Source Of Epidemics Research Articles

Acquisition and spread of Acinetobacter baumannii and Stenotrophomonas maltophilia in intensive care patients

Acinetobacter baumannii and Stenotrophomonas maltophilia are increasingly important pathogens, especially in the intensive care units (ICUs). This study was designed to investigate the clonality, the mode of transmission and the patients' risk profile for acquisition of A. baumannii and S. maltophilia at the ICU of an Italian Hospital. Patterns of A. baumannii and S. maltophilia acquisition in the ICU during the period of the survey were carriage, colonization and infection. Characterization of A. baumannii was performed by ARDRA and genotyping of both pathogens by PFGE. Our study provided evidence for the occurrence of an outbreak sustained by the two organisms in study involving 27.3% of patients enrolled into the surveillance. The spread of a unique A. baumannii epidemic clone was demonstrated. A major clone of S. maltophilia was responsible for the epidemic spread of S. maltophilia (55.5% of isolates), thus confirming A. baumannii cross-transmission and showing--among few published reports--the clonal spread of S. maltophilia. Outliers analysis suggested colonized patients as the probable epidemic sources. Mechanical ventilation was confirmed as risk factor for infection (OR 8.4; 95%C.I.: 2.6-27.5). A multimodal intervention program was introduced, followed in later months with a drastic restriction of infection and colonization due to A. baumannii and S. maltophilia and subsequently with the successful control of the outbreak. Active surveillance of infection and colonization by high-risk clones, together with implementation of control strategies, including strict hand hygiene, proved to be effective to reduce the epidemic spread of both alert pathogens in our ICU.

Thysanoptera larvae living on chickweed (Stellaria mediaLinnaeus) under continental climatic conditions

By the sampling on chickweed ( Stellaria media ) carried out from autumn till the end of spring, the occurrence of the larvae of 12 Thysanoptera species has been established under climatic conditions in Hungary. Only the larvae of T. atratus and T. tabaci were present in this period in relatively high number. Since chickweed is frequently infested by Tomato spotted wilt virus (TSWV) the continuous presence of the larvae of T. tabaci in the whole period is a notable circumstance. This relationship is one of the significant ways of the survival of tomato spotted wilt virus which might be a source of new epidemics.

Optimal control of SARS epidemics based on cybernetics

This paper proposes a concept of the optimization of control measures for SARS epidemics spread, which is based on the subsystem of the compartmental model. The subsystem includes only two variables, exposed class E(t) and infectious class I(t) in free block of a community, but they are the main source of SARS epidemics spread. We proved mathematically that a maximum quarantine/isolation measures for them would reduce SARS epidemics to minimum extent in minimum time according to Pontryagin's minimum principle. Finally, the numerical simulations are given, and the results are satisfied.

Occurrence of the Ascochyta blight pathogen,Ascochyta lentis, on lentil seed in Bolivia

Ascochyta lentis was isolated from necrotic lesions on lentil seed purchased in commercial markets throughout Bolivia in 2000. Incidence of seed infection ranged from 1% to 34% and the fungi isolated were able to reinfect lentil foliage in artificial inoculations. Disease spread from seed to seedling in the field was confirmed by planting infected seed in a field previously free of the disease and observing Ascochyta blight on the foliage. In addition, disease spread between plants initiated from infected seedlots to those initiated from clean seedlots and from infected plants back to seed was also detected. These observations indicate that A. lentis infection of lentil seed is common in Bolivia and may represent an important inoculum source for Ascochyta blight epidemics in commercial lentil plantings.

Retrospective Analysis of Multidrug-ResistantAcinetobacter baumanniiStrains Isolated During a 4-Year Period in a University Hospital

