Immunization as a tool to combat antimicrobial resistance.

Vaccines and immunization programs can play a key role in addressing the growing challenge of antimicrobial resistance (AMR). Amongst the high priority vaccines in development are several AMR pathogens, including: Clostridium difficile, Staphylococcus aureus, Streptococcus pneumoniae, Mycobacterium tuberculosis and Neisseria gonorrhoeae. There is evidence that vaccination can reduce the prevalence of AMR microbes, as demonstrated by both pneumococcal and Haemophilus influenza b vaccines. Research continues on many vaccine-preventable diseases, many of these AMR pathogens, including HIV and universal influenza vaccines. Not only do vaccines prevent infections, they can also prevent secondary opportunistic infections from AMR microbes-for example, bacterial pneumonia following influenza infections. The reduced need to treat these opportunistic infections would also mitigate the advance of AMR microbes in our communities. However, vaccines are not a panacea. One downside to the use of vaccines to address AMR is vaccine hesitancy, which undermines efforts to achieve herd immunity, but this is being increasingly addressed by public health education campaigns.

Enhanced surveillance for measles in low-incidence territories of the Russian Federation: defining a rate for suspected case investigation.

The rate of case investigation for measles-like illness (MLI) is an important indicator for the quality of measles surveillance in countries targeting measles elimination. However, a benchmark rate is still being discussed. We assessed different rates of investigation in 11 territories of the Russian Federation with low reported measles incidence during the previous 4-7 years. Each territory maintained their existing surveillance activities and also undertook additional surveillance activities for MLI over a 3-year period. The annual routine rate of investigation varied from 0·06 to 1·8/100,000 population; the overall rate of investigation, including enhanced surveillance, varied from 1·4 to 7·2/100,000. Forty-nine (30·8%) of 159 measles cases detected were identified through enhanced surveillance. Based on the results of this study, the Russian Federation concluded that a rate of routine investigation of 2/100,000 provided the best balance between available resources and sensitivity for detection of measles cases.

Preventing congenital rubella infection in the European Region of WHO: 2010 target.

The World Health Organisation (WHO) Regional Office for Europe has recently published a strategic plan and surveillance guidelines for measles and congenital rubella infection. The strategy prioritizes measles control activities but encourages the introduction of rubella vaccine when measles vaccine coverage has reached >90 %; although, many western European countries with suboptimal measles vaccine coverage are already using the combined measles, mumps and rubella (MMR) vaccine. Women in these countries may have an especially high risk of having an infant with congenital rubella syndrome. WHO is seeking to improve the surveillance for rubella and congenital rubella syndrome as a means to obtain better information on the burden of these diseases and engage policy decision makers in the need to support the WHO European Region's strategies for rubella.

Preventing congenital rubella infection in the European Region of WHO: 2010 target.

The World Health Organisation (WHO) Regional Office for Europe has recently published a strategic plan and surveillance guidelines for measles and congenital rubella infection. The strategy prioritises measles control activities but encourages the introduction of rubella vaccine when measles vaccine coverage has reached >90 %; although, many western European countries with suboptimal measles vaccine coverage are already using the combined measles, mumps and rubella (MMR) vaccine. Women in these countries may have an especially high risk of having an infant with congenital rubella syndrome. WHO is seeking to improve the surveillance for rubella and congenital rubella syndrome as a means to obtain better information on the burden of these diseases and engage policy decision makers in the need to support the WHO European Region's strategies for rubella.

Pertussis is a frequent cause of prolonged cough illness in adults and adolescents.

Although pertussis is increasingly recognized as a cause of prolonged cough illness in adolescents and adults, its prevalence is not well established. We evaluated pertussis infection in 442 adolescents and adults > or = 12 years old (mean age, 41.3 years) who had a cough-related illness of 7--56 days' duration. For 4 patients (0.9%), results of nasopharyngeal culture or PCR were positive for Bordetella pertussis; for 10 patients (2.3%), either results of culture or PCR were positive or pertussis antibody titers increased 4-fold. Eighty-eight patients (19.9%) had either laboratory-confirmed pertussis or laboratory evidence of pertussis. These patients had significantly longer duration of cough than did patients without laboratory evidence of pertussis (56 days vs. 46 days), and more of them had vomiting with cough (45.5% vs. 28.5%, respectively). Pertussis is a common cause of prolonged cough illness in adolescents and adults and is frequently associated with other symptoms of whooping cough.

