Spotted fever rickettsiosis in South Africa: Evaluation of laboratory diagnostic capacity and inter-laboratory comparison of serological testing.

BACKGROUND: Spotted fever rickettsiosis, also known as tick bite fever (TBF), is a common infectious disease in South Africa (SA). Although the diagnosis of TBF is often based on clinical grounds only, laboratory testing is important to confirm the diagnosis and can contribute to case management in the light of a myriad of differential diagnoses, and in complicated cases. OBJECTIVES: To report on the availability and scope of laboratory tests for investigating suspected cases of TBF in SA, and the outcome of an inter-laboratory comparison (ILC) conducted for serological tests. METHODS: A self-administered questionnaire was circulated to major pathology laboratories in SA to determine what TBF tests they offered for TBF investigation. In addition, a clinical panel was provided to willing laboratories in order to perform an ILC of the serological tests. RESULTS: Serological tests for TBF were available from five laboratories serving both the private and state medical sectors in SA. There was no standardised testing platform or result interpretation across the different laboratories. Polymerase chain reaction (PCR) tests were less frequently available, and not available to state-operated facilities. The outcome of the ILC indicated varied performance and interpretation of serological results for TBF. CONCLUSIONS: Laboratory investigation for TBF is routinely and widely available in SA. Both serological and PCR-based methods were varied, and the lack of standardisation and interpretation of tests needs to be addressed to improve the overall quality of TBF diagnosis in SA. The utility of ILC to identify problem areas in serological testing for TBF is highlighted, and laboratories in SA are encouraged to use it to improve the quality of testing.

Molecular characterization of a hepatitis E virus isolate from Namibia.

Hepatitis E virus (HEV) causes sporadic and epidemic acute viral hepatitis in many developing countries. In Africa, hepatitis E has been documented by virus detection (reverse transcriptase polymerase chain reaction, RT-PCR) in Egypt, Chad, Algeria, Morocco and Tunisia. Cases of presumptive hepatitis E also have been documented by detection of antibody to HEV in the Sudan, Kenya, Ethiopia, Somalia, Djibouti and South Africa. Recently, we reported the recovery of 9 isolates of HEV from feces collected during an outbreak of jaundice in Namibia. These specimens were stored frozen for many years at the South African Institute for Medical Research awaiting new methods to determine the etiology of jaundice. HEV genomic sequences were detected by antigen-capture RT-PCR with primers that amplified 2 independent regions of the HEV genome (ORF-2 and ORF-3). To further characterize the HEV 83-Namibia isolates, we determined the nucleotide (nt) sequence of the 3' end of the capsid gene (296 of 1, 980 nt in ORF-2) and ORF-3 for 1 isolate. The capsid gene sequence shared 86% identity with the prototype Burma strain and up to 96% identity with other African strains at the (nt) level, and 99% identity with Burma or other Africa strains at the amino acid level. A 188 (nt) fragment amplified from ORF-3 was also highly homologous to other HEV but was too short for meaningful comparison. Phylogenetic analysis indicated that HEV 83-Namibia is closely related to other African isolates, and differs from Burmese, Mexican and Chinese HEV. These data link the HEV causing the 1983 Namibia outbreak to more recent HEV transmission in northern and sub-Saharan Africa, suggesting this subgenotype of HEV is firmly established throughout the continent.

Chloroquine-resistant isolates of Plasmodium falciparum with alternative CG2 omega repeat length polymorphisms.

A particular polymorphism in the cg2 gene has previously been linked to chloroquine resistance in reference isolates of Plasmodium falciparum. To assess the association of this polymorphism with chloroquine resistance in field specimens of P. falciparum, we analyzed the omega repeat region of the cg2 gene in 47 isolates of P. falciparum collected in the Ingwavuma District of northern KwaZulu-Natal, South Africa. Polymerase chain reaction (PCR) primers, which were designed to amplify the region of DNA surrounding the omega repeat, were used to obtain omega repeat PCR products from the field isolates. The PCR product for each isolate varied in length, depending on the number of cg2 omega repeats for that isolate. We found that several in vivo and in vitro chloroquine-resistant isolates of P. falciparum did not have the expected 16 omega repeats. These results suggest that the link between the cg2 polymorphism and chloroquine resistance identified previously may not apply in all malarious areas.

