170 clinical isolates of Pseudomonas aeruginosa were tested for in vitro susceptibility to gentamicin, amikacin, tobramycin, netilmicin, kanamycin, streptomycin, cefotaxime, ceftriaxone, cefoperazone, ceftazidime, moxalactam, azlocillin, piperacillin and ticarcillin. Against 93 gentamicin-sensitive strains, the most active antibiotics were in descending order, ceftazidime, tobramycin, gentamicin, amikacin, and the ureidopenicillins. Against 77 gentamicin-resistant strains, only ceftazidime, amikacin and moxalactam had mode minimum inhibitory concentrations within achievable peak serum levels after standard therapeutic dosage. There was no correlation between cephalosporin resistance and aminoglycoside resistance except for cefoperazone, which, together with the ureidopenicillins and ticarcillin, showed marked decrease in activity against gentamicin-resistant strains.
Antibiotic resistance in Gram-negative bacteria, particularly Salmonella and Shigella, requires surveillance worldwide. This study describes results of surveys in Hong Kong, Bangkok and Kuala Lumpur. All strains were isolated in hospitals which have large community catchment areas in addition to specialised hospital units. The prevalence of resistant strains was high in all areas. Gram-negative bacteria such as Enterobacter associated with hospital infections were resistant to penicillins and cephalosporins, with gentamicin resistance ranging from about 20% in Kuala Lumpur and Hong Kong, to 35% in Bangkok. Ninety-seven percent of Shigella isolated in Thailand were resistant to ampicillin. About 10% of Salmonella were resistant to chloramphenicol in all three centres.
The in-vitro activity of cefotaxime and cefoperazone were compared using clinically isolated Escherichia coli, Klebsiella spp and Pseudomonas aeruginosa. Cefotaxime was found on a weight to weight basis, to be much more active than cefoperazone. All the three species studied show the presence of cefoperazone-resistant population which were sensitive to cefotaxime. The possible mechanisms of resistance to these antibiotics were discussed.
Four hundred and ninety-eight predominantly pyocin-type 10 clinical strains of Pseudomonas aeruginosa were analyzed for resistance to carbenicillin, cefoperazone, cefotaxime, ceftazidime, gentamicin, amikacin and netilmicin. Based on NCCLS-recommended MIC breakpoints, 245 strains were found to be resistant, of which 41.6% were resistant to carbenicillin, 38% to gentamicin, 37.8% to netilmicin, 26.3% to cefoperazone, 17.9% to cefotaxime, 0.6% to amikacin and none to ceftazidime. Quadruple resistance to carbenicillin, cefoperazone, gentamicin and netilmicin was the most frequent pattern observed. Resistance to older antibiotics (kanamycin, streptomycin and tetracycline) and to mercuric chloride were also common. Conjugation experiments suggested that self-transmissible and non-transmissible plasmids occurred in at least 66 strains.
Dichloromethane and methanol extracts of 13 Zingiberaceae species from the Alpinia, Costus and Zingiber genera were screened for antimicrobial and antioxidant activities. The antimicrobial activity of most of the extracts was antibacterial with only the methanol extract of Costus discolor showing very potent antifungal activity against only Aspergillus ochraceous (MID, 15.6 microg per disc). All the extracts showed strong antioxidant activity comparable with or higher that of alpha-tocopherol.
The in vitro activity of sulperazon (cefoperazone/sulbactam) was tested against 94 ceftazidime-resistant strains of bacteria isolated from mostly seriously ill patients in critical care units. Acinetobacter baumanii, Pseudomonas aeruginosa and Klebsiella pneumoniae made up 80% of the pathogens studied; 90% of the Klebsiella strains were producers of extended-spectrum beta-lactamases (ESBL). The MIC90 of sulperazon for Klebsiella was 12 mg/l (range 1.5-16 mg/l), indicating that this drug may be a useful alternative for the treatment of ceftazidime-resistant, ESBL-producing Klebsiella.
We have isolated and identified a carbapenem-resistant Pseudomonas aeruginosa strain from Malaysia that produces an IMP-7 metallo-beta-lactamase. This isolate showed high-level resistance to meropenem and imipenem, the MICs of which were 256 and 128 micro g/ml, respectively. Isoelectric focusing analyses revealed pI values of >9.0, 8.2, and 7.8, which indicated the possible presence of IMP and OXA. DNA sequencing confirmed the identity of the IMP-7 determinant.
The pattern of antibiotic resistance amongst gram-negative bacteria (GNB) in paediatric units, which have heavy empirical usage of broad-spectrum antibiotics, was studied prospectively over a 6-month period. A total of 200 consecutive, non-duplicate gram-negative isolates were obtained from 109 patients admitted to intensive care and oncology units in two hospitals. The commonest isolates were Klebsiella spp (36.5 per cent) and Pseudomonas (20.0 per cent). The isolates showed lower susceptibility rates to the third-generation cephalosporins (47-62 per cent) compared with cefepime (91 per cent), imipenem (90 per cent) and ciprofloxacin (99 per cent). Fifty-four (52.8 per cent) Klebsiella and Escherichia coli isolates were determined to be extended-spectrum beta-lactamase (ESBL) producing strains. Antibiotics found to be effective against ESBL-producers were imipenem and ciprofloxacin. The high resistance rate amongst GNB to third-generation cephalosporins is a likely consequence of heavy empirical usage of this group of antibiotics. The carbapenems and quinolones remain useful agents in the management of patients admitted to these units.
