Travel-associated SARS-CoV-2 transmission documented with whole genome sequencing following a long-haul international flight.

BACKGROUND: Multiple instances of flight-associated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission during long-haul flights have been reported during the COVID-19 pandemic. However, comprehensive investigations of passenger risk behaviours, before, during and after the flight, are scarce. METHODS: To investigate suspected SARS-CoV-2 transmission during a flight from United Arab Emirates to Australia in July 2020, systematic, repeated polymerase chain reaction (PCR) testing of passengers in hotel quarantine was linked to whole genome sequencing. Epidemiological analyses of in-depth interviews covering behaviours during the flight and activities pre- and post-boarding were used to identify risk factors for infection. RESULTS: Seventeen of the 95 passengers from four different travel origins had PCR-confirmed infection yielding indistinguishable genomic sequences. Two of the 17 passengers were symptomatic within 2 days of the flight, and classified as co-primary cases. Seven secondary cases were seated within two rows of the co-primary cases, but five economy passengers seated further away and three business class passengers were also infected (attack rate = 16% [15/93]). In multivariable analysis, being seated within two rows of a primary case [odds ratio (OR) 7.16; 95% confidence interval (CI) 1.66-30.85] and spending more than an hour in the arrival airport (OR 4.96; 95% CI 1.04-23.60) were independent predictors of secondary infection, suggesting travel-associated SARS-CoV-2 transmission likely occurred both during and after the flight. Self-reported increased hand hygiene, frequent aisle walking and using the bathroom on the plane did not independently affect the risk of SARS-CoV-2 acquisition. CONCLUSIONS: This investigation identified substantial in-flight transmission among passengers seated both within and beyond two rows of the primary cases. Infection of passengers in separate cabin classes also suggests transmission occurred outside the cabin environment, likely at the arrival airport. Recognizing that transmission may occur pre- and post-boarding may inform contact tracing advice and improve efforts to prevent future travel-associated outbreaks.

Antimicrobial susceptibility of Moraxella catarrhalis isolated from children in Kalgoorlie-Boulder, Western Australia.

AIM: To investigate antimicrobial susceptibility of Moraxella catarrhalis isolated from a cohort of children being followed in a study of the natural history of otitis media in a semi-arid region of Western Australia. METHODS: In the Kalgoorlie Otitis Media Research Project nasopharyngeal aspirates were collected from children up to seven times between the age of 1 week and 2 years. A total of 261 M. catarrhalis strains from 50 Aboriginal and 50 non-Aboriginal children were tested against 14 antibiotics using the Clinical and Laboratory Standards Institute (CLSI) agar dilution method. RESULTS: All strains were susceptible to amoxicillin/clavulanate, cefuroxime, azithromycin, ciprofloxacin, moxifloxacin, levofloxacin, erythromycin and minocycline. While no criteria exist for assessment of susceptibility to roxithromycin, minimum inhibitory concentrations (MICs) were low. Approximately 46% of strains from Aboriginal children and 27% from non-Aboriginal children appeared susceptible to ampicillin. A small number of strains was intermediately resistant to cefaclor (9/261, 3.4%), while the bulk of strains was intermediately resistant to co-trimoxazole. A low prevalence of tetracycline resistance (3/261, 1.1%) was noted. beta-lactamase production was observed in 97.7% of strains. CONCLUSIONS: While M. catarrhalis strains from children of the Kalgoorlie region were susceptible to many of the antibiotics used to treat respiratory tract infections, a large proportion of strains were resistant to ampicillin and/or co-trimoxazole. Current therapeutic guidelines, which recommend amoxicillin for treatment of otitis media, may need to be revised.

Improved pulsed field gel electrophoresis method for Moraxella catarrhalis.

An improved PFGE method for the molecular typing of Moraxella catarrhalis is described. A modified PulseNet method using higher concentrations of EDTA and proteinase K, together with increased reagent volumes and incubation temperatures resulted in improved results and a more rapid turnaround time compared to PFGE methods currently used.