**2. Microbiological and laboratory profile**

*Mycobacterium* species that are considered typical are the tuberculosis specie; *M.tuberculosis.* Many species enclosed in genus *Mycobacteriaceae* are true human pathogens as *Mycobacteri‐ um tuberculosis* complex, that include *M tuberculosis, M bovis,* non pathogenic *M bovis* BCG, *M africanum, M caprae, M microti*, and *M pinnipedii* are characterized by different phenotypes and mammalian host ranges, displays the most extreme genetic homogeneity with 0.01 to 0.03% nucleotides variation only. Growth rate in this group is 6 to 12 weeks. *M leprae* is the only non cultivable in vitro specie and has some genetic variations in relation to *M tuberculo‐ sis complex*.

The only genus of the *Mycobacteriaceae* family is the *Mycobacterium*, the *Mycobacteriaceae* be‐ longs to the order *Actinomycetales*. Mycobacteria is an unusual ocular pathogen that has the following characteristics: intracellular bacilli, slow growing organisms, obligate aerobic, non-motile, non-capsulated, non-sporing, present a large amounts of lipids and true waxes in their cell walls, and are considered gram-positive and acid-fast.

Other places where NTM have been isolated are: contaminated tap water, saline solutions, disinfectant solutions, and hemodialyzers. Mycobacteria influences a number of ocular structures, including the cornea,iris, lens,retina, choroid and optic nerve.

Clinical manifestations of the typical mycobacteria are : lupus vulgaris on eyelid, phlycte‐ nule, scleritis, lacrimal gland involvement, orbital periostitis, granulomatous panuveitis, sec‐ ondary glaucoma and cataract, chorioretinal plaque or nodule, nerve palsies.

The incidence of tuberculosis has increased due to the growth in homelessness, the upsurge of intravenous drug abuse, neglect of tuberculosis programs, acquired immunodeficiency syndrome.

Runyon classified nontuberculous mycobacteria into four groups, described in [Table 1]. Runyon Classification of tuberculous and non-tuberculous *Mycobacterium* is based, on the growth rate, and pigment production. Groups I to III are slow growers that require approxi‐ mately 2 to 3 or more weeks to form visible colonies in culture at 27°C. Group IV organisms are rapid growers, forming non-pigmented colonies in culture in one week.[1,14,15]

Out of the more than 130 actually validated species of non-tuberculousmycobacteria, 60 are slowly growingmycobacteria*,* that shows in solid culture media growth rates of 2 to 4 weeks*,* the most clinically significance and most frequently in isolated human samples are *M avium, M intracellulare, M kansasii, M marinum, M xenopi, M malmoense and M ulcerans.* In the rapidly growing mycobacteria group with 7 -10 days of growing rate on solid culture media, there are three major clinically important species responsible for 80% of diseases in humans *M chelonae, M abscessus* and *M fortuitum,* that are too frequently located in tap water and have been related with sepsis in bone marrow transplant, post-traumatic, surgical ocular and other surgical wound infections.


**Problem statement:** To describe the experience in México (Asociación Para Evitar La Ceguera I.A.P. "Hospital Dr. Luis Sánchez Bulnes" [APEC]) in the management of keratitis caused by nontuberculous mycobacteria.

**Application area:** Cornea and Refractive Service and Mycrobiology Service

*chelonei*, *M. abscessus*, *M. fortuitum*, *M. szulgai*, and *M. mucogenicum* have been reported as the

Atypical Mycobacteria corneal infections are rare, but devastating complications. Although rare, are a diagnostic and therapeutic challenge. Mycobacterium have been involved in sev‐

*Mycobacterium* species that are considered typical are the tuberculosis specie; *M.tuberculosis.* Many species enclosed in genus *Mycobacteriaceae* are true human pathogens as *Mycobacteri‐ um tuberculosis* complex, that include *M tuberculosis, M bovis,* non pathogenic *M bovis* BCG, *M africanum, M caprae, M microti*, and *M pinnipedii* are characterized by different phenotypes and mammalian host ranges, displays the most extreme genetic homogeneity with 0.01 to 0.03% nucleotides variation only. Growth rate in this group is 6 to 12 weeks. *M leprae* is the only non cultivable in vitro specie and has some genetic variations in relation to *M tuberculo‐*

