Medical Microbiology Illustrated (eBook)

S. H. Gillespie (Autor)

eBook Download: PDF | EPUB

2014 | 1. Auflage
296 Seiten
Elsevier Science (Verlag)
978-1-4831-9363-2 (ISBN)

Infos

Medical Microbiology Illustrated presents a detailed description of epidemiology, and the biology of micro-organisms. It discusses the pathogenicity and virulence of microbial agents. It addresses the intrinsic susceptibility or immunity to antimicrobial agents. Some of the topics covered in the book are the types of gram-positive cocci; diverse group of aerobic gram-positive bacilli; classification and clinical importance of erysipelothrix rhusiopathiae; pathogenesis of mycobacterial infection; classification of parasitic infections which manifest with fever; collection of blood for culture and control of substances hazardous to health. The classification and clinical importance of neisseriaceae is fully covered. The definition and pathogenicity of haemophilus are discussed in detail. The text describes in depth the classification and clinical importance of spiral bacteria. The isolation and identification of fungi are completely presented. A chapter is devoted to the laboratory and serological diagnosis of systemic fungal infections. The book can provide useful information to microbiologists, physicians, laboratory scientists, students, and researchers.

Inhalt

Front Cover 1
Medical Microbiology Illustrated 4
Copyright Page 5
Table of Contents 6
Dedication 3
Preface 8
Acknowledgements 10
Chapter 1. Introduction to clinical microbiology 12
Introduction 12
The process of microbiological diagnosis 12
Specimens 12
Sensitivity testing 18
Serology and antigen detection 19
Reporting 19
Typing 21
Computerized records 22
Chapter 2. Gram-positive cocci 23
Introduction 23
Staphylococcus 23
Streptococcus 31
Chapter 3. Gram-positive bacilli 41
Introduction 41
Listeria 47
Chapter 4. Mycobacterial infection 55
Introduction 55
Classification 55
Pathogenesis 55
Clinical importance 56
Laboratory diagnosis 58
Identification techniques 63
Susceptibility testing 66
Chapter 5. Gram-negative cocci (the Neisseriaceae) 69
Classification 69
Classification and clinical importance 69
Neisseria 70
Chapter 6. Gram-negative coccobacilli 79
Introduction 79
Other rare Gram-negative coccobacilli 92
Chapter 7. Gram-negative bacilli 93
Introduction 93
Enterobacteriaceae 93
Chapter 8. Anaerobes 103
Introduction 103
Pathogenesis 104
Laboratory diagnosis 104
Generation of anaerobic atmosphere 107
Identification of anaerobic species 109
Gram-negative non-sporing anaerobes 112
Chapter 9. Spiral bacteria 119
Introduction 119
Borrelia 121
Spirillum minor 123
Chapter 10. Medical mycology 124
Introduction 124
Definitions 124
Classification 125
Opportunistic fungal infections 126
Systemic fungal infections 130
Superficial mycoses 131
Chapter 11. Parasitology 136
Introduction 136
Parasitic infections which present with fever 136
Intestinal parasites 146
Intestinal protozoa 147
Intestinal helminths 150
Chapter 12. The microbiology laboratory: organization and quality assurance 157
Microbiology staff 157
Accreditation 158
Medical audit 159
Laboratory controls 159
Chapter 13. Safety in the laboratory 162
Introduction 162
Control of substances hazardous to health (COSHH) 162
Developing a safety policy 163
Chapter 14. Collection of blood for culture 171
Introduction 171
Principles of blood culture 171
Laboratory examination of blood culture 174
Contamination of blood cultures 176
Concentration techniques 177
Removal of antibiotics in blood 177
Investigation of pyrexia of uncertain origin 177
Chapter 15. Examination of specimens from the central nervous system 182
Acute meningitis 182
Brain abscess 188
Chapter 16. Infections of the respiratory tract 190
Introduction 190
Classification of lower respiratory tract infections 190
Sputum 190
Nasopharyngeal aspiration 192
Lung puncture 193
Throat and nasal swabs 194
Mycoplasma and ureaplasma 195
Chlamydia causing respiratory infection 200
Chapter 17. Examination of faeces for bacterial pathogens 203
Introduction 203
Direct examination 204
Bacteriological culture 204
Chapter 18. Examination of urine and pus 222
Urine 222
Examination of pus 227
Skin 229
Diagnosis of ocular infection 231
Chapter 19. Investigation of specimens from the genital tract and diagnosis of sexually transmitted diseases (STDs) 233
Syphilis 233
Genital mycoplasmas 240
Donovanosis or granuloma inguinale 240
Chancroid 240
Vaginal discharge 241
Chapter 20. Antimicrobial susceptibility 245
Introduction 245
Media 246
Disc diffusion tests 247
Breakpoints 251
Minimal inhibitory and bactericidal concentrations 253
Tests for synergy 255
Antibiotic assays 256
Serum bactericidal levels 258
Beta-lactamase testing 258
Chapter 21. Serological techniques 259
Introduction 259
Antigen–antibody interactions 259
Some indications for serological investigation 261
Precipitation and agglutination techniques 262
Immunofluorescence techniques 266
Radioimmunoassay (RIA) 268
Enzyme-linked immunosorbent assay (ELISA) 268
Detection levels of various techniques 273
Significance of positive results 273
Chapter 22. Bacteriological examination of water, food and air 274
Water 274
Milk 277
Food 278
Air 278
Further reading 281
Index 286

