T.A. Ajani1, C.J. Elikwu2, C.G. Anaedobe3, C.N. Onwuzo2, B. Tayo2, C.C. Okangba2, O.B. Makanjuola1,4

  1. Department of Medical Microbiology and Parasitology, University College Hospital, Ibadan, Nigeria.
  2. Department of Medical Microbiology, Benjamin Carson (Snr) College of Health and Medical Sciences, Babcock University, Ilisan Remo, Nigeria.
  3. Department of Medical Microbiology and Parasitology, College of Health Sciences, University of Abuja,
  4. Department of Medical Microbiology and Parasitology, University of Ibadan, Ibadan, Nigeria.


Background: Molecular diagnosis though faster and more sensitive than phenotypic techniques, is more expensive. Resource limited settings are thus limited to using more of phenotypic rather than molecular methods in the routine detection of Extended Spectrum beta lactamases (ESBL)

Aim: This study aimed to evaluate the performance of double disc synergy test (DSST) and Epsilometer (E) test with Polymerase Chain Reaction (PCR) and to detect the risk factors associated with ESBL producing organisms among in-patients at Babcock University Teaching Hospital, Ilishan-Remo, Nigeria.

Methodology: Hospital-based cross-sectional study in which bacterial isolates of 165 in-patients were collected fromMarch 2018 to September 2019. The isolates were evaluated for ESBL production by the use of DDST, Etest and PCR. The performance evaluation was done. Questionnaire was used to assess the risk factors associated with ESBL, IBM SPSS Version 23
was used to analyze the data.

Results: The participants’ isolates yielded 50/165 (30.3%) that were ESBL positive by DDST, 47/165 (28.9%) by E-test and 48/165(29.1%) by PCR. Sensitivity and specificity of DSST was 100% and 98.3% while that of E-test was 98% and 100% respectively. Age, antibiotics intake without prescription, being on ventilator, urethral catheterization and nasogastric tubes were all significantly associated with presence of ESBL (p value <0.05).

Conclusion: Phenotypic tests remain reliable for the routine detection of ESBL in the absence of molecular methods. Rational use of instrumentation and antibiotics is advocated based on the risk factors detected from this study

Keywords: Double disc synergy test, Epsilometer test, Polymerase Chain Reaction (PCR), Extended spectrum beta lactamases.


Dr T.A. Ajani
Dept. of Medical Micro. and Parasitology,
University College Hospital,
Ibadan, Oyo State,
Email: solamustoo@yahoo.com
Date of Acceptance: 31st Dec., 2022


The continued increase in the prevalence of multi-drug resistant organisms (MDRO) is a known cause of therapeutic failures clinically and this has become a major global concern.1,2 Among the MDRO, of most importance are Gram-negative bacilli producing Extended Spectrum beta lactamases (ESBL). These organisms cause a large proportion of infections both in the hospital and community but are resistant to most common treatment options including Beta lactam antibiotics.3-5 Therefore resistance of Gram-negative bacilli to these antibiotics is a public health concern because of limited therapeutic options in infected patients.1

ESBL hydrolyzes penicillin, narrow- and extendedspectrum cephalosporins and aztreonam but they are inhibited by beta lactam inhibitors.5-7 Also, the presence of ESBL in a bacterium can confer resistance to trimethoprim-sulphamethoxazole, aminoglycosides and quinolones because the plasmids carrying ESBL genes are also known to carry resistance genes that encode for resistance to other antibiotics.5-7 The high transferability of plasmids carrying ESBL genes has increased the risk of resistance transmission in hospital infections leading to prolonged hospital stay, increased medical bills and adverse disease outcomes in patients. All these have made ESBL a serious threat globally.3,7-8

ESBLs are prevalent worldwide and the prevalence has continued to escalate over the years.2,8 In 2017, the Centers for Disease Control and Prevention (CDC) estimated that among hospitalized patients, there were 197,400 cases of ESBL producing enterobacteriaceae and 9,100 estimated deaths in the United States alone.9 In Chitwan, South Asia, the prevalence of ESBL was reported to be 64% while in Pakistan the prevalence of ESBL has been increasing over the last decade and is reported to be 79%.1,10 In Sub-Saharan Africa, ESBL has been reported to be a major public health threat with a prevalence of 62.3% in Mali and 64.3% in Sierra Leone.11 In Nigeria, the prevalence of ESBL varies from 23.6% in Maiduguri, 11.4% in Enugu to 51.3% in Ile-Ife.12-14

Laboratory methods for the detection of ESBL include the phenotypic and molecular methods.15 Phenotypic methods include the use of double disc synergy test (DDST), Epsilometer (E test) and Combination disc method which are based on the inhibitory activities of beta-lactamase inhibitors.3,15-16 These methods are the preferred options in the routine medical microbiology laboratory because of the cheaper cost.3 However, these methods have longer turnaround time, depending on bacterial growth, the results are subjective and there may be the issue of false positivity or false negativity if the ESBLproducing bacteria coexpress AmpC type -lactamase (ACBL).17,18

Molecular diagnosis is faster, more accurate and more sensitive than phenotypic techniques thereby improving treatment outcomes in patients and is also useful in supplying epidemiological data.17,19 Recently, the Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) reduced the susceptibility breakpoints of Cephalosporins therefore making the of use phenotypic ESBL tests routinely unnecessary.3,16 However, considering the lack of precision that might accompany antimicrobial susceptibility test and also that in-vitro susceptibility may not translate to clinical success in the therapeutic management of patient, confirmatory phenotypic ESBL tests might still be necessary routinely.3,20 Though rapid and accurate detection of ESBL is needed for appropriate essential antibiotic treatment and infection control activities and the molecular or automated methods fit perfectly for this, however, they are more costly and need trained personnel. Therefore, most laboratories in developing countries cannot afford to employ these methods.21 This leaves us with the option of using more phenotypic methods than automated or molecular methods in the detection of ESBL. Therefore, it is important to carry out performance evaluation of phenotypic methods as against the molecular methods in our environment. Thus the objective of this study was to evaluate the performance of the double disc synergy test and Etest by comparing with PCR and also to detect the risk factors associated with ESBL among in patients in Babcock University Teaching Hospital, Ilishan-Remo, Nigeria.