Clinical Cases


Case 1: Acute Osteomyelitis

 

This case concerns a ten year old boy presenting with pain and stiffness in his left knee. Previously well, he did suffer from 'septic spots' that usually disappeared after prescription of amoxycillin. On Friday 22 March he became ill with fever (39oC), a raised pulse (120 beats per minute) and muscle aches and pains. His General Practitioner diagnosed influenza, and prescribed paracetamol for the boy.

The patient's condition deteriorated during the next 24 hours and by 6 p.m. on Saturday 23 March, he had a temperature of 40.2oC and a pulse of 140 beats per minute. In addition to general aches and pains, he complained of pain in his left leg, just below the knee joint. Flexing the left knee caused severe pain.

His mother was unhappy with the diagnosis of influenza and rang the doctor's deputising service, who reassured her that the infection was self-limiting, and that it might be wise to persist with the paracetamol.

During the next 24 hours he showed no improvement, and the symptoms were aggravated by nausea and vomiting. The boy became flushed and delirious. His temperature was 41.0oC by Sunday afternoon. The child was taken to the casualty department of St. James' University Hospital. He was seen at 7 p.m. and was diagnosed as suffering from meningitis because of his toxaemia, headache, and reduced level of consciousness. He was given intravenous cefotaxime. A lumbar puncture was performed.

Two hours later, the CSF was reported as normal, but his blood sample showed 3.5x 109 leukocytes per litre, of which 92% were polymorphs. The diagnosis was changed to pyogenic sepsis of unknown aetiology. An emergency brain scan was performed to exclude a cerebral abscess. At midnight this was reported as normal.

The Consultant noted that despite a general restlessness, the patient did not move his left leg spontaneously. Careful examination of the upper part of the left tibia revealed an area where any local pressure caused extreme pain. The limb was swollen and red, and the mother said it had been like this for the past three days.

A diagnosis of acute osteomyelitis was now made, and the patient was referred to the orthopaedic department. Two boreholes were drilled in the upper part of the left tibia where inflammation was most marked. Each aspirate yielded 5 ml of bloodstained pus. The left knee joint was aspirated and its fluid was cloudy. The following results were reported by the laboratory:

 

Both bone aspirates yielded a pure growth of Staphylococcus aureus resistant to penicillin, ampicillin and amoxycillin, but sensitive to erythromycin, fusidic acid, flucloxacillin and gentamicin. The knee aspirate contained 300 polymorphs/cu.mm but was sterile.

 

The osteomyelitis had not invaded the knee joint - the effusion was sympathetic. The pus aspirate confirmed the diagnosis of osteomyelitis. The patient was treated with flucloxacillin and fusidic acid, begun after surgery was complete.

Case 1 Comments:

 

The patient was probably a nasal carrier of Staphylococcus aureus, the source of the bacterium causing osteomyelitis.

The probable delay in diagnosis and treatment was because:

a) The diagnosis was not considered because the condition is rare.
b) Cefotaxime was considered to be the correct therapy.

The use of two antibiotics initially in undiagnosed osteomyelitis is reasonable because the probable causative bacterium, Staphylococcus aureus, has an unpredictable sensitivity and because flucloxacillin and fusidic acid are synergistic against this bacterium.

 

In suspected cases of osteomyelitis, why are holes drilled into the bone?

 

How long does it take for the laboratory to be fairly confident that Staphylococcus aureus is present?

 

How long does it take for the laboratory to be certain that Staphylococcus aureus is present?

 

If Staphylococcus aureus resists penicillin, why is it also resistant to ampicillin and amoxycillin, but sensitive to flucloxacillin?

 

How would you have managed this case had the patient been allergic to penicillins?

 

 


Case 2: Lobar Pneumonia

 

A 23 year old male, a known asthmatic, developed a 'cold' a week before a referral letter was written in March. He complained of malaise, generalised dull headache, a mild sore throat and non-productive cough. After four days he suffered a severe shaking chill lasting 15 minutes, his cough worsened and the patient produced a rusty coloured sputum. The patient was pyrexial when examined and was admitted to hospital. His notes are given:

 

  Presenting complaint
Cold - one week
Cough - one week
Headache - one week
Shaking chill three days ago.
 

History of presenting complaint
Known asthmatic, cold week ago, tired, headache, sore throat, general aches, chestiness. Just before tea-break three days ago suffered a chill. Cough worsened. Started coughing up sputum, wheezing got worse, pain on breathing in.

