Raising the Stakes: Loss of Efflux Pump Regulation Decreases Meropenem Susceptibility in Burkholderia pseudomallei.

Background: Burkholderia pseudomallei, the causative agent of the high-mortality disease melioidosis, is a gram-negative bacterium that is naturally resistant to many antibiotics. There is no vaccine for melioidosis, and effective eradication is reliant on biphasic and prolonged antibiotic administration. The carbapenem drug meropenem is the current gold standard option for treating severe melioidosis. Intrinsic B. pseudomallei resistance toward meropenem has not yet been documented; however, resistance could conceivably develop over the course of infection, leading to prolonged sepsis and treatment failure. Methods: We examined our 30-year clinical collection of melioidosis cases to identify B. pseudomallei isolates with reduced meropenem susceptibility. Isolates were subjected to minimum inhibitory concentration (MIC) testing toward meropenem. Paired isolates from patients who had evolved decreased susceptibility were subjected to whole-genome sequencing. Select agent-compliant genetic manipulation was carried out to confirm the molecular mechanisms conferring resistance. Results: We identified 11 melioidosis cases where B. pseudomallei isolates developed decreased susceptibility toward meropenem during treatment, including 2 cases not treated with this antibiotic. Meropenem MICs increased from 0.5-0.75 µg/mL to 3-8 µg/mL. Comparative genomics identified multiple mutations affecting multidrug resistance-nodulation-division (RND) efflux pump regulators, with concomitant overexpression of their corresponding pumps. All cases were refractory to treatment despite aggressive, targeted therapy, and 2 were associated with a fatal outcome. Conclusions: This study confirms the role of RND efflux pumps in decreased meropenem susceptibility in B. pseudomallei. These findings have important ramifications for the diagnosis, treatment, and management of life-threatening melioidosis cases.

Molecular Antimicrobial Resistance Surveillance for Neisseria gonorrhoeae, Northern Territory, Australia.

Neisseria gonorrhoeae antimicrobial resistance (AMR) is a globally recognized health threat; new strategies are needed to enhance AMR surveillance. The Northern Territory of Australia is unique in that 2 different first-line therapies, based primarily on geographic location, are used for gonorrhea treatment. We tested 1,629 N. gonorrhoeae nucleic acid amplification test-positive clinical samples, collected from regions where ceftriaxone plus azithromycin or amoxicillin plus azithromycin are recommended first-line treatments, by using 8 N. gonorrhoeae AMR PCR assays. We compared results with those from routine culture-based surveillance data. PCR data confirmed an absence of ceftriaxone resistance and a low level of azithromycin resistance (0.2%), and that penicillin resistance was <5% in amoxicillin plus azithromycin regions. Rates of ciprofloxacin resistance and penicillinase-producing N. gonorrhoeae were lower when molecular methods were used. Molecular methods to detect N. gonorrhoeae AMR can increase the evidence base for treatment guidelines, particularly in settings where culture-based surveillance is limited.

Seasonal variability of respiratory syncytial virus infection in the Top End of the Northern Territory (2012-2014).

AIM: To determine the prevalence of respiratory syncytial virus (RSV) in the Top End of the Northern Territory and investigate potential drivers of seasonality including rainfall and humidex (humidity and heat index). METHODS: We performed a retrospective audit of laboratory confirmed cases of RSV from January 2012 to August 2014. Demographic details including age, sex and ethnicity were examined. RSV cases were correlated with monthly rainfall and humidex. RESULTS: There were 272 positive isolates detected from 4305 clinical samples (positivity rate 6.3%). The majority of cases occurred in children <12 months (n = 151, 55.5%), with a higher burden of disease seen in Indigenous compared to non-Indigenous infants in this age category (P < 0.005). The prevalence of RSV in the 0-5 years age category was 58/10 000 children per annum. Indigenous patients had higher prevalence rates (88.8/10 000 population per annum) and younger onset of infection (7.5 months; Interquartile range (IQR) 3-19 months compared to 13 months for non-Indigenous children; IQR 5 months to 2.4 years). RSV cases correlated most strongly with rainfall in the preceding month (r = 0.72). CONCLUSIONS: The Top End of the Northern Territory has a distinct RSV season that correlates with rainfall and humidex, which differs from Southern Australian disease patterns.

Clinical presentation and medical management of melioidosis in children: a 24-year prospective study in the Northern Territory of Australia and review of the literature.

