End of the Semester!!

This is the end of the semester! This means that this graduate project is ending, and this will be my last post. I hope that you have enjoyed reading them, and learned something along the way! I have enjoyed this class and was able to use what I learned in the first Microbiology class to use now!

Virology

This week in lecture, we briefly discussed quality in the lab. This mostly consisted of correct temperatures, control organisms, and other regulations that maitain proper conditions in the lab. The other topic we discussed was virology. This testing is not routinely done in the hospital laboratory. Viruses are obligate intracellular parasites, and do not multiply by binary fission like bacteria. they can only be seen with an electron microscope. Viruses contain a nucleic acid core, envelope, and glycoprotein spikes. In order to replicate, the virus can attach, penetrate, uncoat, replicate, assembly, and release. There are patterns of viral disease. These include acute infections, persistent infections, and slow infection. The methods used to detect viruses vary significantly depending on the lab. One of the major viruses we think of is HIV. The link below is a short video that gives a good overview of how the virus attaches and the integration. Enjoy!

HIV

Antibiotic Resistance and Quality

This week in class we discussed antibiotic resistance. This is a very real and scary problem in our society today. The bacterial resistance can be several mechanisms including inate, acquired, or genetic recombination. Beta -lactams have an interesting mechanism of resistnace where the target or binding site is altered. S. aureus resistance to multiple drugs is a major problem we see frequently. The following article discusses this issue in meat and poultry in the United States. S. aureus contaminated 47% of the samples, and  multidrug resistance was common among isolates (52%). S. aureus genotypes and resistance profiles differed significantly among sample types, suggesting food animal–specific contamination. This is a problem that many people are begining to recognize and try to take action. The Washington Post published an article saying the American Medical Association and the Infectious Diseases Society of America have called on the FDA to ban feeding antibiotics to healthy animals. Testing for the extended spectrum beta-lactamases include both screenng and confirmatory tests. The most important things to remember is the physician will want to know what the bacteria is reststant and susceptile to, and treat the patiet quickly and effectively! Community acquired MRSA is more prevalent, and with football season approaching, athletes should remember to protect themselves!

http://cid.oxfordjournals.org/content/52/10/1227.full.pdf+html
http://www.washingtonpost.com/politics/groups-sue-fda-to-stop-addition-of-antibiotics-in-livestock-feed/2011/05/25/AGxfbVBH_story.html

Lab susceptability

This week in lab we were able to perform out own susceptibility tests. These tests included an agar disk diffusion on Staph epidermidis, an MIC combo plate, E test, CHROMagar, and Nitrocefin disk for beta-lactamase. For the agar diffusion, the plates were streaked and disks were placed and incubated overnight. The next day the zone was measured around each disk. Using given values, susceptibility was determined.

Then, a Microscan gram negative MIC panel was done. The pan is innoculated and incubated to be read the following day. Each well is read for growth or no growth, and each MIC is circled on the report sheet.

The CHROMAgar was streaked with the specimen swab and icubated. The plates were then read and interpreted. If mauve colonies were present, it is positive.

Lastly, the Nitrocefin disk test was performed. The red color seen below indicates a positive result and means the organism is resistant to penacillin and cephalosporin.

Susceptibility Testing Lecture

This week in class we discussed antimicrobial action and antimicrobial susceptibility tests. This is very important for both patients and physicians in order to effectively treat infections. The mechanism of activity varies among agents and some commons ones include Inhibition of cell wall synthesis, disruption of cell membrane, inhibition of nucleic acid synthesis (RNA or DNA), interference with essential , metabolites (ex. folic acid pathway), and Inhibition of protein synthesis (binds to 30S or 50S ribosomal subunit). Beta Lactams act on the cell wall, while glycopeptides inhibit cell call synthesis. Vancomycin is a popular example. Interfering with protein synthesis is also a mechanism, and this is done by tetracyclines, aminoglycosides, and macrolides. In order to detect susceptibility, several methods can be used. Some of these include broth dilutions, microdolutions, and agar dilutions. Additionally, there are automated systems that are available. In order to determine susceptibility, we can use an E test, MBC, MIC, and the Schlicter Test.

