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Letter
Methicillin-resistant Staphylococcus
aureus, Pakistan, 1996–2003
Tariq Butt,*
Rifat Nadeem Ahmad,* Muhammad Usman,* and Abid Mahmood*
*Armed Forces Institute of Pathology, Rawalpindi, Pakistan
Suggested
citation for this article
To the Editor: This letter is written in response to the article
titled "Co-trimoxazole-sensitive, methicillin-resistant Staphylococcus
aureus, Israel, 1988–1997" (1). We found the
authors' findings most interesting. As the authors pointed out, methicillin-resistant
Staphylococcus aureus (MRSA) infections have become a major problem
worldwide. The problem is not restricted to industrialized countries.
The last decade has seen an alarming increase in MRSA infections in Pakistani
hospitals (2). Pakistan's Armed Forces Institute of Pathology
provides laboratory services to a 1,500-bed tertiary-care hospital in
Rawalpindi and is the main reference laboratory in northern Pakistan.
According to our computerized database, the frequency of MRSA among all
nosocomial isolates of S. aureus increased from 39% (212/543) in
1996 to 51% (516/1,018) in 2003 (p < 0.0001). Most of the isolates
were obtained from pus and pus swab specimens (153 in 1996 and 394 in
2003), while the rest were obtained from blood (20 in 1996 and 37 in 2003),
intravenous catheter tips and surgical drainage tubes (14 in 1996 and
31 in 2003), various body fluids (9 in 1996 and 19 in 2003), respiratory
secretions (8 in 1996 and 18 in 2003), tissue (4 in 1996, 9 in 2003),
throat swabs (2 in 1996, 6 in 2003), and urine (2 in 1996, 5 in 2003).
During the last 7 years, resistance in MRSA isolates has steadily increased
to most of the antimicrobial drugs such as gentamicin (69% in 1996 and
88% in 2003), ciprofloxacin (87% in 1996 and 94% in 2003), clindamycin
(60% in 1996 and 70% in 2003), and rifampicin (20% in 1996 and 60% in
2003). However, resistance to co-trimoxazole and doxycycline has decreased.
In 1996, 15% (32/212) of our MRSA isolates were susceptible to co-trimoxazole,
whereas in the first 9 months of 2003, 43% (222/516) of the isolates were
susceptible (p < 0.0001). Similarly, susceptibility to doxycycline
increased from 34% in 1996 to 49% in 2003 (p = 0.0005). Antimicrobial
drug susceptibility of the isolates was tested by the modified Kirby-Bauer
technique and results were interpreted according to the National Committee
for Clinical Laboratory Standards criteria (3). Methicillin
resistance was tested by using 1 µg oxacillin disks (Oxoid, Basingstoke,
Hampshire, UK) on Mueller-Hinton agar containing 4% sodium chloride. Plates
were incubated at 35°C for 24 hours.
We agree with Bishara et al. (1) that the increase in
susceptibility is likely due to decreased use of these antimicrobial drugs
for staphylococcal infections in clinical practice. The use of co-trimoxazole
in our hospital decreased from 48 daily doses per 1,000 hospital days
in 1996 to 35 daily doses in 2003, while use of doxycycline decreased
from 12 daily doses per 1,000 hospital days in 1996 to 9 daily doses in
2003 (4). These antimicrobial drugs offer an inexpensive
alternative to glycopeptides for the treatment of MRSA infections. Data
from the United States and Europe have shown that vancomycin-intermediate
S. aureus isolates also remain susceptible to some of the conventional
antimicrobial drugs, including co-trimoxazole (5). If
their efficacy in vivo is validated by clinical trials, use of these conventional
drugs would not only reduce the load on overstretched health care budgets
but reduce the use of vancomycin, therefore decreasing the risk of isolates
continuing to develop vancomycin resistance.
References
- Bishara J, Pitlik S, Samra Z, Levy I, Paul M, Leibovici
L. Co-trimoxazole–sensitive,
methicillin-resistant Staphylococcus aureus, Israel, 1988–1997.
Emerg Infect Dis. 2003;9:1168–9.
- Hafiz S, Hafiz AN, Ali L, Chughtai AS, Memon B, Ahmed A, et al. Methicillin
resistant Staphylococcus aureus: a multicentre study. J Pak
Med Assoc. 2002;52:312–4.
- National Committee for Clinical Laboratory Standards. Performance
standards for antimicrobial disk susceptibility tests. 7th ed. Approved
standard M2-A7. Wayne (PA): The Committee; 2000.
- World Health Organization Collaborating Centre for Drug Statistics
Methodology. Guidelines for ATC classification and DDD assignment. Oslo:
The Centres; 1996.
- Tenover FC, Biddle JW, Lancaster MV. Increasing
resistance to vancomycin and other glycopeptides in Staphylococcus
aureus. Emerg Infect Dis. 2001;7:327–32.
Suggested citation
for this article:
Butt T, Ahmad RN, Usman M, Mahmood A. Methicillin-resistant Staphylococcus
aureus, Pakistan, 1996–2003 [letter]. Emerg Infect Dis [serial on
the Internet]. 2004 Sep [date cited]. Available from: http://www.cdc.gov/ncidod/EID/vol10no9/03-0844.htm
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