Page 113 - Journal of Special Operations Medicine - Spring 2015

the antibiotic­resistance determinant in MRSA. 3,6,19,20 As whether such transmission is possible or the conditions
discussed, mecA encodes a modified form of the penicil­ that would be necessary for this to occur. Future studies
lin­binding protein that is the target of the beta­lactam will include determining how long S. sciuri can survive
class of antibiotics. The mecA homolog in S. sciuri is con­ on the cuticle of common cockroach species, determining
sidered to be a “silent” gene in that it does not lead to whether S. sciuri is present in the gut of the insect, and
the production of high levels of altered penicillin­ binding determining whether it can be dispersed from the cuticle
protein. A series of elegant studies by the Tomasz group under normal conditions.
at Rockefeller University demonstrated conclusively that
mecA1 can be converted to fully functional mecA when S. Disclaimer
scirui is exposed to antibiotic pressure from the applica­
tion of steadily increased concentrations of methicillin to The views expressed in this publication/presentation
the culture media. Further, these authors demonstrated are those of the author(s) and do not reflect the official
35
that this conversion was due to a single nucleotide change policy or position of the Department of the Army, De­
(from an adenine to a thymine) in the promoter region of partment of Defense, or the US Government.
the mecA gene (the promoter is a genetic structure that
controls gene expression level). This single nucleotide Disclosure
change resulted in an increased expression of the alter­
native penicillin­binding protein and a conversion from The authors have nothing to disclose.
methicillin sensitivity to methicillin resistance.
References
The fact that a single nucleotide change can convert a
methicillin­sensitive strain of S. sciuri into a methicillin­ 1. Couto I, Wu SW, Tomasz A, de Lencastre H. Development
resistant strain can have important public health impli­ of methicillin resistance in clinical isolates of Staphylococcus
cations. For example, this property may limit the use sciuri by transcriptional activation of the mecA homologue
native to the species. J Bacteriol. 2003;185:645–653.
of methicillin with sensitive strains as a means of pre­ 2. Haenni M, Chatre P, Boisset S, et al. Staphylococcal nasal
venting the development of resistance. In addition, since carriage in calves: multiresistant Staphylococcus sciuri and
antimicrobial­resistance determinants are often trans­ immune evasion cluster (IEC) gene in methicillin resistant
ferred from one strain to another, S. sciuri may serve as Staphylococcus aureus ST398. J Antimicrob Chemother. 2011;
66:1927–1938.
a reservoir for an antibiotic­resistance trait that can be 3. Harrison EM, Paterson GK, Holden MT, et al. A novel hy­
transferred to other staphylococcal species. 35,36 This may brid SCCmec­mecC region in Staphylococcus sciuri. J Anti-
be particularly true in the case of co­infection between microb Chemother. 2014;69:911–918.
S. sciuri and other bacterial species. 37 4. Kloos WE, Ballard DN, Webster JA. Ribotype delineation
and description of Staphylococcus sciuri subspecies and their
Although S. sciuri is an emerging pathogen that is not potential as reservoirs of methicillin resistance and staphylo­
lytic enzyme genes. Int J System Bact. 1997;47:313–323.
currently recognized as a significant threat, accurate 5. Lang S, Livesley MA, Lambert PA, et al. The genomic diver­
identification of this agent is necessary to deliver proper sity of coagulase­negative staphylococci associated with noso­
treatment. Indeed, the differentiation of S. sciuri from comial infections. J Hosp Infect. 1999;43:187–193.
S. aureus is essential for the interpretation of antibiotic­ 6. Rolo J, de Lencastre H, Miraqaia M. High frequency and
susceptibility tests, because the critical breakpoints nec­ diversity of cassette chromosome recombinases (ccr) in
methicillin­susceptible Staphylococcus sciuri. J. Antimicrob
essary for determining antibiotic sensitivity or resistance Chemother. 2014;69:1461–1469.
can differ between these two species. This difference 7. Severin A, Wu S, Tabei K, et al. High­level beta­lactam re­
12
can be a problem in resource­limited settings, which sistance and cell wall synthesis catalyzed by the mecA
are often lacking in the proper equipment or techniques homologue of Staphylococcus sciuri introduced into Staphy-
lococcus aureus. J Bacteriol. 2005;187:6651–6658.
required for speciation. Cognizance of the biochemical 8. Kloos WE, Schleifer KH, Smith RF. Characterization of
and antibiotic sensitivity differences between these two Staphylococcus sciuri sp.nov. and its subspecies. Int J System
species, therefore, is essential for personnel engaged in Bact. 1976;26:22–37.
identifying and treating cases of both S. aureus and S. 9. Wallet F, Stuit L, Boulanger E, et al. Peritonitis due to Staphy-
sciuri infection. It is essential that military medical per­ lococcus sciuri in a patient on continuous ambulatory perito­
neal dialysis. Scand J Infect Dis. 2000;32:697–768.
sonnel be aware of the existence of S. sciuri and be fa­ 10. Sawicka-Grzelak A, Szymanowska A, Mlynarczyk A, et al.
miliar with the traits of this organism so that they can Production of staphylokinase and hemolysin by coagulase­
both recommend and apply the appropriate diagnostic negative staphylococcus. Med Dosw Mikrobiol. 1993;45:7–10.
test and treatment regimens during training scenarios, 11. Ahoyo TA, Yehouenou Pazou E, Baba-Moussa L, et al.
as well as in real­world operations. Staphylococcus sciuri outbreak at a tertiary hospital in Benin.
J Med Microb Diagn. 2013;2:126.
12. Coimbra DG, Almeida A, Junior J, et al. Wound infection by
While this study demonstrates the potential for vector­ multiresistant Staphylococcus sciuri identified by molecular
mediated transmission of S. sciuri, it does not demonstrate methods. New Microbiol. 2011;34:425–427.

Staphylococcus sciuri: Entomological Case Study and Brief Review 103