Nasal Carriage Of Staphylococcus Aureus In
Healthy Blood Donors: Demographic Pro le, Risk Factors And Antimicrobial Susceptibility Testing In The Wilaya Of Tizi-ouzou, Algeria.
1 2 3 6
T.DJERBOUA , S.AZRARAK , J.FILALI , O.BECHIRI
SIGNIFICANCE OF WORK: this work is by far one of the rarest if not the sole , that address epidemiology of nasal carriage of Staphylococcus aureus in healthy people and the antibiotic susceptibility pro les in the community setting in Algeria since most studies are carried out my clinical microbiologists receiving pathological samples from infected patients. In this study we did meet with selected healthy people and sampled them in search for Staphylococcus aureus in search of risk factors proper to the geographic and demographic context of this particular region. With a humble yet acceptable number of isolates (35 cases out of 93 people sampled), Results should provide scientists with enough data to compare with and should be used as a primer for further researches on this germ.
ABSTRACT:
BACKGROUND: nasal carriage of Staphylococcus aureus is central in the epidemiology and pathogenesis of staphylococcal infec tions, never theless, ver y few publications are made on this subject especially in the community setting and on healthy people in Algeria.
OBJECTIVES: This study aims to put light on the status of healthy people towards S.aureus carriage and the circumstances around it, also we aim to determine the antimicrobial susceptibility pro le of the isolated stains METHOD: nasal swabbing was performs of healthy blood donors at Nedir Mohammed blood transfusion unit. Samples were enriched on Brain heart broth then isolated on Chapman plate. Identi cation was based on Mannitol fermentation and Coagulase test. Antimicrobial susceptibility testing (AST ) was performed according to Algerian antimicrobial resistance network recommendations inspired
from both CLSI and EUCAST AST guidelines.
RESULTS:
a total 93 healthy blood donors accepted to participate, mainly men (N=77), the mean age was of 29 years old. Most of them had an occupation (91.43) and reported having one or more risk factors for S.aureus nasal carriage.35 of the participants were carriers of S.aureus mainly men (85.71). 19 of these isolates (54%) were MRSA. Our strains whether MRSA or MSSA showed few resistance to other antibiotics.
CONCLUSION:
our results show that Staphylococcus aureus nasal carriage is widely distributed among healthy people and MRSA might be more spread than expected. Further studies including the determination of molecular resistance markers on a larger recruitment should allow a more precise determination of the rates of nasal carriage in healthy people and the impact on Staphylococcal infection epidemiology in our region
.
Introduction:
Staphylococcus aureus (S.aureus) are Gram positive cocci widely distributed in nature. In human being, the main ecological niche is the anterior nostrils.
t h e M e d i t e r r a n e a n re g i o n i n c l u d i n g A l g e r i a a re hyperendemic areas for S.aureus especially with MRSA strains and this trend seems increasing quickly(1)
Nasal carriage of is proven to play a key role in epidemiology and pathogenesis of S.aureus infections. Colonization rates vary widely from a country to another, inside the same country and in same individual since this carriage can be persistent or intermittent (1, 2)
Clinical biology laboratory, Belloua Unit Nedir Mohamed university. Tizi ouzou, Algeria
Article Original: Biologie
Many risk factors were identi ed to be determinants of S.aureus carriage like crowding and healthcare exposure –(3) further risk factors were identi ed to promote MRSA carriage including advanced age, chronic diseases, immunosuppression, antibiotic intake and hospitalization antecedents (4, 5).
This study aims to put light on the status of healthy people towards S.aureus carriage and the circumstances around it, also we aim to determine the antimicrobial susceptibility pro le of the isolated stains.
Material and method
Samples were collected form people eligible for blood donation at the center of blood transfusion in Nedir Mohammed hospital, Tizi-ouzou. Being eligible for blood donation implies that the subject is in good health(6).a fact sheet was established to search for risk factors of S.aureus and specially MRSA carriage Participation to the study was with the donor's oral consent, anonymity was . respected.