BACKGROUND: Melioidosis is less common in children than adults. The clinical spectrum of disease varies greatly between the 2 groups. Treatment guidelines are currently based on adult studies, and revision of existing guidelines is necessary to instruct specific pediatric management. METHODS: Culture-confirmed cases of melioidosis in the Northern Territory between 1989 and 2013 were identified from the Prospective Melioidosis Study. The epidemiology and clinical spectrum of disease for children aged ≤ 16 years were analyzed and compared with the adult data. RESULTS: Forty-five pediatric patients were identified, representing 5% of the total 820 melioidosis cases over 24 years. Most children (84%) had no recognized risk factors for melioidosis, and 80% presented during the wet season. Primary cutaneous melioidosis was the commonest presentation in children (60% vs 13%; P < .001), whereas pneumonia predominated in adults (54% vs 20%; P < .001). Bacteremia was less common in children than in adults (16% vs 59%; P < .001). Brainstem encephalitis occurred in 3 children without risk factors. Children were more likely to report an inoculating event (42%; P < .001). There was no difference in mortality between the groups (P = .178), with 3 children dying (7%); all had identifiable risk factors. Four children with cutaneous melioidosis were successfully treated with oral therapy alone, while 2 had skin lesions that resolved spontaneously. CONCLUSIONS: Pediatric melioidosis commonly manifests as localized cutaneous disease in immunocompetent hosts. The disease can be fatal, especially in individuals with risk factors for disease. Melioidosis with encephalomyelitis can result in severe residual disability. Prompt diagnosis requires a high index of clinical suspicion in endemic areas.

Endemic melioidosis in residents of desert region after atypically intense rainfall in central Australia, 2011.

After heavy rains and flooding during early 2011 in the normally arid interior of Australia, melioidosis was diagnosed in 6 persons over a 4-month period. Although the precise global distribution of the causal bacterium Burkholderia pseudomallei remains to be determined, this organism can clearly survive in harsh and even desert environments outside the wet tropics.

Multitarget PCR Assay for Direct Detection of Penicillinase-Producing Neisseria gonorrhoeae for Enhanced Surveillance of Gonococcal Antimicrobial Resistance.

A multitarget PCR was developed for the direct detection of penicillinase-producing Neisseria gonorrhoeae (PPNG). The assay was validated by testing 342 PPNG isolates and 415 clinical samples. The method is suitable for routine detection of PPNG strains. Its multitarget approach reduces the potential for false-negative results caused by sequence variations.

Dwarf tapeworm (Hymenolepis nana): Characteristics in the Northern Territory 2002-2013.

AIM: Review of dwarf tapeworm (Hymenolepis nana) presentations to Northern Territory (NT) Government health-care facilities over 12 years. We postulated H. nana infections would remain unchanged despite the introduction of deworming programmes as H. nana is not eradicated with albendazole treatment. METHODS: A retrospective observational analysis of consecutive microbiologically confirmed cases of H. nana identified by NT Government health-care facilities between 2002 and 2013. RESULTS: Four hundred sixty-one episodes of H. nana infection were identified over the 12-year period from 68 387 faecal samples. Infections were overwhelmingly in young children with a median age of patients being 3.0 years (interquartile range 2.25-4.67). Patients were predominantly Indigenous (98.9%, P = 0.001) and infections occurred across the entire NT. Infections were associated with anaemia (18.2%) and eosinophilia (39.6%). The annual prevalence of NT Government health-care facility diagnosed H. nana infection remains relatively constant from 6.9 {4.8-9.0 (confidence interval (CI))} cases per 10 000 Indigenous population in 2002, compared with 6.6 (4.7-8.4 CI) cases per 10 000 Indigenous population in 2013. Infection rates in Indigenous children <5 years of age were: 46.1 (16.4-75.8 CI) cases/10 000 in 2002, compared with 44.3 (15.3-73.3 CI) cases/10 000 Indigenous population in 2013. CONCLUSION: H. nana is the most frequently identified cestode (tapeworm) in NT Government health-care facilities. H. nana remains endemic throughout the NT, predominantly infecting Indigenous children less than 5 years of age.

ZIKA VIRUS INFECTION IN AUSTRALIA FOLLOWING A MONKEY BITE IN INDONESIA.

A traveller returning to Australia developed Zika virus infection, with fever, rash and conjunctivitis, with onset five days after a monkey bite in Bali, Indonesia. Flavivirus RNA detected on PCR from a nasopharyngeal swab was sequenced and identified as Zika virus. Although mosquito-borne transmission is also possible, we propose the bite as a plausible route of transmission. The literature for non-vector transmissions of Zika virus and other flaviviruses is reviewed.

Recurrent melioidosis in the Darwin Prospective Melioidosis Study: improving therapies mean that relapse cases are now rare.