BACKGROUND AND PURPOSE: Pseudomonas aeruginosa is an important cause of morbidity and mortality in hospitalized, critically ill patients and patients with underlying medical conditions such as cystic fibrosis, neutropenia, and iatrogenic immunosuppression. The prevalence of multiresistant P. aeruginosa isolates has been increasing. The aim of this study was to determine the antimicrobial susceptibility patterns in P. aeruginosa strains isolated at a university teaching hospital in Kuala Lumpur, Malaysia.
METHODS: The Laboratory Information System of the microbiology department was retrospectively reviewed to determine the susceptibility patterns of P. aeruginosa isolates to anti-pseudomonal antibiotics, from January to June 2005. Disk diffusion methods were employed and results were interpreted according to National Committee for Clinical Laboratory Standards guidelines.
RESULTS: 505 clinical isolates of P. aeruginosa were tested. Major sources of these isolates included respiratory tract, wound, urine and blood. The rates of antimicrobial resistance of isolates were 6.73% to amikacin, 12.9% to gentamicin, 10.1% to netilmicin, 10.9% to ceftazidime, 11.3% to ciprofloxacin, 9.9% to imipenem, 10.8% to piperacillin, 9.4% to piperacillin-tazobactam and 0% to polymyxin B. Of the 505 isolates, 29 (5.74%) were found to be multidrug-resistant; these were most commonly isolated from respiratory tract specimens of patients in surgical units, followed by respiratory tract specimens in patients in medical units.
CONCLUSIONS: The data in this study showed low rates of antibiotic resistance among P. aeruginosa isolates. Combinations of aminoglycosides plus beta-lactams or quinolones should be the appropriate choice for empirical therapy in P. aeruginosa infections. Active antibiotic susceptibility testing and surveillance should be continued in order to curtail the problem of antibiotic resistance.
Pseudomonas aeruginosa is the third most common pathogen causing nosocomial infections. The objective of this study was to investigate the antimicrobial resistance profiles and genetic diversity of hospital isolates of P. aeruginosa and to investigate the presence of several resistance genes and integrons.
This study was carried out to evaluate the antibacterial activity of aqueous and organic extracts of Thymus capitatus L. (Lamiaceae) leaves and stems. Dried ground powder leaves and stems were extracted with water (aqueous extracts), ethanol, dichloromethane and hexane (Soxhlet extracts). The antibacterial activity of these extracts was evaluated against bacteria using disc diffusion method. The result obtained showed that the leaves had stronger antibacterial activity than the stems extracts. The ethanolic extract had the highest yield products and the high antibacterial activity than all other solvents. The results suggest that essential oil as non-polar organic compounds could be the main active compounds in this plant. Therefore the antibacterial activity of leaves ethanol extracts (LEE) was compared with essential oils leaves extracts (LEO) of T. capitatus. The LEO showed greater antibacterial activity than LEE. The LEO showed a broad spectrum of antibacterial activity and the Pseudomonas aeruginosa was the most sensitive bacteria.
Ninety (n = 90) imipenem-resistant Pseudomonas aeruginosa (IRPA) clinical isolates collected randomly during 2005 to 2008 from University Malaya Medical Center were assessed for the presence of different variants of metallo-beta-lactamase (MBL) genes. Polymerase chain reaction (PCR) assay detected 32 (n = 32) MBL gene PCR-positive isolates with the presence of bla(IMP) gene in 14 (n = 14) and bla(VIM) in 18 (n = 18) isolates. Four allelic variants, bla(IMP-7) (12 isolates), bla(IMP-4) (2 isolates), bla(VIM-2) (17 isolates), and bla(VIM-11) (1 isolate), of MBL genes were identified. This study is the first report of detection of bla(IMP-4), bla(VIM-2), and bla(VIM-11) MBL genes from IRPA clinical isolates in Malaysia.
Study site: University Malaya Medical Center (UMMC)
The antibacterial activity of Vernonia cinerea (L.) extract was investigated using the broth dilution method. The extract showed a favorable antimicrobial activity against Pseudomonas aeruginosa with a minimum inhibition concentration (MIC) value of 3.13 mg/mL. V. cinerea extract at (1/2), 1, or 2 times the MIC significantly inhibited bacterial growth with a noticeable drop in optical density (OD) of the bacterial culture, thus confirming the antibacterial activity of the extract on P. aeruginosa. Imaging using scanning (SEM) and transmission (TEM) electron microscopy was done to determine the major alterations in the microstructure of the extract-treated P. aeruginosa. The main abnormalities noted via SEM and TEM studies were the alteration in morphology of the bacterial cells. The main reason for this destruction was the severe alterations of the cell wall with the formation of holes, invaginations, and morphological disorganization caused by the extract. The authors conclude that the extract may be used as a candidate for the development of antimicrobial agents.
