الفهرس 
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Abstract
Microbiological contamination of water in DUWLs creates a risk of cross-infections, and is a source of biological risk factors in the work environment of a dentist. Bacterial cells accumulating and growing on the inner surface of the tubing as a biofilm are responsible for the high levels of contamination of DUWLs output water. Interest in and concern about the biofilms that occur in DUWLs have been increasing in recent years. DU devices are not sterile and has been shown to contain relatively high numbers of bacteria. The range of microorganisms isolated includes both environmental organisms, opportunistic and true human pathogens as P. aeruginosa, L. pneumophila, Mycobacterium spp., and Staphylococcus spp. Staphylococci have the ability to form biofilm which increases the resistance of these bacteria and protect them from disinfectants, antibiotics, and other environmental stresses. It has been reported that S. aureus and CoNS would contain the intercellular adhesion ica operon responsible for slime production. This operon contains the icaADBC genes, in addition to the icaR gene which exerts a regulatory function.
This study aimed to detect biofilm formation and investigate the presence of icaADBC genes in Staphylococcus spp. isolated from DUWLs.
This cross-sectional study was carried out during a 7-month period, from May to November 2017. A total of 190 water samples (100 ml) each were collected randomly from six dental care clinics at the ADRC during the three different working shifts (9am, 11am, 1pm) as follows:
a) High-speed handpiece outlets (68 samples(.
b) Air/water syringe outlets (69 samples).
c) Cup filler outlets (53 samples).
All samples were transferred without delay to the microbiology laboratory at HIPH in an ice box and processed within 1-2 hours of collection. The collected samples were subjected to isolation and identification of Staphylococcus spp. using MF technique, determination of the antimicrobial susceptibility patterns of S. aureus and CoNS isolates using single disk diffusion method according to recommendations of the CLSI, detection of biofilm production ability of the isolated Staphylococcus spp. using MTP method, and the detection of icaADBC genes involved in biofilm formation using the multiplex PCR technique.
The results of this study can be summarized as follows:
1. Of the 190 examined water samples, 34 (17.8%) samples were unacceptable regarding Staphylococcus spp.; where 55 isolates were identified; six were S. aureus and 49 were CoNS.
2. The majority of water samples; 185 out of 190 (97.4%) were acceptable for S. aureus compared to only 5 (2.6%) unacceptable samples.
3. The majority of water samples; 161 out of 190 (84.7%) were acceptable for CoNS compared to 29 (15.3%) unacceptable samples.
4. A higher level of contamination with S. aureus from the high-speed handpiece water samples was detected than those from the air/water syringe (4.4% and 2.9%, respectively).
5. The high-speed handpiece water samples showed a significantly higher level of contamination with CoNS than those from air/water syringe and cup filler samples (26.5%, 11.6% and 5.7%, respectively).
6. The five unacceptable water samples regarding S. aureus were distributed as two (6.7%), two (1.9%) and one (1.9%) from each of the samples collected at 9am,11am, and one pm, respectively, showing no significant difference (p=0.29).
7. The 29 unacceptable samples regarding CoNS were distributed as 5 (16.6%), 9 (17.0%) and15 (14.0%) from each of the samples collected at 9am,11am, and one pm, respectively. The difference between these figures was found to be not statistically significant (p=0.863).
8. The pediatrics, the conservative-treatment and the surgeries dental clinics yielded S. aureus isolates, representing 5.6%, 5.6% and 1.6%, respectively, while all the other clinics did not yield any S. aureus isolates.
9. The 29 unacceptable water samples regarding CoNS were from endodontic, pediatric, prosthodontics, conservative and surgeries, representing 25.0%, 20.4%, 19.4%, 16.7% and 7.8%, respectively
10. Three out of the six isolated S. aureus (50.0%) were recognized as MRSA and 16 out of the 49 isolated CoNS (32.6) were recognized as MRCoNS, and they all showed resistance to multiple antibiotics.
11. All the six S. aureus isolates (100.0%) had the ability to form biofilm with different intensities; four (66.6%) of these isolates were strong biofilm producers, one (16.7%) was moderate and one (16.7%) was a weak biofilm producer, while for the 49 CoNS; 10 were strong biofilm producers, 24 were moderate, 10 were weak and five were non-biofilm producers.
12. All the three MRSA isolates (100.0%) were biofilm producers; two (66.7%) were strong biofilm producers and one (33.3%) was moderate. Out of the 16 MRCoNS isolates, 15 (93.7%) were biofilm producers with different intensities; where 10 (62.5%) were moderate biofilm producers, two (12.5%) were strong producers, and three (18.8%) were weak producers.
13. Forty four (80.0%) out of the 55 staphylococcal isolates were harboring one or more of the ica genes; 21 isolates carried only one single gene, 14 isolates carried two mixed genes, 9 isolates carried three mixed genes. None of the isolates harbored all the four mixed icaADBC genes.
It can be concluded from this study that:
1. The majority of the examined DUW samples were acceptable regarding Staphylococcus spp.
2. CoNS were the most frequently encountered staphylococcal isolates.
3. The high-speed handpiece water samples showed a significantly higher level of contamination than those of air/water syringe, and water cup filler regarding CoNS.
4. The majority of the isolated staphylococcal spp. were biofilm producers with varying intensities.
5. The majority of CoNS isolates were moderate biofilm producers.
6. Most of the staphylococcal isolates were ica operon positive.
7. The presence of the icaADBC genes was not always associated with in-vitro formation of a biofilm. (75.0% agreement)
from the results of this study, the following are recommended:
1. Regular monitoring of the microbiological quality of DUW should be conducted to help ensure its safety and compliance with standards.
2. Further studies are needed to evaluate the sources of CoNS in dental clinics to limit the transmission of infection
3. Further genetic researches of ica independent biofilm formation mechanisms are required.