The Darwin Prospective Melioidosis Study has documented 785 melioidosis cases over 23 years. Recurrent melioidosis occurred in 39/679 (5.7%) patients surviving initial infection; 29 patients suffered relapse of the original infection, and 10 presented with a new Burkholderia pseudomallei infection. With improved therapy, relapse has become rare in recent years.

Clinical Presentation and Outcomes Following Infection With Vibrio spp, Aeromonas spp, Chromobacterium violaceum, and Shewanella spp Water-Associated Organisms in Tropical Australia, 2015-2022.

Background: Water-associated bacterial infections cause a wide spectrum of disease. Although many of these infections are typically due to human host commensal Staphylococcal or Streptococcal spp, water exposure can result in infections with environmental gram negatives such as Vibrio spp, Aeromonas spp, Chromobacterium violaceum, and Shewanella spp (collectively VACS). Methods: We performed a retrospective analysis of the epidemiology, clinical presentation, and outcomes of deep and superficial infections associated with VACS organisms in our health service between 1 January 2015 and 31 December 2023. Results: We identified 317 patient episodes of infection with VACS organisms over this period. Of these, Aeromonas spp (63%) was the most common, followed by Vibrio spp (19%), Shewanella spp (13%), and C violaceum (5%). The majority were isolated from males (74.4%) and involved the lower limb (67.5%). Mild infections were more common than severe presentations, with only 15 (4.7%) admissions to the intensive care unit and 8 (2.5%) deaths. Colonization occurred in 6.9% of patients, in contrast to the perceived severity of some of these bacteria. Copathogens were common and included Staphylococcus aureus (48%) and enteric bacteria (57%). The majority of patients (60%) had no documented water exposure. Initial empiric antimicrobial therapy presumptively covered the susceptibilities of the isolated organisms in 47.3% of patients; however, a lack of VACS-covering empirical therapy was not associated with readmission. Conclusions: The isolation of a VACS organism in our setting was often not associated with documented water exposure, which has implications for empiric antimicrobial therapy. Severe disease and death were uncommon.

Lower Rates of Staphylococcus aureus Bloodstream Infection in Patients on Hemodialysis Receiving Trimethoprim-Sulfamethoxazole Melioidosis Prophylaxis.

Hemodialysis is a risk factor for Staphylococcus aureus bloodstream infection (SAB). In this single-center study, SAB rates were 56% lower during the monsoonal wet season when patients on hemodialysis receive supervised melioidosis prophylaxis with trimethoprim-sulfamethoxazole. This intervention may reduce SAB rates in high-risk patients; however, further targeted studies are required.

Reliability of automated biochemical identification of Burkholderia pseudomallei is regionally dependent.

Misidentifications of Burkholderia pseudomallei as Burkholderia cepacia by Vitek 2 have occurred. Multidimensional scaling ordination of biochemical profiles of 217 Malaysian and Australian B. pseudomallei isolates found clustering of misidentified B. pseudomallei isolates from Malaysian Borneo. Specificity of B. pseudomallei identification in Vitek 2 and potentially other automated identification systems is regionally dependent.

Hookworm in the Northern Territory: down but not out.

OBJECTIVES: To determine the prevalence and trends of human hookworm infection (HWI) in the Northern Territory over the past 10 years, and to assess the influence of the community children's deworming program (CCDP). DESIGN, PATIENTS AND SETTING: A retrospective observational analysis of consecutive microbiologically confirmed cases of HWI in patients diagnosed at NT government health care facilities and the main private laboratory servicing the NT between January 2002 and July 2012. MAIN OUTCOME MEASURES: Annual prevalence of HWI (2002-2011); age, sex, Indigenous status, residence, haemoglobin level and eosinophil count of patients with HWI; and proportion of patients within the CCDP target population (children aged 6 months to 16 years, who should receive 6-monthly albendazole). RESULTS: From 64 691 faecal samples examined during the study period, hookworm was detected in 112 patients. There was a downward trend in the annual prevalence of HWI, falling from 14.0 cases per 100 000 population (95% CI, 8.8-19.2) in 2002 to 2.2 per 100 000 population (95% CI, 0.3-4.1) in 2011. Only 16 patients (14.3%) fell within the CCDP target population. Seventy-one patients (63.4%) were living in remote communities, and 94 (84.7%) were recorded as Indigenous Australians. CONCLUSIONS: The prevalence of HWI in the NT reduced over the 10-2013 period. HWI predominantly occurs in individuals outside the CCDP target population. Our data support continuation of the CCDP in conjunction with improvements in housing, health hardware and health promotion. Continued use of albendazole in individuals beyond the CCDP may facilitate the eventual eradication of HWI from the NT.

