescence. Notice that in distinction to N.

asteroides (see later), Actinomyces shouldn’t be acid-fast. There are

no serologic checks.

Therapy & Prevention

Therapy consists of extended administration of penicil-

lin G, coupled with surgical drainage. There isn’t a important

resistance to penicillin G. No vaccine or prophylactic drug is

out there.

NOCARDIA ASTEROIDES

Illness

Nocardia asteroides causes nocardiosis.

Essential Properties & Pathogenesis

Nocardia species are aerobes and are discovered within the setting,

notably within the soil. In immunocompromised people,

they’ll produce lung an infection and should disseminate. In tis-

sues, Nocardia species are skinny, branching filaments which might be

gram-positive on Gram stain. Many isolates of N. asteroides are

weakly acid-fast (i.e., the staining course of makes use of a weaker solu-

tion of hydrochloric acid to decolorize than that used within the

stain for mycobacteria). If the regular-strength acid is used, N.

asteroides will decolorize.

Medical Findings

Nocardia asteroides usually causes pneumonia, lung abscess

with cavity formation, lung nodules, or empyema. From the

lung, the organism can unfold to numerous organs, notably the

mind, the place it causes mind abscess. Illness happens most frequently

in immunocompromised people, particularly these with

decreased cell-mediated immunity. Nocardia brasiliensis, a differ-

ent species of Nocardia, causes pores and skin infections within the southern

areas of america and mycetoma, often in tropical

areas.

Laboratory Prognosis

Prognosis within the laboratory includes (1) seeing branching rods

or filaments which might be gram-positive (see Determine 22–1) or weakly

acid-fast in an acid-fast stain and (2) seeing cardio development on

bacteriologic media in a number of days.

Therapy & Prevention

Therapy is with trimethoprim-sulfamethoxazole. Surgical

drainage may be wanted. Occasional drug resistance

happens. No vaccine or prophylactic drug is offered.

SELF-ASSESSMENT QUESTIONS

1. Your affected person is a 75-year-old lady with fever and a painful nod-

ule on her forearm. She additionally has a nonproductive cough that she

says is worse than her standard smoking-related cough. She is taking

high-dose corticosteroids (prednisone) for an autoimmune dis-

ease. Chest X-ray reveals a nodular lesion in the correct higher lobe.

A biopsy of the nodule on her arm was obtained. Gram stain of

the specimen confirmed filaments of gram-positive rods. The rods

had been additionally weakly acid-fast. Relating to the causative organism,

which one of many following is most correct?

(A) Tradition of the organism must be accomplished below anaerobic

circumstances.

(B) The pure habitat of the organism is the soil.

(C) It produces an exotoxin that inhibits protein synthesis by

ADP-ribosylation.

(D) Sulfur granules are sometimes seen within the pores and skin lesion.

(E) The vaccine in opposition to this organism comprises the capsular poly-

saccharide because the immunogen.

2. Your affected person is a 20-year-old man who was in a fist struggle in a bar

about 3 weeks in the past. He took a punch that broke his left second

molar. He now has a 3-cm infected space on the pores and skin overlying the

damaged tooth that’s draining pus. A Gram stain of the pus reveals

gram-positive filamentous rods. The rods didn’t seem pink in

the acid-fast stain. Relating to the causative organism, which one

of the next is most correct?

(A) Infections attributable to this organism happen primarily within the

Ohio and Mississippi River Valley space.

(B) The pure habitat of the organism is the soil.

(C) This organism is immune to each penicillins and

aminoglycosides.

(D) Sulfur granules are sometimes seen within the pus positioned on the orifice

of the sinus tract within the pores and skin lesion.

(E) The vaccine in opposition to this organism comprises a toxoid because the

immunogen.

ANSWERS

(1) (B)

(2) (D)

SUMMARIES OF ORGANISMS

Temporary summaries of the organisms described on this chapter

start on web page 653. Please seek the advice of these summaries for a fast

assessment of the important materials.

PRACTICE QUESTIONS: USMLE &

COURSE EXAMINATIONS

Questions on the subjects mentioned on this chapter may be discovered

within the Medical Bacteriology part of Half XIII: USMLE

(Nationwide Board) Observe Questions beginning on web page 715. Additionally

see Half XIV: USMLE (Nationwide Board) Observe Examination