Tags: Imipenem

Actinomycetes

Originally thought to be fungi due to their hyphae-like appearance, they are now recognized as bacteria based on their cell wall components, reproduction by fission without sporulation or budding, inhibition by antibacterial agents, and molecular phylogenetic analysis. The actinomycete chromosomes contain a high content of guanosine and cytosine.

Nocardia

Nocardia spp. are strictly aerobic, ubiquitous soil-dwelling organisms that are largely responsible for the decomposition of organic plant material. Infection usually occurs via inhalation of these organisms in airborne dust particles, leading to pulmonary disease.

Important Anaerobes

Anaerobic bacteria are the predominant component of the normal microbial flora of the human body. The following sites harbor the vast majority of them:

Toxin-Mediated Infections

Tetanus is a disease of global incidence produced by the toxin of Clostridium tetani. The risk of acquiring it increases in people > 60 years of age and in neonates, especially in Third World countries where poor sanitary conditions predispose to umbilical stump contamination. Immunization campaigns have played a crucial role in bringing about the observed decreasing incidence in the United States. The pathogenesis of tetanus involves the absorption of preformed toxin, or, less commonly, invasion of toxin-producing organisms from contaminated wounds; it may complicate surgical wounds colonized with C tetani.

Pseudomonas Aeruginosa

The genus Pseudomonas consists of a number of human pathogens, the most important of which is Pseudomonas aeruginosa. P aeruginosa is an opportunistic pathogen found widely in soil, water, and organic material, reflecting its limited nutritional requirements. A moist environment is favored. Human colonization in the community is rare, and, when it occurs, the skin, gut, and upper or lower airway are colonized.

Other Pseudomonas Species of Medical Importance

This organism is endemic in Southeast Asia with the highest prevalence in Thailand. The organism is a saprophyte living in the soil. Infection may be subclinical, acute, subacute, or chronic.

Infection in Patients With Aids

Paeruginosa infections may occur in patients with AIDS. Risk factors for infection include a CD4 count of < 100 cells/mL3, neutropenia or functional neutrophil defects, intravascular catheterization, hospitalization, and prior use of antibiotics including ciprofloxacin or trimethoprim-sulfamethoxazole. Many cases are community acquired. Bacteremia is common, and the lung or an intravenous catheter is the most frequent portal of entry.

Gram-Positive Aerobic Bacilli

L monocytogenes is found in soil, fertilizer, sewage, and stream water; on plants; and in the intestinal tracts of many mammals. It is a foodborne pathogen that causes bacteremic illness and meningoencephalitis, with few if any gastrointestinal manifestations.

Group B Streptococcus (S Agalactiae) Clinical Syndromes

Early-onset group B streptococcal neonatal infection has three major clinical expressions: bacteremia with no identifiable focus of infection, pneumonia, and meningitis (Box 1). Signs and symptoms of early-onset group B streptococcal neonatal infection include lethargy, poor feeding, jaundice, abnormal temperature, grunting respirations, pallor, and hypotension.

Other Gram-Positive Cocci

Viridans streptococci are part of the normal microbial flora of humans and animals and are indigenous to the upper respiratory tract, the female genital tract, all regions of the gastrointestinal tract, and, most significantly, the oral cavity. Clinically significant species that are currently recognized as belonging to the viridans group of streptococci include Streptococcus anginosus S constellatus, S cristatus, S gordonii, S intermedius, S oralis, S mitis, S mutans, S cricettus, S rattis, S parasanguis, S salivarius, S thermophilus, S sanguinis, S sobrinus, and S vestibularis. Detailed studies of the ecology of strains in the oral cavity and oropharynx have been performed.