Question

CASE STUDY A 32 year-old mother presents at her GP clinic and is concerned about a painful right breast. Her baby has been breast feeding since birth and is now 3 months old. She describes episodes of night chills and fever during the last few days. She is run down, tired and exhausted. She is finding it difficult to care for her baby. Upon examination her doctor observes swelling, warmth and redness of the breast tissue with cracked nipples. Her temperature is 38.8°C. The doctor suspects mastitis, inflammation of the breast tissue with clogged milk ducts, which may be due to an infection. The patient is advised to continue breast feeding and take over-the-counter pain relievers (ibuprofen). However, the doctor would like to prescribe a course of antibiotics to clear the mastitis and prevent a recurrence.

The patient asks about the type of treatment and the doctor replies: “Which type of drugs are prescribed and for how long depend on your health condition and the type of bacteria found in your milk. We will need to send a sample to the lab for testing.”

You, as the diagnostic microbiologist, have been provided with a sample of this patient’s milk from the affected breast ducts for investigation. You need to correctly diagnose the infectious agent and determine antibiotic sensitivity to recommend choice antibiotics for effective treatment.

1) TESTS PERFORMED & RESULTS: (100-word limit)

Microbiological diagnosis:

2)

ANTIBIOTIC SENSITIVITY TEST	Zone of inhibition (mm)	R/I/S

3) DISCUSSION: (100-word limit)

Provide a brief description of diagnosis and treatment options for control of the bacterial infection

Answer 1

Sample : Milk collected from affected breast ducts.

1. Methods and tests for microbiological diagnosis

i. Sample preparation

Sample was prepared by serial dilution technique. The sample dilutions prepared were upto 10-5 using sterile distilled water.

ii. Plating

The 100ul of diluted samples were plated on Mueller Hinton agar plates. Incubate at 37C for 24 hrs.

iii. Colony observation and characterization  

The colonies obtained on the plates were observed, counted (CFU) and noted. The colonies were large, golden-yellow, circular, smooth, butyrous, raised and opaque.

iv. Gram-testing

The bacteria from plates were subjected to Gram staining. This revealed Gram positive cocci in "grape-like" arrangements under light microsope.

**The above results indicates the presence of Staphylococcus sp., a very common bacteria constituting skin microflora. But these cannot be confirmatory.

v. To confirm our suspicion we plate the bacteria from our previously obtained spread plates and streak it onto Columbia agar with 5% sheep blood. We incubate the plate at 37oC for 24 hours. The colonies obtained after incubation were golden-yellow with a surrounding clear zone. This characteristic is showed by Staphylococcus aureus. The clear zone around colonies is the occurance of hemolysis.

vi. Few biochemical tests were also carried on for further confirmation:

Biochemical Tests
Result
Catalase	+
Coagulase	+
Oxidase	-
Indole	-
Methyl Red	+
Voges Proskauer	+
Citrate	-
Nitrate Reduction	+
Urease	+
H2S	-
Starch Hydrolysis	-
Gelatin	-
Mannitol salt fermentation	+

The above biochemical characteristics prove that the tested organism is indeed Staphylococcus aureus.

2.

Antibiotic	Zone of Inhibition (mm)	S/I/R
Penicilin	27	Sensitive
Neomycin	18	Sensitive
Gentamicin	16	Sensitive
Streptomycin	16	Sensitive
Vancomycin	18	Sensitive
Ampicilin	18	Sensitive
Erythromycin	24	Sensitive

3. Clinical Diagnosis

Symptom based: The characteristic symptoms of S. aureus infecting breast are as follows -

a. abrupt onset of high fever

b. breast enlargement on one side

c. breast lump and pain

d. itching, swelling, tenderness, skin redness, warmth in breast tissue and nipple discharge

Laboratory-based diagnosis:

a. Bacterial culture test from clinical sample

b. Biochemical tests for confirmation

Treatment

The treatment to control a breast infection of S. aureus  would require an antibiotic therapy of penicilin (if found sensitive) on dosages decided by the doctor which would depend on the patient's health and other qualitative parameters found relevant by the doctor.