The following link is to an article containing a case history of a 79-year-old man with end-stage renal disease due to hypertension. The man had positive blood cultures for MRSA that was resistant to vancomycin. Read the article to learn more!

http://www.nejm.org/doi/full/10.1056/NEJM199902183400704

Skin, wounds, and Micobacterium lecture

Skin infections can be caused by many agents. Some of these are very serious including MRSA. These infections can be hospital or community acquired. Wounds and abscesses are also problems for many people that may be due to bites, burns, or injury. Some organisms involved may be S. aureus, S. pyogenes, Enterococcus, E. coli, Proteus, P. aeruginosa, and anaerobes. Eye infections are also common among some people. Some symptoms include swelling, exudates, and burning. The most common isolates are S. epidermidis, Lactobacillus, Corynebacterium, and P. acnes. Normal flora can vary in individuals, so each isolate can be identified. Ear infections can be seen in several forms including swimmer’s ear (P. aeruginosa), acute localized otitis externa (S. aerus), and chronic otitis externa (P. aeruginosa, anaerobes). Usually these are plated onto SBA, Choc, and MAC.

Mycobateria

http://www.msnbc.msn.com/id/42788111/ns/health-infectious_diseases/t/eating-armadillos-blamed-leprosy-south/

is a very serious disease that should be taken very seriously and when working with suspected cases, extreme caution should be taken. The main mode of transmission is inhalation, and as a result outbreaks are seen among people living in close quarters. There are 5 stages of infection, and most cases do not progress to the advanced stage. NTMs are non-tuberculosis mycobacterium, and these can be grouped into slow growers, and rapid growers. One very interesting noncultivable NTM is M. leprae, which causes leprosy. This has been seen recently in parts of the South acquired by people eating armadillos. Follow thw link below to the story.

Lecture GI and Genital

This week in lecture we discussed GI and genital tract infections. There are several diseases associated with the GI tract including gastroenteritis, enteritis, infectious diarrhea, and antibiotic associated diarrhea. An interesting fact that I learned from this lecture is that E. coli can be pathogenic or normal flora. The different pathogenic forms are ETEC, EPEC, EIEC, EAEC, and EHEC. Most isolates are the 0157: H7 strain. Salmonella, Shigella, and Camplobacter are all pathogens that are isolated in the lab. KIA, LIA, and Urea are used to ID and differentiate Shigella and Salmonella. When these are identifies, serotyping is done to identify the species. There are other pathogens and anaerobes that are identifies, but they follow procedures previously covered.

Genital Tract infections are commonly caused by sexually transmitted diseases. N. gonorrhoeae, C. trachomatis, HPV, HIV, Trichomonas, and C. albicans are among the most common. There are many diseases associated with the agents, and according ot symptoms a physician will order testing accordingly. A cervical swab should be put in transport media, charcoal cotton or rayon. Specimens for Chlamydia should be transported in 2 SP medium, on ice. Gram stains, wet preps, and direct antigen tests can all be done depending on what organism is suspected. The cell culture is still considered the gold standard. Selective media for a GC culture is MTM, Martin Lewis, and NYC.

Cervical and Fecal Cultures

This week in lab we performed GI and genital tract cultures. The cervical culture was plated onto SBA, Choc, and MTM. There were 2 colonies on SBA and choc, but only one on MTM. Because isolate 1 grew on MTM as pinpoint, small, translucent colonies Neisseria was suspected. The gram stain showed gram negative diplococci, oxidase positive, and a bacticard was pro positive confirming Neisseria gonorrhoeae. The other isolate was catalase positive and gram stained diptheroids and were identified as Corynebacterium.

On the feces culture, there was no growth on CVA while XLD, MAC, and SBA had 2 isolates. On XLD, the colonies were yellow (lactose positive), SLF on MAC, a large, white, mucoid beta hemolytic colonies on SBA. This was presumed to be E. coli ad normal flora. Isolate 2 had clear colonies on XLD and MAC, and large gray beat hemolytic mucoid colonies on SBA. Because there was no black seen in the center of the colonies, KIA was alk/a, LIA was purple/ yellow, and urea negative, Shigella was suspected. The serotyping identified it as Shigella flexneri. The case given with this specimen was a 4 year old who attended daycare who presented with vomiting, diarrhea, fever, lethargy, and irritability. His stool had bloody streaks and had numerous WBCs. Shigella is commonly acquired via the fecal oral route and is common in daycare settings.

The following link is a case history on Shigella flexneri. http://www.jpma.org.pk/PdfDownload/995.pdf