To describe the epidemiology of Acinetobacter baumannii infection during 2000-2003 and to determine whether the multidrug-resistant strains were already present in our Toulouse hospital before the 2003 French national outbreak. Descriptive molecular and clinical epidemiologic study of A. baumannii isolates using a combination of antibiotyping and pulsed-field gel electrophoresis (PFGE). A 1,000-bed university hospital in Toulouse, France. All clinical samples that had tested positive for A. baumannii between January 1, 2000, and December 31, 2003, were collected. Multidrug-resistant isolates of A. baumannii were then submitted to PFGE, and clinical characteristics of the source patients were noted. A total of 1,277 A. baumannii samples were identified, 791 of which had not been previously identified; 148 were positive for multidrug-resistant strains. These strains were more likely to have been isolated in the intensive care unit (ICU) than were susceptible strains (P<.001; relative hazard, 3.77). The positive clinical samples were of various types (eg, nonprotected respiratory samples [43%] and blood [5%]), but no difference in type of source was seen between resistant and susceptible strains. A simultaneous analysis of pulsotypes and antibiotypes proved that the outbreak in the ICU in 2003 could be linked to an initially endemic clone that had been isolated in 2001. Furthermore, a second clone responsible for an extended-spectrum beta -lactamase phenotype was sporadically present in our institution. Although the strains isolated in the burn unit were also genetically related one to another, the specific responsible clone only appeared in 2003. Several multidrug-resistant clones can coexist endemically for several years and can be detected during an outbreak by close survey of epidemic sources.

Potential of fungal antagonists for biocontrol of Fusarium spp. in wheat and maize through competition in crop debris

Pathogenic Fusarium spp. cause head blight in wheat or ear rot in maize leading to yield losses and also a reduction in quality due to mycotoxin contamination of the grain. Infected crop residues are the main inoculum source for epidemics. Saprophytic fungi, obtained from cereal tissues or necrotic tissues of other crops, were screened for their ability to colonise wheat straw and maize stalks and to suppress sporulation of pathogenic Fusarium spp. Results of bio-assays conducted under controlled conditions were variable among Fusarium spp. and host substrates for most antagonists tested, such as yeasts, Trichoderma spp. and non-pathogenic Fusarium spp. Isolates of Clonostachys rosea consistently suppressed sporulation of F. culmorum and F. graminearum on wheat straw, and of F. culmorum, F. graminearum, F. proliferatum and F. verticillioides on maize stalks. Isolates of C. rosea, C. cladosporioides and F. equiseti were applied to pieces of maize stalks or flowering ears in preliminary experiments conducted under field conditions. The colonisation of stalk pieces by pathogenic Fusarium spp. was assessed after 9 months. Colonisation of stalk pieces by pathogenic Fusarium spp. was significantly reduced at several sampling dates. However, results obtained with the antagonists were not consistent for all sampling dates and between experiments.

An outbreak of food-borne group A Streptococcus (GAS) tonsillopharyngitis among residents of a dormitory

Epidemics of food-borne pharyngitis due to group A Streptococcus are rarely reported. Here we present an outbreak of food-borne tonsillopharyngitis in female dormitories in the Islamic Republic of Iran. Throat swabs and cultures were performed on a number of patients, and of specimens from the nasopharynx and hands of staff who were involved in food processing. We planned a case-control study for assessing the source of epidemics. 11 out of 17 throat swabs of students were positive for Streptococcus group A and also 2 throat samples from asymptomatic cooks were positive. A DNA fingerprinting study showed that Streptococcus group A strains of 11 students and 1 cook had the same T agglutination pattern and M protein factor (M3/T13). It is suggested that group A streptococci as well as group C and G streptococci can cause epidemic food-borne pharyngitis. Regular health surveillance of food handlers and food preparation processes are important for prevention of such outbreaks.

Expression profiles of effector proteins SopB, SopD1, SopE1, and AvrA differ with systemic, enteric, and epidemic strains of Salmonella enterica

The presence and expression of sopB, sopD1, sopE1, and avrA genes encoding virulence associated effector proteins were studied comparatively in 405 Salmonella enterica strains. They belong to different serovars and clonal types (genotypes, phage types) and originated from different clinical (systemic infection, focal enteritis, enterocolitis) and epidemic sources (epidemics, sporadic cases). The sopB and sopD1 determinants were commonly prevalent, but sopE1 and avrA genes only in 55% and 80%, respectively. A correlation of this pattern of absence and presence of the respective genes to the epidemic and clinical origin could not be detected. In contrast, the expression of the respective genes appeared differently: SopB and SopE1 proteins are well produced, but SopD1 and AvrA proteins only rarely under the applied standard culture conditions. However, using a range of different environmental signals (temperature, pH, cations, etc.) some of the S. enterica nonproducer strains (e. g., S. Agona, S. Bovismorbificans, S. Virchow, etc.) begin to produce AvrA and SopD1. They turned now into an expression profile which was found typically for the epidemic strains of S. Typhimurium and S. Enteritidis. Also S. enterica strains from systemic infections could be characterized by their strong SopB and SopE1 expression while SopD1 and AvrA proteins were missing. Although it is premature to outline generally a correlation of these expression profiles and the clinical and epidemiological potency of Salmonellae, the reported results allow a first understanding how a fine tuning of their virulence will take place.

