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Phenotypic and genetic characterization of multidrug-resistant Staphylococcus aureus in the tropics of Southeast Asia

Zulkeflle SNM, Yusaimi YA, Sugiura N, Iwamoto K, Goto M, Utsumi M, et al.

Microbiology (Reading), 2016 12;162(12):2064-2074.
PMID: 27902427 DOI: 10.1099/mic.0.000392

Antibiotic resistance has become a major public health problem throughout the world. The presence of antibiotic-resistant bacteria such as Staphylococcus aureus and antibiotic resistance genes (ARGs) in hospital wastewater is a cause for great concern today. In this study, 276 Staph. aureus isolates were recovered from hospital wastewater samples in Malaysia. All of the isolates were screened for susceptibility to nine different classes of antibiotics: ampicillin, ciprofloxacin, gentamicin, kanamycin, erythromycin, vancomycin, trimethoprim and sulfamethoxazole, chloramphenicol, tetracycline and nalidixic acid. Screening tests showed that 100 % of Staph.aureus isolates exhibited resistance against kanamycin, vancomycin, trimethoprim and sulfamethoxazole and nalidixic acid. Additionally, 91, 87, 50, 43, 11 and 8.7 % of isolates showed resistance against erythromycin, gentamicin, ciprofloxacin, ampicillin, chloramphenicol and tetracycline, respectively. Based on these results, 100 % of isolates demonstrated multidrug-resistant (MDR) characteristics, displaying resistance against more than three classes of antibiotics. Of 276 isolates, nine exhibited resistance to more than nine classes of tested antibiotics; these were selected for antibiotic susceptibility testing and examined for the presence of conserved ARGs. Interestingly, a high percentage of the selected MDR Staph.aureus isolates did not contain conserved ARGs. These results indicate that non-conserved MDR gene elements may have already spread into the environment in the tropics of Southeast Asia, and unique resistance mechanisms against several antibiotics may have evolved due to stable, moderate temperatures that support growth of bacteria throughout the year.

Matched MeSH terms: Vancomycin/pharmacology
Susceptibility patterns of anaerobes isolated from clinical specimens in tertiary Hospital, Malaysia

Ishak N, Abdul Wahab Z, Amin Nordin S, Ibrahim R

Malays J Pathol, 2020 Aug;42(2):245-252.
PMID: 32860377

INTRODUCTION: The susceptibility patterns of anaerobes are becoming less predictable due to the emergence of anaerobic resistance trends to antibiotics; hence increasing the importance of the isolation and antimicrobial susceptibility testing of anaerobes.
MATERIALS AND METHODS: This study investigated the isolation of anaerobes from the clinical specimens of Hospital Sungai Buloh, Malaysia, from January 2015 to December 2015. All isolates were identified using the API 20A system (bioMérieux, France). Antimicrobial susceptibility testing was performed using the E-test (bioMérieux, France).
RESULTS: The proportion of obligate anaerobes isolated from the clinical specimens was 0.83%. The Gram-positive anaerobes were most susceptible to vancomycin and imipenem, showing 100% sensitivity to these antimicrobials, followed by clindamycin (86.3%), penicillin (76.7%), and metronidazole (48.9%). Meanwhile, Gram-negative anaerobes were most susceptible to metronidazole (96%) followed by imipenem (89%), clindamycin (79%), and ampicillin (32%). The present study also showed that 3 out of 12 Bacteroides fragilis isolates were resistant to imipenem.
CONCLUSION: This study demonstrated the differences in the susceptibility patterns of anaerobes towards commonly used antimicrobials for the treatment of anaerobic infections. In summary, continuous monitoring of antimicrobial resistance trends among anaerobes is needed to ensure the appropriateness of treatment.

Matched MeSH terms: Vancomycin/pharmacology
Synergy of flavone with vancomycin and oxacillin against vancomycin-intermediate Staphyloccus aureus

Bakar NS, Zin NM, Basri DF

Pak J Pharm Sci, 2012 Jul;25(3):633-8.
PMID: 22713953

This study evaluated in vitro activity of 9 flavonoids in combination with vancomycin or oxacillin against vancomycin-intermediate Staphylococcus aureus (VISA) ATCC 700699 by employing the checkerboard method to obtain Minimal inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) index. Six flavonoids namely hesperitin, rutin, naringenin, flavones, naringin and 3, 7-dihyroxyflavone which exhibited notable inhibitory activity (MIC values < 3200 μg/ml) were further evaluated for combination assay with antibiotics. The combinations of vancomycin+flavone and oxacillin+flavone were found synergistic with the FIC index value 0.094 and 0.126, respectively. Other combinations showed an additive interaction (FIC index = 1.063) but no antagonistic reaction (FIC index > 4) were observed. In time kill studies, oxacillin-flavone combination at synergistic concentration demonstrated bactericidal effect at 24 h period with concentration-dependent manner on the VISA strain. Following 1 h exposure, the combination also produced persistent effect on the bacteria growth for 2.9 hrs at 1x sub-MIC and more than 24 h at 5x of sub-MIC and there was a significant difference between both concentrations (p<0.05). Vancomycin-flavone combination, however, showed no concentration-dependent effect and lower PAE values (1.159 h and 2.322 h at 1x and 5x sub-MIC, respectively) on the VISA strain. In conclusion, flavone markedly intensifies the susceptibility of oxacillin against VISA and the combination can be implicated for further interaction studies at molecular level.

Matched MeSH terms: Vancomycin/pharmacology*
The relationship between trough concentration of vancomycin and effect on methicillin-resistant Staphylococcus aureus in critically ill patients

Cheong JY, Makmor-Bakry M, Lau CL, Abdul Rahman R

S. Afr. Med. J., 2012 Jul;102(7):616-9.
PMID: 22748440

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections in intensive care units in Malaysia is significant. Invasive MRSA infections are commonly treated with vancomycin. In clinical practice, the serum vancomycin trough concentration is used as a surrogate marker of vancomycin efficacy. A low concentration of vancomycin may result in less effective therapy and increase the risk of bacterial resistance. We evaluated the relationship between the resolution of MRSA infections and trough concentrations of vancomycin.

Matched MeSH terms: Vancomycin/pharmacology