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1

Prevalence and antimicrobial susceptibility pattern of methicillin-resistant

Staphylococcus aureus (MRSA) in CMS-teaching hospital: a preliminary report

R. K. Sanjana 1,   Rajesh Shah2,  Navin Chaudhary2,  Y.I. Singh 3

1Assistant Professor, 2Lecturer, 3Prof & Head, Dept. of  Microbiology, College of Medical Sciences-Teaching Hospital,

Bharatpur, Chitwan District, Nepal.

Abstracts

Aims: Nosocomial infection is a major problem in the world today. Methicillin- resistant Staphylococcus

aureus (MRSA) strains, usually resistant to several antibiotics and also intrinsic resistance to ß- lactam

antibiotics, shows a particular ability to spread in hospitals and now present in most of the countries. The

present study was carried out to investigate the prevalence of MRSA and their rate of resistance to

different antistaphylococcal antibiotics.

Materials and methods: Between April 2007 and December 2009, the clinical specimens submitted at

the microbiology laboratory were processed and all Staphylococcus aureus (S. aureus) isolates were included

in this study. All isolates were identified morphologically and biochemically by standard laboratory

procedures and antibiotic susceptibility pattern including oxacillin was determined by modified Kirby

Bauer disc diffusion method.

Results:  Out of a total of 348 Staphylococcus aureus strains isolated from various clinical samples, 138

(39.6%) were found to be Methicillin- resistant. Among MRSA isolates, 86(62.3%) were from different

inpatient departments, whereas, 52(37.7%) of the isolates were from outpatients. All MRSA were resistant

to penicillin. More than 70% of the MRSA strains were resistant to cephalexin, ciprofloxacin and cloxacillin,

while less than 10% of them were resistant to azithromycin, amikacin and tetracycline. Many MRSA

strains were multidrug resistant. However, no strains were resistant to vancomycin.

Conclusion: This preliminary report showed a high prevalence of MRSA in our hospital. To reduce the

prevalence of MRSA, regular surveillance of hospital acquired infection and isolation is the need of the

hour.

Key words: Nosocomial infection, methicillin-resistant Staphylococcus aureus (MRSA), multidrug resistant.

Correspondence: Dr. R. K. Sanjana

E-mail: Rajkumari_sanjana@yahoo.co.in

, 1-6 Original ArticleJournal of College of Medical Sciences-Nepal, 2010, Vol. 6, No. 1



2

Introduction

Staphylococcus aureus is a leading cause of

hospital acquired infection (HAI) and over the past

50 years it has acquired resistance to previously

effective antimicrobials including the penicillinase

resistant ones like methicillin.1 Today, methicillin

resistant Staphylococcus aureus(MRSA) has

emerged as one of the most important nosocomial

pathogens.2 The percentage of hospitals isolating

MRSA in the developed countries has increased from

2% in the 70’s to 30% in the 90’s.3 Moreover, half of

S. aureus in many centres are methicillin

resistant(multidrug resistant) posing major therapeutic

challenge.4 MRSA causes more than 50% of HAI and

are more virulent than the methicillin sensitive strains.5,6

Prompt diagnosis of MRSA infection is, therefore,

important for patients, health care givers and for

epidemiological purposes. Hospital acquired infection

(HAI) gives an enormous burden to the health care

system significantly affecting the patient’s morbidity and

mortality. It results in prolongation of hospital stay and

hence higher bed occupancy rate with an attendant

increase in the cost of hospitalisation.7, 8 Surveillance

of MRSA related infections especially in the hospital

set up is required and has been doing in the developed

countries. Not only that, the magnitude of the problem

is yet to be quantified. This study is an attempt to assess

the prevalence of methicillin resistant S. aureus

(MRSA) infection and its antibiotic susceptibility

pattern in this hospital.

Materials and methods

This study was based on retrospective data of

samples sent from different wards and OPDs of

College of Medical Sciences-teaching hospital,

Bharatpur. Total strains of 348 S. aureus were isolated

from pus, urine, sputum, wound swab, aural swab,

blood, throat swab and urethral swab during April 2007

and Dec 2009. S. aureus was identified by

conventional method. 9 The antimicrobial susceptibility

test was carried out using Kirby-Bauer’s disc diffusion

method modified and updated by Clinical and

Laboratory Standards Institute guidelines (CLSI). 10

Each of the strain was screened for oxacillin resistance

using American Type Culture Collection (ATCC)

43300 as the control. A standard inoculum was

prepared by direct colony suspension in and comparing

it with 0.5 Mc. Farland turbidity. Using a sterile cotton

swab and after removing the excess of the inoculum

by pressing against the side of the tube, the suspension

was inoculated on a Mueller Hinton Agar medium by

lawn culture  method all over the surface of the medium.