Invasive disease due to group B streptococcal infection in adults: results from a Canadian, population-based, active laboratory surveillance study--1996. Sentinel Health Unit Surveillance System Site Coordinators.

In 1996, a population-based surveillance program for invasive adult group B streptococcal (GBS) diseases in Canada was undertaken, to define the epidemiologic and microbiologic characteristics of the disease. Nine public health units across Canada, representing 9.6% of the population, participated in the program. In total, 106 culture-positive cases of invasive adult GBS disease were reported, which represented an incidence rate 4.6 per 100,000 adults (41/100, 000 for pregnant and 4.1/100,000 for nonpregnant adults). Sixty-two (58.5%) of the 106 cases occurred in females, and, of these, 15 (14. 2%) were associated with pregnancy. Serotype V was the most common, accounting for 31% of the 90 GBS isolates typed (26.7% of nonpregnant and 4.4% of pregnant cases). This was followed by serotypes III (19%), Ia (17%), Ib (10%), II (9%), and VII (1%). Thirteen percent were nontypeable. All isolates were susceptible to penicillin, ampicillin, and vancomycin. Resistance to erythromycin and clindamycin was 6.7% and 4.4%, respectively.

Pneumococcal immunization and public health: the Canadian experience.

Pneumococcal vaccine has been poorly used in Canada, despite strong recommendations for its use by the Canadian National Advisory Committee on Immunization. In a recent survey of health officials, however, seven of the 12 Canadian provinces and territories were found to either have a programme for all persons > 65 years of age or were planning to implement one within the next year. Factors that have contributed to this increased interest include: better data on disease incidence and preventable illness from population-based surveillance; data on emerging resistance of Streptococcus pneumoniae in Canada to penicillin and other antimicrobials; implementation of vaccine programmes for the elderly by public health officials in Ontario, Nova Scotia and British Columbia; completion of a cost-benefit study of pneumococcal vaccine for Canada; and increased attention to pneumococcal vaccination at national immunization meetings and in the medical literature. Increased availability of vaccine and competitive pricing are also making programmes for the elderly more feasible and affordable. A national meeting entitled 'Preventing Pneumococcal Disease: A Canadian Consensus Conference' was held in February 1998 to further build on this growing interest.

Risk factors and course of illness among children with invasive penicillin-resistant Streptococcus pneumoniae. The Streptococcus pneumoniae Working Group.

OBJECTIVES: To assess differences in risk factors, clinical presentation, and course of illness between children infected with penicillin-sensitive and drug-resistant Streptococcus pneumoniae (DRSP). DESIGN: A retrospective cohort study conducted in Uruguay and Argentina using information from a hospital-based surveillance system. Hospitalized children 5 years of age and younger who had S pneumoniae isolated from a normally sterile site between June 1993 and October 1996 were eligible. Hospital records were linked with surveillance data. Both stratified univariate analysis and logistic regression was completed. RESULTS: Of the 380 children eligible for the study, 274 records (72%) were available for review. Ninety-nine children (36%) had DRSP; 46 showed intermediate susceptibility (minimum inhibitory concentration, 0.12-1.0 microg/mL) and 53 showed high-level resistance (minimum inhibitory concentration >/=2.0 microg/mL). Children with meningitis were less likely to have DRSP than those with other forms of invasive disease (relative risk = 0. 5; 95% confidence interval [CI], 0.2-0.9). Risk factors associated with DRSP were use of penicillin or ampicillin in the 3 months before illness (odds ratio = 2.9; 95% CI, 1.5-5.7) and possession of private medical coverage (odds ratio = 2.4; 95% CI, 1.2-5.0). Response to therapy, including response to penicillin or ampicillin among children with nonmeningeal invasive disease, course of illness, and clinical outcome did not differ significantly between children infected with penicillin-susceptible or penicillin-resistant isolates. CONCLUSION: In this study, previous use of penicillin or ampicillin and private medical coverage were associated with having DRSP. Children with nonmeningeal invasive disease responded equally well to penicillin regardless of the penicillin susceptibility of their pneumococcal isolate.

