Paediatric bacteraemias in tropical Australia

Antimicrobial Resistance in Staphylococcus aureus and Enterococcus spp. Isolates From Bloodstream Infections in Australian Children, 2013-2021

BACKGROUND

Rising proportions of antimicrobial resistance (AMR) have been observed in both Staphylococcus aureus and Enterococcus spp. isolates.

METHODS

The Australian Group on Antimicrobial Resistance surveillance program captures clinical and microbiological data of isolates detected in blood cultures across Australia. EUCAST 2022 was used for interpretation and the AMR package in R for data analysis.

RESULTS

There were 2091 bloodstream infections (BSIs) with S. aureus and 534 enterococcal BSI episodes in children <18 years old over 9 years. Three quarters of S. aureus BSI episodes were community-onset (78.3%), while more than half of enterococcal BSIs were hospital-onset (56.9%). The median age for S. aureus BSIs was 6 years, while >50% of enterococcal BSIs were in children <12 months old. Fifteen percent of S. aureus isolates were methicillin-resistant. Overall, 85.3% of S. aureus were resistant to penicillin, 12.5% resistant to erythromycin, 10.3% to clindamycin, and 4.7% to ciprofloxacin. Resistance to penicillin decreased over time, while clindamycin resistance increased. Resistance in Enterococcus spp. was almost entirely observed in Enterococcus faecium; only 1 Enterococcus faecalis isolate was ampicillin-resistant, and no E. faecalis isolates were vancomycin or teicoplanin-resistant. Seventy-three percent of E. faecium were resistant to ampicillin, 25.5% to vancomycin (VREfm), and 8.8% to teicoplanin.

CONCLUSIONS

Significant shifts in the epidemiology and resistance profiles of S. aureus and Enterococcus spp. BSIs in Australian children were observed, making clear the importance of age-stratified reporting in AMR data.

Bacteraemia in Tropical Australia: A Review

Purpose of Review

This review discusses the trends of bacteraemia and their outcomes in tropical regions of Australia. Bacteraemia can frequently lead to severe sepsis and potentially life-threatening consequences. Epidemiology of bacteraemia is ever evolving.

Recent Findings

This review outlines the current patterns of bacteraemia in tropical regions of Australia, focusing on their outcomes and associated risk factors. The most frequently reported causes of bacteraemia were Staphylococcus aureus and Escherichia coli. There has been an increase in published incidence of Group A Streptococcus, methicillin-resistant Staphylococcus aureus and Burkholderia pseudomallei bacteraemia cases, while Streptococcus pneumoniae bacteraemia exhibited a declining trend. Factors specific to tropical environments and the higher representation of Indigenous populations in these areas were identified as contributing to the elevated incidence rates.

Summary

Bacteraemia was found to be an increasing healthcare burden to the Australian tropical regions. Ideally, linkage of existing data from healthcare settings could be utilised to obtain more accurate, comprehensive and up to date information of trends and patterns of bacteraemia.

Culture-proven Bloodstream Infections at a Specialist Pediatric Hospital

BACKGROUND

Bloodstream infection (BSI) is one of the leading causes of morbidity and mortality in children. This study was done to assess the local epidemiology and outcome of BSIs managed at a large specialist pediatric hospital with a focus on community-onset BSI.

METHODS

We retrospectively reviewed laboratory-confirmed BSI in children (0-18 years) at The Children's Hospital at Westmead over a 3-year period (2014-2016). Laboratory data and patient medical records were used to determine BSI rates, blood culture contamination rates, patient demographics, isolate profile, antimicrobial resistance and mortality rate in this cohort.

RESULTS

In total, 47,368 blood cultures were collected; 1027 (2.2%) grew probable contaminants and 991 (2.1%) grew clinically significant isolates. Clinically significant bacteremia accounted for 4.8 per 1000 admissions, with 391 children managed for 465 culture-proven BSI episodes. One hundred thirty-one (28.2%) episodes were community-onset community-associated, and 334 (71.8%) were either community-onset healthcare-associated (HCA) (187; 40.2 %) or hospital-onset (147; 31.6%). Of the significant isolates, 243 (52.3%) were Gram-positive bacteria, 198 (42.6%) were Gram-negative bacteria, 6 (1.3%) were polymicrobial infections and 18 (3.9%) were yeast. Staphylococcus aureus (115; 24.7%) and Escherichia coli (54; 11.6%) were the most common organisms identified. Osteoarticular infection (44; 33.6%) and urosepsis (23; 17.6%) were the most frequent sites of infection associated with non-HCA BSI. Mortality at 30 days was reported in 15 (3.3%) children, all whom had preexisting comorbidities.

