Clinical Cases

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? To relieve the pain, to debride the wound, and to obtain a sample for laboratory analysis. How long does it take for the laboratory to be fairly confident that Staphylococcus aureus is present? Given the aetiology of the condition, about ten minutes - a Gram stain will show Grampositive cocci in the pus. How long does it take for the laboratory to be certain that Staphylococcus aureus is present? Up to 48 hours, if the slide test for clumping factor is negative, and a DNase test and tube coagulase must be carried out. If Staphylococcus aureus resists penicillin, why is it also resistant to ampicillin and amoxycillin, but sensitive to flucloxacillin? Flucloxacillin is an anti-staphylococcal penicillin that can resist the action of staphylococcal penicillinase. The other penicillins listed are sensitive to staphylococcal penicillinase. How would you have managed this case had the patient been allergic to penicillins? Because of the patient's allergy to penicillins, an alternative antimicrobial regime must be sought. Due to the poor penetration of many antibiotics into bone, the choice of therapy in such cases is not easy. Clindamycin as a single agent is a reasonable choice, reserving vancomycin as a first-line agent for the treatment of resistant staphylococcal infections.

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 Differential leukocyte count: 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? A mixed flora, both cocci and bacilli, that are either Gram-positive or Gram-negative. Notably, however, the film will cntain lanceolate Gram-positive diplococci. What bacterium has grown from the blood culture? Streptococcus pneumoniae Is the same isolate present in the sputum? Yes, but amongst many other bacteria, derived from the patient's commensal flora. What tests would you use to confirm the identity of the blood culture isolate? Catalase (negative), Optochin sensitivity (sensitive), Bile solubility (soluble). What treatment is generally used in such cases? Penicillin, unless the patient is allergic, or the isolate is penicillin tolerant. Erythromycin is an alternative.

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? Menus, and information on who had eaten what. 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? Given that this is NHS catering, some foods that may be prepared fresh in some establishments will be prepared in bulk, and form previously pasteurised constituents. This will actually reduce the risk posed by, for example, lemon meringue pie. Had this been freshly prepared, it is a potential source of Salmonella enterica var. Enteritidis, but given the catering limitations this is unlikely in this case. There are a number of sources of food poisoning on the menu from the previous two days. These include: Shepherd's pie - Clostridium perfringens. Lemon meringue pie - see above Ham salad - Staphylococcus aureus in the ham, but incubation is too long. Chicken Kiev - a salmonella.

Given the symptoms, and the timing of the incident, the Chicken Kiev is the most likely cause of the incident.

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? A salmonella What further laboratory tests might be used to identify the isolate? Biochemical reactions and its antigenic structure, as determined by serological agglutinations. Since a large number of isolates ill be generated, strain sub-typing will greatly help in investigating the incident. Plasmid profiles can be rapidly determined. If the serovar is common, then the reference laboratory will also perform bacteriophage typing. 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? This will fall into two categories; patient management and environmental measures. Screen for carriage, and cohort infected patients, whether or not they are symptomatic, and close the hospital to further admissions. This will prevent secondary spread, and will also alleviate the burden of the over-worked staff. On the environmental front, make sure that the kitchen practices are adequate, and that the physical state of the food preparation and consumption areas are satisfactory. Full environmental sampling is necessary to identify the source of the incident.

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? A coliform and a Staphylococcus aureus Which of the isolates are likely to lead to a wound infection? Staphylococcus aureus Is it helpful to use prophylactic antibiotics in casualty? Given the severity of the injury in this case, yes, if only to prevent anaerobic infection of the wound. 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? Staphylococcus aureus How would you confirm this? List the tests you would perform and the results you would expect to obtain. Gram reaction (Gram-positive cocci) Catalase (positive) Coagulase (positive) [DNase (positive)]

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? A coliform. How should this be treated? Pins should be removed, if possible, and the wound treated with an antiseptic. Two days later Mr. Simmons was pyrexial (37.5oC). He was started on gentamicin (120mg tds).

Is this a suitable treatment? No. Gentamicin has poor penetration into bone. What precautions are necessary when gentamicin is used? Serum levels must be monitored to ensure that toxic accumulation does not occur, and that therapeutic levels are maintained. 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? Yes Does it have any importance for any other patients and, if so, how may its spread be prevented? Yes. The most important control is thorough hand washing by staff on the unit.