Survey of blood cultures from five community hospitals in south-western Sydney, Australia, 1993-1994

Bloodstream Infections in a Community Hospital: A 25-Year Follow-Up

Objective:

To examine the current status of bloodstream infections (BSIs) in a community hospital as part of a 25-year longitudinal study.

Design:

Retrospective descriptive epidemiologic study.

Setting:

Community teaching hospital.

Patients:

All inpatients in 1998 with a positive blood culture who met the CDC NNIS System case definition of BSI.

Methods:

Cases were stratified by underlying illness category using case mix adjustment categories (after McCabe) and reviewed for associations among mortality, underlying illness severity, and multiple clinical and laboratory parameters.

Results:

Of 19,289 patients discharged in 1998,185 had an episode of infection documented by blood culture (96 cases per 10,000 inpatients). BSI was twice as frequent in patients 65 years and older compared with younger patients. BSIs caused or contributed to the deaths of 22 patients for an overall case-fatality rate of 11.9% compared with 20.7% in 1982 (P = .02). Striking decreases were noted for in-hospital patient mortality in 1998 for BSIs with ultimately and rapidly fatal underlying illnesses (P = .02 and P < .10, respectively). Primary bacteremia decreased compared with 1982. Antibiotic use was vigorous, but resistance was modest in both nosocomial and community-acquired organisms and had changed little from 1982 and 1987.

Conclusions:

Compared with previous studies, case-fatality rates in patients with BSI were substantially lower in rapidly fatal and ultimately fatal underlying illness categories. Antibiotic use was extensive but prompt and appropriate. Microorganism resistance to antibiotics changed little from the 1980s.

Bacteraemias in tropical Australia: changing trends over a 10-year period

Bacteraemia is an important cause of morbidity and mortality worldwide. This is the largest reported study of bacteraemias in Australia. The presence of organisms endemic to the tropical region and the changing trends described have significant implications for empirical antibiotic therapy. This retrospective study examined 8976 blood cultures from Townsville Hospital, a regional Australian hospital located in the tropics over a 10-year period. The rate of bacteraemic episodes during the study period was 10.12 per 1000 admissions. Intravenous devices (18.7%), immunosuppressive therapy (16.1%), and urinary tract infections (16.1%) were important sources for bacteraemia. The most common organisms were Staphylococcus aureus (20.9%) and Escherichia. coli (15.6%). A significant reduction was observed in S. aureus susceptibility to clindamycin (P < 0.05) and in E. coli susceptibility to gentamicin. Organisms isolated that were of relevance to the tropics of Australia included Burkholderia pseudomallei, Group A streptococcus, and Brucella suis.

Influence of referral bias on the clinical characteristics of patients with Gram-negative bloodstream infection

Referral bias can influence the results of studies performed at tertiary-care centres. In this study, we evaluated demographic and microbiological factors that influenced referral of patients with Gram-negative bloodstream infection (BSI). We identified 2919 and 846 unique patients with Gram-negative BSI in a referral cohort of patients treated at Mayo Clinic Hospitals and a population-based cohort of Olmsted County, Minnesota, residents between 1 January 1998 and 31 December 2007, respectively. Multivariable logistic regression analysis was used to determine factors associated with referral. Elderly patients aged ≥80 years with Gram-negative BSI were less likely to be referred than younger patients [odds ratio (OR) 0·43, 95% confidence intervals (CI) 0·30-0·62] as were females (OR 0·63, 95% CI 0·53-0·74). After adjusting for age and gender, bloodstream isolates of Escherichia coli (OR 0·50, 95% CI 0·43-0·58) and Proteus mirabilis (OR 0·49, 95% CI 0·30-0·82) were underrepresented in the referral cohort; and Pseudomonas aeruginosa (OR 2·26, 95% CI 1·70-3·06), Enterobacter cloacae (OR 2·31, 95% CI 1·53-3·66), Serratia marcescens (OR 2·34, 95% CI 1·33-4·52) and Stenotrophomonas maltophilia (OR 17·94, 95% CI 3·98-314·43) were overrepresented in the referral cohort. We demonstrated that demographic and microbiological characteristics of patients with Gram-negative BSI had an influence on referral patterns. These factors should be considered when interpreting results of investigations performed at tertiary-care centres.

Two nations: racial disparities in bloodstream infections recorded at Alice Springs Hospital, central Australia, 2001-2005

OBJECTIVE

To compare bloodstream infection (BSI) rates, pathogens and mortality among Indigenous and non-Indigenous adults in central Australia.

