Microbiology Flashcards
What is the risk of wound infection occurring in a 43 year old woman who is undergoing a laparoscopic choelcystectomy for uncomplicated biliary colic?
2% 5% 15% 20% 30%
5%
The incidence is higher because it is a clean contaminated wound. If there is a bile spill the risks increase and intravenous antibiotics should be given perioperatively.
A 22 year old man presents with a painless penile ulcer and marked inguinal lymphadenopathy. Some of the exudate from the lesion is sent for microscopy. What organism is most likely to be visualized?
Treponema pallidum Nocardia asteroides Mycobacterium tuberculosis Mycobacterium leprae Neisseria gonorrhoea
Treponema pallidum
A hard painless ulcer affecting the genital area of a young male is likely to be the primary lesion of syphilis and that is caused by treponema pallidum. It would be unusual for actinomycosis to affect this area.
A 68 year old man with poorly controlled diabetes presents with severe otalgia and headaches. On examination, there is granulation tissue within the external auditory meatus. What is the most likely underlying infective agent?
Pseudomonas aeruginosa Streptococcus pyogenes Staphylococcus aureus Actinomyces Bacteroides fragilis
Pseudomonas aeruginosa
Severe pain, headaches and granulation tissue within the external auditory meatus are key features of malignant otitis externa. Diabetes mellitus is one of the commonest risk factors.
A 23 year old woman is admitted with sepsis and right loin pain. She has a history of a UTI that was treated by the GP with a course of trimethoprim that was commenced 24 hours previously. Which of the organisms listed below is the most likely cause?
Bacteroides fragilis E-Coli Clostridium difficile Candida albicans Mycobacterium tuberculosis
E-Coli
Ascending infection of the genitourinary tract is most commonly caused by E-Coli. Other organisms may be accountable, however, these are less common
A 30 year old aid worker becomes unwell whilst helping at the scene of a recent earthquake. He develops vomiting and soon afterwards a diarrhoea that is loose and extremely watery. What is the most likely infective organism?
Campylobacter jejuni Vibrio cholera Enterohaemorragic E Coli Clostridium perfringens Clostridium boltulinum
Vibrio cholera
The passage of very loose and watery stools distinguishes cholera. Most gastroenteric infections do not produce such watery motions.
A 45 year old man is recovering in hospital following a total hip replacement. He develops a profuse and watery diarrhoea. Several other patients have been suffering from similar symptoms. Infection with which of the following is the most likely underlying cause?
Clostridium perfringens Clostridium botulinim Clostridium difficile Clostridium welchi Clostridium tetani
Clostridium difficile
Clostridium difficile can spread rapidly on surgical wards. The use of broad spectrum prophylactic antibiotics during arthroplasty surgery can increase the risk.
A 28 year old chef presents to the medical team with profuse bloody diarrhoea. On further questioning he describes tenesmus. They arrange a sigmoidoscopy which reveals necrosis and ulceration of the descending colon mucosa. What is the most likely cause?
Ischaemic colitis Infection with Yersinia pestis Infection with entero invasive E Coli Infection with campylobacter Infection with vibrio cholera
Infection with entero invasive E Coli
Necrosis and ulcers of the large bowel are a feature of enteroinvasive E.coli. It presents with a dysentery type illness similar to shigellosis.
What is the likely risk of surgical wound infection in a 23 year old male undergoing an elective inguinal hernia repair?
Between 5 and 10% Less than 5% Between 10 and 15% More than 25% Between 15 and 20%
Less than 5%
This is a clean procedure and carries the lowest risk of SSI. That is why it is safe to use meshes in these settings.
A 34 year old homosexual is admitted with diarrhoea of 3 months duration. He is found to be HIV positive with a CD4 count <50. Which of the organisms listed below is most likely to be responsible?
Cryptosporidium Adenovirus Norovirus Vibrio cholera Clostridium difficle
Cryptosporidium
Although a self limiting diarrhoea is the norm, this is not the case in immunocompromised individuals who can develop severe illness. Other organisms may include Salmonella, Shigella, and Campylobacter.
A 62 year old lady is unwell following a difficult acute cholecystectomy for acute cholecystitis. Her gallbladder spilled stones intraoperatively and she has been on ciprofloxacin intravenously for this for the past 4 days. She now has colicky abdominal pain and profuse, foul smelling diarrhoea. Which of the organisms below is likely to account for this illness?
E-Coli Clostridium difficile Clostridium perfringens Clostridium tetani Campylobacter
Clostridium difficile
C. difficile may complicate administration of broad spectrum antibiotics.
A 68 year old man with diabetes presents with an area of necrosis of the perineum at the base of the scrotum, there is some surrounding erythema. He is systemically unwell and hypotensive. Which of the following organisms is likely to be accountable?
Clostridium tetani Staphylococcus epidermidis and streptococcus viridans Bacteroides and staphylococcus saprophyticus Streptococcus viridans and bacteroides E-coli and bacteroides
E-coli and bacteroides
This is likely to be Fournier’s Gangrene. A number of agents are implicated. E-coli and bacteroides are the most commonly isolated organisms. The key point is that both aerobic and anaerobic organisms must be present.
