Hospitals are primary transmission sites for CRE-based infections. Up to 75% of hospital admissions attributed to CRE were from long-term care facilities or transferred from another hospital. Suboptimal maintenance practices are the largest cause of CRE transmission. This includes the failure to adequately clean and disinfect medication cabinets, other surfaces in patient rooms, and portable medical equipment, such as X-ray and ultrasound machines that are used for both CRE and non-CRE patients.

Thus far, CRE have primarily been nosocomial infectious agents. Almost all CRE infections occur in people receiving significant medical care in hospitals, long-term acute care facilities, or nursing homes. Independent risk factors for CRE infection include use of beta-lactam antibiotics and the use of mechanical ventilation. Patients with diabetes have also been shown to be at an elevated risk for acquiring CRE infections. When compared to other hospitalized patients, those admitted from long-term acute care (LTAC) facilities have significantly higher incidence of colonization and infection rates. Another 2012 multicenter study found that over 30% of patients with recent exposure to LTAC were colonized or infected with CRE. A person susceptible to CRE transmission is more likely to be female, have a greater number of parenteral nutrition-days (meaning days by which the person received nutrition via the bloodstream), and to have had a significant number of days breathing through a ventilator.

Infections with carbapenem-resistant "Klebsiella pneumoniae" were associated with organ/stem cell transplantation, mechanical ventilation, exposure to antimicrobials, and overall longer length of stay in hospitals.

People most likely to acquire carbapenem-resistant bacteria are those already receiving medical attention. In a study carried out at Sheba medical center, there was a trend toward worse Charleson Comorbidity scores in patients who acquired CRKP during ICU stay. Those at highest risk are patients receiving an organ or stem cell implantation, use of mechanical ventilation, or have to have an extended stay in the hospital along with exposure to antimicrobials. In a study performed in Singapore, the acquisition of ertapenem-resistant Enterobacteriaceae to the acquisition of CRE. Exposure to antibiotics, especially fluoroquinolones, and previous hospitalization dramatically increased the risk of acquisition carbapenem-resistant bacteria. This study found that carbapenem-resistant acquisition has a significantly higher mortality rate and poorer clinical response compared to that of the ertapenem-resistance acquisition.

Bacteruria (also known as urinary tract infection) caused by CRKp and CSKp have similar risk factors. These include prior antibiotic use, admittance to an ICU, use of a permanent urinary catheter, and previous invasive procedures or operations. A retrospective study of patients with CRKp and CSKp infection asserted that the use of cephalosporins (a class of β-lactam antibiotics) used before invasive procedures was higher in patients with CRKp infection, suggesting that it is a risk factor.

In a three-year study, the prevalence of CRE was shown to be proportional to the lengths of stays of the patients in those hospitals. Policies regarding contact precaution for patients infected or colonized by Gram-negative pathogens were also observed in hospitals reporting decreases in CRE prevalence.

One case study showed that patients with a compromised immune response are especially susceptible to both CRE exposure and infection. In one study, an elderly patient with acute lymphoblastic leukemia being treated in a long-term care facility contracted a CRE infection. Her age and condition, combined with her environment and regulation by a catheter and mechanical ventilation, all contributed to a higher susceptibility. This highlights the importance of finding the source of the bacteria, as members of this class of patients are at continued risk for infection. Infection control and prevention of CRE should be the main focus in managing patients at high risk.

Another major risk factor is being in a country with unregulated antibiotic distribution. In countries where antibiotics are over-the counter and obtainable without a prescription, the incidence and prevalence of CRE infections were higher. One study from Japan found that 6.4% of healthy adults carried ESBL (mostly cefotaximase)-producing strains compared to 58.4% in Thailand, where antibiotics are available over the counter and without prescription. An Egyptian research group found that 63.3% of healthy adults were colonized.

