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BRIEF COMMUNICATION
Year : 2017  |  Volume : 35  |  Issue : 2  |  Page : 277-278
 

Changing epidemiology of coagulase-negative staphylococci in normal flora of skin


1 Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh; Department of Microbiology, Apollo Hospitals, Chennai, Tamil Nadu, India
3 Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh; Department of Microbiology, Tagore Hospital and Heart Care Centre, Jalandhar, Punjab, India
4 Department of Transfusion Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India

Date of Web Publication5-Jul-2017

Correspondence Address:
Pallab Ray
Department of Medical Microbiology, Research Block-A, Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijmm.IJMM_16_282

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 ~ Abstract 

Coagulase negative staphylococci (CoNS) have recently emerged as important pathogens causing nosocomial blood stream infections. To evaluate the prevalence of CoNS in cutaneous normal flora, skin swabs were collected from voluntary blood donors and processed for culture and identification using matrix assisted laser desorption ionisation-time of flight (MALDI-TOF). CoNS were isolated from 96% of blood donors, most commonly Staphylococcus hominis (86%), followed by Staphylococcus epidermidis (22%) and Staphylococcus haemolyticus (9%). There has been a shift in the prevalent species of CoNS in the community in India, from the earlier known S. epidermidis towards resistant species such as S. hominis and S. haemolyticus. Routine and rapid speciation of CoNS in clinical isolates with MALDI-TOF should be used effectively to manage these resistant species.


Keywords: Coagulase negative, normal flora, staphylococci, Staphylococcus epidermidis, Staphylococcus haemolyticus


How to cite this article:
Gautam V, Sethuraman N, Kaur R, Sachdev S, Marwaha N, Ray P. Changing epidemiology of coagulase-negative staphylococci in normal flora of skin. Indian J Med Microbiol 2017;35:277-8

How to cite this URL:
Gautam V, Sethuraman N, Kaur R, Sachdev S, Marwaha N, Ray P. Changing epidemiology of coagulase-negative staphylococci in normal flora of skin. Indian J Med Microbiol [serial online] 2017 [cited 2017 Sep 26];35:277-8. Available from: http://www.ijmm.org/text.asp?2017/35/2/277/209581



 ~ Introduction Top


Coagulase negative staphylococci (CoNS) are a diverse group of Gram-positive cocci, commonly isolated from human skin as normal flora,[1] and recently recognised as a significant cause of nosocomial bloodstream infections.[2] This upsurge is associated with the increasing use of indwelling medical devices as well as rising number of critically ill patients.[3] CoNS account for 12%–80% mortality in hospitalised patients and also 16% morbidity has been associated with CoNS bacteraemia.[4] The multidrug resistant nature of the different CoNS species further aggravates the situation, limiting the treatment options for prevalent CoNS species.[2] However, routine speciation is not commonly done in most laboratories. By doing so, we are closing the precious therapeutic window for patients with invasive diseases. The usual conception is that infections caused by CoNS are predominantly caused by Staphylococcus epidermidis. However, the scenario is not the same now as earlier. The other species such as Staphylococcus haemolyticus and Staphylococcus hominis are taking over S. epidermidis. This recent shift in epidemiology is responsible for diverting much more attention towards CoNS species identification.[5] The relative abundance of different Staphylococcus species as normal flora of skin requires a re-evaluation. Hence, this study was taken up to evaluate the distribution of CoNS species in normal flora of a representative healthy population.


 ~ Materials and Methods Top


To evaluate the prevalence of CoNS in normal flora, a fixed surface area of 24 cm 2 over the cubital fossa was swabbed in 100 voluntary blood donors attending the blood bank between February and December 2014 at our tertiary care centre. Sterile cotton swabs moistened with Butterfields' phosphate buffer were used for sampling the skin surface and the swabs were resuspended in the same buffer. They were processed in the laboratory within 2 h of collection and inoculated on 5% sheep blood agar and MacConkey agar. Different morphotypes of colonies were picked up following overnight incubation and identified to species level using matrix assisted laser desorption ionisation-time of flight (MALDI-TOF) (Microflex LT, Bruker Daltonik GmbH, Leipzig, Germany) using Bruker Biotyper software v2.0 with a cut-off score of ≥2. As the study was performed on human subjects, ethics approval was obtained from the Institute Ethics Committee (NK/314/res/2875).