 

Past history
Known asthmatic, tonsillectomy aged 7, LGI.

 

Current Medication
Sodium chromoglycate 20 mg qds (for asthma)
No recent antibiotics

 

Family History
Mother and Father - well. One sister - well.

 

Social History
Non-smoker, Social drinker

 

 

Temperature: 40oC         Blood Pressure: 112/70

 

Physical Examination
23 year old male, respiratory distress and an obvious herpetic lesion on his top lip. No signs of anaemia.

 

Respiratory System
Rapid, shallow breathing, rate 36/min.
Reduced expansion on right side.
Dullness to percussion over right middle lobe.
Fine crepitations over right middle lobe.

  Rest of physical examination
No abnormalities detected.
 

Laboratory reports
Blood chemistry: normal
Haematology: normal, except total wbc 15,000/cu mm

A text version of the table below is provided for browsers that do not display tables properly.

Differential leukocyte count:
Cell typeCount
neutrophils 11,000 - shift to left
eosinophils 1,000
basophils 30
lymphocytes 2,500
monocytes 470
  You are provided with a Gram film and culture plate from the specimen of sputum, and cultures from three sets of blood cultures subcultured after overnight incubation at 37oC. An anterior chest X-ray is also provided.
 

What bacteria are present in the Gram film?

 

What bacterium has grown from the blood culture?

 

Is the same isolate present in the sputum?

 

What tests would you use to confirm the identity of the blood culture isolate?

 

What treatment is generally used in such cases?

 

 


Case 3: Food Poisoning in a Psycho-Geriatric Unit

 

This incident occurred in a psychogeriatric hospital, where many inpatients experienced a sudden episode of diarrhoea and vomiting. The first patients became ill on the morning of 21 August.

 

What information and samples will you require to investigate and control this problem?

 

 

 

The affected patients all ate food on the menus below:

 

19 August

 

Lunch

Fried Cod Chips and Peas
Apple Crumble and Custard

Supper

Shepherds Pie Brussels Sprouts Boiled Potatoes
Lemon Meringue Pie

 

20 August

 

Lunch

Ham Salad
Rhubarb Crumble

Supper

Chicken Kiev
Fresh Fruit Salad with Condensed Milk

 

What foods may be implicated and what food poisoning organisms are associated with that food?

 

 

 

Primary culture of faeces from affected patients on MacConkey agar yielded motile, non-swarming Gram-negative bacilli that did not ferment lactose.

 

What organism is likely to be the causative agent?

 

What further laboratory tests might be used to identify the isolate?

 

 

 

You have now been interviewed on local television because patients have died, and there is a call for a Government enquiry.

 

What steps have you taken to control this episode of food poisoning?

 

 


Case 4: Osteomyelitis Following Major Trauma

 

Mr AS sustained a compound fracture of the tibia in a motor car accident, and was admitted to the LGI. A swab was taken before cleaning the wound prior to suturing. Mr S was placed on traction to allow the fracture to heal. A culture is provided.

 

What has been isolated?

 

Which of the isolates are likely to lead to a wound infection?

 

Is it helpful to use prophylactic antibiotics in casualty?

 

 

 

Four days after his accident, Mr. S became pyrexial (39.6oC) and he had a raised white blood cell count. Whilst in hospital his fracture was immobilised. A sample of pus was aspirated from his wound. The isolate from the pus is provided.

 

What is the bacterium likely to be?

 

How would you confirm this?

 

List the tests you would perform and the results you would expect to obtain.

 

 

 

After 70 days the original wound had healed, but the bone did not. Mr. S required a bone graft and fixation with pins attached to an external frame. Post-operatively there was a serosanguinous discharge from the wound. A swab was taken and the culture is provided for you.

 

What is the isolate?

 

How should this be treated?

 

 

 

Two days later Mr. Simmons was pyrexial (37.5oC). He was started on gentamicin (120mg tds).

 

Is this a suitable treatment?

 

What precautions are necessary when gentamicin is used?

 

 

 

By day 90 Mr. S is progressing well, his wound has now healed, but he has a purulent discharge from the base of one of his pins. A staphylococcus was isolated.

 

Is this likely to be significant?

 

Does it have any importance for any other patients and, if so, how may its spread be prevented?

 

 


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Page edited April 2006


Microbiology Teaching Page


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