ANTIBIOTICS SUSCEPTIBILITY AND MOLECULAR CHARACTERIZATION OF CLINICAL ISOLATES OF E. coli FROM AHMADU BELLO UNIVERSITY TEACHING HOSPITAL SHIKA, ZARIA
ANTIBIOTICS SUSCEPTIBILITY AND MOLECULAR CHARACTERIZATION OF CLINICAL ISOLATES OF E. coli FROM AHMADU BELLO UNIVERSITY TEACHING HOSPITAL SHIKA, ZARIA
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Date
2011-12
Authors
IGWE, James Chibueze
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Abstract
Antimicrobial drug resistance is a global challenge with the emergence of resistant bacterial
strains worldwide. This study was conducted to determine the incidence of E. coli in ABUTH
Shika, Zaria (from March 2011 to February 2012), their antibiotics susceptibility pattern,
molecular characterization and possible presence of E. coli serotype O157:H7. Clinical isolates
of E. coli from inpatients and outpatients were collected and cultured on eosin methylene blue to
obtain pure cultures. A retrospective analysis of records of the Medical Microbiology unit for the
same period (March 2011 to February 2012) was carried out. The incidence of E. coli isolates in
clinical samples was found to be 50% in stool, 26.7% in urine, 13.3% in blood, 6.6% in
urogenital and 3.3% in wounds. The retrospective analysis of the prevalence of E. coli associated
infections in ABUTH Shika, showed that out of the 751 patients bio-data evaluated, female
patients were mostly infected 62.3%(468) compared with male patients 37.4%(281). Of the 751
patients bio-data evaluated, 150 isolates were collected and 60 isolates were confirmed as E. coli.
The antibiotic susceptibility profile of clinical isolates of E. coli to fourteen (14) commonly
prescribed antibiotics in the treatment of E. coli associated infections showed that 76.7% of the
isolates were resistant to ceftazidime, 78.3% to amoxicillin-clavulanic acid, 70% to ampicillinsulbactam,
56.7% to tetracycline, 43.3% to cefalexin, 41.7% to nalidixic acid, 36.7% to
amoxicillin and 30% to cefuroxime. The isolates were also found to be sensitive to ceftriaxone
(88.3%), gentamicin (78.3%), chloramphenicol (78.3%), ciprofloxacin (71.7%), nitrofurantoin
(78.4%), ofloxacin (73.3%). Higher percentage (80%) of the isolates were multidrug resistant
(MDR), 11.7% were extensively drug resistant (XDR). Statistical analysis at p value < 0.05,
showed a significant difference in the level of resistance expressed by E. coli from different
clinical samples. At MARI ≥ 0.3, 71.6% of the patients showed a frequent use of the antibiotics
usually prescribed in the hospital for E. coli infections. The high minimum inhibitory
concentration (μg/ml) of amoxicillin–clavulanic acid and ceftriaxone to the transconjugants of
the multidrug resistant E. coli showed that the resistance exhibited was plasmid encoded. The
extended spectrum β-lactamase (ESBLs) using double disc diffusion method showed that of the
10 isolates tested, all were resistant to amoxicillin-clavulanic acid, 7(70%) to ceftazidime,
5(50%) to ceftriazone and cefpodoxime. Seventy percent 7(70%) of the 10 selected multidrug
resistant clinical isolates were ESBLs positive; a ≥ 5mm increase in zone diameter for either
antibiotics compared to its zone when tested alone, while 30% (3) of the selected isolates showed
production of AmpC gene. E. coli serotype O157:H7 was isolated in 11(18.3%) of the 60
confirmed E. coli isolates (that is, 36.7% (11) of the stool isolates (30) were E. coli serotype
O157:H7, while other serotypes in stool isolates amounted to 63.3%). Hetero-resistant isolates of
E. coli (small colonies variant, found within the diameter of the zone of inhibition of cefoxitin)
showed a far higher resistance to some tested antibiotics than that of their parental clinical
isolates. Using molecular characterization by polymerase chain reaction (PCR), the ESBLs
encoding genes, TEM, SHV and OXA and plasmid bands were detected in the multidrug
resistant isolates, and in line with documented works, this suggests that these genes were plasmid
encoded. E. coli expressing ESBLs and AmpC enzyme are present in E. coli isolated from
ABUTH, Shika, Zaria. These suggest that patients with infections associated with E. coli
producing ESBLs and AmpC enzyme may have complication in therapy and limited treatment
options, which will lead to higher mortality rate, high economic burden and longer hospital stays
Description
A THESIS SUBMITTED TO THE SCHOOL OF POST-GRADUATE STUDIES AHMADU
BELLO UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE
AWARD OF MASTER DEGREE (M.Sc.) IN PHARMACEUTICAL MICROBIOLOGY
DEPARTMENT OF PHARMACEUTICS AND PHARMACEUTICAL MICROBIOLOGY,
FACULTY OF PHARMACEUTICAL SCIENCES,
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
Keywords
ANTIBIOTICS SUSCEPTIBILITY,, MOLECULAR CHARACTERIZATION,, CLINICAL ISOLATES,, E. coli,, AHMADU BELLO UNIVERSITY TEACHING HOSPITAL SHIKA,, ZARIA.