Textauszug

2

Gram-positive cocci

Publisher Summary

Gram-positive cocci are included among some of the most significant human bacterial pathogens: primary pathogens such as Staphylococcus aureus, Streptococcus pyogenes, and Strep. pneumoniae, along with species of lower virulence such as Staph. epidermidis, Staph. Saprophyticus, and Enterococcus faecalis. The isolation and identification of these organisms is one of the most important but also routine tasks performed in clinical microbiology. The Gram-positive cocci are divided into the Streptococcaceae and the Micrococcaceae. This is an important clinical as well as taxonomic division and one that is made simply on the basis of colonial morphology, Gram morphology, and the catalase test. This chapter discusses the biology of two gram-positive cocci, that is, Staphylococcus and Streptococcus. The genus Staphylococcus belongs to the family Micrococcaceae. Staphylococci are Gram positive and occur characteristically in irregular grape-like clusters, tetrads, or short chains. They are catalase-positive, facultative anaerobes, nonmotile, non-spore-forming, and usually unencapsulated. The family Streptococcaceae include Gram-positive spherical bacteria growing in chains or pairs. They are typically nonmotile, non-spore forming facultative anaerobes, and oxidase negative. They attack carbohydrates fermentatively and are catalase negative. The Streptococcaceae are distinguished from the Micrococcaceae in that the former are catalase negative and the latter are catalase positive.

Introduction

Gram-positive cocci are included among some of the most significant human bacterial pathogens: primary pathogens such as Staphylococcus aureus, Streptococcus pyogenes, and Strep. pneumoniae, along with species of lower virulence such as Staph. epidermidis, Staph. saprophyticus and Enterococcus faecalis. Isolation and identification of these organisms is one of the most important but also routine tasks performed in clinical microbiology.

The Gram-positive cocci are divided into the Streptococcaceae and the Micrococcaceae; this is summarized in Table 2.1. This is an important clinical as well as taxonomic division and one which is made simply on the basis of colonial morphology, Gram morphology and the catalase test (Figs 2.1–2.3).

Table 2.1

Differentiation of Gram-positive cocci

Micrococcaceae

Micrococcus spp.

O

+

Clusters

Staphylococcus

F

+

Clusters

Streptococcaceae

Aerococcus

F

weak

Clusters

Streptococcus

F

–

Chains

Enterococcus

F

–

Chains

O/F: Oxidative/Fermentative

Figure 2.1 (a) The Gram stain shows the characteristic ‘bunch of grapes’ appearance which gave staphylococci their name. (b) Coagulase-negative staphylococci like this strain of S. epidermidis may be seen in tetrads. They cannot be distinguished from S. aureus on this characteristic alone

Figure 2.2 (a) Streptococci form long chains of cocci as in this preparation of S. pyogenes. (b) Enterococci and some other species of streptococci may apparently cluster and form short chains

Figure 2.3 (a and b) The catalyse test is an important test for differentiating streptococci from staphylococci. Hydrogen peroxide drawn into a capillary tube is touched onto a colony: catalase-positive strains will be demonstrated by a column of bubbles rising in the tube. Alternatively a colony can be picked up with a wooden applicator and placed into a bijoux of hydrogen peroxide

Staphylococcus

Introduction

The genus Staphylococcus belongs to the family Micrococcaceae (see Table 2.1). (The other major genus in the family, Micrococcus, is found as a commensal in human specimens and in the environment. It rarely causes disease.) Staphylococci are Gram positive and occur characteristically in irregular grape-like clusters, tetrads or short chains. They are catalase-positive, facultative anaerobes, non-motile, non-spore-forming and usually unencapsulated. They may be differentiated from micrococci by their susceptibility to lysostaphin, resistance to lysozyme, fermentative reaction in the Hugh and Leifson test and their ability to ferment glycerol in a medium containing 0.4 mg/1 erythromycin.

