Diagnostic Microbiology and the Microflora Inhabiting the Human Body - Lab Report Example

Diagnostic Microbiology and the Microflora Inhabiting the Human Body Introduction: The human body is home to approximately 200 species of microflora, the maximum population inhabiting the GIT, next skin and then mouth. Most of these are commensals or mutualistic, however, some of these become pathogenic in cases of previous trauma or injury; or when immune system is weakened because of some reason; i.e. when normal defenses of the body are down. Body can also be infected by other pathogenic microbes from the environment, upon exposure to these microbes e.g. Salmonella sp. Such infections invoke responses from the body which are more or less specific to the microbe involved and so are their response to different antibiomicrobial agents. Hence, to be able to provide effective treatment for these pathogens, it is imperative to identify them. Microbiology provides a vast collection of literature to help identify these microbes using morphological feature, biochemical tests and other techniques based on these two. The present experiment aims to identify the bacteria present in the vaginal swab and fecal samples, to check whether these species are normal for this part of body, or are indicative of infection. Discussion: VAGINAL SWAB 1 (V1): The bacteria isolated from vaginal swab 1 (V1) exihibited a negative gram reaction, and the cell were found to be rod shaped, suggesting that V1 is a gram negative bacilli. Further the bacteria showed round, flat, small, colonies, which had entire margins and were cream in colour. These results are suggestive of the bacteria being coliform and most probably being E. coli. V1 showed growth on MacConkey agar, along with change of colour. This result helps in the conclusion that V1 is a lactose fermenting gram neagtive bacilli, since MacConkey agar is selective only for gram negative bacteria and excludes all gram positive bacteria as bile salts in this media inhibit the growth of gram positive bacteria (Fluornoy, 1900). V1 therefore, belongs to the family of Enterobacteriaceae, and since it changes colour in MacConkey agar, it is again suggestive of E.coli, as among the gram negative bacteria, only E.coli is able to ferment lactose, and forms pink to red colonies (MacConkey, 1900). The absence of growth on mannitol salt agar and blood agar, further rules out the gram positive cocci. A positive result for catalase test, rules out the possibility of Streptococci (Chester, 1979), while a positive oxidase test indicates it to anaerobic and hence confirms it to belong to enterobacteriaceae (Baron, 1994). Thus V1 could be safely cocluded to belong to the group of lactose fermenting enterobacteriaceae. Next a positive indole test excludes Enterobacter, Serratia, most of the species of Klebsiella, Erwinia and Citrobacter, bringing down the list of probable bacteria to 4: Citrobacter diversus, Escherichia coli, Erwinia chrysanthem,i Klebsiella oxytoca (Isenberg & Sundheim, 1958). Next a negative citrate test confirms the bacteria to be E. coli, since among these 4 only E. coli is incapable of citrate utilization (Koser, 1924). E. coli is considered to be a resident of intestine of warm blooded animals and is normally non pathogenic. It is the most common gram-negative bacterium isolated in clinical laboratories and is the organism responsible for up to 70 to 95% of urinary tract infections (Mond et al., 1965). The antibiotics that can be used for treatment of E. coli are ampicillin, gentamycin and cepholothin, while E. coli is found to be resistant to clindamycin. VAGINAL SWAB 2 (V2): Bacteria isolated from vaginal swab 2 (V2) exihibited a positive gram reaction and was found to be a cocci dividing in multiple planes. This is indicative of a Staphylococci (Kloos & Schleifer, 1975). Further the irregular, curled, raised, medium and yellow colonies are suggestive of Staphylococcus aureus. The yellow colour of the colony rules out Staphylococcus epidermidis which has white colonies (Sandwik & Brown, 1965). Next, V2 shows alpha haemolytic activity, which again suggests it to be Staphylococcus. aureus, since none of the other staphylococci show haemolytic activity (Marcus et al., 1997). It shows no change in colour on MacConkey agar, which further substantiate the conclusion that it is a gram positive bacteria (Fluornoy, 1900). Growth on mannitol agar is indicative of V2 being either a Staphylococci or a Micrococci and the colour change of the media is indiactive of coagulase positive staphylococci, S. aureus (Koch, 1942). Next, a positive catalse test rules out the possibility of V1 being streptococci or enterococci, which are catalse negative (Taylor & Achanzar, 1972). Thus on the basis of V2 having the capacity to ferment mannitol it can safely be concluded that it is S. aureus. S. aureus