Post-Traumatic Endophthalmitis Due to Acinetobacter radioresistens: Virulence Potential of Commensal Bacteria

Molecular Characterization of Bacterial Agents Causing External Ocular Infections Isolates of Patients in a Third Level Hospital

Empirical use of antibiotics in the treatment of eye infections leads to bacterial pathogens becoming resistant to antibiotics; consequently, treatment failure and eye health complications occur. The aim of this study was to describe the phenotype and genotype of the resistance and adherence of bacterial agents causing eye infections in patients at Hospital Juárez de México. An observational, prospective, cross-sectional, and descriptive study was carried out in patients with signs and symptoms of ocular infection. Bacterial agents were isolated and identified by classical microbiology and mass spectrometry. Antibiotic resistance and adherence profiles were determined. Finally, resistance (mecA/SCCmec) and virulence (icaA and icaD) genes were detected in the Gram-positive population. The results showed that blepharitis was the most prevalent condition in the study population. A MALDI-TOF analysis revealed that Staphylococcus and Pseudomonas genus were the most prevalent as causal agents of infection. Resistances to β-lactams were detected of 44 to 100%, followed by clindamycins, aminoglycosides, folate inhibitors, and nitrofurans. A multiple correspondence analysis showed a relationship between mecA genotype and β-lactams resistance. The identification of SCCmecIII and SCCmecIV elements suggested community and hospital sources of infection. Finally, the coexistence of icaA+/icaD+/mecA(SCCmecIII) and icaA+/icaD+/mecA(SCCmecIV) genotypes was detected in S. aureus. The identification of resistant and virulent isolates highlights the importance of developing protocols that address the timely diagnosis of ocular infections. Herein, implications for the failure of antimicrobial therapy in the treatment of ocular infections in susceptible patients are analysed and discussed.

Comparative Study of Different Diagnostic Routine Methods for the Identification of Acinetobacter radioresistens

Recent publications indicate that A. radioresistens can cause infections in humans, even though it is rarely reported in routine diagnostics. However, the fact that it is infrequently detected may be explained by the misidentification of the species by conventional methods. It is also likely that A. radioresistens is not considered clinically relevant and therefore not consistently included in diagnostic results. To elucidate the medical significance of this probably clinically underestimated bacterial species, we created a well-documented reference strain collection of 21 strains collected in routine diagnostics. For further analysis of A. radioresistens, it is essential to know which methods can be used to achieve a trustworthy identification. We, therefore, compared three methods widely used in routine diagnostics (MALDI-TOF MS, VITEK 2, and sequencing of housekeeping genes) in terms of secure and reliable identification of A. radioresistens. As reference methods, whole genome-based approaches were applied. VITEK 2 led to misidentification for four strains. However, MALDI-TOF MS and sequencing of housekeeping genes led to reliable and robust identifications.