Habitat

Staphylococci are found on the skin and mucus membranes and in the gastrointestinal tract of humans, other mammals and birds. Some species have a preferred host, e.g. S. hyicus, pigs; S. caprae, goats; S. equorum, horses. Many are found on the human host as commensals, and can be found preferentially in some parts of the body (Table 2.2). Staphylococci survive well in the environment on skin squames and in dust and are readily transmitted in hospitals on the hands of medical and nursing staff and by the airborne route. Measures must, therefore, be taken to prevent the spread of strains of Staph. aureus that have enhanced virulence or which carry antibiotic resistance genes.

Table 2.2

Examples of staphylococci found in the human host with preferred site of colonization

Species

Site

S. aureus

Anterior nares

S. epidermidis

Skin

S. saprophyticus

Genitourinary tract

S. haemolyticus

Apocrine skin

S. hominis

Apocrine skin

S. capitis

Scalp

Clinical importance

Staphylococcus aureus is a common cause of primary human skin infections including impetigo, pustules, boils, carbuncles, and cellulitis. It is also frequently implicated in postoperative sepsis, in wound infections, abscesses, and in colonizing intravascular prosthetic devices and the sites of burns. Septicaemia may develop when organisms invade from any of these sites or can occur when introduced by intravenous catheters or by the unhygienic techniques employed by i.v. drug abusers. Serious localized infections may arise as a result of haematogenous spread from the site of a trivial skin infection or as part of the septicaemic process resulting in an acute endocarditis, osteomyelitis, or septic arthritis. Staphylococcal pneumonia may follow severe influenza virus infection or aspiration.

Staphylococcus aureus elaborates a number of potent toxins, including six enterotoxins which withstand heating at 100°C for 30 minutes. Foods typically implicated include ham, cream and custard. Symptoms of vomiting and diarrhoea develop after a short incubation period (4–6 hours) and are typically of short duration.

Strains which elaborate exfoliatin toxin are capable of inducing the staphylococcal scalded skin syndrome (Lyell’s syndrome) where the bacterial toxin causes lysis in the layers of the skin with widespread superficial skin loss. The patient appears to have multiple scalds.

Toxic shock syndrome (TSS) is a community-acquired toxaemia associated with the use of tampons or with skin sepsis where there is a localized S. aureus infection, with an organism which produces the toxic shock syndrome toxin-1 (TSST-1). This results in an acute life-threatening toxaemia characterized by hypotension, scarletiniform rash followed by desquamation, and multi-organ failure.

In the past staphylococci were classified on the basis of the coagulase test into S. aureus and ‘S. albus’, the latter usually being dismissed as a non-pathogen. ‘S. albus’ has now been subdivided into many species (at least 27), some of which are human pathogens.

As a result of changes in medical practice S. epidermidis infection is now considered to be an important clinical problem. S. epidermidis is a frequent cause of hospital-acquired bacteraemia (up to 75% of positive blood cultures) often related to indwelling intravascular prosthetic devices, including prosthetic heart valves, central venous cannulae and pacemakers. The organisms are usually introduced at the time of insertion. In these circumstances staphylococci may cause recurring episodes of bacteraemia necessitating the removal of the prosthetic device.

Staphylococcus epidermidis is responsible for approximately 40% of prosthetic joint infection and is involved in bacterial...

Produkt-Details

• Erscheint lt. Verlag: 28.6.2014
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber ► Gesundheit / Leben / Psychologie ► Krankheiten / Heilverfahren
• Themenwelt: Medizin / Pharmazie ► Allgemeines / Lexika
• Themenwelt: Naturwissenschaften ► Biologie ► Mikrobiologie / Immunologie
• Themenwelt: Technik
• ISBN-10: 1-4831-9363-2 / 1483193632
• ISBN-13: 978-1-4831-9363-2 / 9781483193632