BACKGROUUND:
Staphylococcus aureus infection is associated with hospital and infections which arise from the community. The emergence of resistance to most antimicrobial agents in Staphylococci indicates the need for new effective agents in the treatment of Staphylococcal infection. Among the alternatives available Clindamycin is considered to be safe, effective and less costly agent. In vitro routine tests for Clindamycin susceptibility may fail to detect inducible Clindamycin resistance due to erm genes, resulting in treatment failure, thus necessitating the need to detect such resistance by a simple D-test on routine basis.
AIM OF THE STUDY:
The present study is aimed to detect erm gene in inducible Clindamycin resistant Staphylococcal isolates and to study the relationship between Clindamycin and Methicillin resistance.
MATERIALS AND METHODS:
During the study period a total of 100 non duplicate clinical isolates of Staphylococci were collected from different clinical samples like aural swabs, wound swabs, pus and vaginal swabs from both in-patient and out-patient departments of Tirunelveli Medical College The Staphylococcal species were identified by standard biochemical techniques.and their antibiotic susceptibility tested by standard disk diffusion method on Muller Hinton agar [MHA] according to the standards of clinical and laboratory standards institute[CLSI]. Detection of inducible Clindamycin resistence was performed by D-test on a Mueller Hinton agar plate with a lawn culture of the isolate which was adjusted to 0.5 Mcfarland’s concentration . Discs of Clindamycin(2μg),Erythromycin(15μg) were kept at a distance of 15mm. The disc diffusion D test, showed
1. Inducible MLSB phenotype (iMLSB),
2. Constitutive MLSB phenotype (cMLSB),
3. MS phenotype.
The Staphylococcal isolates from MLSBi were further tested by Real-Time PCR for ermA/ermB/ermC genes.
RESULTS:
In this study among the 100 Staphylococcal isolates 80% were Staphylococcus aureus and rest 20% were coagulase negative staphylococcus. Out of strains isolated 80% were from hospitalized patients . The study group contained 55% males and 45% females and Male to female sex ratio was 1.2 2:1. Majority of the study group were found among the age group 21-30 yrs.
Majority of the Staphylococcal aureus 75% and CONS 100% were isolated from pus and majority of the MSSA 76.36% and 72% MRSA were also from pus. Inducible MLSB resistance was detected by Disc diffusion test (D-test).
In D-test the phenotypic distribution of iMLSB, cMLSB and MS were 35%, 12.5% and 52.5% respectively. In the phenotypic distribution of iMLSB Staphylococcus .aureus was 37.5% and CONS 25%, MSSA 31.58% and MRSA 46.15%.
Majority of the iMLSB was susceptible to Ciprofloxacin, Cotrimoxazole and Gentamycin. while cMLSB and MS phenotype were resistant to ciprofloxacin when compaired to iMLSB .There was high rate of resistance exhibited by cMLSB towards Cefoxitin when compaired to iMLSB. No resistance was observed to vancomycin.
Genetic analysis by real time PCR performed on iMLSB showed 21.42% erm A,7.14% erm B,14.3% erm C,50% erm A and erm C and 7.14% erm B and erm C.
CONCLUSION:
In this present study D-test is easy to perform and found inexpensive for practical purpose than PCR which is the gold standard. This test is used to detect an inducible Clindamycin resistance in staphylococci as a routine work in clinical microbiology laboratories. This test help us to provide confident laboratory reports and Clindamycin can be omitted in patients with infections caused by inducible Clindamycin resistance staphylococci, and therapeutic failures may be thus avoided