DESIGN, PARTICIPANTS AND SETTING

Retrospective study of adult patients (aged > or = 15 years) admitted to Alice Springs Hospital (ASH) between 1 January 2001 and 31 December 2005. Patients were followed up until 30 June 2008.

MAIN OUTCOME MEASURES

Admission-based and population-based BSI rates and mortality rates for Indigenous and non-Indigenous adults.

RESULTS

During the study period, there were 824 BSI episodes (Indigenous, 753; non-Indigenous, 71). The admission-based BSI rate for Indigenous patients was 26.5 (95% CI, 26.4-26.6) per 1000 adult admissions, compared with 5.2 (95% CI, 5.1-5.2) per 1000 adult admissions for non-Indigenous patients (infection rate ratio [IRR], 5.13 [95% CI, 5.10-5.18]). The population-based BSI rate was 1354.7 (95% CI, 1256.3-1460.8) per 100 000 persons per year among Indigenous patients and 69.9 (95% CI, 55.1-88.6) per 100 000 persons per year among non-Indigenous patients (IRR, 19.4 [95% CI, 15.1-24.9]). These differences were not explained by higher comorbidity levels among Indigenous patients. Human T-cell lymphotropic virus type 1 and Strongyloides stercoralis infected 43% and 35%, respectively, of Indigenous patients tested. The risk of death during the follow-up period was 32.1% for Indigenous and 13.4% for non-Indigenous patients (hazard ratio [HR], 2.69 [95% CI, 1.38-5.25]; P = 0.004). Mortality rates were higher among Indigenous patients who had more than a single BSI (HR, 1.86 [95% CI, 1.32-2.62]; P < 0.001). The mean age at death was 48.5 years (SD, 16.2 years) for Indigenous patients and 75.1 years (SD, 18.7 years) for non-Indigenous patients (P < 0.001).

CONCLUSION

Indigenous adults living in central Australia experience BSI rates that are among the highest reported in the world. These are associated with a high risk of death, and are a likely consequence of the poor socioeconomic circumstances of Indigenous people.

Genetic relatedness and virulence gene profiles of Escherichia coli strains isolated from septicaemic and uroseptic patients

We investigated the relationship between clonality and virulence factors (VFs) of a collection of Escherichia coli strains isolated from septicaemic and uroseptic patients with respect to their origin of translocation. Forty septicaemic and 30 uroseptic strains of E. coli were tested for their phylogenetic groupings, genetic relatedness using randomly amplified polymorphic DNA (RAPD), biochemical fingerprinting method (biochemical phenotypes [BPTs]), adherence to HT-29 cells and the presence of 56 E. coli VF genes. Strains belonging to phylogenetic groups B2 and D constituted 93% of all strains. Fifty-four (77%) strains belonged to two major BPT/RAPD clusters (A and B), with cluster A carrying significantly (P = 0.0099) more uroseptic strains. The degree of adhesion to HT-29 cells of uroseptic strains was significantly (P = 0.0012) greater than that of septicaemic strains. Of the 56 VF genes tested, pap genes was the only group that were found significantly (P < 0.0001) more often among uroseptic isolates. Phylogenetic group B2 contained a significantly higher number of strains carrying pap genes than those in group D. We conclude that uroseptic E. coli are clonally different from septicaemic strains, carry more pap genes and predominantly adhere more to the HT-29 cell model of the gut.

Antimicrobial resistance trends of Escherichia coli bloodstream isolates: a population-based study, 1998-2007

BACKGROUND

There have been contradictory results regarding temporal changes in the antimicrobial resistance of Escherichia coli from tertiary care centres. Therefore, we performed a population-based investigation to examine in vitro antimicrobial resistance trends of E. coli bloodstream isolates.

METHODS

In this retrospective population-based incidence study, we identified 461 unique patients with first episodes of E. coli bloodstream infection (BSI) from 1 January 1998 to 31 December 2007 through microbiology records at the two laboratories in Olmsted County, Minnesota. Logistic regression was used to examine temporal changes in antimicrobial resistance and Poisson regression for changes in incidence rates.

