Nocardia species distribution and antimicrobial susceptibility within Australia.

BACKGROUND: Nocardia is a ubiquitous saprophyte capable of causing human disease. Disease is primarily respiratory or cutaneous, usually acquired via inhalation or inoculation. Under the influence of environmental and host factors, Nocardia incidence and species distribution demonstrate geographical variation. AIMS: To examine for differences in Nocardia incidence within Western Australia (WA) and analyse species distribution in the context of prior published studies. To analyse antibiogram data from a nationwide passive antimicrobial resistance surveillance program. METHODS: Retrospective extraction of laboratory data for Western Australian Nocardia isolates over a 21-year period. Analysis of Nocardia antimicrobial susceptibility testing data submitted to the Australian Passive Antimicrobial Resistance Surveillance (APAS) program between 2005 and 2022. RESULTS: Nine hundred sixty WA isolates were identified, giving an annual incidence of 3.03 per 100 000 population with apparent latitudinal variation. The four most common species identified within WA and amongst APAS isolates were N. nova, N. cyriacigeorgica, N. brasiliensis and N. farcinica. APAS data demonstrated that all species exhibited high rates of susceptibility to linezolid (100%) and trimethoprim-sulfamethoxazole (98%). Amikacin (>90% susceptibility for all species except N. transvalensis) was the next most active parenteral agent, superior to both carbapenems and third-generation cephalosporins. Susceptibility to oral antimicrobials (other than linezolid) demonstrated significant interspecies variation. CONCLUSIONS: We demonstrate geographical variation in the distribution of Nocardia incidence. Four species predominate in the Australian setting, and nationwide data confirm a high in vitro susceptibility to trimethoprim-sulphamethoxazole and linezolid, justifying their ongoing role as part of first-line empiric therapy.

Current Epidemiology and Clinical Features of Cryptococcus Infection in Patients Without Human Immunodeficiency Virus: A Multicenter Study in 46 Hospitals in Australia and New Zealand.

BACKGROUND: Patients without human immunodeficiency virus (HIV) are increasingly recognized as being at risk for cryptococcosis. Knowledge of characteristics of cryptococcosis in these patients remains incomplete. METHODS: We conducted a retrospective study of cryptococcosis in 46 Australian and New Zealand hospitals to compare its frequency in patients with and without HIV and describe its characteristics in patients without HIV. Patients with cryptococcosis between January 2015 and December 2019 were included. RESULTS: Of 475 patients with cryptococcosis, 90% were without HIV (426 of 475) with marked predominance in both Cryptococcus neoformans (88.7%) and Cryptococcus gattii cases (94.3%). Most patients without HIV (60.8%) had a known immunocompromising condition: cancer (n = 91), organ transplantation (n = 81), or other immunocompromising condition (n = 97). Cryptococcosis presented as incidental imaging findings in 16.4% of patients (70 of 426). The serum cryptococcal antigen test was positive in 85.1% of tested patients (319 of 375); high titers independently predicted risk of central nervous system involvement. Lumbar puncture was performed in 167 patients to screen for asymptomatic meningitis, with a positivity rate of 13.2% where meningitis could have been predicted by a high serum cryptococcal antigen titer and/or fungemia in 95% of evaluable cases. One-year all-cause mortality was 20.9% in patients without HIV and 21.7% in patients with HIV (P = .89). CONCLUSIONS: Ninety percent of cryptococcosis cases occurred in patients without HIV (89% and 94% for C. neoformans and C. gattii, respectively). Emerging patient risk groups were evident. A high level of awareness is warranted to diagnose cryptococcosis in patients without HIV.

Human Neural Larva Migrans Caused by Ophidascaris robertsi Ascarid.

We describe a case in Australia of human neural larva migrans caused by the ascarid Ophidascaris robertsi, for which Australian carpet pythons are definitive hosts. We made the diagnosis after a live nematode was removed from the brain of a 64-year-old woman who was immunosuppressed for a hypereosinophilic syndrome diagnosed 12 months earlier.

