From the Guidelines
If preliminary microbiology results show gram-positive coccibacilli and gram-positive rods, empiric antibiotic coverage should include vancomycin 15-20 mg/kg IV every 8-12 hours (adjusted based on renal function and targeting trough levels of 15-20 μg/mL for serious infections) to provide coverage for common gram-positive organisms including Staphylococcus species, Streptococcus species, Corynebacterium, Listeria, and Bacillus species. The choice of vancomycin is based on its effectiveness against a wide range of gram-positive organisms, as outlined in the 2002 guidelines for the use of antimicrobial agents in neutropenic patients with cancer 1.
Key Considerations
- The presence of both gram-positive coccibacilli and gram-positive rods suggests either a polymicrobial infection or potential contamination of the sample.
- Clinical correlation is essential, considering the source of the culture, patient symptoms, and risk factors when interpreting these preliminary results.
- Gram-positive coccibacilli may represent organisms like Corynebacterium or Listeria, while gram-positive rods could indicate Bacillus species, Clostridium, or other bacilli.
Additional Coverage
For broader coverage, especially if the infection is severe or in an immunocompromised host, consider adding piperacillin-tazobactam 4.5g IV every 6-8 hours or meropenem 1g IV every 8 hours.
Therapy Adjustment
Once final culture and sensitivity results are available (typically in 48-72 hours), therapy should be narrowed to the most appropriate agent, taking into account the specific organisms identified and their antibiotic resistance patterns, as recommended in the guidelines 1.
Catheter-Related Infections
In cases where catheter-related infections are suspected, such as with Staphylococcus aureus or coagulase-negative staphylococci, removal of the catheter may be necessary for cure, especially if there is evidence of a subcutaneous tunnel or periport infection, septic emboli, hypotension associated with catheter use, or a nonpatent catheter 1.
From the Research
Interpretation of Preliminary Microbiology Results
Preliminary microbiology results showing Gram-positive coccobacilli and Gram-positive rods can be indicative of several types of bacterial infections.
- The presence of Gram-positive coccobacilli can suggest the presence of bacteria such as Weissella confusa, which has been reported to cause bacteremia in patients with complex medical histories or those receiving multiple antibiotics 2.
- Gram-positive rods, on the other hand, can be indicative of bacteria such as Lactobacillus species, which are generally associated with polymicrobial infections and can be considered possible pathogens when isolated from the blood 2.
Possible Infections and Treatment
The interpretation of these results should be considered in the context of the patient's medical history and clinical presentation.
- Infections caused by Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE), can be challenging to treat due to their resistance to commonly used antibiotics 3, 4, 5.
- Newer antibiotics, such as linezolid, have been developed to treat resistant Gram-positive bacterial infections and have been shown to be effective in the treatment of several serious infections 6.
Considerations for Treatment
When considering treatment options, it is essential to take into account the potential for antibiotic resistance and the need for effective treatment strategies.
- The use of antibiotics with activity against Gram-positive multiresistant cocci, such as vancomycin and linezolid, should be guided by susceptibility testing and clinical experience 3, 6.
- The development of new antimicrobial agents and the reinvigoration of old antibiotics that still retain appreciable activity against Gram-positives are crucial in the treatment of Gram-positive infections 5.