Serratia sp. bacteremia in Canberra, Australia: a population-based study over 10 years.

The purpose of this paper was to determine the population incidence and clinical features of Serratia sp. bacteremia in Canberra, Australia. Demographic and clinical data were collected prospectively for episodes of Serratia sp. bacteremia over a 10-year period, and was confined to Canberra residents using residential postal codes. Thirty-eight episodes of Serratia sp. bacteremia occurred, with a yearly incidence of 1.03 per 100,000 population. The majority of episodes occurred in males (68%). The respiratory tract was the most common focus of infection (21%). Twenty-nine percent of episodes were community-associated. A further 18% of episodes had their onset in the community but were healthcare-associated. The 7-day and 6-month mortality rates were 5 and 37%, respectively. Antibiotic resistance to gentamicin (3%) and ciprofloxacin (0%) was low. Serratia sp. bacteremia is more common than generally appreciated, with a large proportion (47%) of episodes having their onset in the community.

Invasive pneumococcal disease in the Australian Capital Territory and Queanbeyan region: do high infant rates reflect more disease or better detection?

OBJECTIVE: To describe the epidemiology of invasive pneumococcal disease in the Australian Capital Territory (ACT) and Queanbeyan region prior to the introduction of conjugate pneumococcal vaccines. METHODOLOGY: Residents with sterile site isolates of Streptococcus pneumoniae from 1998 to 2000 were identified from a prospective bacteraemia surveillance project involving all ACT public hospitals, supplemented by retrospective laboratory-based detection of other sterile site isolates. RESULTS: Incidence of invasive pneumococcal disease was 15.2 cases per 105 per year, and 193.4 per 105 per year in infants under 2 years. Primary bacteraemia was significantly more common in infants and young children than in older subjects. Reduced penicillin susceptibility was observed in 9.6% of isolates, and no high-level penicillin resistance was observed. CONCLUSIONS: Infants in the ACT and Queanbeyan have a higher invasive pneumococcal disease incidence than similar populations worldwide. Better detection is the most likely explanation. This population would be ideal for studies of the 'real life' effectiveness of infant conjugate vaccination.

Antibiotic resistance in Streptococcus pneumoniae.

Resistance to penicillin and other antibiotics in Streptococcus pneumoniae has emerged in Australia and around the world in the past decade, and appears to be worsening (e.g., rates of penicillin resistance in Australia rose from 1% in 1989 to 25% in 1997). In Australia, the only oral antibiotic able to treat respiratory infections caused by some multiresistant strains is high-dose amoxycillin. If these strains increase in prevalence, then treatment failures for relatively minor infections (e.g., otitis media) are likely to become common, resulting in repeat antibiotic courses or hospitalisation for parenteral therapy. Therapy for meningitis caused by penicillin-sensitive pneumococcal strains remains high-dose benzylpenicillin, but empirical treatment while awaiting culture and sensitivity results is problematic; neither penicillin nor third-generation cephalosporins cover all strains. Therefore, many authorities recommend vancomycin, usually combined with a third-generation cephalosporin, for treating presumptive or proven pneumococcal meningitis pending penicillin-susceptibility results. As almost all readily available oral antibiotics in Australia select for resistant strains of pneumococci, multiresistant strains will increase in prevalence unless unnecessary antibiotic use and prescription volumes are reduced substantially in the next few years.

Identification of genes associated with copper tolerance in an adhesion-defective mutant of Aeromonas veronii biovar sobria.

TnphoA mutagenesis was used to identify adhesins of Aeromonas veronii biovar sobria 3767, a strain isolated from a diarrhoeal stool specimen. Six mutants, from a library of 154, exhibited significantly reduced levels of adhesion to HEp-2 cells. Primers to the terminal regions of TnphoA were used for inverse PCR and the product from one mutant was cloned into pBluescript and partial sequence data obtained. Scanning GenBank and EMBL data bases revealed DNA sequence similarity to the copA gene of Pseudomonas syringae pv. tomato which confers resistance to copper and other heavy metals. The transposon was located within the copA gene and the mutant exhibited a reduced tolerance to copper. Primer walking, using the inverse PCR product as a template, revealed three open reading frames (ORFs) copA, B and C in A. veronii biovar sobria 3767. The predicted amino acid sequences of ORFs A and B had significant homology (55 and 34% respectively) to the copA and B proteins of P. syringae. No amino acid or DNA sequence homology existed between ORF C of strain 3767 and any other gene in the data bases scanned. Further analysis of the nucleotide sequence failed to reveal the presence of typical copper regulatory genes within the vicinity of the Aeromonas sequence. The association between copper tolerance and adhesion in A. veronii biovar sobria requires further study.