In February 2015, the FDA reported about a transmission risk when people undergo a gastroenterology procedure called endoscopic retrograde cholangiopancreatography, where an endoscope enters the mouth, passes the stomach, and ends in the duodenum; if incompletely disinfected, the device can transmit CRE from one patient to another. The FDA's safety communication came a day after the UCLA Health System, Los Angeles, notified more than 100 patients that they may have been infected with CRE during endoscopies between October 2014 and January 2015. The FDA had issued its first notice about the devices in 2009.

Bacteria with resistance to antibiotics predate medical use of antibiotics by humans. However, widespread antibiotic use has made more bacteria resistant through the process of evolutionary pressure.

Reasons for the widespread use of antibiotics in human medicine include:

- increasing global availability over time since the 1950s

- uncontrolled sale in many low or middle income countries, where they can be obtained over the counter without a prescription, potentially resulting in antibiotics being used when not indicated. This may result in emergence of resistance in any remaining bacteria.

Other causes include:

- Antibiotic use in livestock feed at low doses for growth promotion is an accepted practice in many industrialized countries and is known to lead to increased levels of resistance.

- Releasing large quantities of antibiotics into the environment during pharmaceutical manufacturing through inadequate wastewater treatment increases the risk that antibiotic-resistant strains will develop and spread.

- It is uncertain whether antibacterials in soaps and other products contribute to antibiotic resistance, but antibacterial soaps are discouraged for other reasons.

A World Health Organization (WHO) report released April 2014 stated, "this serious threat is no longer a prediction for the future, it is happening right now in every region of the world and has the potential to affect anyone, of any age, in any country. Antibiotic resistance—when bacteria change so antibiotics no longer work in people who need them to treat infections—is now a major threat to public health."

Studies have found that men have a higher risk of getting XDR-TB than women. One study showed that the male to female ratio was more than threefold, with statistical relevance (P<0.05) Studies done on the effect of age and XDR-TB have revealed that individuals who are 65 and up are less likely to get XDR-TB. A study in Japan found that XDR-TB patients are more likely to be younger.

CRE resistance depends upon a number of factors such as the health of the patient, whether the patient has recently undergone a transplant, risk of co-infection, and use of multiple antibiotics.

Carbapenem minimal inhibitory concentrations (MICs) results may be more predictive of clinical patient outcomes than the current categorical classification of the MICs being listed as susceptible, intermediate, or resistant. The study aimed to define an all-cause hospital mortality breakpoint for carbapenem MICs that were adjusted for risk factors. Another objective was to determine if a similar breakpoint existed for indirect outcomes, such as the time to death and length of stay after infection for survivors. Seventy-one patients were included, of which 52 patients survived and 19 patients died. Classification and regression tree analysis determined a split of organism MIC between 2 and 4 mg/liter and predicted differences in mortality (16.1% for 2 mg/liter versus 76.9% for 4 mg/liter). In logistic regression controlling for confounders, each imipenem MIC doubling dilution doubled the probability of death. This classification scheme correctly predicted 82.6% of cases. Patients were accordingly stratified to MICs of ≤2 mg/liter (58 patients) and ≥4 mg/liter (13 patients). Patients in the group with a MIC of ≥4 mg/liter tended to be more ill. Secondary outcomes were also similar between groups. Patients with organisms that had an MIC of ≥4 mg/liter had worse outcomes than those with isolates of an MIC of ≤2 mg/liter.

At New York Presbyterian Hospital, part of Columbia University Medical Center in New York, NY, a study was conducted on the significant rise in carbapenem resistance in "K. pneumoniae" from 1999 to 2007. Following a positive blood culture from a patient, overall mortality was 23% in 7 days, 42% in 30 days, and 60% by the end of hospitalization. The overall in-hospital mortality rate was 48%.

