Implementing the Updated Guidelines in Routine Clinical Microbiology Reporting [Letter]

Dear editor

Bacterial isolation and elaboration of their antimicrobial susceptibility pattern in various types of external eye infections is of paramount importance so as to initiate the early and targeted antimicrobial therapy. This study by Woreta et al has emphasized the same by characterizing various bacterial isolates from such infections and performing their antimicrobial susceptibility pattern in patients from Menelik II Referral Hospital in Addis Ababa, Ethiopia.¹

The study has mentioned about the different types of eye samples collected, their laboratory processing methods including the quality control checks in the laboratory and bacterial isolates identified from them and their antimicrobial susceptibility testing results as per CLSI guidelines.^2–4

We would like to add a few comments related to the antimicrobial agents tested and the guidelines used for reporting the results of these antimicrobial susceptibility tests.

In the present study, the authors have mentioned about the CLSI guidelines 2017 for performing and interpreting the results of susceptibility testing of Vancomycin for Staphylococcus aureus by disk diffusion method whereas the current CLSI guidelines do not recommend the same.^5,6 The authors have further reported high susceptibility to Vancomycin (92.9%) among the gram positive isolates tested. However as per current CLSI guidelines, the reported susceptibility pattern of Vancomycin in gram positive isolates in the present study may lead to incorrect interpretation as the susceptibility reporting of Vancomycin in Staphylococcus aureus by disk diffusion method has been discontinued. Further to that, there is an evidence of Vancomycin susceptible Staphylococcus aureus isolates becoming Vancomycin intermediate susceptible during the course of prolonged therapy which may further result in treatment nonresponsiveness.^5,6

Additionally, the routine testing and reporting of Tobramycin susceptibility results for the Staphylococcus species including CONS is not mentioned in current CLSI guidelines which is mentioned in the present study. However, the aminoglycosides have shown the clinical utility for treating infections caused by Staphylococci including Methicillin Resistant Staphylococcus aureus (MRSA) and Vancomycin resistant Staphylococcal isolates (VRSA).^5–7

The CLSI guidelines have not given any comment on the reporting of Vancomycin resistance in Streptococcus spp. viridans group though the same has been highlighted in this study in table 3.^5,6

Lastly, computing the 100% susceptibility from a single P. stuartii isolate to Gentamicin in Table 4 is not in lines with the current CLSI as well as EUCAST guidelines which clearly mention that P. stuartii should be considered resistant to Gentamicin, Netilmicin and Tobramycin and though appear as susceptible in vitro; they should be reported as resistant.^5,6,8

Nonetheless, we appreciate the authors for their sincere efforts for conducting the study on bacterial pathogens from various external eye infections along with inclusion of all the essential laboratory quality control parameters and studying the association of different variables involved.