Intravascular catheter-associated infections.

Serious infections associated with intravascular catheters are common. The available data suggests there are likely to be more than 500 000 cases of catheter-associated bloodstream infections occurring annually in Western Europe and the USA. These may be associated with as many as 100 000 deaths. The pathophysiology of this common condition is still not fully elucidated. With catheters that are in place for short periods (a few days), microbial migration down the outer surface of the device to the intravascular tip predominates. For catheters that are in place for longer periods, migration occurs more often via the internal lumen. After being in place for more than 8 days, nearly all central vein catheters will have microorganisms embedded in a biofilm within the catheter lumen. In some catheters, microorganisms will proliferate to sufficient numbers for systemic sepsis to result. The occurrence and rate of this proliferation is dependent on microbial virulence factors, host factors, and characteristics of the catheter. Diagnosis of intravascular device-associated sepsis remains problematic because the pathophysiology of the condition changes with time and because standard culture techniques rarely detect organisms embedded in biofilms. The semiquantitative roll method on blood agar remains in common use because of its simplicity. However, the method only samples the external surface of the catheter. For catheters that have been in place for extended periods of time, methods that better sample the internal lumen, such as sonication and quantitative broth methods, should be developed and used.

Variations in antibiotic resistance profile in Enterobacteriaceae isolated from wild Australian mammals.

We carried out a retrospective analysis of 946 strains of Enterobacteriaceae isolated from wild Australian mammals between 1993 and 1997. The prevalence of resistance to fixed concentrations of 32 antimicrobial agents was determined, and the respective roles that taxonomic family of the host, state of origin and bacterial species play in defining prevalence and range of resistance were investigated. Our results demonstrated a low but widespread prevalence of antimicrobial resistance in wild isolates. Only amikacin, ciprofloxacin, meropenem and gentamicin inhibited growth in all 946 samples. There was extensive variation in the combination of antibiotics to which isolates were resistant, and multiple antibiotic resistance was common. Geographical location and host group significantly influenced the antibiotic resistance profile of an isolate, whereas bacterial species influenced both the resistance profile of an isolate and the number of antibiotics it was resistant to. The role of these factors in determining observed antibiotic resistance profiles suggests that any study measuring resistance in wild isolates should include the broadest possible range of bacterial species, host species and sampling locations. As such, this study provides an important new baseline for future measurements of antibiotic resistance in the Australian environment.

Vancomycin-resistant enterococci and use of avoparcin in animal feed: is there a link?

Australia is unique among Western countries in allowing animal use of this vancomycin-like antibiotic.

Rapidly emerging antimicrobial resistances in Streptococcus pneumoniae in Australia. Pneumococcal Study Group.

OBJECTIVE: To examine the prevalence of resistance in Streptococcus pneumoniae to key antimicrobials in Australia during 1997. DESIGN: Prospective, Australia-wide, laboratory-based survey. SETTING: 11 microbiology laboratories from seven Australian States and Territories (five private laboratories and six public hospital laboratories) between March and November 1997. STRAINS: Up to 100 consecutive, clinically significant strains of S. pneumoniae isolated by each laboratory. MAIN OUTCOME MEASURES: Susceptibility to penicillin, amoxycillin-clavulanate, cefaclor, ceftriaxone, erythromycin, tetracycline, and sulfamethoxazole-trimethoprim (cotrimoxazole), measured by a gradient diffusion, minimum inhibitory concentration technique. RESULTS: Of 1020 strains, 16.8% had intermediate susceptibility to penicillin and 8.6% were resistant. Rates of resistance to other drugs were: amoxycillin-clavulanate, 3.1%; cefaclor, 21.4%; ceftriaxone, 3.1%; erythromycin, 15.6%; tetracycline, 15.7%; and cotrimoxazole, 33.4%. Non-invasive isolates harboured more resistances than invasive isolates, and resistance was more prevalent in isolates from children under two years. Multiple resistance was also common, with 21.2% of strains resistant to two or more classes of drug, and 9.3% of non-invasive and 1.7% of invasive isolates resistant to four classes. There were no obvious differences in resistance rates between private and public hospital laboratories. CONCLUSIONS: Rates of antimicrobial resistance are rising rapidly in S. pneumoniae in Australia. Recommendations for empiric treatment of invasive and respiratory infection need to take account of these changes.