At Soroka Medical Center, an Israeli university teaching hospital, a study was done between October 2005 and October 2008 to determine the direct mortality rate associated with carbapenem-resistant "K. pneumoniae" bloodstream infections. The crude mortality rate for those with the resistant bacteremia was 71.9%, and the attributable mortality rate was determined to be 50% with a 95% confidence interval. The crude mortality rate for control subjects was 21.9%. As a result of the study, Soroka Medical Center started an intensive program designed to prevent the spread of carbapenem-resistant "K. pneumoniae."

A 2013 retrospective study at the Shaare Zedek Medical Center of patients with urinary tract infections (bacteriuria) caused by carbapenem-resistant "Klebsiella pneumoniae" (CRKp) showed no statistically significant difference in mortality rates from patients with bacteriuria caused by carbapenem-susceptible "K. pneumoniae" (CSKp). A 29% mortality rate was seen in patients with CRKp infection compared to a 25% mortality rate in patients with CSKp infections that produced extended-spectrum beta-lactamase (ESBL). Both mortality rates were considerably higher than that of patients with drug-susceptible urosepsis. Most patients in the study suffered from other illnesses, including dementia, immune compromise, renal failure, or diabetes mellitus. The main risk factor for death found by the study was being bedridden, which significantly increased the chance of death. This suggests that the deaths were due to reasons other than bacteriuria. Total length of hospitalization was somewhat longer in patients with CRKp infections (28 ± 33 days compared to 22 ± 28 days for patients with CSKp infection).

In a case-control study of 99 patients compared with 99 controls at Mount Sinai Hospital (Manhattan), a 1,171 bed tertiary care teaching hospital, 38% of patients in long-term care that were afflicted with CRE died from "K. pneumoniae" infection. Patients had risk factors including diabetes, HIV infection, heart disease, liver disease, renal insufficiency, one was a transplant recipient. 72% of patients who were released from the hospital with CRE were readmitted within 90 days.

A 2008 study at Mount Sinai identified outcomes associated with Carbapenem-resistant "Klebsiella pneumoniae" infections, in which patients in need of organ or stem cell transplants, mechanical ventilation, prolonged hospitalization, or prior treatment with carbapenems, had an increased probability of infection with Carbapenem-resistant "K. pneumoniae". A combination of antibiotics worked to treat infection and survival rates of infected patients increased when the focus of infection was removed.

CRE infections can set in about 12 days after liver transplantation, and 18% of those patients died a year after transplantation in a 2012 study.

Carriers who refuse to wear a mask in public have been indefinitely involuntarily committed to regular jails, and cut off from contacting the world. Some have run away from the USA, complaining of abuse.

Common multidrug-resistant organisms are usually bacteria:

- Vancomycin-Resistant Enterococci (VRE)

- Methicillin-Resistant "Staphylococcus" "aureus" (MRSA)

- Extended-spectrum β-lactamase (ESBLs) producing Gram-negative bacteria

- "Klebsiella" "pneumoniae" carbapenemase (KPC) producing Gram-negatives

- Multidrug-Resistant gram negative rods (MDR GNR) MDRGN bacteria such as "Enterobacter species", "E.coli", "Klebsiella pneumoniae", "Acinetobacter baumannii", "Pseudomonas aeruginosa"

A group of gram-positive and gram-negative bacteria of particular recent importance have been dubbed as the ESKAPE group ("Enterococcus faecium", "Staphylococcus aureus", "Klebsiella pneumoniae", "Acinetobacter baumannii", "Pseudomonas aeruginosa" and Enterobacter species).

- Multi-drug-resistant tuberculosis

Cases of MDR tuberculosis have been reported in every country surveyed. MDR-TB most commonly develops in the course of TB treatment, and is most commonly due to doctors giving inappropriate treatment, or patients missing doses or failing to complete their treatment. Because MDR tuberculosis is an airborne pathogen, persons with active, pulmonary tuberculosis caused by a multidrug-resistant strain can transmit the disease if they are alive and coughing. TB strains are often less fit and less transmissible, and outbreaks occur more readily in people with weakened immune systems (e.g., patients with HIV). Outbreaks among non immunocompromised healthy people do occur, but are less common.