A Canadian multicentre case-control study of sporadic Escherichia coli 0157:H7 infection.

OBJECTIVE: To evaluate further risk factors for Escherichia coli 0157:H7 infection including consumer preferences related to the consumption of ground beef and the role of person-to-person transmission of this infection. PATIENTS AND METHODS: A case-control study of sporadic E coli 0157:H7 infection was undertaken in five Canadian cites from June to December 1991. One hundred cases of E coli 0157:H7 infection were age- and sex-matched to 200 neighbourhood controls. Cases and controls were interviewed face-to-face to obtain information on potential risk factors for infection and health outcomes. Daycare providers of case and control children were interviewed regarding risk factors for infection at the institutional level. Contacts of cases and controls who reported diarrhea in the seven days before the case onset date were also interviewed about their symptoms and risk factors. RESULTS: All cases had diarrhea during the course of their illness and 90 (90%) reported bloody diarrhea. Four (4%) were reported to have developed hemolytic uremic syndrome; however, there were no fatalities. Sixty-one (61%) of patients were hospitalized. Two variables were associated with infection in the final conditional logistic regression model: eating pink hamburger patties (odds ratio = 12.4, P=0.0001, population attributable fraction =40.2%) and contact with a nonhousehold member suffering from diarrhea (odds ratio = 7.0, P=0.0054, population attributable fraction = 10.3%) in the seven days before illness. Forty per cent of cases and controls who indicated that they prefer well done hamburgers said they would eat a 'pink' hamburger if served to them rather than ask that the hamburger be cooked longer. CONCLUSIONS: Health care workers should remain vigilant in their efforts to educate the public as to the risks associated with the consumption of ground beef that is inadequately cooked, and the importance of personal hygiene in the prevention of enteric illness.

Salmonella typhimurium DT104: a virulent and drug-resistant pathogen.

Salmonella typhimurium phage type (PT) or definitive type (DT) 104 is a virulent pathogen for humans and animals, particularly cattle. It has been isolated increasingly from humans and animals in the United Kingdom and several other European countries and, more recently, in the United States and Canada. Humans may acquire the infection from foods of animal origin contaminated with the infective organism. Farm families are particularly at risk of acquiring the infection by contact with infected animals or by drinking unpasteurized milk. The symptoms in cattle are watery to bloody diarrhea, a drop in milk production, pyrexia, anorexia, dehydration and depression. Infection may result in septicemic salmonellosis and, upon necropsy, a fibrinonecrotic enterocolitis may be observed. The infection occurs more commonly in the calving season than at other times. Feedlot cattle and pigs may also be affected. Prolonged carriage and shedding of the pathogen may occur. Symptoms in humans consist of diarrhea, fever, headache, nausea, abdominal pain, vomiting, and, less frequently, blood in the stool. Salmonella typhimurium DT104 strains are commonly resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline.

Invasive Streptococcus pneumoniae infection in Latin American children: results of the Pan American Health Organization Surveillance Study.

Protein-polysaccharide conjugate vaccines against Streptococcus pneumoniae promise to be an effective public health intervention for children, especially in an era of increasing antimicrobial resistance. To characterize the distribution of capsular types in Latin America, surveillance for invasive pneumococcal infection in children < or = 5 years of age was done in six countries between February 1993 and April 1996. Fifty percent of 1,649 sterile-site isolates were from children with pneumonia, and 52% were isolated from blood. The 15 most common of the capsular types prevalent throughout the region accounted for 87.7% of all isolates. Overall, 24.9% of isolates had diminished susceptibility to penicillin: 16.7% had intermediate resistance and 8.3% had high-level resistance. Three customized vaccine formulas containing 7, 12, and 15 capsular types were found to have regional coverages of 72%, 85%, and 88%, respectively. This study emphasizes the need for local surveillance for invasive pneumococcal disease prior to the development and evaluation of protein-polysaccharide conjugate vaccines for children.