Spectrum of human Pasteurella species infections in tropical Australia.

BACKGROUND: Acquired zoonotic infections with Pasteurella bacterial species have a wide clinical spectrum of disease from invasive infections to localised bite-wound infections. METHODS: This study reviewed the spectrum of the demographic, clinical, temporal, and microbiological trends of laboratory confirmed Pasteurella species infections presenting to a single-centre tropical tertiary hospital over a twenty-year period. RESULTS: 195 episodes from 190 patients were included. 51.3% patients were female, and 20.5% Aboriginal or Torres Strait Islander peoples. Crude incidence of Pasteurella spp. infections increased from 1.5 per 100,000 population in 2000, to 11.4 per 100,000 population in 2021. There were 22 (11.3%) bloodstream infections, 22 (11.3%) invasive, 34 (17.4%) deep local, 98 (50.2%) superficial infections, and 19 (9.7%) other or unknown. Adults over 65 years of age accounted for the majority of bacteraemias (63.7%). More severe infections, including bacteraemia, invasive and deep local infections, were more common in lower limb infections and in those with underlying comorbidities. Animal contact with cats was more common in bloodstream infections (36.4%), but dog bites more common in invasive, deep local and superficial infections. 30-day all-cause mortality was low at 1.0%. Pasteurella multocida was most commonly identified (61.1%), but P. canis, P. dagmatis, and other Pasteurella infections were also noted. 67.7% of specimens were polymicrobial, with other significant organisms being Staphylococcus aureus, Streptococcus pyogenes, Group G Streptococcus and Pseudomonas aeruginosa. CONCLUSION: Pasteurella species remain clinically important pathogens, with the ability to cause severe and invasive infections with associated morbidity. Presentations to hospital are becoming more common, and the polymicrobial nature of bites wounds has implications for empiric antibiotic guidelines.

Epidemiology, management and outcomes of Cryptococcus gattii infections: A 22-year cohort.

BACKGROUND: Cryptococcus gattii is a globally endemic pathogen causing disease in apparently immune-competent hosts. We describe a 22-year cohort study from Australia's Northern Territory to evaluate trends in epidemiology and management, and outcome predictors. METHODS: A retrospective cohort study of all C. gattii infections at the northern Australian referral hospital 1996-2018 was conducted. Cases were defined as confirmed (culture-positive) or probable. Demographic, clinical and outcome data were extracted from medical records. RESULTS: 45 individuals with C. gattii infection were included: 44 Aboriginal Australians; 35 with confirmed infection; none HIV positive out of 38 tested. Multifocal disease (pulmonary and central nervous system) occurred in 20/45 (44%). Nine people (20%) died within 12 months of diagnosis, five attributed directly to C. gattii. Significant residual disability was evident in 4/36 (11%) survivors. Predictors of mortality included: treatment before the year 2002 (4/11 versus 1/34); interruption to induction therapy (2/8 versus 3/37) and end-stage kidney disease (2/5 versus 3/40). Prolonged antifungal therapy was the standard approach in this cohort, with median treatment duration being 425 days (IQR 166-715). Ten individuals had adjunctive lung resection surgery for large pulmonary cryptococcomas (median diameter 6cm [range 2.2-10cm], versus 2.8cm [1.2-9cm] in those managed non-operatively). One died post-operatively, and 7 had thoracic surgical complications, but ultimately 9/10 (90%) treated surgically were cured compared with 10/15 (67%) who did not have lung surgery. Four patients were diagnosed with immune reconstitution inflammatory syndrome which was associated with age <40 years, brain cryptococcomas, high cerebrospinal fluid pressure, and serum cryptococcal antigen titre >1:512. CONCLUSION: C. gattii infection remains a challenging condition but treatment outcomes have significantly improved over 2 decades, with eradication of infection the norm. Adjunctive surgery for the management of bulky pulmonary C. gattii infection appears to increase the likelihood of durable cure and likely reduces the required duration of antifungal therapy.

Melioidosis in Timor-Leste: First Case Description and Phylogenetic Analysis.

Burkholderia pseudomallei, the causative agent of melioidosis, has not yet been reported in Timor-Leste, a sovereign state northwest of Australia. In the context of improved access to diagnostic resources and expanding clinical networks in the Australasian region, we report the first 3 cases of culture-confirmed melioidosis in Timor-Leste. These cases describe a broad range of typical presentations, including sepsis, pneumonia, multifocal abscesses, and cutaneous infection. Phylogenetic analysis revealed that the Timor-Leste isolates belong to the Australasian clade of B. pseudomallei, rather than the Asian clade, consistent with the phylogeographic separation across the Wallace Line. This study underscores an urgent need to increase awareness of this pathogen in Timor-Leste and establish diagnostic laboratories with improved culture capacity in regional hospitals. Clinical suspicion should prompt appropriate sampling and communication with laboratory staff to target diagnostic testing. Local antimicrobial guidelines have recently been revised to include recommendations for empiric treatment of severe sepsis.

