PubMed · 376562
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K Crossley, K Mead. 1979. A modified device for replica plating.. https://doi.org/10.1136/jcp.32.4.409
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BACKGROUND: Blood culture is one of the most important bacteriological examinations with important clinical and therapeutic consequences. Blood cultures should be ordered in all patients with signs suggesting septicemia, endocarditis or severe infection (pneumococcal pneumonia, bacterial meningitis with bloodstream dissemination). Blood culture methods have evolved considerably over the last twenty years. After using manual methods for many years, read by non-standardized visual methods, the development of media with defined compositions and supplemented to allow growth of bacteria difficult to culture has been associated with the development of automatic blood culture devices. AUTOMATIC DEVICES: These devices have undergone rapid improvement. Semi-automatic devices (Bactec NR-660) were rapidly followed by completely automatic techniques, including four devices currently available: since 1989 Bio-Argos (Rio-Rad) and Bact/Alert (Organon-Teknika) and in 1993, Bactec 9240 (Becton-Dickinson) and Vital (BioMérieux). All these devices allow automatic detection of CO2 produced during bacterial growth. Automatic reading systems provide continuous output avoiding the need for invasive methods and thus the risk of contamination in addition to saving time. Potential application to achieve quantitative blood cultures for intensive care units is in the development stage. CONSEQUENCES: The reliability of these devices is well recognized and their contribution to severe bacterial infection is undeniable. There are certain limitations however related to material cost and the non-identification of the pathogen involved. Molecular biology techniques open new perspectives in this field. The evolution of techniques, definitions, and pathogenic approach to septicemia must be revisited as new infectious situations have been identified at the same time as new investigation tools resulting from considerable technological progress. New methods of blood culture have largely contributed to this progress.
The coliform group has been used extensively as an indicator of water quality and has historically led to the public health protection concept. The aim of this review is to examine methods currently in use or which can be proposed for the monitoring of coliforms in drinking water. Actually, the need for more rapid, sensitive and specific tests is essential in the water industry. Routine and widely accepted techniques are discussed, as are methods which have emerged from recent research developments.Approved traditional methods for coliform detection include the multiple-tube fermentation (MTF) technique and the membrane filter (MF) technique using different specific media and incubation conditions. These methods have limitations, however, such as duration of incubation, antagonistic organism interference, lack of specificity and poor detection of slow-growing or viable but non-culturable (VBNC) microorganisms. Nowadays, the simple and inexpensive membrane filter technique is the most widely used method for routine enumeration of coliforms in drinking water.The detection of coliforms based on specific enzymatic activity has improved the sensitivity of these methods. The enzymes beta-D galactosidase and beta-D glucuronidase are widely used for the detection and enumeration of total coliforms and Escherichia coli, respectively. Many chromogenic and fluorogenic substrates exist for the specific detection of these enzymatic activities, and various commercial tests based on these substrates are available. Numerous comparisons have shown these tests may be a suitable alternative to the classical techniques. They are, however, more expensive, and the incubation time, even though reduced, remains too long for same-day results. More sophisticated analytical tools such as solid phase cytometry can be employed to decrease the time needed for the detection of bacterial enzymatic activities, with a low detection threshold. Detection of coliforms by molecular methods is also proposed, as these methods allow for very specific and rapid detection without the need for a cultivation step. Three molecular-based methods are evaluated here: the immunological, polymerase chain reaction (PCR) and in-situ hybridization (ISH) techniques. In the immunological approach, various antibodies against coliform bacteria have been produced, but the application of this technique often showed low antibody specificity. PCR can be used to detect coliform bacteria by means of signal amplification: DNA sequence coding for the lacZ gene (beta-galactosidase gene) and the uidA gene (beta-D glucuronidase gene) has been used to detect total coliforms and E. coli, respectively. However, quantification with PCR is still lacking in precision and necessitates extensive laboratory work. The FISH technique involves the use of oligonucleotide probes to detect complementary sequences inside specific cells. Oligonucleotide probes designed specifically for regions of the 16S RNA molecules of Enterobacteriaceae can be used for microbiological quality control of drinking water samples. FISH should be an interesting viable alternative to the conventional culture methods for the detection of coliforms in drinking water, as it provides quantitative data in a fairly short period of time (6 to 8 h), but still requires research effort. This review shows that even though many innovative bacterial detection methods have been developed, few have the potential for becoming a standardized method for the detection of coliforms in drinking water samples.
Pseudomonas aeruginosa has been implicated as a foodborne and waterborne pathogen and is now considered a primary infectious agent. In the present study, the survival of P. aeruginosa inoculated in mineral water was evaluated by drop counts on Pseudomonas Agar Base (PAB), PAB with CN supplement X107, PAB with cetrimide, PAB with nalidixic acid, and these media with added FeSO(4). Initial counts, before starvation, were the same in all media tested. Following this period, P. aeruginosa became sensitive to PAB with added cetrimide. The addition of FeSO(4) did not improve the recovery of stressed P. aeruginosa but gave colonies a typical dark brown colour being easily differentiated from other species that can grow at 42 degrees C. The modified Pseudomonas agar medium was also tested with several P. aeruginosa strains, other species of Pseudomonas, and other genera. Only P. aeruginosa strains (pyocyanin positive) produced the typical colonies. Our results demonstrate that Pseudomonas agar with ferrous sulphate, used for the differentiation of P. aeruginosa colonies, and nalidixic acid, used as an inhibitor of Gram-positive bacteria, might be a useful medium for the detection of injured P. aeruginosa in mineral water.