A 53 year old man presents with an ulcerated mass at the anal verge. A biopsy is taken and the histology demonstrates as squamous cell carcinoma. Infection with which of the viruses below is most likely to have contributed to the development of the condition?
Human papillomavirus 7 Human immunodeficiency virus 1 Human immunodeficiency virus 2 Human papillomavirus 16 Human T-lymphotropic virus 1
Human papillomavirus 16
Infection with human papilloma virus 16 is a risk factor for the development of intra epithelial dysplasia of the anal skin with subsequent increased risk of invasive malignancy.
A 58 year old man undergoes a difficult colonoscopy for assessment of a caecal cancer. 48 hours after the procedure he is admitted with septicaemia. His abdomen is soft and non tender. Blood cultures grow gram positive cocci. What is the most likely underlying organism?
Staphylococcus epidermidis Streptococcus pyogenes Streptococcus bovis Clostridium difficle Bacteroides fragilis
Streptococcus bovis
Streptococcus bovis septicaemia is associated with carcinoma of the colon. It also can also cause endocarditis.
A 29 year old female undergoes a sub total thyroidectomy. Five days post operatively the wound becomes erythematous and discharges pus. What is the most likely causative organism?
Streptococcus pyogenes Haemophilus influenzae Pseudomonas aeruginosa Staphylococcus aureus Proteus mirabilis
Staphylococcus aureus
In this setting Staphylococcus aureus Infection is the most likely cause. In the UK between 2010 and 2011 the commonest cause of wound infection was enterobacter infections (usually following cardiac or colonic surgery). 23% of infections were due to Staph aureus, which fits the scenario above. Infection with the other organisms including strep pyogenes was much rarer.
Which of the following cancers is not associated with the human papillomavirus?
Anal cancer Oropharyngeal cancer Tracheal cancer Vulval cancer Penile cancer
Tracheal cancer
HPV is associated with:
- Cervical cancer (HPV 16/18 most common)
- Anal cancer
- Penile cancer
- Vulval cancer
- Oropharyngeal cancer
A 21 year old man is admitted with crampy abdominal pain and diarrhoea. He attended a large wedding earlier in the day. Several other guests are also affected with the same illness. Which of the organisms is likely to be accountable?
Staphylococcus aureus E-Coli Salmonella Clostridium perfringens Campylobacter
Clostridium perfringens
C. Perfringens is a common cause of food borne illness and its ability to form spores may make it relatively resistant to cooking. The timing of onset would favor C. Perfringens which typically evolves over several hours, rather than staphylococcus aureus poisoning which may occur sooner.
Which of the following is not associated with Epstein-Barr virus?
Burkitt's lymphoma Post-transplantation lymphoma Hodgkin's lymphoma Nasopharyngeal carcinoma Mycosis fungoides
Mycosis fungoides
Which organism is most likely to cause osteomyelitis in children with sickle cell disease?
Group A Streptococcus species Staphylococcus aureus Enterobacter Salmonella species Group B Streptococcus species
Salmonella species
Worldwide the Salmonella species remains the most common infecting organism in children with osteomyelitis. Reference: Etiology of Osteomyelitis Complicating Sickle Cell Disease (Burnett, et al. Pediatrics 1998; 101:2 296-297)
A 28 year old lady is breast feeding her first child. She presents with discomfort of the right breast. Clinical examination demonstrates erythema and an area that is fluctuant. Aspiration and culture of the fluid is most likely to demonstrate infection with which of the following organisms?
Lactobacillus caseii Staphylococcus aureus Streptococcus pyogenes Staphylococcus epidermidis Actinomycosis
Streptococcus pyogenes
Staphylococcus aureus is the commonest cause. The infants mouth is usually the source as it damages the nipple areolar complex allowing entry of bacteria.
A 22 year old man has undergone an inguinal hernia repair. Seven days later he presents with an erythematous and tender wound that is discharging a purulent material. What is the most likely cause?
Infection with Staphylococcus aureus Discharging haematoma Infection with Pseudomonas Infection with Streptococcus pyogenes Infection with Bacteroides
Infection with Staphylococcus aureus
In this setting Staphylococcus aureus Infection is the most likely cause. In the UK between 2010 and 2011 the commonest cause of wound infection was enterobacter infections (usually following cardiac or colonic surgery). 23% of infections were due to Staph aureus, which fits the scenario above. Infection with the other organisms including strep pyogenes was much rarer.
An enthusiastic watercress farmer is admitted with a protracted history of severe abdominal pain, fevers and progressive jaundice. Imaging with ultrasound shows mildly dilated bile ducts with hyperechoic areas within them. What is the most likely cause?
Fasicola hepatica Clonrochis sinesis Entamoeba histiolytica Viral hepatitis Leptospirosis
Fasicola hepatica
The watercress history is important here as fasicola hepatica is most classically transported to humans through eating watercress. The USS finding of luminal parasites is classical and its this that contributes to jaundice.
