Mueller–Hinton agar is superior to PDM blood agar for detection of methicillin-resistant Staphylococcus aureus

Abstract

The aim of this study was to compare the expression of oxacillin resistance in methicillin-resistant Staphylococcus aureus (MRSA) on Paper Disc Method agar supplemented with 5% defibrinated blood (PDM blood agar) and Mueller-Hinton agar supplemented with 2% NaCl (MH NaCl agar) using different susceptibility tests. Fifty mecA-containing isolates of S. aureus, exhibiting 46 different pulsed-field gel electrophoresis patterns, were comparatively tested using the E test, the single disk diffusion test, and the multipoint inoculation technique, under various culture conditions. The E test incubated at 35 degrees C for 24 h (breakpoint of resistance > or = 2.0 mg/L) detected 94% of the isolates on MH NaCl agar, compared with 28% for PDM blood agar (P < 0.05). The disk diffusion test (breakpoint < 10 mm in diameter) under these incubation conditions detected resistance in 100% of the isolates on MH NaCl agar and in 80% of the isolates on PDM blood agar (P < 0.05). The multipoint technique (breakpoint > or = 1 mg/L), applied at 35 degrees C for 24 h, detected 100% on MH NaCl agar and 46% on PDM blood agar (P < 0.05). Irrespective of the method of susceptibility testing evaluated, MH NaCl agar was superior to PDM blood agar for the detection of oxacillin resistance in mecA-containing S. aureus.

Spread of Clones of Multidrug-Resistant, Coagulase-Negative Staphylococci Within a University Hospital

“…13 CNS are associated with bacteremia, wound-related infections, intravascular catheter-related infections, and a variety of postoperative infections. 14 Moreover, it has been shown that CNS have the ability to develop resistance to all hitherto described antibiotics and multidrug-resistant CNS are currently a common finding among hospitalized patients. 46 The emergence of multidrug-resistant CNS has limited the therapeutic arsenal, thus increasing the risk of treatment failure and costs.…”

In vitroEvaluation of the Phagocytosis Activity of Neutrophils and Characterization ofStaphylococcus aureusMastitis in Dairy Cows of Small Family Farms

“…To confirm the MRSA strains, Mueller Hinton agar plates containing 4% NaCl were inoculated and incubated at 35 and 42°C for 24 hours. The bacterial inhibition halos of the bacterial growth on the agar plates were expressed in mm and compared to the established values for the test with a difference >4 mm in diameter between the halos of inhibition containing unidisks with 1, 2, 4, and 6 μg of oxacicline [31]. The in vitro production of β-lactamase was determined by the modified iodometric method [32].…”

Incidence of Methicillin-Resistant Staphylococcus Aureus (MRSA) Recovered from Patients with Urinary Tract Infections in Zakho City/ Kurdistan-Iraq

“…In 1990, a study noted that the mecA gene was not found in methicillin-susceptible isolates of staphylococci (Archer & Pennell, 1990;Louie et al, 2000a). However, later a study demonstrated that the mecA gene was regarded as the benchmark for identifying methicillin-resistant Staphylococcus aureus (MRSA) (Monsen et al, 2003;Unal et al, 1994b). Further studies reported that MRSA strains bearing the genes encoding for Panton-Valentine leucocidin (PVL), a highly powerful toxin, have been accountable for a serious threat to public health (Holmes et al, 2005;Sina et al, 2018).…”