The Resistance Spectrum Of Enterobacteriaceae, An Anal Culture Isolate

Abstract-The gram-negative bacteria Serratia marcescens has gained attention in recent years for its tendency to cause nosocomial infections in humans, as well as its development of antibiotic resistance. Antibiotic resistance in a bacterium that is harmful to humans can be concerning as it can result in infections that are difficult to treat. In order to find out more about the growing antibiotic resistance of S. marcescens, this experiment used the disc diffusion method to test the susceptibility of S. marcescens to two varieties of antibiotics that were known to have success against some gram-negative bacterium: streptomycin and ampicillin. These antibiotics were, respectively, an aminoglycoside and a beta-lactam. The experiment tested which of the two that S. marcescens had developed more of a resistance to. The zones of inhibition of the discs were significantly larger for discs treated with streptomycin compared to discs treated with ampicillin. This led to the conclusion that S. marcescens is less resistant to streptomycin than to ampicillin.

E.coli outbreaks have steadily grown over the last few decades. An expansion in big farming has led to E. coli not only being found in meat, but vegetation as well, due to waste runoff. This has increased our need for adequate antibiotics that can fight bacteria, like E. coli. The best way to pinpoint which antibiotics work is by measuring their ability to create antimicrobial agents or zones of inhibition. When a paper disc that has been saturated in an antibiotic is inserted in a solution of E.coli and medium, the zone of inhibition will be noted as the clear ring that forms around the disk. The antibiotics efficacy is then determined by measuring each disk zone of inhibition, and comparing these measurements to the zone measurements of an untreated specimen. If an antibiotic is to be deemed sufficient for treating E. coli it should show a zone of inhibition that is at least double the size of the untreated specimen.

Smith H. 1969. TRANSFER OF ANTIBIOTIC RESISTANCE FROM ANIMAL AND HUMAN STRAINS OF ESCHERICHIA COLI TO RESIDENT E. COLI IN THE ALIMENTARY TRACT OF MAN. Science Direct [Internet]. [Cited 2015 Dec 1]. Available from:

I believe that the test that we performed was not effective in distinguishing between bacteriostatic and bactericidal agents because there is no distinguishing characteristics between the zone of inhibition of a bacteriostatic agent and a bactericidal agent.

The problem that this experiment is trying to solve is whether or not Staphylococcus epidermidis is resistant or susceptible to various antibiotics. The independent variable for the experiment is the type of antibiotic being used against the bacteria(Ampicillin, Streptomycin, Penicillin, and Tetracycline). The

Penicillin (P-10) was measured at 0mm in diameters. There was no susceptibility. Therefore, with the zone size as 0, Escherichia coli was resistant to penicillin.

The overconsumption of antibiotics is a big contribution to drug resistance and is why users should know what happens with the repeated use of these drugs. Even though some bacterial mutation occurs naturally, human use of antibacterial is the cause of higher-levels of resistance (Alliance for the Prudent Use of Antibiotics 2014). Bacteria mutate either by genetic mutation or by receiving the defensive agent. During an infection bacteria multiply naturally within the body and when exposed to antibiotics, bacteria have an opportunity to adapt to the drug (Alliance for the Prudent Use of Antibiotics 2014). During this period of

The independent variable for the Antibiotic Resistance Lab was the strain of E. Coli, the strain that we tested is called E. Coli K-12. The dependent variable was the amount of E. Coli that was resistant to triclosan, i.e. the size of the zone of inhibition. This lab was experimental because we were physically dealing with the variables. We created the environment for the E.Coli to either adapt to or not.

