Increasing incidence of candidaemia: long-term epidemiological trends, Queensland, Australia, 1999-2008

Given variability in the epidemiology of candidaemia and a relative paucity of contemporary longitudinal data, a passive laboratory-based surveillance study was performed to assess the epidemiology of candidaemia in all public healthcare facilities in Queensland, Australia over the period 1999-2008. Demographic and microbiological data on all candidaemia episodes, together with appropriate denominators (admissions and patient-days), were collected from laboratory and administrative information systems. From 1999 to 2008, 1137 episodes occurred (overall incidence-density: 0.45 per 10 000 patient-days) with a 3.5-fold increase in density (P<0.0001 for trend). Candidaemia episodes originating in traditional high-risk areas either decreased (haemato-oncology and paediatric wards) or remained stable (intensive care units). Episodes on adult medical/surgical wards increased significantly over time, accounting for 60% of the total by 2008. The relative proportion caused by Candida albicans decreased and Candida parapsilosis increased (both P<0.01). The proportion of fluconazole-resistant isolates did not change. The increasing occurrence of candidaemia outside traditional high-risk areas and the emergence of C. parapsilosis present new challenges for preventive and early intervention strategies.

Comparison of contamination rates of catheter-drawn and peripheral blood cultures

The aim of this study was to assess the sensitivity and specificity of catheter-drawn and peripheral blood cultures. Paired blood culture samples collected over a 44-month period from a 280 bed Brisbane metropolitan hospital were analysed, using standard clinical and microbiological criteria, to determine whether blood culture isolates represented true bacteraemias or contamination. Catheter-collected cultures had a specificity of 85% compared with 97% for peripheral cultures. In only two instances (0.2%) was the diagnosis of clinically significant bacteraemia made on the basis of catheter culture alone. This study concluded that catheter-collected samples are not a good test for true bacteraemia, and that peripheral cultures are more reliable when the results of the paired cultures are discordant.

Clinical significance of quantitative blood cultures in newborn infants

AIM

To evaluate quantitative blood culture as a secondary test on a positive blood culture for the diagnosis of sepsis in newborn infants.

METHOD

A 15-month prospective study of colony forming units (CFU) on positive blood cultures from newborn infants clinically suspected of having bacterial sepsis. Growth of bacteria in peripheral blood cultures was quantified using the isolater 1.5 microbial tube lysis direct plating culture system. Colony forming units were evaluated against a clinical assessment of infection.

RESULTS

Of 137 positive blood cultures, 71 (51.8%) were taken from neonates with clinically defined infection and 66 (48.2%) were from non-infected infants. The clinical and biographical data in these two groups were similar. Coagulase negative staphylococci were the most commonly isolated organisms in each group (60.6% vs 93.9%). Eight deaths from sepsis occurred in the clinically infected group. Eighty-five per cent of sepsis was late onset. Although a CFU count > or = 30/mL predicted sepsis (sensitivity 83%, specificity 60%, positive predictive value 69%, negative predictive value 76%), a CFU count < 30/mL did not rule out serious sepsis. The higher the CFU count the greater the likelihood of sepsis.

CONCLUSION

Quantitative blood culture was not shown to be a sensitive secondary test on a positive blood culture to distinguish clinical sepsis from culture contamination. Although a positive threshold of > or = 30 CFU/mL proved to be optimal, improvement in test performance would be expected with a lower incidence of culture contamination.

Varicella-zoster virus infection in Australia

OBJECTIVE

To determine the epidemiology of varicella-zoster virus (VZV) infection in Australia using currently available data sources.

DESIGN

Analysis of national death data (23 years), congenital and neonatal cases (one year) and attendances at sentinel general practices (two years); hospital admissions in NSW and SA (six years); serological studies in 1995 involving antenatal clinics in Sydney and Brisbane and child-care centre staff and refugees in Sydney; and case-ascertainment in 1995 in South Western Sydney among public hospital staff, child-care centre staff and the community.