RESULTS

The median age of patients with E. coli BSI was 69 years; 306 (66.4%) were female. The age-adjusted incidence rate of E. coli BSI per 100 000 person-years was 48.0 (95% CI: 42.5-53.4) in females and 34.0 (95% CI: 28.6-39.6) in males. The urinary tract was the most common primary source of infection (79.8%). During the study period, resistance rates of E. coli bloodstream isolates increased from 32% to 53% for ampicillin, from 23% to 45% for ampicillin/sulbactam, from 9% to 28% for trimethoprim/sulfamethoxazole and from 0% to 12% for ciprofloxacin. Resistance rates to carbapenems, cephalosporins and piperacillin/tazobactam remained low and stable.

CONCLUSIONS

To our knowledge, this is the first population-based study on antimicrobial resistance trends of E. coli bloodstream isolates in the USA. We demonstrated linear trends of increasing resistance among these isolates to three different classes of antimicrobial over the past decade.

Escherichia coli bacteraemia in Canberra: incidence and clinical features

OBJECTIVE

To determine the population incidence and clinical features of Escherichia coli bacteraemia in Canberra, Australia.

DESIGN, SETTING AND PARTICIPANTS

Canberra (including the nearby local government areas of Queanbeyan and Yarrowlumla) has a geographically isolated population of about 366 000 people. Its six hospitals also provide tertiary medical services for the surrounding region. Confining our analysis (by residential postcodes) to Canberra residents only, we used microbiology laboratory records and population statistics to calculate the population incidence of E. coli bacteraemia from January 2000 to December 2004. Clinical data were also collected prospectively on episodes occurring within three of the hospitals.

MAIN OUTCOME MEASURES

Population incidence of E. coli bacteraemia; place of acquisition of infection; focus of infection within body; recovery, new morbidity or death at 7 days.

RESULTS

During the 5-year period, 515 episodes of E. coli bacteraemia occurred in Canberra residents, an incidence of 28 per 100 000 population per year. The highest rate was in men aged > or = 80 years (463 per 100 000). Overall, E. coli bacteraemia occurred in equal numbers in males and females, but incidence was higher in males aged < 1 year and > or = 60 years. Most episodes occurred in people aged > or = 60 years (316/511 [62%]) and most were community-associated (347/511 [68%]). Half the infections (257/511) had a genitourinary focus and 28% (141/511) a gastrointestinal focus. The 7-day case-fatality rate was 5%. Prostate biopsies and urinary catheters were notable preventable foci of health care-associated bacteraemia. Resistance of isolates to gentamicin (2.1%), ciprofloxacin (1.8%) and cefotaxime (0.4%) was low.

CONCLUSIONS

E. coli is the most common cause of bacteraemia in Canberra, and incidence increases with age. Most cases have a community onset, but many episodes are related to health care procedures. Ongoing surveillance is important for identifying risk factors that may be modified to reduce disease.

Infections caused by Scedosporium spp

Scedosporium spp. are increasingly recognized as causes of resistant life-threatening infections in immunocompromised patients. Scedosporium spp. also cause a wide spectrum of conditions, including mycetoma, saprobic involvement and colonization of the airways, sinopulmonary infections, extrapulmonary localized infections, and disseminated infections. Invasive scedosporium infections are also associated with central nervous infection following near-drowning accidents. The most common sites of infection are the lungs, sinuses, bones, joints, eyes, and brain. Scedosporium apiospermum and Scedosporium prolificans are the two principal medically important species of this genus. Pseudallescheria boydii, the teleomorph of S. apiospermum, is recognized by the presence of cleistothecia. Recent advances in molecular taxonomy have advanced the understanding of the genus Scedosporium and have demonstrated a wider range of species than heretofore recognized. Studies of the pathogenesis of and immune response to Scedosporium spp. underscore the importance of innate host defenses in protection against these organisms. Microbiological diagnosis of Scedosporium spp. currently depends upon culture and morphological characterization. Molecular tools for clinical microbiological detection of Scedosporium spp. are currently investigational. Infections caused by S. apiospermum and P. boydii in patients and animals may respond to antifungal triazoles. By comparison, infections caused by S. prolificans seldom respond to medical therapy alone. Surgery and reversal of immunosuppression may be the only effective therapeutic options for infections caused by S. prolificans.

Mesenteric adenitis and portal vein thrombosis due to Fusobacterium nucleatum

We report the first description of portal and mesenteric vein thrombosis associated with suppurative mesenteric adenitis in a 71-year-old woman. The bacterium detected in mesenteric lymph nodes was Fusobacterium nucleatum, an anaerobic Gram-negative bacillus. Our patient had a clinical syndrome of pharyngitis and fever preceding portal vein thrombosis. Abdominal symptoms improved with antibiotics and anticoagulant therapy. This location of F. nucleatum in mesenteric lymph nodes provides an interesting insight into the occurrence of septic thrombosis in the portal vein following pharyngo-tonsillar infection.