The sampling consisted of a nasal swab of both nostrils that was immediately put in a nutrient broth and incubated for 24h.the enrichment broth was subcultured onto Chapman agar and incubated in ordinary atmosphere at 37°C for 24h.Identi cation of S.aureus was performed on Mannitol positive colonies using Coagulase test.
In order to get a view of antibiotic sensitivity of the initial population of S.aureus present in the sample, we did isolate as many colonies as possible from the initial agar onto another Chapman plate in the form of spots.
Antibiotic susceptibility testing (AST) was performed following the recommendation of the “Standardization of antibiotic testing on the national scale, 7 Edition”, published by the Algerian antibiotic resistance network (AARN) .This document is inspired from th
Clinical laboratory standards institute (CLSI) and European committee on antimicrobial susceptibility testing (EUCAST) recommendations (7)
Bacterial suspension was prepared using several colonies and then diluted to meet the 0.5 McFarland turbidity.
AST method include disk diffusion on Muller-Hinton agar for Penicillin G, Cefoxitin (MRSA detection), Gentamicin, Amikacin, Kanamycin, Erythromycin, Clindamycin, Pristinamycin, O oxacin, Cipro oxacin, Levo oxacin, Chloramphenicol, Teicoplanin, Rifampicin, Co-trimoxazol, Tetracyclin, Fusidic acid.
MIC determination for Vancomycin and Fosfomycin was performed using Broth micro dilution (BMD), but due to lack of reagents, tests we used Brain-Hearth infusion broth (BHIB) as testing medium and Medicine powder, Monuril® (sachets containing 3g of Fosfomycin-tromethamin granules for oral solution) for and Vancomycin Mylan ® (500mg powder for solution for infusion) Quality controls for disk diffusion and Vancomycin MIC BMD were performed using Staphylococcus aureus ATCC 25923, those for Fosfomycin-Tromethamin MIC BMD were performed on Staphylococcus aureus ATCC 25923, Escherichia coli 25922 and Pseudomonas aeruginosa ATCC 27853
Data was saved and analyzed using Whonet 5.6 software and Microsoft Excel 2013.
RESULTS:
93 people accepted to participate in this study, the middle age was of 29 years old. Data gathered with the fact sheet are exposed in the Table 1
S.aureus positive culture rates are of 37% (35 people). The main results concerning carriers of S.aureus summarized in gure 2
Table 2: rates of carriage of Staphylococcus aureus in terms of demographic pro le and risk factors (N=35)
1: were calculated from a total of 35 carriers of S.aureus
2: were calculated from the total number of people who responded to the given criterion, for example the ratio for students (0.83), 10 were carriers and 12 non carriers.
3: the carriage rate reported refers to people who responded “yes” in “crowded environment” (N=55), they mainly lived in a university campus (N=40) with a C/NC carrier ratio of 0.81, in contrast, those who responded “no” (N=38) have a carriage rate of 22% and a C/NC ratio of 0.40 4: people who reported having a cat or a dog (N=19) had a C/NC ratio of 0.90, those who reported being in contact with cattle (N=22) had a C/NC ratio of 0.46
5: among people who reported an antecedent of hospitalization, 45.7 were carriers, those who were under medical supervision had an N/NC ratio of 0.90 while those who were hospitalized for a surgical intervention had a C/NC ratio of 1
We also noticed that, C/NC ratio increased when the number of associated risk factor, it ranges from 0.40 for no risk factor to 1.12 for three associated risk factors (for example living in crowded environments plus owning a domestic pet and having an antecedent of hospitalization). For four associated risk factors C/NC ratio was of 2.
In terms of antibiotic sensitivity results, 54% of isolates were MRSA (N=19). Compared to the total study population (N=93), carriage rates are 17% MSSA and 20% MRSA. rates of MRSA isolation also increased with age , MSSA/MRSA ratio of 1.43 for the [21-28[years of age class versus 0.60 for the [35-42[ class. the main results correlated to demographic pro le and risk factors are summarized in table 3 and AST results to the panel tested are reported in gure 1
Table 3: demographic pro le and risk factors of MRSA carriers (N=19)
1: S.aureus Carriers (N=35) who responded “yes” in “crowded environment” (N=27) had more MRSA (15 MRSA out of strains).