As of 2013, 3.7% of new tuberculosis cases have MDR-TB. Levels are much higher in those previously treated for tuberculosis - about 20%. WHO estimates that there were about 0.5 million new MDR-TB cases in the world in 2011. About 60% of these cases occurred in Brazil, China, India, the Russian Federation and South Africa alone. In Moldova, the crumbling health system has led to the rise of MDR-TB. In 2013, the Mexico–United States border was noted to be "a very hot region for drug resistant TB", though the number of cases remained small.

It has been known for many years that INH-resistant TB is less virulent in guinea pigs, and the epidemiological evidence is that MDR strains of TB do not dominate naturally. A study in Los Angeles, California found that only 6% of cases of MDR-TB were clustered. Likewise, the appearance of high rates of MDR-TB in New York City in the early 1990s was associated with the explosion of AIDS in that area. In New York City, a report issued by city health authorities states that fully 80 percent of all MDR-TB cases could be traced back to prisons and homeless shelters. When patients have MDR-TB, they require longer periods of treatment—about two years of multidrug regimen. Several of the less powerful second-line drugs, which are required to treat MDR-TB, are also more toxic, with side effects such as nausea, abdominal pain, and even psychosis. The Partners in Health team had treated patients in Peru who were sick with strains that were resistant to ten and even twelve drugs. Most such patients require adjuvant surgery for any hope of a cure.

The prime example for MDR against antiparasitic drugs is malaria. "Plasmodium vivax" has become chloroquine and sulfadoxine-pyrimethamine resistant a few decades ago, and as of 2012 artemisinin-resistant Plasmodium falciparum has emerged in western Cambodia and western Thailand.

"Toxoplasma gondii" can also become resistant to artemisinin, as well as atovaquone and sulfadiazine, but is not usually MDR

Antihelminthic resistance is mainly reported in the veterinary literature, for example in connection with the practice of livestock drenching and has been recent focus of FDA regulation.

There are several ways that drug resistance to TB, and drug resistance in general, can be prevented:

1. Rapid diagnosis & treatment of TB: One of the greatest risk factors for drug resistant TB is problems in treatment and diagnosis, especially in developing countries. If TB is identified and treated soon, drug resistance can be avoided.

2. Completion of treatment: Previous treatment of TB is an indicator of MDR TB. If the patient does not complete his/her antibiotic treatment, or if the physician does not prescribe the proper antibiotic regimen, resistance can develop. Also, drugs that are of poor quality or less in quantity, especially in developing countries, contribute to MDR TB.

3. Patients with HIV/AIDS should be identified and diagnosed as soon as possible. They lack the immunity to fight the TB infection and are at great risk of developing drug resistance.

4. Identify contacts who could have contracted TB: i.e. family members, people in close contact, etc.

5. Research: Much research and funding is needed in the diagnosis, prevention and treatment of TB and MDR TB.

"Opponents of a universal tuberculosis treatment, reasoning from misguided notions of cost-effectiveness, fail to acknowledge that MDRTB is not a disease of poor people in distant places. The disease is infectious and airborne. Treating only one group of patients looks inexpensive in the short run, but will prove disastrous for all in the long run."- Paul Farmer

Totally drug-resistant tuberculosis (TDR-TB) is a generic term for tuberculosis strains that are resistant to a wider range of drugs than strains classified as extensively drug-resistant tuberculosis. TDR-TB has been identified in three countries; India, Iran, and Italy. The emergence of TDR-TB has been documented in four major publications. However, it is not yet recognised by the World Health Organization.