Epidemiology of community-acquired and nosocomial bloodstream infections in tropical Australia: a 12-month prospective study

OBJECTIVES

To define the relative incidence of organisms causing blood stream infections in a tropical setting with a very low prevalence of human immunodeficiency virus infection (<1%).

METHODS

A 12-month prospective study of blood stream infections in 2000 at Royal Darwin Hospital in the tropical north of Australia.

RESULTS

Significant isolates were grown from 257 sets of blood cultures. Staphylococcus aureus was the most common isolate overall (28%); 26% of these were methicillin-resistant (MRSA). Escherichia coli was the most common cause of community-acquired bacteraemia. Burkholderia pseudomallei caused 32% of community acquired, bacteraemic pneumonia; 6% of bacteraemias overall. Vancomycin-resistant enterococci were not isolated. Crude mortality rates (13% overall; 9% attributable mortality) were lower than in most comparable studies.

CONCLUSIONS

The major difference between these findings and surveys performed elsewhere is the presence of B. pseudomallei as a significant cause of bacteraemic community-acquired pneumonia. Our results demonstrate the effects of local environmental and patient characteristics on the range of organisms causing blood stream infections, and emphasize the important role of local microbiology laboratories in guiding empiric antibiotic therapy.

Cephalosporin resistant urinary tract infections in young children

OBJECTIVE

To describe the antibiotic resistance pattern of bacteria causing urinary tract infection (UTI) in a cohort of Australian children under 6 years of age.

METHODS

Data were collected over a 12-month period from children under 6 years of age with a provisional diagnosis of UTI made in the Emergency Department of Sunshine Hospital, Victoria.

RESULTS

During the study period 100 culture-proven UTI were identified in 97 children. Three children had two episodes. Out of the 100 episodes, 39% were male, 56% were under 12 months of age at presentation and 61% were managed as outpatients. Clinical features were non-specific in the majority of cases. Hydronephrosis and vesicoureteric reflux was detected in 5.5% and 28.6%, respectively, of children with their first investigated UTI. A single bacterial isolate was cultured from 97 urines and two from three samples. Escherichia coli (n = 90) and Proteus mirabilis (n = 5) were the most common isolates. In vitro resistance to ampicillin/amoxycillin was found in 52% of isolates, to trimethoprim in 14% and to cephalothin/cephalexin in 24%. This resistance rate to first generation cephalosporins is the highest reported to date in adult or paediatric UTI in Australia.

CONCLUSIONS

Ampicillin/amoxycillin or cephalothin/cephalexin may not be the optimal choice of antibiotic for the empiric treatment of UTI in this and possibly other paediatric populations.

Retrospective review of febrile neutropenia in the Royal Darwin Hospital, 1994-99

BACKGROUND

Febrile neutropenia is a life-threatening complication of cytotoxic chemotherapy. Empirical antibiotic treatment should be based on predominant pathogens and epidemiological characteristics of the treated community. The aim of the present study was to review cases of febrile neutropenia at the Royal Darwin Hospital (RDH) in order to assess the appropriateness of empirical antibiotic therapy.

METHODS

A retrospective review of cases of febrile neutropenia secondary to malignancy or chemotherapy occurring at the RDH over the period 1994-99. In order to compare infections in this group with those in the wider hospital community, all positive blood cultures in the medical and intensive care units were reviewed for the same time period.

RESULTS

Thirty-six episodes of febrile neutropenia were reviewed. Staphylococcus aureus (predominantly methicillin resistant), Pseudomonas aeruginosa and Escherichia coli were the most common organisms identified. Nine patients died of their infection, four with methicillin-resistant S. aureus bacteraemia. S. aureus, E. coli, Streptococcus pneumoniae and Burkholderia pseudomallei (melioid) were the most frequently isolated organisms from blood cultures taken in the medical and intensive care units.

CONCLUSIONS

Gram-positive organisms are the predominant pathogens in febrile neutropenic episodes at the RDH. Standard empirical therapy with an extended-spectrum penicillin and an aminoglycoside remains appropriate, with the addition of vancomycin when clinical status fails to improve. When practising in the Top End, particular consideration should be given to skin integrity and scabies and testing for Strongyloides in Aboriginal patients.