Public health interventions successfully mitigated multiple incursions of SARS-CoV-2 Delta variant in the Australian Capital Territory.

The COVID-19 pandemic has presented a unique opportunity to understand how real-time pathogen genomics can be used for large-scale outbreak investigations. On 12 August 2021, the Australian Capital Territory (ACT) detected an incursion of the SARS-CoV-2 Delta (B.1.617.2) variant. Prior to this date, SARS-CoV-2 had been eliminated locally since 7 July 2020. Several public health interventions were rapidly implemented in response to the incursion, including a territory-wide lockdown and comprehensive contact tracing. The ACT has not previously used pathogen genomics at a population level in an outbreak response; therefore, this incursion also presented an opportunity to investigate the utility of genomic sequencing to support contact tracing efforts in the ACT. Sequencing of >75% of the 1793 laboratory-confirmed cases during the 3 months following the initial notification identified at least 13 independent incursions with onwards spread in the community. Stratification of cases by genomic cluster revealed that distinct cohorts were affected by the different incursions. Two incursions resulted in most of the community transmission during the study period, with persistent transmission in vulnerable sections of the community. Ultimately, both major incursions were successfully mitigated through public health interventions, including COVID-19 vaccines. The high rates of SARS-CoV-2 sequencing in the ACT and the relatively small population size facilitated detailed investigations of the patterns of virus transmission, revealing insights beyond those gathered from traditional contact tracing alone. Genomic sequencing was critical to disentangling complex transmission chains to target interventions appropriately.

Campylobacter-associated hospitalisations in an Australian provincial setting.

BACKGROUND: Campylobacter spp. infections are a globally important cause of enterocolitis, causing substantial morbidity. Capturing accurate information on hospitalisations is challenging and limited population-level data exist to describe the clinico-epidemiological characteristics of hospitalised cases. METHODS: Hospital administrative and laboratory datasets were linked to identify Campylobacter-associated hospitalisations between 2004 and 2013. Accuracy of morbidity coding was assessed using laboratory diagnosis as a gold standard, with health department surveillance data used to calculate population-based rates. Additional patient-level data were collected via review of medical records. Descriptive statistics were used to assess changes in rates and proportions and to assess relationships between key variables including age, length of stay, comorbidity and complications. RESULTS: In total 685 Campylobacter-associated hospital admissions were identified, with the sensitivity of morbidity coding 52.8% (95% CI 48.9-56.7%). The mean annual rate of hospitalisation was 13.6%. Hospitalisation rates were higher for females across most age-groups, while for both genders marked increases were observed for those aged ≥60 years. Median admission age was 39.5 years, with an average length of stay of 3.5 days. Comorbidities were present in 34.5% (237/685) of admissions, with these patients more likely to develop electrolyte disturbances, hypotension, renal impairment or acute confusion (all p < 0.001). Bacteraemia and acute kidney injury were observed in 4.1% (28/685) and 3.6% (23/685) of admissions, respectively. Inpatient mortality was low (0.15%). CONCLUSION: Under reporting of Campylobacter-associated hospitalisations is substantial but can be improved through data linkage. We observed demographic differences among those hospitalised but further work is needed to determine risk factors and predictors for hospitalisation.

Bacteraemia, antimicrobial susceptibility and treatment among Campylobacter-associated hospitalisations in the Australian Capital Territory: a review.

