Abstract
Background
Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is a known risk factor for nosocomialtransmission and infection. In an effort to mitigate this problem, topical mupirocin has been widely used for clearing nasal carriage of MRSA. However, mupirocin resistance has become a worldwide concern due to increased use of the antibiotic. The aims of this study were to evaluate the clinical characteristics and prevalence of mupirocin resistance among clinical isolates of staphylococci and to investigate antimicrobial susceptibility.
Methods
A total of 175 S. aureus specimens recovered over a 4-month period from various body sites were tested for resistance to mupirocin and other antibiotics using the Vitek2 automated system. The presence of the mupA gene was assessed in isolates exhibiting resistance to mupirocin and in other selected organisms. The clinical characteristics of the isolates were also reviewed.
Results
Of the 175 S. aureus isolates, 9.1% (16/175) were resistant to mupirocin, with 1.7% (3/175) having high-level resistance (HR) and 7.4% (13/175) having low-level resistance (LR). Patients with HR-mupirocin-resistant S. aureus had a longer duration of hospitalization (P=0.026). Of the 13 LR-mupirocin-resistant S. aureus strains, 11 had identical antibiogram patterns. The mupA gene was detected only among HR isolates.
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Fig. 1.
Bands of mupA gene in 3 high-level resistance of mupirocin. Lane 1, patient No. 162; Lane 2, patient No. 192; Lane 3, patient No. 195; Lane 4, PCR size marker.
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Table 1.
Distribution of mupirocin MICs among 175 strains of Staphylococcus aureus
Mupirocin resistance | MIC (μg/mL) | No. of isolate (%) |
---|---|---|
Susceptible | <2 | 150 (85.7) |
4 | 9 (5.1) | |
Low-level resistant | 64 | 13 (7.4) |
High-level resistant | ≥512 | 3 (1.7) |
Total | 175 (100) |
Table 2.
Clinical characteristics of 175 strains of Staphylococcus aureus
Table 3.
Antimicrobial resistance profile of 108 MRSA strain
Table 4.
Epidemiologic and clinical features of the sixteen mupirocin-resistant Staphylococcus aureus
No. | MR | Antibiogram∗ | Specimen | Place | Hospita stay (days) | Primary diagnosis |
---|---|---|---|---|---|---|
4 | HR | LQVT | Blood | ICU | 222 | COPD |
8 | LR | LQRTsVT | Sputum | GW | 6 | COPD |
10 | LR | LQRTsVT | Ascitic fluid | GW | 24 | Duodenal ulcer |
15 | LR | GLQRTsVT | Sputum | ICU | 5 | SAH |
55 | LR | LQRTsVT | Sputum | ED | 2 | COPD |
65 | LR | LQRTsVT | Sputum | GW | 30 | Gangrene of toe |
66 | LR | LQRTsVT | Wound | GW | 2 | Sacral sore |
79 | LR | LQRTsVT | Sputum | GW | 4 | ESRD |
92 | LR | LQVT | Sputum | GW | 9 | Pneumothorax |
99 | LR | LQRTsVT | Sputum | GW | 60 | Aplastic anemia |
100 | LR | LQRTsVT | Sputum | ICU | 4 | Septic shock |
106 | LR | LQRTsVT | Blood | GW | 4 | ESRD |
107 | HR | CLQRTsV | T Wound | GW | 24 | Sacral sore |
109 | HR | CiCELQRTs TeVT | Sputum | GW | 55 | SAH |
153 | LR | LQRTsVT | Wound | GW | 35 | Open wound of ankle and foot |
169 | LR | LQRTsVT | Sputum | ICU | 23 | Spine fracture |
∗ Type of antibiogram: LQVT (susceptible to linezolid, quinupristin-dafopristin, vancomycin, teicoplanin), LQRTsVT (susceptible to linezolid, quinupristin-dafopristin, rifampin, trimethoprim-sulfamethoxazole, vancomycin, teicoplanin), GLQRTsVT (susceptible to gentamicin, linezolid, quinupristin-dafopristin, rifampin, trimethoprim-sulfamethoxazole, vancomycin, teicoplanin), CiCELQRTsTeVT (susceptible to ciprofloxacin, clindamycin, erythromycin, linezolid, quinupristin-dafopristin, rifampin, trimethoprim-sulfamethoxazole, tetracycline, vancomycin, teicoplanin).