Heterotrophic plate count methodology in the United States.

In the United States (US), the history of bacterial plate counting (BPC) methods used for water can be traced largely through Standard Methods for the Examination of Water and Wastewater (Standard Methods). The bacterial count method has evolved from the original Standard Methods (1st edition, 1905) plate count which used nutrient gelatin and incubation at 20 degrees C for 48 h, to the HPC method options in the latest edition of Standard Methods that provide greater flexibility of application, depending on the data needs of the water analyst. The use of agar-agar as a gelling agent, replacing gelatin, allowed the use of higher incubation temperatures and resulted in the "body temperature count" (37 degrees C) found in the 3rd through the 8th edition of Standard Methods.

Heterotrophic plate count bacteria--what is their significance in drinking water?

While the literature documents the universal occurrence of heterotrophic plate count (HPC) bacteria in soils, foods, air, and all sources of water, there is a lingering question as to whether this group of organisms may signal an increased health risk when elevated populations are present in drinking water. This paper reviews the relevant literature on HPC bacteria in drinking water, the lack of clinical evidence that elevated populations or specific genera within the HPC flora pose an increased health risk to any segment of the population, and the appropriate uses of HPC data as a tool to monitor drinking water quality changes following treatment. It finds no evidence to support health-based regulations of HPC concentrations.

Assessment of equine fecal contamination: the search for alternative bacterial source-tracking targets.

16S rDNA clone libraries were evaluated for detection of fecal source-identifying bacteria from a collapsed equine manure pile. Libraries were constructed using universal eubacterial primers and Bacteroides-Prevotella group-specific primers. Eubacterial sequences indicated that upstream and downstream water samples were predominantly beta- and gamma-Proteobacteria (35 and 19%, respectively), while the manure library consisted predominantly of Firmicutes (31%) and previously unidentified sequences (60%).

Molecular characterization of bacteria inhabiting a water distribution system simulator.

The objective of this study was to monitor the impact of chlorination and chloramination treatments on heterotrophic bacteria (HB) and ammonia-oxidizing bacteria (AOB) inhabiting a water distribution system simulator. HB densities decreased while AOB densities increased when chloramine was added. AOB densities decreased below detection limits after the disinfection treatment was switched back to chlorination.

Microbial source tracking: state of the science.

Although water quality of the Nation's lakes, rivers and streams has been monitored for many decades and especially since the passage of the Clean Water Act in 1972, many still do not meet the Act's goal of "fishable and swimmable". While waterways can be impaired in numerous ways, the protection from pathogenic microbe contamination is most important for waters used for human recreation, drinking water and aquaculture. Typically, monitoring methods used for detecting potential pathogenic microorganisms in environmental waters are based upon cultivation and enumeration of fecal indicator bacteria (i.

Improving waterborne disease outbreak investigations.

This article is a summary of discussions held and recommendations made at a workshop for the investigation of waterborne disease outbreaks in Chapel Hill, North Carolina, December 7-8, 1998. Suspected waterborne outbreaks in the United States are primarily investigated by state and local public health officials who may infrequently conduct enteric disease outbreak investigations. Thus, it is important that officials have a formal plan to ensure that epidemiological studies are methodologically sound and that effective collaboration occurs among the epidemiologists, scientists, and engineers who will conduct the investigations.

Deletion of the serotonin 5-HT2C receptor PDZ recognition motif prevents receptor phosphorylation and delays resensitization of receptor responses.

Phosphorylation-deficient serotonin 5-HT(2C) receptors were generated to determine whether phosphorylation promotes desensitization of receptor responses. Phosphorylation of mutant 5-HT(2C) receptors that lack the carboxyl-terminal PDZ recognition motif (Ser(458)-Ser-Val-COOH; DeltaPDZ) was not detectable based on a band-shift phosphorylation assay and incorporation of (32)P. Treatment of cells stably expressing DeltaPDZ or wild-type 5-HT(2C) receptors with serotonin produced identical maximal responses and EC(50) values for eliciting [(3)H]inositol phosphate formation.

Inactivation of Helicobacter pylori by chlorination.

Three strains of Helicobacter pylori were studied to determine their resistance to chlorination. The organisms were readily inactivated by free chlorine and should therefore be controlled by disinfection practices normally employed in the treatment of drinking water.

Doxycycline reduces early neurologic impairment after cerebral arterial air embolism in the rabbit.

Background: Previous studies indicate leukocytes play a role in the pathogenesis of cerebral arterial air embolism. Because doxycycline inhibits numerous leukocyte activities, the authors hypothesized doxycycline would decrease neurologic impairment after cerebral arterial air embolism.

Methods: New Zealand White rabbits anesthetized with methohexital received either intravenous saline (n = 7) or 10 mg/kg doxycycline (n = 7) 1 h before administration of 100 microl/kg of air into the internal carotid artery.

Comparison of a modified double-lumen endotracheal tube with a single-lumen tube with enclosed bronchial blocker.

This study compared the modified BronchoCath double-lumen endotracheal tube with the Univent bronchial blocker to determine whether there were objective advantages of one over the other during anesthesia with one-lung ventilation (OLV). Forty patients having either thoracic or esophageal procedures were randomly assigned to one of two groups. Twenty patients received a left-side modified BronchoCath double-lumen tube (DLT), and 20 received a Univent tube with a bronchial blocker.

