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. 2017 Aug 31;12(8):e0184172.
doi: 10.1371/journal.pone.0184172. eCollection 2017.

Biofilm Formation of Methicillin-Resistant Coagulase Negative Staphylococci (MR-CoNS) Isolated From Community and Hospital Environments

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Free PMC article

Biofilm Formation of Methicillin-Resistant Coagulase Negative Staphylococci (MR-CoNS) Isolated From Community and Hospital Environments

Rathanin Seng et al. PLoS One. .
Free PMC article

Abstract

Methicillin-resistant coagulase negative staphylococci (MR-CoNS) are the major cause of infectious diseases because of their potential ability to form biofilm and colonize the community or hospital environments. This study was designed to investigate the biofilm producing ability, and the presence of mecA, icaAD, bap and fnbA genes in MR-CoNS isolates. The MR-CoNS used in this study were isolated from various samples of community environment and five wards of hospital environments, using mannitol salt agar (MSA) supplemented with 4 μg/ml of oxacillin. The specie level of Staphylococcus haemolyticus, Staphylococcus epidermidis, Staphylococcus hominis and Staphylococcus warneri was identified by specific primers of groESL (S. haemolyticus), rdr (S. epidermidis) and nuc (S. hominis and S. warneri). The remainder isolates were identified by tuf gene sequencing. Biofilm production was determined using Congo red agar (CRA) and Microtiter plate (MTP) assay. The mecA and biofilm associated genes (icaAD, fnbA and bap) were detected using PCR method. From the 558 samples from community and hospital environments, 292 MR-CoNS were isolated (41 from community environments, and 251 from hospital environments). S. haemolyticus (41.1%) and S. epidermidis (30.1%) were the predominant species in this study. Biofilm production was detected in 265 (90.7%) isolates by CRA, and 260 (88.6%) isolates were detected by MTP assay. The staphylococci isolates derived from hospital environments were more associated with biofilm production than the community-derived isolates. Overall, the icaAD and bap genes were detected in 74 (29.5%) and 14 (5.6%) of all isolates from hospital environments. When tested by MTP, the icaAD gene from hospital environment isolates was associated with biofilm biomass. No association was found between bap gene and biofilm formation. The MR-CoNS isolates obtained from community environments did not harbor the icaAD and bap genes. Conversely, fnbA gene presented in MR-CoNS isolated from both community and hospital environments. The high prevalence of biofilm producing MR-CoNS strains demonstrated in this study indicates the persisting ability in environments, and is useful in developing prevention strategies countering the spread of MR-CoNS.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Biofilm producing ability of MR-CoNS obtained from community and hospital environments.
(A) (B) (C) (D) and (E) Two group comparisons of median OD570 were analyzed by using Mann–Whitney U-tests (P-values < 0.05 indicate the statistical differences). (A) The comparison of OD570 among S. epidermidis, S. haemolyticus and other staphylococcal species. (B) (C) (D) and (E) the comparison of OD570 of MR-CoNS species between community and hospital isolates. Species distribution in other species were S. capitis, S. warneri, S. cohnii, S. pasteuri, S. caprae, S. hominis, S. saprophyticus, S. nepalensis and Staphylococcus spp.
Fig 2
Fig 2. Comparisons of biofilm forming ability between the present and absent of each virulence genes.
(A) (B) (C) (D) P- values represent the comparisons of median OD570 between two groups of MR-CoNS (Mann–Whitney U-tests, P < 0.0). Species distribution in other species were S. capitis, S. warneri, S. cohnii, S. pasteuri, S. caprae, S. hominis, S. saprophyticus, S. nepalensis and Staphylococcus spp.

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Grant support

This study was funded by Office of the Higher Education Thailand (HERP 2559) (R2559A006) to SS. RS was supported by the Royal Scholarship under Her Royal Highness Princess Maha Chakri Sirindhorn, 2015 of Naresuan University. RT was supported by The Royal Golden Jubilee Ph.D. Program (PHD/0031/2558).
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