Antibiotic resistance in Streptococcus pneumoniae isolated from children.

OBJECTIVE: To determine the level of antibiotic resistance in pneumoniae (S. pneumoniae) isolated from nasal swabs of healthy children. METHOD: Cross-sectional community survey. SETTING: Survey was undertaken in general practice settings in Canberra during March and April 1998. SUBJECTS: Four hundred and sixty-one children under 3 years of age enrolled in general practice trial of clinical practice guidelines for antibiotic use. OUTCOME MEASURES: Resistance to penicillin, erythromycin, co-trimoxazole, tetracycline, chloramphenicol and cefotaxime among the isolates of S. pneumoniae. RESULTS: A total of 461 nasal swabs were collected and S. pneumoniae was isolated from 171 (37.1%). Penicillin resistance was found in 12.3% of these isolates, with high level resistance in 0.6%. Resistance rates were higher for cotrimoxazole (44.4%) and erythromycin (18.1%) than for penicillin. Multidrug resistance was found in 19% of these isolates. There was a significant association between the attendance at a day care centre and carriage of pneumococcus (53% vs 32%, odds ratio (OR) 2.4, 95% confidence interval (CI) 1.5-3.7, P < 0.001). Children who attended day care centers and had received antibiotics during the 4 months prior to swab collection were three times more likely to carry an antibiotic-resistant isolate than children who had neither attended a day care centre nor received antibiotics (68% vs 40%, OR 3.1, 95% CI 1.2-8.4, P = 0.02). CONCLUSION: The level of antibiotic resistance in pneumococci from healthy children was of concern. Carriage of pneumococcus was significantly higher in children who attended a day care centre. Resistance was significantly correlated with antibiotic use in combination with day-care attendance. These findings warrant more judicious use of antibiotics in children.

Antibiotic management of pneumococcal infections in an era of increased resistance.

Pneumococci are a leading cause of bacterial meningitis and bacteraemia, as well as pneumonia, otitis media and sinusitis in childhood. These organisms recently have shown a dramatic increase in antibiotic resistance. Penicillin-resistant pneumococci are of special concern as they are often resistant to other unrelated antibiotics. This is of particular significance to Aboriginal children who have among the highest rates of pneumococcal infection in the world. Laboratories should now test all invasive pneumococcal isolates for penicillin and third generation cephalosporin resistance. Local treatment guidelines are required for pneumococcal infections, especially for meningitis, taking into account the prevalence of resistant strains within the community. At present, penicillin and amoxycillin remain the drugs of choice for pneumococcal infections, with the exception of meningitis where initial empirical therapy must be with a third generation cephalosporin. Judicious antibiotic use, which avoids over-prescribing and unnecessary use of broad-spectrum agents, improved living standards in underprivileged communities and introduction of an effective conjugate vaccine, able to reduce the rates of pneumococcal infection and hopefully colonization, may limit the spread of resistant strains.

New guidelines for management and prevention of meningococcal disease in Australia. Meningococcal Disease Working Party of the National Health and Medical Research Council.

The incidence of invasive meningococcal disease in Australia has increased over the past decade, and in April 1997 the National Health and Medical Research Council published guidelines for management of patients with meningococcal disease and their contacts. These guidelines emphasise the need for immediate intravenous antibiotic treatment of patients with suspected meningococcal disease, before transfer to hospital or lumbar puncture. When possible, blood for culture should be collected before antibiotic therapy, if this does not delay treatment.