is a normal flora found on the skin of humans and infection occurs only in cases of invasion through a lesion present on the skin due to a previous trauma. However, S. aureus has been isolated from Urinary tract of humans (Muder et al., 2006), and has been found to be a cause of asymtomatic UTI in some cases. S. aureus are resistant to most antimicrobial agents: ampicillin, chloramphenicol, tetracycline, cepholothin, clindamycin and can only be treated with gentamycin. FAECAL SAMPLE (F): Bacteris isolated from faecal sample (F), showed a gram negative reaction and is also a bacilli. This results excludes the gram positive and the cocci. The colonies are round, flat, entire, small and cream, which is suggestive of bacteria being either coliform, or Salmonella. Growth on blood agar showing no haemolysis rules out the possibility of Coagulase positive Staphylococci, an absence of growth on mannitol agar confirms too rules out the possibility of coagulase positive staphylococci and micrococci (Koch, 1942). A catalase positive result is indicative of F being enterobacteria (Taylor & Achanzar, 1972), while an oxidase negative test confirms it to be anaerobic enterobacteria (Baron, 1994). A negative indole test is suggestive of Salmonella (Isenberg & Sundheim, 1958). F further gives a negative reult for urease and profuse H2S production, confirming that it is Salmonella sp.(Clarke & Barret, 1987). The identification of F as Salmonella is further confirmed by the following results: VP negative, Lysine decarboxylase positve and citrate positive (Holt et al., 1994). Salmonella live in the intestinal tracts of warm as well as cold blooded animals and their presences in feacal samples is indicative of GIT infections or diarrohea. This can be due to ingestion of raw or contaminated food (Post, 1997). Salmonella have been found to be resistant to most of the antibiotics including ampicillin, gentamycin, tetracycline, cepholothin, clindamycin and even showed intermediate sensitivity to chloramphenicol. LAB REPORT FORM 4: The bacteria cultured from skin is a gram positive cocci and it could be a Staphylococcus, Micrococcus or Streptococcus. Since the cell arrangement is not clearly tetrad, Micrococcus can be ruled out (Holt et al., 1994). Staphylococcus and Streptococcus bacteria are normal flora of human skin. Of these Staphylococcus is the more common indigenous flora of the skin, so this microbe is most probably Staphylococcus, and since the colonies of this microbe are creamy, it could be S. epidermidis (Kloos & Schleifer, 1975). S epidermidis is one of the most predominant bacteria of human skin, and is present on almost every part of the body. It is highly adapted to its human host, and is an opportunistic pathogen, causing disease only when it can invade the body through a previously formed lesion or opening in the body (Huebner & Goldman, 1999). The bacteria cultured from mouth are also gram positive and cocci, thus suggesting a possiblity of either of the Staphylococcus, Streptococcus and Micrococcus. However, since the cell arrangement is not tetrad, again the Micrococcus bacteria is less probable (Holt et al., 1994). Next, the colonies being small, there is more probability of Streptococcus, which occur singly or in chains. Streptococcus sp. are very common in the mouth of humans, Streptococcus salivarius being the first to inhabit the mouth in newborns while Streptococcus mutans colonising with the appearance of teeth and is also responsible for dental caries (Facklam et al., 1974). Streptococcus mitis is another bacteria of the genera inhabiting the mouth. LAB REPORT FORM 5: there is a perceptible decrease in the microbial growth following washing of hands and it can be concluded from the lack of microbial growth on plates cultured post handwash. Both the Soap and handwash are equally effective, reducing microbial growth to negligible. The result, however does not agree with class result, class result showing no perceptible decrease in micrbial growth post handwash. LAB REPORT FORM 6: There is a proportional increase in the micrbial growth with serial dilution, maximum growth occuring at the fifth dilution. It is definitely a bactericidal agent, completely inhibiting growth at first and second dilutions. The result is similar to the class result for ethanol, which shows gradual increase in microbia growth with serial dilution. Among the various reagents tested, ethanol (MIC at dilution 2) seems to be most effective chemical agent, inhibiting growth even at second dilution, next being vinegar (MIC: tube turbidity inhibited till dilution 5), bleach (MIC: dilution 1), sodium hydrochloride (MIC: dilution 1); in decreasing order of effectivity. All of these are bactericidal, since they completely inhibit growth at first, or second dilution. Floor cleaner is less effective (MIC: dilution Read More