Abstract
The emergence of staphylococci, either coagulase negative (CNS) or coagulase positive (CPS), as important human pathogens has implied that reliable methods for their identification are of large significance in understanding the diseases caused by them. The identification and characterization of staphylococci from biopsies taken from human breast tumors is reported here. Out of 32 tissue biopsies, a total of 12 suspected staphylococci grew on mannitol salt agar (MSA) medium, including 7 fermenters and 5 non-fermenter staphylococci based on traditional laboratory methods. Polymerase chain reaction (PCR) successfully identified seven isolates at the genus level as methicillin resistant Staphylococcus spp. by targeting a common region of the mecA gene. Only two of the seven bacteria were S. aureus based on the three-specific primers designed to amplify the housekeeping gene recN, and two of the virulence genes icaD and pvl. Diagnosing the isolates using the Vitek system revealed different findings. Although 6 of 7 isolates belonged to the Staphylococcus genus, including: S. cohnii subsp. cohnii, 2 isolates; S. lentus, 2 isolates; and one isolate for each S. auricularis and S. xylosus, the last bacterium was completely different (Aerococcus viridans). Concerning the two bacteria characterised as S. aureus by PCR, they were identified as S. lentus by Vitek with comparatively low detection probabilities of 93% and 88%. The data of this study indicate that undoubtedly PCR is a reliable and accurate test for identification of mannitol fermenter and salt tolerant bacteria in comparison with other tests that depend mainly on biochemical characteristics.
Highlights
Cancer formation induced by bacteria has been suggested as a consequence of bacterial infection [1, 2], which constitutes one step among multistep process needed for real cell transformation and cancer development
The 10 swabs obtained from different areas and equipment in the surgical hall of the same hospital from which tumor biopsies were collected showed negative growth on mannitol salt agar (MSA) indicating the sterility procedures followed by the hospital
Molecular identification Thermal cycler successfully amplified a partial region of 280 bp of the mecA gene in 7/8 of the tested isolates, in which isolate number 7 was intentionally used as a control that showed methicillin susceptibility on Mueller Hinton agar
Summary
Cancer formation induced by bacteria has been suggested as a consequence of bacterial infection [1, 2], which constitutes one step among multistep process needed for real cell transformation and cancer development. Chronic bacterial infections increase the possibility to initiate tumorigenesis because of the increasing chance to encountering a pre-transformed cell [3]. In this context, S. aureus has been suggested to contribute to tumor formation by producing chronic inflammation, which causes production of various cytokines, including tumor necrosis factor that has been associated with all steps of tumor development. S. aureus has been shown to cause dangerous medical problems in humans by. These genetic changes and instabilities might not be the cause, but the result of cancer cell formation. The role played by carcinogens, infectious agents and correlating factors is the induction of cellular senescence instead of mutagenic [5]
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