Somatosensory evoked potentials correlate with neurological outcome in rabbits undergoing cerebral air embolism.

Background And Purpose: Somatosensory evoked potentials (SSEPs) have been used as an outcome measure in models of cerebral air embolism despite the lack of studies correlating SSEPs with other measures of neurological injury. We examined the relationship between SSEPs and neurological impairment in the setting of cerebral air embolism.

Methods: Anesthetized New Zealand White rabbits received either 0, 50, 100, or 150 microL/kg of air into the internal carotid artery.

Detection of Escherichia coli O157:H7 in water from coliform enrichment cultures.

Environmental water samples were seeded with Escherichia coli O157:H7 and the bacterium was recovered using a traditional coliform enrichment procedure followed by selective plating on sorbitol MacConkey agar and biochemical and serological characterization. Assays for beta-glucuronidase and glutamate decarboxylase were found to be useful procedures for screening suspected isolates. The organism was not recovered in a survey of various water samples.

Theoretical assessment of normobaric oxygen therapy to treat pneumocephalus.

Background: Pneumocephalus has been linked to several clinical conditions, including headache, lethargy, and even brain herniation or death. The effects of different normobaric oxygen concentrations and durations of therapy on the rate of air absorption were examined.

Methods: An existing mathematical model of inert gas absorption was used.

Heparin reduces neurological impairment after cerebral arterial air embolism in the rabbit.

Background And Purpose: Neurological injury after cerebral air embolism may be due to thromboinflammatory responses at sites of air-injured endothelium. Because heparin inhibits multiple thromboinflammatory processes, we hypothesized that heparin would decrease neurological impairment after cerebral air embolism.

Methods: To first establish a dose of air that would cause unequivocal neurological injury, anesthetized New Zealand White rabbits received either 0, 50, 100, or 150 microL/kg of air into the internal carotid artery (n = 5 in each group).

Marked hemodilution increases neurologic injury after focal cerebral ischemia in rabbits.

Moderate hemodilution (hematocrit approximately 30%) reduces neurologic injury after focal cerebral ischemia. In contrast, both clinical and experimental studies suggest that marked hemodilution (hematocrit < 30%) may exacerbate neurologic injury. We compared the effect of marked versus minimal hemodilution on cerebral infarct volume after focal cerebral ischemia in rabbits.

A comparison of anesthetic techniques for awake intubation in neurosurgical patients.

Two different methods of achieving upper airway anesthesia for awake fiberoptic intubation were prospectively compared in patients undergoing surgery for cervical spine instability. Forty patients were randomized to either topical anesthesia or nerve block groups. Topical anesthesia patients were administered nebulized 4% lidocaine (approximately 20 ml) via the oropharynx plus a transtracheal injection of 4% lidocaine (3 ml).

Rapid Glutamate Decarboxylase Assay for Detection of Escherichia coli.

Volume 59, no. 12, p. 4347, column 1, line 3 from bottom: "500 x g" should read "2,500 x g.

Occurrence of high-level aminoglycoside resistance in environmental isolates of enterococci.

High-level resistance to aminoglycosides was observed in environmental isolates of enterococci. Various aquatic habitats, including agricultural runoff, creeks, rivers, wastewater, and wells, were analyzed. Strains of Enterococcus faecalis, E.

The incidence of pneumocephalus after supratentorial craniotomy. Observations on the disappearance of intracranial air.

Background: Pneumocephalus occurs in a variety of clinical settings and has important anesthetic implications, particularly if N2O is used. One common cause of pneumocephalus is a craniotomy or craniectomy, and therefore, patients undergoing these neurosurgical procedures may be at increased risk for the development of tension pneumocephalus if N2O is used during a subsequent anesthetic. However, because the rate at which a postoperative pneumocephalus resolves has not been well defined, the duration of this risk period is unknown.

Rapid glutamate decarboxylase assay for detection of Escherichia coli.

A rapid test procedure for the enzyme glutamate decarboxylase was developed for detection of Escherichia coli. The assay procedure was able to confirm the presence of E. coli in enteric broth cultures with 95% specificity for both pure cultures and environmental samples.

Evaluation and simplification of the assimilable organic carbon nutrient bioassay for bacterial growth in drinking water.

A modified assimilable organic carbon (AOC) bioassay is proposed. We evaluated all aspects of the AOC bioassay technique, including inoculum, incubation water, bioassay vessel, and enumeration technique. Other concerns included eliminating the need to prepare organic carbon-free glassware and minimizing the risks of bacterial and organic carbon contamination.

Secondary hypotensive insults in a rat forebrain ischemia model.

Previous studies have shown that the recently injured brain has an increased sensitivity to subsequent brief episodes of severe ischemia. This investigation was designed to assess whether less severe secondary insults, which alone would be incapable of producing injury, exacerbate brain damage resulting from a primary episode of global ischemia. Rats were subjected to either 10 min of 2-vessel forebrain ischemia (primary insult alone), 20 min of hypotension (mean arterial pressure, MAP = either 40 or 25 mmHg) without vessel occlusion (secondary insult alone), or 10 min ischemia followed 1 h later by the hypotensive challenge (primary + secondary insult).