The only genus of the *Mycobacteriaceae* family is the *Mycobacterium*, the *Mycobacteriaceae* be‐ longs to the order *Actinomycetales*. Mycobacteria is an unusual ocular pathogen that has the following characteristics: intracellular bacilli, slow growing organisms, obligate aerobic, non-motile, non-capsulated, non-sporing, present a large amounts of lipids and true waxes

Other places where NTM have been isolated are: contaminated tap water, saline solutions, disinfectant solutions, and hemodialyzers. Mycobacteria influences a number of ocular

Clinical manifestations of the typical mycobacteria are : lupus vulgaris on eyelid, phlycte‐ nule, scleritis, lacrimal gland involvement, orbital periostitis, granulomatous panuveitis, sec‐

The incidence of tuberculosis has increased due to the growth in homelessness, the upsurge of intravenous drug abuse, neglect of tuberculosis programs, acquired immunodeficiency

Runyon classified nontuberculous mycobacteria into four groups, described in [Table 1]. Runyon Classification of tuberculous and non-tuberculous *Mycobacterium* is based, on the growth rate, and pigment production. Groups I to III are slow growers that require approxi‐ mately 2 to 3 or more weeks to form visible colonies in culture at 27°C. Group IV organisms

Out of the more than 130 actually validated species of non-tuberculousmycobacteria, 60 are slowly growingmycobacteria*,* that shows in solid culture media growth rates of 2 to 4 weeks*,* the most clinically significance and most frequently in isolated human samples are *M avium, M intracellulare, M kansasii, M marinum, M xenopi, M malmoense and M ulcerans.* In the

are rapid growers, forming non-pigmented colonies in culture in one week.[1,14,15]

in their cell walls, and are considered gram-positive and acid-fast.

structures, including the cornea,iris, lens,retina, choroid and optic nerve.

ondary glaucoma and cataract, chorioretinal plaque or nodule, nerve palsies.

result of improper asepsis.

148 Common Eye Infections

*sis complex*.

syndrome.

eral isolated cases as well as in outbreaks.[4-12]

**2. Microbiological and laboratory profile**

**Research course:** To describe of atypical *Mycobacterium* keratitiscases diagnosed and attended in the Cornea Service of our Hospital in the last 10 years.

**Methods:** This is a descriptive retrospective case series of five patients treated in our service.

**Table 1.** Runyon's Classification of Nontuberculous Mycobacterium

#### **3. Laboratory diagnosis and bacteriology**

In ophthalmological infections traumatic or post-surgical in origin, are frequently involved in non-tuberculous or atypical fast growing *Mycobacteria*, the species *M. chelonae, M. chelo‐ nae /abscesus*, *M. fortuitum* have been isolated in many cases. These rapidly growing *Mycobac‐ teria* share the cellular characteristics of *Mycobacterium* genus,like mycolic acids esters in its cell wall*,* long straight or curved rods with irregular Gram staining [Figure 1], and specific red-magenta staining characteristic with Ziehl-Neelsen or Kinyoun cold techniques.[Figure 2] They are aerobic and capable of growing in 5 -10% CO2 atmosphere and in blood agar media.[Figure 3] In addition, these microorganisms are arylsulfatase positive, catalase posi‐ tive and niacin negative. [Figure 4]

**Figure 2.** Red-magenta rods of *M. chelonae* in a corneal smear of patient with keratitis.

**Figure 4.** Catalase 65oC positive test (O2 bubbles) for *Mycobacterium chelonae*.

To identify the microorganism, its phenotypic characteristics were used, such as pigmenta‐ tion of colonies growing in the darkness (presented in Table 1) on Lowenstein-Jensen media.

The most common species of rapidly growing *Mycobacteria* belong to group IV of Runyon's classification, also known as colorless or nonchromatogens.[Figure 5]

**Figure 5.** *Mycobacterium chelonae* colonies in Lowenstein-Jensen medium after 7 days of incubation at 27oC.

For genotypic characterization, the 16Sr RNA gene sequencing, high performance liquid chromatography and polymerase chain reaction has been used.