Reuse in sterile sites of single-use medical devices: how common is this in Australia?

OBJECTIVE: To determine to what extent Australian hospitals reuse in sterile sites medical devices labelled "single use only"; to assess the adequacy of cleaning and sterilising procedures before reuse; and to estimate the possible incidence of cross-infection and the costs of not reusing these devices. DESIGN: A self-administered questionnaire survey. SETTING: All Australian hospitals (419) with more than 45 beds and undertaking medical and surgical procedures. METHODS: Questionnaires were sent to hospital infection control practitioners in 1994 requesting information about reuse in sterile sites of single-use medical devices, the extent of reuse, the cleaning and sterilising processes involved, and the reasons for reuse. RESULTS: Responses were received from 168 hospitals (40%). Reuse occurred in 64 (38%), and another 33 hospitals had been reusing medical devices 12 months before our survey (i.e., 97/168 hospitals [58%] were either reusing them at the time of our survey or had been doing so 12 months previously). More large (> 300 beds) metropolitan public hospitals (9/14; 64%) reported reusing than did smaller (50/143; 41%) or private hospitals (15/47; 32%). At six of the 64 hospitals where reuse occurred, the process of cleaning and/or sterilization of these devices was not satisfactory; from the information we received, both cleaning and sterilization were satisfactory in only 38 hospitals (59%). Examination of the 14 most commonly reuse devices showed that the structure of 13 of these may compromise cleaning (and therefore sterilization). The main reason given for reuse was cost saving. Assuming a 2% prevalence of transmissible infections in blood, and an infection transmission risk of 1/500, we estimate that each year in Australia there may be 40 cases of cross-infection for every one million procedures performed with reused devices (0.004%). CONCLUSIONS: Reuse of medical devices labelled "single use only" is common in Australian hospitals. Most devices appear to be unsuitable for reuse. Complete cessation of this practice of reusing single-use medical devices would stop potential cross-infection, but this would cost and estimated $2.5 million or more per case prevented

Drug-resistant Streptococcus pneumoniae: the beginning of the end for many antibiotics? Australian Group on Antimicrobial Resistance (AGAR)

OBJECTIVE: To determine the levels of antibiotic resistance in Streptococcus pneumoniae in Australia. DESIGN: Prospective, Australia-wide, laboratory-based survey. SETTING: 27 hospital and private laboratories around Australia, from January 1994 to August 1995. SUBJECTS: First 100 patients with clinically significant isolates of S. pneumoniae at each laboratory. OUTCOME MEASURES: Resistance to penicillin (determined from penicillin minimum inhibitory concentration [MIC] measured by the Etest), erythromycin, trimethoprim-sulfamethoxazole, tetracycline, chloramphenicol, cefotaxime and ceftriaxone. RESULTS: A total of 2396 isolates were tested (including 537 invasive isolates and 740 from children). Penicillin resistance was seen in 161 isolates (6.7%), including 17 with high level resistance. Penicillin resistance rates were significantly lower in invasive than in non-invasive strains (3.7% versus 7.6%; odds ratio [OR], 0.47; 95% confidence interval [CI], 0.28-0.77; P = 0.001). There was no significant difference in penicillin resistance rates between children (< 15 years) and adults (7.3% versus 6.5%; OR, 1.14; 95% CI, 0.80-1.63; P = 0.47). Resistance rates were higher for most other antibiotics than for penicillin (chloramphenicol, 6%; erythromycin, 11%; tetracycline, 15%; and trimethoprim-sulfamethoxazole, 42%). No high level resistance was seen to third generation cephalosporins, but 17 of 109 penicillin-resistant isolates tested (16%) displayed intermediate resistance to cefotaxime. Rates of antibiotic resistance varied between States, with the lowest rates in Tasmania. CONCLUSIONS: Antibiotic resistance levels in S. pneumoniae are increasing in Australia and high level penicillin resistance is being encountered for the first time (including in invasive strains). This will lead to an increasing number of therapeutic dilemmas and possible therapeutic failures, especially important in meningitis.