M.M. Ehlers

Prevalence, quantification and typing of adenoviruses detected in river and treated drinking water in South Africa

Aims:  Human adenoviruses (HAds), of which there are 51 serotypes, are associated with gastrointestinal, respiratory, urinary tract and eye infections. The importance of water in the transmission of HAds and the potential health risks constituted by HAds in these environments are widely recognized. Adenoviruses have not previously been quantified in river and treated drinking water samples. In this study, HAds in river water and treated drinking water sources in South Africa were detected, quantified and typed.

Incidence of adenoviruses in raw and treated water

Adenoviruses are of major public health importance and are associated with a variety of clinical manifestations, i.e. gastroenteritis, eye infections and respiratory infections. The importance of water in the epidemiology of adenoviruses and the potential health risks constituted by adenoviruses in water sources and supplies are widely recognised. This study was conducted to assess the incidence of human adenoviruses in raw and treated water systems. Various raw and treated water were routinely monitored for the presence of adenoviruses, over a 1-year period (July 2000-June 2001). The supplies were derived from acceptable quality surface water sources using treatment processes, which conform to international standards for the production of safe drinking water. Adenoviruses were detected by firstly amplifying the viruses in cell cultures and then amplifying the extracted nucleic acids of these viruses using molecular techniques (nested PCR). The results indicated human adenoviruses present in 13 (12.75%) of the raw and 9 (4.41%) of the treated water samples tested. The combination of cell culture and nested PCR has proved to be a quick and reliable method for the detection of adenoviruses in water environments.

Detection of enteroviruses in treated drinking water

This study deals with the routine monitoring of drinking water for the presence of enteroviruses, over a period of 1 year. A rapid and simple method was employed for the simultaneous detection and typing of enteroviruses in large-volume water samples. This included an integrated cell culture/nested PCR approach, followed by restriction enzyme analysis. The two drinking water supplies studied were derived from acceptable quality surface water sources using treatment processes, which conform to international specifications for the production of safe drinking water. Enteroviruses (predominantly coxsackie B viruses) were detected in 11% and 16% of the drinking water samples from two treatment plants, respectively. This study confirms that acceptable water quality indicators do not necessarily reflect the virus content of drinking water.

The occurrence of E. coli O157:H7 in South African water sources intended for direct and indirect human consumption.

The occurrence of Escherichia coli O157:H7 in selected water samples in South Africa was investigated. The chromogenic Rainbow agar O157 medium designed for the rapid identification of E. coli O157:H7 was used for the detection of these organisms in various river-water samples in the Vaal Barrage Reservoir drainage basin of South Africa. A total of 204 samples were obtained from 15 sites where water was used for direct and indirect human consumption. Samples were filtered through Gelman filter-units and incubated on Rainbow agar O157 which produced different colours according to the bacterial chromogenic properties. Six hundred and sixty-three suspected E. coli O157:H7 colonies, with colours ranging between dark blue, grey and black, were subcultured onto sorbitol-MacConkey agar and screened for different virulence factors specific for E. coli O157:H7 and agglutination with anti-E. coli O157 antiserum. The results indicated that none of the suspected colonies contained all of the virulence factors necessary to classify them as E. coli O157:H7. None of these organisms agglutinated with antisera against E. coli O157. The probability of being infected with E. coli O157:H7 from direct or indirect consumption of these river water sources is therefore low. Some samples did, however, contain enterohaemorrhagic E. coli virulence properties, such as Stx1, Stx2 and enterohaemolysin, which might impose a health risk if ingested.

Detection and risk assessment of adenoviruses in swimming pool water

Aims:  The role of swimming pool water as a source of human adenovirus (HAd) infection has previously been demonstrated. In this study, the risk of infection of HAds detected in a survey of swimming pool water from two indoor and one outdoor swimming pools over a period of 1 year was assessed.

Molecular identification and genotyping of MRSA isolates

The aim of this study was to identify and characterize 97 methicillin-resistant Staphylococcus aureus (MRSA) isolates. Two conventional multiplex PCR assays, a real-time PCR assay and two PCR-based genotyping techniques including the spa- and hypervariable region (HVR)-typing methods were used to identify and characterize 97 MRSA strains isolated between April 2006 to September 2007 from the Steve Biko Academic Hospital. All MRSA isolates were positive for 16S rRNA gene, 99% were positive for the mecA gene and 4% positive for the Panton-Valentine leukocidin (PVL) gene. Staphylococcal cassette chromosome mec (SCCmec) typing showed 67% of isolates were SCCmec II [health-care-associated MRSA (HA-MRSA)], 14% were SCCmec III (HA-MRSA) and 4% were SCCmec IVd [community-associated MRSA (CA-MRSA)]. These CA-MRSA isolates showed a prevalence of 100% for the PVL gene. Using spa typing, three distinct clusters could be identified while HVR typing revealed six different clusters. CA-MRSA isolates were clustered together using spa and HVR typing. This study showed the prevalence of the CA-MRSA strains, PVL genes, the SCCmec types and the clonality of the MRSA strains. The high prevalence of the PVL gene in CA-MRSA isolates already residing in intensive care units was alarming and indicated the emergence of new MRSA lineages with a particular fitness for community and hospital transmission.

