Simon Warwick

Control of an Outbreak of Multidrug-Resistant Acinetobacter baumannii-calcoaceticus Colonization and Infection in an Intensive Care Unit (ICU) Without Closing the ICU or Placing Patients in Isolation

OBJECTIVE To describe the control of multidrug-resistant Acinetobacter baumannii-calcoaceticus (MDRABC) colonization and infection in an intensive care unit (ICU). SETTING An 18-bed ICU in a large tertiary care teaching hospital in London. INTERVENTIONS After recognition of the outbreak, a range of infection control measures were introduced over several months that were primarily aimed at reducing environmental contamination with the outbreak strain. Strategies included use of a closed tracheal suction system for all patients receiving mechanical ventilation, use of nebulized colistin for patients with evidence of mild to moderate ventilator-associated pneumonia, improved availability of alcohol for hand decontamination, and clearer designation of responsibilities and strategies for cleaning equipment and the environment in the proximity of patients colonized or infected with MDRABC. RESULTS The outbreak lasted from June 2001 through November 2002 and involved 136 new cases of MDRABC infection or colonization. The number of newly diagnosed cases per month reached a maximum of 15 in February 2002, and the number of new cases slowly decreased over the next 9 months. CONCLUSION This outbreak was controlled by emphasizing the control of environmental reservoirs and did not require recourse to ward closure or placement of affected patients in isolation.

Use of Quantitative 16S Ribosomal DNA Detection for Diagnosis of Central Vascular Catheter-Associated Bacterial Infection

ABSTRACT Many central vascular catheters (CVCs) are removed unnecessarily because current diagnostic methods for CVC-associated infection are unreliable. A quantitative PCR assay using primers and probe targeted to bacterial 16S ribosomal DNA was used to measure the levels of bacterial DNA in blood samples drawn through the CVC in a population of patients receiving intravenous nutrition. Bacterial DNA concentrations were raised in 16 of 16 blood samples taken during episodes of probable bacterial CVC-associated infection. Bacterial DNA concentrations were raised in 4 of 29 episodes in which bacterial CVC-associated infection was unlikely. The use of this technique has the potential to substantially reduce the unnecessary removal of CVCs.

Colonization and persistence of antibiotic-resistant Enterobacteriaceae strains in infants nursed in two neonatal intensive care units in East London, United Kingdom.

ABSTRACT Stool samples were collected from infants nursed in two neonatal intensive care units (NICUs) in East London, United Kingdom. The aim of the study was to determine the incidence of and risk factors for the carriage of multiresistant Enterobacteriaceae strains (MRE; resistant to three or more classes of antibiotic) and the extent of the persistence of resistant strains following discharge. Sixty-two (50%) of 124 infants had acquired MRE by 2 weeks of postnatal age, and 69 (56%) infants had acquired MRE by discharge. The proportions of infants at 2 weeks carrying strains that were resistant to antibiotics were the following: tetracycline, 79%; amoxicillin, 78%; cephalosporins, 31%; trimethoprim, 20%; piperacillin-tazobactam, 11%; chloramphenicol, 9%; and aminoglycoside, 4%. A gestational age of less than 26 weeks was a risk factor for colonization with MRE at discharge, but not at 2 weeks. Analysis within a NICU showed that exposure of an infant to a specific antibiotic in the NICU was not a risk factor for the carriage of a strain resistant to that antibiotic. Estimates of persistence from discharge to 6 months were the following: for tetracycline, 57% (95% confidence intervals [CI], 0.35 to 0.87); chloramphenicol, 49% (95% CI, 0.20 to 0.83); trimethoprim, 45% (95% CI, 0.22 to 0.74); piperacillin-tazobactam, 42% (95% CI, 0.20 to 0.71); and augmentin, 34% (95% CI, 0.11 to 0.66). Strains resistant to cephalosporins or aminoglycosides showed lower levels of persistence. Nine of 34 infants (26.5%) with Escherichia coli and 4 (7.1%) of 56 infants with Klebsiella spp. at discharge carried strains indistinguishable by randomly amplified polymorphic DNA and antibiotic susceptibility patterns at 6 months. MRE were found at high frequency in the infants during their stay in the NICU and persisted in a proportion of infants.

Tsukamurella tyrosinosolvens Intravascular Catheter Infection Identified Using 16S Ribosomal DNA Sequencing

Cultures of blood from a hemodialysis line repeatedly yielded a gram-positive rod. The organism was identified as Tsukamurella tyrosinosolvens by 16S ribosomal DNA sequencing, and the patient was treated successfully by removal of the line.

The use of molecular techniques for bacterial detection in the analysis of gastric aspirates collected from infants on the first day of life.

UNLABELLED Prospective service evaluation of the utility of molecular methods to analyse neonatal gastric aspirate specimens in a single neonatal unit and associated maternity unit. 43 newborn infants investigated for sepsis with median gestational age of 39 weeks (range 31-41 weeks) and median birth weight 3050 grams (range 1250-4220 g). Gastric aspirates routinely collected within 12h of birth were analysed using conventional and molecular methods for bacterial detection, bacterial DNA load and sequencing to identified bacterial species. RESULTS Bacterial DNA loads varied from 0.03 to 1736 pg/microl of DNA extract (1 microl of DNA extract equivalent to 4 microl gastric aspirate). Bacteria were identified in 30/43 (70%) of samples by molecular methods and 10/43 (23.3%) of samples by culture. Cultures were only positive when the bacterial DNA exceeded 4.5 pg/microl of extract. Infants with prolonged rupture of membranes (>24h prior to delivery) had a DNA load on average 23 times higher than those without (95%CI 3.7 to 141; p=0.001). Additional bacteria detected by molecular methods included many species that are fastidious and potentially pathogenic including Leptotrichia spp., Serratia spp., Ureaplasma spp., Veillonella spp., Haemophilus influenzae and Group B Streptococcus. Due to a low rate of adverse outcomes it was not possible to correlate bacterial identifications or DNA load with infant outcome. CONCLUSIONS Molecular methods can identify bacteria from a greater proportion of gastric aspirate specimens that conventional culture. Further work is required to establish whether this information can be used to improve infant outcomes.

The dangers of dog bites

This report describes an unusual case of endocarditis caused by Capnocytophaga canimorsus as a result of dog bite. The diagnosis could be established only by molecular techniques after amplification of bacterial DNA from the infected cardiac valve. The epidemiology and management of Capnocytophaga infections is discussed, as well as the role of prophylactic antibiotics in preventing these infections after dog bites.

Vibrio harveyi sepsis in a child with cancer

A paediatric oncology patient presented with central line sepsis caused by Vibrio harveyi, a gram negative bioluminescent marine bacterium known to be pathogenic to fish and marine invertebrates, after swimming in the sea. Pediatr Blood Cancer 2008;50:891–892.

Listeriosis Due to Infection with a Catalase-Negative Strain of Listeria monocytogenes

ABSTRACT A strain of Listeria monocytogenes recovered from blood and cerebrospinal fluid had no detectable catalase activity, a characteristic used for primary identification. The sporadic occurrence of pathogenic catalase-negative strains highlights the need for a reconsideration of diagnostic criteria and questions the role of catalase in the pathogenesis of listeria infection.