Abstract
Nocardiosis is an infectious disease caused by Nocardia species that occurs worldwide, albeit more prevalently in tropical/subtropical regions. It can appear as either acute, subacute or as a chronic infection mostly with those with a compromised/weakened immune system. Inhalation of spores and or mycelium fragments is the main transmission route for developing pulmonary nocardiosis. In contrast, cutaneous nocardiosis usually occurs via direct contact. In the subtropical region of the Sunshine Coast in Australia foaming events with thick and persistent and orange-brown color foam have been observed during summer seasons in the near shore marine environments. This study reports the existence of nocardiae in these near shore marine environments by the use of a novel isolation method which used the gas requirements of nocardiae as a selective battery. A total of 32 nocardiae were isolated with the use of this novel method and subsequently conducted molecular identification methods confirmed that the isolates belonged to the genus Nocardia. Twenty-one isolates out of the 32 were closely related to N. nova strains MGA115 and one was related to CBU 09/875, in addition when compared with human pathogenic nocardiae twenty of the isolates were found to be related to N. nova strain JCM 6044. Isolates displayed varied resistance against some of the antibiotics tested when interpretation threshold recommended the Comite de L’Antibiogramme de la Societe Francaise de Microbiologie were used. The highest level of resistance against cefotaxime (n = 27) and ceftriaxone (n = 24). Some of the isolates (n = 6) that displayed resistance to selected antibiotics also possessed potential human pathogenic characteristics such as adherence and translocation through human long epithelial cells as well as displaying phage resistance (n = 26). They might thus present a potential public health risk if frequently encountered through exposure to aerosols generated by the foam as well as direct contact through a wound. Preventative measures to control the growth of nocardiae in such environments such as the control of pollutants, might prevent potential infections that might be caused by these bacteria in humans as well as in marine animals.
Highlights
Members belonging to the genus Nocardia of the phylum Actinobacteria and the order Corynebacteriales [1] are classified as Gram-positive and filamentous bacteria [2]
The foaming events in the Sunshine Coast region of Australia along coastal shorelines, lakes and streams were frequently coincided with adverse/turbulent weather conditions when excess pollution in effluent water runoff at near-shore marine environments was observed https://www.qld.gov.au/environment/ pollution/management/disasters/flood-impacts They carried similar characteristics of the foam color and density reported by Fryer and Gray [15]
Facultative anaerobic characteristics of nocardiae resulted in their survival in the anaerobic chamber and clearance of background bacterial flora (Figure 1 A–F) which would under aerobic conditions would overgrow nocardiae colonies and render them unculturable
Summary
Members belonging to the genus Nocardia of the phylum Actinobacteria and the order Corynebacteriales [1] are classified as Gram-positive ( many species display a level of acid fastness) and filamentous bacteria [2]. They are widely distributed [3,4,5], mostly saprophytic and ubiquitous in the environment and commonly found in soil, water bodies, and decaying vegetation [6]. The wastewater recycling industry normally utilizes nocardiae and other filamentous microorganisms for bioremediation in the anoxic phase of their treatment plants to metabolize dissolved nitrates (NO3-) [7,11,12]. Some of the isolates were closely related to human pathogenic ones reported in other parts of the world [17]
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