CONCLUSIONS

The majority of BSI episodes managed in our hospital were either community-onset HCA or hospital-onset infections. This highlights the considerable importance of infection control and central venous catheter device care initiatives. Among community-associated BSI, S. aureus in association with osteoarticular infection was predominant.

Paediatric Salmonellosis-Differences between Tropical and Sub-Tropical Regions of Queensland, Australia

Salmonellosis is an important cause of morbidity in tropical regions.This study aims to describe the epidemiology of non-typhoidal Salmonellae (NTS) in children presenting to public hospitals in Queensland, Australia, over the past 20 years, with a focus on differences between tropical and sub-tropical zones in the region. This is a retrospective and descriptive cohort study of 8162 NTS positive samples collected in 0–17-year-olds from the Queensland public hospital pathology database (Auslab) over a 20-year period from 1997 to 2016. There were 2951 (36.2%) positive NTS samples collected in tropical zones and 5211 (63.8%) in the sub-tropical zones of Queensland, with a total of 8162 over the region. The tropical zone contributed a disproportionately higher number of positive NTS samples by population sub-analysis. Of the specimens collected, 7421 (90.92%) were faecal, 505 (6.2%) blood, 161 (1.97%) urine, 13 (0.16%) cerebrospinal fluid (CSF) and 62 of other origin. Other categories of specimen types isolated include swab, fluid, aspirate, lavage, bone, tissue, isolate and pus, and these were not included in sub-analysis. The most commonly identified serovars were Salmonella Typhimurium, Salmonella Virchow and Salmonella Saintpaul. This is the first and largest study that emphasises the high burden of invasive and non-invasive NTS infections resulting in hospital presentations in the paediatric population of tropical north Queensland, compared to the sub-tropics.

Pediatric bloodstream infections in metropolitan Australia

BACKGROUND

Bloodstream infections (BSIs) cause significant morbidity and mortality of children worldwide. The aim of this study was to investigate BSI in children and determine the identity of causative organism and their susceptibility patterns in a metropolitan public hospital in Australia.

METHODS

We retrospectively reviewed children aged 0-16 years admitted to a public hospital from January 1, 2010 to August 31, 2014 inclusive, and whose blood cultures revealed bacteraemia. Data were collected regarding patient demographics, species of bacteria isolated, antimicrobial susceptibility of these isolates, and clinical outcomes.

RESULTS

Out of 96 patients with BSI, 55 (57.3%) were males. The median age was 3.35 years (IQR 0.44-7.46), and there were 2 mortalities. Common sites of infection were the respiratory tract (16.6%, n = 16), bone and joints (15.6%, n = 15) and the urinary tract (11.5%, n = 11). The most frequent isolates were Staphylococcus aureus (27.0%), Escherichia coli (14.0%) and Streptococcus pneumoniae (12.0%). Whilst most bacterial isolates displayed susceptibility (> 90%) to common antimicrobial agents, only 57.1% (8/14) of Escherichia coli isolates were susceptible to ampicillin and 58.3% (7/12) were susceptible to co-trimoxazole.

CONCLUSIONS

Gram-positive bacteria accounted for the majority of pediatric BSIs, of which invasive pneumococcal disease remains a noteworthy cause. The majority of isolates, except Escherichia coli, were susceptible to commonly used antimicrobials. This study confirms the knowledge of high rates of resistance of Escherichia coli to ampicillin. Therefore, empirical treatment should still include gentamicin. Monitoring of resistance patterns is warranted to ensure that antibiotic therapy remains appropriate.

Paediatric thoracic empyema in the tropical North Queensland region of Australia: Epidemiological trends over a decade

AIM

The Townsville Hospital and Health Service is the regional referral centre for children in the north of Queensland. Aboriginal and Torres Strait Islander (ATSI) people make up 7-10% of the population. Increasing numbers of children with paediatric thoracic empyema (pTE) are being referred to Townsville Hospital and Health Service for management. This study aims to describe the incidence rates, epidemiology, microbiology and trends of this disease in North Queensland over a 10-year period.

