Antibiogram of Pseudomonas aeruginosa and Methicillin-resistant Staphylococcus aureus in patients with diabetes

Objective: To determine the antibiogram of Pseudomonas aeruginosa and Methicillin-resistant Staphylococcus aureus (MRSA) in patients with diabetes. Methods: The study was carried out in the Microbiology Department of Clinical and Research Laboratory, Baqai Institute of Diabetology and Endocrinology (BIDE) from January 2012 to December 2012. All samples received in the laboratory were processed according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Identification of Pseudomonas aeruginosa and Methicillin-resistant Staphylococcus aureus (MRSA) was done and antimicrobial susceptibility pattern was determined by disc diffusion method. Results: A total of 585 pathogens were isolated from 542 specimens of patients with diabetes. One hundred twenty one (20.68%) Pseudomonas aeruginosa and 25(4.27%) non-aeruginosa Pseudomonas were detected from 542 samples. Among 108 (18%) samples detecting the growth of Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus (MRSA) were found in 42 (39%) samples. Pseudomonas aeruginosa showed marked susceptibility to imipenem (100%) followed by piperacillin / tazobactam (90.91%). All MRSA positive specimens were susceptible to vancomycin, but highly or completely resistant to the other antimicrobial drugs. Conclusion : In the present study imipenem, piperacillin/tazobactam and sulbactam-cefoperazone were found to be the most effective drugs against Pseudomonas aeruginosa. The majority of MRSA were resistant to one or more than one antimicrobial drugs. Vancomycin and imipenem were the most effective drugsagainstStaphylococcus aureus and MRSA. .


INTRODUCTION
Diabetes is a metabolic disorder affecting 371 million people worldwide. At present, Pakistan has around 6.6 million people with diabetes; the number is anticipated to rise to 11.4 million by the year 2030. 1 Patients with diabetes are more prone to life-threatening infections compared to patients without diabetes. 2 Pseudomonas aeruginosa, a known opportunistic pathogen frequently causes serious infections. Usually compromised hosts like patients with diabetes are the main target of Pseudomonas aeruginosa and the pathogenicity of the organism is based on its ability to produce a variety of toxins, proteases and ability to resist phagocytosis. It may cause severe tissue damage in patients with diabetes and should never be ignored. 3 High frequency of Pseudomonas aeruginosa was found in different studies. [3][4][5] Staphylococcus aureus belongs to the family Staphylococcaceae, isspherical, Gram positive non motile cocci. Staphylococcus aureusis usually a component of mixed infections". 6 Approximately 20-30% of the general population is "staph carriers". 7 Methicillin-resistant Staphylococcus aureus (MRSA) are commonly seen among those who have weak immune system. 7 MRSA may cause severe infections in hospitalized patients, such as bloodstream infections, surgical wound infections and pneumonia. 8 The frequency of MRSA varied considerably in different studies i.e. from 31.1% in an Iranian study 9 to as high as 63.4% in a study conducted in China. 10 The present study was designed to determine the antibiogram of Pseudomonas aeruginosa and Methicillin-resistant Staphylococcus aureus in patients with diabetes in a tertiary care hospital of Karachi-Pakistan.

METHODS
A descriptive study was conducted at the Department of Microbiology, Clinical and Research Laboratory, Baqai Institute of Diabetology and Endocrinology (BIDE), a 24 hours laboratory service in Karachi-Pakistan from January 2012 to December 2012.

RESULTS
Overall, a total of 585 pathogens were isolated from 542 specimens of patients with diabetes. Tissue were the commonest specimens received in the laboratory 314 (57.93%) followed by pus 95 (17.5%), bone 32 (5.9%) and other samples (blood, urine, stool, sputum and body fluids) 101 (18.6%) as shown in Table-I. The frequency of Pseudomonas aeruginosa was 27.07%, 24.21%, 37.50%, and 33.33% in tissue, pus, bone and fecal specimens respectively. About 5.41%, 5.26% and 9.38% tissue, pus and bone specimens respectively showed the growth of Nonaeruginosa Pseudomonas as shown in Table- (Table-II).
Antimicrobial sensitivity patterns of microbial isolates are shown in Table-III. Both Pseudomonas aeruginosa and non-aeruginosa Pseudomonas showed 100% sensitivity against imipenem.

DISCUSSION
The results of our study show a comprehensive evaluation of microbiological profile and antimicrobial susceptibility pattern of two super bugs Pseudomonas aeruginosa and Methicillinresistant Staphylococcus aureus in patients with diabetes.
High frequency of Pseudomonas aeruginosa was found in various studies. 4,5,13 In our study 20.68% specimens showed the growth of Pseudomonas aeruginosa similar to the findings of other studies. 14,15 While low frequency was observed in studies conducted in Iran (5.4%) 9 and Northern areas of Pakistan (4%). 16 The frequency of Gram positive isolates in this study was 22%, while in a local study from Pakistan frequency of Gram positive was found to be 46%. 16 May be the difference is due to environmental factors and the available public health facilities.
Most frequent aerobic Gram positive isolate found in our study was Staphylococcus aureus (18%). The frequency of MRSA in the study was 39%, which is similar to the findings of other studies. 9,17 However, studies conducted in China and India showed high prevalence of MRSA63.4% and 65.5% respectively. 10,18 Imipenem was found to be the most effective drug against Pseudomonas aeruginosa in our study which is similar to the other studies. 9,[13][14][15][19][20][21] In this study piperacillin / tazobactam appeared as the second most effective drug against Pseudomonas aeruginosa infection (90.91% susceptibility). Whereas Indian studies showed 83% and 66% susceptibility of piperacillin / tazobactam towards Pseudomonas aeruginosa. 14,21,22 Our study results showed 80.9% susceptibility of Pseudomonas aerug inosaisolates towards amikacin is also similar to the other studies. 14,15,22 The frequency of imipenem susceptibility to Staphylococcus aureus in diabetic foot infections was 90% in our study while it was 100% in an Indian study; 23 whereas it was only 33.3% in an Iranian study. 15 Highly resistant MRSA to cefpirome and erythromycin (98%) were observed in our study whereas it was 88.2% in a Chinese study, 10 while lower rates (40%) were found in an Indian study. 24 About 93% of MRSA showed resistance towards clarithromycin, chloramphenicol and ciprofloxacin in this study while in an Indian study 20% of chloramphenicol and 50% of ciprofloxacin resistant MRSA were isolated. 24 In our study 83% of sulphamethoxazole resistant MRSA were found while they were 58.8% in Chinese study 10 High rate of clindamycin resistant MRSA (82.4%) was found in Chinese study 10 while it was 76% in our study.

CONCLUSION
In the present study imipenem, piperacillin/ tazobactam and sulbactam-cefoperazone were found to be the most effective drugs against Pseudomonas aeruginosa. The majority of MRSA were resistant to one or more than one antimicrobial drugs. Vancomycin and imipenem were the most effective drugs against Staphylococcus aureus and MRSA.

Declaration of Competing Interests:
Nothing to declare.