2: S.aureus Carriers who reported having an animal contact (N=16) had more MRSA (12 MRSA) than those who have not (N=19, 7 MRSA)
3: S.aureus Carriers who reported a hospitalization antecedent (N=16) had more MRSA isolates if they had a surgery undertaken (N=9, 6 MRSA) in contrast to a medical supervision (N=7, 3 MRSA) 4: S.aureus Carriers reporting “yes” to recent antibiotic intake (N=8) had higher MRSA isolates (6 MRSA) those who said “no” (N=27) had more MSSA isolated (14 MSSA)
DISCUSSION:
Staphylococcus aureus is an important human pathogen he is involved in community and hospital infections with high morbidity and mortality and considerable impact on healthcare costs.(8)
Studies nasal carriage of S.aureus are very rare, in fact a PubMed research with keywords “Staphylococcus aureus, community, nasal and Algeria” only yielded one result
In this study, nearly one man out of four was a Staphylococcus aureus carrier. Many published studies highlighted the fact that men were more often carriers then woman (9, 10), the studies emphasize on the fact that women were more respectful of their global hygiene and hand washing than their male counterparts.
Furthermore, the role of particular occupation as a risk factor of nasal carriage of S.aureus like contact with raw meant, livestock, healthcare professionals…(11, 12) is a well established fact. In our study, it is hard to establish the link between a given occupation and the carriage risk since the number of participants in this study is limited.
We could however suspect that life with a heterogeneous group of people (crowded environment) at work or life in a university campus could constitute a risk factor since this notion was found in 77% of S.aureus carriers in our study.(13-15)
Also, working with livestock and having a pet like cats and dogs may constitute a risk factor since this ubiquitous germ can be easily transmitted from humans to animals and vice versa. In our study nearly half of the carriers had a pet or was in contact with cattle (16, 17).
Hospitalization antecedents and antibiotic intake are risk factors for MRSA carriage (18) in our study, the number of people carrying MRSA were more important in they undergone surgery or taken an antibiotic, but this data need further enrichment.
The overall carriage rates of S.aureus and MSSA/MRSA rates are higher than those reported by Djoudi et al thus higher than the countries compared in Djoudi et al study but as reported, data of nasal carriage in the same country may vary wildly from a region to another. Comparison of the main results of the two studies are summarized in table 4 (19).This comparison is though hard to make since the context of the two studies are totally different i.e. our study was totally dedicated to healthy people.
Table 4: comparison of Staphylococcus aureus carrier data in our study with Djoudi and al study
In matter of antibiotic sensitivity profiles, in the absence of similar studies, we compared our results to those reported by the Algerian antimicrobial resistance network (AARN) (20). We found that rates of MRSA isolates were higher than those reported by AARN (54% versus 23, 75% for outpatient and 34.89% for global S.aureus strains inventoried by AARN).for the rest of antibiotics tested for S.aureus, our rates were lower than those reported by AARN for outpatient and global data (Figure 2).
The differences between our study and those of Djoudi et al and AARN report might be due to the fact that data collected by AARN results from clinical strains and not from carriage strains, it might also be due to our recruitment (N=93) in comparison of Djoudi et al (N=507) and AARN.
Figure 2: compared resistance rates among S.aureus strains in our study and AARN data
LIMITS OF THE STUDY:
we encountered many barriers to achieve this modest work mainly the insufficient number of participants, many people refused to be sampled, we encountered also issues related to the collection of information from reluctant participants and technical issues mainly none availability of AST products and the absence of molecular tools.
CONCLUSION
Our data gives a small view of Staphylococcus aureus nasal carriage in healthy people in the 4 biggest Wilaya of Algeria, th
shows that S.aureus generally and MRSA carriage specially might be more spread then expected. Through this study we hope to be the primer for other more extensive researches dedicated to the community setting including analysis at the molecular scale whom are important in the global effort of
ghting drug resistant bacteria.
Acknowledgements:
We are grateful to Doctor Sellam, chief of staff of the blood transfusion unit at Nedir Mohammed University hospital for granting us access to the blood donors.
https://www.cdc.gov/niosh/docs/2013-112/pdfs/2013- 112.pdf
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