METHODS

A retrospective chart review of all children (1 month to 16 years), admitted in the years 2007-2016, with community-acquired pTE was conducted. International Classification of Diseases codes were used to identify the patients. Epidemiological and microbiological data were extracted from records.

RESULTS

Of the 123 cases identified, incidence rates per 100 000 were 8.5 (95% confidence interval (CI) 8.4-8.6) in all children and much higher at 19.8 (95% CI: 19.5-21.9) in ATSI children. The under 5 years age group had the highest rate (24.5; 95% CI: 24.4-24.6). There was a progressive rise in incidence during the 10-year period, with the highest incidence of 15.2 (95% CI: 15.1-15.2) occurring in 2016. A pathogen was isolated in 76% of cases. Non-multi-resistant methicillin-resistant Staphylococcus aureus was the most common pathogen isolated in 22 of 64 ATSI children (34%), while Streptococcus pneumoniae was the most common pathogen isolated in 27 of 59 non-ATSI children (46%).

CONCLUSIONS

A high and increasing incidence of pTE in North Queensland is being observed. ATSI children have higher incidence rates and are more likely to have non-multi-resistant methicillin-resistant Staphylococcus aureus as a causative agent.

Detection of Typhoidal and Paratyphoidal Salmonella in Blood by Real-time Polymerase Chain Reaction

BACKGROUND

The gold standard for diagnosis of enteric fever caused by Salmonella Typhi or Salmonella Paratyphi A or B is bone marrow culture. However, because bone marrow aspiration is highly invasive, many hospitals and large health centers perform blood culture instead. As blood culture has several limitations, there is a need for novel typhoid diagnostics with improved sensitivity and more rapid time to detection.

METHODS

We developed a clyA-based real-time polymerase chain reaction (qPCR) method to detect Salmonella Typhi and Salmonella Paratyphi A simultaneously in blood. The sensitivity and specificity of this probeset was first evaluated in vitro in the laboratory and then in a typhoid-endemic population, in Karachi, Pakistan, and in healthy US volunteers.

RESULTS

We optimized a DNA extraction and real-time PCR-based method that could reliably detect 1 colony-forming unit/mL of Salmonella Typhi. The probe set was able to detect clinical Salmonella Typhi and Salmonella Paratyphi A strains and also diarrheagenic Escherichia coli, but not invasive E. coli or other invasive bacteria. In the field, the clyA qPCR diagnostic was 40% as sensitive as blood culture. However, when qPCR-positive specimens were considered to be true positives, blood culture only exhibited 28.57% sensitivity. Specificity was ≥90% for all comparisons and in the healthy US volunteers. qPCR was significantly faster than blood culture in terms of detection of typhoid and paratyphoid.

CONCLUSIONS

Based on lessons learned, we recommend that future field trials of this and other novel diagnostics that detect typhoidal and nontyphoidal Salmonella employ multiple methodologies to define a "positive" sample.

Antibacterial activity and mechanism of action of auranofin against multi-drug resistant bacterial pathogens

Traditional methods employed to discover new antibiotics are both a time-consuming and financially-taxing venture. This has led researchers to mine existing libraries of clinical molecules in order to repurpose old drugs for new applications (as antimicrobials). Such an effort led to the discovery of auranofin, a drug initially approved as an anti-rheumatic agent, which also possesses potent antibacterial activity in a clinically achievable range. The present study demonstrates auranofin’s antibacterial activity is a complex process that involves inhibition of multiple biosynthetic pathways including cell wall, DNA, and bacterial protein synthesis. We also confirmed that the lack of activity of auranofin observed against Gram-negative bacteria is due to the permeability barrier conferred by the outer membrane. Auranofin’s ability to suppress bacterial protein synthesis leads to significant reduction in the production of key methicillin-resistant Staphylococcus aureus (MRSA) toxins. Additionally, auranofin is capable of eradicating intracellular MRSA present inside infected macrophage cells. Furthermore, auranofin is efficacious in a mouse model of MRSA systemic infection and significantly reduces the bacterial load in murine organs including the spleen and liver. Collectively, this study provides valuable evidence that auranofin has significant promise to be repurposed as a novel antibacterial for treatment of invasive bacterial infections.