Surveillance of leptospiral carriage by feral rats in Barbados.

Rodents, particularly rats, are widely held to be the source of most human cases of leptospirosis. Feral rats were trapped at sites throughout Barbados during two six month surveys: from October to March 1986/87 and from October to March 1994/95. During the first survey, 63 rats were trapped, of which 26 (41%) were identified as Rattus rattus and 37 (59%) as Rattus norvegicus. In the second study, 100 rats were trapped, of which R. rattus comprised 24% (24) and R. norvegicus 76% (76). Cultures of blood, urine and kidney were made in EMJH medium. Leptospires were isolated from 12/63 (19%) and from 16/100 (16%) of the rats during 1986/87 and 1994/95, respectively; 27/28 isolates were recovered from the kidneys or urine or both, while only one isolate was recovered from the blood. During the first study, isolates were identified as serovars copenhageni (11) and arborea (1), while in the second study, serovars copenhageni (9), arborea (5) and bim (1) were identified; one isolate was lost before it could be identified. In the first study, antibodies were detected by microscopic agglutination at a titre of > or = 100 in 26/62 (42%) of rats tested, while in the second survey, 5/100 (5%) of rats had similar titres. In two surveys, conducted eight years apart, we confirmed that rats in Barbados are commonly infected with leptospires, and that viable organisms are found in the kidneys and urine, evidence of chronic infection and thus excretion of leptospires in rodent urine. Moreover, the predominant serovar isolated was copenhageni, of which Rattus spp. are the worldwide reservoir. There was little evidence that rats act as a reservoir for the serovar bim, the most common cause of human leptospirosis in Barbados.

The microbiological analysis of Sahara dust and its association with asthma in Barbados

Sahara or African dust originates on the African continent and its transported across the North Atlantic to Barbados and other Caribbean Islands by the North East Trade Winds. The amount of dust deposited in Barbados has shown a steady increase over the years and so has the incidence of respiratory disease and asthma. This study investigated the monthly variation of the concentration of Sahara dust in the atmosphere the presence of micro-organisms in it. It also examined whether there was any association between these and asthmatic attendances at the Asthma Bay of the Accident and Emergency Department of the Queen Elizabeth Hospital (QEH). During the one year study period, dust deposition was lowest during February and March 1996 and heaviest during April to July 1996 with the peak in April. The peak in April did not coincide with any noticeable increase in asthma attendances during that month. A total of 289 dust samples were collected and cultured. The cultures grew mainly bacillus species and fungi, including several species of Aspergillus. 43 samples (14.8 percent) grew bacilli and fungi and 5 (1.7 percent) grew organisms other than bacilli and fungi, such as micrococci. More colonies of fungi were isolated during the early part of the year and more bacilli were found during the latter part of the year when there was the peak attendance at the QEH Asthma Bay. It is concluded that the content of Sahara dust may be of greater importance to the development of asthma than the concentration of the dust.(AU)

Surveillance of leptospiral carriage by feral rats in Barbados

Rodents, particularly rats, are widely held to be the source of most human cases of leptospirosis. Feral rats were trapped at sites throughout Barbados during two-six month surveys: from October to March 1986/87 and from October to March 1994/95. During the first survey, 63 rats were trapped, of which 26 (41 percent) were identified as Rattus rattus and 37 (59 percent) as Rattus norvegicus. In the second study, 100 rats were trapped, of which R. rattus comprised 24 percent (24) and R. norvegicus 76 percent (76). Cultures of blood, urine and kidney were made in EMJH medium. Leptospires were isolated from 12/63 (19 percent) and from 16/100 (16 percent) of the rats during 1986/87 and 1994/95, respectively; 27/28 isolates were recovered from the kidneys or urine or both, while only one isolate was recovered from the blood. During the first study, isolates were identified as serovars copenhageni (11), arborea (1), while in the second study, serovars copenhageni (9), arborea (5) and bim (1) were identified; one isolate was lost before it could be identified. In the first study, antibodies were detected by microscopic agglutination at a titre of > or = 100 in 26/62 (42 percent) of rats tested, while in the second survey, 5/100 (5 percent) of rats had similar titres. In two surveys, conducted eight years aparts we confirmed that rats in Barbados are commonly infected with leptospires, and that viable organisms are found in the kidneys and urine, evidence of chronic infection and thus excretion of leptospires in rodent urine. Moreover, the predominant serovar isolated was copenhageni, of which Rattus spp. are the worldwide reservoir. There was little evidence that rats act as a reservoir for the serovar bim, the most common cause of human leptospirosis in Barbados.(AU)