Oxacillin disc (1µg), (HI Media Laboratories, Pvt. Ltd.

Mumbai) was applied along with other antimicrobials

for testing sensitivity and the plates were examined after

an over night incubation at 37 º C. Zone of inhibition

diameter (in mm) were measured and results were

interpreted as sensitive, resistant as per

recommendation of Clinical and Laboratory Standards

Institute guidelines (CLSI). Other antimicrobials tested

were chloramphenicol (30µg), tetracycline (30 µg),

gentamicin (10µg ), erythromycin (15µg), co-

trimoxazole (25µg), cephalexin (30µg ), ciprofloxacin

(5µg), amikacin (30µg ), cefotaxime (30µg) and

vancomycin (10µg ).

Results

Isolation of Staphylococcus was maximum in pus

samples. Out of the 348 strains of S. aureus examined

138 (39.6%) were found to be Methicillin- resistant

and of which 86 (62.3%) were from inpatient

departments. Amongst them only 9 (10.4%) of the

Journal of College of Medical Sciences-Nepal, 2010, Vol. 6, No. 1



3

isolates were from intensive care units (ICU). A total

of 52 (37.7%) MRSA strains were from outpatients.

Maximum isolation of MRSA was from pus (53.3%),

followed by wound swabs (44.4%), sputum (37.5%),

aural swabs (33.3%) etc. (Table- 1) shows detection

of MRSA in different samples. All the strains of MRSA

were found to be resistant to Penicillin. (Table -2)

depicts the antibiotic susceptibility data for all the S.

aureus isolates. Among MRSA, resistance to

cephalexin was 81.8%, ciprofloxacin -71.0%,

cloxacillin -70.6%, erythromycin -58.0%, gentamicin

-38.0%, cefotaxim -31.6%, cotrimoxazole -20.4%,

while amikacin, azithromycin and tetracycline were

resistant to less than 10% of the MRSA strains. Many

MRSA strains were multidrug resistant. No strain was

resistant to vancomycin. However, 41.2% of Methicillin

sensitive S. aureus (MSSA) were resistant to penicillin,

25.7% resistance to cephalexin, 25.4% resistance to

ciprofloxacin, 16.6% resistance to cloxacillin, 14.5%

resistance to erythromycin, 32.3 % resistance to

gentamicin as compared with MRSA. MSSA isolates

also revealed higher susceptibility to cefotaxime,

cotrimoxazole with a resistance rate of 9.3% and 9.8%

of the strains respectively.  None of the MSSA was

resistant to azithromycin.

Table- 1: Isolation of MRSA from Specimens of outdoor and indoor patients in CMS-teaching hospital,

Bharatpur, Nepal

R.K. Sanjana et al. Prevalence and antimicrobial susceptibility..............................: a preliminary report

 
 

                     OPD              Ward & ICU                    Total S.No        
  Specimens S. aureus MRSA   

(%) 
 S. aureus MRSA   

(%) 
S. 
aureus 

MRSA   
 (%) 

1 Pus 60 32        
53.33 

80 53           
66.25    

140 85        
60.71 

2 Urine 20 04        
20.00 

30 08           
26.66 

50 12        
24.00 

3 Wound swab 09 04        
44.44 

10 06           
60.00 

19 10        
52.63 

4 Sputum 08 03        
37.50 

15 06           
20.00 

23 09         
39.13 

5 Aural swab 09 03         
33.33 

20 06            
30.00 

29 09         
31.03 

6 Blood 18 02         
11.11 

34 03            
08.82 

52 05         
09.61 

7 Throat swab 08 02         
25.00 

12 03            
25.00 

20 05         
25.00 

8 CSF 00 00           
00 

01 00             
00 

01 00            
00 

9 Urethral 
swab 

04 01         
25.00   

03 01            
33.33 

07 02         
28.57 

10 Bone 
cartilage 

00 00              
00   

02 00              
00 

02 00            
00 

11 Semen 03 01         
33.33 

02 00             
00 

05 01         
20.00 

Total 139 52         
37.68 

209 86            
41.14  

348 138      
39.65 



4

Discussion

MRSA is a global phenomenon with a prevalence

rate ranging from 2% in Netherland and Switzerland,

to 70% in Japan and Hong Kong.11, 12 In this study, the

prevalence of MRSA was found to be 39.6%.