BACKGROUND: Campylobacter spp. cause mostly self-limiting enterocolitis, although a significant proportion of cases require hospitalisation highlighting potential for severe disease. Among people admitted, blood culture specimens are frequently collected and antibiotic treatment is initiated. We sought to understand clinical and host factors associated with bacteraemia, antibiotic treatment and isolate non-susceptibility among Campylobacter-associated hospitalisations. METHODS: Using linked hospital microbiology and administrative data we identified and reviewed Campylobacter-associated hospitalisations between 2004 and 2013. We calculated population-level incidence for Campylobacter bacteraemia and used logistic regression to examine factors associated with bacteraemia, antibiotic treatment and isolate non-susceptibility among Campylobacter-associated hospitalisations. RESULTS: Among 685 Campylobacter-associated hospitalisations, we identified 25 admissions for bacteraemia, an estimated incidence of 0.71 cases per 100,000 population per year. Around half of hospitalisations (333/685) had blood culturing performed. Factors associated with bacteraemia included underlying liver disease (aOR 48.89, 95% CI 7.03-340.22, p < 0.001), Haematology unit admission (aOR 14.67, 95% CI 2.99-72.07, p = 0.001) and age 70-79 years (aOR 4.93, 95% CI 1.57-15.49). Approximately one-third (219/685) of admissions received antibiotics with treatment rates increasing significantly over time (p < 0.05). Factors associated with antibiotic treatment included Gastroenterology unit admission (aOR 3.75, 95% CI 1.95-7.20, p < 0.001), having blood cultures taken (aOR 2.76, 95% CI 1.79-4.26, p < 0.001) and age 40-49 years (aOR 2.34, 95% CI 1.14-4.79, p = 0.02). Non-susceptibility of isolates to standard antimicrobials increased significantly over time (p = 0.01) and was associated with overseas travel (aOR 11.80 95% CI 3.18-43.83, p < 0.001) and negatively associated with tachycardia (aOR 0.48, 95%CI 0.26-0.88, p = 0.02), suggesting a healthy traveller effect. CONCLUSIONS: Campylobacter infections result in considerable hospital burden. Among those admitted to hospital, an interplay of factors involving clinical presentation, presence of underlying comorbidities, complications and increasing age influence how a case is investigated and managed.

Consensus guidelines for the diagnosis and management of invasive fungal disease due to moulds other than Aspergillus in the haematology/oncology setting, 2021.

Invasive fungal disease (IFD) due to moulds other than Aspergillus is a significant cause of mortality in patients with malignancies or post haemopoietic stem cell transplantation. The current guidelines focus on the diagnosis and management of the common non-Aspergillus moulds (NAM), such as Mucorales, Scedosporium species (spp.), Lomentospora prolificans and Fusarium spp. Rare but emerging NAM including Paecilomyces variotii, Purpureocillium lilacinum and Scopulariopsis spp. are also reviewed. Culture and histological examination of tissue biopsy specimens remain the mainstay of diagnosis, but molecular methods are increasingly being used. As NAM frequently disseminate, blood cultures and skin examination with biopsy of any suspicious lesions are critically important. Treatment requires a multidisciplinary approach with surgical debridement as a central component. Other management strategies include control of the underlying disease/predisposing factors, augmentation of the host response and the reduction of immunosuppression. Carefully selected antifungal therapy, guided by susceptibility testing, is critical to cure. We also outline novel antifungal agents still in clinical trial which offer substantial potential for improved outcomes in the future. Paediatric recommendations follow those of adults. Ongoing epidemiological research, improvement in diagnostics and the development of new antifungal agents will continue to improve the poor outcomes that have been traditionally associated with IFD due to NAM.

Risk factors for candidaemia: A prospective multi-centre case-control study.

OBJECTIVES: Candidaemia carries a mortality of up to 40% and may be related to increasing complexity of medical care. Here, we determined risk factors for the development of candidaemia. METHODS: We conducted a prospective, multi-centre, case-control study over 12 months. Cases were aged ≥18 years with at least one blood culture positive for Candida spp. Each case was matched with two controls, by age within 10 years, admission within 6 months, admitting unit, and admission duration at least as long as the time between admission and onset of candidaemia. RESULTS: A total of 118 incident cases and 236 matched controls were compared. By multivariate analysis, risk factors for candidaemia included neutropenia, solid organ transplant, significant liver, respiratory or cardiovascular disease, recent gastrointestinal, biliary or urological surgery, central venous access device, intravenous drug use, urinary catheter and carbapenem receipt. CONCLUSIONS: Risk factors for candidaemia derive from the infection source, carbapenem use, host immune function and organ-based co-morbidities. Preventive strategies should target iatrogenic disruption of mucocutaneous barriers and intravenous drug use.

