In order to understand the role of biofilm in the emergence of antibiotic resistance, a total of 104 clinical Acinetobacter baumannii strains were investigated for their biofilm-forming capacities and genes associated with biofilm formation. Selected biofilm-formers were tested for antibiotic susceptibilities when grown in biofilm phase. Reversibility of antibiotic susceptibility in planktonic cells regrown from biofilm were investigated. We found 59.6% of the strains were biofilm-formers, among which, 66.1% were non-multidrug resistant (MDR) strains. Presence of virulence genes bap, csuE, and abaI was significantly associated with biofilm-forming capacities. When strains were grown in biofilm state, the minimum biofilm eradication concentrations were 44, 407, and 364 times higher than the minimum bactericidal concentrations (MBC) for colistin, ciprofloxacin, and imipenem, respectively. Persisters were detected after treating the biofilm at 32–256 times the MBC of planktonic cells. Reversibility test for antibiotic susceptibility showed that biofilm formation induced reversible antibiotic tolerance in the non-MDR strains but a higher level of irreversible resistance in the extensively drug-resistant (XDR) strain. In summary, we showed that the non-MDR strains were strong biofilm-formers. Presence of persisters in biofilm contributed to the reduced antibiotic susceptibilities. Biofilm-grown Acinetobacter baumannii has induced antibiotic tolerance in non-MDR strains and increased resistance levels in XDR strains. To address the regulatory mechanisms of biofilm-specific resistance, thorough investigations at genome and transcription levels are warranted.

Background Self-collected specimens has been advocated to avoid infectious exposure to healthcare workers. Self-induced sputum in those with a productive cough, and saliva in those without a productive cough have been proposed, but sensitivity remains uncertain. Methods We performed a prospective study in two regional hospitals in Hong Kong Results We prospectively examined 563 serial samples collected during the virus shedding periods of 50 patients: 150 deep-throat saliva (DTS), 309 pooled-nasopharyngeal (NP) and throat swabs, and 104 sputum. DTS had the lowest overall RT-PCR positive rate (68.7% vs. 89.4% [sputum] and 80.9% [pooled NP and throat swabs]), and the lowest viral RNA concentration (mean log copy/mL 3.54 vs. 5.03 [sputum] and 4.63 [pooled NP and throat swabs]). Analyses with respect to time from symptom onset and severity also revealed similar results. Virus yield of DTS correlated with that of sputum (Pearson correlation index [95% CI]: 0.76 [0.62 – 0.86]). We estimated the overall false-negative rate of DTS could be 31.3%, and increased 2.7 times among patients without sputum. Conclusion DTS produced the lowest viral RNA concentration and RT-PCR positive rate compared to conventional respiratory specimens in all phases of illness. Self-collect sputum should be the choice for patients with sputum.

Background: Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected millions of individuals since December 2019, resulting in significant morbidity and mortality globally. During the 1918 Influenza Pandemic, it was observed that influenza was associated with bacterial co-infections. However, empirical or prophylactic antibiotic use during viral pandemics should be balanced against the associated adverse drug events. Methods: In this retrospective cohort study, we investigated bacterial co-infections in adults with COVID-19 in Hong Kong. Notably, at the time of writing this report, patients with varying disease severities were isolated in hospitals until confirmatory evidence of virological clearance or immunity was available. The study included adults with laboratory-confirmed COVID-19 admitted to a single hospital cluster between 8 January 2020 and 1 May 2020. We obtained data regarding patient demographics, clinical presentations, blood test results, treatment, and outcomes. Bacteriological profiles and risk factors for co-infections were investigated. Antibiotic prescription practices were also reviewed. Results: Of the 147 patients recruited, clinical disease was suspected in 42% ( n = 62) of patients who underwent testing for other respiratory infections. Notably, 35% ( n = 52) of the patients were prescribed empirical antibiotics, predominantly penicillins or cephalosporins. Of these, 35% ( n = 18) received more than one class of antibiotics and 37% ( n = 19) received empirical antibiotics for over 1 week. Overall, 8.2% ( n = 12) of patients developed bacterial co-infections since the detection of COVID-19 until discharge. Methicillin-susceptible Staphylococcus aureus was the most common causative pathogen identified. Although 8.2% ( n = 12) of patients developed hypoxia and required oxygen therapy, no mortality was observed. Multivariate analysis showed that pneumonic changes on chest radiography at the time of admission predicted bacterial co-infections. Conclusion: These findings emphasise the importance of judicious administration of antibiotics throughout the disease course of COVID-19 and highlight the role of antimicrobial stewardship during a pandemic.

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