Impact of results of a rapid Staphylococcus aureus diagnostic test on prescribing of antibiotics for patients with clustered gram-positive cocci in blood cultures.

In tropical northern Australia, approximately 20% of Staphylococcus aureus bacteremia is caused by methicillin-resistant Staphylococcus aureus (MRSA). We prospectively evaluated the impact on clinician antibiotic prescribing of the results obtained from performing the GeneXpert MRSA/SA test on 151 positive blood cultures with clustered gram-positive cocci. The GeneXpert result led to earlier appropriate prescription of vancomycin for 54% of patients with MRSA; 25% of patients avoided vancomycin, and 16% of patients had all antibiotics ceased.

Is Streptococcus pyogenes resistant or susceptible to trimethoprim-sulfamethoxazole?

Streptococcus pyogenes is commonly believed to be resistant to trimethoprim-sulfamethoxazole (SXT), resulting in reservations about using SXT for skin and soft tissue infections (SSTI) where S. pyogenes is involved. S. pyogenes' in vitro susceptibility to SXT depends on the medium's thymidine content. Thymidine allows S. pyogenes to bypass the sulfur-mediated inhibition of folate metabolism and, historically, has resulted in apparently reduced susceptibility of S. pyogenes to sulfur antibacterials. The low thymidine concentration in Mueller-Hinton agar (MHA) is now regulated. We explored S. pyogenes susceptibility to SXT on various media. Using two sets of 100 clinical S. pyogenes isolates, we tested for susceptibility using SXT Etests on MHA containing defibrinated horse blood and 20 mg/liter ß-NAD (MHF), MHA with sheep blood (MHS), MHA alone, MHA with horse blood (MHBA), and MHA with lysed horse blood (MHLHBA). European Committee on Antibacterial Susceptibility Testing (EUCAST) breakpoints defined susceptibility (MIC, ≤ 1 mg/liter) and resistance (MIC, >2 mg/liter). In study 1, 99% of S. pyogenes isolates were susceptible to SXT on MHA, MHBA, and MHLHBA, with geometric mean MICs of 0.04, 0.04, and 0.05 mg/liter, respectively. In study 2, all 100 S. pyogenes isolates were susceptible to SXT on MHF, MHS, MHA, and MHLHBA with geometric mean MICs of 0.07, 0.16, 0.07, and 0.09 mg/liter, respectively. This study confirms the in vitro susceptibility of S. pyogenes to SXT, providing support for the use of SXT for SSTIs. A clinical trial using SXT for impetigo is ongoing.

Melioidosis at Royal Darwin Hospital in the big 2009-2010 wet season: comparison with the preceding 20 years.

OBJECTIVE: To compare the unprecedented 91 cases of melioidosis in the Top End of the Northern Territory of Australia from 1 October 2009 to 30 September 2010 with the 540 cases in the preceding 20 years and postulate reasons for this year of very high melioidosis incidence. DESIGN, SETTING AND PARTICIPANTS: Review of prospectively collected data on all patients with culture-confirmed melioidosis at Royal Darwin Hospital, the Top End's tertiary referral centre, since 1 October 1989. MAIN OUTCOME MEASURES: Population-based annual incidence of melioidosis; differences in epidemiology, clinical presentations and outcomes for 2009-2010 compared with the preceding 20 years. RESULTS: In 2009-2010, the estimated population-based incidence of melioidosis was 50.2 cases per 100 000 in the Top End population overall, and 102.4 cases per 100 000 in the Top End Indigenous population. The proportion of patients acquiring melioidosis in the Darwin urban area increased from 49% in 1989-2009 to 65% in 2009-2010 (OR, 1.96; 95% CI, 1.20-3.19). Among the 49 Indigenous Australian patients with melioidosis in 2009-2010, 63% acquired the infection in Darwin, compared with 35% of Indigenous patients in the previous 20 years (OR, 3.17; 95% CI, 1.62-6.24). CONCLUSIONS: In 2009-2010, the Top End had the highest annual incidence of melioidosis documented from anywhere to date. The prominent increase in cases in Darwin was associated with above average rainfall in Darwin during December 2009 to February 2010. The increase in the proportion of Indigenous Australians who acquired melioidosis in Darwin may reflect movement of some Indigenous people into Darwin from remote communities.