Surveillance of leptospiral carriage by feral rats in Barbados

Rodents, particularly rats, are widely held to be the source of most human cases of leptospirosis. Feral rats were trapped at sites throughout Barbados during two six month surveys: from October to March 1986/87 and from October to March 1994/95. During the first survey, 63 rats were trapped, of which 26 (41) were identified as Rattus rattus and 37 (59) as Rattus norvegicus. In the second study, 100 rats were trapped, of which R. rattus comprised 24(24) and R. norvegicus 76(76). Cultures of blood, urine and kidney were made in EMJH medium. Leptospires were isolated from 12/63 (19) and from 16/100 (16) of the rats during 1986/87 and 1994/95, respectively; 27/28 isolates were recovered from the kidneys or urine or both, while only one isolate was recovered from the blood. During the first study, isolates were identified as serovars copenhageni (11) and arborea (1), while in the second study, serovars copenhageni (9), arborea (5) and bim (1) were identified; one isolate was lost before it could be identified. In the first study, antibodies were detected by microscopic agglutination at a titre of > or = 100 in 26/62 (42) of rats tested, while in the second survey, 5/100 (5) of rats had similar titres. In two surveys, conducted eight years apart, we confirmed that rats in Barbados are commonly infected with leptospires, and that viable organisms are found in the kidneys and urine, evidence of chronic infection and thus excretion of leptospires in rodent urine. Moreover, the predominant serovar isolated was copenhageni, of which Rattus spp. are the worldwide reservoir. There was little evidence that rats act as a reservoir for the serovar bim, the most common cause of human leptospirosis in Barbados.

Surveillance of leptospiral carriage in feral rats in Barbados - abstract

Rodents, particularly rats, are widely held to be the source of most human cases of leptospirosis. Feral rats were trapped at sites throughout the island of Barbados during two six month surveys, from October - March 1986/87 and 1994/95. During the first survey, 63 rats were trapped, of which 26 (41 percent) were identified as Rattus rattus and 37 (59 percent) as Rattus norvegicus. In the second study, 100 rats were trapped, of which R. rattus comprised 24 percent (24) and R. norvegicus 76 percent (76). Cultures of blood, urine and kidney were made in EMJH medium. Leptospira were isolated from 12/63 (19 percent) and from 16/100 (16 percent) of the rats during 1986/87 and 1994/95, respectively; 27/28 isolates were recovered from the kidneys or urine or both, while only one isolate was recovered from blood. During the first study, isolates were identified as serovars copenhageni (11) and arborea (1), while in the second study, serovars copenhageni (9), arborea (5) and bim (1) were identified; one isolate was lost before it could be identified. In the first study, antibodies were detected by microscopic agglutination at a titre of > 100 in 26/62 (42 percent) of rats tested, while in the second survey, 5/100 (5 percent) of rats had similar titres. In two surveys, conducted eight years apart, we confirmed that rats in Barbados are commonly infected with leptospira, and that viable organisms are found in the kidneys and urine, evidence of chronic infection and thus excretion of leptospira in rodent urine. Moreover, the predominant serovar isolated was copenhageni, of which Rattus spp. are the worldwide reservoirs. There was little evidence that rats act as a reservoir for the serovar bim, the most common cause of human leptospirosis in Barbados. (AU)

The occurrence of non-01 Vibrio cholerae in non-potable water samples in Barbados.

Fourteen freshwater or brackish-water samples taken from different sites were examined for the presence of Vibrio cholerae. Standard enrichment techniques, using pre-incubation in alkaline peptone water and plating on thiosulfate citrate bile sucrose agar (TCBS) followed by biochemical, physiological and morphological characterization of the isolates, revealed the presence of Vibrio cholerae at nine of the sites examined. Serotyping for type 01 only was performed. All the strains isolated were non-01 Vibrio cholerae.

