A disk-diffusion test using E. coli gave the following results:  Disinfectant         Zone of inhibition (diameter in mm)       A                                    15       B                                    2.0       C                                    10       D                                    5   In the table above, which compound was the most effective against E. coli?       A) A       B) B           C) C       D) D                       E) The answer cannot be determined based on the information provided.

If a student would like to examine if an bacterial organism is capable of using starch, which of the following classes of medium would the student be using? A) A medium classified as differential B) A medium classified as defined C) A medium classified as selective D) A medium classified as minimal E) A medium classified as rich

From a 5% normal saline (NaCl) solution, take 2 ml and dilute it 1:5. Take 5 ml of this solution and dilute it 1:10. A 2:100 dilution is made from this last solution. Determine: a) How many times less concentrated is the 2nd dilution than the original? b) What is the dilution factor in each step of the series and what is the final volume of each dilution? c) How many grams of NaCl will be in 1 ml of the last solution?

The Kirby-Bauer test examines the effectiveness of antibiotics and disinfectants or antiseptics on separately plated bacteria. Which of the following Zones of Inhibition (ZOI) measurements on a plate of Klebsiella pneumoniae shows the strongest inhibition of the bacterium's growth?   a) Penicillin, 7 mm ZOI b) Actinomycin, 9 mm ZOI c) Tetracycline, 26 mm ZOI d) Chloramphenicol 2 mm ZOI e) Streptomycin, 23 mm ZOI

what does a negative result mean in an oxidase test?Select all that applies a)The bacteria may undergo anaerobic respiration b)The bacteria may have a cytochrome C oxidase c)The bacteria may undergo aerobic respiration d)The bacteria will not have cytochrome C oxidase e)None of the anwers are correct

Material (wound discharge) from a patient with suspected anaerobic wound infection was sent to the bacteriological laboratory. It is necessary to isolate a pure culture of anaerobic bacteria. 1. What principle of isolation of pure culture of anaerobic microorganisms will be applied? 2. What methods of creating anaerobic conditions with the participation of aerobic microorganisms are known? 3. What are the methods of controlling anaerobic conditions?

The Petri Dish method is used in microbiology to raise bacteria in: a) rapid growth b) pure culture c) septic environment d) all of the above 2. What is the difference between antiseptic and sanitization?3. In order to prevent any kind of contamination the medium must be _________ before placing it in the Petri dish. a) lyophilized b) pasteurized c) autoclaved d) distille

The data below were obtained for the growth of a pure culture of Escherichia coli in nutrient broth at a temperature of 37°C.   Determine (1) the specific growth rate and (2) generation time of E. coli and the duration of the (3) lag and (4) log (or exponential) phases. (ln 2 = 0.693)   Time (h)               0        1        2        3        4        8       16      32 Bacterial No./mL 104.1  103.9  104.4  105.5  106.5  107.7  108.0  107.6

(c) Public health scientists wanted to investigate the effect of ionising radiation on the growth of Salmonella typhimurium in the presence of antibiotics. They grew bacterial colonies of Salmonella typhimurium in petri dishes labelled A, B and C. The Petri dishes were kept at 36°C for 48 hours, with scientists observing the bacteria every 24 hours. The results for this investigation are below. Petri dish A B с Treatment Was subjected to ionising radiation followed immediately by a dose of antibiotic X An equal amount of antibiotic X was added (as was added to Petri dish A) Was given neither ionising radiation nor antibiotic X After 24 hours Small spots of growth on surface No growth Growth across whole surface After 48 hours (ii) Identify the purpose of petri dish C. Large spots of growth on surface No growth Growth across whole surface (i) Explain the effect of the ionising radiation on the bacteria. (iii) Explain why scientists must continue to develop new antibiotics.