 ~ Results Top


The relative distribution of different Staphylococcus species in the normal flora of 100 healthy adult blood donors was studied [Table 1]. CoNS were isolated from 96% of donors. The most common CoNS isolate was S. hominis isolated from 86% of donors, followed by S. epidermidis (22%) and S. haemolyticus (9%).
Table 1: Relative distribution of different Staphylococcus species in normal flora of healthy blood donors

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 ~ Discussion Top


The microbial flora of skin is diverse between sites of a body and also within a site between individuals of a population. However, core microbiome consisting of most commonly shared species does exist.[6] Traditional culture methods have been used in the 1960s and 1970s to characterise normal flora of skin, which showed S. epidermidis as the most common species of Staphylococcus in normal flora.[7] However, there are very few studies in recent times demonstrating relative distribution of all cultivable species on skin in a large group of individuals. Hitherto, culture studies of the normal flora of skin have been more concentrated on the pathogenic species of Staphylococcus aureus.[8],[9],[10] With the rising importance of CoNS in bacterial sepsis, we felt it pertinent to reevaluate the relative abundance of Staphylococcus species in a large number of individuals. We selected the antecubital fossa to sample major cultivable bacterial flora as it is the site most commonly used to draw blood for culture, and also it is one of the moist sites of the body where staphylococci predominate as the major bacterial genus. We chose swabbing of a fixed surface area of the skin over more invasive procedures because the relative abundance of organisms in the different layers throughout the thickness of skin remains fairly constant.[11] Our study found that S. hominis was present in the antecubital fossae of 86% of individuals, whereas only 22% of individuals harboured S. epidermidis. This difference in distribution may be due to selective pressures even in the community due to widespread use of antibiotics in our country. S. haemolyticus, not described as a common commensal was the third most common commensal (9%). S. haemolyticus is a particularly difficult to treat species with high-level resistance to methicillin as well as vancomycin.[12] Hence, CoNS speciation must be a routine in all the diagnostic laboratories.

Rapid bacterial identification methods like MALDI-TOF-MS can be especially beneficial in diagnosis and early initiation of therapy. Identification using MALDI-TOF is based on bacterial intrinsic ribosomal proteins and has been shown to yield accurate results in a short time frame and at a much lower cost than any other routinely available microbiological techniques.


 ~ Conclusion Top


The epidemiology of coagulase negative staphylococci is shifting towards more drug resistant species. This underlies the need to rapidly identify clinical isolates of CoNS to species level using available robust methods such as MALDI-TOF.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
 ~ References Top

1.
Kloos WE, Bannerman TL. Update on clinical significance of coagulase-negative staphylococci. Clin Microbiol Rev 1994;7:117-40.  Back to cited text no. 1
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2.
John JF, Harvin AM. History and evolution of antibiotic resistance in coagulase-negative staphylococci: Susceptibility profiles of new anti-staphylococcal agents. Ther Clin Risk Manag 2007;3:1143-52.  Back to cited text no. 2
[PUBMED]    
3.
Shin JH, Kim SH, Jeong HS, Oh SH, Kim HR, Lee JN, et al. Identification of coagulase-negative staphylococci isolated from continuous ambulatory peritoneal dialysis fluid using 16S ribosomal RNA, tuf, and SodA gene sequencing. Perit Dial Int 2011;31:340-6.  Back to cited text no. 3
    
4.
Szymanska G, Szemraj M, Szewczyk EM. Species-specific sensitivity of coagulase-negative staphylococci to single antibiotics and their combinations. Pol J Microbiol 2011;60:155-61.  Back to cited text no. 4
    
5.
Usha MG, Shwetha DC, Vishwanath G. Speciation of coagulase negative staphylococcal isolates from clinically significant specimens and their antibiogram. Indian J Pathol Microbiol 2013;56:258-60.  Back to cited text no. 5
  [Full text]  
6.
Grice EA, Kong HH, Conlan S, Deming CB, Davis J, Young AC; NISC Comparative Sequencing Program, et al. Topographical and temporal diversity of the human skin microbiome. Science 2009;324:1190-2.  Back to cited text no. 6
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7.
Kloos WE, Musselwhite MS. Distribution and persistence of Staphylococcus and Micrococcus species and other aerobic bacteria on human skin. Appl Microbiol 1975;30:381-5.  Back to cited text no. 7
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8.
Otto M. Staphylococcus colonization of the skin and antimicrobial peptides. Expert Rev Dermatol 2010;5:183-95.  Back to cited text no. 8
    
9.
Wertheim HF, Melles DC, Vos MC, van Leeuwen W, van Belkum A, Verbrugh HA, et al. The role of nasal carriage in Staphylococcus aureus infections. Lancet Infect Dis 2005;5:751-62.  Back to cited text no. 9
[PUBMED]    
10.
Williams RE. Healthy carriage of Staphylococcus aureus: Its prevalence and importance. Bacteriol Rev 1963;27:56-71.  Back to cited text no. 10
[PUBMED]    
11.
Grice EA, Kong HH, Renaud G, Young AC; NISC Comparative Sequencing Program, Bouffard GG, Blakesley RW, et al. A diversity profile of the human skin microbiota. Genome Res 2008;18:1043-50.  Back to cited text no. 11
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12.
Czekaj T, Ciszewski M, Szewczyk EM. Staphylococcus haemolyticus – An emerging threat in the twilight of the antibiotics age. Microbiology 2015;161:2061-8.  Back to cited text no. 12
[PUBMED]    



 
 
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