Keeping Pace with the Elusive Bordetella pertussis

At a time when global eradication of polio is anticipated and eradication of measles is feasible, disease caused by Bordetella pertussis infection persists. Although immunization has had a profound effect in reducing disease burden, pertussis remains an endemic disease in adolescents and adults. The persistent circulation of B. pertussis in these older age groups provides a source for epidemics in susceptible infants and young children.

Clinical applications of new cerebrospinal fluid analytic techniques for the diagnosis and treatment of central nervous system infections.

Advances in molecular biology and immunology provide new, highly sensitive and specific techniques that can be applied to analysis of cerebrospinal fluid to enhance the diagnosis and treatment of central nervous system (CNS) infections. In addition to improved accuracy and speed of diagnosis, these modalities may offer improved means of monitoring treatment efficacy, establishing prognosis, detecting organism resistance, and tracking epidemic sources. This brief review discusses a number of recent papers applying these methods, in order to illustrate their value and significance for clinical neurologic practice. Some of these applications are commonly available, whereas others are likely to enter the physician's armamentarium in the near future. As they do, they can be expected to improve the treatment of CNS infections.

Molecular analysis of Vibrio cholerae O1, O139, non-O1, and non-O139 strains: clonal relationships between clinical and environmental isolates.

A total of 26 strains of Vibrio cholerae, including members of the O1, O139, and non-O1, non-O139 serogroups from both clinical and environmental sources, were examined for the presence of genes encoding cholera toxin (ctxA), zonula occludens toxin (zot), accessory cholera enterotoxin (ace), hemolysin (hlyA), NAG-specific heat-stable toxin (st), toxin-coregulated pilus (tcpA), and outer membrane protein (ompU), for genomic organization, and for the presence of the regulatory protein genes tcpI and toxR in order to determine relationships between epidemic serotypes and sources of isolation. While 22 of the 26 strains were hemolytic on 5% sheep blood nutrient agar, all strains were PCR positive for hlyA, the hemolysin gene. When multiplex PCR was used, all serogroup O1 and O139 strains were positive for tcpA, ompU, and tcpI. All O1 and O139 strains except one O1 strain and one O139 strain were positive for the ctxA, zot, and ace genes. Also, O1 strain VO3 was negative for the zot gene. All of the non-O1, non-O139 strains were negative for the ctxA, zot, ace, tcpA, and tcpI genes, and all of the non-O1, non-O139 strains except strain VO26 were negative for ompU. All of the strains except non-O1, non-O139 strain VO22 were PCR positive for the gene encoding the central regulatory protein, toxR. All V. cholerae strains were negative for the NAG-specific st gene. Of the nine non-ctx-producing strains of V. cholerae, only one, non-O1, non-O139 strain VO24, caused fluid accumulation in the rabbit ileal loop assay. The other eight strains, including an O1 strain, an O139 strain, and six non-O1, non-O139 strains, regardless of the source of isolation, caused fluid accumulation after two to five serial passages through the rabbit gut. Culture filtrates of all non-cholera-toxigenic strains grown in AKI media also caused fluid accumulation, suggesting that a new toxin was produced in AKI medium by these strains. Studies of clonality performed by using enterobacterial repetitive intergenic consensus sequence PCR, Box element PCR, amplified fragment length polymorphism (AFLP), and pulsed-field gel electrophoresis (PFGE) collectively indicated that the V. cholerae O1 and O139 strains had a clonal origin, whereas the non-O1, non-O139 strains belonged to different clones. The clinical isolates closely resembled environmental isolates in their genomic patterns. Overall, there was an excellent correlation among the results of the PCR, AFLP, and PFGE analyses, and individual strains derived from clinical and environmental sources produced similar fingerprint patterns. From the results of this study, we concluded that the non-cholera-toxin-producing strains of V. cholerae, whether of clinical or environmental origin, possess the ability to produce a new secretogenic toxin that is entirely different from the toxin produced by toxigenic V. cholerae O1 and O139 strains. We also concluded that the aquatic environment is a reservoir for V. cholerae O1, O139, non-O1, and non-O139 serogroup strains.

