BIOFILM FORMATION AND ANTIBIOTICS RESISTANCE BYSTAPHYLOCOCCUS AUREUSISOLATED FROM PATIENTS IN NATIONAL ORTHOPAEDIC HOSPITAL, DALA, KANO, NIGERIA
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Date
2020-01-16
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Ahmadu Bello University Zaria
Abstract
Staphylococcus aureus is a Gram-positive pathogens causing a wide range of health-care
and community acquired infections. Its ability to form small-colony variants (SCV),
biofilm and acquire resistant genes have resulted in its persistence in patients and also
putting health-care workers at risk. This study evaluated the antibiotic resistance profile and
biofilm forming capacity of S. aureus isolated from clinical samples of hospitalized patients
in National Orthopaedic Hospital Dala (NOHD), Kano, Nigeria. A total of 189 samples
consisting of 49 wound swabs, 49 nasal swab, 49 bed swab and 42 urine samples were
collected over a period of 3 months. These samples were cultured on mannitol salt agar
(MSA) and the isolates were subjected to Gram staining, catalase test, and coagulase test.
And the coagulase positive isolates were further screened using Staphylococcal Microgen
identification kit to identify S. aureus isolates. A total of 28 S. aureus were identified from
the189 clinical samples collected. The S. aureus isolates were screened for small-colony
variants (SCVs) by culturing the isolates on Columbia blood agar (CBA) to detect pin-point
or tiny colonies that are non-haemolytic and non-pigmented and they were evaluated for
biofilm-formation using the microtiter plate (MTP) method. Also, antibiotics susceptibility
pattern and inducible clindamycin (D-test) resistance of the S. aureus isolates were
determined using the agar disc diffusion method. Molecular analysis of the isolates was
done to determine the presence of biofilm associated genes (icaA and bbp) and antibiotics
resistance genes (mecA and vanA) in the S. aureus isolates using polymerase chain reaction
(PCR) to amplify the genes if present. Of the 189 samples collected, 28 (14.3%) were
confirmed to be S. aureus. Biofilm production was observed in 27 (96.4%) of the S. aureus
isolates with 1 (3.6%) S aureus isolate as non-biofilm producer. From the biofilm
producers, 3 (10.7%) of the biofilm-producing isolates were strong biofilm-formers, 6(21.4%) were moderate biofilm-formers and 18 (64.3%) were weak biofilm-formers.
Antibiotics susceptibility showed that the S. aureus isolates were generally resistant to
Amoxicillin-Clavulanic (67.9%), Tetracycline (67.9%), Ciprofloxacin (67.9%),
Norfloxacin (64.3%), Cefoxitin (67.9%), Clindamycin (57.1%) and Gentamicin (53.6%).
But they were significantly susceptibility to Linezolid (85.7%), Mupirocin (64.3%),
Erythromycin (53.6%), Trimethoprim-Sulfamethoxazole (57.1%) and Quinipristin-
Dalfopristin (60.7%). High percentage (85.7%) of the S. aureus isolates had MAR index˃
0.2, and 85.7% of the isolates were multi-drug resistant (MDR) also. A total of 2 (7.1%) S.
aureus isolates tested positive for inducible clindamycin resistance and 57.1% showed
constitutive clindamycin resistance. The high-level mupirocin resistance was found in
21.4% of the isolates while the low-level mupirocin resistance was found in 25% of the
isolates. Molecular analysis of these isolates showed that 30% harboured icaA gene that
was amplified at 188bp, 37.5% harboured bbp gene that was amplified at 500bp, 33.3%
harboured mecA gene that was amplified at 533bp and 20% harboured VanA gene that was
amplified at 1030bp.