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Pneumolysin is an important virulence factor of the human pathogen Streptococcus pneumoniae. Sequence analysis of the ply gene from 121 clinical isolates of S. pneumoniae uncovered a number of alleles. Twenty-two strains were chosen for further analysis, and 14 protein alleles were discovered. Five of these had been reported previously, and the remaining 9 were novel. Cell lysates were used to determine the specific hemolytic activities of the pneumolysin proteins. Six strains showed no hemolytic activity, and the remaining 16 were hemolytic, to varying degrees. We report that the nonhemolytic allele reported previously in serotype 1, sequence type (ST) 306 isolates is also present in a number of pneumococcal isolates of serotype 8 that belong to the ST53 lineage. Serotype 1 and 8 pneumococci are known to be associated with outbreaks of invasive disease. The nonhemolytic pneumolysin allele is therefore associated with the dominant clones of outbreak-associated serotypes of S. pneumoniae.

An outbreak of serious illness and death occurred in injecting drug users during 2000 in Scotland, Ireland and England. National and international collaboration was necessary for the investigation and management of this outbreak. In England and Wales active case-finding was initiated, coupled with standardised data collection and microbiological investigation of cases. Twenty-six definite or probable cases were identified in England between 1 April and 31 Aug. 2000; 17 of these occurred in the North. The overall case fatality was 50% (13/26). The principal apparent risk factor was a history of intramuscular or subcutaneous injection of heroin and the limited duration of the outbreak suggested that the problem might have been related to a particular supply of heroin. Clostridium novyi was isolated from two English cases. Taken in conjunction with contemporaneous microbiological and epidemiological results from Scottish and Irish cases, the probable aetiology for this outbreak was infection with C. novyi associated with both a particular supply of heroin and the method of preparation and injection used. A 'toolkit' was distributed in Sept. 2000 to all Consultants for Communicable Disease Control in England and Wales to assist them with the ongoing surveillance, investigation and management of this condition. Lessons learned have been used to produce guidance for the investigation and management of outbreaks of unexplained serious illness of possible infective aetiology.

Twenty-six isolates of the newly designated M90 serotype group A Streptococcus (GAS) from a large food-borne outbreak of pharyngitis in Greece and six M90 sporadic isolates from UK, were typed by pulsed-field gel electrophoresis (PFGE). Twenty-four outbreak isolates were identical and two closely related. The Greek isolates were possibly related with one UK isolate, while other sporadic isolates exhibited distinct PFGE profiles from the former isolates.

A nosocomial outbreak of infection and colonization involving six patients and caused by a strain of Staphylococcus aureus showing intermediate resistance to methicillin (MIC = 4-8 mg l-1) is described. The outbreak was associated with skin-carriage of the epidemic strain by a nurse suffering from severe eczema. The reduced susceptibility of the outbreak strain to methicillin was associated with beta-lactamase production. Elimination or inhibition of beta-lactamase activity produced a two-fold decrease in methicillin MIC. There was no evidence for the presence of either penicillin-binding protein 2a or the corresponding mec gene, which mediate resistance in fully methicillin-resistant strains.

During a 3-week period, nine babies in the neonatal unit of a large teaching hospital in Durban were infected or colonized with Klebsiella pneumoniae resistant to a range of antimicrobial agents including amikacin and cefotaxime. Resistance to cefotaxime was reduced by clavulanic acid in vitro suggesting production of extended-spectrum beta-lactamase activity. All the isolates had the same antibiotic resistance profile, belonged to the same serotype (K17), were non-typable with bacteriophages, and had identical plasmid profiles indicating that they belonged to the same strain. During a 1-day microbiological survey of the ward, the outbreak strain was isolated from the nose and hands of a doctor based in the nursery and from the hands of a nurse and the mother of an infected baby. The strain was also isolated from nine of 67 environmental samples. Investigation revealed that infection control practices which had been instituted following a previous outbreak in the nursery with multi-resistant methicillin-resistant Staphylococcus aureus (MRSA) were not being adhered to. The re-introduction and strict enforcement of these procedures under the supervision of an Infection Control Nurse resulted in the abrupt end of the outbreak.

During an 8-month period, Klebsiella pneumoniae resistant to cefotaxime and ceftazidime were isolated from 18 elderly patients in two closely-situated UK hospitals. Amongst these 18 patients, the organisms were isolated from urine samples of 17, from blood cultures of two and from a wound swab of one. The infected patients were located in nine different wards and several of the patients had been transferred between wards, within and between the two hospitals. All the bacterial isolates belonged to serotype K62, were non-typable or reacted only weakly with bacteriophage, showed similar plasmid profiles and were resistant to tetracycline and trimethoprim, thus indicating they were the same strain. Resistance to cefotaxime and ceftazidime was inhibited by clavulanic acid suggesting the involvement of extended-spectrum beta-lactamase (ESBL) enzyme activity. This was confirmed by analytical isoelectric focusing, which showed that isolates each produced two beta-lactamases with isoelectric points of 7.0(SHV-3) and 7.6 (SHV-1/2) respectively.

Erythromycin resistance amongst group A streptococci (GAS) in Great Britain is a relatively rare occurrence and outbreaks have been sporadically reported. Over an 8-month period in 1986 ten associated cases occurred in the town of Bridgewater in Somerset. Isolates were group A, type M4 and resistant to erythromycin (MIC 8 mg/l) but sensitive to lincomycin and clindamycin. Erythromycin resistance was transferable from all isolates to a group A recipient strain. No plasmid DNA could be detected in the original isolates or transconjugants.