Co-infection and secondary infection in critically ill Omicron variant COVID-19 patients in a university hospital

<b>Objective:</b> To understand the impact of COVID-19 on the pathogen spectrum in critically ill patients. <b>Method:</b> A retrospective&nbsp;study of COVID-19 ICU patients requiring invasive mechanical ventilation (IMV) or high-flow nasal cannula (HFNC), 2022/1 ~ 2022/8. <b>Results:</b> Consecutive 144 cases were studied. Deducting 12 with ICU stay &lt; 2 days, 132 were examed for secondary infection within 30 days. At ICU admission, there were 132 (92%) cases had both sputum and blood cultures, 100 (69%) had urine culture, 112 (78%) had Pneumococcus&nbsp;&amp;&nbsp;Legionella&nbsp;urine antigen, 81 (56%) had&nbsp;<i>M.&nbsp;pneumoniae</i>&nbsp;IgM, 52 (36%) had sputum&nbsp;<i>M. tuberculosis</i> cultures. Among HFNC group, 3 (5.7%) developed nosocomial pneumonia. And 37 (46.8%) IMV&nbsp;patients got VAP, 14 (37.8%) were newly developed MDRO infections. Other HAI included 5 (3.8%) bloodstream infections, 10 (7.5%) urinary tract infections, 4&nbsp; aspergillosis, 1&nbsp;<i>Pneumocystis</i>&nbsp;pneumonia, 1 CMV viremia. Conclusion The most common pathogens of co-infection pneumonia are<i>&nbsp;K. pneumoniae</i> and <i>P. aeruginosa</i>. Secondary pneumonia is frequent&nbsp;in IMV patients. Carbapenem-resistant Gram-negative bacteria&nbsp;are the substantial threats.