Determination of Colistin Resistance by Simple Disk Diffusion Test Using Modified Mueller-Hinton Agar

BACKGROUND: Colistin has become a last-resort antibiotic for the management of multidrug-resistant gram-negative bacteria. The disk diffusion test is cheap and easy to perform but may be unreliable for colistin susceptibility testing due to poor diffusion of the large colistin molecule. An improved agar diffusion test would increase the reliability of colistin susceptibility testing. This study aimed to modify Muller-Hinton agar (MHA) to improve colistin diffusion in agar.METHODS: MHA was modified by reducing the agar concentration from 100% to 30% and supplementing with protamine. We tested 60 gram-negative clinical isolates of Pseudomonas aeruginosa (N=27) and Acinetobacter calcoaceticus-baumannii complex (N=33). Disk diffusion test results were interpreted based on minimum inhibitory concentrations determined by broth microdilution.RESULTS: The modified MHA yielded the best performance metrics, including 94.7% sensitivity, 100% specificity, and an area under the curve of 0.995 (95% confidence interval, 0.982–1.000), P<0.001, at a cut-off point of 13 mm.CONCLUSIONS: A reduction of the agar concentration from 100% to 30% and the addition of protamine improved colistin diffusion in agar and allowed routine colistin susceptibility testing in a clinical microbiology laboratory, but should be handled with caution.

Bacteriological Profile and Antibiotic Susceptibility Patterns in Neonatal Septicaemia in Tertiary Care Hospital

Introduction: Neonatal septicaemia has great role in morbidityand mortality among neonates. Neonatal mortality rate hasbeen reported in India as 17 per 1000 live births as per 2016-17 data. Neonatal septicaemia may be of early onset or lateonset depending of the age of the neonates. The mostcommon bacterial agents involved are Group B Streptococcus,Klebsiella pneumoniae, CoNS, Streptococcus pneumoniae,Haemophilus influenzae etc. Diagnosis is done by manymethods but the most important and absolute mode ofdiagnosis is blood culture.Aims and Objectives: The present study is done for thedetection of bacteriological profile and their antibioticsusceptibility pattern in case of neonatal septicaemia. Earlydiagnosis and specific treatment can save the lives of manyneonates who are suffering from neonatal septicaemia.Materials and Methods: The material used for the diagnosis isvenous blood of the suspected neonates. Blood culture methodis used for the diagnosis of Neonatal septicaemia. Repeatedsubculture is done on Blood agar, Nutrient agar, andMacConkey agar plates. Confirmation of organism is donethrough different biochemical tests. The antibiotic susceptibilitytesting was performed on Muller Hinton agar (MHA) by KirbyBauer disc diffusion method for bacterial isolates, as perclinical and laboratory standards institute (CLSI) guideline.Results: Total 206 cases of suspected neonatal septicaemiawere investigated in which 142 cases are found positive. Mostcommon organism isolated was Klebsiella pneumoniae(39.44%) than Staphylococcus aureus (33.8%), otherorganisms are Escherichia coli (9.86%), CoNS (8.48%),Pseudomonas (5.63%), Enterococcus (2.82%) etc. overallincidence of Gram negative organism (54.93%) was more thanGram positive organism (45.07%). As far as antibioticsensitivity pattern was concerned most of the organism were100% sensitive to imipenem, meropenem and colistin B andresistant to Ampicillin.Conclusion: Gram negative isolates were more common thanGram positive as the causative agents of neonatal sepsis. Themost common causative organism was Klebsiella pneumoniae.The other organisms isolated were Pseudomonas aeruginosa,Staphylococcus aureus, CoNS, etc. Most of the Gram negativeisolates were sensitive to Amikacin, Gentamycin, Ofloxacin andCiprofloxacin but were highly susceptible to Meropenem,Imipenem and Collistin-B. The Gram positive isolates werebetter sensitive to Amikacin, Cephalosporin, Ciprofloxacin andClindamycin but were less sensitive or resistant to Ampicillinand Erythromycin. They showed high susceptibility toTicoplanim, Linezolid, Vancomycin and Methicillin.

Screening of antibacterial activity, qualitative and quantitative analysis of phytochemicals in vitex trifolia.

The present focus of the study was to evaluate the antibacterial activity and phytochemical analysis in the medically important plant vitex trifolia leaf extract by using solvents like aqueous, methanol, acetone, benzene, petroleum ether. The plant vitex trifolia used for its phytochemical and pharmacological studies. In qualitative and quantitative analysis of vitex trifolia viz., alkaloids, saponin, tannin, phenols, terpenoids, flavonoids, steroids, were determined using standard methods. Vitex trifolia leaves were collected, air-dried and soxhlet extracted by using standard method. These extracts were then tested for antimicrobial activity using disc diffusion method. Vitex trifolia showed highest antibacterial activity (IZ= 0.5cm in acetone extract, IZ = 0.75 in ethanol extract) against Bacillus subtilis and (IZ= 0.15cm in acetone extract, IZ = 0.25cm in ethanol extract, IZ = 0.35cm in aqueous extract) against Escherichia coli. Results concluded that the phytochemicals of leaves extract of vitex trifolia has the potential to act as a antibacterial agent.

Candida prevalence and its antifungal susceptibility in various clinical specimens in tertiary care center.

Background: The purpose of this study was to isolate the Candida spp. & examine their susceptibility to antifungal drugs from various clinical specimens. One hundred fifty isolates of Candida spp. were included in this study. Clinical history revealed that all patients were on systemic broad spectrum antibacterial drugs. Materials and Methods: Candida spp. was differentiated by germ tube test, culture characteristics on special media for fungus, sugar fermentation, sugar assimilation and growth on corn meal agar. Antifungal drug susceptibility testing against Fluconazole, Ketoconazole, Itraconazole, Voriconazole, Nystatin and Amphotericin B were done on basis of CLSI guidelines on Methylene blue containing Mueller Hinton Agar by disk diffusion method. Result: We found 52% and 48%, C.albicans & Non albicans candida spp., respectively. There were no resistance to Nystatin and Amphotericin B. C.albicans was more susceptible than Non albicans candida. Nystatin & Amphotericin B were susceptible to all isolated Candida spp. In present scenario, Fluconazole is most commonly used empirical antifungal drug, which is more effective to C.albicans than Non albicans Candida. Conclusion: Due to emergence of resistance in Azole group of antifungal among Non albicans candida, it should be mandatory to use antifungal drugs as per the susceptibility testing.