Factors affecting the presence, genetic diversity and antimicrobial sensitivity of Escherichia coli in poultry meat samples collected from Canberra, Australia.

To investigate the factors determining the clonal composition of Escherichia coli in poultry meat samples, 306 samples were collected from 16 shops, representing three supermarket chains and an independent butchery located in each of the four town centers of Canberra, Australia, during the summer, autumn and winter. A total of 3415 E. coli isolates were recovered and assigned to a phylogenetic group using the Clermont quadruplex PCR method, fingerprinted using repetitive element palindromic (REP) PCR and screened for their antimicrobial susceptibility profiles. The probability of detecting E. coli and the number of fingerprint types detected per sample, as well as the phylogroup membership of the isolates and their antimicrobial sensitivity profiles varied, with one or more of retailer, store, meat type, season and husbandry. The results of this study demonstrate that poultry meat products are likely to be contaminated with a genetically diverse community of E. coli and suggest that factors relating to the nature of the meat product and distribution chain are determinants of the observed diversity.

Epidemiology of non-typhoid Salmonella infection in the Australian Capital Territory over a 10-year period.

AIM: To describe the epidemiology of non-typhoid Salmonella (NTS) infection in the Australian Capital Territory (ACT), including factors associated with hospitalisation. METHODS: This was a retrospective descriptive and observational study of culture-confirmed NTS infections using data collected from ACT public health, public pathology and hospital services in the period 2003-2012. Outcome measures include incidence and NTS serotype for total reported and hospitalised cases and focus of infection, complications and antibiotic susceptibility for hospitalised cases. RESULTS: In total, 1469 cases of NTS infection were reported, with the crude annual incidence increasing from 24.4 to 61.3 cases per 100 000 population; 14% were hospitalised, representing an incidence of 5.9 hospitalisations per 100 000 population, without significant change over time. Hospitalisation incidence peaked at the extremes of age. Comorbid disease and age ≥ 80 years were associated with complications during hospitalisation. Salmonella serotype Typhimurium was the most common serotype, accounting for 64% of NTS. Independent risk factors for invasive disease included non-S. Typhimurium serotype (aRR 5.46, 95%CI 1.69-17.65 P = 0.005), ischaemic heart disease (aRR 4.18, 95%CI 1.20-14.60 P = 0.025) and haematological malignancy (aRR 6.93, 95%CI 2.54-18.94 P < 0.001). Among hospitalised patients, resistance to ampicillin, ceftriaxone, trimethoprim-sulfamethoxazole and quinolones was 9.9%, 0%, 4.4% and 2.5% respectively. CONCLUSIONS: NTS notifications in the ACT have increased over time, with outbreaks of food-borne disease contributing to this increase. Crude age-specific incidence is highest in the very young, while rates of hospitalisation are highest in the elderly. Comorbid disease and infection with a non-S. Typhimurium serotype were associated with complicated NTS disease course. Antimicrobial resistance in NTS is low and has not increased over time.

Changing epidemiology of candidaemia in Australia.

Objectives: Knowledge of contemporary epidemiology of candidaemia is essential. We aimed to identify changes since 2004 in incidence, species epidemiology and antifungal susceptibilities of Candida spp. causing candidaemia in Australia. Methods: These data were collected from nationwide active laboratory-based surveillance for candidaemia over 1 year (within 2014-2015). Isolate identification was by MALDI-TOF MS supplemented by DNA sequencing. Antifungal susceptibility testing was performed using Sensititre YeastOne™. Results: A total of 527 candidaemia episodes (yielding 548 isolates) were evaluable. The mean annual incidence was 2.41/105 population. The median patient age was 63 years (56% of cases occurred in males). Of 498 isolates with confirmed species identity, Candida albicans was the most common (44.4%) followed by Candida glabrata complex (26.7%) and Candida parapsilosis complex (16.5%). Uncommon Candida species comprised 25 (5%) isolates. Overall, C. albicans (>99%) and C. parapsilosis (98.8%) were fluconazole susceptible. However, 16.7% (4 of 24) of Candida tropicalis were fluconazole- and voriconazole-resistant and were non-WT to posaconazole. Of C. glabrata isolates, 6.8% were resistant/non-WT to azoles; only one isolate was classed as resistant to caspofungin (MIC of 0.5 mg/L) by CLSI criteria, but was micafungin and anidulafungin susceptible. There was no azole/echinocandin co-resistance. Conclusions: We report an almost 1.7-fold proportional increase in C. glabrata candidaemia (26.7% versus 16% in 2004) in Australia. Antifungal resistance was generally uncommon, but azole resistance (16.7% of isolates) amongst C. tropicalis may be emerging.