The occurrence of non-O1 vibrio cholerae in non-potable water samples in Barbados

Fourteen freshwater or brackish-water samples taken from different sites were examined for the presence of Vibrio cholerae. Standard enrichment techniques, using pre-incubation in alkaline peptone water and plating on thiosulfate citrate bile sucrose agar (TCBS) followed by biochemical, physiological and morphological characterization of the isolates, revealed the presence of Vibrio cholerae at nine of the sites examined. Serotyping for type O1 only was performed. All the strains isolated were non-O1 Vibrio cholerae (AU)

The occurrence of non-O1 vibrio cholerae in non-potable water samples in Barbados

Fourteen freshwater or brackish-water samples taken from different sites were examined for the presence of Vibrio cholerae. Standard enrichment techniques, using pre-incubation in alkaline peptone water and plating on thiosulfate citrate bile sucrose agar (TCBS) followed by biochemical, physiological and morphological characterization of the isolates, revealed the presence of Vibrio cholerae at nine of the sites examined. Serotyping for type O1 only was performed. All the strains isolated were non-O1 Vibrio cholerae.

Effect of low intraphagolysosomal pH on antimicrobial activity of antibiotics against ingested staphylococci.

The ability of aminoglycoside antibiotics and rifampicin to kill Staphylococcus aureus that had been ingested by blood polymorphonuclear leukocytes (PMNs) in vitro was investigated. Gentamicin and streptomycin failed to kill intracellular staphylococci, possibly because they could not penetrate PMNs or were inactivated by the low intraphagolysosomal pH. Rifampicin accumulated within the leukocytes in a form that killed staphylococci in a cell-free medium, but the bactericidal activity of intracellular rifampicin against ingested staphylococci was much less than that in a cell-free system. Investigations with granules isolated from PMNs, at various pH-values, revealed that the impairment of rifampicin activity was a result of limitation of the staphylococcal growth rate by a low pH. These observations indicate that the inhibition of intraphagocytic bacterial growth by the low intraphagolysosomal pH and other phagolysosomal bacteristatic factors determines the antimicrobial activity of accumulated antibiotics.

Intraphagocytic protection of staphylococci from extracellular penicillin.

In a system in which unphagocytosed bacteria were removed by differential centrifugation after a 30-min phagocytosis period, staphylococci associated with rabbit polymorphonulcear (PMN) leukocytes were completely protected from the effects of benzyl penicillin 1 microgram/ml, but not completely protected from the effects of 5 micrograms/ml. When unphagocytosed bacteria were lysed with lysostaphin, effective protection could be observed over a range of penicillin concentrations from 0.25 to 200 micrograms/ml. 14C-benzyl penicillin failed to accumulate in rabbit PMN leukocytes, whether or not they had previously phagocytosed staphylococci, in conditions in which mouse peritoneal macrophages readily accumulated penicillin. Mixed granule extracts prepared from the PMN leukocytes interacted synergically with penicillin against staphylococci at physiological pH (7.2) but failed to show synergy at an intraphagolysosomal pH of 5.0 unless the bacteria were first sublethally treated with penicillin. Experiments in which the pH value of culture media was changed either from 7.2 to 5.0 or from 5.0 to 7.2 indicated that the partial nature of the protective effect of the intraphagolysosomal environment could be attributed to the growth-limiting effects of the low phagolysosomal pH, which prevents full expression of the synergic potential of granule contents and penicillin. The concentration-dependent nature of the protection and its incompleteness are explained by supposing that a proportion of the staphylococci not ingested during the 30-min phagocytosis period are modified by penicillin in a way that opsonises them and potentiates the intrinsic bactericidal mechanisms of the PMN leukocytes when the bacteria are subsequently ingested.

Phagocytosis measured as inhibition of uridine uptake: a method that distinguishes between surface adherence and ingestion.

Polymorphonuclear leucocytes selectively inhibited the incorporation of 14C-uridine by intracellular staphylococci. Within specified limits, the amount of radiolabel incorporated by extracellular staphylococci was related to bacterial concentration. The incorporation of labelled uridine can thus be exploited to assay the extent to which association between staphylococci and polymorphonuclear leucocytes reflects surface adherence as opposed to ingestion. A comparison of the new method with a conventional viable-count determination of leucocyte-associated bacteria shows it to be comparable in efficiency when non-immune serum is used as opsonin and superior when specific opsonin is used.