Ants (Hymenoptera: Formicidae): mechanical dispersers of pathogenic bacteria in two hospitals in the interior of São Paulo. A problem neglected by public health

Introduction: This study addresses nosocomial infection as a public health problem and highlights the importance of ants as dispersers of bacteria with pathogenic potential in two hospitals in northwest São Paulo. Studies on the transmission of bacteria by ants in hospitals are scarce. Since 1972, the potential of these insects as vectors of pathogens in hospital environments has been observed. This role is influenced by the adaptive behavior of ants in urban environments and by the structure of hospitals, favoring their dissemination. The scientific literature has demonstrated the role of ants in the dissemination of bacteria belonging to the genera Staphylococcus, Serratia, Klebsiella, Acinetobacter, Enterobacter and Enterococcus, however, few studies establish a clear relationship between these bacteria and the prevalence of nosocomial infections by the same infectious agents . Currently, the spread of multidrug-resistant bacteria has become a global public health problem. In this context, the most adopted intervention has been the control of transmission vehicles, through stricter sanitary measures. Objective: The research aims to investigate the presence and diversity of bacterial species carried by ants in the hospital environment, and to verify the real need to control these insects. Methodology: The state of São Paulo is located in a climate transition zone influenced by both extra-tropical and tropical air masses. The collection took place at the Padre Albino and Emílio Carlos hospitals -both philanthropic institutions that work in partnership with the SUS- in the municipality of Catanduva, during the months of March to May 2023. The ants were collected using sterile paper strips and transferred to a Petri dish containing 5% blood-agar culture medium for the insects to walk through the medium and transmit the bacteria to the surface. Observing the growth of mixed colonies on the plate, new samples with isolated colonies were obtained through seeding by exhaustion in the same culture medium and incubated for 24 hours at 37°C and, after being cultivated, submitted to optical microscopy and biochemical identification. Result: Taken together, the results showed that there is a great diversity of bacterial species that can be transmitted by ant feet. Among the bacteria isolated, in an initial analysis, we found cocci, gram positive, catalase positive and catalase negative, suggesting, respectively, species of the genera Staphylococcus and Streptococcus. Others are gram positive, catalase positive and catalase negative bacilli, some sporulating and others not, suggesting species of the Bacillus genera, catalase positive and sporulating. Other bacilli isolated, gram positive, that proved to be catalase negative still require further analysis. These genera are potentially pathogenic for immunosuppressed individuals, especially those hospitalized. Species of these genera are frequently associated with nosocomial infections of the lungs, postoperative wounds, urinary tract, skin and soft tissue, and sepsis. Conclusion: The effective control of these vectors can contribute significantly to reducing the risk of nosocomial infections and increasing the safety of the hospital environment for inpatients.