First case report of myopericarditis linked to Campylobacter coli enterocolitis.

BACKGROUND: Campylobacter spp. are a common cause of mostly self-limiting enterocolitis. Although rare, pericarditis and myopericarditis have been increasingly documented as complications following campylobacteriosis. Such cases have occurred predominantly in younger males, and involved a single causative species, namely Campylobacter jejuni. We report the first case of myopericarditis following Campylobacter coli enterocolitis, with illness occurring in an immunocompetent middle-aged female. CASE PRESENTATION: A 51-yo female was admitted to a cardiology unit with a 3-days history of chest pain. The woman had no significant medical history or risk factors for cardiac disease, nor did she report any recent overseas travel. Four days prior to the commencement of chest pain the woman had reported onset of an acute gastrointestinal illness, passing 3-4 loose stools daily, a situation that persisted at the time of presentation. Physical examination showed the woman's vital signs to be essentially stable, although she was noted to be mildly tachycardic. Laboratory testing showed mildly elevated C-reactive protein and a raised troponin I in the absence of elevation of the serum creatinine kinase. Electrocardiography (ECG) demonstrated concave ST segment elevations, and PR elevation in aVR and depression in lead II. Transthoracic echocardiogram (TTE) revealed normal biventricular size and function with no significant valvular abnormalities. There were no left ventricular regional wall motion abnormalities. No pericardial effusion was present but the pericardium appeared echodense. A diagnosis of myopericarditis was made on the basis of chest pain, typical ECG changes and troponin rise. The chest pain resolved and she was discharged from hospital after 2-days of observation, but with ongoing diarrhoea. Following discharge, a faecal sample taken during the admission, cultured Campylobacter spp. Matrix assisted laser desorption ionization time-of-flight (Bruker) confirmed the cultured isolate as C. coli. CONCLUSION: We report the first case of myopericarditis with a suggested link to an antecedent Campylobacter coli enterocolitis. Although rare, myopericarditis is becoming increasingly regarded as a complication following campylobacteriosis. Our report highlights potential for pericardial disease beyond that attributed to Campylobacter jejuni. However uncertainty regarding pathogenesis, coupled with a paucity of population level data continues to restrict conclusions regarding the strength of this apparent association.

Genomic Characteristics of NDM-Producing Enterobacteriaceae Isolates in Australia and Their blaNDM Genetic Contexts.

blaNDM has been reported in different Enterobacteriaceae species and on numerous plasmid replicon types (Inc). Plasmid replicon typing, in combination with genomic characteristics of the bacterial host (e.g., sequence typing), is used to infer the spread of antimicrobial resistance determinants between genetically unrelated bacterial hosts. The genetic context of blaNDM is heterogeneous. In this study, we genomically characterized 12 NDM-producing Enterobacteriaceae isolated in Australia between 2012 and 2014: Escherichia coli (n = 6), Klebsiella pneumoniae (n = 3), Enterobacter cloacae (n = 2) and Providencia rettgeri (n = 1). We describe their blaNDM genetic contexts within Tn125, providing insights into the acquisition of blaNDM into Enterobacteriaceae. IncFII-type (n = 7) and IncX3 (n = 4) plasmids were the most common plasmid types found. The IncHI1B (n = 1) plasmid was also identified. Five different blaNDM genetic contexts were identified, indicating four particular plasmids with specific blaNDM genetic contexts (NGCs), three of which were IncFII plasmids (FII-A to -C). Of note, the blaNDM genetic context of P. rettgeri was not conjugative. Epidemiological links between our NDM-producing Enterobacteriaceae were established by their acquisition of these five particular plasmid types. The combination of different molecular and genetic characterization methods allowed us to provide insight into the spread of plasmids transmitting blaNDM.

