Wound infections are responsible for significant mortality and morbidity worldwide accounting for 70-80% mortality. Methicillin-resistant S. aureus has long been recognized as an important pathogen in human disease and is the most common cause of nosocomial infections. The development of resistance against the therapeutic options for treatment of infection caused by MRSA is an emerging problem 1, 2, 6. Therefore, this study was aimed to assess the prevalence and antimicrobial susceptibility pattern of Methicillin-resistant and inducible Clindamycin resistant S. aureus among patients with an infected wound.
In the present study, the overall prevalence of S. aureus was 79(49.7%) which was in agreement with the study done in Nepal 19 and Yekatit 12 Hospital Addis Ababa, Ethiopia 20. Reports conducted in Brazil 8 and Nigeria 21 are showing higher prevalence than the present study. Our result is higher when compared with researches done abroad 22, 23-25. This differences might be due to study design, study period, and socioeconomic status of the population studied.
In this study out of 79 isolated S. aureus, 65(82.28%) were MRSA. It is comparable to studies done in Kenya accounting 87.2% 27 and in Nigeria 78% 28. However, it is higher than the research report from Jimma University specialized hospital and Debre Markos Referral Hospital, Ethiopia 20, 26 and in the inland region of northeastern Brazil, India, and Pakistan 22, 25, 27. Furthermore, different studies have depicted variations in the prevalence rates of MRSA in different countries. This might be due to the variation in the population studied, the practice of antibiotics usage, sample size, sample type, infection control practices.
This study showed that the recovery rate of MRSA was greater in male 35(53.84%), in patients with surgery 20(30.54%) followed by patients with an infection after skin abrasion 19(29.23%). Other studies were done in Jordan 29 and Uganda 19 reported the same result with the present study. This may be attributed to S. aureus is the main pathogen causing skin infections. Out of 65 MRSA isolates 30(46.23%) were recovered from patients in the age range of 15-30 years. This is in line with a study conducted in Bangalore, India 30. Patients who were hospitalized for more than 1 week harbored more MRSA isolates and those who took antibiotics previously within the last one year were found to be high and isolation of MRSA was also high. This is in agreement with research done in Ethiopia 25, Cameroon 31 and India 22. However, there was no statistically significant association between the prevalence of MRSA and associated factors. This may be due to the smaller sample size included in our study.
Since the treatment of wound infection is on an empirical basis with first line broad-spectrum antibiotics and the increase of drug resistance among pathogens causing wound infection especially S. aureus, continuously updated data on antimicrobial susceptibility patterns would be beneficial for the trend of empirical therapy. In the determination of the susceptibility of MRSA on nine (9) selected antibiotics by disk diffusion technique showed that MRSA tends to be resistant to a wider range of antibiotics.
In this study, MRSA isolates were resistance to Tetracycline (72.3%), Co-trimoxazole (43.1%), Erythromycin (32.9%). This was consistent with reports in Ethiopia 2, 32 and elsewhere 6, 33. The same isolate was highly sensitive to Amikacin (100%), Vancomycin (100%), Clindamycin (94.9%), and Gentamycin (92%) which is also in agreement with the research done in Pakistan 24, that reported 100%, 94.7%, 86.2% and 84% sensitivity to Vancomycin, Chloramphenicol, Clindamycin and Amikacin respectively. Remarkable susceptibility to Vancomycin, Amikacin and Gentamycin may be due to lesser use of these antibiotics as a result of their less availability and cost. However, higher resistance to Vancomycin and Clindamycin was reported from a study done in Nigeria 21.
In this study, Vancomycin was 100% effective against both Methicillin-resistant and sensitive S. aureus. This was not in parallel with studies conducted in Addis Ababa, Ethiopia 32, Debre Markos, Ethiopia 26 and Kumasi, Ghana 34 which reported the variable resistance of MRSA against Vancomycin.
The present study revealed that out of 79 isolated S. aureus tested for Inducible Clindamycin resistance 19 (24.1%) were positive (Erythromycin resistant, Clindamycin sensitive and D-test positive). This is comparable with a study conducted in Kenya, which showed 19 (37.2%) isolates were inducible Clindamycin resistance 35. But it is lower than a study done in India 41 (47.12%) 36.
The overall prevalence of inducible Clindamycin resistance among MRSA isolates were 16(24.6%) whereas among MSSA only three isolates were showed inducible Clindamycin resistance. This is supported by other studies as in Andhara south India 23/82(28.04%) 37. On the other hand, there were higher percentages of 19/46 (41.3%) and 16/26 (61%) of MRSA exhibiting inducible Clindamycin resistance in India and Tanzania respectively 38, 39. The remaining MRSA isolates show no resistance phenotype 46(70.8%), cMLSB 2(3.08%) and MS (D-negative) 1(1.54%). This is in agreement with research done in South India and Nepal 8, 19.
In general, it may be risky to use Clindamycin when erythromycin testing shows a resistant or intermediate even though the bacteria are sensitive to Clindamycin. For this reason, routine D-testing might help clinicians to retain confidence in using Clindamycin when erythromycin resistance is observed 40.
The prevalence of MRSA in Arba Minch General Hospital was found to be high. It is an alarming result which needs a due attention and intervention to control the spread of drug-resistant organisms. Amikacin and Vancomycin were 100% effective drugs against both MRSA and MSSA isolates. However, high level of resistance was observed to Tetracycline and Co-trimoxazole among MRSA isolates. The incidence of inducible Clindamycin resistance was found too high. This may limit the therapeutic options and may lead to treatment failure. In this case, it may be very important to evaluate the susceptibility pattern of MRSA periodically.