Page 112 - Journal of Special Operations Medicine - Spring 2015

Figure 1 Blood agar plate demonstrating 24 hours of growth Figure 3 Nymph of Periplaneta americana suspended in
at 37ºC of a pure culture of Staphylococcus sciuri. 10mL of normal saline solution.

behavior has persisted into the modern era and has re­
sulted in the emergence of cockroaches as a ubiquitous
pest in urban environments. 26,27,30,31 Cockroaches tend to
feed on garbage and sewage at sites heavily contami­
Figure 2 Gram stain of Staphylococcus sciuri demonstrating nated with pathogenic microorganisms. This is problem­
gram-positive cocci in clumps and clusters.
atic, because cockroaches can harbor between 7 million
and 14 million microorganisms on the external cuticle
and at least 7 million organisms in the gut. Pathogens
26
such as Escherichia coli, Pseudomonas aeruginosa, and
Klebsiella species have been isolated from cockroaches
dwelling within human habitats. 26,30,31,32 Cockroaches
have been directly implicated in at least one outbreak
of dysentery. Therefore, human environments may be
33
ideal for these pests’ development and propagation, as
most human habitats are maintained at constant tem­
perature and humidity, and contain numerous sources
of food.

The finding of S. sciuri associated with a P. americana
is significant given the history of the cockroach in the
spread of disease. 26,27,30 In addition, it should be noted
that the organism was removed from the cuticle of the
Discussion cockroach by gentle agitation and washing of the cuticle
Cockroaches are members of the order Blattodea. They with sterile saline, indicating that the organisms were not
28
are typically characterized by unique reddish­brown firmly attached to the cuticle. This instability increases
coloration; a dorsoventrally flattened, oval body; and the possibility of mechanical transmission. It should also
distinctive positioning of the antennae (Figure 3). Cock­ be noted that recent studies have revealed that several
roaches are considered to be tropical insects; although strains of S. sciuri are hydrophilic. Hydrophilic organ­
34
Hawaii has no native cockroach species, at least 19 dif­ isms can be readily dispersed into liquid media such as
ferent species have been unintentionally introduced into water, intravenous solutions, and medication. In human
the islands over the last 200 years. This has resulted in environments, the mechanical spread of a hydrophilic
28
an almost uniform distribution of these insects through­ organism by an insect vector can have disastrous conse­
out the islands and recognition of these organisms as quences. For example, consider the contamination of a
significant pests. The two species most commonly as­ water source by contaminated insects or the movement
sociated with human habitats are the small German of insects across the surface of moist food, leaving an
cockroach (B. germanica) and the larger American cock­ expanding trail of bacteria in their path.
roach (P. americana). 28
Recent evidence has indicated that S. sciuri may be the
Cockroaches first appeared during the late Triassic pe­ ancestor to all modern Staphylococcus species. 3,6,19,20
riod (approximately 200 million years ago). They most Furthermore, although most strains of S. sciuri are
29
likely emerged as scavengers, feeding on the remains left methicillin sensitive, many harbor an inactive mecA ho­
behind from dinosaurs and other large vertebrates. This molog (mecA1), which may have been the progenitor of

102 Journal of Special Operations Medicine Volume 15, Edition 1/Spring 2015