TDR-TB has resulted from further mutations within the bacterial genome to confer resistance, beyond those seen in XDR- and MDR-TB. Development of resistance is associated with poor management of cases. Drug resistance testing occurs in only 9% of TB cases worldwide. Without testing to determine drug resistance profiles, MDR- or XDR-TB patients may develop resistance to additional drugs. TDR-TB is relatively poorly documented, as many countries do not test patient samples against a broad enough range of drugs to diagnose such a comprehensive array of resistance. The United Nations' Special Programme for Research and Training in Tropical Diseases has set up a TDR Tuberculosis Specimen Bank to archive specimens of TDR-TB.

HCAP is a condition in patients who can come from the community, but have frequent contact with the healthcare environment. Historically, the etiology and prognosis of nursing home pneumonia appeared to differ from other types of community acquired pneumonia, with studies reporting a worse prognosis and higher incidence of multi drug resistant organisms as etiology agents. The definition criteria which has been used is the same as the one which has been previously used to identify bloodstream healthcare associated infections.

HCAP is no longer recognized as a clinically independent entity. This is due to increasing evidence from a growing number of studies that many patients defined as having HCAP are not at high risk for MDR pathogens. As a result, 2016 IDSA guidelines removed consideration of HCAP as a separate clinical entity.

Healthcare-associated pneumonia can be defined as pneumonia in a patient with at least one of the following risk factors:

- hospitalization in an acute care hospital for two or more days in the last 90 days;

- residence in a nursing home or long-term care facility in the last 30 days

- receiving outpatient intravenous therapy (like antibiotics or chemotherapy) within the past 30 days

- receiving home wound care within the past 30 days

- attending a hospital clinic or dialysis center in the last 30 days

- having a family member with known multi-drug resistant pathogens

VAP occurring early after intubation typically involves fewer resistant organisms and is thus associated with a more favorable outcome. Because respiratory failure requiring mechanical ventilation is itself associated with a high mortality, determination of the exact contribution of VAP to mortality has been difficult. As of 2006, estimates range from 33% to 50% death in patients who develop VAP. Mortality is more likely when VAP is associated with certain microorganisms ("Pseudomonas", "Acinetobacter"), blood stream infections, and ineffective initial antibiotics. VAP is especially common in people who have acute respiratory distress syndrome (ARDS).

Progression from TB infection to overt TB disease occurs when the bacilli overcome the immune system defenses and begin to multiply. In primary TB disease (some 1–5% of cases), this occurs soon after the initial infection. However, in the majority of cases, a latent infection occurs with no obvious symptoms. These dormant bacilli produce active tuberculosis in 5–10% of these latent cases, often many years after infection.

The risk of reactivation increases with immunosuppression, such as that caused by infection with HIV. In people coinfected with "M. tuberculosis" and HIV, the risk of reactivation increases to 10% per year. Studies using DNA fingerprinting of "M. tuberculosis" strains have shown reinfection contributes more substantially to recurrent TB than previously thought, with estimates that it might account for more than 50% of reactivated cases in areas where TB is common. The chance of death from a case of tuberculosis is about 4% as of 2008, down from 8% in 1995.

A number of factors make people more susceptible to TB infections. The most important risk factor globally is HIV; 13% of all people with TB are infected by the virus. This is a particular problem in sub-Saharan Africa, where rates of HIV are high. Of people without HIV who are infected with tuberculosis, about 5–10% develop active disease during their lifetimes; in contrast, 30% of those coinfected with HIV develop the active disease.

Tuberculosis is closely linked to both overcrowding and malnutrition, making it one of the principal diseases of poverty. Those at high risk thus include: people who inject illicit drugs, inhabitants and employees of locales where vulnerable people gather (e.g. prisons and homeless shelters), medically underprivileged and resource-poor communities, high-risk ethnic minorities, children in close contact with high-risk category patients, and health-care providers serving these patients.

Chronic lung disease is another significant risk factor. Silicosis increases the risk about 30-fold. Those who smoke cigarettes have nearly twice the risk of TB compared to nonsmokers.

Other disease states can also increase the risk of developing tuberculosis. These include alcoholism and diabetes mellitus (three-fold increase).

