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Trends in antibiotic susceptibility patterns and epidemiology of MRSA isolates from several hospitals in Riyadh, Saudi Arabia.

Baddour MM, Abuelkheir MM, Fatani AJ - Ann. Clin. Microbiol. Antimicrob. (2006)

Bottom Line: Methicillin-resistant Staphylococcus aureus (MRSA), is associated with high morbidity and mortality rates with rapid development of resistance.Quinupristin-dalfopristin and linezolid are the most effective antibiotics tested against inpatient isolates while quinupristin-dalfopristin and gatifloxacin seem to be the most effective against outpatient isolates.Trends over time show a tendency towards decreased susceptibility to gatifloxacin and linezolid with increasing susceptibility to gentamicin and sulfamethoxazole/trimethoprim.

View Article: PubMed Central - HTML - PubMed

Affiliation: Microbiology and Immunology Dept, Faculty of Medicine, Alexandria University, Egypt. baddourm@yahoo.com

ABSTRACT

Background: Methicillin-resistant Staphylococcus aureus (MRSA), is associated with high morbidity and mortality rates with rapid development of resistance.

Methods: A total of 512 MRSA isolates were procured from 6 major hospitals in Riyadh, Saudi Arabia and antibiotic susceptibilities and MICs were documented against several antibiotics and vancomycin. SPSS version 10 was used for statistical analysis.

Results: The prevalence of MRSA in the study hospitals ranged from 12% to 49.4%. Mean patient age was 44 years with males constituting 64.4% and females 35.6%. Approximately 41.5% of the isolates came from patients in the extreme age groups. MIC for vancomycin was in the susceptible range for all isolates ranging from 0.25 to 3 ug/ml. The overall susceptibility of MRSA to the various antibiotics tested was: fusidic acid 4.3%, sulfamethoxazole/trimethoprim 33.8%, gentamicin 39.6%, mupirocin 77.0%, gatifloxacin 78.9%, chloramphenicl 80.7%, linezolid 95.1%, quinupristin/dalfopristin 100%. Some differences were noted in the resistance of isolates among the participating hospitals reflecting antibiotic usage. On the whole, inpatient isolates (accounting for 77.5% of the isolates) were more resistant than outpatient isolates (22.5%) except for linezolid. Quinupristin-dalfopristin and linezolid are the most effective antibiotics tested against inpatient isolates while quinupristin-dalfopristin and gatifloxacin seem to be the most effective against outpatient isolates. Approximately one forth of the isolates are no longer susceptible to mupirocin used for eradication of the carrier state reflecting resistance developing after widespread use. Trends over time show a tendency towards decreased susceptibility to gatifloxacin and linezolid with increasing susceptibility to gentamicin and sulfamethoxazole/trimethoprim.

Conclusion: Quinupristin/dalfopristin and linezolid are two valuable additions to our antimicrobial armamentarium, but resistance has already been described. To preserve their value, their use should be limited to those rare cases where they are clearly needed. Fusidic acid, the local antibiotic, gentamicin and trimethoprim/sulfamethoxazole should not be relied upon for treatment of MRSA infections, at least empirically as the percentage of susceptible isolates is very low.

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Comparative susceptibility of the 512 MRSA isolates to tested antimicrobials.
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Figure 1: Comparative susceptibility of the 512 MRSA isolates to tested antimicrobials.

Mentions: As depicted in table 1 and figure 1, 78.9% of the isolates were susceptible to gatifloxacin (isolates with intermediate resistance were included with the resistant ones). This is in contrast to the high resistance rates of MRSA isolates from Japan to fluoroquinolones which are at the high 80–95%[47], which probably reflects the excessive use of this class of antibiotics there and thus induction of resistance. In North America, gatifloxacin susceptibility is 64.7%[34], which is closer to our results. Susceptibility to chloramphenical in the Japanese isolates ranged from 3.8% to 5.1%[47], while in the present study, 80.7% of MRSA were susceptible. Panhotra et al, from Al-Hasa region of Saudi Arabia report full susceptibility of their MRSA isolates to chloramphenicol[48]. Linezolid was highly effective in the present study with an overall 95.9% susceptibility and was also reported in 2005 from Poland and in 2006 from UK to be fully susceptible[49,50]. Isolates showed a 77.0% susceptibility to mupirocin, this is in between the 83.4% reported from Austria, Germany and Switzerland[51], the 88.9% reported from the UK[22] and the 71.9% reported from Kuwait[52]. Gentamicin was poorly effective against our MRSA isolates (39.6%) and gave even weaker results reported in 2001 (34.8%)[28], and 2005 (0% & 25%)[48,49]. Results given by trimethoprim-sulfamethoxazole are even worse with a mere 33.8% susceptibility in the current study, 21.1% from Bukharie and Abdelhadi[28], 2001 and full resistance by Panhotra et al, 2005[48]. Our results are in sharp contrast with those of Echa'niz-Aviles et al[53], 2006 who found all their isolates to be susceptible to gentamicin and trimethoprim-sulphamethoxazole. It is pertinent to deduce that antibiotics such as gentamicin and trimethoprim-sulfamethoxazole and the local fusidic acid should no longer be relied upon at least for empirical treatment of the local MRSA isolates. Whether the resistance observed in tested isolates comes from their inherent genetic propensity to acquire resistance or this is due to mere selection of antibiotic resistant isolates through monotherapy or under-dosage could not be clarified as the previous antibiotic intake data were not available for all isolates.