Risk factors for infection with verocytotoxigenic Escherichia coli in cattle on Ontario dairy farms.

Risk factors for prevalent infection with verocytotoxigenic Escherichia coli (VTEC) were studied in a random sample of 886 cows and 592 calves under 3 months of age on 80 randomly selected dairy farms in southern Ontario. Fecal-culture supernatants from each animal were screened for verocytotoxicity using a Vero cell assay (VCA) and for verocytotoxin (VT) genes by a polymerase chain reaction (PCR) procedure. Up to 20 F. colt isolates from positive samples were tested for VT production using VCA and PCR. VTEC isolates were serotyped. Farm managers were interviewed using a standardized questionnaire to obtain information on farm- and individual animal-level management practices and characteristics. There was a significant (P < 0.001) positive association between age of calves and their VTEC infection status, and calves were significantly more likely to be infected than cows. The proportion of calves infected on the farm was positively associated with both the use of regular pails for feeding calves (as opposed to nipple bottles or nipple pails) and bringing new animals into the herd in the previous year.

Invasive Streptococcus pneumoniae infections: serotype distribution and antimicrobial resistance in Canada, 1992-1995.

OBJECTIVE: To report current information about invasive pneumococcal infections, capsular types and antimicrobial resistance in Canada. DESIGN: Retrospective analysis. SETTING: Canada. PATIENTS: A total of 976 patients from whom Streptococcus pneumoniae was isolated from blood or cerebrospinal fluid between Jan. 1, 1992, and Dec. 31, 1995. OUTCOME MEASURES: Capsular type and antimicrobial susceptibility. RESULTS: Twenty types accounted for 90.8% of the isolates from patients over 5 years of age; all but type 15A are covered by the currently available 23-valent vaccine. Nine types accounted for 92% of the isolates recovered from children 5 years and less. Reduced susceptibility to penicillin was found in 7.8% of the collection and was associated with types 6B, 9V and 19A. Full resistance to penicillin was observed most frequently during 1995 and was associated with type 9V. Rates of reduced susceptibility over one 12-month period were 19.5% for trimethoprim-sulfamethoxazole and 4.5% or less for each of cefotaxime, ceftriaxone, chloramphenicol, erythromycin, ofloxacin and tetracycline. CONCLUSIONS: Over 90% of invasive pneumococcal infections are covered by the currently available vaccines (for people over 2 years of age) and the pneumococcal protein-polysaccharide conjugate vaccines under development for young children. The high frequency of antimicrobial resistance observed requires more complete investigation and confirmation; however, taken from a global perspective, it supports the need to develop better control strategies, including greater use of new and existing vaccines.

Persistence of Escherichia coli O157:H7 in dairy cattle and the dairy farm environment.

The persistence of Escherichia coli O157:H7 in cattle and the farm environment was investigated on eight Ontario dairy farms positive for E. coli O157:H7 in a longitudinal study commenced one year previously. Faecal samples from cows, calves, humans, cats, rodents, wild birds, a composite fly sample and numerous composite and individual environmental samples were cultured and tested for verotoxin-producing E. coli (VTEC). VTEC isolates were serotyped and E. coli O157:H7 isolates were phage typed. E. coli O157:H7 phage type 34 was isolated from one calf on each of two farms. The same phage type had been isolated on one of these farms 12 months earlier. Most E. coli O157:H7-positive animals and farms became culture-negative within 2 and 3 months, respectively. E. coli O157:H7 was not isolated from any environmental samples, although evidence of VTEC was found in composite samples from calf feeders (19.1%), calf barn surfaces (18%), cow feeders (14.9%), flies (12.5%), cow barn surfaces (11.3%), and individual milk filters (12.5%). VTEC belonging to 21 non-O157 serotypes were isolated from 24 cows (8.2%), 21 calves (18.3%), 2 cow feeder samples (3.0%), and 1 calf feeder sample (4.8%). Shedding of E. coli O157:H7 by infected dairy cattle appears to be transient and persistence of E. coli O157:H7 was not demonstrated from the farm environment sites tested.