RESULTS

In Australia, there have been an average of 3.5 deaths from chickenpox (mostly children) and 11 from herpes zoster (mostly older people) each year since 1980. The crude death rate for chickenpox has declined (p > 0.05). In 1995, there were 14 cases of neonatal and two of congenital varicella. Average annual admission rates for NSW and SA showed 1,200 hospital bed-days used for chickenpox, more than 20% with complications, and more than 7,300 bed days for zoster; annually more than 880 in-patient admissions were complicated by VZV. Most people encounter the virus in their first 15 years, but some remain susceptible into their 20s; 25% of cases and 37% of hospital admissions for chickenpox occur in people > or = 15 years of age.

CONCLUSION

VZV infection involves people of all ages. It causes substantial morbidity and mortality, particularly at the extremes of life. The death rate from chickenpox but not zoster has fallen since the introduction of acyclovir in the 1980s. Surveillance of VZV infection must be given priority once vaccines become available, to monitor changes in morbidity and mortality.

Failure of the urinary group B streptococcal antigen test as a screen for neonatal sepsis

The accuracy of the urinary group B streptococcal antigen latex agglutination (LA) test for screening infants at risk of group B streptococcal (GBS) sepsis in the first 24 hours of life was prospectively studied in 236 infants for six months. Infection with GBS was defined by a positive blood culture while colonisation was defined by GBS cultured from any other site. The combination of infection and colonisation was used as the gold standard for the LA test. Although the LA test had a sensitivity of 90%, the specificity was only 70%, the positive predictive value 12% and the false positive rate 30%. The overall accuracy was only 71%. The LA test was unable to predict GBS sepsis in infants at risk of the disease. The false positive rate was unacceptably high and could not be potentially accounted for in 11 infants. However, a negative test was useful in excluding GBS disease.

Isolation of Kingella kingae from a corneal ulcer

Kingella kingae was isolated from a corneal ulcer in an 11-month-old male. This organism has been previously reported from normally sterile sites, including sites of endophthalmitis, but this is the first time isolation from the cornea has been reported.

Late-onset neonatal sepsis due to multiply-resistant coagulase-negative staphylococci

A cluster of septic episodes that were caused by coagulase-negative staphylococci occurred in eight patients, over a six-month period from August 1, 1984 to January 31, 1985, in a Brisbane neonatal intensive-care unit where sepsis which was due to these organisms previously was uncommon. The organisms were universally-resistant to tobramycin (the aminoglycoside agent that was used at that time) and were variably-resistant to gentamicin, flucloxacillin and cephalothin. All organisms were sensitive to netilmicin, vancomycin, fusidic acid and rifampicin. The affected infants were all of 32 weeks' or less gestation and most of them weighed less than 1500 g at birth. All neonates had been ventilated artificially and had had long intravascular lines. Two infants had ventriculoperitoneal shunts that had been infected with coagulase-negative staphylococci--a potentially-important problem that has not been noted in premature infants in previous reports. Our experience demonstrates that it is important to consider the patterns of resistance to aminoglycoside as well as to beta-lactam antibiotic agents for the empirical therapy of septic episodes and for neurosurgical prophylaxis in nurseries where coagulase-negative staphylococci are emerging as common nosocomial pathogens.

Yersinia enterocolitica. Isolation from faeces of adults and children in Queensland

Over a 22-month period, all 5075 faecal specimens received by the microbiology laboratory of the Mater Misericordiae Public Hospital, Brisbane, were screened for the presence of Yersinia enterocolitica by culturing on cefsulodinirgasan-novobiocin agar medium. Y. enterocolitica was isolated from 37 patients (0.7% of all specimens). Ten patients were 10 years of age or older, and presented predominantly with pain in the abdomen; of these, five underwent an appendicectomy. Mesenteric adenitis was diagnosed histologically in three patients and Y. enterocolitica was isolated from a lymph-node biopsy specimen in one of these. The other 27 patients were under 5 years of age, and presented predominantly with diarrhoea of 24 hours' to six weeks' duration. In seven cases, another recognized faecal pathogen was also isolated. The isolation rate of Y. enterocolitica was one-quarter that of Salmonella and seven times that of Shigella.