While most Corynebacterium species are commonly considered contaminants when isolated from blood, respiratory and urine specimens, additional factors for each source should be considered:
- For blood cultures
- How was the specimen obtained? Was this a venous draw or a line draw?
- The number of positive cultures - how many cultures were positive, were they collected on multiple days, and were the cultures drawn from a line as well as a venous draw?
- Co-morbidities - does the patient have underlying medical conditions that would suggest an infection from an isolate usually considered "normal flora"?
- Other test results - what are the results of the white blood cell count and differential?
- The clinical condition of the patient - does the body temperature or overall condition of the patient indicate there may be an infection?
- For respiratory specimens
- How was the specimen obtained - is there a chance for normal flora contamination due to collection procedures?
- Gram stain results - were gram-positive rods seen predominantly in the Gram stain surrounded by or ingested by PMNs?
- Culture results - was the organism isolated pure or predominate on the culture plates? Have there been multiple cultures with the same organism isolated?
- Chest X-ray - do the radiographic findings indicate infection?
- Co-morbidities - does the patient have underlying medical conditions that would suggest an infection from an isolate usually considered "normal flora"?
- Other test results - what are the results of the white blood cell count and differential?
- The clinical condition of the patient - does the body temperature, change in respiratory status, or overall condition of the patient indicate there may be an infection?
- For urine specimens
- How was the specimen obtained - is there a chance for normal flora contamination due to improper collection procedure?
- If a Gram stain was ordered, were gram-positive rods seen predominately in the Gram stain surrounded by or ingested by PMNs?
- Culture results - was the organism isolated pure or predominate on the culture plates (>100,000 CFU/mL)? Have there been multiple cultures with the same organism isolated?
- Were there positive blood cultures with the same isolate? This may indicate a urosepsis episode.
- Co-morbidities - does the patient have underlying medical conditions that would suggest an infection from an isolate usually considered "normal flora"?
- Consider the clinical condition of the patient - UTI signs and symptoms such as a fever >38°C, suprapubic or costovertebral tenderness with no other cause, frequency, urgency, or dysuria persisting after catheter removal.
- Do urinalysis results correlate with culture?
A bit of detective work at this stage will help in determining how far to go with the workup of the organism and may save time in deducing a patient's true medical condition.