Phylogenetic diversity, antimicrobial susceptibility and virulence characteristics of phylogroup F Escherichia coli in Australia.

Unlike Escherichia coli strains belonging to phylogroup B2, the clinical significance of strains belonging to phylogroup F is not well understood. Here we report on a collection of phylogroup F strains recovered in Australia from faeces and extra-intestinal sites from humans, companion animals and native animals, as well as from poultry meat and water samples. The distribution of sequence types was clearly non-random with respect to isolate source. The antimicrobial resistance and virulence trait profiles also varied with the sequence type of the isolate. Phylogroup F strains tended to lack the virulence traits typically associated with phylogroup B2 strains responsible for extra-intestinal infection in humans. Resistance to fluoroquinolones and/or expanded-spectrum cephalosporins was common within ST648, ST354 and ST3711. Although ST354 and ST3711 are part of the same clonal complex, the ST3711 isolates were only recovered from native birds being cared for in a single wildlife rehabilitation centre, whereas the ST354 isolates were from faeces and extra-intestinal sites of dogs and humans, as well as from poultry meat. Although ST354 isolates from chicken meat in Western Australia were distinct from all other ST354 isolates, those from poultry meat samples collected in eastern Australia shared many similarities with other ST354 isolates from humans and companion animals.

Increasing incidence of Clostridium difficile infection, Australia, 2011-2012.

OBJECTIVES: To report the quarterly incidence of hospital-identified Clostridium difficile infection (HI-CDI) in Australia, and to estimate the burden ascribed to hospital-associated (HA) and community-associated (CA) infections. DESIGN, SETTING AND PATIENTS: Prospective surveillance of all cases of CDI diagnosed in hospital patients from 1 January 2011 to 31 December 2012 in 450 public hospitals in all Australian states and the Australian Capital Territory. All patients admitted to inpatient wards or units in acute public hospitals, including psychiatry, rehabilitation and aged care, were included, as well as those attending emergency departments and outpatient clinics. MAIN OUTCOME MEASURES: Incidence of HI-CDI (primary outcome); proportion and incidence of HA-CDI and CA-CDI (secondary outcomes). RESULTS: The annual incidence of HI-CDI increased from 3.25/10 000 patient-days (PD) in 2011 to 4.03/10 000 PD in 2012. Poisson regression modelling demonstrated a 29% increase (95% CI, 25% to 34%) per quarter between April and December 2011, with a peak of 4.49/10 000 PD in the October-December quarter. The incidence plateaued in January-March 2012 and then declined by 8% (95% CI, - 11% to - 5%) per quarter to 3.76/10 000 PD in July-September 2012, after which the rate rose again by 11% (95% CI, 4% to 19%) per quarter to 4.09/10 000 PD in October-December 2012. Trends were similar for HA-CDI and CA-CDI. A subgroup analysis determined that 26% of cases were CA-CDI. CONCLUSIONS: A significant increase in both HA-CDI and CA-CDI identified through hospital surveillance occurred in Australia during 2011-2012. Studies are required to further characterise the epidemiology of CDI in Australia.

Genomic Surveillance of Invasive Meningococcal Disease During a National MenW Outbreak in Australia, 2017-2018.