Risk assessment of adenoviruses detected in treated drinking water and recreational water

Aims:  Human adenoviruses (HAds) have previously been detected in sewage and polluted river and dam water, as well as treated drinking water. The 51 serotypes of HAds cause a wide range of infections with clinical manifestations associated with the gastrointestinal, respiratory and urinary tracts, and the eyes. Water may play a meaningful role in the transmission of many of these HAd serotypes, specifically the enteric HAds which are transmitted via the faecal–oral route. The presence of these viruses in water used for drinking and recreational purposes is considered to constitute a potential health risk. In this study, the risk of infection by the group of HAds previously detected over a period of 1 year in selected drinking water supplies, as well as river and dam water used for recreational purposes, was assessed.

Antimicrobial susceptibility patterns of Ureaplasma species and Mycoplasma hominis in pregnant women

BackgroundGenital mycoplasmas colonise up to 80% of sexually mature women and may invade the amniotic cavity during pregnancy and cause complications. Tetracyclines and fluoroquinolones are contraindicated in pregnancy and erythromycin is often used to treat patients. However, increasing resistance to common antimicrobial agents is widely reported. The purpose of this study was to investigate antimicrobial susceptibility patterns of genital mycoplasmas in pregnant women.MethodsSelf-collected vaginal swabs were obtained from 96 pregnant women attending an antenatal clinic in Gauteng, South Africa. Specimens were screened with the Mycofast Revolution assay for the presence of Ureaplasma species and Mycoplasma hominis. The antimicrobial susceptibility to levofloxacin, moxifloxacin, erythromycin, clindamycin and tetracycline were determined at various breakpoints. A multiplex polymerase chain reaction assay was used to speciate Ureaplasma positive specimens as either U. parvum or U. urealyticum.ResultsSeventy-six percent (73/96) of specimens contained Ureaplasma spp., while 39.7% (29/73) of Ureaplasma positive specimens were also positive for M. hominis. Susceptibilities of Ureaplasma spp. to levofloxacin and moxifloxacin were 59% (26/44) and 98% (43/44) respectively. Mixed isolates (Ureaplasma species and M. hominis) were highly resistant to erythromycin and tetracycline (both 97% resistance). Resistance of Ureaplasma spp. to erythromycin was 80% (35/44) and tetracycline resistance was detected in 73% (32/44) of Ureaplasma spp. Speciation indicated that U. parvum was the predominant Ureaplasma spp. conferring antimicrobial resistance.ConclusionsTreatment options for genital mycoplasma infections are becoming limited. More elaborative studies are needed to elucidate the diverse antimicrobial susceptibility patterns found in this study when compared to similar studies. To prevent complications in pregnant women, the foetus and the neonate, routine screening for the presence of genital mycoplasmas is recommended. In addition, it is recommended that antimicrobial susceptibility patterns are determined.

Evaluation of the GenoType® MTBDRsl assay for susceptibility testing of second-line anti-tuberculosis drugs.

BACKGROUND The GenoType® MTBDRsl assay is a new rapid assay for the detection of resistance to second-line anti-tuberculosis drugs. OBJECTIVE To evaluate the MTBDRsl assay on 342 multidrug-resistant tuberculosis isolates for resistance to ofloxacin (OFX), kanamycin (KM), capreomycin (CPM) and ethambutol (EMB), to compare the results to the agar proportion method, and to test discrepant results using DNA sequencing. RESULT The sensitivity and specificity of the MTBDRsl assay were respectively 70.3% and 97.7% for OFX, 25.0% and 98.7% for KM, 21.2% and 98.7% for CPM and 56.3% and 56.0% for EMB. DNA sequencing identified mutations that were not detected by the MTBDRsl assay. The 8/11 phenotypically OFX-resistant isolates had mutations in gyrA (2/8 had an additional mutation in the gyrB gene), 1/11 had mutations only in the gyrB gene, 6/21 phenotypically KM-resistant isolates had mutations in the rrs gene, and 7/26 and 20/26 phenotypically CPM-resistant isolates had mutations in the rrs and tlyA genes. CONCLUSION The MTBDRsl assay showed lower sensitivity than previous studies. The assay performed favourably for OFX; however, it was less sensitive in the detection of KM/CPM resistance and demonstrated low sensitivity and specificity for EMB resistance. It is recommended that the MTBDRsl assay include additional genes to achieve better sensitivity for all the drugs tested.

Emergence of class 1 integron-associated GES-5 and GES-5-like extended-spectrum β-lactamases in clinical isolates of Pseudomonas aeruginosa in South Africa

Several different Guiana extended-spectrum (GES) enzymes have been described occurring in Enterobacteriaceae and Pseudomonas aeruginosa worldwide. Polymerase chain reaction and gene sequencing analysis confirmed bla(GES) genes identified in three P. aeruginosa clinical isolates from South Africa as bla(GES-5) and bla(GES-5)-like, respectively. Compared with GES-1, the GES-5-like protein exhibited an A21E amino acid change, a novel mutation not previously described in this family. Integron structures identified upstream from the bla(GES-5) and bla(GES-5)-like genes were found to be identical to bla(GES-2)-carrying integrons described previously from the same geographical region. These findings confirm the establishment and persistence of integron-associated GES-type extended-spectrum beta-lactamases (ESBLs) in the South African nosocomial environment. This study describes the first isolation of class 1 integron-associated bla(GES-5) and the emergence of a novel GES-5-like ESBL in South Africa.