Prevalence of MRSA was higher among inpatients

(41.1%) than outpatients (37.4%). This difference

could be due to prolonged hospital stay, instrumentation

and other invasive procedures. A comparable

prevalence rate of 34.7%, 31.0% and 38.5% were

also reported from Assam, Tamil Nadu and Delhi13, 14,

15 whereas, in some studies the rate is comparatively

low. In a study in Eastern part of Nepal in Dharan, the

rate of MRSA was (26.4%),16 which was low as

compared to this study. In another study in Nagpur

the rate of MRSA (19.5%) 17 was also low compared

to our study.  However, in another study it was very

high (80.8%).18 Analysis from previous studies revealed

a relationship between methicillin resistance and

Table- 2:  Resistance to individual antimicrobials in MRSA and MSSA isolated in CMS-teaching

hospital, Bharatpur,Nepal

Journal of College of Medical Sciences-Nepal, 2010, Vol. 6, No. 1

               MRSA                 MSSA                  Total S. No Antimicrobials 
Tested Resistance  

(%) 
Tested Resistance  

(%) 
Tested Resistance  

(%) 
1 Penicillin G 126 126             

100 
189 78               

41.25 
315 204             

64.76 
2 Cephalexin 22 18               

81.81 
69 25               

36.23 
91 43               

47.25 
3 Ciprofloxacin 83 59              

71.08 
138 35               

25.36 
221 94               

42.53 
4 Cloxacillin 136 96               

70.58 
187 80               

42.78 
323 127             

39.31 
5 Erythromycin 62 36               

58.06      
124 18               

14.51 
186 54               

29.03 
6 Gentamicin 21 08               

38.09 
65 21               

32.30  
86 29               

33.72 
7 Cefotaxim 57 18              

31.57 
118 11               

09.32 
175 29               

16.57 
8 Co-trimoxazole 44 09              

20.45   
132 13               

09.84        
176 22               

12.50 
9 Ofloxacin 68 12              

17.64 
154 18               

11.68 
222 30               

13.51   
10 Amoxyclav 28 04              

14.28 
84 07               

08.33 
112 11               

09.82 
11 Azithromycin 52 05              

09.61     
158 00               

00 
210 08               

03.80 
12 Amikacin 65 06              

09.23 
112 07               

06.25 
177 13               

07.34 
13 Tetrcyclin 50 04               

08.00  
59 06               

10.16 
109 10               

09.17 
14 Vancomycin 128 00               

00 
186 00               

00 
324 00               

00 
 
 
 



5

resistance to other antibiotics.19, 20 This study showed

that all MRSA isolates were significantly less sensitive

to antibiotics as compared with MSSA isolates. Many

of the isolates were resistant to commonly used

antistaphylococcal agents except vancomycin.

Anupurba et al. also observed that 32% of MRSA

isolates are resistant to all commonly used antibiotics

for S. aureus except vancomycin.21 Because of the

resistance of MRSA to all commonly used antibiotics,

it is necessary to test newer group of antibiotics such

as vancomycin and teicoplanin routinely. Resistance

to (cephalexin) was much higher (81.8%) in this study.

This is comparable to the study done by Namrata et

al. in the eastern part of Nepal who reported the

resistant rate to be above (65%).16  Resistance to

quinolones (ciprofloxacin) was also high (71%) in this

study . In the study reported by Lahari Sakia et al., the

resistant rate was also high (87.5%)  in Assam.13

However, in the same institute, a previous study, in

2001, reported the resistant rate of ciprofloxacin to

be only (22.8%).16 The rapid emergence of

ciprofloxacin is probably due to the indiscriminate and

empirical use of these drugs. MSSA isolates shows

higher susceptibility to penicillin and cloxacillin (100%

vs. 41.3%) and (70.6% vs.43.0%) respectively than

MRSA strains. The epidemiology of MRSA is gradually

changing since its emergence was reported. Initially

there were occasional reports but now it has become

one of the established hospital acquired pathogen.

Moreover, the association of multidrug resistance with

MRSA had added to the problem. ß – lactam

antibiotics like penicillin and cephalexin resistance were

100% and 81% respectively. Resistance to amino

glycosides was more in gentamicin (38%) than amikacin

(9.2%) in this study, however, it cannot be

recommended for empirical treatment of MRSA

associated infections.

Vancomycin seems to be the only antimicrobial

agent which showed 100% sensitivity and may be used

as the drug of choice for treating multidrug resistant

MRSA infections. However, regular monitoring of

vancomycin sensitivity and routine testing of other

newer glycopeptides like teicoplanin should be carried

out. Further, the regular surveillance of hospital

associated infections including monitoring antibiotic

sensitivity pattern of MRSA and formulation of definite

antibiotic policy may be helpful for reducing the

incidence of MRSA infection.

Conclusion

This preliminary report showed a high prevalence

of MRSA in our hospital. There is a need for

surveillance of MRSA and its antimicrobial profile. The

hospital infection control policy and guidelines that

already exists should be strictly implemented and

followed so as to enable the clinicians to deliver better

and proper health care to the patients.

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