Investigating Enterococcus faecalis’s structures and resistances to antibiotics
Introduction
Bacteria’s phenotype is commonly described as gram-negative or gram-positive from conducting a gram stain. A bacterium that is gram-negative tends to have cells composed of a thin peptidoglycan layer, and a gram stain of gram-negative bacteria are seen as red or pink through a microscope (Smith and Hussey, 2005). On the other hand, a bacterium that is gram-positive will have cells made of a thick peptidoglycan layer, and the gram stain of a gram negative bacteria would be seen blue or purple (Smith and Hussey, 2005). In particular, Enterococcus faecalis is a gram-positive bacterium which has been found in many infections in the urinary tract, surgical, …show more content…
We measured the zone of inhibition after a week to observe which antibiotic Enterococcus faecalis is most sensitive to. My hypothesis is that Enterococcus faecalis will have varying levels of sensitivity to different types of antibiotics by expressing different size of zone of inhibition. If neomycin, tetracycline, and erythromycin are individually applied to a colony of Enterococcus faecalis, then the zone of inhibition will be highest to lowest in the order of neomycin, erythromycin, and tetracycline. I based this order based on my research that suggest tetracycline would be less effective because Enterococcus faecalis has found to be resistant to tetracycline in 58% of the isolates (McBride et al., 2007). Whereas, erythromycin should be slightly more effective than tetracycline because the study indicated that only 38% of isolates were resistance as compared to 58% for tetracycline. (McBride et al., 2007). Neomycin was rank to be the most effective because a break out of high-level gentamicin resistant Enterococcus faecalis was noted to be not resistant to neomycin in a Norwegian hospital(Wendelbo et al., 2003). A control treatment was also assigned by not adding any antibiotic. If no antibiotic is applied to the Enterococcus faecalis , then there should be no zone of inhibition for the control group. Furthermore, …show more content…
Figure 2 and Figure 3 both show the average zone of inhibition for neomycin was 12.4 mm and the average zone of inhibition for tetracycline is 15.8 mm. Lastly, the control group had an average zone of inhibition of zero mm as presented in the figure 2 (table) and figure 3 (graph) suggesting it was the antibiotics actually had an effect on the zone inhibition of the bacteria. My hypothesis was supported because Enterococcus faecalis was very sensitive to all three antibiotics by having a zone of inhibition greater than 10 mm. However, my predictions on the order of highest to lowest zone of inhibition for the three antibiotics were proven wrong. Instead of the order neomycin, erythromycin, and tetracycline, results from figure 3 shows erythromycin, tetracycline, and then neomycin in the order of highest zone of inhibition to lowest. These predictions that was base on previous experiments from (Mcbride et al 2007) and (Wendelbo et al., 2003) were falsified. There is however limitation to my experiment because of the small sample size that consisted only of five agar trays. If more trials were done, we may get results closer to the sources. Since erythromycin is being supported by my data to be a more effective antibiotic, doctors can prescribe this antibiotic to patients with
Introduction
Bacteria’s phenotype is commonly described as gram-negative or gram-positive from conducting a gram stain. A bacterium that is gram-negative tends to have cells composed of a thin peptidoglycan layer, and a gram stain of gram-negative bacteria are seen as red or pink through a microscope (Smith and Hussey, 2005). On the other hand, a bacterium that is gram-positive will have cells made of a thick peptidoglycan layer, and the gram stain of a gram negative bacteria would be seen blue or purple (Smith and Hussey, 2005). In particular, Enterococcus faecalis is a gram-positive bacterium which has been found in many infections in the urinary tract, surgical, …show more content…
We measured the zone of inhibition after a week to observe which antibiotic Enterococcus faecalis is most sensitive to. My hypothesis is that Enterococcus faecalis will have varying levels of sensitivity to different types of antibiotics by expressing different size of zone of inhibition. If neomycin, tetracycline, and erythromycin are individually applied to a colony of Enterococcus faecalis, then the zone of inhibition will be highest to lowest in the order of neomycin, erythromycin, and tetracycline. I based this order based on my research that suggest tetracycline would be less effective because Enterococcus faecalis has found to be resistant to tetracycline in 58% of the isolates (McBride et al., 2007). Whereas, erythromycin should be slightly more effective than tetracycline because the study indicated that only 38% of isolates were resistance as compared to 58% for tetracycline. (McBride et al., 2007). Neomycin was rank to be the most effective because a break out of high-level gentamicin resistant Enterococcus faecalis was noted to be not resistant to neomycin in a Norwegian hospital(Wendelbo et al., 2003). A control treatment was also assigned by not adding any antibiotic. If no antibiotic is applied to the Enterococcus faecalis , then there should be no zone of inhibition for the control group. Furthermore, …show more content…
Figure 2 and Figure 3 both show the average zone of inhibition for neomycin was 12.4 mm and the average zone of inhibition for tetracycline is 15.8 mm. Lastly, the control group had an average zone of inhibition of zero mm as presented in the figure 2 (table) and figure 3 (graph) suggesting it was the antibiotics actually had an effect on the zone inhibition of the bacteria. My hypothesis was supported because Enterococcus faecalis was very sensitive to all three antibiotics by having a zone of inhibition greater than 10 mm. However, my predictions on the order of highest to lowest zone of inhibition for the three antibiotics were proven wrong. Instead of the order neomycin, erythromycin, and tetracycline, results from figure 3 shows erythromycin, tetracycline, and then neomycin in the order of highest zone of inhibition to lowest. These predictions that was base on previous experiments from (Mcbride et al 2007) and (Wendelbo et al., 2003) were falsified. There is however limitation to my experiment because of the small sample size that consisted only of five agar trays. If more trials were done, we may get results closer to the sources. Since erythromycin is being supported by my data to be a more effective antibiotic, doctors can prescribe this antibiotic to patients with