1 Introduction
Microorganisms are one of the major threats to mankind and microbial infections are the leading cause of motility worldwide. According to the World Health Organization (WHO), microbial infections collectively resulted in 25% of death worldwide (
WHO, 1999).
S. aureus is a Gram positive cocci commonly associated with several clinical conditions. Humans are the natural reservoir and the infection is mostly asymptomatic (
Chambers, 2001), however
S. aureus is also reported to cause the symptomatic infection of skin and soft tissues such as abscesses (boils), carbuncles, hidradenitis suppurativa, folliculitis, impetigo, furuncles, and cellulitis, sore throat. Glomerulonephritis, food poisoning, lymphadenitis, toxic shock syndrome, osteomyelitis, pneumonia, meningitis, endocarditis and bacteremia are few other complications associated with
S. aureus infections (
Bamberger and Boyd, 2005).
Generally,
S. aureus infections can be treated by the application of flucloxacillin, dicloxacillin, cephalosporins (cefazolin, cephalothin and cephalexin), clindamycin, lincomycin and erythromycin, vancomycin, teicoplanin, combination of rifampicin and fusidic acid, lincosamides (clindamycin, lincomycin) or cotrimoxazole. New antibiotics such as linezolid and quinupristin/dalfopristin can also be used but are very costly (
Rayner and Munckhof, 2005). However in last few decades, reports of microbial drug resistance in
S. aureus have been documented all around the world (
Livermore, 2000;
Bal and Gould, 2005;
Pantosti et al., 2007). Emergence of the drug resistance could be attributed to the unrestricted and overuse use of antibiotics in a particular environment. Infection with these resistant strains of
S. aureus is expected to cause more severe disease and may require longer treatment period than infection with susceptible strains.
A routine check of antibiotic sensitivity pattern could help to understand the emergence of drug resistance in microorganisms and may help in deciding the drug of choice for the treatment of infection. Therefore, the aim of the present study is to record the antibiotic sensitivity pattern of various antibiotics toward the S. aureus isolated from the clinical samples. This study also highlights the need for continuous surveillance of antibiotic sensitivity pattern of S. aureus with a view to selecting appropriate therapy.
2 Material and methods
2.1 Chemicals and media
Blood agar base, MacConkey agar, Chrom agar, Muller Hinton agar, Amikacin (AK), Amoxicillin+ clavulanic acid (AMC), Ampicillin+ sulbactam (A/S), Azithromycin (AZM), Aztreonam (AT), Cefoparazone (CPZ), Cefpodoxime (CPD), Ceftazidime (CAZ), Ceftriaxone (CTR), Cefuroxime (CXM), Ciprofloxacin (CIP), Clarithromycin (CLR), Clindamycin (CD), Cloxacillin (Cox), Doxycycline (DO), Impipenem (IPM), Levofloxacin (LE), Linezolid (LZ), Meropenem (MRP), Methicillin (MC), Moxifloxacin (MO), Ofloaxacin (OF), Pipracillin+ Tazobactum, (PIT), Teicoplanin (TEI), Vancomycin (VA) discs were purchased from Himedia Pvt Ltd, Mumbai, India. All other chemical used during the study were of analytical grade.
2.2 Antibiotic sensitivity test
2.2.1 Samples
A total of 50 isolates of S. aureus were isolated from different clinical samples, pus, throat swabs, urine and sputum on Blood agar and MacConkey agar and Chrom agar plates at Dhanwantri Hospital and Research Centre, Jaipur, Rajasthan, India during year 2013. The cultures were characterized microscopically by Gram’s staining and biochemically by catalase and coagulase test.
2.3 Assay
The 50
S. aureus cultures were screened for their sensitivity toward 25 standard antibiotics. Antibiotics included Amikacin (30 µg/disc), Amoxicillin+ clavulanic acid (AMC), Ampicillin+ sulbactam (A/S), Azithromycin (AZM), Aztreonam (AT), Cefoparazone (CPZ), Cefpodoxime (CPD), Ceftazidime (CAZ), Ceftriaxone (CTR), Cefuroxime (CXM), Ciprofloxacin (CIP), Clarithromycin (CLR), Clindamycin (CD), Cloxacillin (Cox), Doxycycline (DO), Impipenem (IPM), Levofloxacin (LE), Linezolid (LZ), Meropenem (MRP), Methicillin (MC), Moxifloxacin (MO), Ofloaxacin (OF), Pipracillin+ Tazobactum, (PIT), Teicoplanin (TEI), Vancomycin (VA). Antibiotic sensitivity test was performed by disc diffusion method on Muller hinton agar (MHA) plates.