Certain medications, such as corticosteroids and infliximab (an anti-αTNF monoclonal antibody), are becoming increasingly important risk factors, especially in the developed world.

Genetic susceptibility also exists, for which the overall importance remains undefined.

Between 8 and 28% of patients receiving mechanical ventilation are affected by VAP. VAP can develop at any time during ventilation, but occurs most often in the first week of mechanical ventilation. There is some evidence for gender differences in the course of VAP: men have been found to get VAP more often, but women are more likely to die after contracting VAP.

The U.S. Centers for Disease Control and Prevention (CDC) publishes a journal "Emerging Infectious Diseases" that identifies the following factors contributing to disease emergence:

- Microbial adaption; e.g. genetic drift and genetic shift in Influenza A

- Changing human susceptibility; e.g. mass immunocompromisation with HIV/AIDS

- Climate and weather; e.g. diseases with zoonotic vectors such as West Nile Disease (transmitted by mosquitoes) are moving further from the tropics as the climate warms

- Change in human demographics and trade; e.g. rapid travel enabled SARS to rapidly propagate around the globe

- Economic development; e.g. use of antibiotics to increase meat yield of farmed cows leads to antibiotic resistance

- Breakdown of public health; e.g. the current situation in Zimbabwe

- Poverty and social inequality; e.g. tuberculosis is primarily a problem in low-income areas

- War and famine

- Bioterrorism; e.g. 2001 Anthrax attacks

- Dam and irrigation system construction; e.g. malaria and other mosquito borne diseases

Methicillin-resistant Staphylococcus aureus (MRSA) evolved from Methicillin-susceptible Staphylococcus aureus (MSSA) otherwise known as common "S. aureus". Many people are natural carriers of "S. aureus", without being affected in any way. MSSA was treatable with the antibiotic methicillin until it acquired the gene for antibiotic resistance. Though genetic mapping of various strains of MRSA, scientists have found that MSSA acquired the mecA gene in the 1960s, which accounts for its pathogenicity, before this it had a predominantly commensal relationship with humans. It is theorized that when this "S. aureus" strain that had acquired the mecA gene was introduced into hospitals, it came into contact with other hospital bacteria that had already been exposed to high levels of antibiotics. When exposed to such high levels of antibiotics, the hospital bacteria suddenly found themselves in an environment that had a high level of selection for antibiotic resistance, and thus resistance to multiple antibiotics formed within these hospital populations. When "S. aureus" came into contact with these populations, the multiple genes that code for antibiotic resistance to different drugs were then acquired by MRSA, making it nearly impossible to control. It is thought that MSSA acquired the resistance gene through the horizontal gene transfer, a method in which genetic information can be passed within a generation, and spread rapidly through its own population as was illustrated in multiple studies. Horizontal gene transfer speeds the process of genetic transfer since there is no need to wait an entire generation time for gene to be passed on. Since most antibiotics do not work on MRSA, physicians have to turn to alternative methods based in Darwinian medicine. However prevention is the most preferred method of avoiding antibiotic resistance. By reducing unnecessary antibiotic use in human and animal populations, antibiotics resistance can be slowed.

The most commonly known pathogen is "Candida albicans", causing roughly 70% of fungemias, followed by "Candida glabrata" with 10%, "Aspergillus" with 1% and "Saccharomyces" as the fourth most common. However, the frequency of infection by "C. glabrata", "Saccharomyces boulardii", "Candida tropicalis", "C. krusei" and "C. parapsilosis" is increasing, perhaps because significant use of fluconazole is common or due to increase in antibiotic use.

New emerging pathogen: "Candida auris" is an emerging multidrug-resistant (MDR) yeast that can cause invasive infections and is associated with high mortality. It was first described in 2009 after being isolated from external ear discharge of a patient in Japan. Since the 2009 report, C. auris infections, specifically fungemia, have been reported from South Korea, India, South Africa, and Kuwait. Although published reports are not available, C. auris has also been identified in Colombia, Venezuela, Pakistan, and the United Kingdom.

