Characterization of bacteria isolates colonizing the throat of hospitalized patients at Sobi Specialist Hospital, Ilorin, Nigeria and <i>in vitro</i> antimicrobial effects of <i>Citrus aurantifolia</i> and Alum on the isolates

Abstract

Background: Antibiotic resistance in microorganisms implicated in nosocomial respiratory infections is a major reason for prolonged hospital stay and increased cost of therapeutic treatment of hospital acquired pneumonia (HAP). This study was designed to isolate bacterial pathogens  colonizing the throat of hospitalized patients at the Sobi Specialist Hospital, Ilorin, and to evaluate antibacterial effects of extracts of Citrus  aurantifolia peel and Alum against these bacterial isolates.

Methodology: This was a cross sectional study of 100 randomly recruited hospitalized patients at the Sobi Specialist Hospital, Ilorin, Nigeria. Throat  samples collected from consenting participants were cultured on selective agar media (MacConkey, Eosin-Methylene blue and Mannitol salt) for  isolation of bacteria. Identification of isolates from culture plates was done by Gram reaction and conventional biochemical tests while confirmation  of the isolates was done by the polymerase chain reaction (PCR) assay. Antibiotic susceptibility test for each isolate to selected antibiotics (ampicillin,  amoxicillin-clavulanate, cefuroxime, ceftazidime, gentamicin, nitrofuran, ofloxacin and ciprofloxacin) was done by the Kirby Buer disc  diffusion method. Aqueous extract of Alum ([KAl(SO₄).12H₂O]) was done to produce concentrations of 10, 20, 30, 40 and 50% (w/v) at pH 3.6 and  tested on the bacterial isolates using agar diffusion method. Citrus aurantifolia peel was extracted using methanol and hexane solvents to produce  extract concentrations of 500mg/ml, 250mg/ml and 150mg/ml, and tested on the isolates by agar diffusion, and by the broth dilution method to  obtain minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) of C. aurantifolia.

Results: A total of 14 bacterial isolates were recovered from throat samples of 100 hospitalized patients with Staphylococcus aureus (43%, n=6) being  the most frequent while Escherichia coli (14.5%, n=2) was the least frequent. The isolates were generally resistant to penicillin, aminoglycoside and  fluoroquinolone groups of antibiotics tested. The zone of inhibition for hexane and methanol extracts of C. aurantifolia and aqueous extract of alum  on the bacterial isolates ranged from 11.5-19.2mm, 9.8-15.8mm, and 9.3-21.2mm respectively while those of selected antibiotics ranged from  7.0-25.0mm. The MICs of hexane and methanol extracts of C. aurantifolia against S. aureus were 10mg/ml and 25mg/ml, while the MBCs were 50  and 100mg/ml respectively.

Conclusion: Findings from this study showed the presence of resistant pathogenic bacteria colonizing the throat of hospitalized patients receiving care at the Sobi Specialist Hospital, Ilorin, Nigeria. The crude extracts of C. aurantifolia and Alum in this study showed inhibitory effects (albeit at  higher concentrations) on the bacterial isolates comparable to the standard antibiotics. We posit that based on the inhibition capacity, further  studies to characterize, purify and isolate the active anti-bacterial components in the extracts should be considered for novelty.