Background: In Australia, invasive meningococcal disease (IMD) incidence rapidly increased between 2014 and 2017 due to rising serogroup W (MenW) and MenY infections. We aimed to better understand the genetic diversity of IMD during 2017 and 2018 using whole genome sequencing data. Methods: Whole genome sequencing data from 440 Australian IMD isolates collected during 2017 and 2018 and 1737 international MenW:CC11 isolates collected in Europe, Africa, Asia, North America, and South America between 1974 and 2020 were used in phylogenetic analyses; genetic relatedness was determined from single-nucleotide polymorphisms. Results: Australian isolates were as follows: 181 MenW (41%), 144 MenB (33%), 88 MenY (20%), 16 MenC (4%), 1 MenW/Y (0.2%), and 10 nongenogroupable (2%). Eighteen clonal complexes (CCs) were identified, and 3 (CC11, CC23, CC41/44) accounted for 78% of isolates (343/440). These CCs were associated with specific serogroups: CC11 (n = 199) predominated among MenW (n = 181) and MenC (n = 15), CC23 (n = 80) among MenY (n = 78), and CC41/44 (n = 64) among MenB (n = 64). MenB isolates were highly diverse, MenY were intermediately diverse, and MenW and MenC isolates demonstrated the least genetic diversity. Thirty serogroup and CC-specific genomic clusters were identified. International CC11 comparison revealed diversification of MenW in Australia. Conclusions: Whole genome sequencing comprehensively characterized Australian IMD isolates, indexed their genetic variability, provided increased within-CC resolution, and elucidated the evolution of CC11 in Australia.

Off-season RSV epidemics in Australia after easing of COVID-19 restrictions.

Human respiratory syncytial virus (RSV) is an important cause of acute respiratory infection with the most severe disease in the young and elderly. Non-pharmaceutical interventions and travel restrictions for controlling COVID-19 have impacted the circulation of most respiratory viruses including RSV globally, particularly in Australia, where during 2020 the normal winter epidemics were notably absent. However, in late 2020, unprecedented widespread RSV outbreaks occurred, beginning in spring, and extending into summer across two widely separated regions of the Australian continent, New South Wales (NSW) and Australian Capital Territory (ACT) in the east, and Western Australia. Through genomic sequencing we reveal a major reduction in RSV genetic diversity following COVID-19 emergence with two genetically distinct RSV-A clades circulating cryptically, likely localised for several months prior to an epidemic surge in cases upon relaxation of COVID-19 control measures. The NSW/ACT clade subsequently spread to the neighbouring state of Victoria and to cause extensive outbreaks and hospitalisations in early 2021. These findings highlight the need for continued surveillance and sequencing of RSV and other respiratory viruses during and after the COVID-19 pandemic, as mitigation measures may disrupt seasonal patterns, causing larger or more severe outbreaks.

Antibiotic stability in commercial peritoneal dialysis solutions: influence of formulation, storage and duration.

BACKGROUND: Peritoneal dialysis (PD)-associated peritonitis is treated by administration of antibiotics mixed with the PD solution. Data on antibiotic stability for solutions in current use are limited. The aim of this study was to determine the stability of cefepime, cephazolin and ampicillin in three commercial PD solutions. METHODS: Antibiotics were added to the non-glucose compartment of the Gambro (Gambrosol®) and Fresenius (Balance®) multi-compartment systems and Baxter (Dianeal®) single-compartment (glucose 2.5%) PD solutions in a sterile suite. Antibiotic stability over 3 weeks was determined using both a bioassay of bacterial inhibition and antibiotic concentrations. The influence on stability and sterility of storage conditions was determined. RESULTS: The bioassay demonstrated the stability of all antibiotics for 9 days at room temperature and 3 weeks when refrigerated, except ampicillin in the Gambro solution, which displayed no bioactivity after 4 days. However, a ceiling effect in bacterial inhibition at higher antibiotic concentrations limited the ability of the bioassay to detect antibiotic degradation at relevant concentrations. Antibiotic concentrations varied with time but were comparable to the bioassay and supported stability in refrigerated solutions, except ampicillin in the Gambro solution. No bacterial contamination, marked colour change or precipitation occurred. CONCLUSIONS: This study supports the stability of cephazolin and cefepime in all three PD solutions and ampicillin in only the Baxter and Fresenius PD solutions. Antibiotic stability studies should ideally be conducted prior to registration and marketing of new PD solutions.