Malaria in the highlands of Madagascar after five years of indoor house spraying of DDT

The central region of Madagascar is a vast area of highlands (altitude 700–2000 m). Malaria transmission has re-established itself here since the last epidemic of 1985–1990 and has caused the deaths of 40 000 persons according to the Minister of Health. To combat the main malaria vector in the region, Anopheles funestus, annual programmes of indoor house spraying of DDT were carried out between December 1993 and January 1998 in most rural areas at altitude 1000–1500 m. A parasitological and serological study was then conducted in the highland schools to evaluate the impact of the programme and set up a database on the region. Using a cluster-sampling method 2 independent selections were conducted (one of 130 sites, the other of 40 sites). During the study, 13 462 schoolchildren were examined, 71% living in sprayed villages. Parasite prevalence among schoolchildren declined as altitude increases, from 11% at 700–900 m to 0 ·4 % at >1500 m. Below 1500 m, the impact of the spraying on the prevalence of the parasite was very clear (an average decrease of from 20% to 2 ·7 % below 1000 m and of from 4 ·5 % without spraying to 0 ·8 % at 1000–1500 m). Geographical analysis of the data showed that the marginal regions remained the most affected by malaria (especially outside spraying zones), and persistence of ‘pockets of transmission’ at 1000–1500 m, essentially in areas where spraying has never been used. In 9 schools, anti- Plasmodium antibodies were sought by indirect immunofluorescence on thick smears of parasitized red blood cells. The seroprevalence ranged from 22% to 63%, which suggests that the parasite is still circulating in the region. Even though our data show that vector control continues to be very successful in the Madagascan highlands, rapid reinfection could occur and must be monitored following spraying. To this end, the Minister for Health, with the support of the Italian Co-operation, has placed the region under epidemiological surveillance since 1997. An alert system for the timely detection of the sources of epidemics and the targeting of the antsivectoral campaign is also in operation. Our study suggests that this strategy should be reinforced by the spraying of DDT in the marginal zones in order to consolidate the results obtained at higher altitudes.

An epidemic of tinea corporis caused by Trichophyton tonsurans among wrestlers in Sweden.

An epidemic of tinea corporis due to Trichophyton tonsurans among wrestlers in Sweden is described. Totally 19 patients, 14 patients from Malmö and 5 from Gothenburg, were found. The suspected source of this epidemic was from a wrestlers' team from the USA visiting Sweden in April, 1993. All patients were treated orally with either griseofulvin, fluconazole or terbinafine, and all were cured. To prevent spreading, epidemiological tracing of secondary cases is important.

Hemolytic uremic syndrome

The most important advances in the understanding of the pathogenesis of the hemolytic uremic syndrome in recent years has been the identification of the most likely etiological candidate, Escherichia coli O157:H7, and the continuing elucidation of the effects of its toxin, Shiga-like toxin, on endothelial cells. It has become clear that there are two main clinical types of hemolytic uremic syndrome, namely diarrhea associated and non-diarrheal associated. Important strides have been made in defining epidemiological aspects of the disease, including sources of contaminated food and water, identification of the sources of epidemics, and person-to-person spread. Although the acute mortality rate has continued to improve, treatment remains largely supportive, and no effective definitive treatment has been found for the renal or central nervous system injury.

Recurrent Epidemics Caused by a Single Strain of Erythromycin-Resistant Staphylococcus aureus

OBJECTIVE--To compare the accuracy of clinical epidemiologic findings with results of molecular epidemiologic analysis in identifying the source of recurrent epidemics of erythromycin-resistant Staphylococcus aureus (ERSA) infections in a well-baby nursery. DESIGN--Epidemic investigations with retrospective and prospective microbiological surveillance. Staphylococcus aureus isolates were evaluated by plasmid analysis and genotyping. SETTING--A well-baby nursery in a 700-bed university teaching hospital with approximately 250 deliveries per month. PATIENTS--Newborn infants who developed ERSA infections during 1990 and 1991. INTERVENTION--Traditional infection control measures, including cohorting of infected infants and hand washing, were implemented. Personnel were cultured for nasal carriage of S aureus during both epidemics. Employees carrying ERSA were removed from the nursery and treated with mupirocin. RESULTS--In the first epidemic, 15 infants were infected with ERSA. A nursing assistant who cared for most of the infants was found to be a carrier of ERSA. She was removed from the nursery and the epidemic resolved. Fifteen months after the first epidemic ended, an epidemic that involved 11 infants began. The attending physician had a facial furuncle and was found to be a carrier of ERSA. The physician was treated and the epidemic resolved. Plasmid and genotyping showed the ERSA organisms from both epidemics were the same. The employee implicated in the first epidemic did not have the epidemic strain, but the physician who attended during both epidemics did. CONCLUSIONS--Traditional epidemic investigations may lead to false conclusions that can only be recognized with molecular epidemiologic techniques. For these techniques to be useful in the control of outbreaks, plasmid analysis and/or genotyping must be readily available.