Fungemia or fungaemia is the presence of fungi or yeasts in the blood. The most common type, also known as candidemia, candedemia, or systemic candidiasis, is caused by "Candida" species, but infections by other fungi, including "Saccharomyces", "Aspergillus" and "Cryptococcus", are also called fungemia. It is most commonly seen in immunosuppressed or immunocompromised patients with severe neutropenia, cancer patients, or in patients with intravenous catheters. It has been suggested the otherwise immunocompetent patients taking infliximab may be at a higher risk for fungemia.

Diagnosis is difficult, as routine blood cultures have poor sensitivity.

Antineoplastic resistance, synonymous with chemotherapy resistance, is the ability of cancer cells to survive and grow despite different anti-cancer therapies, i.e. their multiple drug resistance. There are two general causes of antineoplastic therapy failure:

Inherent resistance, such as genetic characteristics, giving cancer cells their resistance from the beginning, which is rooted in the concept of cancer cell heterogeneity and acquired resistance after drug exposure.

As resistance to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, and streptomycin is now common, these agents have not been used as first–line treatment of typhoid fever for almost 20 years. Typhoid resistant to these agents is known as multidrug-resistant typhoid (MDR typhoid).

Ciprofloxacin resistance is an increasing problem, especially in the Indian subcontinent and Southeast Asia. Many centres are shifting from using ciprofloxacin as the first line for treating suspected typhoid originating in South America, India, Pakistan, Bangladesh, Thailand, or Vietnam. For these people, the recommended first-line treatment is ceftriaxone. Also, azithromycin has been suggested to be better at treating typhoid in resistant populations than both fluoroquinolone drugs and ceftriaxone. Azithromycin significantly reduces relapse rates compared with ceftriaxone.

A separate problem exists with laboratory testing for reduced susceptibility to ciprofloxacin: current recommendations are that isolates should be tested simultaneously against ciprofloxacin (CIP) and against nalidixic acid (NAL), and that isolates that are sensitive to both CIP and NAL should be reported as "sensitive to ciprofloxacin", but that isolates testing sensitive to CIP but not to NAL should be reported as "reduced sensitivity to ciprofloxacin". However, an analysis of 271 isolates showed that around 18% of isolates with a reduced susceptibility to ciprofloxacin (MIC 0.125–1.0 mg/l) would not be picked up by this method. How this problem can be solved is not certain, because most laboratories around the world (including the West) are dependent on disk testing and cannot test for MICs.

The bacterium that causes typhoid fever may be spread through poor hygiene habits and public sanitation conditions, and sometimes also by flying insects feeding on feces. Public education campaigns encouraging people to wash their hands after defecating and before handling food are an important component in controlling spread of the disease. According to statistics from the United States Centers for Disease Control and Prevention (CDC), the chlorination of drinking water has led to dramatic decreases in the transmission of typhoid fever in the United States.

Antineoplastic resistance, often used interchangeably with chemotherapy resistance, is the multiple drug resistance of neoplastic (cancerous) cells, or the ability of cancer cells to survive and grow despite anti-cancer therapies.

There are two general causes of antineoplastic therapy failure: Inherent genetic characteristics, giving cancer cells their resistance, which is rooted in the concept of cancer cell heterogeneity and acquired resistance after drug exposure. Altered membrane transport, enhanced DNA repair, apoptotic pathway defects, alteration of target molecules, protein and pathway mechanisms, such as enzymatic deactivation.

Since cancer is a genetic disease, two genomic events underlie acquired drug resistance: Genome alterations (e.g. gene amplification and deletion) and epigenetic modifications.

Cancer cells are constantly using a variety of tools, involving genes, proteins and altered pathways, to ensure their survival against antineoplastic drugs.