This measure of the inhibition zone indicated the susceptibility or resistance of the bacterium to the antibiotic. And by comparing the experimentally determined zone diameters with known diameters, susceptibility patterns known

The Kirby-Bauer disc diffusion method was used to examine sensitivity of antimicrobial agents, it fast and simple way to find an antibiotic to use for a treatment of some type of infection. This method uses a plate that has been cover with the testing bacteria and small disc covered in the antibiotic to see if the bacteria is able to around the disc, it will make an even circle around the disc which is the zone of inhibition. This zone of inhibition diameter can be measured and compared to the interpretation chart to find the antibiotic sensitivity or resistance. When the zone of inhibition is very small or nonexistent this shows that bacteria is resistant to the antibiotic and will not work against this bacterial infection. If the zone is

The goal of antimicrobial susceptibility testing is to predict the success or failure of antibiotic therapy. Tests are performed and measure the growth response of an isolated organism to a selected drug or medicine. The results of antimicrobial susceptibility testing ought to be combined with clinical information and skill once choosing the foremost appropriate antibiotic. There are many factors to think about in selecting an appropriate antibiotic for treatment of a bacterial infection. The foremost basic of those is whether the causative organism is prone to a selected antibiotic, and the way much of that antibiotic are necessary to inhibit or kill the organism. Whereas we tend to do

Ceftazidime is a third generation cephalosporin antibiotic used to treat a number of bacterial infections, particularly Pseudomonas and other Gram negatives, and its activity relies on binding of essential penicillin-binding proteins (PBPs) (1). Despite its effectiveness against certain bacteria, there have been reports of rapidly increasing incidences of antibacterial resistance to ceftazidime caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (2). Recently, a new beta-lactam/beta-lactamase inhibitor combination, ceftazidime-avibactam (AVYCAZ) has shown to have “in vitro activity against Enterobacteriaceae in the presence of some beta-lactamases and extended-spectrum beta-lactamases” and is FDA-approved for treating complicated intra-abdominal infections as well as complicated urinary tract infections (1). Due to the resistance frequency of inpatient Enterobacteriaceae isolates at the University of Washington Medical Center (4), susceptibility testing of Ceftazidime and Ceftazidime-Avibactam are crucial to ensure antibiotic treatment efficacy and to take action to reduce the spread of multi-drug resistant bacteria in a hospital setting.

The Escherichia coli (E. coli) is a facultative gram negative rod-shaped bacterium. It is commonly seen in the intestinal tract of humans and animals. E. coli is the most rampant member of the large bacterial family, Enterobacteriaceae, (Sorumand, 2001). This intestinal bacterium can be easily spread in diverse ecosystems. For this purpose, faecal E. coli is noted to be a key indicator for the selective density applied by the use of antimicrobials on intestinal inhabitants of bacteria (van den Bogaard and Stobberingh, 2000). E. coli and associated bacteria comprise about 0.1% of gut flora, and faecal-oral transmission is the main route through which pathogenic strains of the bacterium cause

The Enteroccocci species are a group of gram-positive, round shaped, facultative anaerobic cocci bacteria that are normally present in the human intestines and in the female genital tract. These bacteria can also be found within the environment. They are resistant to several antibiotics, but in the past, physicians could rely on the drug vancomycin to effectively treat enterococcal infections. A couple decades ago doctors and researchers discovered that a new strain was being formed and that some enterococci have become resistant to vancomycin (reference). Vancomycin resistance is acquired when a sensitive Enterococcus acquires a special piece of DNA called a plasmid that permits the bacteria to become resistant to vancomycin hence the term vancomycin-resistant enterococci (VRE). The two main species that cause problems are vancomycin-resistant Enterococcus faecium and vancomycin-resistant Enterococcus faecalis. E.faecium is the most common species of VRE. Unlike E.coil these bacteria do not have the same genus as other common fecal bacteria. VRE can be spread from person to person and are an increasing problem in hospitals and chronic-care facilities. Approximately 30% of all enterococcal infections are now caused by vancomycin-resistant strains (VRE).

The goal of this experiment is to determine whether different antibiotics will inhibit bacterial growth of S. Aureus. The hypothesis is that all three antibiotics used (penicillin, gentamicin, and kanamycin) will inhibit growth. If a zone of inhibition is observed around each antibiotic disk, then the hypothesis will be supported - demonstrating the bacteria’s susceptibility to the subject antibiotics. By demonstrating the efficacy of various different antibiotics and comparing them to one another in context of the target bacteria, combined with the gram stain results of S. Aureus, the results may be further analyzed and explained.