Unusual case of Acanthamoeba polyphaga and Pseudomonas aeruginosa keratitis in a contact lens wearer from Gauteng, South Africa.

Acanthamoeba species can cause a chronic, progressive ulcerative keratitis of the eye which is not responsive to the usual antimicrobial therapy and is frequently mistaken for stromal herpes keratitis. An unusual case of coinfection with Acanthamoeba polyphaga and Pseudomonas aeruginosa as causes of corneal keratitis in a contact lens wearer from Gauteng, South Africa, is reported. These two pathogens have previously been assumed to be selectively exclusive. Cysts of the isolated acanthameba tolerated an incubation temperature of 40 degrees C, indicating a pathogenic species. This case highlights the importance of culture methods in the diagnosis of corneal infection and the choice of treatment regimen. The patient's history of careless contact lens-disinfecting habits emphasizes the need to adhere strictly to recommended methods of contact lens care.

In vitro activities of 14 antibiotics against 100 human isolates of Yersinia pestis from a southern African plague focus.

A limited repertoire of antimicrobial agents is currently in use for the treatment of plague. We investigated the in vitro activities of some newer antimicrobial agents against Yersinia pestis. Among the injectable agents tested, cefotaxime was the most active, and among the oral agents, both levofloxacin and ofloxacin were highly active, with MICs at which 90% of isolates are inhibited of < 0.03 microgram/ml. the susceptibilities to the ketolide RU004 and the penem faropenem warrant attention. The enhanced activities of quinolones against Y. pestis suggest that these agents should be further investigated for the treatment of human plague in the future.

Investigation of contaminated parenteral nutrition fluids associated with an outbreak of Serratia odorifera septicaemia.

An outbreak of fatal septicaemia caused by Serratia odorifera biotype 1 involved infants at several hospitals; the common vehicle of infection was contaminated parenteral nutrition fluid. The transfusate had been made up in a flexible film isolator system. The implicated organism was recovered from surfaces inside the isolator, despite routine decontamination procedures having been carried out shortly before. Our investigation into the origin of contamination revealed several shortcomings in the infusate compounding process. We noted deficiencies in cleaning and decontamination procedures, and in storage and sterility testing policies, but the origin and mechanism of the contamination were unclear. Withdrawal of parenteral nutrition products and revision of decontamination procedures terminated the outbreak. The efficacy of peracetic acid treatment of flexible film isolators, given the circumstances of this outbreak, may need further investigation. Regular training and assessment of admixture technicians is important.

Sporotrichosis following a rodent bite. A case report.

A ten year old boy developed lymphocutaneous sporotrichosis following a wild rodent bite. The infection was successfully treated with potassium iodide. Sporotrichosis in humans has followed bites, pecks and stings inflicted by a variety of animals, birds and insects. Many species of animals are susceptible to infection by Sporothrix schenkii, but transmission from infected animals to man is uncommon.

Blastomyces dermatitidis infections in the RSA.

Twenty cases of blastomycosis have been confirmed in the RSA, 9 of which are presented for the first time. Patients came from all four provinces and the mean age was 40 years. Six cases were diagnosed between 1985 and 1987. Differences between strains of Blastomyces dermatitidis isolated in the RSA and in North America include morphological and cultural characteristics, mycelial-yeast conversion, antigenic structure, and compatibility in cross-mating experiments. The diagnosis of this disease can be made by direct examination of unstained specimens, by histological examination or by culture of the organism. Culture should be attempted in all cases for confirmation of microscopic findings.