Restriction Fragment Length Polymorphism and Virulence Pattern of the Veterinary Pathogen Escherichia coli O139: K82: H1

Escherichia coli O139:K82:H1 strains originating from outbreaks and single cases of oedema disease in pigs were characterized by their genomic restriction fragment length polymorphism (RFLP), their virulence pattern, and by the occurrence as well as the genomic distribution of the determinants for hemolysin (hly) and verotoxins (shiga-like toxins; sltI, sltII). Whereas the RFLPs revealed considerable variation among the E. coli O139:K82:H1 isolates depending the origin and epidemic source of the strains, the virulence gene slt II was found to be present in nearly all strains in a particular chromosomal region. Similar to RFLPs, the plasmid profiles are useful for epidemiological analysis.

Application of a capture enzyme immunoassay in an outbreak of waterborne giardiasis in the United Kingdom

A capture enzyme immunoassay (EIA) for the detection of Giardia lamblia antigen was used to examine 136 fecal samples collected during an outbreak of waterborne giardiasis in a city in the UK. Six cases of Giardia lamblia infection were detected that had previously not been diagnosed by microscopy. The capture EIA provides an efficient means of processing large numbers of samples for prompt and accurate assessment of an epidemic. It may also facilitate rapid tracing of epidemic sources.

Pseudomonas tolaasii on mushroom (Agaricus bisporus) crops: bactericidal effects of six disinfectants and their toxicity to mushrooms

N‐Cetylpyridinium chloride, benzalkonium chloride, Cetrimide, bronopol (2‐bromo‐2‐nitropropane‐1,3‐diol), Panacide and Chloramine T were tested as possible disinfectants for use in growing mushrooms (Agaricus bisporus) where Pseudomonas tolaasii blotch is prevalent. The most effective materials in vitro against Ps. tolaasii where the quaternary ammonium compounds and bronopol in terms of the MIC and MCC tests. In 8 min ‘clean’ and ‘dirty’ tests incorporating yeast cells bronopol did not kill the pathogen, whereas the other five disinfectants did so. If mushroom casing (peat plus limestone) was added to these short duration tests the pathogen survived all six disinfectants. When tests with added casing were extended to 20 h, bronopol was very effective (cidal value 100 µg/ml) and the pathogen was not killed by the other five disinfectants. In experiments on agar plates, bronopol and chloramine T were stimulating to the growth of A. bisporus. Growing mushroom caps treated with bronopol remained white, whereas caps treated with the other five disinfectants turned brown within 30 min. It is thus likely that bronopol could be used to control the source of bacterial blotch epidemics in mushroom growing, which previous work has shown to be in the casing.

Typing methods for Proteus rettgeri: comparison of biotype, antibiograms, serotype, and bacteriocin production

Two hunderd five strains of Proteus rettgeri from epidemic and nonepidemic sources were differentiated by a new biotyping scheme, agglutination in O antisera, antimicrobial resistance patterns, and a new scheme based on bacteriocin production. The P. rettgeri were divided into 10 groups by their fermentation of lactose, sucrose, D-mannitol, and salicin. These groups were then subdivided into 19 biotypes by other biochemical reactions. Bacteriocin production was tested by the cross-streak method. Thirty-four bacteriocin-sensitive indicator strains were evaluated, and 16 were selected for the final scheme and used to type the 205 P. rettgeri, which were divided into 15 bacteriocin types. Serologically, 43% of the P. rettgeri were O42, 13% were untypable, 4% were O15, and 3% each were O33, O64, and O84 in addition to 31 remaining serotypes. Strains of P. rettgeri from known outbreaks contained fewer biotypes, O groups, and bacteriocin types and were more resistant to antimicrobial agents than endemic strains. Strains with common patterns with all four marker systems were frequently associated with outbreaks. A strong correlation between multiple antibiotic resistance and bacteriocin production was shown.

Investigation into the source of epidemics of infantile gastroenteritis in Coondapur.

Investigation into the source of epidemics of infantile gastroenteritis in Coondapur.