Nocardiosis occur due to an aerobic actinomycete in the “genus Nocardia”, an unusual gram +ve bacteria. It is most commonly seen in im/m. (immunocomp
NOCARDIOSIS
Clinical
manifestations:
1) Nocardiosis occur due to an aerobic actinomycete in the “genus Nocardia”,
an unusual gram +ve bacteria. It is most commonly seen in im/m. (immunocompromised)
ptns, e.g., kidney transplant recipients.
2) Three
locations are most commonly involved: the lungs,
central nervous system (CNS), &
the skin. There’re no pathognomonic Sns
or Sms for nocardiosis. It should be
suspected in any ptn presenting with brain,
soft tissue, or cutaneous involvement and a concurrent or
recent pulmonary affection.
3) The
lungs are commonly the primary location of nocardial
infection in more than 2/3rd
of ptns. Onset of pulmonary nocardiosis could be acute,
subacute, or chronic and cannot be recognized by any particular
Sns or Sms.
4) Radiographic
criteria of pulmonary affection are variable and may include single or multiple nodular
lesions, lung mass (with or with no cavitation), reticulo-nodular infiltration, interstitial infiltrates, lobar consolidated
lesions, sub-pleural plaque, & pleural effusion.
5) CNS involvement accounts for about 20
% of Nocardia
ptns and most often results from disseminated
infection coming from pulmonary or cutaneous
locations. However, the hallmark of
CNS Nocardial infection is the formation of parenchymal abscesses that can be observed in any zone of the brain
tissues.
6) 4 patterns of skin involvement can be seen: primary cutaneous, lymphocutaneous,
cutaneous involvement from a disseminated focus, & mycetoma.
7) Most
cutaneous lesions develop owing to the direct
traumatic inoculation of the pathogen
into the skin.
8) Disseminated nocardial infection can be defined
as 2 or more non-contiguous locations of affection that may or may not involve lung
focus.
Diagnosis
(1) Final
diagnosis of nocardial infection needs isolation + identification
of the pathogen from a clinical sample.
(2) To establish
a Dgx of nocardiosis is somehow problematic as an invasive intervention
is usually warranted to get an adequate sampling
and recovering of Nocardia in the lab is somehow difficult owing
to its slowly growing nature.
(3) With
the prompt clinical subset, a presumptive Dgx of nocardial disease can be established
if the partial acid-fast filamentous branched rods
are detected in clinical sampling.
(4) Nocardial pathogens in the routine aerobic culture usually need about 5-21 d to grow.
(5) Précised speciation & susceptibility tests of clinical
specimen is crucial as resistant patterns
vary by species varieties.
(6) PCR can provide more
accurate & rapid result for the Dgx of nocardial
infection as compared to
the conventional techniques but it is
not currently available in most clinical labs.
(7) Isolated
Nocardia
are usually referred to a reference lab for precise recognition
& susceptibility
testing.
(8) Regarding
of the higher affinity of Nocardia pathogen to induce CNS infection, an urgent brain imaging is
currently mandated for ALL im/m. ptns and in ALL ptns with pulmonary nocardial disease.
REFERENCES
3.
Sorrel TC, Mitchell DH, Iredell JR, Chen SC-A.
Nocardia Species. In: Principles and Practice of Infectious Diseases, 7th ed,
Mandell GL, Bennett JE, Dolin R (Eds), Churchill Livingstone Elsevier,
Philadelphia 2010. p.3199.
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