Methanol extract of the Gracilaria changii has been screened for antimicrobial activity against Pseudomonas aeruginosa. Antimicrobial activities were carried out using disc diffusion assay and broth dilution method against P. aeruginosa. The methanol extract of G. changii showed a good antimicrobial activity against P. aeruginosa with MIC (Minimum Inhibitory Concentration) value of 6.25mg/ml. Exposure of P. aeruginosa cells to 6.25mg/ml of methanol extract of G. changii resulted in complete inhibition of the bacterial cells. The main abnormalities noted via SEM and TEM studies were the alterations in morphology and cytology of the bacterial cells. The main reason for this deterioration was discussed. The effect of the methanol extract on the growth profile for the bacteria was also done and confirmed the bactericidal effect of the G. changii methanol extract on P. aeruginosa by changing the normal growth profile of P. aeruginosa. In an acute toxicity study using mice, the median lethal dose (LD(50)) of the extract was greater than 2000 mg/kg, and we found no pathological changes in macroscopic examination by necropsy of mice treated with extract. We conclude that G. changii might be safely used as an antimicrobial agent.
Full-thickness burn wounds require excision and skin grafting. Multiple surgical procedures are inevitable in managing moderate to severe full-thickness burns. Wound bed preparations prior to surgery are necessary in order to prevent wound infection and promote wound healing. Honey can be used to treat burn wounds. However, not all the honey is the same. This study aims to evaluate the wound contraction and antibacterial properties of locally-produced Tualang honey on managing full-thickness burn wounds in vivo.
The major l-amino acid oxidase (LAAO, EC 1.4.3.2) of king cobra (Ophiophagus hannah) venom is known to be an unusual form of snake venom LAAO as it possesses unique structural features and unusual thermal stability. The antibacterial effects of king cobra venom LAAO were tested against several strains of clinical isolates including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli using broth microdilution assay. For comparison, the antibacterial effects of several antibiotics (cefotaxime, kanamycin, tetracycline, vancomycin and penicillin) were also examined using the same conditions. King cobra venom LAAO was very effective in inhibiting the two Gram-positive bacteria (S. aureus and S. epidermidis) tested, with minimum inhibitory concentration (MIC) of 0.78μg/mL (0.006μM) and 1.56μg/mL (0.012μM) against S. aureus and S. epidermidis, respectively. The MICs are comparable to the MICs of the antibiotics tested, on a weight basis. However, the LAAO was only moderately effective against three Gram-negative bacteria tested (P. aeruginosa, K. pneumoniae and E. coli), with MIC ranges from 25 to 50μg/mL (0.2-0.4μM). Catalase at the concentration of 1mg/mL abolished the antibacterial effect of LAAO, indicating that the antibacterial effect of the enzyme involves generation of hydrogen peroxide. Binding studies indicated that king cobra venom LAAO binds strongly to the Gram-positive S. aureus and S. epidermidis, but less strongly to the Gram-negative E. coli and P. aeruginosa, indicating that specific binding to bacteria is important for the potent antibacterial activity of the enzyme.
A methanol-soluble extract of the bark of Myristica cinnamomea was found to exhibit anti-quorum sensing activity, and subsequent bioassay-guided isolation led to the identification of the active compound malabaricone C (1). Compound 1 inhibited violacein production by Chromobacterium violaceum CV026 when grown in the presence of a cognate signaling molecule, N-3-oxohexanoyl-homoserine lactone. Furthermore, 1 inhibited the quorum sensing-regulated pyocyanin production and biofilm formation in Pseudomonas aeruginosa PAO1. These results suggest that the anti-quorum sensing activity of 1 and related molecules should be investigated further.
Silver nanoparticles (AgNPs) of a small size were successfully synthesized using the wet chemical reduction method into the lamellar space layer of montmorillonite/chitosan (MMT/Cts) as an organomodified mineral solid support in the absence of any heat treatment. AgNO3, MMT, Cts, and NaBH4 were used as the silver precursor, the solid support, the natural polymeric stabilizer, and the chemical reduction agent, respectively. MMT was suspended in aqueous AgNO3/Cts solution. The interlamellar space limits were changed (d-spacing = 1.24-1.54 nm); therefore, AgNPs formed on the interlayer and external surface of MMT/Cts with d-average = 6.28-9.84 nm diameter. Characterizations were done using different methods, ie, ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence spectrometry, and Fourier transform infrared spectroscopy. Silver/montmorillonite/chitosan bionanocomposite (Ag/MMT/Cts BNC) systems were examined. The antibacterial activity of AgNPs in MMT/Cts was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria, ie, Escherichia coli, E. coli O157:H7, and Pseudomonas aeruginosa by the disc diffusion method using Mueller Hinton agar at different sizes of AgNPs. All of the synthesized Ag/MMT/Cts BNCs were found to have high antibacterial activity. These results show that Ag/MMT/Cts BNCs can be useful in different biological research and biomedical applications, including surgical devices and drug delivery vehicles.