S. aureus isolates were swabbed on Mueller Hinton agar plates by using sterilize cotton swabs. The antibiotic discs were placed on the agar surface using a sterilize forceps. Plates were incubated at 37°C for 24 h. Plates were observed for zone of inhibition (
Iqbal et al., 2004).
3 Results and discussion
S. aureus is a common reason of infectious disease in hospitals and is most liable to infect new born babies, surgical patients, old and malnourished persons and patients with diabetes and other chronic diseases. The patients admitted in hospitals with impaired immunity are at highest risk of getting infection with S. aureus. Even though several antibiotics are in use to control S. aureus infection, they failed to control the associated morbidity and mortality. This failure of antibiotics to efficiently control S. aureus could be attributed to the emergence of drug resistance in microorganisms. It had been observed that the excessive use of antibiotics can trigger the development of drug resistance in microorganisms. During this study, 50 samples of S. aureus were isolated from the pus, throat swabs and urine specimens collected from admitted patients. Among 50 S. aureus isolates, 48 (96%) were found to be resistance toward Aztreonam and Doxicycline followed by Ciprofloxacin (n = 45, 90%), Cefpodoxime and Ceftazidime (n = 44, 88%), Cefuroxime (n = 40, 80%), Pipracillin+ Tazobactum (n = 38, 76%), Cefoparazone (n = 36, 72%), Amoxicillin+ Clavulanic acid and Ceftriaxone (n = 33, 66%), Levofloxacin (n = 32, 64%), Moxifloxacin (n = 31, 62%), Ofloaxacin (n = 25, 50%), Cloxacillin (n = 22, 44%), Azithromycin (n = 21, 42%), Clindamycin (n = 19, 38%), Meropenem (n = 18, 36%), Clarithromycin (n = 16, 32%), Ampicillin+ sulbactam (n = 13, 26%), Amikacin (n = 12, 24%), Impipenem (n = 8, 16%), Linezolid and Methicillin (n = 7, 14%) and Teicoplanin (n = 3, 6%). All 50 isolates of S. aureus were found to be sensitive toward vancomycin. Results are summarized in Table 1 and graphically represented in Fig. 1.
Results of this study are representing the increase in incidents of drug resistance in the clinical isolates of S. aureus which is an issue of concern. Among 50 S. aureus isolates, 7 isolates were found to be resistance toward Methicillin which is an alarming issue in healthcare industry. A routine screening of microorganism for their antibiotic sensitivity pattern could significantly help to establish the suitable antibiotic and its therapeutic dose, which eventually reduces the chances of getting drug resistance in microorganisms.
Methicillin-resistant
Staphylococcus aureus (MRSA) is one of the major cause of morbidity and mortality when compare to the other
S. aureus infections. The resistance pattern of
S. aureus has underscored the need for new antimicrobial drugs. It is now migrated into the community. This strain shared some characteristics features with nosocomial strains due to this it antimicrobial susceptibility and potential virulence will vary (
Appelbaum, 2006).
This study was alarming the resistance of
S. aureus and also the diminishing efficacy of antimicrobial agents for the treatment of
S. aureus infections. Still new drug exist, its shelf-life is likely to be increasingly limited. Hence, new approaches to treatment and prevention will become more and more important, especially with the diminishing availability of new “wonder drugs” (
Lowy, 2003).
4 Conclusion
This study draws attention on the need of routine surveillance of antibiotic sensitivity pattern of S. aureus with a view to selecting appropriate therapy. The results of this study showed that the Vancomycin is the most effective antibiotic to control S. aureus infection. In addition Teicoplanin also demonstrated the promising results.
Higher Education Press and Springer-Verlag Berlin Heidelberg
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