Trends in antibiotic susceptibility patterns and epidemiology of MRSA isolates from several hospitals in Riyadh, Saudi Arabia.

Baddour MM, Abuelkheir MM, Fatani AJ - Ann. Clin. Microbiol. Antimicrob. (2006)

Comparative susceptibility of the 512 MRSA isolates to tested antimicrobials.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1713249&req=5

Figure 1: Comparative susceptibility of the 512 MRSA isolates to tested antimicrobials.
Mentions: As depicted in table 1 and figure 1, 78.9% of the isolates were susceptible to gatifloxacin (isolates with intermediate resistance were included with the resistant ones). This is in contrast to the high resistance rates of MRSA isolates from Japan to fluoroquinolones which are at the high 80–95%[47], which probably reflects the excessive use of this class of antibiotics there and thus induction of resistance. In North America, gatifloxacin susceptibility is 64.7%[34], which is closer to our results. Susceptibility to chloramphenical in the Japanese isolates ranged from 3.8% to 5.1%[47], while in the present study, 80.7% of MRSA were susceptible. Panhotra et al, from Al-Hasa region of Saudi Arabia report full susceptibility of their MRSA isolates to chloramphenicol[48]. Linezolid was highly effective in the present study with an overall 95.9% susceptibility and was also reported in 2005 from Poland and in 2006 from UK to be fully susceptible[49,50]. Isolates showed a 77.0% susceptibility to mupirocin, this is in between the 83.4% reported from Austria, Germany and Switzerland[51], the 88.9% reported from the UK[22] and the 71.9% reported from Kuwait[52]. Gentamicin was poorly effective against our MRSA isolates (39.6%) and gave even weaker results reported in 2001 (34.8%)[28], and 2005 (0% & 25%)[48,49]. Results given by trimethoprim-sulfamethoxazole are even worse with a mere 33.8% susceptibility in the current study, 21.1% from Bukharie and Abdelhadi[28], 2001 and full resistance by Panhotra et al, 2005[48]. Our results are in sharp contrast with those of Echa'niz-Aviles et al[53], 2006 who found all their isolates to be susceptible to gentamicin and trimethoprim-sulphamethoxazole. It is pertinent to deduce that antibiotics such as gentamicin and trimethoprim-sulfamethoxazole and the local fusidic acid should no longer be relied upon at least for empirical treatment of the local MRSA isolates. Whether the resistance observed in tested isolates comes from their inherent genetic propensity to acquire resistance or this is due to mere selection of antibiotic resistant isolates through monotherapy or under-dosage could not be clarified as the previous antibiotic intake data were not available for all isolates.

Bottom Line: Methicillin-resistant Staphylococcus aureus (MRSA), is associated with high morbidity and mortality rates with rapid development of resistance.Quinupristin-dalfopristin and linezolid are the most effective antibiotics tested against inpatient isolates while quinupristin-dalfopristin and gatifloxacin seem to be the most effective against outpatient isolates.Trends over time show a tendency towards decreased susceptibility to gatifloxacin and linezolid with increasing susceptibility to gentamicin and sulfamethoxazole/trimethoprim.

View Article: PubMed Central - HTML - PubMed

Affiliation: Microbiology and Immunology Dept, Faculty of Medicine, Alexandria University, Egypt. baddourm@yahoo.com

ABSTRACT

Background: Methicillin-resistant Staphylococcus aureus (MRSA), is associated with high morbidity and mortality rates with rapid development of resistance.

Methods: A total of 512 MRSA isolates were procured from 6 major hospitals in Riyadh, Saudi Arabia and antibiotic susceptibilities and MICs were documented against several antibiotics and vancomycin. SPSS version 10 was used for statistical analysis.

Results: The prevalence of MRSA in the study hospitals ranged from 12% to 49.4%. Mean patient age was 44 years with males constituting 64.4% and females 35.6%. Approximately 41.5% of the isolates came from patients in the extreme age groups. MIC for vancomycin was in the susceptible range for all isolates ranging from 0.25 to 3 ug/ml. The overall susceptibility of MRSA to the various antibiotics tested was: fusidic acid 4.3%, sulfamethoxazole/trimethoprim 33.8%, gentamicin 39.6%, mupirocin 77.0%, gatifloxacin 78.9%, chloramphenicl 80.7%, linezolid 95.1%, quinupristin/dalfopristin 100%. Some differences were noted in the resistance of isolates among the participating hospitals reflecting antibiotic usage. On the whole, inpatient isolates (accounting for 77.5% of the isolates) were more resistant than outpatient isolates (22.5%) except for linezolid. Quinupristin-dalfopristin and linezolid are the most effective antibiotics tested against inpatient isolates while quinupristin-dalfopristin and gatifloxacin seem to be the most effective against outpatient isolates. Approximately one forth of the isolates are no longer susceptible to mupirocin used for eradication of the carrier state reflecting resistance developing after widespread use. Trends over time show a tendency towards decreased susceptibility to gatifloxacin and linezolid with increasing susceptibility to gentamicin and sulfamethoxazole/trimethoprim.

Conclusion: Quinupristin/dalfopristin and linezolid are two valuable additions to our antimicrobial armamentarium, but resistance has already been described. To preserve their value, their use should be limited to those rare cases where they are clearly needed. Fusidic acid, the local antibiotic, gentamicin and trimethoprim/sulfamethoxazole should not be relied upon for treatment of MRSA infections, at least empirically as the percentage of susceptible isolates is very low.

Show MeSH
Related in: MedlinePlus